Cytotoxic lymphocytes generated in vivo with acute measles virus infection.

We studied the generation of cytotoxic lymphocytes in adults during an outbreak of acute measles virus infection. Nine patients were studied determining in particular whether virus-specific cytotoxic T lymphocytes could be directly detected in peripheral blood during this acute infection. The cytotoxicity of PBL was assayed against measles virus-infected and uninfected phytohemagglutinin-induced blast cells of matched and mismatched HLA, A, B, and C types, in a standard 4-h 51Cr release assay. There was greater cytotoxicity against measles virus-infected than uninfected target cells in at least one sample from every patient. In 4 patients this preferential lysis of virus infected cells was greater (a difference of more than 10% virus-specific lysis) against HLA-matched than mismatched targets. This preference for HLA A and B matched infected target cells was also clearly seen when the effector PBL were depleted of FC receptor bearing cells. The other 5 subjects exhibited no evidence of preferential lysis of HLA-matched measles virus-infected cells. All 9 patients limited the spread of measles virus infection and recovered equally from the acute infection. These studies provide some evidence to suggest that MHC-restricted virus-specific CTL are detectable in human peripheral blood during acute measles virus infection, albeit only with low frequency, but are not necessarily associated with recovery from disease.