Human CD8+ cytotoxic T cell responses to adenovirus capsid proteins

Abstract

Adenoviruses (Ads) cause fatal disease in allogeneic stem cell transplant recipients, but there is no established therapy. Ad-specific CD8+ T cells were detected in PBMC from healthy adults at a mean frequency of 77 per 10(5) CD8+ T cells (range 8-260) by interferon-gamma ELISPOT and cytokine flow cytometry assays. CD8+ T cell lines from 7 of 7 donors exhibited MHC-class-I-restricted killing of targets expressing the capsid protein hexon. In contrast, cytotoxicity against the capsid proteins fiber and penton base was weaker or not detected. Two HLA-A2-restricted hexon epitopes and one HLA-B-restricted epitope were identified, all of which are adjacent to or overlap an HLA-DP4-restricted epitope in the highly conserved C-terminus. Thus, hexon is the immunodominant T cell target among capsid proteins and contains multiple C-terminal epitopes conserved among serotypes. These data support evaluation of donor lymphocyte infusions for treatment of Ad disease post-transplant.

Generation of cytotoxic T-cell lines using overlapping pentadecapeptides derived from conserved regions of the adenovirus hexon protein

“…The well-characterized DPB1*0401-restricted epitope TLLYVLFEV (H913-921) is contained within this region, along with minimally four additional peptides recognized by Ad-specific T cells ( Supplementary Fig. S2) (Tang et al, 2006). We confirmed that SP98/SP99, each containing the TLLYVLFEV sequence, were recognized in the context of both DPB1*0401 and DPB1*0402 and further identified epitopes restricted by DQB*0402 and Cw*0702 within H906-928.…”

“…We confirmed that SP98/SP99, each containing the TLLYVLFEV sequence, were recognized in the context of both DPB1*0401 and DPB1*0402 and further identified epitopes restricted by DQB*0402 and Cw*0702 within H906-928. Indeed, multiple investigators have reported hexon-specific responses within this region after natural infection (Tang et al, 2004(Tang et al, , 2006, after priming with intact Ad (Olive et al, 2002) or a modified Ad vector , and using 30-mer hexon peptides . Predominantly CD4 + T cells respond to Ad in healthy adults and paediatric patients post-HPCT, which contrasts with the largely CD8 + T-cell response to most viral pathogens (Appay et al, 2008;Yewdell & Bennink, 1992).…”

“…CD4 + T cells recognize exogenous viral proteins degraded into peptides in endosomal vesicles, where they bind to class II antigens; therefore, presentation is not affected by E3-19K (Germain & Hendrix, 1991). Ex vivo generation of Ad-specific CD8 + T-cell responses by intact virus requires the use of E3 deletion mutants that allow for presentation of Ad peptides by class I molecules (Tang et al, 2006). In these studies, only targets infected with mutant virus or pretreated with IFN-c to upregulate class I expression were recognized.…”

“…This was complicated by the fact that the minimal sequence recognized was not defined definitively in all studies. We used the likely minimal sequence of peptides characterized in this study, as shown in Table 1 in bold, underlined and italic, with peptides to the level identified by other groups Heemskerk et al, 2003Heemskerk et al, , 2006Leen et al, 2004bOnion et al, 2007;Tang et al, 2006). Because we used 15-mers, compared with 20-or 30-mers used by others for peptide identification, the sequences containing the minimal peptides could be narrowed in several cases.…”

“…Shared epitopes that confer protective immunity across Ad serotypes are relatively uncharacterized. Cross-reactive T-cell responses among Ad serotypes can be generated ex vivo by priming with Ad-infected fibroblasts (Olive et al, 2002;Tang et al, 2006), Ad lysates (Feuchtinger et al, 2006) or a modified Ad vector (Leen et al, 2004a). In each case, the T-cell response was found to be predominantly against hexon conserved regions.…”