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Binding of hepatitis C virus to CD81
P Pileri1, Y Uematsu, S Campagnoli
1IRIS, Chiron, Siena 53100, Italy.
Insights
Hepatitis C virus (HCV) uses its E2 protein to bind CD81 on liver and B cells. This interaction is crucial for viral entry and can be blocked by neutralizing antibodies, offering potential therapeutic targets.
Area of Science:
- Virology
- Immunology
- Hepatology
Background:
- Chronic hepatitis C virus (HCV) infection affects 3% of the global population, leading to significant liver disease.
- HCV is linked to cryoglobulinemia, a B lymphocyte disorder, indicating a broader impact beyond the liver.
- The precise mechanisms of HCV cell entry and its tropism remain incompletely understood.
Purpose of the Study:
- To investigate the interaction between the HCV E2 envelope protein and host cell receptors.
- To identify the specific region on CD81 involved in HCV binding.
- To explore the potential of blocking this interaction as a strategy against HCV infection.
Main Methods:
- Mapping the binding site of HCV E2 protein on human CD81.
- Utilizing recombinant molecules containing the CD81 major extracellular loop.
- Assessing the effect of neutralizing antibodies on HCV-CD81 binding in vitro.
Main Results:
- The HCV E2 envelope protein specifically binds to human CD81, a tetraspanin found on hepatocytes and B lymphocytes.
- Binding was localized to the major extracellular loop of CD81.
- Antibodies known to neutralize HCV infection in vivo effectively inhibited the binding of HCV to CD81 in vitro.
Conclusions:
- CD81 serves as a key receptor for HCV entry into host cells, particularly hepatocytes and B lymphocytes.
- The E2 protein's interaction with the CD81 extracellular loop is critical for viral attachment.
- Targeting the HCV E2-CD81 interaction with neutralizing antibodies presents a promising therapeutic avenue for controlling HCV infection.
Abstract:
Chronic hepatitis C virus (HCV) infection occurs in about 3 percent of the world's population and is a major cause of liver disease. HCV infection is also associated with cryoglobulinemia, a B lymphocyte proliferative disorder. Virus tropism is controversial, and the mechanisms of cell entry remain unknown. The HCV envelope protein E2 binds human CD81, a tetraspanin expressed on various cell types including hepatocytes and B lymphocytes. Binding of E2 was mapped to the major extracellular loop of CD81. Recombinant molecules containing this loop bound HCV and antibodies that neutralize HCV infection in vivo inhibited virus binding to CD81 in vitro.