Immunogenicity of ORFV-based vectors expressing the rabies virus glycoprotein in livestock species

The parapoxvirus Orf virus (ORFV) encodes several immunomodulatory proteins (IMPs) that modulate host-innate and pro-inflammatory responses and has been proposed as a vaccine delivery vector for use in animal species. Here we describe the construction and characterization of two recombinant ORFV vectors expressing the rabies virus (RABV) glycoprotein (G). The RABV-G gene was inserted in the ORFV024 or ORFV121 gene loci, which encode for IMPs that are unique to parapoxviruses and inhibit activation of the NF-κB signaling pathway. The immunogenicity of the resultant recombinant viruses (ORFV^∆024RABV-G or ORFV^∆121RABV-G, respectively) was evaluated in pigs and cattle. Immunization of the target species with ORFV^∆024RABV-G and ORFV^∆121RABV-G elicited robust neutralizing antibody responses against RABV. Notably, neutralizing antibody titers induced in ORFV^∆121RABV-G-immunized pigs and cattle were significantly higher than those detected in ORFV^∆024RABV-G-immunized animals, indicating a higher immunogenicity of ORFV^Δ121-based vectors in these animal species.