Lab study of South African SARS-CoV-2 variant and Moderna vaccine: reduced neutralization, but still protective

As the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) pandemic rages on, several virus variants have been emerging with mutations in the structural and non-structural proteins. The SARS-CoV-2 spike protein binds to the host angiotensin-converting enzyme 2 (ACE2) receptor, facilitating viral entry into the host cell. Studies have shown many different mutations in the spike protein over the last twelve months.

The first significant spike protein variant emerged with a mutation from aspartic acid (D) to glycine (G) at position 614, leading to increased viral fitness, replication, and binding to ACE2 and conformational changes within the protein. Several other variants have emerged over the past few months, raising concerns about changes to transmission, nature of the disease, and viral fitness.

When SARS-CoV-2 infects humans, our immune system rapidly responds against the viral spike protein. The receptor-binding motif in the spike protein interacts with the ACE2 receptor and is a key target of neutralization for antibodies. Longitudinal studies have found that the antibodies to the spike protein can remain in the body for at least a year following infection.

The mRNA-1273 vaccine encodes the SARS-CoV-2 spike protein and triggers a potent neutralizing antibody response to the virus that lasts for several months. The B.1.351 variant originated in South Africa has three mutations in the receptor-binding domain and many other mutations in the spike protein, all of which may influence viral binding to the ACE2 receptor and viral resistance to neutralization by antibodies.

Comparing antibody binding and viral neutralization against two different SARS-CoV-2 variants

Researchers from the US recently compared antibody binding and viral neutralization against 2 SARS-CoV-2 variants that emerged in different parts of the world. The researchers used sera from spike mRNA vaccinated and naturally infected individuals against a circulating B.1 variant and the emerging B.1.351 variant. The study is published on the preprint server bioRxiv*.

Study: Reduced binding and neutralization of infection- and vaccine-induced antibodies to the B.1.351 (South African) SARS-CoV-2 variant. Image Credit: NIAID

EHC-083E (the B.1 variant) belongs to the B.1 PANGO lineage and was isolated in March 2020 from a nasopharyngeal swab of a patient in Atlanta, GA. This variant has the D614G mutation in the viral spike protein. The B.1.351 variant was isolated in November 2020 from an oropharyngeal swab of a patient in KwaZulu-Natal, South Africa. This variant of the virus contains amino acid mutations (L18F, D80A, D215G) within the viral spike protein and deletion at positions 242-244 (L242del, A243del, and L244del), K417N, E484K, N501Y, and D614G.

Neutralizing antibodies for B.1.351 variant are produced early in the infection phase

The researchers observed decreased antibody binding to the B.1.351-derived receptor binding domain of the SARS-CoV-2 spike protein and neutralization power against the B.1.351 variant in sera from both infected and vaccinated individuals. Their longitudinal convalescent COVID-19 cohort assessed the impact on antibody binding to the receptor-binding domain and neutralization across the SARS-CoV-2 variants. Interestingly, most convalescent COVID-19 individuals showed less impact on neutralization against the B.1.351 variant at longer durations post-infection. This showed that neutralizing antibodies for the B.1.351 variant is produced early during infection and last for several months.

Most SARS-CoV-2-infected individuals showed binding and neutralizing titers against the B.1.351 variant in both acute and convalescent sera

According to the observations, most sera samples from acute and convalescent COVID-19 individuals showed antibody binding to the B.1.351-dervied receptor binding domain.  Most samples also showed a neutralizing capacity for the B.1.351 variant, and the effector functions of these neutralizing antibodies might contribute to SARS-CoV-2 infection control.

To summarize, although decreased by a few folds, most SARS-CoV-2 infected individuals showed binding and neutralizing titers against the B.1.351 variant in acute as well as convalescent sera. Moreover, all mRNA-1273 vaccinated individuals still maintained viral neutralization. These findings agree with previous notions that natural infection- and vaccine-induced immunity can offer protection against COVID-19 in the context of the SARS-CoV-2 B.1.351 variant.

