Serologic Responses to Herpes Simplex Virus in Rabbits: Complement-requiring Neutralizing, Conventional Neutralizing, and Passive Hemagglutinating Antibodies

Abstract

Five strains of herpes simplex virus type 1 (HSV-1), two strains of type 2 (HSV-2), and the Brod. strain were injected into rabbits. Type-specific and heterologous antibody responses were determined. Homotypic complement-requiring neutralizing (CRN) antibody appeared after immunizations with HSV-1. A ratio of CRN to conventional neutralizing (N) antibody ⩾ 4 in one blood sample indicated a current antigenic stimulus. Significant CRN:N ratios (⩾4) usually indicated a primary immunologic response. Homotypic CRN:N ratios were significant seven, 14, and 21 days after immunization with HSV-1. CRN antibodies were IgM at seven and 14 days but became IgG at 21 days. Lower titers of heterologous HSV-neutralizing antibodies were also present. After immunizations with the HSV-2 and Brod. strains, homologous N antibody did not necessarily appear within 21 days, and CRN antibody developed in response to strain MS (HSV-2) but not to E304 (HSV-2 prototype) or Brod. Simultaneously, heterologous CRN and N antibody to HSV-1 appeared. With strains of both types, but especially with those of HSV-2, passive hemagglutinating (PHA) antibody appeared earlier and in higher titer than N antibody. The kinetics of appearance of PHA, CRN, and N antibodies suggest that PHA is not a measure of N antibody. The Brod. strain was neutralized poorly by hyperimmune rabbit antiserum to HSV-1 or HSV-2. However, hyperimmune antiserum to Brod. neutralized both HSV-1 and prototype HSV-2 but not B virus of monkeys. Antiserum to Brod. neutralized strain E304 better than HSV-1.