Abstract
Objective: Many studies have explored the protective mechanism from infection of SARS-CoV-2. However, studies of couples living together in which one individual experienced symptomatic Confirmed Positive (CP) while the other consistently tested negative for infection (Household contact; HC) are scarce. Herein, we investigated humoral and T-cell responses in pre- and post-infection samples from CP and HC.
Methods: 52 CP and 44 HC individuals were recruited. Humoral responses were measured from plasma. Antigen-specific T cells against spike, non-spike, and common cold coronaviruses (CCC) were measured using an AIM+ICS from PBMCs.
Results: Humoral and T responses were similar between CP and HC before infection. In longitudinal analyses, except for the spike T responses, those responses were significantly increased after infection in CP but not in HC. One-third of the HC pairs were also associated with increased non-spike reactivity besides displaying increased spike reactivity in post-infection. 41.7% of HC pairs showed high pre-existing or CCC-specific T cells in pre-infection. No obvious pattern was found in the remaining HC pairs.
Conclusions: Measurement of antibody and T cell responses before infection does not predict protective mechanisms in household discordant pairs. Despite testing negative for COVID-19, some HC might have experienced asymptomatic/abortive infections and the other HC might have been protected due to the pre-existing or cross-reactive T cells.
