Scientific Publications by FDA Staff

J Virol 2018 Feb 26;92(6):e01742-17

Determinants in the IgV domain of human HAVCR1 (TIM-1) are required to enhance hepatitis C virus entry.

Kachko A, Costafreda MI, Zubkova I, Jacques J, Takeda K, Wells F, Kaplan G, Major ME

Hepatitis C virus (HCV) is the leading cause of chronic hepatitis in humans. Several host molecules participate in HCV cell entry but this process remains unclear. The complete unraveling of the HCV entry process is important to further understand viral pathogenesis and develop therapeutics. The human hepatitis A virus (HAV) cellular receptor 1 (HAVCR1), CD365, also known as TIM-1, functions as a phospholipid receptor involved in cell entry of several enveloped viruses. Here, we studied the role of HAVCR1 in HCV infection. HAVCR1 antibody inhibited entry in a dose dependent manner. HAVCR1 soluble constructs neutralized HCV, which did not require the HAVCR1 mucin-like region, and was abrogated by a N94A mutation in the IgV phospholipid-binding pocket; indicating a direct interaction of the HAVCR1 IgV with HCV virions. However, knock out of HAVCR1 in Huh7 cells reduced but did not prevent HCV growth. Interestingly, the mouse HAVCR1 ortholog, also a phospholipid receptor, did not enhance infection and a soluble form failed to neutralize HCV although replacement of the mouse IgV domain with the human HAVCR1 IgV restored the enhancement of HCV infection. Mutations in the cytoplasmic tail revealed that direct HAVCR1 signaling is not required to enhance HCV infection. Our data show that the phospholipid binding function and other determinant(s) in the IgV domain of human HAVCR1 enhance HCV infection. Although the exact mechanism is not known, it is possible that HAVCR1 facilitates entry by stabilizing or enhancing attachment leading to direct interactions with specific receptors, such as CD81. IMPORTANCE: Hepatitis C virus (HCV) enters cells through a multi-faceted process. We identified the human hepatitis A virus cellular receptor 1 (HAVCR1), CD365, also known as TIM-1, as a facilitator of HCV entry. Antibody blocking, and silencing or knock out of HAVCR1 in hepatoma cells reduced HCV entry. Our findings that the interaction of HAVCR1 with HCV early during infection enhances entry but is not required for infection support the hypothesis that HAVCR1 facilitates entry by stabilizing or enhancing virus binding to the cell surface membrane and allowing the correct virus-receptor positioning for interaction with the main HCV receptors. Furthermore, our data show that in addition to the phospholipid binding function of HAVCR1, the enhancement of HCV infection involves other determinants in the IgV domain of HAVCR1. These findings expand the repertoire of molecules that HCV uses for cell entry, adding to the already complex mechanism of HCV infection and pathogenesis.