Defining The HSV-Specific CD8+ T Cell Repertoire In C57BL/6 Mice

Abstract

Purpose: : Herpes simplex virus type 1 (HSV-1) glycoprotein B (gB) contains a strongly immunodominant CD8⁺ T cell eptiope (gB_498-505) that is recognized by 50% of both the CD8⁺ effector T cells in acutely infected trigeminal ganglia (TG) and the CD8⁺ memory T cells in latently infected TG of C57BL/6 mice. The goal of this study was to identify the subdominant epitopes recognized by 50% of the HSV-specific CD8⁺ T cell repertoire.

Methods: : The entire HSV-1 proteome (GI 9629378) was scanned for peptide sequences predicted to have a high affinity binding capacity for the MHC class I molecules H-2 K^b or H-2 D^b. For each MHC allele, the 188 peptides with the highest median ranks, corresponding to the top 0.5% scoring peptides, were selected for screening. B6WT3 fibroblast targets were pulsed with peptide and used to stimulate dispersed TG or spleen cells obtained 8 days after HSV-1 corneal infection. Responding CD8⁺ T cells were quantified by intracellular staining for IFN-γ and TNF-α followed by flow cytometry analysis.

Results: : Of 376 predicted HSV-1 CD8⁺ T cell epitopes, 19 (gB_498-505 and 18 subdominant epitopes) stimulated CD8⁺ T cells in the spleens and TG of HSV-1 acutely infected mice. These 19 epitopes identified virtually all CD8⁺ T cells in the infected TG and represented all or the vast majority of the HSV-specific CD8⁺ TCR repertoire. A similar frequency of epitope specific CD8⁺ T cells was observed in the TG and among HSV-specific CD8⁺ T cells in the spleen. Only 11 of approximately 84 HSV-1 proteins are recognized by CD8⁺ T cells and most (~80%) are expressed before viral DNA synthesis. Neither the immunodominance of gB_498-505 nor the dominance hierarchy of the subdominant epitopes is due solely to MHC or TCR affinity.

Conclusions: : We conclude that the vast majority of CD8⁺ T cells in HSV-1 acutely infected TG are HSV-specific, that HSV-1 β and γ1 proteins that are expressed before viral DNA synthesis are favored targets of CD8⁺ T cells, and that dominance within the TCR repertoire is likely due to the frequency or expansion and survival characteristics of CD8⁺ T cell precursors.

Keywords: herpes simplex virus • cytokines/chemokines • immunomodulation/immunoregulation