“Our results show that despite few fold decrease, most infected individuals showed binding and neutralizing titers against the B.1.351 variant in acute and convalescent sera, and further, all mRNA-1273 vaccinated individuals still maintained neutralization.”

*Important Notice

bioRxiv 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:
  • Reduced binding and neutralization of infection- and vaccine-induced antibodies to the B.1.351 (South African) SARS-CoV-2 variant, Venkata Viswanadh Edara, Carson Norwood, Katharine Floyd, Lilin Lai, Meredith E. Davis-Gardner, William H. Hudson, Grace Mantus, Lindsay E. Nyhoff, Max W. Adelman, Rebecca Fineman, Shivan Patel, Rebecca Byram, Dumingu Nipuni Gomes, Garett Michael, Hayatu Abdullahi, Nour Beydoun, Bernadine Panganiban, Nina McNair, Kieffer Hellmeister, Jamila Pitts, Joy Winters, Jennifer Kleinhenz, Jacob Usher, James B. O’Keefe, Anne Piantadosi, Jesse J. Waggoner, Ahmed Babiker, David S. Stephens, Evan J. Anderson, Srilatha Edupuganti, Nadine Rouphael, Rafi Ahmed, Jens Wrammert, Mehul S. Suthar, bioRxiv, 2021.02.20.432046; doi: https://doi.org/10.1101/2021.02.20.432046, https://www.biorxiv.org/content/10.1101/2021.02.20.432046v1

Posted in: Medical Research News | Disease/Infection News

Tags: ACE2, Amino Acid, Angiotensin, Angiotensin-Converting Enzyme 2, Antibodies, Antibody, Aspartic Acid, Cell, Coronavirus, Coronavirus Disease COVID-19, Enzyme, Glycine, Immune System, Infection Control, Mutation, Pandemic, Protein, Receptor, Respiratory, SARS, SARS-CoV-2, Severe Acute Respiratory, Severe Acute Respiratory Syndrome, Spike Protein, Syndrome, Vaccine, Virus

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Written by

Susha Cheriyedath

Susha has a Bachelor of Science (B.Sc.) degree in Chemistry and Master of Science (M.Sc) degree in Biochemistry from the University of Calicut, India. She always had a keen interest in medical and health science. As part of her masters degree, she specialized in Biochemistry, with an emphasis on Microbiology, Physiology, Biotechnology, and Nutrition. In her spare time, she loves to cook up a storm in the kitchen with her super-messy baking experiments.

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COVID-19 vaccine candidate shows potential against SARS-CoV-2 and potential future zoonotic coronaviruses

Over the last two decades, three major outbreaks of highly pathogenic coronaviruses have occurred. The third is the ongoing coronavirus disease 2019 (COVID-19) pandemic that has claimed well over 2.46 million human lives so far, in a little over a year from its onset. Without any targeted, safe and effective antivirals to prevent or treat the infection by the causative pathogen, the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), population immunity via mass vaccination seems to be the only way out – as complex and expensive as the process is likely to be.

Study: SARS-CoV-2 vaccination induces neutralizing antibodies against pandemic and pre-emergent SARS-related coronaviruses in monkeys. Image Credit: Numstocker / Shutterstock

Pan-group 2b CoV vaccine

A new study, released on the bioRxiv* preprint server, sheds light on the threat posed by future zoonotic coronaviruses to make similar leaps across species barriers to infect human beings and cause other pandemics. The goal would appear to be a vaccine capable of inducing not limited immunity against SARS-CoV-2 alone, but one that can elicit broadly neutralizing antibody and cellular immune responses against a range of other betaCoVs.

This includes existing SARS-related coronaviruses (SARSr-CoVs) in humans, as well as those that are now circulating in animals.

The first evidence that this could be so came from the observation that SARS-CoV caused the production of cross-neutralizing antibodies against many betacoronaviruses (betaCoVs). This proof-of-concept drove the search for a vaccine that would induce neutralizing antibodies against multiple group 2b Sarbecoviruses.

