Subviral herpes simplex vaccine.

An experimental split herpes simplex type 1 (HSV-1) vaccine, virtually free of virus DNA, was prepared from a Nonidet P-40--extract of HSV-1 infected human diploid cells. For determining the contents of neutralizing antigens in these preparations a chromium release inhibition test (CRIT) was developed. The vaccine was gradually shown to be capable of inducing neutralization antibody formation in various animals and conferring protection against intraperitoneal challenge with either type 1 or type 2 viruses in mice. Its administration to mice also markedly restricted the establishment of latent infection following the virus infection. There was an excellent correlation between the immunogenicity of the vaccine and the content of neutralizing antigens as determined by CRIT.