Reciprocal cross-species infection potential of human and domestic cat hepatitis B viruses

Background and Aims: The host tropism of human hepatitis B virus (HBV) limits cross-species transmission and hampers animal model development. Recently identified domestic cat hepatitis B virus (DCHBV) shares high similarity with HBV in viral receptor-binding motifs and their cognate receptor, sodium taurocholate co-transporting polypeptide (NTCP), suggesting potential for cross-species transmission. This study aimed to assess the reciprocal transmission capacity between HBV and DCHBV and identify key determinants of host specificity. Approach and Results: Transfection of Huh7 cells with a DCHBV infectious clone alone, or co-transfection with hepatitis delta virus (HDV) cDNA, produced DCHBV or HDV pseudotyped with DCHBV envelope proteins (DCHDV), respectively. Cross-species infection was assessed using HepG2 cells expressing human or cat NTCP (HepG2-hNTCP/cNTCP), as well as primary human or cat hepatocytes (PHH/PCH). HBV and HDV efficiently infected HepG2-cNTCP cells and PCH. In contrast, DCHBV/DCHDV failed to infect HepG2-hNTCP cells and PHH, despite successful infection of PCH. All the infections could be inhibited by the myristoylated preS1/2-48 peptide, indicating that cNTCP is the bona fide receptor for DCHBV infection. Inefficient internalization may restrict DCHBV/DCHDV infection of human hepatocytes. Using chimeric envelope proteins, we found that the region spanning residues 16-49 of DCHBV preS1 restricts its transmission to human hepatocytes. Additionally, overexpression of cat orthologs of the proposed HBV cofactors EGFR and NRP1 did not rescue the infection. Conclusions: These findings suggest a marginal zoonotic risk of DCHBV for humans and support domestic cats as a potential immunocompetent animal model for HBV research.