Lopandić et al. produced and purified recombinant protein M, which can specifically bind to antibodies from the sera of COVID-19 convalescents, and in M-based ELISA for the detection of IgG and IgM, the sensitivities were 96% and 93%, respectively.229 In general, all these antigens showed comparable sensitivities when assayed. Here, CD40LG is linked to COVID-19.