Serologic Classification of Herpes Simplex Viruses

Roizman et al. in a recent publication (1) raised a provocative issue concerning the serologic classification of herpes simplex viruses. We agree with these investigators that herpes simplex viruses should be placed in one serologic group, and offer additional arguments in favor of this proposal. Our comments are based on studies that were carried out concerning serologic relationships between intra- and interspecies herpesvirus variants as determined by 50% neutralization endpoints. Employing antisera prepared in rabbits by intravenous (i.v.) immunization, it was noted that the 7S and 19S antibodies fractionated from early (7 day) and late (7 week) immune sera differed in their neutralizing properties against the immunizing or isologous herpesvirus strain (2). These differences were reflected in the ability of these four antibody fractions to neutralize virus alone and to sensitize virus for subsequent neutralization by complement (C) or anti-γ globulin. Later studies (3-6) showed that these four antibody fractions also differed in their ability to differentiate between crossreacting herpesvirus strains. Of particular interest was the observation that the late 19S antibodies, in contrast to the other three antibody fractions, showed a high degree of specificity for the immunizing or isologous herpesvirus strain. In the case of herpes simplex "types" 1 and 2, for example, the late 19S antibodies demonstrated differences by the 50% neutralization endpoint which approached the 20-fold level accepted for differentiating poliovirus serotypes (6). More recent studies (unpublished) have demonstrated a similar efficacy for late 19S antibodies in classifying fresh isolates of "types" 1 and 2 strains. In contrast, the early 7S, early 19S and late 7S antibodies showed only two- to fourfold differences between "types" 1 and 2 strains by the 50% neutralization endpoint.