CD40LG and infection: Although, similar results were obtained in all the samples from each phase analyzed by commercial ELISA and TBEV NS1-based ELISA assays, 7 samples from the convalescent phase of TBEV infection were IgM negative while they were considered positive by commercial assays, presumably because all these samples were collected from two months after onset of symptoms, i.e. when IgM antibodies decrease to undetectable levels.