Cross-neutralizing antibodies

Cross-neutralizing antibodies always target the viral receptor-binding domain (RBD) via a specific epitope. The RBD can be rendered more immunogenic by using a multimeric form. One way to achieve this is by using nanoparticles to mount arrays of RBD proteins, creating a virus-like particle (VLP).

Vaccines have been shown to successfully induce cross-neutralizing antibodies against pseudoviruses expressing CoV antigens in mouse studies. The current study describes a non-human primate (NHP) study that explores the cross-neutralizing ability of a SARS-CoV-2 vaccine based on multimeric SARS-CoV-2 RBD-bearing nanoparticles.

RBD-conjugated nanoparticle vaccine

The RBD-conjugated nanoparticle vaccine comprises 24 RBD protomers on a sortase-ferritin platform for the sake of versatility. This bound not only to the human host cell receptor, the angiotensin-converting enzyme 2 (ACE2), which is thought to be the SARS-CoV-2 entry receptor, but also to potent anti-RBD neutralizing antibodies. These include DH1041, DH1042, DH1043, DH1044, and DH1045.

All these antibodies bind to epitopes within the receptor-binding motif, within the RBD. However, antibodies that bound to epitopes outside the RBD were not able to bind the RBD-bearing nanoparticle. In contrast, it did show binding to the cross-neutralizing antibody DH1047.

This vaccine was assessed by a three-dose regimen, administered at four-week intervals, in a non-human primate (NHP) study. The vaccine was found to result in high plasma levels of antibodies to the SARS-CoV-2 RBD and to the stabilized spike protein.

The antibodies completely blocked the ACE2 binding site on the spike protein after two doses of vaccine and partially blocked the binding of the RBD antibody DH104.

SARS-CoV-2 receptor binding domain (RBD) sortase conjugated nanoparticles (scNPs) elicits extremely high titers of SARS-CoV-2 pseudovirus neutralizing antibodies. a. SARS-CoV-2 RBD nanoparticles were constructed by expressing RBD with a C-terminal sortase A donor sequence (blue and red) and a Helicobacter pylori ferritin nanoparticle with N737 terminal sortase A acceptor sequences (gray) on each subunit (top left). The RBD is shown in blue with the ACE2 binding site in red. The RBD was conjugated to nanoparticles by a sortase A (SrtA) enzyme conjugation reaction (top right). The resultant nanoparticle is modeled on the bottom left. Nine amino acid sortase linker is shown in orange. Two dimensional class averages of negative stain electron microscopy images of actual RBD nanoparticles are shown on the bottom right. b. Antigenicity of RBD nanoparticles determined by biolayer interferometry against a panel of SARS-CoV-2 antibodies and the ACE2 receptor. Antibodies are color-coded based on epitope and function. N-terminal domain (NTD), nonAbs IE, infection enhancing non-neutralizing antibody; nAb, neutralizing antibody; nonAb, non-neutralizing antibody. Mean and standard error from 3 independent experiments are shown. c. Cynomolgus macaque challenge study scheme. Blue arrows indicate 748 RBD-NP immunization timepoints. Intranasal/intratracheal SARS-CoV-2 challenge is indicated at week 10. d. Macaque serum IgG binding determined by ELISA to recombinant SARS-CoV-2 stabilized Spike ectodomain (S-2P), RBD, NTD, and Fusion peptide (FP). Binding titer is shown as area752under-the curve of the log10-transformed curve. Arrows indicate immunization timepoints. e. Plasma antibody blocking of SARS-CoV-2 S-2P binding to ACE2-Fc and RBD neutralizing antibody DH1041. Group mean and standard error are shown. f. Dose-dependent serum neutralization of SARS-COV-2 pseudotyped virus infection of ACE2- expressing 293T cells. Serum was collected after two immunizations. The SARS-CoV-2 pseudovirus spike has an aspartic acid to glycine change at position 614 (D614G). Each curve represents a single macaque. g. Heat map of serum neutralization ID50 and ID80 titers for SARS-COV-2 D614G pseudotyped virus after two immunizations. h. SARS-COV-2 D614G pseudotyped virus serum neutralization kinetics. Each curve represents a single macaque. i. Comparison of serum neutralization ID50 titers from cynomolgus macaques immunized with recombinant protein RBD nanoparticles (blue) or nucleoside-modified mRNA-LNP expressing S- 2P (burgundy) (**P<0.01, Two-tailed Exact Wilcoxon test n = 5). j. Comparison of serum neutralization titers obtained from RBD-scNP-vaccinated macaques (blue) and SARS-CoV-2 infected humans (shades of green). Human samples were stratified based on disease severity as asymptomatic (N=34), symptomatic (n=71), and hospitalized (N=60) (**P<0.01, Two-tailed Wilcoxon test n = 5).

