Impacts of COVID on the immune system

Authors: Lara Herrero, The Conversation Medical Xpress September 19, 2022

So you’ve had COVID and have now recovered. You don’t have ongoing symptoms and luckily, you don’t seem to have developed long COVID.

But what impacts has COVID had on your overall immune system?

It’s early days yet. But growing evidence suggests there are changes to your immune system that may put you at risk of other infectious diseases.

Here’s what we know so far.

A round of viral infections

Over this past winter, many of us have had what seemed like a continual round of viral illness. This may have included COVID, influenza or infection with respiratory syncytial virus. We may have recovered from one infection, only to get another.

Then there is the re-emergence of infectious diseases globally such as monkeypox or polio.

Could these all be connected? Does COVID somehow weaken the immune system to make us more prone to other infectious diseases?

There are many reasons for infectious diseases to emerge in new locations, after many decades, or in new populations. So we cannot jump to the conclusion COVID infections have given rise to these and other viral infections.

But evidence is building of the negative impact of COVID on a healthy individual’s immune system, several weeks after symptoms have subsided.

What happens when you catch a virus?

There are three possible outcomes after a viral infection:

  1. your immune system clears the infection and you recover (for instance, with rhinovirus which causes the common cold)
  2. your immune system fights the virus into “latency” and you recover with a virus dormant in our bodies (for instance, varicella zoster virus, which causes chickenpox)
  3. your immune system fights, and despite best efforts the virus remains “chronic,” replicating at very low levels (this can occur for hepatitis C virus).

Ideally we all want option 1, to clear the virus. In fact, most of us clear SARS-CoV-2, the virus that causes COVID. That’s through a complex process, using many different parts of our immune system.

But international evidence suggests changes to our immune cells after SARS-CoV-2 infection may have other impacts. It may affect our ability to fight other viruses, as well as other pathogens, such as bacteria or fungi.

How much do we know?

An Australian study has found SARS-CoV-2 alters the balance of immune cells up to 24 weeks after clearing the infection.

There were changes to the relative numbers and types of immune cells between people who had recovered from COVID compared with healthy people who had not been infected.

This included changes to cells of the innate immune system (which provides a non-specific immune response) and the adaptive immune system (a specific immune response, targeting a recognised foreign invader).

Another study focused specifically on dendritic cells—the immune cells that are often considered the body’s “first line of defence.”

Researchers found fewer of these cells circulating after people recovered from COVID. The ones that remained were less able to activate white blood cells known as T-cells, a critical step in activating anti-viral immunity.

Other studies have found different impacts on T-cells, and other types of white blood cells known as B-cells (cells involved in producing antibodies).

After SARS-CoV-2 infection, one study found evidence many of these cells had been activated and “exhausted.” This suggests the cells are dysfunctional, and might not be able to adequately fight a subsequent infection. In other words, sustained activation of these immune cells after a SARS-CoV-2 infection may have an impact on other inflammatory diseases.

One study found people who had recovered from COVID have changes in different types of B-cells. This included changes in the cells’ metabolism, which may impact how these cells function. Given B-cells are critical for producing antibodies, we’re not quite sure of the precise implications.

Could this influence how our bodies produce antibodies against SARS-CoV-2 should we encounter it again? Or could this impact our ability to produce antibodies against pathogens more broadly—against other viruses, bacteria or fungi? The study did not say.

What impact will these changes have?

One of the main concerns is whether such changes may impact how the immune system responds to other infections, or whether these changes might worsen or cause other chronic conditions.

So more work needs to be done to understand the long-term impact of SARS-CoV-2 infection on a person’s immune system.

For instance, we still don’t know how long these changes to the immune system last, and if the immune system recovers. We also don’t know if SARS-CoV-2 triggers other chronic illnesses, such as chronic fatigue syndrome (myalgic encephalomyelitis). Research into this is ongoing.

What we do know is that having a healthy immune system and being vaccinated (when a vaccine has been developed) is critically important to have the best chance of fighting any infection.

Bone Marrow Suppression Secondary to the COVID-19 Booster Vaccine: A Case Report

TAuthors: oral Shastri 1Navkiran Randhawa 2Ragia Aly 3Masood Ghouse 3 PMID: 35210894PMCID: PMC8863340DOI: 10.2147/JBM.S350290 J Blood Med.  2022; 13: 69–74.Published online 2022 Feb 18. doi: 10.2147/JBM.S350290

Abstract

As of September 2021, SARS-CoV-2 booster shots became widely available in the US to ensure continued protection against the virus. A temporal relationship has been previously reported between the first or second dose of the COVID-19 vaccine and the development of thrombocytopenia. However, adverse events related to the third COVID-19 vaccine are still being reported and studied. We report a 74-year-old male who developed bone marrow suppression and pancytopenia recorded seven days after receiving the Pfizer SARS-CoV-2 vaccine. During his hospital stay, the patient’s hemoglobin, white blood cell, and platelet levels continued to trend downwards. However, all three levels showed improvement one week after discharge without robust intervention. Global vaccination is of utmost importance, as is understanding and documenting post-vaccination reactions including bone marrow suppression. Prompt evaluation and patient education are imperative to improve patient outcomes and combat hesitancy against vaccine administration.

Introduction

Since its emergence in December of 2019, the rapid spread of severe acute respiratory syndrome coronavirus (SARS-CoV-2) has quickly affected millions of lives across every continent.1 This highly transmittable and pathogenic viral infection has led to massive mitigation efforts and allocation of resources to prevent the spread of transmission and high mortality related to complications.2 The establishment of higher levels of community (herd) immunity and protection against SARS-CoV-2 via the widespread deployment of effective vaccines has become a global effort.3 In December of 2020, the FDA issued an Emergency use Authorization for the Pfizer-BioNTech and Moderna COVID-19 Vaccine as a two-dose series.4 In September 2021, booster vaccines became widely administered in the US due to waning immunity of the COVID-19 vaccines against variants of SARS-CoV-2 along with ensuring continued protection against the virus.5

Serious adverse events such as anaphylaxis, Guillain-Barre Syndrome, myocarditis, pericarditis, thrombocytopenia, and death have been previously reported following the first and/or second dose of vaccine.6 To our knowledge, no cases have been reported regarding bone marrow suppression related to the third COVID-19 vaccine. Adverse events reported between August 12-September 19, 2021 from the COVID-19 booster vaccine supported similar reactions to those after dose two.7 According to the Centers for Disease Control and Prevention (CDC), these initial findings indicate no unexpected patterns of adverse reactions after an additional dose of COVID-19 vaccination.7 However, adverse events related to the COVID-19 booster are still being reported and studied.6 This report presents a case of bone marrow suppression occurring after the third COVID-19 vaccine without a similar reaction after the first or second dose.Go to:

Case Report

A 74-year-old male with a history of polychondritis and hypothyroidism presented to the hospital after falling out of his chair and inability to ambulate. The patient was found to be mildly confused upon arrival to the emergency room, limiting our ability to obtain a full verbal history. Chart review revealed the patient had received his third Pfizer Covid vaccine shot seven days before admission followed by fatigue, decreased appetite, fever, and chills. The patient had received the second Pfizer Covid-19 shot nine months before the booster. No reactions to the previous two shots were noted.

Upon initial evaluation, vital signs were within normal limits and a physical exam revealed significant tenderness in the upper arm and no gross bleeding (Figure 1). Computed tomography (CT) imaging (Figure 2) was significant for enhancement of the left axillary lymph node. The patient’s initial complete blood count (CBC) was remarkable for a hemoglobin count of 9.9 g/dl and platelet count of 84 x 109/L; both values lower than his prior hemoglobin count of 13.7 g/dl and platelet count of 180 x 109/L from December of 2020. His mean corpuscular volume (MCV) was elevated at 101.3 femtolitres from his prior MCV value of 95.8 femtolitres in December of 2020. His white blood cell (WBC) count was recorded at 7.6 x 109/L.

An external file that holds a picture, illustration, etc.
Object name is JBM-13-69-g0001.jpg

Figure 1

The patient’s upper arm showed erythema with no gross bleeding near the injection site

An external file that holds a picture, illustration, etc.
Object name is JBM-13-69-g0002.jpg

Figure 2

The patient’s CT imaging of the thoracic region showed enhancement of the left axillary lymph node.

The hemoglobin, WBC, and platelet count further down trended from his baseline (Figures 3​5).5). Anemia labs including ferritin levels (554 ng/mL), vitamin B12 (253 pg/mL), total bilirubin (0.5 mg/dL), and reticulocyte count (0.8%) were nonsignificant during the patient’s hospital stay. The patient’s left shoulder presented with extensive bruising, erythema, papular rash, warmth, and tenderness on palpation during the hospitalization. An improvement in WBC and platelet levels was noted on day 4 of hospitalization.

An external file that holds a picture, illustration, etc.
Object name is JBM-13-69-g0003.jpg

Figure 3

The patient’s hemoglobin count throughout his hospital course and 6 days after discharge.

