Durability of the humoral immune response in recovered COVID-19 patients

Abstract EN

Background: The immunological factors involved in protection against the disease caused by SARS-CoV-2 are insufficiently defined and understood.

However, previous knowledge pertaining to the related SARS virus and other human coronaviruses may prove useful.

Population-based serosurveys measuring anti- ARS-CoV-2 antibodies may provide a pattern for estimating infection degrees and observing the devel-opment of the epidemic.

In this study, we aimed to investigate the persistence of antibody against theSARS-CoV-2 in recovered patients in Al Madinah region of Saudi Arabia.

Materials and methods: A total of 150 recovered COVID-19 patients participated in this study.

All the patients tested po sitive for the presence of SARS-CoV-2 RNA, using qualitative RT-PCR.

An ELISA was usedto measure anti-Spike (S) IgG antibodies in serum samples and screen for their persistence at various time points post-infection.

Results: The patients were categorized as asymptomatic (27.3%), mild (28%) and moderate (44.7%) according to the disease severity.

Amongst them, 35.3% were females (n = 53) and 64.7% were males (n = 97).

Significant anti-S IgG antibody levels were observed among the different groups, with the patients in moderate group exhibiting the highest levels followed by the mild group; while the lowest levels were detected among the asymptomatic.

There was a significant positive correlation between the patients’ age and anti-S IgG antibody concentrations (Pearson r = 0.45; p < 0.001).

Conclusion: Our findings provide a solid evidence to support the use of an anti-S IgG ELISA as a diagnostic tool to indicate SARS-CoV-2 infection.

IgG seropositivity was sustained in recovered patients up to a hun-dred days’ post-infection, the latest time point for antibody measurement in our study.

Ours is the first report in Saudi Arabia to investigate the durability of humoral immune response in recovered COVID-19 patients.