VACCINATION AGAINST TICK-BORNE ENCEPHALITIS-VIRUS, A FLAVIVIRUS, PREVENTS DISEASE BUT NOT INFECTION, ALTHOUGH VIREMIA IS UNDETECTABLE

By adoptive transfer of sera or immunoglobulin preparations, vaccine-i nduced protection against TBEV has been demonstrated to be mediated by antibodies to the surface protein of TBEV, glycoprotein E. Neverthele ss, the mechanism of vaccine-induced protection against TBEV remains u nclear. Protection by E antibodies without in vitro neutralization was shown by one group, whereas others found a correlation between protec tion in vivo and neutralization in vitro. Here, the authors confirm in a mouse model of tick-borne encephalitis (TBE) that immunization with the whole-killed virus vaccine protects mice against a subsequent cha llenge with a highly lethal dose of virus, i.e. 250 LD50 doses. Vaccin e-induced immunity, however, is not completely neutralizing as demonst rated by the development of immune responses to a non-structural virus protein absent from the vaccine, yet expressed in the course of virus replication. Antibodies specific for the non-structural protein 1 (NS 1) and cytotoxic T-cells could be detected after, but not prior to, vi rus challenge of vaccinated animals, establishing that protection by t his highly effective vaccine is not equivalent with complete neutraliz ation of the challenge virus. (C) 1998 Elsevier Science Ltd. All right s reserved.