ADJUVANT CARRIER ACTIVITY OF INACTIVATED TICK-BORNE ENCEPHALITIS-VIRUS/

Virus-like or virus-derived particles have been reported to increase t he immunogenicity of foreign antigens. In this study formaldehyde-inac tivated tick-borne encephalitis virus (TBEV), a potent immunogen in hu mans, was tested for possible adjuvant/carrier function. The results o f our study revealed that substantial antibody titers against very low doses of tetanus toxoid could be obtained when mice were immunized wi th the antigen covalently coupled to TBEV (using N-succinimidyl-3-(2-p yridyldithio)propionate, a heterobifunctional, cleavable crosslinker c ontaining a disulfide bridge). In contrast, only moderate anti-tetanus toxoid titers were induced by immunizations with a simple mixture of low dose tetanus toxoid and TBEV or when the disulfide bridge of the c rosslinker used to couple tetanus toxoid to TBEV was cleaved prior to immunization. The antibody response to TBEV, on the other hand, was no t influenced by its linkage to tetanus toxoid. Comparable anti-TBEV ti ters were obtained following immunization of the animals with either t he TBEV-tetanus toxoid conjugate or the mixture of tetanus toxoid and TBEV. Prior application of a TBEV vaccine did not change the antibody response against tetanus toxoid and thus carrier-induced epitopic supp ression could be ruled out. The abovementioned adjuvant/carrier proper ties of TBEV might make it a suitable candidate for use in bi- or mult ivalent vaccines containing weak immunogens. (C) 1998 Elsevier Science Ltd. All rights reserved.