Immunogenicity of wild and attenuated varicella-zoster virus strains in rhesus monkeys.

Thirty susceptible rhesus monkeys were inoculated with cell-free varicella-zoster virus strain OKA or strain KMcC. Both wild and attenuated strains were used. No clinical signs characteristic of human varicella were seen in any of the animals. Virus was not isolated from throat swabs, blood, or cerebrospinal fluid. Antibodies were measured by an enhanced plaque neutralization test. The wild and attenuated OKA strains produced comparable levels of antibodies for 3 months after inoculation. Attenuated KMcC strains produced lower titers than the wild strain. On rechallenge 3 months after primary inoculation animals boostered with the attenuated OKA strain developed significantly higher antibody titers than animals receiving the wild strain. Animals primed and challenged with the attenuated KMcC strains showed significantly lower antibody titers than animals which received the wild strain. The results indicate that the immunogenicity of attenuated OKA and KMcC strains in rhesus monkeys parallels the experience obtained with these strains in humans.