Link between fever, diarrhea, severe COVID-19, and persistent anti-SARS-CoV-2 antibodies

Authors: By Dr. Liji Thomas, MD Jan 7 2021

Ever since the coronavirus disease 2019 (COVID-19) pandemic began, there have been many attempts to understand the nature and duration of immunity against the causative agent, the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2).

A new preprint research paper appearing on the medRxiv* server describes a link between the persistence of neutralizing antibodies against the virus, disease severity, and specific COVID-19 symptoms.

Permanent immunity is essential if the pandemic is to end. In the earlier SARS epidemic, antibodies were found to last for three or more years after infection in most patients. With the current virus, it may last for six or more months at least, as appears from some reports. Other researchers have concluded that immunity wanes rapidly over the same period, with some patients who were tested positive for antibodies becoming seronegative later on. This discrepancy may be traceable to variation in testing methods, sample sizes and testing time points, as well as disease severity.

Study details

The current study looked at a population of over a hundred convalescent COVID-19 patients, testing most of them for antibodies at five weeks and three months from symptom resolution.

The researchers used a multiplex assay that measured the Immunoglobulin G (IgG) levels against four SARS-CoV-2 antigens, one from SARS-CoV, and four from circulating seasonal coronaviruses. In addition, they carried out an inhibition assay against SARS-CoV-2 spike receptor-binding domain (RBD)-angiotensin-converting enzyme 2 (ACE2) binding and a neutralization assay against the virus. The antibody titers were then plotted against various clinical features and demographic factors.

Antibody titers higher in COVID-19 convalescents

The researchers found that severe disease is correlated with advanced age and the male sex. Patients with underlying vascular disease were more likely to be hospitalized with COVID-19, but those with asthma were relatively spared.

Convalescent COVID-19 patients had higher IgG levels against all four SARS-CoV-2 antigens, relative to controls, and in 98% of cases, at least one of the tests was likely to show higher binding compared to controls. IgGs targeting the viral spike and RBD were likely to be much more discriminatory between SARS-CoV-2 patients and controls. Interestingly, anti-SARS-CoV IgG, as well as anti-seasonal betacoronavirus antibodies, were likely to be higher in these patients.

Anti-spike and anti-nucleocapsid IgG levels, as well as neutralizing antibody titers, were higher in convalescent hospitalized COVID-19 patients than in convalescent non-hospitalized patients, and the titers were positively associated with disease severity.Antibodies against SARS-CoV-2 persist three months after COVID-19 symptom resolution. Sera from COVID-19 convalescent subjects (n=79) collected 5 weeks (w) and 3 months (m) after symptom resolution were subjected to multiplex assay to detect IgG that binds to SARS-CoV-2 S, NTD, RBD and N antigens (A), to RBD-ACE2 binding inhibition assay (B), and to SARS-CoV-2 neutralization assay (C). Dots, lines, and asterisks in red represent non-hospitalized (n=67) and in blue represent hospitalized (n=12) subjects with lines connecting the two time points for individual subjects (*p<0.05 and **p<0.01 by paired t test).Antibodies against SARS-CoV-2 persist three months after COVID-19 symptom resolution. Sera from COVID-19 convalescent subjects (n=79) collected 5 weeks (w) and 3 months (m) after symptom resolution were subjected to multiplex assay to detect IgG that binds to SARS-CoV-2 S, NTD, RBD and N antigens (A), to RBD-ACE2 binding inhibition assay (B), and to SARS-CoV-2 neutralization assay (C). Dots, lines, and asterisks in red represent non-hospitalized (n=67) and in blue represent hospitalized (n=12) subjects with lines connecting the two time points for individual subjects (*p<0.05 and **p<0.01 by paired t test).

Clinical correlates of higher antibody titer

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When antibody titers in non-hospitalized subjects were compared with clinical and demographic variables, they found that older males with a higher body mass index (BMI) and a Charlson Comorbidity Index score >2 were likely to have higher antibody titers. COVID-19 symptoms that correlated with higher antibody levels in these patients comprise fever, diarrhea, abdominal pain and loss of appetite. Chest tightening, headache and sore throat were associated with less severe symptoms.

