Discovery of immunodominant T-cell epitopes reveals penton protein as a second immunodominant target in human adenovirus infection

Abstract

BackgroundHuman adenovirus (HAdV) infections remain a significant cause of morbidity and mortality after hematopoietic stem cell transplantation (HSCT). Efficient antiviral T-cell responses are necessary to clear infection, which is hampered by delayed immune reconstitution and medical immunosuppression after HSCT. Protective immunity may be conferred by adoptive transfer of HAdV-specific T cells. For identification of patients at risk and monitoring of treatment responses diligent assessment of anti-HAdV cellular immune responses is crucial. The HAdV-derived protein hexon has been recognized as a major immunodominant target across HAdV species. We aimed at identifying further targets of protective anti-HAdV immune response and characterizing immunogenic epitopes.MethodsNineteen candidate nonamers from hexon and penton proteins were identified by epitope binding prediction. Peptides were synthesized and tested for in vivo immunogenicity by screening peripheral blood mononuclear cells from healthy volunteers (n = 64) and HAdV-infected stem cell recipients (n = 26) for memory T cells recognizing the candidate epitopes in the context of most common HLA alleles.ResultsFunctional CD8+ T cells recognizing seven epitopes were identified, among them four penton-derived and two hexon-derived peptides. The HLA-A*01-restricted penton-derived peptide STDVASLNY (A01PentonSTDV) and HLA-A*02-restricted hexon-derived peptide TLLYVLFEV (A02HexonTLLY) were recognized by more than half of the persons carrying the respective HLA-type.ConclusionsThus, the HAdV-derived penton protein is a novel major target of the anti-HAdV immune response. Identification of new immunodominant epitopes will facilitate and broaden immune assessment strategies to identify patients suitable for T-cell transfer. Knowledge of additional target structures may increase T-cell recovery in manufacturing processes.Electronic supplementary materialThe online version of this article (doi:10.1186/s12967-016-1042-2) contains supplementary material, which is available to authorized users.

Recombinant Live Attenuated Influenza Vaccine Viruses Carrying Conserved T Cell Epitopes of Human Adenoviruses Induce Functional Cytotoxic T Cell Responses and Protect Mice against both Infections

“…The most commonly studied is Mastadenovirus C, and the greatest number of epitopes was detected in the hexon protein. This protein contains multiple conserved regions enriched with immunogenic T-cell epitopes, which are conserved among different AdV groups [ 27 , 28 , 29 , 30 ]. Therefore, we selected the 80 amino acid-long C-terminus domain of the AdV hexon protein (residues 855 to 935) as an AdV cassette vaccine insert due to its high level of conservancy among different AdV serotypes ( Figure S3 ) and also because it is enriched with experimental human T-cell epitopes ( Figure 2 A).…”

Transfer of Hexon‐ and Penton‐selected adenovirus‐specific T cells for refractory adenovirus infection after haploidentical stem cell transplantation

“…This is the first report on the feasibility of adeno‐reactive T‐cells that had been produced using penton‐directed manufacturing and subsequently leading to specific T‐cell responses upon adoptive transfer. The adenoviral penton protein is a recently described second immunodominant target . Application of penton‐specific T cells improved the immune response shown in ELISpot assay and was followed by a 2 log decrease of viral loads.…”

“…Monitoring of HAdV viral load in blood and stool was performed by routine quantitative PCR as described earlier . Quantification of HAdV‐specific T‐cell frequencies was done before and after T‐cell transfer by IFN‐γ ELISpot assay as described and using the following peptide pools: ppADV5 Hexon, ppADV5 Penton (all Miltenyi Biotec) . If suitable numbers of PBMCs were obtained, HAdV‐specific T cells were expanded over 7 days using the respective antigens ppADV5 Hexon and ppADV5 Penton in TexMACS media (Miltenyi Biotec) containing 50 U/mL IL‐2 (Peprotec).…”

“…Because of failure to achieve durable response in the patient ( Figure 1B) and the presence of penton-directed HAdV-specific T cells in the blood of the mother (Figure 2A,B; Table S1), we decided to include the newly identified immunogenic PepTivator AdV5 Penton for the third and fourth preparation. 1 The child received a total of ten doses of HAdVspecific T cells within a period of 5 months (Table 1, Figure 1A). The first five doses were hexon-selected HAdV-specific T cells.…”

Past and present of monitoring the functional immune response developed against Epstein-Barr and Adenovirus in hematopoietic stem cell transplantation

“…Al igual que para el EBV, se han utilizado otras técnicas para la monitorización de estos LT específicos de AdV como ELISPOT y multímeros, obteniendo similares conclusiones y sin poder también establecer un valor umbral que defina futuras reactivaciones víricas. Además, se ha identificado la proteína pentón de AdV como portadora de epítopos inmunogénicos, lo cual, permitirá ampliar las estrategias de evaluación inmunológica 50 .…”