The Epstein-Barr virus open reading frame BDLF3 codes for a 100-150 kDa glycoprotein

The Epstein-Barr virus (EBV) open reading frame BDLF3 is predicted to code for a glycoprotein on the basis that it contains sequences with signal peptide and transdomain characteristics and nine potential N-linked glycosylation sites. No sequential or positional homologues of BDLF3 have been located in other herpesviruses. A bacterial glutathione S-transferase (GST)-BDLF3 fusion protein was used to demonstrate that over one-third of EBV-immune human sera tested recognized the fusion protein but not GST alone on Western blots. The fusion protein was used to raise polyclonal sera in rabbits. A BDLF3 recombinant baculovirus was constructed using the full-length BDLF3 sequence (AcBDLF3). Rabbit anti-fusion protein sera and some human EBV-immune sera recognized products of approximately 30 and 55 kDa from AcBDLF3-infected insect cells by Western blotting. A peptide representing the carboxy-terminal amino acids 215-234 of the BDLF3 sequence was used to raise anti-peptide sera in rabbits. Anti-peptide serum detected a product by indirect immunofluorescence in acetone-fixed EBV-infected B cells from all cell lines tested. A diffuse band with a molecular mass of 100-150 kDa was detected by Western blot in B95-8 cell lysates, partially purified B95-8 virus and B95-8-infected cell membranes after probing with anti-BDLF3 peptide serum. This product was shown to be glycosylated after enzymatic deglycosylation of a B95-8 virus preparation using neuraminidase, O-glycosidase or N-glycosidase F. The BDLF3 protein products have no known function.