Competitive with the Moderna/Pfizer vaccine for neutralizing antibody titer

When tested against the currently dominant D614G strain of SARS-CoV-2, the RBD-conjugated nanoparticle vaccine induced higher neutralizing antibody titers than another vaccine similar to the Moderna and Pfizer lipid-encapsulated nucleoside-modified mRNA (mRNA-LNP) vaccines that are now being used in the vaccination campaigns against COVID-19.

The measure of antibody titer used here showed an eight-fold increase with the former compared to the latter. The antibody response was also higher with the RBD-nanoparticle vaccine than with natural infection of all grades of severity.

Unaffected by emerging variants

It also showed potent neutralizing activity against the new SARS-CoV-2 variant B.1.1.7, which is rapidly spreading worldwide. This is not only more infective but may be resistant to many RBD-targeting antibodies, as well as more virulent.

While changes in binding affinity of anti-RBD antibody DH1041 to the ACE2 receptor and to the spike protein were observed with different mutations, such as those acquired during mink infection, or those found in the South African or Brazil or UK strains, the cross-neutralizing antibody DH1047 showed unchanged binding to the SARS-CoV-2.

“RBD-scNP (RBD sortase A conjugated nanoparticle) and mRNA-LNP-induced RBD binding antibodies were not sensitive to spike mutations present in neutralization-resistant UK, South Africa or Brazil SARS-CoV-2 variants.”

SARS-CoV-2 spike induces cross-neutralizing antibodies to pre-emergent betaCoVs

SARSr-CoVs still pose a danger of future pandemics to human beings. The researchers, therefore, explored the ability of this vaccine to neutralize other viruses. Similar to the LNP-mRNA vaccines based on the prefusion stabilized spike or the RBD, the RBD-scNP also elicited potent cross-neutralizing antibodies against SARS-CoV and SARSr-bat CoVs (batCoV-WIV-1, and batCoV-SHC014).

The neutralization was most potent against SARS-CoV-2, however. The highest neutralizing antibody titers were observed with RBD-scNP and the least with the RBD-expressing LNP-mRNA vaccine. The high titers may indicate that durable immunity is achieved.  

The RBD-scNP vaccine showed cross-neutralizing activity against batCoV-RaTG13 and pangolin CoV GXP4L spike antigens, in addition to SARS-CoV and SARS-CoV-2. Notably, sera obtained following vaccination with this formulation failed to neutralize the seasonal human CoVs or MERS-CoV, probably because of the difference in RBD among these CoVs, which belong to different groups.

The similarity between the RBD-scNP and DH1047 in terms of cross-neutralizing profile shows that not only do antibodies induced by the former bind near the epitope bound by the latter, but they are not specific to SARS-CoV-2 RBD. In fact, they also block batCoV-SHC01.

Notably, only a third of COVID-19 patients produce antibodies that block DH1047, indicating it is a sub-immunodominant epitope. As such, the RBD-scNP vaccine targets this epitope rather than the immunodominant ACE2 blocking epitope.

Protection against productive infection

The RBD-scNP vaccine was also protective for vaccinated monkeys when challenged with the SARS-CoV-2 virus via the respiratory tract. In all but one of the vaccinated macaques, “RBD-scNP-induced immunity prevented virus replication, and likely provided sterilizing immunity, in the upper and lower respiratory tract.”

What are the implications?

