POLYMORPHISM WITHIN THE HERPES-SIMPLEX VIRUS (HSV) RIBONUCLEOTIDE REDUCTASE LARGE SUBUNIT (ICP6) CONFERS TYPE SPECIFICITY FOR RECOGNITION BY HSV TYPE 1-SPECIFIC CYTOTOXIC T-LYMPHOCYTES

A panel of herpes simplex virus type 1 (HSV-1)-specific, CD8(+), major histocompatibility complex class I (H-2K(b))-restricted cytotoxic T-l ymphocyte (CTL) clones was derived from HSV-l-immunized C57BL/6 (H-2(b )) mice in order to identify the HSV-1 CTL recognition epitope(s) whic h confers type specificity. HSV-1 x HSV-2 intertypic recombinants were used to narrow the region encoding potential CTL recognition epitopes to within 0.51 to 0.58 map units of the HSV-1 genome. Using an inhibi tor of viral DNA synthesis and an ICP6 deletion mutant, the large subu nit of ribonucleotide reductase (ICP6, RR1) was identified as a target protein for these type-specific CTL. Potential CTL recognition epitop es within RR1 were located on the basis of the peptide motif predicted to bind to the MHC class I H-2K(b) molecule. A peptide corresponding to residues 822 to 829 of RR1 was shown to confer susceptibility on H- 2K(b)-expressing target cells to lysis by the type 1-specific CTL. On the basis of a comparison of the HSV-1 RR1 epitope (residues 822 to 82 9),vith the homologous sequence of HSV-2 RR1 (residues 828 to 836) and by the use of amino acid substitutions within synthetic peptides, we identified HSV-1 residue 828 as being largely responsible for the type specificity exhibited by HSV-1-specific CTL. This HSV-1 RR1 epitope, when expressed in recombinant simian virus 40 large T antigen in prima ry C57BL/6 cells, was recognized by the HSV-1 RR1-specific CTL clones. These results indicate that an early HSV protein with enzymatic activ ity provides a target for HSV-specific CTL and that type specificity i s dictated largely by a single amino acid.