SARS-CoV-2 infection induces sustained humoral immune responses in convalescent patients following symptomatic COVID-19

Abstract

Long-term antibody responses and neutralizing activities following SARS-CoV-2 infections have not yet been elucidated. We quantified immunoglobulin M (IgM) and G (IgG) antibodies recognizing the SARS-CoV-2 receptor-binding domain (RBD) of the spike (S) or the nucleocapsid (N) protein, and neutralizing antibodies during a period of six months following COVID-19 disease onset in 349 symptomatic COVID-19 patients, which were among the first world-wide being infected. The positivity rate and magnitude of IgM-S and IgG-N responses increased rapidly. High levels of IgM-S/N and IgG-S/N at 2-3 weeks after disease onset were associated with virus control and IgG-S titers correlated closely with the capacity to neutralize SARS-CoV-2. While specific IgM-S/N became undetectable 12 weeks after disease onset in most patients, IgG-S/N titers showed an intermediate contraction phase, but stabilized at relatively high levels over the six months observation period. At late time points the positivity rates for binding and neutralizing SARS-CoV-2-specific antibodies was still over 70%. Taken together, our data indicate sustained humoral immunity in recovered patients who suffer from symptomatic COVID-19, suggesting prolonged immunity.

Longitudinal observation and decline of neutralizing antibody responses in the three months following SARS-CoV-2 infection in humans

“…The magnitude of the following decline in neutralizing antibody titres reported here is similar to that observed in several newly reported pre-prints 12,13,20,31,[34][35][36][37][38][39] . In these studies, similar to our observations, those who generated a high neutralizing antibody titre still had high neutralizing antibody titres regardless of the initial decline 12,13,31,35,39 and, for those with lower disease severity, two studies reported 7/34 (ref.…”

“…31 ) individuals with a decline to undetectable neutralizing antibodies (ID 50 < 20 or ID 50 < 50, respectively) at the last timepoint studied. In contrast, several studies report a sustained antibody response in the first 3 months after SARS-CoV-2 infection, but these studies report changes in binding antibodies only 34,37,38 . Although binding titres to S glycoprotein and RBD correlate with neutralizing antibody titres, this difference in antibody measurement may account for the differences in kinetics described.…”

Longevity of seropositivity and neutralizing titers among SARS-CoV-2 infected individuals after 4 months from baseline: a population-based study in the province of Trento

“…These results appear to be consistent with those obtained for other human coronaviruses, such as NL63, 229E, OC43, and HKU1, showing a rapid decay of antibodies directed against the nucleocapsid protein 16 . However, other studies showed different results, with high IgG levels after several months [7][8][9]17 . The inconsistency in the results of previous studies could be explained by differences in the study populations (i.e., patients with mild vs moderate or severe disease) or in the use of different methods (i.e., detection of antibodies directed against the nucleocapsid vs whole spike or the receptor binding domain of the spike) 4 .…”

Early Humoral Response Correlates with Disease Severity and Outcomes in COVID-19 Patients

“…Analysis of SARS-CoV-2 specific antibodies response in a cohort of COVID-19 patients in China showed a potential overall correlation between total antibodies (IgG and IgM) against the RBD and disease severity [30]. Interestingly, a recent study showed an opposite trend of increased IgG antibodies in milder cases compared to more severe COVID-19 patients [31]. However, this study focused on the correlation between antibodies levels and viral RNA shedding in patients and not necessarily disease severity.…”