Protectivity of herpes simplex virus antigens: studies in mice on the adjuvant effect of PICLC and on the dependence of protection on T cell competence.

The efficacy of a herpes simplex virus type 1 (HSV-1) envelope antigen (EAG) preparation against HSV infection was studied in T cell competent and T cell deficient mice. Immuno-competent mice were successfully protected against herpes simplex virus type 1 (HSV-1) or type 2 (HSV-2) infection when immunized 2 weeks prior to this infection with a heat-inactivated whole virus preparation or a HSV-1 envelope antigen (HSV-1 EAG) preparation. Since HSV-1 EAG was considerably less effective than the whole virus preparation, a poly.riboinosinic-poly.ribocytidylic acid complex with poly-L-lysine and carboxymethylcellulose (PICLC) was used as adjuvant. Immunization with HSV-1 EAG plus PICLC resulted in a pronounced increase of this protection rate as compared with that obtained after immunization solely with HSV-1 EAG. PICLC alone, however, offered no protection when given 2 weeks before challenge. In T cell deficient nu/nu mice no protection was achieved with HSV-1 EAG while their T cell competent, heterozygous littermates were protected. From these results it may be concluded that T cell competence is a prerequisite for establishing a protective immunity against HSV infection after immunization with HSV-1 EAG.