【Objective】 To study the CD4 T cell epitopes in Core and NS3 protein of genotype 1(GT1) and 6(GT6) of hepatitis C virus(HCV). 【Methods】 A total of 298 overlapping peptides(16-mer) spanning Core and NS3 protein of GT1 and GT6 HCV were synthesized. Peripheral blood mononuclear cells(PBMCs) from 17 HCV+ and 7 healthy blood donors were stimulated by peptide pools, followed by evaluating T cell response by IFN-γ ELISPOT, by which 21 peptides with positive results were found. These peptides were further applied to individually stimulate 20 HCV+ and 18 healthy PBMCs. The differences of responsive frequencies to the 21 positive peptides between the two study groups were compared. 【Results】 Pooled and individual peptide stimulation tests showed that HCV+ PBMCs were responsive to the stimulation of 5 peptides(GT1 NS31273-1288 and NS31315-1330; GT6 NS31033-1048, NS31087-1102 and NS31351-1366), with a responsive frequency ranging 18.9%-27.0%. In contrast, healthy PBMCs were not or low responsive(0%-4.0%) to these five peptides. The responsive frequencies were statistically different between the two groups(P<0.05). No reported epitopes in IEDB were found identical with these 5 peptides via sequence alignment. 【Conclusion】 Our study identified novel CD4 T cell epitopes in NS3 protein of GT1 and GT6 HCV, which has potential application value for the research and development of HCV vaccine.

【Objective】 To investigate the correlation of peripheral myeloid-derived suppressor cells (MDSC) with hepatitis c virus (HCV) infection. 【Methods】 109 voluntary blood donors who donated blood during February 2018 to September 2020 at Guangzhou Blood Center were recruited in this study. They were assigned to chronic hepatitis c (CHC) group (n=48), spontaneous clearance (SC) group (n=29) and healthy donors (control) group (n=32) according to the results of anti-HCV and HCV RNA tests. Blood samples were drawn from the participants and peripheral blood mononuclear cells (PBMC) were freshly isolated, followed by staining with fluorescently-labeled antibody against cell surface markers of MDSC, which were then applied to the detection of monocytic- (M) and polymorphonuclear (PMN)-MDSC by flow cytometry. Parameters for liver function including alanine aminotransferase (ALT), aspartate aminotransferase (AST), γ-glutamyl transpeptidase (GGT), total bilirubin (TBIL) and direct bilirubin (DBIL) were also measured. One-way ANOVA tests were applied to compare the differences of M- and PMN-MDSC and liver function between three study groups. For pairwise comparisons, P values were adjusted for multiple comparisons by Bonferroni correction (Pc). 【Results】 The frequencies of M-MDSC (%) in CHC, SC and HC were 1.39±0.86, 0.85±0.63 and 0.57±0.23, respectively (P<0.01). Specifically, CHC presented significantly higher level of M-MDSC than SC (Pc<0.01) and control (Pc<0.05). There was no significant difference in the frequencies of PMN-MDSC among the three study groups (0.81±0.54 vs 0.65±0.40 vs 0.62±0.29, P>0.05). In addition, AST (34.4±19.2 vs 23.0±7.78 U/L) and GGT (40.8±31.4 vs 22.3±7.40 U/L) level were higher in CHC compared with control (Pc<0.05 and Pc<0.01, respectively). 【Conclusion】 The level of peripheral M-MDSC was significantly elevated in chronic HCV infected donors, which would related to the progression of chronicity after HCV infection.