FIG. 6.

MV-LAP expression affects both MHC-I expression and CTL lysis. (A) MV-LAP induces MHC-I down-regulation of Malme 3 M cells. Malme 3 M cells were either mock infected (solid line) or infected with either wild-type MV (dashed line) or an MV-ΔLAP mutant virus (bold line). Twenty-four hours postinfection, MHC-I surface expression was quantified using an anti-HLA-A, -B, and -C MAb. M1 represents the MHC-I-positive cell population. (B) Cytotoxic activity is abolished after MV infection. The lytic activity of the A2Kb huTyr CTL line was tested against mock-infected (diamonds), MV-infected (circles), and MV-ΔLAP-infected (triangles) Malme 3 M cells at the indicated effector/target cell ratios. Specific lysis was dramatically decreased after MV infection and almost unchanged after MV-ΔLAP infection.