Studies On The Genetic Variation Of Canine Parvovirus Strains Isolated In Beijing Area Of China

Abstract: The evolution and variation of canine parvovirus(CPV) isolated in Beijing aera were examined.The PCR was developed on the basis of the published sequences and special-point variation,which could differentiate CPV-2,CPV-2a and CPV-2b. Type-special PCR was used to differentiate CPV-2 form CPV-2a and CPV-2b, and PCR Amplification of Specific Alleles(PASA) was used to differentiate CPV-2a from CPV-2b. A total of 31 CPV isolates from ill dogs collected form Beijing area of China were typed by type-special PCR or PASA.The point mutation in VP2 residue 297 of canine parvovirus from Ser to Ala acid was examined, which causes a alteration of the restriction enzyme AIu I site. Mutation at residue 297 in the VP2 sequence of the CPV isolated strains was examined by the PCR-based restriction fragment length polymorphism.The VP2 capsid protein genes of CPV-010 (CPV-2a) and CPV-21 (CPV-2b) strains were cloned,sequenced, and then analysed with respect to their evolutionary relationship to other CPV isolates. The partial gene sequences of the two CPVs were cloned and sequenced in order to examine their differences between tandem repeats in the 5 ' non-coding region, and compared homology with tandem repeat sequences of others parvovirus.The results of the PCR typing of CPV isolates showed CPV-2a and CPV-2b were both present in Beijing area. It was found that CPV-2 was not discovered in isolated strains, CPV-2a has 18 isolates, and CPV-2b has 13 isolates. CPV-2b was first discovered in 1997's isolates,and CPV-2b isolates were gradually increasing since 1997.The differences of VP2 residues 297 was examined, the results indicated that Ala was the predominant VP2 residue 297 of CPV-2a and CPV-2b isolates in Beijing area.The results of cloning and sequencing of VP2 gene showed the structural protein VP2 contains 1775 nucleotides, encoding 584 amino acids. There is a high homology in nucleotide sequence and amino acid sequences which were drived from the virus VP2 genomes of CPV-010, CPV-21, CPV-IM, CPV-15,CPV-N. The rate of nucleotide sequence homology is 99.38%-99.66%, and the rate of amino acid homology is 98.63%-99.83%. The results of analysis of tandem repeat sequences showed CPV-010 and CPV-21 took the same tandem repeats not only in number but also in location, with a genome homology of 99.33%.The assay showed that the evolution and variation of CPV in Beijing aera followed the same pattern observed in overseas. Phylogenetic analysis of theirs complete VP2 sequences indicated they origined from a common ancestor.