Species specificity for HBsAg binding protein endonexin II

Background/Aims: Hepatitis B virus displays a distinct species and tissue tropism, Previously we have demonstrated that a human liver plasma membrane protein,vith a molecular weight of approximately 34 kiloDalton specifically binds to HBsAg. This protein was identified as endonexin II, a Ca2+ dependent phospholipid binding protein. Methods: Using a mouse monoclonal antibody, directed against the HBsAg binding epitope on human endonexin II, liver tissue from various nonhuman species, human liver tissue and some extrahepatic human tissues were screened for the presence of endonexin II. Results: Endonexin II was detectable in human, chimpanzee and rhesus monkey liver and in all tested extra-hepatic human tissues, using western blot and inmunohistochemical techniques, In rat, mouse, cow and pig liver tissues endonexin II could not be detected with the antibody. Conclusions: The species specific distribution of the HBsAg binding protein endonexin II apparently correlates with the species tropism of hepatitis B virus. Furthermore, the detection of HBV-DNA, RNA transcripts and antigens in a variety of tissues in chronic infected patients, is in agreement with the wide distribution of the HBsAg binding endonexin II in various tissues.