Cellular immune responses to herpes simplex virus type 1 in recurrent herpes labialis: In vitro blastogenesis and cytotoxicity to infected cell lines

Cellular immunity to herpes simplex virus type 1 (HSV-1) in 12 volunteers with recurrent herpes labialis was evaluated by means of two microassays. In the blastogenesis assay, lymphocytes were incubated with tissue culture cells persistently infected with HSV-1. Uninfected cells were used as controls, and a blastogenic index was calculated. The mean blastogenic index (x SD) for subjects with recurrent herpes labialis was 26.9 (x 8.3); the mean blastogenic index (x SD) in control donors with antibody to HSV-1 was 13.4 (x 7.2). The difference between these values was statistically significant (t = 4.154; P < 0.001). In the cytotoxicity assay, cells of the same persistently infected line were used as target cells, and release of 51Cr from these cells or from control cells served as the index of lymphocyte reactivity. Specific immune release attributable to HSV-1 averaged 3.7% (x 1.8%) in subjects with recurrent herpes labialis, compared with 23.1% (x 9.8%) in controls (t = 6.135; P < 0.001). These data suggest a dissociation between mechanisms of cellular immunity, with enhanced lymphocyte blastogenesis but decreased cytotoxicity. Recurrent herpes labialis may thus result from subtle cellular immune deficiency involving at least one of the efferent mechanisms.