犬瘟热减毒疫苗对小熊猫安全性与免疫原性研究

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.