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

Abstract

A panel of herpes simplex virus type 1 (HSV-1)-specific, CD8 ؉ , major histocompatibility complex class I (H-2K b )-restricted cytotoxic T-lymphocyte (CTL) clones was derived from HSV-1-immunized C57BL/6 (H-2 b ) mice in order to identify the HSV-1 CTL recognition epitope(s) which confers type specificity. HSV-1 ؋ 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 inhibitor of viral DNA synthesis and an ICP6 deletion mutant, the large subunit of ribonucleotide reductase (ICP6, RR1) was identified as a target protein for these type-specific CTL. Potential CTL recognition epitopes 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 829) with 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 primary C57BL/6 cells, was recognized by the HSV-1 RR1-specific CTL clones. These results indicate that an early HSV protein with enzymatic activity provides a target for HSV-specific CTL and that type specificity is dictated largely by a single amino acid.

Neonatal CD8+ T cells are slow to develop into lytic effectors after HSV infection in vivo

“…Thus, the limited neonatal response to gB 498–505 , the immunodominant CTL determinant to HSV, could have been associated with an enhanced response to subdominant determinants. Here, we show that this was not the case, as the neonatal CTL response to the subdominant epitope to HSV‐2, RR1 829–836 35, 36, was similarly reduced. Numerous studies have defined the memory CD8 + T cell response to viruses in the newborn 10–16, 18, including a disabled infectious single‐cycle HSV‐1 strain 42, but few studies 10, 15, 26, 27, like ours, have examined the kinetics of the primary CTL response in the neonatal period after viral infection.…”

“…To test if the delayed neonatal CD8 + T cell response to the immunodominant determinant reflected the response to non‐dominant epitopes, we measured the in vivo CTL responses to the major subdominant CTL epitope to HSV ribonucleotide reductase (HSV‐2 RR1 829–836 ) 35 at day 5 post HSV infection, i.e. the time of the peak adult response.…”

CTL response compensation for the loss of an immunodominant class I‐restricted HSV‐1 determinant

“…Finally, we examined if the compensation observed in Figure 4 was a product of the enhancement of the response against a known HSV subdominant determinant, RR 822-829 . 5,27 We therefore measured the size of the RR 822-829 -specific CTL response following infection with the recombinant viruses, stimulating splenocytes from infected animals with either whole virus or the minimal peptides: RR 822-829 or gB 498-505 . Following infection with HSVrgB, an almost equivalent-sized population responded to the gB 498-505 peptide as when stimulated by whole virus, emphasizing the dominance of the gB 498-505 determinant in the wild-type HSV response (Fig.…”

“…HSV-1 provides an excellent model to address this issue, as greater than 70% of the entire CTL response to HSV-1 in C57BL/6 mice is directed against a single glycoprotein B-derived determinant (gB 498-505 ), 5 and a sizable fraction of the remaining T cells are shown in this study to be directed to a previously identified subdominant determinant derived from the HSV ribonucleotide reductase (RR 822-829 ). 5,27 We have exploited this defined but simple determinant hierarchy to examine whether removing the major determinant causes a gross reduction in the CTL response or alternatively, drives the emergence of alternate T-cell populations. virus, which has a 550 amino acid deletion in the UL27 (gB) gene that includes the immunodominant gB 498-505 peptide, was obtained from Dr Stanley Person 28 and propagated on the D6 cell line (UL27 transformed) in the presence of G418.…”

The impact of interspecies recombination on human herpes simplex virus evolution and host immune recognition

“…The NR version of this epitope contains two amino acid changes relative to the CR1 and CR2 genotypes. Functional experiments have demonstrated that the HSV-1 specific CD8+ T-cells that recognize the CR1/CR2 version of this epitope do not recognize the NR version (Salvucci et al, 1995).…”