Isolation of a Herpes Simplex Virus-Specific Antigenic Fraction Which Stimulates the Production of Neutralizing Antibody

Infection of mammalian cells with herpes simplex virus (HSV) results in the production of a number of virus-induced soluble antigens. Immunodiffusion analyses of the soluble antigen mixture (SAM) obtained from HSV-infected KB or BHK cells revealed at least six well-defined immunoprecipitin bands. Calcium phosphate chromatography (Brushite) was employed to separate one immunoprecipitin (designated CP-1) from the remaining viral and host antigens. We conclude that CP-1 is a viral-specific antigen because (i) specific antiserum, which had been repeatedly absorbed with uninfected cell extracts or serum components, still retained the capacity to react in gel diffusion with CP-1 antigen; (ii) anti-CP-1 serum reacted in gel diffusion with SAM, yielding one precipitin band in identity with the band formed against human gamma globulin; (iii) the CP-1 fraction stimulated the production of HSV-neutralizing antibody of high capacity. The last observation suggests that fraction CP-1 contains a biologically active structural component of the virus which is associated with the envelope. The CP-1 immunoprecipitin was separated from SAM by an alternative method by using a cyanogen bromide-linked immunosorbent prepared from anti-CP-1 gamma globulin. The observation that the CP-1 antigen isolated from the immunosorbent effectively blocked serum-neutralizing activity provided further evidence that neutralizing antibody was directed against CP-1. Acrylamide gel electrophoresis and immunological experiments suggest that the CP-1 antigen is in part a glycoprotein. The finding that CP-1 contains only one antigenic component of the virus will permit future biological studies to be made with a monoprecipitin antiserum. In addition, the techniques described in this paper represent initial steps in the purification of HSV antigens.