Identification of amino acids restricting HBV receptor function in porcine NTCP.

With 254 million chronically infected patients, hepatitis B virus (HBV) continues to be a severe health threat. While animal models play a crucial role in developing new therapies, the availability of preclinical HBV models is very limited. Therefore, novel in vivo infection models are urgently needed. The bona fide HBV receptor, sodium-taurocholate cotransporting polypeptide (NTCP), determines HBV's species and cell-type specificity. Recent studies have indicated that the expression of human NTCP is the only limiting factor for HBV infection in selected species, such as macaques or pigs. Here, we confirm HBV infection of pig hepatocytes expressing human NTCP and show that porcine NTCP does not support HBV binding. By gradually humanizing porcine NTCP and site-directed mutagenesis, we identified amino acids 158 and 167 in porcine NTCP, limiting HBV interaction. In a proof-of-concept experiment, we showed that the expression of porcine NTCP with humanized amino acids 157-167 renders primary porcine hepatocytes fully susceptible to HBV. These results pave the way for generating transgenic pigs with humanized porcine chimeric NTCP as a novel, fully immunocompetent infection model for developing and validating new curative HBV therapies.