Study on an attenuated rabies virus strain CTN181-3.

We have obtained an attenuated rabies virus CTN181-3. In this paper, we make a comprehensive studies on CTN181-3. CTN181-3 showed no pathogenicity by i. c. or o. i. inoculation in 3-week-old mice, lower pathogenic in 2-week-old mice, and no virulence by o. i. inoculation in 8-week-old golden hamsters. CTN181-3 showed high immunogenicity, which produced high level neutralizing antibodies, 100% sero-conversation and >5.0 IU/ml GMT by one dose i. m. or o. i. vaccination in mice and golden hamsters. Cellular immune response by one dose i. m. or o. i. inoculation was detected. Especially in PEP, reduced dose of vaccination resulted in 50% (one dose) and 100% (2 doses) protections in golden hamsters. Molecular basis of the attenuation indicated that eight substitutions compared to its parental virus strain CTN-1, among them the two substitutions at the G276 (Leu→Val) and L1496 (Met→Trp) were the critical attenuated site. The phenotypic and genotypic characteristics of CTN181-3 were highly stable, no reversion was occurred when the virus was multiple passaged in suckling mice brains, guinea pig submandibular glands or BSR/Vero cell cultures. The gene homology compared to the Chinese rabies isolates showed much higher than rabies vaccine strains used in China, suggesting CTN181-3 is a promising and suitable oral rabies vaccine candidate strain.