Susceptibility screening of highly pathogenic porcine reproductive and respiratory syndrome virus in several strains of minipigs / 中国比较医学杂志

Objective To screen strains of minipigs sensitive to highly pathogenic porcine reproductive and respiratory syndrome virus (HP-PRRSV) for evaluation of HP-PRRS live vaccine.Methods Lantang pigs, Juema, Bama and Wuzhishan ( white) minipigs were inoculated with virulent strain NVDC-JXA1 of PRRSV, and local binary hybrid pigs were used as control.The animals were continuously observed for 5 weeks on mental status, appetite, survival, etc.after inoculation of virus.The dead pigs were autopsied and the lung tissue samples were collected for detecting virus by RT-PCR.By the end of the experiment, serum of survival animals were collected for detecting PRRSV antibody by ELISA assay.Result The animals showed depression, anorexia, and other clinical signs and death in each group after inoculation.Meanwhile, the testing results were all positive in the RT-PCR and ELISA detection.Bama and Wuzhishan ( white) minipigs were the most sensitive to virulent strain NVDC-JXA1 of PRRSV regarding mortality rate.Conclusions Bama and Wuzhishan ( white) minipigs are sensitive to HP-PRRSV, and can be used for the inspection of HP-PRRS live vaccine.

Expression of Open Reading Frame 5 Protein of Porcine Reproductive and Respiratory Syndrome Virus Using Semliki Forest Virus Expression System

The ORF5 gene encodes a major envelope glycoprotein (GP5), which is one of the three major proteins of porcine reproductive and respiratory syndrome virus (PRRSV). The GP5 protein has been known to be a 24.5-26kDa N-glycosylated envelope protein. The GP5 is involved in inducing neutralizing antibodies. For this reason, the GP5 is primary candidate for the PRRSV subunit vaccine. To produce the native form of GP5 in mammalian cells, we have cloned the ORF5 gene from PRRSV CNV-1 into the Semliki Forest virus (SFV)-based expression vector, resulting in recombinant pSFV-ORF5. By the infection with recombinant pSFV-ORF5 to BHK-21 cells, the GP5 expression was confirmed by immunocytochemistry and immunoblotting assay. The recombinant virus particle harboring ORF5 gene was infectious to BHK-21 and MARC-145. The RNA synthesis and expression of GP5 in the infected cell was also confirmed by RT-PCR.

Seroprevalence of Antibody to Procine Reproductive and Respiratory Syndrome Virus in Diagnostic Submissions

During the period from January to December of 2001, a total of 3,391 swine sera were submitted to our laboratory from 256 farms for the diagnosis of porcine reproductive and respiratory syndrome (PRRS). The antibody to porcine reproductive and respiratory syndrome virus (PRRSV) was tested by the indirect immunofluorescent antibody (IFA) test. Of the 256 farms tested, 230 farms (89.8%) were positive for the PRRSV antibody. The overall seroprevalence of the PRRSV antibody was 52.1% (1765/3391). Most of the pigs seemed to be infected with PRRSV at around 50 to 60 days old. The seroprevalence of the antibody became higher with age, and peaked at around 100 days old. More than one-third of the adult pigs, including boars, gilts, and sows, was positive for the PRRSV antibody. The infection of PRRSV was chronic and confined to growers and/or finishers in most farms. However, the antibody was detected in all production phases at some farms.