CD40LG and COVID-19: In individuals recovering from COVID-19, adaptive immunity to SARS-CoV-2 is primarily mediated by CD4+ cells with a repertoire of T cell receptors specific for the S epitope, resulting in robust neutralization IgG, IgM, and IgA antibodies producing trimers of the ectodomain of RBD and S1 [104,105] while individuals exhibit b-cell monoclonal antibody neutralizing activities, which bind ACE2 to RDB and the NTD of S, indicating that the two S epitopes are highly immunogenic at the apex of S [106,107].