The RBD-scNP platform induced the highest cross-neutralizing antibody titer for group 2b CoVs, and as such, may serve as the basis for a reasonably effective initial broadly neutralizing vaccine against this group – both now, and in the future, if the further zoonotic transmission should occur.

The study also showed that the use of both RBD-scNP and the LNP-spike mRNA vaccines, the latter resembling those which have been recently rolled out, is capable of inducing cross-neutralizing antibodies to the dominant D614G variant and the newer variants of SARS-CoV-2, but at lower titers.

The findings indicate the ability of the SARS-CoV-2 Spike to be included in an RBD-scNP or LNP-mRNA formulation to induce cross-neutralizing antibodies against several SARSr-CoVs. Thus, even the currently used vaccines are likely to prevent future pandemics if immunization is successfully achieved.

*Important Notice

bioRxiv 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:
  • Saunders, K. O. et al. (2021). SARS-CoV-2 vaccination induces neutralizing antibodies against pandemic and pre-emergent SARS-related coronaviruses in monkeys. bioRxiv preprint. doi: https://doi.org/10.1101/2021.02.17.431492. https://www.biorxiv.org/content/10.1101/2021.02.17.431492v1

Posted in: Medical Science News | Medical Research News | Disease/Infection News | Healthcare News

Tags: ACE2, Amino Acid, Angiotensin, Angiotensin-Converting Enzyme 2, Antibodies, Antibody, Aspartic Acid, binding affinity, Cell, Conjugation, Coronavirus, Coronavirus Disease COVID-19, Electron, Electron Microscopy, Enzyme, Glycine, heat, Helicobacter pylori, Immunization, MERS-CoV, Microscopy, Nanoparticle, Nanoparticles, Nucleoside, Pandemic, Pathogen, Protein, Pseudovirus, Receptor, Respiratory, SARS, SARS-CoV-2, Severe Acute Respiratory, Severe Acute Respiratory Syndrome, Spike Protein, Syndrome, Vaccine, Virus

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Written by

Dr. Liji Thomas

Dr. Liji Thomas is an OB-GYN, who graduated from the Government Medical College, University of Calicut, Kerala, in 2001. Liji practiced as a full-time consultant in obstetrics/gynecology in a private hospital for a few years following her graduation. She has counseled hundreds of patients facing issues from pregnancy-related problems and infertility, and has been in charge of over 2,000 deliveries, striving always to achieve a normal delivery rather than operative.

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Substrain of SARS-CoV-2 variant in UK may resist antibody neutralization

Researchers at the Polish Academy of Sciences in Warsaw have identified a substrain of the recently emerged B.1.1.7 variant of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) that may confer resistance to antibody neutralization.

The SARS-CoV-2 virus is the agent responsible for the coronavirus disease 2019 (COVID-19) pandemic that has now claimed the lives of more than 2.35 million people.

The substrain of the B.1.1.7 variant of concern (VOC) contains mutations that have previously been shown to compromise the binding of neutralizing antibodies.

Tomasz Lipniacki and colleagues say mutations in the receptor-binding domain (RBD) of the viral spike protein are of particular concern, especially those identified in the receptor-binding motif (RBM).

The spike protein is the surface structure the virus uses to bind to and infect cells by attaching to the host cell receptor angiotensin-converting enzyme 2 (ACE2).

The researchers say the mutations could eventually lead to “immune escape” strains that can reinfect convalescent individuals and reduce the efficacy of the vaccines currently being used in mass immunization efforts.

“Such mutants may hinder the efficiency of existing vaccines and expand in response to the increasing after‐infection or vaccine‐induced seroprevalence,” writes the team.

A pre-print version of the research paper is available on the medRxiv* server, while the article undergoes peer review.

Study: L18F substrain of SARS-CoV-2 VOC-202012/01 is rapidly spreading in England. Image Credit: NIAID

The B.1.1.7 variant has spread rapidly since mid-October 2020

The B.1.1.7 variant has rapidly spread since mid-October 2020, and by January 2021, it constituted about 80% of all SARS-CoV-2 genomes sequenced in England.

