A bovine herpesvirus 1 (BoHV-1) defective in glycoprotein E (gE) was constructed from
a Brazilian genital BoHV-1 isolate, by replacing the full gE coding region with the
green fluorescent protein (GFP) gene for selection. Upon
co-transfection of MDBK cells with genomic viral DNA plus the
GFP-bearing gE-deletion plasmid, three fluorescent recombinant
clones were obtained out of approximately 5000 viral plaques. Deletion of the
gE gene and the presence of the GFP marker in
the genome of recombinant viruses were confirmed by PCR. Despite forming smaller
plaques, the BoHV-1△gE recombinants replicated in MDBK cells with similar kinetics
and to similar titers to that of the parental virus (SV56/90), demonstrating that the
gE deletion had no deleterious effects on replication efficacy in
vitro. Thirteen calves inoculated intramuscularly with BoHV-1△gE
developed virus neutralizing antibodies at day 42 post-infection (titers from 2 to
16), demonstrating the ability of the recombinant to replicate and to induce a
serological response in vivo. Furthermore, the serological response
induced by recombinant BoHV-1△gE could be differentiated from that induced by
wild-type BoHV-1 by the use of an anti-gE antibody ELISA kit. Taken together, these
results indicated the potential application of recombinant BoHV-1 △gE in vaccine
formulations to prevent the losses caused by BoHV-1 infections while allowing for
differentiation of vaccinated from naturally infected animals.