A prime-boost immunization strategy with DNA and recombinant baculovirus-expressed protein enhances protective immunogenicity of glycoprotein D of equine herpesvirus 1 in naive and infection-primed mice

The immunogenicity and protective efficacy afforded by intramuscular inoculation of plasmid DNA encoding equine herpesvirus 1 (EHV-1) glycoprotein D (gD) followed by EHV-1 go expressed by a recombinant baculovirus was assessed in a murine model of EHV-1 respiratory infection. Compared with mice inoculated with DNA or protein only, mice inoculated with the combination of go DNA and protein had enhanced ELISA and neutralizing antibody titres to EHV-1 and had accelerated clearance of virus from lungs following challenge infection. The enhanced protective effects of this consecutive immunization were also evident in mice which had a previous infection with EHV-1 and had pre-existing antibodies. The T-helper 1 (Th1) type of immune response induced by EHV-1 go DNA was maintained after the protein boost, despite the go protein alone appearing to direct a Th2 response. (C) 2000 Elsevier Science Ltd. All rights reserved.