A comparison of gene transfer and antigen-loaded dendritic cells for the generation of CD4⁺ and CD8⁺ cytomegalovirus-specific T cells in HLA-A2⁺ and HLA-A2^- donors

Dendritic cells have been used effectively to select for human cytomegalovirus (CMV)-specific T cells for immunotherapy applications. The ability to process and present relevant major histocompatibility complex class I and II peptides to T cells makes them ideal for selecting CD4⁺ and CD8⁺ T cells regardless of HLA tissue type. This study compared the generation of CMV-specific T cells by using dendritic cells loaded with either CMV pp65_(495-503) peptide or CMV lysate or transduced with adenovirus encoding the pp65 gene (Ad5pp65GFP) for the generation of CD4⁺ and CD8⁺ CMV-specific T cells in HLA-A2⁺ and HLA-A2^- donors. In HLA-A2⁺ donors, CD8⁺ tetramer⁺ T cells increased with all antigens but were greatest in peptide- and Ad5pp65GFP-stimulated T cells. The CD4⁺/CD8⁺ ratio in the stimulated T-cell cultures proved to be dependent on the antigen used. CMV lysate-stimulated cells were primarily CD4⁺, whereas peptide- and Ad5pp65GFP-stimulated cultures were mostly CD8⁺. Analysis of cells from lysate-stimulated or gene-transduced-stimulated cultures showed expansion of CMV-specific CD4⁺ T cells, indicating that major histocompatibility complex class II peptides were present in both antigens. Furthermore, CMV-specific T cells were generated from HLA-A2^- donors by using Ad5pp65GFP transduction or CMV lysate stimulation and were able to recognize a pp65 peptide restricted to the HLA-B35 allele. These data indicate that either CMV lysate or adenovirus encoding CMV antigenic genes may be useful for the generation of both CD4⁺ and CD8⁺ CMV-specific T cells in donors irrespective of HLA tissue type and may be applicable to clinical immunotherapy.