The link between the specific symptoms listed above with higher antibody titers could indicate that they mark a robust systemic inflammatory response, which in turn is necessary for a strong antibody response. Diarrhea may mark severe disease, but it is strange that in this case, it was not more frequent in the hospitalized cohort. Alternatively, diarrhea may have strengthened the immune antibody response via the exposure of the virus to more immune cells via the damaged enteric mucosa. More study is required to clarify this finding.

Potential substitute for neutralizing assay

The binding assay showed that the convalescent serum at five weeks inhibited RBD-ACE2 binding much more powerfully than control serum. Neutralizing activity was also higher in these sera, but in 15% of cases, convalescent patients showed comparable neutralizing antibody titers to those in control sera. On the whole, however, there was a positive association between neutralizing antibody titer, anti-SARS-CoV-2 IgG titers, and inhibition of ACE2 binding.

Persistent immunity at three months

This study also shows that SARS-CoV-2 antibodies persist in these patients at even three months after symptoms subside, with persistent IgG titers against the SARS-CoV-2 spike, RBD, nucleocapsid and N-terminal domain antigens. Binding and neutralization assays remained highly inhibitory throughout this period. The same was true of antibodies against the other coronaviruses tested as well, an effect that has been seen with other viruses and could be the result of cross-reactive anti-SARS-CoV-2 antibodies. Alternatively, it could be due to the activation of memory B cells formed in response to infection by the seasonal beta-coronaviruses.

Conclusion

IgG titers, particularly against S and RBD, and RBD-ACE2 binding inhibition better differentiate between COVID-19 convalescent and naive individuals than the neutralizing assay,” the researchers concluded.

These could be combined into a single diagnostic test, they suggest, with extreme sensitivity and specificity. The correlation with neutralizing antibody titers could indicate that the neutralizing assay, which is more expensive, sophisticated and expensive, as well as more dangerous for the investigators, could be replaced by the other antibody tests without loss of value.

In short, the study shows that specific antibodies persist for three months at least following recovery; antibody titers correlate with COVID-19-related fever, loss of appetite, abdominal pain and diarrhea; and are also higher in older males with more severe disease, a higher BMI and CCI above 2. Further research would help understand the lowest protective titer that prevents reinfection, and the duration of immunity.

*Important Notice

medRxiv publishes preliminary scientific reports that are not peer-reviewed and, therefore, should not be regarded as conclusive, guide clinical practice/health-related behavior, or treated as established information.Journal reference:

Coronavirus (Covid-19)

A collection of articles and other resources on the Coronavirus (Covid-19) outbreak, including clinical reports, management guidelines, and commentary.

CORONAVIRUS (COVID-19)     VACCINE RESOURCES     VACCINE FAQ https://www.nejm.org/coronavirus

All Journal content related to the Covid-19 pandemic is freely available.

For More Information: https://www.nejm.org/coronavirus

Lack of antibodies against seasonal coronavirus OC43 nucleocapsid protein identifies patients at risk of critical COVID-19

Authors: MartinDugasa1TanjaGrote-Westrickb1UtaMerledMichaelaFontenaylmAndreas E.KremerhFrankHansesijRichardVollenbergcEvaLorentzenbShilpaTiwari-BecklerdJérômeDucheminlSyrineEllouzelMarcelVetterhJuliaFürsthPhilippSchusterkTobiasBrixaClaudia M.DenkingerfgCarstenMüller-TidoweHartmutSchmidtcJoachimKühnb1

Highlights

Does prior infection with seasonal human coronavirus OC43 protect against critical COVID-19?•

Findings: In an international multi-center study inpatients without anti-HCoV OC43 NP antibodies had an increased risk of critical disease.•

Meaning: Prior infections with seasonal HCoV OC43 have a protective effect against critical COVID-19.

Abstract

Background

The vast majority of COVID-19 patients experience a mild disease. However, a minority suffers from critical disease with substantial morbidity and mortality.

Objectives

To identify individuals at risk of critical COVID-19, the relevance of a seroreactivity against seasonal human coronaviruses was analyzed.

Methods

We conducted a multi-center non-interventional study comprising 296 patients with confirmed SARS-CoV-2 infections from four tertiary care referral centers in Germany and France. The ICU group comprised more males, whereas the outpatient group contained a higher percentage of females. For each patient, the serum or plasma sample obtained closest after symptom onset was examined by immunoblot regarding IgG antibodies against the nucleocapsid protein (NP) of HCoV 229E, NL63, OC43 and HKU1.

