No abstract

The bovine herpesvirus 1 (BHV-1) recombinants BHV-1/eG ori and BHV-1/eG syn were isolated after insertion of expression cassettes which contained either a genomic RNA-derived cDNA fragment (BHV-1/eG ori ) or a modified, chemically synthesized open reading frame (ORF) (BHV-1/eG syn ), which both encode the attachment glycoprotein G of bovine respiratory syncytial virus (BRSV), a class II membrane glycoprotein. Northern blot analyses and nuclear runoff transcription experiments indicated that transcripts encompassing the authentic BRSV G ORF were unstable in the nucleus of BHV-1/eG ori -infected cells. In contrast, high levels of BRSV G RNA were detected in BHV-1/eG syn -infected cells. Immunoblots showed that the BHV-1/eG syn -expressed BRSV G glycoprotein contains N-and O-linked carbohydrates and that it is incorporated into the membrane of infected cells and into the envelope of BHV-1/eG syn virions. The latter was also demonstrated by neutralization of BHV-1/eG syn infectivity by monoclonal antibodies or polyclonal anti-BRSV G antisera and complement. Our results show that expression of the BRSV G glycoprotein by BHV-1 was dependent on the modification of the BRSV G ORF and indicate that incorporation of class II membrane glycoproteins into BHV-1 virions does notnecessarily require BHV-1-specific signals. This raises the possibility of targeting heterologous polypeptides to the viral envelope, which might enable the construction of BHV-1 recombinants with new biological properties and the development of improved BHV-1-based live and inactivated vector vaccines.