Changes of Humoral Immunity Response in SARS-CoV-2 Convalescent Patients over 8 months

ABSTRACT

Many countries around the world have all seen a sharp rise in COVID-19 cases as the second wave since the beginning of October 2020. Decline of antibodies response to severe acute respiratory syndrome coronavirus (SARS-CoV-2) that was reported exclusively in the early month increases the risk of reinfection for convalescent individuals. There is a current need to follow the maintenance of special antibodies against SARS-CoV-2. Here, we reported changes of antibodies against SARS-CoV-2 in convalescent patients over 8 months. Antibodies of all 20 participants targeting SARS-CoV-2 spike receptor binding-domain (RBD) had decreased from a mean OD450 value 1.78 to 0.38 over 8 months. The neutralizing antibody (NAb) titers decreased from the mean ID50 value 836 to 170. The NAb titers were significantly correlated with IgG level during 8 months (P<0.001). Furthermore, while RBD-specific IgG existence of 25% (5/20) convalescent plasma was undetectable, the NAb titers of 15% (3/20) convalescent plasma decreased below the threshold. In addition, compared to wild-type SARS-CoV-2 (S-D614), lower titers of neutralizing antibodies against its G614 variant were shown at 8 months after symptom onset. This study has important implications when considering antibody protection against SARS-CoV-2 reinfection.