Generation of CMV-specific T lymphocytes using protein-spanning pools of pp65-derived overlapping pentadecapeptides for adoptive immunotherapy.

Cell-mediated immunity is essential for control of human cytomegalovirus (HCMV) infection. We used a pool of 138 synthetic overlapping pentadecapeptides overspanning the entire pp65 protein to generate polyclonal CMV-specific T-cell lines from 12 CMV-seropositive donors inheriting different HLA genotypes. Autologous monocyte-derived dendritic cells (DCs) pulsed with this complete pool consistently induced highly specific T cells that selectively recognized 1-3 pentadecapeptides identified by secondary responses to a mapping grid of pentadecapeptide subpools with single overlaps. Responses against peptide-loaded targets sharing single HLA class I or II alleles identified the restricting HLA alleles. HLA-A*0201+ donors consistently responded to pentadecapeptides containing HLA-A*0201-binding epitope(aa495-503)NLVPMVATV. T-cell lines from other donors contained high frequencies of CD4 and/or CD8 T cells selectively reactive against peptides presented by other HLA alleles, including both known epitopes such as (aa341-350)QYDPVAALF (HLA-A*2402) as well as unreported epitopes such as (aa267-275)HERNGFTVL (HLA-B*4001 and B*4002) and (aa513-523)FFWDANDIYRI (HLA-DRB1*1301). These T cells consistently lysed CMV-infected target cells. Thus, this approach fosters expansion and selection of HLA-restricted CMV-pp65-reactive T-cell lines of high specificity that also lyse CMV-infected targets, and from a functional and regulatory perspective, may have advantages for generating virus-specific T cells for adoptive immunotherapy.