High-Level Cellular and Humoral Immune Responses in Guinea Pigs Immunized Intradermally with a Heat-Inactivated Varicella-Zoster Virus Vaccine

The threat of varicella and herpes zoster in immunocompromised individuals necessitates the development of a safe and effective varicella-zoster virus (VZV) vaccine. The immune responses of guinea pigs to the intradermal (i.d.) or subcutaneous (s.c.) administration of a heat-inactivated or live VZV vaccine were investigated. Relative to nonimmunized animals, a single 399-PFU dose of vaccine induced nonsignificant increases in gamma interferon (IFN-γ), granzyme B, and perforin mRNA expression in the splenocytes of all groups, while two i.d. administrations of the inactivated vaccine increased IFN-γ mRNA expression significantly (P < 0.005). A single 1,995-PFU dose significantly increased the expression of IFN-γ mRNA in the groups receiving the vaccine either i.d. (P < 0.005) or s.c. (P < 0.05), that of granzyme B mRNA in the groups immunized i.d. with the inactivated (P < 0.005) or live (P < 0.005) vaccine, and that of perforin mRNA in the animals that received the inactivated vaccine i.d. (P < 0.005). Importantly, increases in the expression of IFN-γ (P = 0.025), granzyme B (P = 0.004), and perforin (P > 0.05) mRNAs were observed in the animals immunized i.d. with 1,995 PFU of inactivated vaccine relative to those immunized s.c. with the same dose. The proportion of animals expressing IFN-γ mRNA mirrored the proportion expressing IFN-γ protein (correlation coefficient of 0.88). VZV glycoprotein-specific and virus-neutralizing antibodies were produced with no significant intergroup differences. A booster i.d. administration of the 399-PFU dose of heat-inactivated vaccine enhanced the antibody responses. These results demonstrate that i.d. administration of an inactivated VZV vaccine can be an efficient mode of immunization against VZV.