The high transmissibility of this VOC may be expressed in terms of its replicative advantage – defined as the ratio of the VOC reproduction number to that of non-VOC strains.

To date, a number of studies have estimated the replicative advantage as lying somewhere between 1.47 and 2.24.

As is the case with all viral strains, the B.1.1.7 variant will continue to mutate, and given its significant replicative advantage, any mutations acquired are likely to spread globally.

“As this strain will likely spread globally towards fixation, it is important to monitor its molecular evolution,” say the researchers.

What did the current study involve?

Using the Global Initiative on Sharing Avian Influenza Data (GISAID) database, Lipniacki and colleagues estimated growth rates of the mutations that B.1.1.7 has acquired.

This revealed a substrain with an L18F substitution in the spike protein that is rapidly growing in the UK.

This leucine‐to‐phenylalanine substitution in residue 18 was first reported to have occurred in a VOC strain genome collected on December 4th, 2020.

As of February 5th, 2021, as many as 850 spikes L18F VOC genomes had been reported in England.

Based on data collected between December 7th, 2020 and January 17th, 2021, the researchers showed that the L18F substrain had spread exponentially in England. They estimated a replicative advantage of 1.70 relative to the remaining B.1.1.7 substrains.

RBM mutations are particularly concerning

Lipniacki and colleagues say that mutations in the RBD of the spike protein are particularly concerning, especially substitutions E484K and S494P found in the RBM.

Importantly, the LI8F mutation has expanded in the South African variant 501Y.V2 that contains the spike mutations E484K and N501Y. Studies have suggested that E484K may compromise the binding of class 2 neutralizing antibodies, while the A501V mutation compromises the binding of class 1 antibodies.

Furthermore, in a 2021 study published in Science, the S494P substitution was characterized as an escape mutation, along with six other escape residues in the RBM that included F490.

In the current study, Lipniacki and colleagues also identified F490S as a potential escape mutation.

What do the authors advise?

“These mutations may potentially lead to immune escape mutants, resulting in reinfection of convalescent individuals and lowering efficacy of current vaccines,” warn the researchers.

“Propagation of such mutations is facilitated by high replicative advantage of the VOC strain and potential selection due to the increasing number of convalescent or immunized individuals,” they add.

Correspondingly, a study published in 2021 showed that L18F substitution compromises the binding of neutralizing antibodies, suggesting that the replicative advantage of L18F mutants may be partly associated with the ability to infect seroprevalent individuals (who already have anti-SARS-CoV-2 antibodies).

“In turn, propagation of mutations in escape residues (L18, E484, F490S, or S494) on the VOC strain suggests an increasing selection pressure resulting from the growth of the seroprevalent fraction of the population of England,” says Lipniacki and colleagues.

“This trend can be enhanced by the ongoing English vaccination program, in which the relatively large time span between the first and second dose can be a contributing factor,” concludes the team.

*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:
  • Lipniacki T, et al. L18F substrain of SARS-CoV-2 VOC-202012/01 is rapidly spreading in England. medRxiv, 2021. doi: https://doi.org/10.1101/2021.02.07.21251262, https://www.medrxiv.org/content/10.1101/2021.02.07.21251262v1

Posted in: Medical Research News | Disease/Infection News

Tags: ACE2, Angiotensin, Angiotensin-Converting Enzyme 2, Antibodies, Antibody, Avian Influenza, Cell, Coronavirus, Coronavirus Disease COVID-19, Efficacy, Enzyme, Evolution, Genome, Immunization, Influenza, Leucine, Mutation, Pandemic, Phenylalanine, Propagation, Protein, Receptor, Reproduction, Research, Respiratory, SARS, SARS-CoV-2, Severe Acute Respiratory, Severe Acute Respiratory Syndrome, Spike Protein, Syndrome, Vaccine, Virus

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Written by

Sally Robertson

Sally has a Bachelor's Degree in Biomedical Sciences (B.Sc.). She is a specialist in reviewing and summarising the latest findings across all areas of medicine covered in major, high-impact, world-leading international medical journals, international press conferences and bulletins from governmental agencies and regulatory bodies. At News-Medical, Sally generates daily news features, life science articles and interview coverage.

