Cell surface expression of MHC molecules in glioma cells infected with herpes simplex virus type-1

9L glioma cells consistently expressed major histocompatibility complex (MHC) class I but not class II molecules. Herpes simplex type-1 virus (HSV-1) infection significantly reduced the expression of MHC I on the cell surface. Recombinant interferons could enhance the cell-surface expression of MHC I but had no effect on MHC II. This enhancement was partially inhibited by HSV-1 infection. HSV-1 mutants with deletions in ICP4, ICP6, ICP27, ICP47 and UL41 genes do not affect the infection induced inhibition, suggest that a different mechanism may be employed in the inhibition of cell-surface expression of MHC molecules.