Impaired human leukocyte antigen-restricted measles virus-specific cytotoxic T-cell response in subacute sclerosing panencephalitis.

The capacity of peripheral blood lymphocytes to proliferate in response to measles virus and to generate measles virus-specific cytotoxic T lymphocytes (CTL) was examined in 4 patients with subacute sclerosing panencephalitis (SSPE). The lymphoproliferative response to measles virus was obtainable in the 4 SSPE patients. In contrast, the CTL response to measles virus was reduced in 3 of the 4 SSPE patients. This defect appeared to be in the generation of the measles virus-specific CTLs, since measles virus-infected target cells from the patients could be lysed by human leukocyte antigen-matched peripheral blood lymphocytes from healthy individuals. The SSPE patients with reduced measles virus CTL response had a normal ability to generate mumps virus, influenza virus, or alloantigen-specific CTLs. The lysis of measles virus-infected targets that was observed with these SSPE patients could be reduced by depleting the effectors of natural killer cells or by performing cold target blocking with K562 cells, indicating that the lysis of the measles virus-infected targets was probably mediated by natural killer cells. These results demonstrate a reduction in the cell-mediated immune response to measles virus as measured by the generation of measles virus-specific CTLs in 3 of the 4 SSPE patients studied. This defect could relate to the persistence of measles virus in these patients.