Kinetics of naturally induced binding and neutralising anti-SARS-CoV-2 antibody levels and potencies among SARS-CoV-2 infected Kenyans with diverse grades of COVID-19 severity: an observational study
Kimotho J., Sein Y., Sayed S., Shah R., Mwai K., Saleh M., Wanjiku P., Mwacharo J., Nyagwange J., Karanja H., Kutima B., Gitonga JN., Mugo D., Karanu A., Moranga L., Oluoch V., Shah J., Mutiso J., Mburu A., Nneka Z., Betti P., Usyu Mutinda W., Issak Abdi A., Bejon P., Isabella Ochola-Oyier L., M.Warimwe G., Nduati EW., M. Ndungu F.
Background: Given the low levels of coronavirus disease 2019 (COVID-19) vaccine coverage in sub-Saharan Africa (sSA), despite high levels of natural severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) exposures, strategies for extending the breadth and longevity of naturally acquired immunity are warranted. Designing such strategies will require a good understanding of natural immunity. Methods: We measured whole-spike immunoglobulin G (IgG) and spike-receptor binding domain (RBD) total immunoglobulins (Igs) on 585 plasma samples collected longitudinally over five successive time points within six months of COVID-19 diagnosis in 309 COVID-19 patients. We measured antibody-neutralising potency against the wild-type (Wuhan) SARS-CoV-2 pseudovirus in a subset of 51 patients over three successive time points. Binding and neutralising antibody levels and potencies were then tested for correlations with COVID-19 severities. Results: Rates of seroconversion increased from day 0 (day of PCR testing) to day 180 (six months) (63.6% to 100 %) and (69.3 % to 97%) for anti-spike-IgG and anti-spike-RBD binding Igs, respectively. Levels of these binding antibodies peaked at day 28 (p<0.0001) and were subsequently maintained for six months without significant decay (p>0.99). Similarly, antibody-neutralising potencies peaked at day 28 (p<0.0001) but declined by three-fold, six months after COVID-19 diagnosis (p<0.0001). Binding antibody levels were highly correlated with neutralising antibody potencies at all the time points analysed (r>0.6, p<0.0001). Levels and potencies of binding and neutralising antibodies increased with disease severity. Conclusions: Most COVID-19 patients generated SARS-CoV-2 specific binding antibodies that remained stable in the first six months of infection. However, the respective neutralising antibodies decayed three-fold by month-six of COVID-19 diagnosis suggesting that they are short-lived, consistent with what has been observed elsewhere in the world. Thus, regular vaccination boosters are required to sustain the high levels of anti-SARS-CoV-2 naturally acquired neutralising antibody potencies in our population.