Application of recombinant adenoviruses expressing glycoprotein or nucleoprotein of rabies virus to Korean raccoon dogs

A new rabies vaccine for animals, including raccoon dogs, in Korea is needed to eradicate rabies infection. In this study, we constructed two recombinant adenoviruses expressing the glycoprotein or nucleoprotein of the rabies virus (RABV). We then investigated the safety and immunogenicity of these strains in raccoon dogs, depending on inoculation route. Recombinant adenoviruses expressing the glycoprotein (Ad-0910G) or nucleoprotein (Ad-0910N) of rabies were constructed in 293A cells using an adenoviral system. One-year-old raccoon dogs underwent intramuscular (IM) inoculation or oral administration of the recombinant Ad-0910G and Ad-0910N. Clinical symptoms were observed and virus-neutralizing antibodies (VNA) against RABV were measured at 0, 2, 4, and 6 weeks after the immunization. Raccoons were considered positive if VNA titers were ≥ 0.1 IU/mL. Raccoon dogs inoculated with the combined Ad-0910G and Ad-0910N virus via the IM route did not exhibit any clinical sign of rabies during the observation period. All raccoon dogs (n = 7) immunized IM had high VNA titers, ranging from 0.17 to 41.6 IU/mL at 2 weeks after inoculation, but 70% (7/10) of raccoon dogs administered viruses via the oral route responded by 6 weeks after administration against RABV. Raccoon dogs inoculated with Ad-0910G and Ad-0910N viruses showed no adverse effects. Immunization with the combined Ad-0910G and Ad-0910N strains may play an important role in inducing VNA against RABV in raccoon dogs.