The Study on Safety and Immunogenicity of the Live Attenuated Canine Distemper Virus Vaccine for Ailurus
Seventeen Ailuruses were vaccinated with the live attenuated canine distemper virus (CDV) vaccine derived from CDV/R-20/8 strain. During the period 30 days,sixteen Ailuruses did not develop clinical signs of canine distemper(CD).On the 20th day post-vaccination,one Ailurus developed suspicious clinical signs of CD,such as fever,cough,conjunctivitis and so on.After three days,this animal was agonized and euthanized,appearing lobular pneumonia by histopathological examination.CDV-like particles were seen under electron microscope.CDV H gene was amplified by RT-PCR from the liver of the Ailurus and sequenced.Its nucleotide homologies to the CDV/R-20/8 strain,the Onderstepoort and the Convac vaccine strain, the A75/17 virulent strain were 99.7%,96.5% and 91.9% respectively.Its amino acid sequence homologies to the above virus strains were 95.5%,95.6% and 91.0% respectively.And it had seven N-linked glycosylation sites like the Convac vaccine strain,but did not have N-linked glycosylation sites in amino acids 309-311 existing in virulent strains.The results demonstrated that CDV isolated from Ailurus was closest to CDV/R-20/8.It is relevant to CDV/R-20/8 that the Ailurus developed to CD after inoculation with CDV vaccine.Serum neutralizing antibody (SN) titers of the sixteen Ailuruses against CDV were tested,which were below 1∶4 prior to vaccination and were all beyond 1∶128 30 days post-immunization.It indicated that the CDV/R-20/8 vaccine strain had better immunogenicity for Ailurus.