Results

Median age was 60 years (range 18-96). Patients with critical disease (n=106) had significantly lower levels of anti-HCoV OC43 nucleocapsid protein (NP)-specific antibodies compared to other COVID-19 inpatients (p=0.007). In multivariate analysis (adjusted for age, sex and BMI), OC43 negative inpatients had an increased risk of critical disease (adjusted odds ratio (AOR) 2.68 [95% CI 1.09 – 7.05]), higher than the risk by increased age or BMI, and lower than the risk by male sex. A risk stratification based on sex and OC43 serostatus was derived from this analysis.

Conclusions

Our results suggest that prior infections with seasonal human coronaviruses can protect against a severe course of COVID-19. Therefore, anti-OC43 antibodies should be measured for COVID-19 inpatients and considered as part of the risk assessment for each patient. Hence, we expect individuals tested negative for anti-OC43 antibodies to particularly benefit from vaccination against SARS-CoV-2, especially with other risk factors prevailing.

For More Information: https://www.sciencedirect.com/science/article/pii/S1386653221001141

Lack of antibodies against seasonal coronavirus OC43 nucleocapsid protein identifies patients at risk of critical COVID-19

Authors: Martin Dugas 1Tanja Grote-Westrick 2Uta Merle 3Michaela Fontenay 4Andreas E Kremer 5Frank Hanses 6Richard Vollenberg 7Eva Lorentzen 8Shilpa Tiwari-Heckler 9Jérôme Duchemin 10Syrine Ellouze 11Marcel Vetter 12Julia Fürst 13Philipp Schuster 14Tobias Brix 15Claudia M Denkinger 16Carsten Müller-Tidow 17Hartmut Schmidt 18Phil-Robin Tepasse 19Joachim Kühn 20

Abstract

Background: The vast majority of COVID-19 patients experience a mild disease. However, a minority suffers from critical disease with substantial morbidity and mortality.

Objectives: To identify individuals at risk of critical COVID-19, the relevance of a seroreactivity against seasonal human coronaviruses was analyzed.

Methods: We conducted a multi-center non-interventional study comprising 296 patients with confirmed SARS-CoV-2 infections from four tertiary care referral centers in Germany and France. The ICU group comprised more males, whereas the outpatient group contained a higher percentage of females. For each patient, the serum or plasma sample obtained closest after symptom onset was examined by immunoblot regarding IgG antibodies against the nucleocapsid protein (NP) of HCoV 229E, NL63, OC43 and HKU1.

Results: Median age was 60 years (range 18-96). Patients with critical disease (n=106) had significantly lower levels of anti-HCoV OC43 nucleocapsid protein (NP)-specific antibodies compared to other COVID-19 inpatients (p=0.007). In multivariate analysis (adjusted for age, sex and BMI), OC43 negative inpatients had an increased risk of critical disease (adjusted odds ratio (AOR) 2.68 [95% CI 1.09 – 7.05]), higher than the risk by increased age or BMI, and lower than the risk by male sex. A risk stratification based on sex and OC43 serostatus was derived from this analysis.

Conclusions: Our results suggest that prior infections with seasonal human coronaviruses can protect against a severe course of COVID-19. Therefore, anti-OC43 antibodies should be measured for COVID-19 inpatients and considered as part of the risk assessment for each patient. Hence, we expect individuals tested negative for anti-OC43 antibodies to particularly benefit from vaccination against SARS-CoV-2, especially with other risk factors prevailing.

For More Information: https://pubmed.ncbi.nlm.nih.gov/33965698/

Trained Innate Immunity, Epigenetics, and Covid-19

Authors: Alberto Mantovani, M.D., and Mihai G. Netea, M.D.

Innate immunity is mediated by different cell types and cell-associated or fluid-phase pattern-recognition molecules and plays a key role in tissue repair and resistance against pathogens.1 Exposure to selected vaccines, such as bacille Calmette–Guérin (BCG) or microbial components, can increase the baseline tone of innate immunity and trigger pathogen-agnostic antimicrobial resistance (known as trained innate immunity). Such training is directly relevant to resistance against infectious diseases, including Covid-19. A recent study by de Laval et al.2 pinpoints a driver of durable innate immune memory conferred by myeloid cells (monocytes, macrophages, and neutrophils).

