A Colorimetric Neutralization Test for Herpes Simplex, with Observations on Neutralizing and Complement-Fixing Antibody Levels in Human Sera

Abstract

Discussion and Summary The colorimetric neutralization test for herpes simplex described in this report is considerably easier to conduct than neutralization tests in mice or embryonated eggs, and lends itself to large-scale studies. Also, the constant virusvarying serum technique, widely regarded as more sensitive than the constant serum-varying virus method for detecting differences in levels of neutralizing antibody, is utilized. As a tool for epidemiologic and diagnostic purposes, the neutralization test was found comparable to the complement fixation test in its ability to demonstrate 4-fold or greater titer rises. It would appear that either the complement fixation or colorimetric neutralization test would be adequate for diagnosis of primary herpetic infections, and that little would be gained diagnostically by the use of both tests except in instances where equivocal results were obtained with one test. Only 2 of 31 4-fold or greater rises in antibody titer were detected by the neutralization test, but not the complement fixation test, and only 3 of the 31 antibody rises were detected by the complement fixation test, but not the neutralization test. Although the neutralizing antibody titers tended to be somewhat higher than the complement-fixing antibody titers, they both increased at approximately the same rate in cases of primary herpetic infections. This is in contrast to the antibody response in many other viral diseases in which neutralizing antibodies appear long before complement-fixing antibodies, and may even reach their maximal titer by the time of onset of the illness, e.g., poliomyelitis (19). The neutralizing antibody titers detected by the colorimetric method showed good correlation with the complement-fixing antibody titers for the same sera (r = 0.82). This correlation between complement-fixing and neutralizing antibody titers was noted for individuals in all age groups studied, and it would appear, on the basis of the limited amount of data available, that production of both types of antibody is stimulated by recurrent herpetic infections, or that complement-fixing antibody persists for as long after primary infections as does neutralizing antibody.