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 (three genotype 1b and one genotype 2a) were amplified from pGEMT-E2 plasmids and sub-cloned into pQE40 vectors respectively to construct recombinant expression plasmids which expressed 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.
RESULTS:Four DHFR-HVR1 fusion proteins were successfully expressed in E.coli (320-800 ug fusion proteins per 100 ml culture). Each fusion protein (SH1b, BJ1b, SD1b and SD2a) reacted with 72.8 % (51/70), 60 % (42/ 70), 48.6 % (34/70), and 58.6 % (41/70) of the anti-HCV positive patients' sera respectively by ELISA. 57.1 % (4/ 7) of non responders reacted with all four HVR1 fusion proteins, while only 15.3 % (2/13) of responders reacted with all of them. The O.D. values of sera from IFN therapy responders were significantly higher than those of non responders (P<0.05).
CONCLUSION:The selected HVR1 fusion proteins expressed in E. coli can broadly react with HCV-infected patients' sera. The 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 strains, anti-HVR1 antibodies can not neutralize all the quasispecies. A polyvalent and high immunogenic vaccine comprising a mixture of several HVR1 sequences that cover the reactivity of most HCV isolates may be useful.
INTRODUCTIONHepatitis C virus (HCV) is the major etiologic agent of blood transfusion-associated and sporadic non-A non-B hepatitis worldwide. About 70 % of the infections become chronic, among which a significant proportion eventually develops cirrhosis and hepatocellular carcinoma. Despite recent success after the combination therapy with Interferon-α and ribavirin [1][2][3] , about 60 % of patients still fail to respond. Thus, the development of HCV vaccine is especially important, but it remains an urgent challenge due to the high mutation rate of HCV.Multiple lines of evidence indicate that one of the principal neutralization determinants corresponds to the hypervariable region 1 (HVR1), which is located in the amino-terminus of E2 of HCV (nt1150-1230). Zibert et al [4] found that an early appearance of antibodies directed to HVR1 is associated with acute self-limiting infection of HCV, while the persistence of HVR1 antibodies is associated with chronic HCV infection. Antibodies against HVR1 have been shown to block adsorption to susceptible cells in vitro [5,6] . Animal antibodies raised against this region have provided effective prophylaxis in chimpanzee challenge experiments...