Ggesting differential affinity of the HCV-LPs towards liver cells. The binding of HCV-LP to the Huh7 cells was maximum at 4h of incubation and after which there was decrease in fluorescence. It is possible that after 4h of incubation, the HCV-LPs enter into the cells by receptor mediated endocytosis. Interestingly, both genotype 3a and genotype 1b HCV-LPs showed similar results. There is a cascade of events which enable the attachment and entry of HCV into permissive cells. The mAbs E8G9 and D2H3 are probably against the HCV-LP envelope protein region involved in binding to any one of the several set of cellular receptor proteins. Since the Hypericin manufacturer epitope for the E8G9 was putatively mapped to 596?46 which is probably structurally close to the sites of the E2 protein critical for CD81 receptor binding (,420, 527, 529, 530, 535) [33,34] it might have been more effective in prevention of the virus binding. The same E8G9 mAb also showed better inhibition (,66 ) of virus entry in the HCV cell culture system and the mAb H1H10 showed only marginal inhibition (,30 ). Perhaps the epitope for H1H10 is mapped to a distant location from the receptor binding domains of E2 protein. Further, mAbs D2H3, G2C7 and E1B11 didn’t show significant inhibition of binding of HCV-LP to Huh 7 cells. The epitope for D2H3 has been mapped in the region 4 (596?99 aa of E2 protein), which might be far from receptor 26001275 binding sites. The epitopes for H1H10, G2C7 and E1B11 could not be mapped by western blot Lecirelin web analysis, possibly due to the fact that the mAbs are conformation specific. Since IgG from culture supernatant of hybridoma cells were used for the ELISA assay, it is possible that the E8G9 and H1H10 specific IgG concentration is low which is reflected in the low titrers. Though mAb E8G9 inhibited the binding of the VLPs to Huh7 cells, the inhibition seen is not more than ,66 . This can be attributed to the fact that HCV binding to cells involves more than one receptor. Inhibition of binding to at least the CD81 and SRB1 would be required for complete inhibition. Moreover the HCVLPs were generated in baculovirus system; therefore the glycosylation of the insect cell expressed envelope proteins, which were earlier shown to be important for the virus entry [34], may be different when compared to HCV replicating in mammalian cells. Earlier Keck et al have demonstrated the involvement of the Nterminus of HCV envelope protein E1 in virus binding and entry using a monoclonal antibody derived from this region. The mAb H111 was able to bind to HCV E1 of genotypes 1a, 1b, 2b, and 3a indicating the conservation of this epitope across the genotypes. However, still the mAb H111 could achieve only upto 70 inhibition of HCV-LP binding [35]. Additionally, Triyatni et al. [21] has demonstrated that several mAbs derived from multiple epitops within HVR-1could strongly bind to HCV-LP, suggesting that these epitopes are also exposed on the viral surface [21,36]. In fact, Zibert et al has successfully demonstrated using patient serum that blocking of viral attachment can be revered by preincubating serum with HVR1 specific proteins. However, considering the factMonoclonal Antibodies Inhibiting HCV Infectionthat the stoichiometry of the HCV-Ab complex is not clear, they have not excluded involvement of other epitopes in viral attachment [37]. Thus it appears that multiple epitopes are required for complete neutralization, to achieve more inhibition of virus entry into target cells. Although, the.Ggesting differential affinity of the HCV-LPs towards liver cells. The binding of HCV-LP to the Huh7 cells was maximum at 4h of incubation and after which there was decrease in fluorescence. It is possible that after 4h of incubation, the HCV-LPs enter into the cells by receptor mediated endocytosis. Interestingly, both genotype 3a and genotype 1b HCV-LPs showed similar results. There is a cascade of events which enable the attachment and entry of HCV into permissive cells. The mAbs E8G9 and D2H3 are probably against the HCV-LP envelope protein region involved in binding to any one of the several set of cellular receptor proteins. Since the epitope for the E8G9 was putatively mapped to 596?46 which is probably structurally close to the sites of the E2 protein critical for CD81 receptor binding (,420, 527, 529, 530, 535) [33,34] it might have been more effective in prevention of the virus binding. The same E8G9 mAb also showed better inhibition (,66 ) of virus entry in the HCV cell culture system and the mAb H1H10 showed only marginal inhibition (,30 ). Perhaps the epitope for H1H10 is mapped to a distant location from the receptor binding domains of E2 protein. Further, mAbs D2H3, G2C7 and E1B11 didn’t show significant inhibition of binding of HCV-LP to Huh 7 cells. The epitope for D2H3 has been mapped in the region 4 (596?99 aa of E2 protein), which might be far from receptor 26001275 binding sites. The epitopes for H1H10, G2C7 and E1B11 could not be mapped by western blot analysis, possibly due to the fact that the mAbs are conformation specific. Since IgG from culture supernatant of hybridoma cells were used for the ELISA assay, it is possible that the E8G9 and H1H10 specific IgG concentration is low which is reflected in the low titrers. Though mAb E8G9 inhibited the binding of the VLPs to Huh7 cells, the inhibition seen is not more than ,66 . This can be attributed to the fact that HCV binding to cells involves more than one receptor. Inhibition of binding to at least the CD81 and SRB1 would be required for complete inhibition. Moreover the HCVLPs were generated in baculovirus system; therefore the glycosylation of the insect cell expressed envelope proteins, which were earlier shown to be important for the virus entry [34], may be different when compared to HCV replicating in mammalian cells. Earlier Keck et al have demonstrated the involvement of the Nterminus of HCV envelope protein E1 in virus binding and entry using a monoclonal antibody derived from this region. The mAb H111 was able to bind to HCV E1 of genotypes 1a, 1b, 2b, and 3a indicating the conservation of this epitope across the genotypes. However, still the mAb H111 could achieve only upto 70 inhibition of HCV-LP binding [35]. Additionally, Triyatni et al. [21] has demonstrated that several mAbs derived from multiple epitops within HVR-1could strongly bind to HCV-LP, suggesting that these epitopes are also exposed on the viral surface [21,36]. In fact, Zibert et al has successfully demonstrated using patient serum that blocking of viral attachment can be revered by preincubating serum with HVR1 specific proteins. However, considering the factMonoclonal Antibodies Inhibiting HCV Infectionthat the stoichiometry of the HCV-Ab complex is not clear, they have not excluded involvement of other epitopes in viral attachment [37]. Thus it appears that multiple epitopes are required for complete neutralization, to achieve more inhibition of virus entry into target cells. Although, the.