An external file that holds a picture, illustration, etc.
Object name is JBM-13-69-g0004.jpg

Figure 4

The patient’s WBC count throughout his hospital course and 6 days after discharge.

An external file that holds a picture, illustration, etc.
Object name is JBM-13-69-g0005.jpg

Figure 5

The patient’s platelet count throughout his hospital course and 6 days after discharge.

Before discharge, the patient was fully alert and oriented and reported improvement in his symptoms. Examination of his lateral left arm showed decreased erythema and bruising with slight petechiae. The patient was discharged due to stabilization of labs and encouraged to take oral vitamin B12 supplements. During his outpatient follow-up six days after hospitalization, his hemoglobin increased to 10.5 g/dl, WBC count increased to 4.9 x 109/L, and platelets increased to 101 x 109/L.

Discussion

This paper presents a patient with pancytopenia recorded seven days after receiving the Pfizer booster vaccine. Interestingly, this patient did not report any reactions after the first or second dose of the Pfizer vaccine against SARS-CoV-2. Pancytopenia refers to a decrease in all peripheral bloodlines and is present when all three cell lines are below the normal reference range.8 The patient’s physical exam showed no signs of active bleeding along with his labs indicating no evidence of hemolysis. The patient’s hemoglobin, platelet, and white blood cell count presented below baseline followed by a decrease and slight improvement during his hospital stay. Six days after hospitalization, all three cell lines showed improvement. The temporal association with the booster vaccine and negative infectious disease workup raised suspicion for vaccine-induced bone marrow suppression. In addition, the patient’s reticulocyte count and lactate dehydrogenase value were consistent with hypoproliferation within the bone marrow.

Currently, there is a gap in knowledge of adverse events specific to the third vaccine against SARS-CoV-2 due to the recent initiation of administration and ongoing reporting of events.6 To our knowledge, bone marrow suppression after any dose of vaccine against SARS-CoV-2 has not been previously reported. However, a prior case of pancytopenia after the third vaccination with a recombinant hepatitis B vaccine has previously been reported.9 The patient’s bone marrow biopsy within this case displayed a paucity of late myeloid elements and CD8+ T cells.9 It was believed the patient’s CD8+T cells were causing excessive production of IFN-γ; a stimulant of negative regulators of hematopoiesis such as tumor necrosis factor and lymphotoxin.10 IFN-γ has also previously been reported to create immunological effects comprising an upregulation of histocompatibility gene transcription and alteration in class I and II antigen expression at the cell surface.11 It was predicted these changes resulted in an autoimmune reaction causing suppression of maturation of hematopoietic progenitor cells and pancytopenia.9 Via a similar mechanism, we believe that our patient’s pancytopenia was immune-mediated, potentially triggered by the vaccination.

Vaccines against SARS-CoV-2 (first or second dose) and the induction of Idiopathic Thrombocytopenic Purpura (ITP) have also been recently acknowledged in multiple cases.12 Our patient presented with low platelet levels and associated petechiae and purpura at the site of the vaccination. However, the patient’s presentation of low hemoglobin and white blood cells along with normal reticulocyte levels was more indicative of pancytopenia secondary to bone marrow suppression. In patients presenting with pancytopenia, the history and the physical exam should help assess the severity of the pancytopenia and comorbid illnesses that may complicate the disorder.13 In addition, suspicious medications and exposure to toxic agents should be ruled out.13 Initial screening laboratory evaluation should include the patient’s complete blood count, peripheral blood smear examination, reticulocyte count, complete metabolic panel, prothrombin time/partial thromboplastin time, and blood type and screen. Common interventions to alleviate bone marrow suppression and pancytopenia include treating the underlying cause and utilizing supplements to boost red blood cell production if indicated.

Vaccines against SARS-CoV-2 undergo continuous safety monitoring; adverse events are very rare.14 However, vaccine hesitancy remains a barrier towards full population inoculation against SARS-CoV-2 and is influenced by misinformation regarding vaccine safety.15 One study using an anonymous online questionnaire found a person’s trust in the effectiveness of the vaccine was a major facilitative factor affecting willingness to vaccinate.16 The same study also found that 66.7% of unvaccinated participants thought the vaccine’s safety was not enough, making it the main reason for reluctance or hesitance to be vaccinated.16 Therefore, education of adverse events and available interventions post-vaccination is imperative to prevent the spread of misinformation and combat hesitancy towards vaccination.15

As of September 19, 2021, about 2.2 million people in the United States received a third vaccine against SARS-CoV-2.17 Among those who received the vaccine, 22,000 people reported the effects of the vaccine with no unexpected patterns of adverse reactions.17 Our patient demonstrates abnormal pancytopenia first recorded seven days after receiving the booster vaccine, possibly indicating a rare adverse event from the vaccination given the temporal relationship. While additional studies and observations are indicated to verify bone marrow suppression as an adverse reaction, this case report provides an opportunity for patient education and treatment planning before symptoms arise.

Conclusion

Our case report highlights pancytopenia secondary to bone marrow suppression following Pfizer vaccination against SARS-CoV-2. It is important to consider the possibility of bone marrow suppression following the third vaccine against SARS-CoV-2. Although additional studies are indicated to determine the risk factors and pathogenesis of vaccine-induced bone marrow suppression, prompt evaluation and initiation of interventions can improve patient outcomes.

References

1. Fernandes A, Chaudhari S, Jamil N, Gopalakrishnan G. COVID-19 vaccine. Endocr Pract. 2021;27(2):170–172. doi:10.1016/j.eprac.2021.01.013 [PMC free article] [PubMed] [CrossRef] [Google Scholar]

2. Johansson MA, Quandelacy TM, Kada S, et al. SARS-CoV-2 transmission from people without COVID-19 symptoms. JAMA Network Open. 2021;4(1):e2035057–e2035057. doi:10.1001/jamanetworkopen.2020.35057 [PMC free article] [PubMed] [CrossRef] [Google Scholar]

3. Graham BS. Rapid COVID-19 vaccine development. Science. 2020;368(6494):945–946. doi:10.1126/science.abb8923 [PubMed] [CrossRef] [Google Scholar]

4. Gee J, Marquez P, Su J, et al. First month of COVID-19 vaccine safety monitoring—United States, December 14, 2020–January 13. Morb Mortal Wkly Rep. 2021;70(8):283. doi:10.15585/mmwr.mm7008e3 [PMC free article] [PubMed] [CrossRef] [Google Scholar]

5. Mahase E. Covid-19 booster vaccines: what we know and who’s doing what. BMJ. 2021. doi: 10.1136/bmj.n2082 [PubMed] [CrossRef] [Google Scholar]

6. Centers for Disease Control and Prevention. Selected adverse events reported after COVID-19 vaccination. Centers for Disease Control and Prevention. Available from: https://www.cdc.gov/coronavirus/2019-ncov/vaccines/safety/adverse-events.html. Accessed November 8, 2021. [Google Scholar]

7. Hause AM. Safety monitoring of an additional dose. Centers for Disease Control and Prevention; 2021. Available from: https://www.cdc.gov/mmwr/volumes/70/wr/mm7039e4.htm. Accessed February 11, 2022. [Google Scholar]

8. Valent P. Low blood counts: immune mediated, idiopathic, or myelodysplasia. Hematology. 2012;2012(1):485–491. doi:10.1182/asheducation.V2012.1.485.3798522 [PubMed] [CrossRef] [Google Scholar]

9. Viallard JF, Boiron JM, Parrens M, et al. Severe pancytopenia triggered by recombinant hepatitis B vaccine. Br J Haematol. 2000;110(1):230–233. doi:10.1046/j.1365-2141.2000.02171.x [PubMed] [CrossRef] [Google Scholar]

10. Collart MA, Belin D, Vassalli JD, De Kossodo S, Vassalli P. Gamma interferon enhances macrophage transcription of the tumor necrosis factor/cachectin, interleukin 1, and urokinase genes, which are controlled by short-lived repressors. J Exp Med. 1986;164(6):2113–2118. doi:10.1084/jem.164.6.2113 [PMC free article] [PubMed] [CrossRef] [Google Scholar]

11. Wallach D, Fellous M, Revel M. Preferential effect of gamma interferon on the synthesis of HLA antigens and their mRNAs in human cells. Nature. 1982;299(5886):833–836. doi:10.1038/299833a0 [PubMed] [CrossRef] [Google Scholar]

12. Shah SRA, Dolkar S, Mathew J, et al. COVID-19 vaccination associated severe immune thrombocytopenia. Exp Hematol Oncol. 2021;10:42. doi:10.1186/s40164-021-00235-0 [PMC free article] [PubMed] [CrossRef] [Google Scholar]

13. Elizabeth P, Weinzierl MD, Daniel A, Arber MD. The differential diagnosis and bone marrow evaluation of new-onset pancytopenia. Am J Clin Pathol. 2013;139(1):9–29. doi:10.1309/AJCP50AEEYGREWUZ [PubMed] [CrossRef] [Google Scholar]

14. Centers for Disease Control and Prevention. COVID-19 vaccination; 2020. Available from: https://www.cdc.gov/coronavirus/2019-ncov/vaccines/safety/safety-of-vaccines.html. Accessed February 11, 2022.

