Diverse CD81 proteins support hepatitis C virus infection

Area of Science:

• Virology
• Immunology
• Genetics

Background:

• Hepatitis C virus (HCV) entry into host cells is a critical step in infection.
• CD81, a tetraspanin protein, is a known host factor essential for HCV entry.
• Understanding the role of CD81 sequence variation in determining HCV host tropism is crucial for developing antiviral strategies.

Purpose of the Study:

• To investigate if variations in the CD81 protein sequence influence the host range of Hepatitis C virus.
• To determine the correlation between CD81 sequence, its interaction with viral proteins, and its ability to support HCV entry.

Main Methods:

• Expression of a diverse panel of CD81 proteins from different species.
• Testing the binding of recombinant CD81 large extracellular loop (LEL) proteins to soluble HCV E2 (sE2).
• Assessing the ability of CD81 variants to mediate entry of HCV pseudotyped viruses (HCVpp) and cell culture-grown HCV.

Main Results:

• Human and African green monkey CD81 LEL bound sE2 and inhibited HCVpp infection, while mouse and rat CD81 did not.
• All expressed CD81 proteins, when present on cells, conferred susceptibility to HCVpp and cell culture-grown HCV, with varying efficiencies.
• Mutations in human CD81 that abolished sE2 binding still supported HCVpp infection, indicating a complex relationship between binding and entry.

Conclusions:

• CD81 sequence exhibits significant plasticity in supporting HCV entry, suggesting it contributes to, but does not solely determine, species-specific HCV susceptibility.
• Interaction assays with sE2 do not fully predict the capacity of CD81 variants to support viral entry.
• Further research into CD81 polymorphism and its impact on HCV infection dynamics is warranted.