Abstract: ObjectiveTo study the change of E2/NS1 area of hepatctis C virus(HCV)caused by human immunodeficiency virus(HIV)/HCV co-infection and homologic differences between the two groups and to provide evidence for the treatment of HCV/HIV co-infection.MethodsTotally 255 HCV positive cases were divided into two groups according to their HIV infection status and the HCV genotypes of the cases were identified.The E2/NS1 of HCV was amplified with reverse transcription-PCR(RT-PCR)for single strand conformation polymorphism(SSCP)analysis and sequenced after purification.ResultsThere were statistical differences between the HCV/HIV co-infection group and the HCV mono-infection group in genotype of HCV(χ²=35.4,P<0.001).There were statistical differences between the HCV/HIV co-infection group and the HCV mono-infection group in SSCP strip number(t=2.32,P=0.049).The homology of E2/NS1 of HCV for HCV mono-infection and HIV/HCV co-infection was 76.7% and 87.6%,respectively,with a significant difference (χ²=20.13,P<0.001).The variation in the two groups comes from HVR-1,HVR-2,and HVR-3.The homologic differences of the two groups are HCV E2/NS1,HVR-1,and HVR-3.The amino acid sites have high mutation in HCV monoinfection group but are more conservative in the HCV/HIV co-infection group.ConclusionHCV 1b is the main genotype in HCV mono-infection and HIV/HCV co-infection groups,but there are significant differences in HCV genotype distribution between the two groups.HIV can reduce the gene variant of 1b HCV E2/NS1,mainly in HVR-1 and HVR-3 area.