AIM: To analyze the neutralizing activity of antibodies against E1 region of hepatitis C virus (HCV). Specific polyclonal antibody was raised via immunization of New Zealand rabbits with a synthetic peptide that had been derived from the E1 region of HCV and was shown to be highly conserved among HCV published genotypes. METHODS: Hyper-immune HCV E1 antibodies were incubated over night at 4℃with serum samples positive for HCV RNA, with viral loads ranging from 615 to 3.2 million IU/ mL. Treated sera were incubated with HepG2 cells for 90 min. Blocking of viral binding and entry into cells by anti E1 antibody were tested by means of RTPCR and flow cytometry. RESULTS: Direct immunostaining using FITC conjugated E1 antibody followed by Flow cytometric analysis showed reduced mean fluorescence intensity in samples pre-incubated with E1 antibody compared with untreated samples. Furthermore, 13 out of 18 positive sera (72%) showed complete inhibition of infectivity as detected by RT-PCR. CONCLUSION: In house produced E1 antibody, blocks binding and entry of HCV virion infection to target cells suggesting the involvement of this epitope in virus binding and entry. Isolation of these antibodies that block virus attachment to human cells are useful as therapeutic reagents. AIM: To analyze the neutralizing activity of antibodies against E1 region of hepatitis C virus (HCV). Specific polyclonal antibody was raised via immunization of New Zealand rabbits with a synthetic peptide that had been derived from the E1 region of HCV and was shown to be Highly conserved among HCV published genotypes. METHODS: Hyper-immune HCV E1 antibodies were incubated at night at 4°C with serum samples positive for HCV RNA, with synchronized viral ranging from 615 to 3.2 million IU/ mL. Treated sera were cultured with HepG2 cells. For 90 min. Blocking of viral binding and entry into cells by anti E1 antibody were tested by means of RTPCR and flow cytometry. RESULTS: Direct immunostaining using FITC conjugated E1 antibody followed by Flow cytometric analysis show reduced mean fluorescence intensity in samples pre-incubated With E1 antibody compared with untreated samples., 13 out of 18 positive sera (72%) showed complete inhibition of infectivity as detected by RT-PCR. C ONCLUSION: In house produced E1 antibody, blocks binding and entry of HCV virion infection to target cells suggesting the involvement of this epitope in virus binding and entry. Isolation of these antibodies that block virus attachment to human cells are useful as therapeutic reagents.