Involvement of phosphatidylserine and non-phospholipid components of the hepatitis B virus envelope in human Annexin V binding and in HBV infection in vitro.
OBJECTIVE
We have previously demonstrated that human liver Annexin V (hAV), a Ca2+-dependent phospholipid binding protein, binds specifically to small HBsAg (SHBsAg). Because of the propensity of AV to bind phospholipids, we here examine the role of phospholipids, as component of the HBV envelope, in binding to hAV and in HBV infection.


METHODS
The influence of phospholipids (phosphatidylserine and phosphatidylcholine) on the binding of hAV to SHBsAg or to anti-hAV monoclonals was determined 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 binding of hAV to SHBsAg and recognized different epitopes of hAV. The binding of one of these monoclonals to hAV could be inhibited by phosphatidylserine, but not by phosphatidylcholine. Further experiments revealed that phosphatidylserine could also inhibit the binding of hAV to SHBsAg and could even prevent HBV infection in vitro. Phosphatidylcholine had no effect on the binding 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 envelope must also be involved in hAV binding.


CONCLUSIONS
These results indicate that phosphatidylserine and a non-phospholipid component of the HBV envelope are involved in hAV binding and in HBV infection.
De Meyer
S
S
Department of Liver and Pancreatic Diseases, University Hospital Gasthuisberg, Catholic University Leuven, Belgium.
Gong
Z
Z
Depla
E
E
Maertens
G
G
Yap
S H
SH
D017304:Annexin A5 / Q000187:drug effects / Q000276:immunology / Q000502:physiology*; D000911:Antibodies, Monoclonal / Q000494:pharmacology; D000918:Antibody Specificity; D001667:Binding, Competitive; D002478:Cells, Cultured; D006514:Hepatitis B Surface Antigens / Q000235:genetics / Q000378:metabolism*; D006515:Hepatitis B virus / Q000235:genetics / Q000502:physiology*; D006735:Horseradish Peroxidase / Q000378:metabolism; D006801:Humans; D008099:Liver / Q000166:cytology* / Q000502:physiology / Q000821:virology; D010713:Phosphatidylcholines / Q000494:pharmacology / Q000502:physiology; D010718:Phosphatidylserines / Q000494:pharmacology / Q000502:physiology*; D011485:Protein Binding; D012333:RNA, Messenger / Q000235:genetics; D011994:Recombinant Proteins / Q000378:metabolism; D012441:Saccharomyces cerevisiae
D017304:Annexin A5; D000911:Antibodies, Monoclonal; D006514:Hepatitis B Surface Antigens; D010713:Phosphatidylcholines; D010718:Phosphatidylserines; D012333:RNA, Messenger; D011994:Recombinant Proteins; D006735:Horseradish Peroxidase