15. Dror AA, Eisenbach N, Taiber S, et al. Vaccine hesitancy: the next challenge in the fight against COVID-19. Eur J Epidemiol. 2020;35:775–779. doi:10.1007/s10654-020-00671-y [PMC free article] [PubMed] [CrossRef] [Google Scholar]

16. Gan L, Chen Y, Hu P, et al. Willingness to receive SARS-CoV-2 vaccination and associated factors among Chinese adults: a cross sectional survey. Int J Environ Res Public Health. 2021;18(4):1993. doi:10.3390/ijerph18041993 [PMC free article] [PubMed] [CrossRef] [Google Scholar]

17. STAT. Early data suggest side effects after Covid booster similar to second dose; 2021. Available from: https://www.statnews.com/2021/09/28/side-effect-rates-from-a-third-covid-19-vaccine-dose-similar-to-those-after-second-shot-early-data-indicate/.

Bone Marrow Suppression Secondary to the COVID-19 Booster Vaccine: A Case Report

Authors: Toral Shastri 1Navkiran Randhawa 2Ragia Aly 3Masood Ghouse 3

PMID: 35210894 PMCID: PMC8863340DOI: 10.2147/JBM.S350290

Abstract

As of September 2021, SARS-CoV-2 booster shots became widely available in the US to ensure continued protection against the virus. A temporal relationship has been previously reported between the first or second dose of the COVID-19 vaccine and the development of thrombocytopenia. However, adverse events related to the third COVID-19 vaccine are still being reported and studied. We report a 74-year-old male who developed bone marrow suppression and pancytopenia recorded seven days after receiving the Pfizer SARS-CoV-2 vaccine. During his hospital stay, the patient’s hemoglobin, white blood cell, and platelet levels continued to trend downwards. However, all three levels showed improvement one week after discharge without robust intervention. Global vaccination is of utmost importance, as is understanding and documenting post-vaccination reactions including bone marrow suppression. Prompt evaluation and patient education are imperative to improve patient outcomes and combat hesitancy against vaccine administration.

Introduction

Since its emergence in December of 2019, the rapid spread of severe acute respiratory syndrome coronavirus (SARS-CoV-2) has quickly affected millions of lives across every continent.1 This highly transmittable and pathogenic viral infection has led to massive mitigation efforts and allocation of resources to prevent the spread of transmission and high mortality related to complications.2 The establishment of higher levels of community (herd) immunity and protection against SARS-CoV-2 via the widespread deployment of effective vaccines has become a global effort.3 In December of 2020, the FDA issued an Emergency use Authorization for the Pfizer-BioNTech and Moderna COVID-19 Vaccine as a two-dose series.4 In September 2021, booster vaccines became widely administered in the US due to waning immunity of the COVID-19 vaccines against variants of SARS-CoV-2 along with ensuring continued protection against the virus.5

Serious adverse events such as anaphylaxis, Guillain-Barre Syndrome, myocarditis, pericarditis, thrombocytopenia, and death have been previously reported following the first and/or second dose of vaccine.6 To our knowledge, no cases have been reported regarding bone marrow suppression related to the third COVID-19 vaccine. Adverse events reported between August 12-September 19, 2021 from the COVID-19 booster vaccine supported similar reactions to those after dose two.7 According to the Centers for Disease Control and Prevention (CDC), these initial findings indicate no unexpected patterns of adverse reactions after an additional dose of COVID-19 vaccination.7 However, adverse events related to the COVID-19 booster are still being reported and studied.6 This report presents a case of bone marrow suppression occurring after the third COVID-19 vaccine without a similar reaction after the first or second dose.Go to:

Case Report

A 74-year-old male with a history of polychondritis and hypothyroidism presented to the hospital after falling out of his chair and inability to ambulate. The patient was found to be mildly confused upon arrival to the emergency room, limiting our ability to obtain a full verbal history. Chart review revealed the patient had received his third Pfizer Covid vaccine shot seven days before admission followed by fatigue, decreased appetite, fever, and chills. The patient had received the second Pfizer Covid-19 shot nine months before the booster. No reactions to the previous two shots were noted.

Upon initial evaluation, vital signs were within normal limits and a physical exam revealed significant tenderness in the upper arm and no gross bleeding (Figure 1). Computed tomography (CT) imaging (Figure 2) was significant for enhancement of the left axillary lymph node. The patient’s initial complete blood count (CBC) was remarkable for a hemoglobin count of 9.9 g/dl and platelet count of 84 x 109/L; both values lower than his prior hemoglobin count of 13.7 g/dl and platelet count of 180 x 109/L from December of 2020. His mean corpuscular volume (MCV) was elevated at 101.3 femtolitres from his prior MCV value of 95.8 femtolitres in December of 2020. His white blood cell (WBC) count was recorded at 7.6 x 109/L.

An external file that holds a picture, illustration, etc.
Object name is JBM-13-69-g0001.jpg

Figure 1

The patient’s upper arm showed erythema with no gross bleeding near the injection site

An external file that holds a picture, illustration, etc.
Object name is JBM-13-69-g0002.jpg

Figure 2

The patient’s CT imaging of the thoracic region showed enhancement of the left axillary lymph node.

The hemoglobin, WBC, and platelet count further down trended from his baseline (Figures 3​5).5). Anemia labs including ferritin levels (554 ng/mL), vitamin B12 (253 pg/mL), total bilirubin (0.5 mg/dL), and reticulocyte count (0.8%) were nonsignificant during the patient’s hospital stay. The patient’s left shoulder presented with extensive bruising, erythema, papular rash, warmth, and tenderness on palpation during the hospitalization. An improvement in WBC and platelet levels was noted on day 4 of hospitalization.

An external file that holds a picture, illustration, etc.
Object name is JBM-13-69-g0003.jpg

Figure 3

The patient’s hemoglobin count throughout his hospital course and 6 days after discharge.

An external file that holds a picture, illustration, etc.
Object name is JBM-13-69-g0004.jpg

Figure 4

The patient’s WBC count throughout his hospital course and 6 days after discharge.

An external file that holds a picture, illustration, etc.
Object name is JBM-13-69-g0005.jpg

Figure 5

The patient’s platelet count throughout his hospital course and 6 days after discharge.

Before discharge, the patient was fully alert and oriented and reported improvement in his symptoms. Examination of his lateral left arm showed decreased erythema and bruising with slight petechiae. The patient was discharged due to stabilization of labs and encouraged to take oral vitamin B12 supplements. During his outpatient follow-up six days after hospitalization, his hemoglobin increased to 10.5 g/dl, WBC count increased to 4.9 x 109/L, and platelets increased to 101 x 109/L.

Discussion

This paper presents a patient with pancytopenia recorded seven days after receiving the Pfizer booster vaccine. Interestingly, this patient did not report any reactions after the first or second dose of the Pfizer vaccine against SARS-CoV-2. Pancytopenia refers to a decrease in all peripheral bloodlines and is present when all three cell lines are below the normal reference range.8 The patient’s physical exam showed no signs of active bleeding along with his labs indicating no evidence of hemolysis. The patient’s hemoglobin, platelet, and white blood cell count presented below baseline followed by a decrease and slight improvement during his hospital stay. Six days after hospitalization, all three cell lines showed improvement. The temporal association with the booster vaccine and negative infectious disease workup raised suspicion for vaccine-induced bone marrow suppression. In addition, the patient’s reticulocyte count and lactate dehydrogenase value were consistent with hypoproliferation within the bone marrow.

Currently, there is a gap in knowledge of adverse events specific to the third vaccine against SARS-CoV-2 due to the recent initiation of administration and ongoing reporting of events.6 To our knowledge, bone marrow suppression after any dose of vaccine against SARS-CoV-2 has not been previously reported. However, a prior case of pancytopenia after the third vaccination with a recombinant hepatitis B vaccine has previously been reported.9 The patient’s bone marrow biopsy within this case displayed a paucity of late myeloid elements and CD8+ T cells.9 It was believed the patient’s CD8+T cells were causing excessive production of IFN-γ; a stimulant of negative regulators of hematopoiesis such as tumor necrosis factor and lymphotoxin.10 IFN-γ has also previously been reported to create immunological effects comprising an upregulation of histocompatibility gene transcription and alteration in class I and II antigen expression at the cell surface.11 It was predicted these changes resulted in an autoimmune reaction causing suppression of maturation of hematopoietic progenitor cells and pancytopenia.9 Via a similar mechanism, we believe that our patient’s pancytopenia was immune-mediated, potentially triggered by the vaccination.

