In vitro binding properties of the hepatitis delta antigens to the hepatitis B virus envelope proteins: potential significance for the formation of delta particles.
To investigate the possible existence of (a) reactive binding site(s) on the hepatitis B surface antigen (HBsAg) for the hepatitis delta antigen (delta Ag) in the hepatitis delta virus (HDV), we performed binding studies using recombinant (rec)Small, recMiddle, recLarge HBsAg and recombinant small (S) and large (L) hepatitis delta antigen (recS delta Ag, recL delta Ag). Rec delta Ag was immobilized onto microtiter plates and incubated with recSmall, recMiddle and recLarge HBsAg. Of the three HBsAg proteins only the recMiddle HBsAg was found to bind to recS delta Ag. This binding was inhibited by the addition of synthetic PreS2 peptide but not by small HBsAg, indicating that the S delta Ag exhibits a PreS2 binding site. RecL delta Ag bound to all three forms of HBsAg. The binding of the HBsAg to recL delta Ag was saturable and could be blocked with an excess of HBsAg, but not with BSA. The region of the additional 19 amino acids of the L delta Ag is therefore responsible for the creation of the small HBsAg binding site on the L delta Ag. We therefore suggest that all HBsAg proteins but particularly the small HBsAg in the HDV coat seem to be involved in the interaction with the HDV core particle and that the PreS2 region of the middle HBsAg plays a crucial role in binding to small delta Ag during HDV particle formation, probably to increase the stability of the HDV particle.
de Bruin
W
W
Division of Gastro-intestinal and Liver Diseases, University Hospital of Nijmegen, The Netherlands.
Leenders
W
W
Kos
T
T
Yap
S H
SH
D000956:Antigens, Viral / Q000032:analysis / Q000235:genetics / Q000378:metabolism*; D016367:Baculoviridae / Q000235:genetics; D001665:Binding Sites; D002460:Cell Line; D004797:Enzyme-Linked Immunosorbent Assay; D006514:Hepatitis B Surface Antigens / Q000235:genetics / Q000378:metabolism*; D003698:Hepatitis Delta Virus / Q000235:genetics / Q000378:metabolism*; D035923:Hepatitis delta Antigens; D011485:Protein Binding; D011498:Protein Precursors / Q000378:metabolism*; D011869:Radioligand Assay; D011993:Recombinant Fusion Proteins / Q000032:analysis / Q000235:genetics / Q000378:metabolism; D014759:Viral Envelope Proteins / Q000378:metabolism*
D000956:Antigens, Viral; D006514:Hepatitis B Surface Antigens; D035923:Hepatitis delta Antigens; D011498:Protein Precursors; D011993:Recombinant Fusion Proteins; D014759:Viral Envelope Proteins; C442244:hepatitis delta virus large antigen; C050807:presurface protein 2, hepatitis B surface antigen