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

Abstract

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-SARS-CoV-2 antibodies may provide a pattern for estimating infection degrees and observing the development of the epidemic. In this study, we aimed to investigate the persistence of antibody against the SARS-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 positive for the presence of SARS-CoV-2 RNA, using qualitative RT-PCR. An ELISA was used to 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 hundred 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.

Stable IgG-antibody levels in patients with mild SARS-CoV-2 infection

“…This is in agreement with other studies showing a sustained antibody response, e.g. 6-9 months after infection (4,5,7,(22)(23)(24). Neutralizing antibodies are evidently important for protection against disease (25), and protection over longer time-periods depends on the evolution of memory B cells (26).…”

ChAdOx1 nCoV-19 Immunogenicity and Immunological Response Following COVID-19 Infection in Patients Receiving Maintenance Hemodialysis

“…The vaccinated group had a lower absolute mean anti-spike IgG level than the recovered group, as well as a lower seroconversion rate. The higher anti-spike IgG level in the recovered group could be attributed to the recovered group's eligibility criteria, which comprised only symptomatic and hospitalized COVID-19 patients with a higher humoral immune response than asymptomatic COVID-19 patients [62]. Although there was a significant difference in age between the vaccinated and recovered groups, there was evidence that, in the general population, age was not associated with IgG response to ChA-dOx1 nCoV-19 [37].…”

An Update on Protective Effectiveness of Immune Responses After Recovery From COVID-19

“…There was also a significant positive correlation between the patients’ age and their anti-S IgG antibody levels, showing a greater concentration in older adults compared to younger adults. Patients were seropositive 100 days after the disease onset when the latest measurement occurred ( 38 ). Robust humoral immunity correlates with the spike-specific antibodies, memory B cells, and circulating follicular helper T cells (cTFH), steadily induced after SARS-CoV-2 infection and associated with plasma neutralizing activity ( 39 ).…”