Vaccines against SARS-CoV-2 (first or second dose) and the induction of Idiopathic Thrombocytopenic Purpura (ITP) have also been recently acknowledged in multiple cases.12 Our patient presented with low platelet levels and associated petechiae and purpura at the site of the vaccination. However, the patient’s presentation of low hemoglobin and white blood cells along with normal reticulocyte levels was more indicative of pancytopenia secondary to bone marrow suppression. In patients presenting with pancytopenia, the history and the physical exam should help assess the severity of the pancytopenia and comorbid illnesses that may complicate the disorder.13 In addition, suspicious medications and exposure to toxic agents should be ruled out.13 Initial screening laboratory evaluation should include the patient’s complete blood count, peripheral blood smear examination, reticulocyte count, complete metabolic panel, prothrombin time/partial thromboplastin time, and blood type and screen. Common interventions to alleviate bone marrow suppression and pancytopenia include treating the underlying cause and utilizing supplements to boost red blood cell production if indicated.

Vaccines against SARS-CoV-2 undergo continuous safety monitoring; adverse events are very rare.14 However, vaccine hesitancy remains a barrier towards full population inoculation against SARS-CoV-2 and is influenced by misinformation regarding vaccine safety.15 One study using an anonymous online questionnaire found a person’s trust in the effectiveness of the vaccine was a major facilitative factor affecting willingness to vaccinate.16 The same study also found that 66.7% of unvaccinated participants thought the vaccine’s safety was not enough, making it the main reason for reluctance or hesitance to be vaccinated.16 Therefore, education of adverse events and available interventions post-vaccination is imperative to prevent the spread of misinformation and combat hesitancy towards vaccination.15

As of September 19, 2021, about 2.2 million people in the United States received a third vaccine against SARS-CoV-2.17 Among those who received the vaccine, 22,000 people reported the effects of the vaccine with no unexpected patterns of adverse reactions.17 Our patient demonstrates abnormal pancytopenia first recorded seven days after receiving the booster vaccine, possibly indicating a rare adverse event from the vaccination given the temporal relationship. While additional studies and observations are indicated to verify bone marrow suppression as an adverse reaction, this case report provides an opportunity for patient education and treatment planning before symptoms arise.

Conclusion

Our case report highlights pancytopenia secondary to bone marrow suppression following Pfizer vaccination against SARS-CoV-2. It is important to consider the possibility of bone marrow suppression following the third vaccine against SARS-CoV-2. Although additional studies are indicated to determine the risk factors and pathogenesis of vaccine-induced bone marrow suppression, prompt evaluation and initiation of interventions can improve patient outcomes

Consent for Publication

Institutional approval was not required to publish the case details. The publication of this study has been consented to by the patient.

Disclosure

The authors report no conflicts of interest in this work.

1. Fernandes A, Chaudhari S, Jamil N, Gopalakrishnan G. COVID-19 vaccine. Endocr Pract. 2021;27(2):170–172. doi:10.1016/j.eprac.2021.01.013 [PMC free article] [PubMed] [CrossRef] [Google Scholar]

2. Johansson MA, Quandelacy TM, Kada S, et al. SARS-CoV-2 transmission from people without COVID-19 symptoms. JAMA Network Open. 2021;4(1):e2035057–e2035057. doi:10.1001/jamanetworkopen.2020.35057 [PMC free article] [PubMed] [CrossRef] [Google Scholar]

3. Graham BS. Rapid COVID-19 vaccine development. Science. 2020;368(6494):945–946. doi:10.1126/science.abb8923 [PubMed] [CrossRef] [Google Scholar]

4. Gee J, Marquez P, Su J, et al. First month of COVID-19 vaccine safety monitoring—United States, December 14, 2020–January 13. Morb Mortal Wkly Rep. 2021;70(8):283. doi:10.15585/mmwr.mm7008e3 [PMC free article] [PubMed] [CrossRef] [Google Scholar]

5. Mahase E. Covid-19 booster vaccines: what we know and who’s doing what. BMJ. 2021. doi: 10.1136/bmj.n2082 [PubMed] [CrossRef] [Google Scholar]

6. Centers for Disease Control and Prevention. Selected adverse events reported after COVID-19 vaccination. Centers for Disease Control and Prevention. Available from: https://www.cdc.gov/coronavirus/2019-ncov/vaccines/safety/adverse-events.html. Accessed November 8, 2021. [Google Scholar]

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SARS-CoV-2 infection induces long-lived bone marrow plasma cells in humans

Authors: Jackson S. TurnerWooseob KimElizaveta KalaidinaCharles W. GossAdriana M. RauseoAaron J. SchmitzLena HansenAlem HaileMichael K. KlebertIskra PusicJane A. O’HalloranRachel M. Presti & Ali H. Ellebedy 

Nature volume 595, pages421–425 (2021)

Abstract

Long-lived bone marrow plasma cells (BMPCs) are a persistent and essential source of protective antibodies1,2,3,4,5,6,7. Individuals who have recovered from COVID-19 have a substantially lower risk of reinfection with SARS-CoV-28,9,10. Nonetheless, it has been reported that levels of anti-SARS-CoV-2 serum antibodies decrease rapidly in the first few months after infection, raising concerns that long-lived BMPCs may not be generated and humoral immunity against SARS-CoV-2 may be short-lived11,12,13. Here we show that in convalescent individuals who had experienced mild SARS-CoV-2 infections (n = 77), levels of serum anti-SARS-CoV-2 spike protein (S) antibodies declined rapidly in the first 4 months after infection and then more gradually over the following 7 months, remaining detectable at least 11 months after infection. Anti-S antibody titres correlated with the frequency of S-specific plasma cells in bone marrow aspirates from 18 individuals who had recovered from COVID-19 at 7 to 8 months after infection. S-specific BMPCs were not detected in aspirates from 11 healthy individuals with no history of SARS-CoV-2 infection. We show that S-binding BMPCs are quiescent, which suggests that they are part of a stable compartment. Consistently, circulating resting memory B cells directed against SARS-CoV-2 S were detected in the convalescent individuals. Overall, our results indicate that mild infection with SARS-CoV-2 induces robust antigen-specific, long-lived humoral immune memory in humans.

Main

Reinfections by seasonal coronaviruses occur 6 to 12 months after the previous infection, indicating that protective immunity against these viruses may be short-lived14,15. Early reports documenting rapidly declining antibody titres in the first few months after infection in individuals who had recovered from COVID-19 suggested that protective immunity against SARS-CoV-2 might be similarly transient11,12,13. It was also suggested that infection with SARS-CoV-2 could fail to elicit a functional germinal centre response, which would interfere with the generation of long-lived plasma cells3,4,5,7,16. More recent reports analysing samples that were collected approximately 4 to 6 months after infection indicate that SARS-CoV-2 antibody titres decline more slowly than in the initial months after infection8,17,18,19,20,21. Durable serum antibody titres are maintained by long-lived plasma cells—non-replicating, antigen-specific plasma cells that are detected in the bone marrow long after the clearance of the antigen1,2,3,4,5,6,7. We sought to determine whether they were detectable in convalescent individuals approximately 7 months after SARS-CoV-2 infection.

Biphasic decay of anti-S antibody titres

Blood samples were collected approximately 1 month after the onset of symptoms from 77 individuals who were convalescing from COVID-19 (49% female, 51% male, median age 49 years), the majority of whom had experienced mild illness (7.8% hospitalized, Extended Data Tables 12). Follow-up blood samples were collected three times at approximately three-month intervals. Twelve convalescent participants received either the BNT162b2 (Pfizer) or the mRNA-1273 (Moderna) SARS-CoV-2 vaccine between the last two time points; these post-vaccination samples were not included in our analyses. In addition, bone marrow aspirates were collected from 18 of the convalescent individuals at 7 to 8 months after infection and from 11 healthy volunteers with no history of SARS-CoV-2 infection or vaccination. Follow-up bone marrow aspirates were collected from 5 of the 18 convalescent individuals and from 1 additional convalescent donor approximately 11 months after infection (Fig. 1a, Extended Data Tables 34). We first performed a longitudinal analysis of circulating anti-SARS-CoV-2 serum antibodies. Whereas anti-SARS-CoV-2 spike protein (S) IgG antibodies were undetectable in blood from control individuals, 74 out of the 77 convalescent individuals had detectable serum titres approximately 1 month after the onset of symptoms. Between 1 and 4 months after symptom onset, overall anti-S IgG titres decreased from a mean loge-transformed half-maximal dilution of 6.3 to 5.7 (mean difference 0.59 ± 0.06, P < 0.001). However, in the interval between 4 and 11 months after symptom onset, the rate of decline slowed, and mean titres decreased from 5.7 to 5.3 (mean difference 0.44 ± 0.10, P < 0.001; Fig. 1a). In contrast to the anti-S antibody titres, IgG titres against the 2019–2020 inactivated seasonal influenza virus vaccine were detected in all control individuals and individuals who were convalescing from COVID-19, and declined much more gradually, if at all over the course of the study, with mean titres decreasing from 8.0 to 7.9 (mean difference 0.16 ± 0.06, P = 0.042) and 7.9 to 7.8 (mean difference 0.02 ± 0.08, P = 0.997) across the 1-to-4-month and 4-to-11-month intervals after symptom onset, respectively (Fig. 1b).

figure 1
Fig. 1: SARS-CoV-2 infection elicits durable serum anti-S antibody titres.

