3% and 70.0 ± 3.2% of cells incubated with control rat or mouse mAbs stained positive for NS5A and E2, respectively, incubation with QQ-4G9-A6 and NK-8H5-E3 markedly reduced the number of NS5A-positive (14.2 ± 3.4%) and E2-positive (16.7 ± 2.6%) cells (Fig. 3E,F). Taken together, these data indicate that a postbinding function of SR-BI is required for HCV cell-to-cell transmission and spread. The SR-BI ectodomain has been demonstrated to be important for both HDL binding and CE Selleck LY294002 uptake, but the determinants involved in these processes have not yet been defined. To assess whether anti–SR-BI mAbs inhibiting

HCV postbinding steps affect HDL binding to SR-BI, we studied Cy5-labeled HDL binding to hSR-BI in the presence or absence of anti–SR-BI mAbs. In contrast

to polyclonal anti–SR-BI serum, which inhibited Cy5-labeled HDL binding, none of the anti–SR-BI mAbs markedly interfered with HDL–SR-BI binding at concentrations inhibiting HCV infection by up to 90% (Fig. 4A, statistically not significant). Furthermore, we investigated the effect of these mAbs on CE uptake and cholesterol efflux. Whereas PS-6A7-C4, PS-7B11-E3, NK-6B10-E6, and NK-6G8-B5 had no effect on lipid transfer, QQ-4A3-A1, QQ-2A10-A5, QQ-4G9-A6, and NK-8H5-E3 partially reduced both CE uptake and cholesterol Obeticholic Acid efflux at concentrations inhibiting HCV infection by up to 90% (Fig. 4B,C). These data indicate that the anti–SR-BI mAbs inhibiting HCVcc infection also partially inhibit

SR-BI–mediated lipid transfer (Table 1). Taken together, these data suggest that SR-BI determinants involved in HCV postbinding events do not mediate HDL binding but may contribute to lipid transfer, in line with the reported link between the SR-BI lipid transfer function and HCV infection.11, 12, 23 To assess the clinical relevance of blocking SR-BI postbinding function to inhibit Fossariinae HCV infection, we determined the effect of anti–SR-BI mAbs on entry into Huh7.5.1 cells of HCVcc and HCVpp of major genotypes and highly infectious HCV strains selected during liver transplantation (P02VJ). All anti–SR-BI mAbs inhibiting HCVcc genotype 2a (Jc1) infection (QQ-4A3-A1, QQ-2A10-A5, QQ-4G9-A6 and NK-8H5-E3) also inhibited infection of HCVcc and HCVpp of all major genotypes (P < 0.01), whereas VSV-Gpp entry was unaffected (Fig. 5 and Supporting Fig. 3). Moreover, entry of patient-derived HCVpp P02VJ into both Huh7.5.1 cells and primary human hepatocytes was also efficiently inhibited by these anti–SR-BI mAbs (Supporting Fig. 7 and data not shown). Given that combinations of drugs targeting both viral and host factors represents a promising future approach to prevent and treat HCV infection, we next determined whether the combination of anti–SR-BI mAbs NK-8H5-E3 or QQ-2A10-A5 and anti-HCV envelope antibodies results in an additive or synergistic effect on inhibiting HCV infection.