CHMP5 and COVID-19–associated multisystem inflammatory syndrome in children: In addition, study [29] reported elevated levels of IgG antibody titers against SRBD and full-length S, and IgA antibody titers against full-length S (but not S-RBD) in patients with MISC compared to patients with severe COVID-19 (majority of whom had undetectable levels of the spike or nucleocapsid proteins of IgG antibodies).