Induction of S-binding long-lived BMPCs

The relatively rapid early decline in the levels of anti-S IgG, followed by a slower decrease, is consistent with a transition from serum antibodies being secreted by short-lived plasmablasts to secretion by a smaller but more persistent population of long-lived plasma cells generated later in the immune response. The majority of this latter population resides in the bone marrow1,2,3,4,5,6. To investigate whether individuals who had recovered from COVID-19 developed a virus-specific long-lived BMPC compartment, we examined bone marrow aspirates obtained approximately 7 and 11 months after infection for anti-SARS-CoV-2 S-specific BMPCs. We magnetically enriched BMPCs from the aspirates and then quantified the frequencies of those secreting IgG and IgA directed against the 2019–2020 influenza virus vaccine, the tetanus–diphtheria vaccine and SARS-CoV-2 S by enzyme-linked immunosorbent spot assay (ELISpot) (Fig. 2a). Frequencies of influenza- and tetanus–diphtheria-vaccine-specific BMPCs were comparable between control individuals and convalescent individuals. IgG- and IgA-secreting S-specific BMPCs were detected in 15 and 9 of the 19 convalescent individuals, respectively, but not in any of the 11 control individuals (Fig. 2b). Notably, none of the control individuals or convalescent individuals had detectable S-specific antibody-secreting cells in the blood at the time of bone marrow sampling, indicating that the detected BMPCs represent bone-marrow-resident cells and not contamination from circulating plasmablasts. Frequencies of anti-S IgG BMPCs were stable among the 5 convalescent individuals who were sampled a second time approximately 4 months later, and frequencies of anti-S IgA BMPCs were stable in 4 of these 5 individuals but had decreased to below the limit of detection in one individual (Fig. 2c). Consistent with their stable BMPC frequencies, anti-S IgG titres in the 5 convalescent individuals remained consistent between 7 and 11 months after symptom onset. IgG titres measured against the receptor-binding domain (RBD) of the S protein—a primary target of neutralizing antibodies—were detected in 4 of the 5 convalescent individuals and were also stable between 7 and 11 months after symptom onset (Fig. 2d). Frequencies of anti-S IgG BMPCs showed a modest but significant correlation with circulating anti-S IgG titres at 7–8 months after the onset of symptoms in convalescent individuals, consistent with the long-term maintenance of antibody levels by these cells (r = 0.48, P = 0.046). In accordance with previous reports22,23,24, frequencies of influenza-vaccine-specific IgG BMPCs and antibody titres exhibited a strong and significant correlation (r = 0.67, P < 0.001; Fig. 2e). Nine of the aspirates from control individuals and 12 of the 18 aspirates that were collected 7 months after symptom onset from convalescent individuals yielded a sufficient number of BMPCs for additional analysis by flow cytometry. We stained these samples intracellularly with fluorescently labelled S and influenza virus haemagglutinin (HA) probes to identify and characterize antigen-specific BMPCs. As controls, we also intracellularly stained peripheral blood mononuclear cells (PBMCs) from healthy volunteers one week after vaccination against SARS-CoV-2 or seasonal influenza virus (Fig. 3a, Extended Data Fig. 1a–c). Consistent with the ELISpot data, low frequencies of S-binding BMPCs were detected in 10 of the 12 samples from convalescent individuals, but not in any of the 9 control samples (Fig. 3b). Although both recently generated circulating plasmablasts and S- and HA-binding BMPCs expressed BLIMP-1, the BMPCs were differentiated by their lack of expression of Ki-67—indicating a quiescent state—as well as by higher levels of CD38 (Fig. 3c).

figure 2
Fig. 2: SARS-CoV-2 infection elicits S-binding long-lived BMPCs.
figure 3
Fig. 3: SARS-CoV-2 S-binding BMPCs are quiescent and distinct from circulating plasmablasts.

Robust S-binding memory B cell response

Memory B cells form the second arm of humoral immune memory. After re-exposure to an antigen, memory B cells rapidly expand and differentiate into antibody-secreting plasmablasts. We examined the frequency of SARS-CoV-2-specific circulating memory B cells in individuals who were convalescing from COVID-19 and in healthy control individuals. We stained PBMCs with fluorescently labelled S probes and determined the frequency of S-binding memory B cells among isotype-switched IgDloCD20+ memory B cells by flow cytometry. For comparison, we co-stained the cells with fluorescently labelled influenza virus HA probes (Fig. 4a, Extended Data Fig. 1d). S-binding memory B cells were identified in convalescent individuals in the first sample that was collected approximately one month after the onset of symptoms, with comparable frequencies to influenza HA-binding memory B cells (Fig. 4b). S-binding memory B cells were maintained for at least 7 months after symptom onset and were present at significantly higher frequencies relative to healthy controls—comparable to the frequencies of influenza HA-binding memory B cells that were identified in both groups (Fig. 4c).

figure 4
Fig. 4: SARS-CoV-2 infection elicits a robust memory B cell response.

Discussion

This study sought to determine whether infection with SARS-CoV-2 induces antigen-specific long-lived BMPCs in humans. We detected SARS-CoV-2 S-specific BMPCs in bone marrow aspirates from 15 out of 19 convalescent individuals, and in none from the 11 control participants. The frequencies of anti-S IgG BMPCs modestly correlated with serum IgG titres at 7–8 months after infection. Phenotypic analysis by flow cytometry showed that S-binding BMPCs were quiescent, and their frequencies were largely consistent in 5 paired aspirates collected at 7 and 11 months after symptom onset. Notably, we detected no S-binding cells among plasmablasts in blood samples collected at the same time as the bone marrow aspirates by ELISpot or flow cytometry in any of the convalescent or control samples. Together, these data indicate that mild SARS-CoV-2 infection induces a long-lived BMPC response. In addition, we showed that S-binding memory B cells in the blood of individuals who had recovered from COVID-19 were present at similar frequencies to those directed against influenza virus HA. Overall, our results are consistent with SARS-CoV-2 infection eliciting a canonical T-cell-dependent B cell response, in which an early transient burst of extrafollicular plasmablasts generates a wave of serum antibodies that decline relatively quickly. This is followed by more stably maintained levels of serum antibodies that are supported by long-lived BMPCs.

Although this overall trend captures the serum antibody dynamics of the majority of participants, we observed that in three participants, anti-S serum antibody titres increased between 4 and 7 months after the onset of symptoms, after having initially declined between 1 and 4 months. This could be stochastic noise, could represent increased net binding affinity as early plasmablast-derived antibodies are replaced by those from affinity-matured BMPCs, or could represent increases in antibody concentration from re-encounter with the virus (although none of the participants in our cohort tested positive a second time). Although anti-S IgG titres in the convalescent cohort were relatively stable in the interval between 4 and 11 months after symptom onset, they did measurably decrease, in contrast to anti-influenza virus vaccine titres. It is possible that this decline reflects a final waning of early plasmablast-derived antibodies. It is also possible that the lack of decline in influenza titres was due to boosting through exposure to influenza antigens. Our data suggest that SARS-CoV-2 infection induces a germinal centre response in humans because long-lived BMPCs are thought to be predominantly germinal-centre-derived7. This is consistent with a recent study that reported increased levels of somatic hypermutation in memory B cells that target the RBD of SARS-CoV-2 S in convalescent individuals at 6 months compared to 1 month after infection20.

To our knowledge, the current study provides the first direct evidence for the induction of antigen-specific BMPCs after a viral infection in humans. However, we do acknowledge several limitations. Although we detected anti-S IgG antibodies in serum at least 7 months after infection in all 19 of the convalescent donors from whom we obtained bone marrow aspirates, we failed to detect S-specific BMPCs in 4 donors. Serum anti-S antibody titres in those four donors were low, suggesting that S-specific BMPCs may potentially be present at very low frequencies that are below the limit of detection of the assay. Another limitation is that we do not know the fraction of the S-binding BMPCs detected in our study that encodes neutralizing antibodies. SARS-CoV-2 S protein is the main target of neutralizing antibodies17,25,26,27,28,29,30 and a correlation between serum anti-S IgG binding and neutralization titres has been documented17,31. Further studies will be required to determine the epitopes that are targeted by BMPCs and memory B cells, as well as their clonal relatedness. Finally, although our data document a robust induction of long-lived BMPCs after infection with SARS-CoV-2, it is critical to note that our convalescent individuals mostly experienced mild infections. Our data are consistent with a report showing that individuals who recovered rapidly from symptomatic SARS-CoV-2 infection generated a robust humoral immune response32. It is possible that more-severe SARS-CoV-2 infections could lead to a different outcome with respect to long-lived BMPC frequencies, owing to dysregulated humoral immune responses. This, however, has not been the case in survivors of the 2014 Ebola virus outbreak in West Africa, in whom severe viral infection induced long-lasting antigen-specific serum IgG antibodies33.

