Involvement of phosphatidylserine and non-phospholipid components of the hepatitis B virus envelope in human Annexin V binding and in HBV infection in vitro

Background/Aims: We have previously demonstrated that human liver Annexin V (hAV), a Ca2+-dependent phospholipid binding protein, binds specifically t o small HBsAg (SHBsAg), Because of the propensity of AV to bind phospholipi ds, we here examine the role of phospholipids, as component of the HBV enve lope, in binding to hAV and in HBV infection, Methods: The influence of phospholipids (phosphatidylserine and phosphatidy lcholine) on the binding of hAV to SHBsAg or to anti-hAV monoclonals was de termined by ELISA, Their influence on HBV infection was investigated using an in vitro HBV infection assay, Results: Two monoclonals, specific against hAV were able to block the bindi ng of hAV to SHBsAg and recognized different epitopes of hAV. The binding o f one of these monoclonals to hAV could be inhibited by phosphatidylserine, but not by phosphatidylcholine, Further experiments revealed that phosphat idylserine could also inhibit the binding of hAV to SHBsAg and could even p revent HBV infection in vitro, Phosphatidylcholine had no effect on the bin ding of hAV to SHBsAg and could not prevent HBV infection in vitro. However , since phosphatidylserine was not able to abolish the binding of the other blocking monoclonal to hAV a non-phospholipid component of the HBV envelop e must also be involved in hAV binding, Conclusions: These results indicate that phosphatidylserine and a non-phosp holipid component of the HBV envelope are involved in hAV binding and in HB V infection.