Myeloid cells are central players in innate immunity: they produce effector molecules and contribute to the activation, orientation, and regulation of adaptive immune responses. Diversity and plasticity are fundamental properties of myeloid cells, particularly macrophages. To some extent, these properties are imprinted through ontogenetic origin (embryonal vs. adult bone marrow), but they are also influenced by environmental cues in the tissue. Moreover, in response to microbial molecules, metabolic products, or cytokines, macrophages increase effector function (“activation”), are primed for short-term responses (“priming”), or become unresponsive (“tolerance”). Microbial components can also cause long-term imprinting (“training”) of innate immunity and myeloid-cell function (Figure 1).3 (This type of imprinting is distinct from genomic imprinting whereby methyl groups are added to DNA in or near specific genes.)

For More Information: https://www.nejm.org/doi/10.1056/NEJMcibr2011679

Multi-layered transcriptomic analyses reveal an immunological overlap between COVID-19 and hemophagocytic lymphohistiocytosis associated with disease severity

Authors: Lena F. Schimkea,5, Alexandre H.C. Marquesa, Gabriela Crispim Baiocchia, Caroline Aliane de Souza Pradob Dennyson Leandro M. Fonsecab , Paula Paccielli Freirea , Desirée Rodrigues Plaçab , Igor Salerno Filgueirasa ,Ranieri Coelho Salgadoa, Gabriel Jansen-Marquesc, Antonio Edson Rocha liveirab
, Jean PierreSchatzmann Perona, José Alexandre Marzagão Barbutoa,d, Niels Olsen Saraiva Camaraa
, Vera Lúcia Garcia Calicha , Hans D. Ochse, Antonio Condino-Netoa, Katherine A. Overmyerf,g, Joshua J. Coonh,i, JosephBalnisj,k, Ariel Jaitovichj,k, Jonas Schulte-Schreppingl, Thomas Ulasm, Joachim L. Schultzel,m, Helder I.Nakayab, Igor Jurisican,o,p, Otavio Cabral-Marquesa,b,q

ABSTRACT
Clinical and hyperinflammatory overlap between COVID-19 and hemophagocytic lymphohistiocytosis (HLH) has been reported. However, the underlying mechanisms are unclear. Here we show that COVID-19 and HLH have an overlap of signaling pathways and gene signatures commonly dysregulated, which were defined by investigating the transcriptomes of
1253 subjects (controls, COVID-19, and HLH patients) using microarray, bulk RNA-sequencing (RNAseq), and single-cell RNAseq (scRNAseq). COVID-19 and HLH share pathways involved in cytokine and chemokine signaling as well as neutrophil-mediated immune responses that associate with COVID-19 severity. These genes are dysregulated at protein level across several
COVID-19 studies and form an interconnected network with differentially expressed plasma proteins which converge to neutrophil hyperactivation in COVID-19 patients admitted to the intensive care unit. scRNAseq analysis indicated that these genes are specifically upregulated across different leukocyte populations, including lymphocyte subsets and immature neutrophils.


Artificial intelligence modeling confirmed the strong association of these genes with COVID-19 severity. Thus, our work indicates putative therapeutic pathways for intervention.

INTRODUCTION
More than one year of Coronavirus disease 2019 (COVID-19) pandemic caused by the severe acute respiratory syndrome Coronavirus (SARS-CoV)-2, more than 197 million cases and 4,2 million deaths have been reported worldwide (July 30th 2021, WHO COVID-19 Dashboard). The clinical presentation ranges from asymptomatic to severe disease manifesting as pneumonia, acute respiratory distress syndrome (ARDS), and a life-threatening hyperinflammatory syndrome associated with excessive cytokine release (hypercytokinaemia)1–3 . Risk factors for severe manifestation and higher mortality include old age as well as hypertension, obesity, and diabetes4. Currently, COVID-19 continues to spread, new variants of SARS-CoV-2 have been reported and the number of infections resulting in death of young individuals with no comorbidities has increased the mortality rates among the young population 5,6. In addition, some novel SARS-CoV-2 variants of concern appear to escape neutralization by vaccine-induced humoral immunity7 . Thus, the need for a better understanding of the immunopathologic mechanisms associated with severe SARS-CoV-2 infection.