Long-lived BMPCs provide the host with a persistent source of preformed protective antibodies and are therefore needed to maintain durable immune protection. However, the longevity of serum anti-S IgG antibodies is not the only determinant of how durable immune-mediated protection will be. Isotype-switched memory B cells can rapidly differentiate into antibody-secreting cells after re-exposure to a pathogen, offering a second line of defence34. Encouragingly, the frequency of S-binding circulating memory B cells at 7 months after infection was similar to that of B cells directed against contemporary influenza HA antigens. Overall, our data provide strong evidence that SARS-CoV-2 infection in humans robustly establishes the two arms of humoral immune memory: long-lived BMPCs and memory B cells. These findings provide an immunogenicity benchmark for SARS-CoV-2 vaccines and a foundation for assessing the durability of primary humoral immune responses that are induced in humans after viral infections.

Methods

Data reporting

No statistical methods were used to predetermine sample size. The experiments were not randomized and the investigators were not blinded during outcome assessment.

Sample collection, preparation and storage

All studies were approved by the Institutional Review Board of Washington University in St Louis. Written consent was obtained from all participants. Seventy-seven participants who had recovered from SARS-CoV-2 infection and eleven control individuals without a history of SARS-CoV-2 infection were enrolled (Extended Data Tables 14). Blood samples were collected in EDTA tubes and PBMCs were enriched by density gradient centrifugation over Ficoll 1077 (GE) or Lymphopure (BioLegend). The remaining red blood cells were lysed with ammonium chloride lysis buffer, and cells were immediately used or cryopreserved in 10% dimethyl sulfoxide in fetal bovine serum (FBS). Bone marrow aspirates of approximately 30 ml were collected in EDTA tubes from the iliac crest of 18 individuals who had recovered from COVID-19 and the control individuals. Bone marrow mononuclear cells were enriched by density gradient centrifugation over Ficoll 1077, and the remaining red blood cells were lysed with ammonium chloride buffer (Lonza) and washed with phosphate-buffered saline (PBS) supplemented with 2% FBS and 2 mM EDTA. Bone marrow plasma cells were enriched from bone marrow mononuclear cells using the CD138 Positive Selection Kit II (Stemcell) and immediately used for ELISpot or cryopreserved in 10% dimethyl sulfoxide in FBS.

Antigens

Recombinant soluble spike protein (S) and its receptor-binding domain (RBD) derived from SARS-CoV-2 were expressed as previously described35. In brief, mammalian cell codon-optimized nucleotide sequences coding for the soluble version of S (GenBank: MN908947.3, amino acids (aa) 1–1,213) including a C-terminal thrombin cleavage site, T4 foldon trimerization domain and hexahistidine tag cloned into the mammalian expression vector pCAGGS. The S protein sequence was modified to remove the polybasic cleavage site (RRAR to A) and two stabilizing mutations were introduced (K986P and V987P, wild-type numbering). The RBD, along with the signal peptide (aa 1–14) plus a hexahistidine tag were cloned into the mammalian expression vector pCAGGS. Recombinant proteins were produced in Expi293F cells (Thermo Fisher Scientific) by transfection with purified DNA using the ExpiFectamine 293 Transfection Kit (Thermo Fisher Scientific). Supernatants from transfected cells were collected 3 (for S) or 4 (for RBD) days after transfection, and recombinant proteins were purified using Ni-NTA agarose (Thermo Fisher Scientific), then buffer-exchanged into PBS and concentrated using Amicon Ultracel centrifugal filters (EMD Millipore). For flow cytometry staining, recombinant S was labelled with Alexa Fluor 647- or DyLight 488-NHS ester (Thermo Fisher Scientific); excess Alexa Fluor 647 and DyLight 488 were removed using 7-kDa and 40-kDa Zeba desalting columns, respectively (Pierce). Recombinant HA from A/Michigan/45/2015 (aa 18–529, Immune Technology) was labelled with DyLight 405-NHS ester (Thermo Fisher Scientific); excess DyLight 405 was removed using 7-kDa Zeba desalting columns. Recombinant HA from A/Brisbane/02/2018 (aa 18–529) and B/Colorado/06/2017 (aa 18–546) (both Immune Technology) were biotinylated using the EZ-Link Micro NHS-PEG4-Biotinylation Kit (Thermo Fisher Scientific); excess biotin was removed using 7-kDa Zeba desalting columns.

ELISpot

Plates were coated with Flucelvax Quadrivalent 2019/2020 seasonal influenza virus vaccine (Sequiris), tetanus–diphtheria vaccine (Grifols), recombinant S or anti-human Ig. Direct ex vivo ELISpot was performed to determine the number of total, vaccine-binding or recombinant S-binding IgG- and IgA-secreting cells present in BMPC and PBMC samples using IgG/IgA double-colour ELISpot Kits (Cellular Technology) according to the manufacturer’s instructions. ELISpot plates were analysed using an ELISpot counter (Cellular Technology).

ELISA

Assays were performed in 96-well plates (MaxiSorp, Thermo Fisher Scientific) coated with 100 μl of Flucelvax 2019/2020 or recombinant S in PBS, and plates were incubated at 4 °C overnight. Plates were then blocked with 10% FBS and 0.05% Tween-20 in PBS. Serum or plasma were serially diluted in blocking buffer and added to the plates. Plates were incubated for 90 min at room temperature and then washed 3 times with 0.05% Tween-20 in PBS. Goat anti-human IgG–HRP (Jackson ImmunoResearch, 1:2,500) was diluted in blocking buffer before adding to wells and incubating for 60 min at room temperature. Plates were washed 3 times with 0.05% Tween-20 in PBS, and then washed 3 times with PBS before the addition of o-phenylenediamine dihydrochloride peroxidase substrate (Sigma-Aldrich). Reactions were stopped by the addition of 1 M HCl. Optical density measurements were taken at 490 nm. The half-maximal binding dilution for each serum or plasma sample was calculated using nonlinear regression (GraphPad Prism v.8). The limit of detection was defined as 1:30.

Statistics

Spearman’s correlation coefficients were estimated to assess the relationship between 7-month anti-S and anti-influenza virus vaccine IgG titres and the frequencies of BMPCs secreting IgG specific for S and for influenza virus vaccine, respectively. Means and pairwise differences of antibody titres at each time point were estimated using a linear mixed model analysis with a first-order autoregressive covariance structure. Time since symptom onset was treated as a categorical fixed effect for the 4 different sample time points spaced approximately 3 months apart. P values were adjusted for multiple comparisons using Tukey’s method. All analyses were conducted using SAS v.9.4 (SAS Institute) and Prism v.8.4 (GraphPad), and P values of less than 0.05 were considered significant.

Flow cytometry

Staining for flow cytometry analysis was performed using cryo-preserved magnetically enriched BMPCs and cryo-preserved PBMCs. For BMPC staining, cells were stained for 30 min on ice with CD45-A532 (HI30, Thermo Fisher Scientific, 1:50), CD38-BB700 (HIT2, BD Horizon, 1:500), CD19-PE (HIB19, 1:200), CXCR5-PE-Dazzle 594 (J252D4, 1:50), CD71-PE-Cy7 (CY1G4, 1:400), CD20-APC-Fire750 (2H7, 1:400), CD3-APC-Fire810 (SK7, 1:50) and Zombie Aqua (all BioLegend) diluted in Brilliant Stain buffer (BD Horizon). Cells were washed twice with 2% FBS and 2 mM EDTA in PBS (P2), fixed for 1 h using the True Nuclear permeabilization kit (BioLegend), washed twice with perm/wash buffer, stained for 1h with DyLight 405-conjugated recombinant HA from A/Michigan/45/2015, DyLight 488- and Alexa 647-conjugated S, Ki-67-BV711 (Ki-67, 1:200, BioLegend) and BLIMP-1-A700 (646702, 1:50, R&D), washed twice with perm/wash buffer, and resuspended in P2. For memory B cell staining, PBMCs were stained for 30 min on ice with biotinylated recombinant HAs diluted in P2, washed twice, then stained for 30 min on ice with Alexa 647-conjugated S, IgA-FITC (M24A, Millipore, 1:500), IgG-BV480 (goat polyclonal, Jackson ImmunoResearch, 1:100), IgD-SB702 (IA6-2, Thermo Fisher Scientific, 1:50), CD38-BB700 (HIT2, BD Horizon, 1:500), CD20-Pacific Blue (2H7, 1:400), CD4-BV570 (OKT4, 1:50), CD24-BV605 (ML5, 1:100), streptavidin-BV650, CD19-BV750 (HIB19, 1:100), CD71-PE (CY1G4, 1:400), CXCR5-PE-Dazzle 594 (J252D4, 1:50), CD27-PE-Cy7 (O323, 1:200), IgM-APC-Fire750 (MHM-88, 1:100), CD3-APC-Fire810 (SK7, 1:50) and Zombie NIR (all BioLegend) diluted in Brilliant Stain buffer (BD Horizon), and washed twice with P2. Cells were acquired on an Aurora using SpectroFlo v.2.2 (Cytek). Flow cytometry data were analysed using FlowJo v.10 (Treestar). In each experiment, PBMCs were included from convalescent individuals and control individuals.

