Expansion of the HSV-2-specific T cell repertoire in skin after immunotherapeutic HSV-2 vaccine

Abstract

ABSTRACTThe skin at the site of HSV-2 reactivation is enriched for HSV-2 specific T cells. To evaluate whether an immunotherapeutic vaccine could elicit skin-based memory T cells we studied skin biopsies and HSV-2-reactive CD4+ T cells from peripheral blood mononuclear cells (PBMCs) by T-cell receptor (TCR) sequencing before and after vaccination with a replication-incompetent whole virus HSV-2 vaccine candidate (HSV529). The representation of HSV-2-reactive CD4+ T cell sequences from PBMCs increased from a median of 0.03% (range 0-0.09%) to 0.6% (range 0-1.3%) of the total skin TCR repertoire after the first vaccine dose. We found sustained expansion after vaccination in unique, skin-based T-cell clonotypes that were not detected in HSV-2-reactive CD4+ T cells isolated from PBMCs. While detection of skin clonotypes in the blood was related to abundance in the skin it was not related to expansion after vaccination. In one participant a switch in immunodominance was observed after vaccination with the emergence of a newly dominant TCRa/b pair in skin that was not detected in blood. We confirmed that the newly dominant clonotype was derived from an HSV-specific CD4+ T cell by creation of a synthetic TCR in a Jurkat-based cell line with a NR4A1-mNeonGreen reporter system. Our data indicate that the skin in areas of HSV-2 reactivation possesses an oligoclonal TCR repertoire that is distinct from the circulation with prominent clonotypes infrequently detected in the circulation by standard methods. Defining the influence of therapeutic vaccination on the HSV-2-specific TCR repertoire requires tissue-based evaluation.