In vitro stimulation of sensitized lymphocytes by herpes simplex virus and vaccinia virus.

Splenic lymphocytes from rabbits immunized with herpes simplex virus (HSV) were incubated in vitro with ultraviolet light-inactivated HSV, and the degree of lymphocyte transformation was determined by measurement of the incorporation of [(3)H]thymidine into acid-insoluble material. Lymphocytes from immunized rabbits were stimulated as much as 30-fold, whereas lymphocytes from control rabbits were unaffected. Lymphocyte sensitization occurred within 3 days after immunization; sensitized lymphocytes could still be detected 120 days after immunization. The antigenicity of the ultraviolet light-inactivated crude virus pool was found to reside primarily in the virion. Infectious virus, in comparison with inactivated virus, produced less lymphocyte stimulation. Studies on the interaction of the humoral and cellular immune responses showed that incubation of anti-HSV antibody with HSV antigens did not reduce the capacity of the viral antigens to stimulate sensitized lymphocytes. Other experiments revealed that lymphocytes from both the spleen and peripheral blood of animals immunized with vaccinia virus could be stimulated by vaccinia, but not by HSV. Conversely, lymphocytes from animals immunized with HSV could not be stimulated by vaccinia. The transformation of sensitized lymphocytes by viral antigens appears to be a simple, highly specific, and quantitative in vitro technique for the study of the cellular immune response to viral infections.