AIM:To explore the properties of hypervariable region 1(HVR1) in the envelope 2 gene of hepatitis C virus byanalyzing the reactivity of HVR1 fusion proteins from differentChinese HCV strains with sera of patients with chronichepatitis C and by comparing their reactivity betweeninterferon therapy responders and non-responders.METHODS:Gene fragments of HVR1 of four HCV strains(three genotype lb and one genotype 2a) were amplifiedfrom pGEMT-E2 plasmids and sub-cloned into pQE40vectors respectively to construct recombinant expressionplasmids which expressed HVR1 fused downstream toDHFR in Escherichia coli strain TG1.The purified DHFR-HVR1 proteins were then used to detect the anti-HVR1antibodies in 70 serum samples of patients with chronichepatitis C.RESULTS:Four DHFR-HVR1 fusion proteins weresuccessfully expressed in E.coli (320-800 ug fusion proteinsper 100 ml culture).Each fusion protein (SHlb,BJlb,SDlb and SD2a) reacted with 72.8% (51/70),60% (42/70),48.6% (34/70),and 58.6% (41/70) of the anti-HCVpositive patients’ sera respectively by ELISA.57.1% (4/7) of non responders reacted with all four HVR1 fusionproteins,while only 15.3% (2/13) of responders reactedwith all of them.The O.D.values of sera from IFN therapyresponders were significantly higher than those of nonresponders (P<0.05).CONCLUSION:The selected HVR1 fusion proteinsexpressed in E.coli can broadly react with HCV-infectedpatients’ sera.The intensity and/or quality of the immuneresponse against HCV may be a critical factor determiningthe response to interferon treatment.With the evolution ofvirus strains,anti-HVR1 antibodies can not neutralize all thequasispecies.A polyvalent and high immunogenic vaccinecomprising a mixture of several HVR1 sequences that coverthe reactivity of most HCV isolates may be useful. AIM: To explore the properties of hypervariable region 1 (HVR1) in the envelope 2 gene of hepatitis C virus by analyzing the reactivity of HVR1 fusion proteins from different Chinese HCV strains with sera of patients with chronic hepatitis C and by comparing their reactivity between interferon therapy responders and non -responders.METHODS: Gene fragments of HVR1 of four HCV strains (amplified from pGEMT-E2 plasmids and sub-cloned into pQE40 vectors respectively to construct recombinant expression plasmids which express HVR1 fused downstream to DHFR in Escherichia coli strain TG1 . The purified DHFR-HVR1 proteins were then used to detect the anti-HVR1 antibodies in 70 serum samples of patients with chronic hepatitis C. C. RESULTS: Four DHFR-HVR1 fusion proteins weresuccessfully expressed in E. coli (320-800 μg fusion proteinper 100 ml culture ). Each fusion protein (SHlb, BJlb, SDlb and SD2a) reacted with 72.8% (51/70), 60% (42/70), 48.6% (34/70), and 58.6% (41/70) the anti-HCV positive patients’ sera respectively by ELISA. 57.1% (4/7) of non responders reacted with all four HVRl fusion proteins, while only 15.3% (2/13) of responders with all of them. ODvalues ​​of sera from CONCLUSION: The selected HVR1 fusion protein expressed in E. coli can broadly react with HCV-infected patients’ sera. Intensity and / or quality of the immune response against HCV may be a critical factor determining the response to interferon treatment. With the evolution of virus, anti-HVR1 antibodies can not be neutralized all the quasispecies. A polyvalent and high immunogenic vaccine consensus in a mixture of several HVR1 sequences that coverthe reactivity of most HCV isolates may be useful.