Ad5-nCoV boosted vaccine and reinfection-induced memory T/B cell responses and humoral immunity to SARS-CoV-2: based on two prospective cohorts

Here, we regularly followed SARS-CoV-2 infected cohorts to investigate the combined effects of neutralizing antibodies (NAbs) and B and T cell profiles during the convalescent period. Ten participants infected with SARS-CoV-2 in December 2022 were selected to assess the effects of an inhaled adenovirus type 5 vectored COVID-19 vaccine (Ad5-nCoV) booster on B cells and humoral immunity. To evaluate T cell responses, eight primary and 20 reinfection participants were included. Blood samples from all 38 participants were collected at 1-, 2-, and 6-months post-infection. The assays included single B cell technology, activation-induced marker (AIM) assays, and pseudovirus neutralization. In the first cohort, eighteen monoclonal antibodies (mAbs) with neutralizing activity from memory B cells (MBC) against SARS-CoV-2 mutants were obtained by high throughput single-B-cell cloning method, which lasted from 1- month to 6- month post infection. The overall number of mAbs from MBC in the inhaled Ad5-nCoV-boosted immunization group was higher than that in the non-boosted immunization group at 2-, and 6-months post-infection. In the second cohort, circulating T follicular helper cells (cTfh) and AIM