| The disease of porcine parvovirus (PPV) is caused by porcine parvovirus which is a major cause of reproduction failure in swine. Parvovirus infections in pigs may cause fetal death and mummification, still births and other reproductive failures in pregnant sows, and dermatitis and diarrhea in piglets. Since PPV was isolated by Carwright in 1967, the virus and it's antibody were proved to be positive in many countries, and the antibody positive rate of PPV reaches to 50%~80%. In china, the antibody positive rate of PPV was up to 80%, which causes lots of economical losses in swine production. In present study, the proliferous properties of PPV in porcine kidney (PK-15) cells, inhibitory effects of nitric oxide and different selenium sources on PPV infection in vitro, the pathogenicity of different strain of PPV and their rule of variation were studied, which provided theoretic and technological base of prevention and treatment in the disease. Apart from these, the safety and effective DNA vaccination was developed. The research contents are as follows.1. Some proliferation properties of three strains of PPV in PK-15 cells were studied by using the immunofiuorescence technique. The results suggested that the three strains had the similar characteristics of the multiplication. The location of virus was observed in cytoplasm at 12 h post-inoculation, followed by a highest production at 48 h after inoculation. Then the viral particles inside host cells began to reduce and caused host cells to crack, and the particles released from the cells. Based on the results, the one-step growth curve of cells was drawn, which showed that the viral titers were reached to the highest level at 60 h post-inoculation, subsequently the viral concentration began to decrease.2. Inhibitory effects of NO and different selenium sources on PPV infection on PK-15 cells were studied. The result showed that production of NO was effectively induced when the cultures were treated with S-nitroso-N-acetylpenicllamine (SNAP) or L-Arginine, and the replication of PPV on PK-15 cellswas significantly inhibited by the addition of these materials, which have a dose-dependent manner. The anti-PPV effects of L-Arginine could be blocked by the addition of NG-nitro-L-Arginine. Higher level of inhibition of viral production was also obtained when pretreated with SNAP 6 h and 3 h before infection than added 3 h and 6 h after infection. Inhibitory effects of different selenium sources (Sodium selenite, DL-Selenomethionine and Kappa-selenocarrageenan) on PPV infection in vitro on the PK-15 cells were also studied. In addition, the influences of Glutathione reduced (GSH) and D-Mannitol on antiviral effects of selenium were carried out on PK-15 cells. The results showed that all the three kinds of selenium sources have inhibitory effects on the PPV replication in vitro. Among them, DL-Selenomethionine had the highest inhibitory effects, the lowest was the Kappa-selenocarrageenan, and they also produced a concentration-dependent manner. The GSH and D-Mannitol have the ability to increase the antiviral effects of Selenium. The antiviral effect was enhanced obviously with the addition of GSH and D-Mannitol together.3. In order to investigate the pathogenicity of different strain and rule of variation of PPV, VP2 gene of NJ-1 strain, NJ-2 strain, 7909 strain and Vaccine strain of PPV were amplified by PCR, and cloned into pGEM-T Easy respectively and sequenced. Then the differences of these sequences were compared. Among the four sequences, NJ-1 strain, NJ-2 strain, 7909 strain were all 1438 bp, which all encode 476 Aa. The vaccine strain was 657 bp, encoding 219 Aa, which was 781 bp shorter than other strains. The four sequences with NADL-2 strain, Kresse strain, China strain and VR-1 strain coming from GenBank were compared. The nucleotide sequence homologies were 97.7%-99.9% and the amino acid homologies were 97.7%~99.2%. By analysis of phylogenetic tree, it was found that the sequenced strains have higher homology with China strain, but have lo...
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