Reporting summary

Further information on research design is available in the Nature Research Reporting Summary linked to this paper.

Data availability

Relevant data are available from the corresponding author upon reasonable request.

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Adaptive immunity to SARS-CoV-2 and COVID-19

Authors: Alessandro Sette1,2 and Shane Crotty1,2,* 1Center for Infectious Disease and Vaccine Research, La Jolla Institute for Immunology (LJI), La Jolla, CA 92037, USA
2Department of Medicine, Division of Infectious Diseases and Global Public Health, University of California, San Diego (UCSD), La Jolla, CA
92037, USA

SUMMARY
The adaptive immune system is important for control of most viral infections. The three fundamental components of the adaptive immune system are B cells (the source of antibodies), CD4+ T cells, and CD8+ T cells. The armamentarium of B cells, CD4+ T cells, and CD8+ T cells has differing roles in different viral infections and in vaccines, and thus it is critical to directly study adaptive immunity to SARS-CoV-2 to understand COVID-19. Knowledge is now available on relationships between antigen-specific immune responses and SARS-CoV-2 infection. Although more studies are needed, a picture has begun to emerge that reveals that CD4+ T cells, CD8+ T cells, and neutralizing antibodies all contribute to control of SARS-CoV-2 in both
non-hospitalized and hospitalized cases of COVID-19. The specific functions and kinetics of these adaptive immune responses are discussed, as well as their interplay with innate immunity and implications for COVID19 vaccines and immune memory against re-infection.


INTRODUCTION


Coronavirus disease 2019 (COVID-19), caused by the novel human pathogen severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) (Hu et al., 2020), is a serious disease that has resulted in widespread global morbidity and mortality.


Our understanding of SARS-CoV-2 and COVID-19 has rapidly evolved during 2020. As of December 2020, the United States has experienced >300,000 deaths, winter cases are rising exceptionally fast, and the first interim phase 3 vaccine trial results have been reported. The scientific advances in understanding SARS-CoV-2 and COVID-19 have been extraordinarily rapid and broad, by any metric, which is an amazing testament to the commitment, creativity, collaboration, and expertise of the international scientific community, both in academia and industry, under extremely challenging conditions. This article will review our current understanding of the immunology of COVID-19, with a primary focus on adaptive immunity.


The immune system is broadly divided into the innate immune system and the adaptive immune system. Although the adaptive and innate immune systems are linked in important and powerful ways, they each consist of different cell types with different jobs.


The adaptive immune system consists of three major cell types: B cells, CD4+ T cells, and CD8+ T cells (Figure 1). B cells produce antibodies. CD4+ T cells possess a range of helper and effector functionalities. CD8+ T cells kill infected cells. Given that adaptive immune responses are important for the control and clearance of almost all viral infections that cause disease in humans, and adaptive immune responses and immune memory are central to the success of all vaccines, it is critical to understand adaptive responses to SARS-CoV-2.

ONE INTEGRATED MODEL OF IMMUNE RESPONSES TO SARS-CoV-2

This review first presents a working model of immune responses to SARS-CoV-2, to provide an overarching context, and then the review explores individual compartments and immunological facets of adaptive immunity to SARS-CoV-2 in greater detail. Importantly, this is an evolving model and should not be accepted as definitive; instead, it provides a reference point for interpreting much of the available data in the literature and to identify knowledge gaps that may provide directions for future studies.

For More Information: https://www.cell.com/cell/pdfExtended/S0092-8674(21)00007-6

Pre-existing immunity to SARS-CoV-2: the knowns and unknowns

Authors: Alessandro Sette 1 2Shane Crotty 3 4

Abstract

T cell reactivity against SARS-CoV-2 was observed in unexposed people; however, the source and clinical relevance of the reactivity remains unknown. It is speculated that this reflects T cell memory to circulating ‘common cold’ coronaviruses. It will be important to define specificities of these T cells and assess their association with COVID-19 disease severity and vaccine responses.

As data start to accumulate on the detection and characterization of SARS-CoV-2 T cell responses in humans, a surprising finding has been reported: lymphocytes from 20–50% of unexposed donors display significant reactivity to SARS-CoV-2 antigen peptide pools1,2,3,4.

In a study by Grifoni et al.1, reactivity was detected in 50% of donor blood samples obtained in the USA between 2015 and 2018, before SARS-CoV-2 appeared in the human population. T cell reactivity was highest against proteins other than the coronavirus spike protein, but T cell reactivity was also detected against spike. The SARS-CoV-2 T cell reactivity was mostly associated with CD4+ T cells, with a smaller contribution by CD8+ T cells1. Similarly, in a study of blood donors in the Netherlands, Weiskopf et al.2 detected CD4+ T cell reactivity against SARS-CoV-2 spike peptides in 1 of 10 unexposed subjects and against SARS-CoV-2 non-spike peptides in 2 of 10 unexposed subjects. CD8+ T cell reactivity was observed in 1 of 10 unexposed donors. In a third study, from Germany, Braun et al.3 reported positive T cell responses against spike peptides in 34% of SARS-CoV-2 seronegative healthy donors. Finally, a study of individuals in Singapore, by Le Bert et al.4, reported T cell responses to nucleocapsid protein nsp7 or nsp13 in 50% of subjects with no history of SARS, COVID-19, or contact with patients with SARS or COVID-19. A study by Meckiff using samples from the UK also detected reactivity in unexposed subjects5. Taken together, five studies report evidence of pre-existing T cells that recognize SARS-CoV-2 in a significant fraction of people from diverse geographical locations.

These early reports demonstrate that substantial T cell reactivity exists in many unexposed people; nevertheless, data have not yet demonstrated the source of the T cells or whether they are memory T cells. It has been speculated that the SARS-CoV-2-specific T cells in unexposed individuals might originate from memory T cells derived from exposure to ‘common cold’ coronaviruses (CCCs), such as HCoV-OC43, HCoV-HKU1, HCoV-NL63 and HCoV-229E, which widely circulate in the human population and are responsible for mild self-limiting respiratory symptoms. More than 90% of the human population is seropositive for at least three of the CCCs6. Thiel and colleagues3 reported that the T cell reactivity was highest against a pool of SARS-CoV-2 spike peptides that had homology to CCCs.

What are the implications of these observations? The potential for pre-existing crossreactivity against COVID-19 in a fraction of the human population has led to extensive speculation. Pre-existing T cell immunity to SARS-CoV-2 could be relevant because it could influence COVID-19 disease severity. It is plausible that people with a high level of pre-existing memory CD4+ T cells that recognize SARS-CoV-2 could mount a faster and stronger immune response upon exposure to SARS-CoV-2 and thereby limit disease severity. Memory T follicular helper (TFH) CD4+ T cells could potentially facilitate an increased and more rapid neutralizing antibody response against SARS-CoV-2. Memory CD4+ and CD8+ T cells might also facilitate direct antiviral immunity in the lungs and nasopharynx early after exposure, in keeping with our understanding of antiviral CD4+ T cells in lungs against the related SARS-CoV7 and our general understanding of the value of memory CD8+ T cells in protection from viral infections. Large studies in which pre-existing immunity is measured and correlated with prospective infection and disease severity could address the possible role of pre-existing T cell memory against SARS-CoV-2.

For More Information: https://www.nature.com/articles/s41577-020-0389-z

A long-term perspective on immunity to COVID

Determining the duration of protective immunity to infection by SARS-CoV-2 is crucial for understanding and predicting the course of the COVID-19 pandemic. Clinical studies now indicate that immunity will be long-lasting.

Authors: Andreas Radbruch & Hyun-Dong Chang

Generating immunity against the SARS-CoV-2 coronavirus is of the utmost importance for bringing the COVID-19 pandemic under control, protecting vulnerable individuals from severe disease and limiting viral spread. Our immune systems protect against SARS-CoV-2 either through a sophisticated reaction to infection or in response to vaccination. A key question is, how long does this immunity last? Writing in NatureTurner et al.1 and Wang et al.2 characterize human immune responses to SARS-CoV-2 infection over the course of a year.

