CD40LG and COVID-19: Although the magnitude of neutralizing antibody (NAb) responses correlated with COVID-19 severity, the NAb titers including IgM and IgA were subjected to rapid decline in most discharged COVID-19 patients, while virus might rebound in discharged patients who experienced low levels of prolonged viral replication in the gastrointestinal tract (Hu et al., 2020; Long et al., 2020).