Patients with severe COVID-19 have systemically dysregulated innate and adaptive immune responses, which are reflected in elevated plasma levels of numerous cytokines and chemokines including granulocyte colony-stimulating factor (GM-CSF), tumor necrosis factor (TNF), interleukin (IL)-6, IL-6R, IL18, CC chemokine ligand 2 (CCL2) and CXC chemokine ligand 10
(CXCL10)8–10 , and hyperactivation of lymphoid and myeloid cells11. Notably, the hyperinflammation in COVID-19 shares similarities with cytokine storm syndromes such as those triggered by sepsis, autoinflammatory disorders, metabolic conditions and malignancies12–14 ,often resembling a hematopathologic condition called hemophagocytic lymphohistiocytosis
(HLH)15. HLH is a life-threatening progressive systemic hyperinflammatory disorder characterized by multi-organ involvement, fever flares, hepatosplenomegaly, and cytopenia due to hemophagocytic activity in the bone marrow15–17 or within peripheral lymphoid organs such as pulmonary lymph nodes and spleen. HLH is marked by aberrant activation of B and T lymphocytes and monocytes/macrophages, coagulopathy, hypotension, and ARDS. Recently, neutrophil hyperactivation has been shown to also play a critical role in HLH development18,19. This is in agreement with the observation that the HLH-like phenotype observed in severe COVID-19 patients is due to an innate neutrophilic hyperinflammatory response associated with available under aCC-BY-NC-ND 4.0 International license. (which was not certified by peer review) is the author/funder, who has granted bioRxiv a license to display the preprint in perpetuity.

It is made bioRxiv preprint doi: ttps://doi.org/10.1101/2021.07.30.454529; this version posted August 1, 2021. The copyright holder for this preprint
virus-induced hypercytokinaemia which is dominant in patients with an unfavorable clinical course17 . Thus, HLH has been proposed as an underlying etiologic factor of severe COVID191,3,20. HLH usually develops during the acute phase of COVID-191,20–27 . However, a case of HLH that occurred two weeks after recovery from COVID-19 has recently been reported as the cause
of death during post-acute COVID-19 syndrome28
.
The familial form of HLH (fHLH) is caused by inborn errors of immunity (IEI) in different genes encoding proteins involved in granule-dependent cytotoxic activity of leukocytes such as AP3B1, LYST, PRF1, RAB27A, STXBP2, STX11, UNC13D29–31. In contrast, the secondary form (sHLH) usually manifests in adults following a viral infection (e.g., adenovirus, EBV, enterovirus, hepatitis viruses, parvovirus B19, and HIV)32,33, or in association with autoimmune /rheumatologic, malignant, or metabolic conditions that lead to defects in T/NK cell functions and excessive inflammation16,31. fHLH and sHLH affect both children and adults, however, the clinical and genetic distinction of HLH forms is not clear since immunocompetent children can develop sHLH 34,35, while adult patients with sHLH may also have germline mutations in HLH genes36. Of note, germline variants in UNC13D and AP3B1 have also been
identified in some COVID-19 patients with HLH phenotype37, thus, indicating that both HLH forms may be associated with COVID-19.


Here, we characterized the signaling pathways and gene signatures commonly dysregulated in both COVID-19 and HLH patients by investigating the transcriptomes of 1253 subjects (controls, COVID-19, and HLH patients) assessed by microarray, bulk RNA-sequencing (RNAseq), and single-cell RNAseq (scRNAseq) (Table 1). We found shared gene signatures and cellular signaling pathways involved in cytokine and chemokine signaling as well as neutrophilmediated immune responses that associate with COVID-19 severity.

For More Information: https://www.biorxiv.org/content/10.1101/2021.07.30.454529v1.full.pdf

Good news: Mild COVID-19 induces lasting antibody protection

People who have had mild illness develop antibodyproducing cells that can last lifetime

Authors: by Tamara Bhandari•May 24, 2021

Months after recovering from mild cases of COVID-19, people still have immune cells in their body pumping out antibodies against the virus that causes COVID-19, according to a study from researchers at Washington University School of Medicine in St. Louis. Such cells could persist for a lifetime, churning out antibodies all the while.

