Expression of bovine viral diarrhoea virus glycoprotein E2 by bovine herpesvirus-1 from a synthetic ORF and incorporation of E2 into recombinant virions

Expression cassettes containing the codons for the pestivirus E-ms signal p eptide (Sig) followed by a chemically synthesized ORF that encoded the bovi ne viral diarrhoea virus (BVDV) strain C86 glycoprotein E2, a class I membr ane glycoprotein, were constructed with and without a chimeric intron seque nce immediately upstream of the translation start codon, and incorporated i nto the genome of bovine herpesvirus-l (BHV-1), The resulting recombinants, BHV-1/SigE2(syn) and BHV-1/SigE2(syn)-intron, expressed comparable quantit ies of glycoprotein E2, and Northern blot hybridizations indicated that the presence of the intron did not increase significantly the steady-state lev els of transcripts encompassing the SigE2(syn) ORF. In BHV-1 /SigE2(syn)-in fected cells, the 54 kDa E2 glycoprotein formed a dimer with an apparent mo lecular mass of 94 kDa, which was further modified to a 101 kDa form found in the envelope of recombinant virus particles. Penetration kinetics and si ngle-step growth curves indicated that the incorporation of the BVDV E2 gly coprotein in the BHV-1 envelope, which apparently did not require BHV-1-spe cific signals, interfered with entry into target cells and egress of progen y virions. These results demonstrate that a pestivirus glycoprotein can be expressed efficiently by BHV-1 and incorporated into the viral envelope. BH V-1 thus represents a promising tool for the development of efficacious liv e and inactivated BHV-1-based vector vaccines.