A whole-blood lymphoproliferation assay for measuring cellular immunity against herpes viruses

A whole blood test system was established to study cell-mediated immunity to cytomegalovirus (CMV) and herpes simplex virus (HSV) in a large number of healthy blood donors. Cellular immunity was measured by the in vitro proliferative response (LP) of peripheral lymphocytes. These responded vigorously to several mitogens. Lymphocytes of most individuals responded to HSV, but only a limited number were reactive towards CMV. In parallel, antibodies against CMV and HSV were measured by an ELISA technique. For HSV, good correlation was observed between serological and lymphocyte proliferation results. For CMV, no clear correlation was obtained, only 21 of 40 donors positive in the antibody test being positive in the LP test. The majority of seronegatives were negative in the LP test. Use of virions purified by sucrose gradient centrifugation, or an additional strain of CMV (strain Davis) did not increase the number of donors positive in the LP test. One explanation might be that individuals possessing antibodies against CMV as measured by ELISA but no capacity to react in the LP test had suffered from a CMV infection a long time before, and now showed waning cellular immunity, but antibody still detectable. Use of the whole blood technique on 108 individuals showed that this very simple test works well with various mitogens and at least some antigens.