SARS-CoV-2 is a new virus and unfortunately research into immune-memory cannot be based uniquely on predictions as to the immune response observed a short time after recovery. It’s necessary to evaluate responses of the immune-memory several months after infection so as to verify the organism’s reactivity. This requires the study of different components including the antibodies, the LB, the LT CD4+ and the CD8+ cells, which may have immune-memory reactions at different kinetic rates, in other words, may have variable reaction speeds.
To study this, 185 individuals infected by the virus were observed. They were aged between 19 and 81 and had widely varied levels of the illness (asymptomatic or with mild, moderate or severe symptoms). Blood samples were taken up to 8 months after infection so as to study the antibodies and the immune-memory cells in circulation.
Concerning the antibody response, it was observed that 90% of patients studied possessed neutralizing antibodies at 6 to 8 months after infection. The IgG antibodies targeting the virus’ spike protein (a surface protein) remained active for some time, with a slight reduction after 6 months. The antibodies targeting the receptor-binding domain (RBD, domain situated on the spike protein) and the nucleocapsid protein largely follow the same kinetic pattern as those targeted against the spike protein. Nevertheless, the amplitude of the antibody response is extremely variable depending on the individual, and this is a central characteristic of immune-memory when faced with this virus.
The LB memory response appears robust and durable. The LB memory responses specifically targeting the spike protein, the RBD protein and the nucleocapsid are broadly similar: the quantity of LB increases during the first five post-infection months.