The findings, published May 24 in the journal Nature, suggest that mild cases of COVID-19 leave those infected with lasting antibody protection and that repeated bouts of illness are likely to be uncommon.

“Last fall, there were reports that antibodies wane quickly after infection with the virus that causes COVID-19, and mainstream media interpreted that to mean that immunity was not long-lived,” said senior author Ali Ellebedy, PhD, an associate professor of pathology & immunology, of medicine and of molecular microbiology. “But that’s a misinterpretation of the data. It’s normal for antibody levels to go down after acute infection, but they don’t go down to zero; they plateau. Here, we found antibody-producing cells in people 11 months after first symptoms. These cells will live and produce antibodies for the rest of people’s lives. That’s strong evidence for long-lasting immunity.”

For More Information: https://medicine.wustl.edu/news/good-news-mild-covid-19-induces-lasting-antibody-protection/

COVID-19 Science Update released: June 4, 2021 Edition 92

Authors: From the Office of the Chief Medical Officer, CDC COVID-19 Response, and the CDC Library, Atlanta GA. Intended for use by public health professionals responding to the COVID-19 pandemic.

PEER-REVIEWED

Safety, immunogenicity, and efficacy of the BNT162b2 COVID-19 vaccine in adolescents.external icon Frenck et al. NEJM (May 27, 2021).

Key findings:

  • Vaccine efficacy was 100% (95% CI 75.3%-100%) in 12- to 15-year-olds.
    • There were no cases in the vaccinated group compared with 16 cases among the placebo group, 7 or more days after dose 2.
  • Compared with baseline, geometric mean neutralizing antibody titers were 118.3-fold higher 1 month after dose 2.
  • Vaccine reactions were mainly transient, mild to moderate, and similar to a comparator group of 16–25-year-olds.
    • Injection-site pain was reported by 79% to 86%, fatigue was reported by 60% to 66%, and headache was reported by 55% to 65% of participants (Figure).

Methods: A randomized, placebo-controlled, observer-blinded trial of Pfizer/BioNTech BNT162b2 in 2,260 adolescents 12–15 years old (1,129 received placebo). Efficacy of the vaccine was assessed based on confirmed SARS-CoV-2 infection with onset 7 or more days after dose 2. Reactogenicity events (assessed for 7 days after each dose) and unsolicited adverse events compared with 16–25 age group (n = 3,610). SARS-CoV-2 serum neutralization assays were performed. LimitationsRacial and ethnic diversity of participants 12-15 years does not reflect the general US population; short (1 month) post-vaccination safety evaluation.

Implications: Vaccination of adolescents with BNT162b2 was safe and effective. Vaccinating adolescents will broaden community protection, and it will likely facilitate reintegration into society and resumption of in-person learning.

Figure:Graphs showing systemic events with 7 days after dose 1 or dose 2 of vaccine or placeboresize iconView Larger

Note: Adapted from Frenck et al. Systemic events reported within 7 days after receiving dose 1 (top) or dose 2 (bottom) of vaccine or placebo. 1 participant in the 12-to-15-year-old group had a fever with a temperature >40°C after dose 1. From the New England Journal of Medicine, Frenck et al., Safety, immunogenicity, and efficacy of the BNT162b2 COVID-19 vaccine in adolescents. May 27, 2021, online ahead of print. Copyright © 2021 Massachusetts Medical Society. Reprinted with permission from Massachusetts Medical Society.

Occurrence of severe COVID-19 in vaccinated transplant patientsexternal icon. Caillard et al. Kidney International. (May 21, 2021).

Key findings:

  • 55 solid organ transplant recipients developed COVID-19 after receiving 2 doses of mRNA vaccine.
    • Symptoms began a median of 22 days after the second vaccine dose (Figure).
    • 15 cases required hospitalization; of these, 6 were admitted to an intensive care unit, and 3 died.
  • Of 25 patients with post-vaccination serology, 24 were antibody negative; 1 was antibody positive but had low titers.

For More Information: https://www.cdc.gov/library/covid19/06042021_covidupdate.html

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 

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 titers 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.

For More Information: https://www.nature.com/articles/s41586-021-03647-4

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