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SARS-CoV-2 antibodies detected six months after infection

SARS-CoV-2 antibodies detected six months after infection

(HealthDay)—For many individuals, severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) antispike antibodies remain for at least six months after infection, according to a report published by the U.K. Biobank.

To determine the extent of past infection with SARS-CoV-2 in different population subgroups, the U.K. Biobank collected blood samples from about 20,200 individuals on a monthly basis for six months.

A total of 18,893 individuals (93.5 percent) provided at least one sample that was successfully assayed between May 27 and Dec. 4, 2020. The researchers found that 9 percent of individuals had at least one sample that was seropositive for SARS-CoV-2 antispike antibodies during the study period. Seroprevalence differed significantly by age, ethnicity, geographic region, and socioeconomic status. Overall, 1,264 individuals were seropositive in month 1. The duration of seropositivity was assessed among those who were seropositive in month 1 and had reported symptoms or had a positive polymerase chain reaction test. Of these 705 participants, 12.2 percent sero-reverted within six months of symptom onset. Only five participants (<1 percent) sero-reverted within three months.

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What is Autoimmunity?

The term autoimmunity refers to a failure of the body’s immune system to recognize its own cells and tissues as “self”. Instead, immune responses are launched against these cells and tissues as if they were foreign or invading bodies.

The immune system exists in almost all complex life forms. The main functions of the immune system are to defend the body from germs and other foreign invaders. The immune system is composed of special cells and organs that together mount an immune attack against foreign chemicals, viruses, bacteria, or pollen.

A cell called a B lymphocyte develops into a plasma cell, which produces antibodies to fight off such invaders. Any such substance that triggers an immune response in this way is referred to as an antigen. For the immune system to function appropriately, it must be able to distinguish cells that are “self” form substances that are non-self or foreign. Autoimmunity refers to when the immune system fails to do this and instead produces antibodies that are directed towards the body’s own tissues. These are called auto-antibodies.

Some of the main examples of autoimmune disorders include diabetes mellitus type 1 (IDDM), systemic lupus erythematosus (SLE), Hashimoto's thyroiditis, Graves' disease of the thyroid, Sjögren's syndrome, Churg-Strauss Syndrome, Coeliac disease, rheumatoid arthritis (RA), and idiopathic thrombocytopenic purpura.

In previous years, a misconception existed that the body was not capable of recognising “self” antigens. At the start of the twentieth century, Paul Ehrlich described the concept of “horror autotoxicus,” which referred to how a normal body would not create an immune attack against its own tissue. Therefore, such responses were considered abnormal and a sign of disease. Now, however, we know that autoimmunity is a key part of the vertebrate immune system, but that it is usually kept in check by an immunological tolerance of antigens that are “self.”

Sources

  1. www.oucom.ohiou.edu/…/Lecture17_autoimmunity2xpg.pdf
  2. www.kau.edu.sa/…/…_7_AUTOIMMUNITY_AND_AUTOIMMUNE_DISEASE_Part1.pdf
  3. omicsonline.org/…r-basis-in-todays-perspective-2155-9899.S10-003.pdf
  4. www.st-andrews.ac.uk/~gdk/bl4217web/Gp2RefList/autoimmune_path.pdf
  5. http://www.kims.org.kw/bulletin/Issues/Issue9/Autoimmunity_I.PDF

Further Reading

  • All Autoimmunity Content
  • Low-Level Autoimmunity
  • Autoimmunity Immunological Tolerance
  • Autoimmunity Genetic Factors
  • Autoimmunity Sex
More…

Last Updated: Aug 23, 2018

Written by

Dr. Ananya Mandal

Dr. Ananya Mandal is a doctor by profession, lecturer by vocation and a medical writer by passion. She specialized in Clinical Pharmacology after her bachelor's (MBBS). For her, health communication is not just writing complicated reviews for professionals but making medical knowledge understandable and available to the general public as well.

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