Scientists investigate kinetics of naturally induced anti-SARS-CoV-2 antibodies in Kenyan population

In a recent study posted on medrex sib*Preprint server, Researchers investigated the breadth and longevity of immunity induced by natural severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) exposure in the Kenyan population.

Background

Triggered by SARS-CoV-2 infection Neutralizing antibody (nAbs), the best-established correlate of protection against all infectious agents. These nAbs provide protection against viruses through several mechanisms including neutralization, opsonization, and antibody-dependent cytotoxicity.

SARS-CoV-2-induced nAbs elicit strong immunoglobulin G (IgG), IgM, and IgA antibody responses. However, only a few have a neutralizing function. Over 90% of neutralizing nAbs target the receptor binding domain (RBD) of the SARS-CoV-2 spike (S) protein.

Previous studies examining general populations in high-income countries (such as European countries) have shown that anti-SARS-CoV-2 nAbs can be short-lived. Some of her COVID-19 patients remain seronegative despite being SARS-CoV-2 positive. These observations raise the possibility that there are population differences in people’s ability to generate and maintain anti-SARS-CoV-2 antibodies.

Sub-Saharan countries such as Kenya have low coverage of the COVID-19 vaccine. As of September 2022, nearly 70% of the Kenyan population had not been vaccinated against his SARS-CoV-2, and there is a unique need to understand natural acquired immunity to SARS-CoV-2. We provide the environment.

Comparing anti-SARS-CoV-2 immune responses between patients with different geographic locations and clinical phenotypes may help find potential correlations of COVID-19 disease severity. Furthermore, it may help determine the presence and longevity of antibody-neutralizing function in people who have acquired immunity through natural infection rather than vaccination.

About research

In the present study, researchers determined the kinetics of naturally acquired anti-SARS-CoV-2 neutralizing antibodies in a cohort of Kenyan patients with varying degrees of COVID-19 severity. They followed these patients for 6 months after diagnosis of COVID-19 and assessed the titers and subsequent decline of anti-SARS-CoV-2 binding and neutralizing antibodies.

The team sampled recruited patients at baseline, called Day 0. Blood samples were then collected on days 7, 14, 28, and 180 (6 months) of positive COVID-19 testing. In addition, we categorized her COVID-19 symptoms in all patients as asymptomatic, mild, moderate, and severe according to National Institutes of Health (NIH) guidelines. The team used an in-house enzyme-linked immunosorbent assay (ELISA) targeting full-length trimeric S to measure the levels of her IgG antibodies in patient-provided serum samples.

Survey results

From 309 patients, researchers collected 585 blood samples at five study time points. His 70% of the study cohort were male patients, and most patients belonged to the mild and severe groups (121/309 and 141/309, respectively).

In participants recruited before April 2021, the neutralizing potency of the antibodies increased through day 28 and then declined through day 180. Days 28 and 180. Infectious nAbs were more potent against the Wuhan-Hu1 strain than later epidemic SARS-CoV-2 VOCs. Results also showed a strong correlation between increased antibody binding levels, neutralizing potency, and disease severity.

Only a few studies have determined the kinetics of anti-SARS-CoV-2 antibodies in sub-Saharan African populations over longer periods. For example, a South African study quantified her IgG antibodies in a COVID-19 patient weekly over 3 months and showed a rapid decline in anti-SARS-CoV-2 RBD IgA and IgM nAbs.

However, the results of the current study demonstrate the importance of longer periods of follow-up in longitudinal studies confirming anti-SARS-CoV-2 antibody dynamics after infection.

Neutralizing anti-SARS-CoV-2 antibodies declined 3-fold by 6 months of follow-up. A small number of patients had increased binding and neutralizing antibodies 28 days after COVID-19 diagnosis without vaccination. Other studies have shown the occurrence of SARS-CoV-2 reinfection.

Conclusion

Research results have shown that anti-SARS-CoV-2 nAbs are short-lived, whereas other antibodies can be long-lasting. Antibodies function through cellular cytotoxicity and complement deposition mechanisms to mediate viral clearance. However, such a role remains unexplored in SARS-CoV-2.

Investigating these mechanisms is of great importance as the COVID-19 vaccine uses them for viral clearance that contributes more to sterile immunity. Understanding the scale and functional aspects of antibody dynamics will help develop the next generation of his COVID-19 vaccines that can provide much-needed long-term protection.

Finally, even in sub-Saharan African populations, vaccine boosters help maintain high levels of neutralizing antibodies that peak after acute infection. Coordinated efforts to do so could help expand and extend current levels of naturally acquired anti-SARS-CoV-2 immunity.

*Important Notices

medRxiv publishes non-peer-reviewed, preliminary scientific reports and should not be considered conclusive, to guide clinical practice/health-related actions, or to be treated as established information .