Identification of novel HLA-A*0201-restricted CD8+ T-cell epitopes on hepatitis delta virus

Abstract

Hepatitis delta virus (HDV) superinfection causes a poor prognosis in hepatitis B virus-infected patients and effective therapy is lacking. Cytotoxic T-lymphocyte (CTL) responses play an important role in the pathogenesis of chronic viral hepatitis; however, the CD8 + T-cell epitopes of HDV have never been defined. Potential HLA-A*0201-restricted HDV peptides were selected from the SYFPEITHI database and screened by T2 cell-stabilization assay. HLA-A*0201 transgenic mice on a C57BL/6 background were injected intramuscularly with an HDV DNA vaccine. Splenocytes were stained directly ex vivo with HLA-A*0201-peptide tetramers after immunization. Epitope-specific CTL responses were confirmed by cytotoxic assays. HLA-A2, chronically infected HDV patients were also enrolled, to assess the existence of HDV-specific CD8 + T cells, based on findings in animals. Following HDV DNA vaccination, nearly 0?9 % of the total splenic CD8 + T cells were specific for peptides HDV 26-34 and HDV 43-51 in HLA-A*0201 transgenic mice, which was significantly higher than the number found in non-transgenic mice or in transgenic mice that had been immunized with control plasmid. HDV 26-34-and 43-51-specific CTL lines were able to produce CTL responses to each peptide. Interestingly, HDV 26-34-and HDV 43-51-specific CD8 + T cells were also detectable in two chronically infected HDV patients in the absence of active HDV replication. In conclusion, HDV 26-34 and 43-51 are novel HLA-A*0201-restricted CTL epitopes on genotype I HDV. HDV 26-34-and 43-51-specific CTLs have been detected in chronic hepatitis delta patients without active disease. Evoking CTL responses to HDV may be an alternative approach to controlling HDV viraemia in patients with chronic hepatitis delta.

Positive Selection of Hepatitis Delta Antigen in Chronic Hepatitis D Patients

“…In HBV and hepatitis C virus infections, multispecific CD8 ϩ T-cell responses to HBV and hepatitis C virus are closely associated with viral clearance (8,24). Our previous study revealed that aa 26 to 34 and aa 43 to 51 of HDAg are novel HLA-A*0201-restricted CTL epitopes in genotype I HDV (10). Using a neural network method, our analysis suggested more potential CTL epitopes in the genotype I.…”

“…Based on the assumption that host immunity interacts mostly with the majority in the viral population, the dominant variants of the first time point from each patient were selected for analysis. Among the high-affinity list of the predicted ligands, the cutoff binding level was determined by sites tested in a HLA-A*0201 transgenic mice model (10). The analyses were done by the NetMHC program v2.1 (15).…”

“…Cytotoxicity was hypothesized in some studies but was not supported by many others (6,17). An immune mechanism is believed by most investigators to be responsible for hepatic inflammation and clearance of HDV (10,16). B-cell and T-cell epitopes were mapped based on in vitro studies (16,25).…”

“…B-cell and T-cell epitopes were mapped based on in vitro studies (16,25). Recently, we reported two potential cytotoxic T-cell epitopes in animal and in vitro studies (10,11). We reported that HDV variants in quasispecies might be changed during clinical course of chronic hepatitis D (29).…”

Protective immunity with an E1 multivalent epitope DNA vaccine against cottontail rabbit papillomavirus (CRPV) infection in an HLA-A2.1 transgenic rabbit model

“…A T2 cell-stabilization assay was also performed as described previously with some modification [21]. T2 cells were seeded into 96-well U-bottom plates at a density of 3×10 5 /ml and incubated for 18 h with each peptide (20 μg/ml) at 26 °C.…”