Distantly related hepaciviruses share common entry factor, Claudin-1

Due to increased and broadened screening efforts, the last decade has seen a rapid expansion in the number of viral species classified into the Hepacivirus genus. Conserved genetic features of hepaciviruses suggest they have undergone specific adaptation and evolved to hijack similar host proteins for efficient propagation in the liver. Here, we developed pseudotyped viruses to elucidate the entry factors of GB virus-B (GBV-B), the first hepacivirus described in an animal, closely related to hepatitis C virus (HCV). GBV-B pseudotyped viruses (GBVBpp) were shown to be uniquely sensitive to the serum of tamarins infected with GBV-B, validating their usefulness as a surrogate for GBV-B entry studies. We screened GBVBpp infection of hepatoma cell lines CRISPR/Cas9-engineered to ablate expression of individual HCV receptors/entry factors and found that claudin-1 is essential for GBV-B infection, indicating GBV-B and HCV share a common entry factor. Our data suggest that claudin-1 facilitates HCV and GBV-B entry through distinct mechanisms since the former requires the first extracellular loop and the latter is reliant on the second extracellular loop. The implication of this sharing of claudin-1 as an entry factor between these two hepaciviruses on their tissue tropism and evolutionary relationships will be discussed. ImportanceHepatitis C virus (HCV) is a major public health burden; approximately 58 million individuals have chronic HCV infection which could lead to cirrhosis and liver cancer. To achieve the World Health Organisation target of eliminating hepatitis by 2030, new therapeutics and vaccines are needed. Understanding how HCV enters the cells will inform the design of new vaccines and treatments, targeting the first stage of HCV infection. However, the entry mechanism is complex and sparsely described. Studying the entry of related hepaciviruses will increase the knowledge of the molecular mechanisms of the first stages of HCV infection, such as the membrane fusion, and inform structure-guided HCV vaccine design; in this work we have identified a protein, Claudin-1, which facilitates the entry of HCV-related hepacivirus, but with a mechanism not described for HCV. Similar work on other hepaciviruses may unveil commonality of entry factors and possibly new mechanisms.