犬2型腺病毒毒株纤突蛋白基因的比较分析

根据GenBank中犬腺病毒（canine adenovirus,CAV)纤突基因序列，设计合成2对引物。用PCR方法，对犬2型腺病毒沈阳分离株（CAV-2SY株）第5代强毒（SY-V5）、经蚀斑克隆驯化的第60代毒弱毒（SY-V60）、SY-V60感犬体上传5代的回收毒（SY-CP5）、美国疫苗毒（US-V20）等4个毒株的纤突基因进行了扩增，PCR产物经纯化后进行基因序列测定，测序结果经拼接后得到1个由1629个核苷酸组成的纤突蛋白全基因序列，编码543个氨基酸。犬2型腺病毒与GenBank中的标准的CAV-2强毒株（Toronto A26/61)纤突蛋白基因序列的比较结果表明：CAV-2SY株强毒株与Tornto A26/61株相同；SY-V60株与SY-CP5相同，与驯化前的SY-V5相比，在1134位发生碱基颠换，编码的氨基酸由原来的天冬酰氨（N）变为赖氨酸（K），并导致N-X-S/T潜在糖基化位点发生改变，US-V20该部位与发生同样的突变，本试测定和比较的CAV-2强毒株有5个潜在的N-联糖基化位点，弱毒株仅有4个位点；US-V20与TorontoA26/61差异较大，有11个碱基发生变化，导致8个氨基酸的变异。

Comparative Analysis of the CAV-2 Fiber Protein Gene

The canine adenovirus-2(CAV-2) is associated with upper respiratory infection and intestinal syndroms.Adenovirus fiber protein(Fip) plays a crucial role in infection by attaching the virus to a specific cell-surface receptor.I n order to further explain the mechanism of difference in cell tropism and virul ence at molecular level,we designed 2 pairs of primers according to the publishe d CAV-2 Fip gene to amplify the Fip genes with PCR method.The Fip genes of the CAV-2 virulent strain SY-V5,attenuated SY-V60,SY-CP5(derived from SY-V60 pa ssed in susceptible dogs for 5 passages) and USA vaccine strain(US-V20) had bee n sequenced and compared with one another and with that of the standard CAV-2 T oronto virulent strain.Complete Fip gene of all CAV-2 strains were 1 629 nt and 542 amino acids.The deduced amino acid sequences of the Fip of the CAV-2 s trains were compared one another and with that of Toronto strain.Comparing with SY-V5 and Toronto strains,there are point mutation(transversion) occurring in S Y-V60 and SY-CP5 which changes the potential site for asparagine-linked glyco sylation.