Summary auto-generated
This study compared hepatitis C virus (HCV) E2 glycoprotein binding to the CD81 receptor across three different forms: truncated soluble E2 (E2660), full-length E1E2 complex from mammalian cells, and virus-like particles (VLPs) from insect cells. All three forms bound human CD81, confirming CD81 as a potential HCV receptor. Using a panel of well-characterized monoclonal antibodies (MAbs), researchers tested which antibodies could block glycoprotein-CD81 interaction. MAbs targeting amino acid regions 396–407, 412–423, and 528–535 inhibited binding of all three forms. However, MAbs against regions 432–443 and 436–447 selectively blocked VLP binding while having no effect on E2660 or FL E1E2 complex binding. These differential inhibition patterns indicate structural differences among the E2 glycoprotein forms. The findings suggest that the E2 region 412–447 plays a critical role in CD81 interaction and highlight the importance of selecting appropriate viral ligands for structure-function studies, as VLPs may more accurately represent native virion conformations compared to soluble or non-particulate forms.
Key findings
- Three different HCV E2 glycoprotein forms (truncated E2660, full-length E1E2, and VLPs) all bind CD81, but exhibit structural differences in their epitope accessibility
- MAbs targeting E2 amino acid regions 412–423 and 528–535 block CD81 binding across all three glycoprotein forms, identifying critical interaction regions
- MAbs against E2 regions 432–447 and 436–447 selectively inhibit VLP-CD81 interaction but not E2660 or FL E1E2 interaction, indicating VLPs have distinct structural properties
- VLPs likely represent more native virion-like conformations than soluble glycoprotein forms and should be carefully selected for studying HCV receptor interactions
- The E2 region 412–447 appears particularly important for CD81-binding modulation based on multiple MAb inhibition patterns
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Abstract
Structurefunction analysis of the hepatitis C virus (HCV) envelope glycoproteins, E1 and E2, has been difficult due to the unavailability of HCV virions. Truncated soluble forms of E2 have been used as models to study virus interaction with the putative HCV receptor CD81, but they may not fully mimic E2 structures on the virion. Here, we compared the CD81-binding characteristics of truncated E2 (E2660) and full-length (FL) E1E2 complex expressed in mammalian cells, and of HCV virus-like particles (VLPs) generated in insect cells. All three glycoprotein forms interacted with human CD81 in an in vitro binding assay, allowing us to test a panel of well-characterized anti-E2 monoclonal antibodies (MAbs) for their ability to inhibit the glycoproteinCD81 interaction. MAbs specific for E2 amino acid (aa) regions 396407, 412423 and 528535 blocked binding to CD81 of all antigens tested. However, MAbs specific for regions 432443, 436443 and 436447 inhibited the interaction of VLPs, but not of E2660 or the FL E1E2 complex with CD81, indicating the existence of structural differences amongst the E2 forms. These findings underscore the need to carefully select an appropriate ligand for structurefunction analysis.