Cytomegalovirus (CMV) Phosphoprotein 65 Makes a Large Contribution to Shaping the T Cell Repertoire in CMV‐Exposed Individuals

Abstract

Antigen-specific, cytokine flow cytometry was used to analyze the prevalence and frequency of CD4 and CD8 memory T cells specific for the abundantly expressed cytomegalovirus (CMV) phosphoprotein 65 (pp65) in healthy CMV IgG-seropositive individuals. Stimulation of peripheral blood mononuclear cells with peptide pools and individual peptides derived from the pp65 amino acid sequence in 40 donors revealed that 63% of donors had a detectable CD4 T cell response and that 83% of donors had a detectable CD8 T cell response against this protein. The overall frequencies of T cells directed against pp65 were analyzed for 20 donors by stimulation with peptide pools covering the complete pp65 protein and were as high as 2 in 1000 and 9 in 1000 (median) peripheral blood CD4 and CD8 T cells, respectively. In addition, a comparison between CD4 responses to a CMV lysate containing various CMV proteins and pp65-specific responses in 9 donors indicated that pp65 was a dominant target of the CMV-specific CD4 T cell response in some, but not all, donors. Several new T cell epitopes were identified.

Expression and function of NKG2D in CD4+ T cells specific for human cytomegalovirus

“…By switching the use of costimulatory molecules, CD4 + cells primed by professional antigen-presenting cells (APC) might efficiently respond to other HLA class II + virus-infected cell types. Though most studies have focused on the response of CD8 + CTL to HCMV antigens [48], CD4 + T cells specific for epitopes of viral proteins such as pp65 and IE1 have been identified [49][50][51]. Recently, the gB HCMV glycoprotein was shown to be processed via the endosomal pathway by non-professional APC, being efficiently presented by HLA class II molecules to CD4 + T cells [52].…”

Selection of CMV-specific CD8+ and CD4+ T cells by mini-EBV-transformed B cell lines

“…As previously described [19], the 138 peptides of this library were used to compose two sets of 12 peptide subpools each in a cross-matrix orientation, which enabled the pp65 subsequence recognized by the T cell clone to be define using only 24 individual reactions. Fig.…”

“…7 A shows some typical results. For example, clone 14 from donor F46 only reacted with "vertical" pools 7 and 8 and "horizontal" pool 16, making it likely that the epitope recognized by this clone was to be found in the overlap region of two neighboring peptides, one present in pools 7 and 16, the other in pools 8 and 16; this overlap region has the sequence NQWKEPDVYYT, previously suspected of containing an HLA-B*3501-restricted epitope [19]. This region contains the nonameric sequence NQWKEPDVY carrying the typical C-terminal tyrosine "anchor residue".…”

Delivery of functional DNA and messenger RNA to mammalian phagocytic cells by recombinant yeast

“…However, it is long known that in most individuals up to 95% of all CTL-recognizing CMV-infected cells are pp65 specific. 34,35 We observed a higher number of activated CD8 T cells after yeast delivery of nucleic acids than in control reactions containing proteins from a virus lysate. This is worth noting as the immune response induced by pp65 in vitro is known to be similar to that of whole viral antigen considering T cell proliferation, as well as interleukin 2 and interferon production, [35][36][37] again underlining the efficacy of the yeast system.…”