Detectability of IgM antibodies against TBE virus after natural infection and after vaccination.

IgM antibodies against tick-borne encephalitis (TBE) virus were investigated by means of a three-layer ELISA (antigen bound to the solid phase) and a four-layer ELISA (anti-mu-serum bound to the solid phase) after natural infection as well as after vaccination. In general, the four-layer ELISA detected IgM antibodies more often and for a longer period of time than the three-layer test. In some patients, IgM antibodies were detected for as long as eight months after the disease with the four-layer test but for only six months with the three-layer test. In addition, after the second TBE vaccination, IgM antibodies were found for as long as eight months in 24 sera which were taken within eight months after the second vaccination. Five were positive in the three-layer ELISA and 16 in the four-layer test. IgM antibodies were never detected in specimens taken later than ten months after the second and third vaccination. The results are of diagnostic importance in infections of the CNS which are not caused by TBE virus and which have been preceded by a possibly silent TBE virus infection or by a TBE vaccination.