Use of the 51Cr Release Test to Demonstrate Patterns of Antibody Response in Humans to Herpesvirus Types 1 and 2

Antibodies to the surface antigens of cells infected with herpesvirus types 1 or 2 were assayed by the 51 Cr release test. Absorption of sera with 10 7 unlabeled cells infected with herpesvirus type 1 removed all cytolytic activity to herpesvirus type 1 51 Cr-labeled cells; however, cytolytic activity to 51 Cr-labeled cells infected with herpesvirus type 2 remained in some of the absorbed sera. Sucrose gradient separation of the immunoglobulins revealed that the cytolytic activity was in the IgM fractions in all eight sera collected 3 to 28 days after the onset of illness caused by herpesvirus type 2 and also in the IgG fractions in all six sera obtained 11 to 28 days after the onset of illness. Sera collected 8 months or more after the infection were found to contain cytolytic activity only in the IgG-containing fractions. Cytolytic antibody activity of 20% specific 51 Cr release or greater from labeled cells infected with herpesvirus type 2 after absorption with unlabeled type 1 infected cells was found in the convalescent sera of most patients who had no neutralizing antibody to type 1 in their acute phase sera. However, among persons with neutralizing antibodies in their acute phase sera, cytolytic activity to the type 2 cells was absent or at low levels in their convalescent sera after absorption with type 1 unlabeled cells. The data suggest that antibodies reacting only to herpesvirus type 2 infected cells can be detected by the 51 Cr release test and that the quantity of the antibody present depends upon whether or not the person had been infected with herpesvirus type 1 before infection with herpesvirus type 2.