Cell-mediated cytotoxicity against measles virus in SSPE. I. Enhancement by antibody.

In patients with subacute sclerosing panencephalitis (SSPE) virus persistency has been explained by a blocking factor of specific cell-mediated immunity in SSPE serum and cerebrospinal fluid (CSF). In the present study the effect of SSPE serum and CSF on cell-mediated cytotoxicity against 51Cr-labeled allogenic measles virus-infected target cells was tested. Pretreatment of SSPE peripheral lymphoid cells by serum or CSF neither blocked nor increased measles-specific cytotoxicity when cells were subsequently tested in FCS containing tissue culture medium. However, killing activity was always enhanced after pretreatment of target cells or direct addition of serum or CSF to the cytotoxic assay. Enhancement was also observed with non-SSPE-derived measles antibodies. The effect was dependent on measles antibody concentrations. These results suggest that antibody-dependent killing by K cells is intact in patients with SSPE. It is possible that virus-infected brain cells are protected from an immune attack in vivo by antibody-induced antigenic modulation.