| Porcine Parvovirus?PPV?,an infectious cause of Porcine Parvovirus Infection?PPI?which was called by a joint name porcine viral reproductive disease,mainly caused SMEDI syndrome?stillbirth,mummification,embryonic death,and infertility?in gilts,infected pigs regardless of age and sex,and domestic or wild.At present,PPV has been known to be prevalent worldwide and is now endemic.In recent years,with the increased infection rate and morbidity,PPV has been one of the most economically important diseases of the global swine industry.Therefore,it is of important significance for the development of pig industry to have a good understand of etiological characteristics and offer valuable references for the prevention and control of PPV.Clinical samples taken from gilts and fetal porcine with suspected PPV infection were detected by PCR.When the test result was positive,sample supernatant was inoc?Lated onto ST cell for virus isolation.Finally,a new PPV strain was obtained named PPV GD-2.With the analysis of physicochemical properties of the new strain,we found it insensitive to chloroform,acid?pH3.0?and trypsin,and the tolerable temperature was 56?for 30 min.All of these were consistent with previously reports about PPV.Five pairs of oligonucleotide primers were designed according to the PPV NADL-2sequence to amplify the nearly whole genome of PPV GD-2.Then?bp sequence was obtained covering the entire coding region.In order to clarify the genetic evolution of PPV,the Bayesian Markov Chain Monte Carlo method in beast v1.8.3 and related packages were used in this study.The result of phylogenetic analysis showed that PPV GD-2 was in the nearest phylogenetic relationship with classical attenuated vaccine strain NADL-2.The average nucleotide substitution rate of PPV VP2 was calculated to be 2.3592×10-5substitution/site/year(95%HPD:1.1051×10-8,5.1334×10-5).As an ancient virus,the most recent common ancestor of PPV was originated in 1593 and had divergence in 1700s.As a new PPV strain,it was necessary to know the breeding properties after virus infection and characterization of cell culture of PPV GD-2.A specific and sensitive PPV SYBR Green?real time PCR was established with the purpose to analyze virus DNA content after PPV GD-2 infection to ST cell in different periods.We obtained the one step growth curve of the virus in vitro proliferation according to the test results.It showed that the virus began to thrive exponentially 8 hours after the virus infection,with cell lesions aggravating and gradual lysis and death of cells,16 hours later,PPV DNA content began to decrease and tended to be stable finally.In addition,the immunogenicity of PPV GD-2 was analyzed in this study by monitoring the HI antibody level of guinea pigs.As sensitive creatures,the PPV GD-2 was inoculated to guinea pigs as animal model.After inoculation,we found it had no pathogenicity in guinea pigs and could stimulate sustainable antibody.It indicated that PPV GD-2 strain had satisfied immunogenicity.In conclusion,a new strain PPV GD-2 was isolated from clinical samples taken from gilts and fetal porcine with suspected PPV infection and the new strain inherited stably in ST cell.The results of phylogenetic analysis showed it had the nearest phylogenetic relationship to the vaccine strain PPV NADL-2.When inoculated to guinea pigs,PPV GD-2 isolate showed good immunogenicity. |
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