There is ongoing discussion about which aspects of the immune response to SARS-CoV-2 provide hallmarks of immunity (in other words, correlates of immunological protection). However, there is probably a consensus that the two main pillars of an antiviral response are immune cells called cytotoxic T cells, which can selectively eliminate infected cells, and neutralizing antibodies, a type of antibody that prevents a virus from infecting cells, and that is secreted by immune cells called plasma cells. A third pillar of an effective immune response would be the generation of T helper cells, which are specific for the virus and coordinate the immune reaction. Crucially, these latter cells are required for generating immunological memory — in particular, for orchestrating the emergence of long-lived plasma cells3, which continue to secrete antiviral antibodies even when the virus has gone.

Immunological memory is not a long-lasting version of the immediate immune reaction to a particular virus; rather, it is a distinct aspect of the immune system. In the memory phase of an immune response, B and T cells that are specific for a virus are maintained in a state of dormancy, but are poised to spring into action if they encounter the virus again or a vaccine that represents it. These memory B and T cells arise from cells activated in the initial immune reaction. The cells undergo changes to their chromosomal DNA, termed epigenetic modifications, that enable them to react rapidly to subsequent signs of infection and drive responses geared to eliminating the disease-causing agent4. B cells have a dual role in immunity: they produce antibodies that can recognize viral proteins, and they can present parts of these proteins to specific T cells or develop into plasma cells that secrete antibodies in large quantities. About 25 years ago5, it became evident that plasma cells can become memory cells themselves, and can secrete antibodies for long-lasting protection. Memory plasma cells can be maintained for decades, if not a lifetime, in the bone marrow6.

The presence in the bone marrow of long-lived, antibody-secreting memory plasma cells is probably the best available predictor of long-lasting immunity. For SARS-CoV-2, most studies so far have analyzed the acute phase of the immune response, which spans a few months after infection, and have monitored T cells, B cells and secreted antibodies7. It has remained unclear whether the response generates long-lived memory plasma cells that secrete antibodies against SARS-CoV-2.

For More Information: https://www.nature.com/articles/d41586-021-01557-z

COVID-19 survivors may possess wide-ranging resistance to the disease

Authors: Rajee Suri rajee.suri@emory.edu

Recovered COVID-19 patients retain broad and effective longer-term immunity to the disease, suggests a recent Emory University study, which is the most comprehensive of its kind so far. The findings have implications for expanding understanding about human immune memory as well as future vaccine development for coronaviruses.

The longitudinal study, published recently on Cell Reports Medicine, looked at 254 patients with mostly mild to moderate symptoms of SARS-CoV-2 infection over a period for more than eight months (250 days) and found that their immune response to the virus remained durable and strong.

Emory Vaccine Center director Rafi Ahmed, PhD, and a lead author on the paper, says the findings are reassuring, especially given early reports during the pandemic that protective neutralizing antibodies did not last in COVID-19 patients.

“The study serves as a framework to define and predict long-lived immunity to SARS-CoV-2 after natural infection. We also saw indications in this phase that natural immunity could continue to persist,” Ahmed says. The research team will continue to evaluate this cohort over the next few years.

Researchers found that not only did the immune response increase with disease severity, but also with each decade of age regardless of disease severity, suggesting that there are additional unknown factors influencing age-related differences in COVID-19 responses. 

In following the patients for months, researchers got a more nuanced view of how the immune system responds to COVID-19 infection. The picture that emerges indicates that the body’s defense shield not only produces an array of neutralizing antibodies but activates certain T and B cells to establish immune memory, offering more sustained defenses against reinfection.

“We saw that antibody responses, especially IgG antibodies, were not only durable in the vast majority of patients but decayed at a slower rate than previously estimated, which suggests that patients are generating longer-lived plasma cells that can neutralize the SARS-CoV-2 spike protein.”

For More Information: https://news.emory.edu/stories/2021/07/covid_survivors_resistance/index.html

Adaptive immune responses to SARS-CoV-2 infection in severe versus mild individuals

Authors: Fan ZhangRui GanZiqi ZhenXiaoli HuXiang LiFengxia ZhouYing LiuChuangeng ChenShuangyu XieBailing ZhangXiaoke Wu & Zhiwei Huang Signal Transduction and Targeted Therapy volume 5, Article number: 156 (2020) 

Abstract

The global Coronavirus disease 2019 (COVID-19) pandemic caused by SARS-CoV-2 has affected more than eight million people. There is an urgent need to investigate how the adaptive immunity is established in COVID-19 patients. In this study, we profiled adaptive immune cells of PBMCs from recovered COVID-19 patients with varying disease severity using single-cell RNA and TCR/BCR V(D)J sequencing. The sequencing data revealed SARS-CoV-2-specific shuffling of adaptive immune repertories and COVID-19-induced remodeling of peripheral lymphocytes. Characterization of variations in the peripheral T and B cells from the COVID-19 patients revealed a positive correlation of humoral immune response and T-cell immune memory with disease severity. Sequencing and functional data revealed SARS-CoV-2-specific T-cell immune memory in the convalescent COVID-19 patients. Furthermore, we also identified novel antigens that are responsive in the convalescent patients. Altogether, our study reveals adaptive immune repertories underlying pathogenesis and recovery in severe versus mild COVID-19 patients, providing valuable information for potential vaccine and therapeutic development against SARS-CoV-2 infection.

Introduction

Coronavirus disease 2019 (COVID-19) caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has raised a global health emergency. Worldwide studies have contributed to the characterization, diagnosis, and treatment of the disease.1,2,3,4 However, the pathogenesis of SARS-CoV-2 infection in humans remains unclear. Previous studies on severe acute respiratory syndrome (SARS),5 Middle East respiratory syndrome,6 and influenza7 demonstrated that immune changes, especially those in peripheral blood lymphocyte subsets, play a critical role in defense against coronavirus infections. Consistently, several studies of COVID-19 patients showed that both humoral and cellular immunity are involved in the pathogenesis of COVID-19.8,9,10 Although most COVID-19 patients presented mild-to-moderate symptoms, some infected individuals did develop severe or critical outcomes. However, the immunological features associated with the disease severity remains largely unknown. In addition, earlier studies on the recovery of SARS patients have shown that complete restoration of peripheral lymphocyte may require a longer period.11 Thus, studies of the immune system of convalescent COVID-19 patients will facilitate understanding of their recovery state and establish the relationship between adaptive immune responses and disease severity if it exists.

For More Information: https://www.nature.com/articles/s41392-020-00263-y

Adaptive immunity to SARS-CoV-2 and COVID-19

Authors: Alessandro Sette1,2 and Shane Crotty1,2,∗

Abstract

The adaptive immune system is important for control of most viral infections. The three fundamental components of the adaptive immune system are B cells (the source of antibodies), CD4+ T cells, and CD8+ T cells. The armamentarium of B cells, CD4+ T cells, and CD8+ T cells has differing roles in different viral infections and in vaccines, and thus it is critical to directly study adaptive immunity to SARS-CoV-2 to understand COVID-19. Knowledge is now available on relationships between antigen-specific immune responses and SARS-CoV-2 infection. Although more studies are needed, a picture has begun to emerge that reveals that CD4+ T cells, CD8+ T cells, and neutralizing antibodies all contribute to control of SARS-CoV-2 in both non-hospitalized and hospitalized cases of COVID-19. The specific functions and kinetics of these adaptive immune responses are discussed, as well as their interplay with innate immunity and implications for COVID-19 vaccines and immune memory against re-infection.

Introduction

Coronavirus disease 2019 (COVID-19), caused by the novel human pathogen severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) (Hu et al., 2020), is a serious disease that has resulted in widespread global morbidity and mortality. Our understanding of SARS-CoV-2 and COVID-19 has rapidly evolved during 2020. As of December 2020, the United States has experienced >300,000 deaths, winter cases are rising exceptionally fast, and the first interim phase 3 vaccine trial results have been reported. The scientific advances in understanding SARS-CoV-2 and COVID-19 have been extraordinarily rapid and broad, by any metric, which is an amazing testament to the commitment, creativity, collaboration, and expertise of the international scientific community, both in academia and industry, under extremely challenging conditions. This article will review our current understanding of the immunology of COVID-19, with a primary focus on adaptive immunity.

The immune system is broadly divided into the innate immune system and the adaptive immune system. Although the adaptive and innate immune systems are linked in important and powerful ways, they each consist of different cell types with different jobs. The adaptive immune system consists of three major cell types: B cells, CD4+ T cells, and CD8+ T cells (Figure 1 ). B cells produce antibodies. CD4+ T cells possess a range of helper and effector functionalities. CD8+ T cells kill infected cells. Given that adaptive immune responses are important for the control and clearance of almost all viral infections that cause disease in humans, and adaptive immune responses and immune memory are central to the success of all vaccines, it is critical to understand adaptive responses to SARS-CoV-2.

For More Information: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7803150/