Cellular immune responses in mice challenged with an amyocarditic variant of coxsackievirus B3

An amyocarditic variant of a temperature‐sensitive (ts) mutant derived from the parent myocarditic variant Coxsackievirus B3 (CVB3m) was studied in a murine model of CVB3m‐induced myocarditis to assess virus‐induced antigens and their possible role in the disease process. Amyocarditic variant ts5R induced a heart tissue antigen(s), extractable by hypertonic KCI, which inhibited migration of peritoneal exudate cells from CVB3‐inoculated myocarditic mice in an agarose droplet cell‐migration‐inhibition assay. The ts5R variant was amyocarditic at inoculum doses of 103 to 108 plaque‐forming units per mouse, but in cyclophosphamide‐immunosuppressed mice, ts5R induced myocarditis. Viable ts5R served as a vaccine and protected mice against CVB3m‐induced myocarditis. Murine neonatal skin fibroblasts (MNSF) infected with either virus served as in vitro targets and were lysed by splenic cytotoxic T lymphocytes from mice inoculated with either virus variant. ts5R and CVB3m replicated to similar titers in murine neonatal skin fibroblasts (MNSF) at 24 hr postinoculation (pi), but differences in titers were found by 72 hr pi. Levels of natural killer cell activities in spleens of ts5R‐inoculated mice were slightly lower than in spleens of CVB3m‐inoculated mice at 7 days pi. The data suggest that viral induction of new antigens on target cells and viral induction of specific cytotoxic T lymphocytes that recognize these antigenic changes do not always result in induction of myocarditis.