Isolation And Identification Of Strains Of PRRSV HuB1 And Research Of Glycyrrhizic Acid In Vitro Anti-PRRSV Infection

Porcine reproductive and respiratory syndrome(PRRS) is a serious infectious disease of swine which is caused by porcine reproductive and respiratory syndrome virus(PRRSV).It is characterized by severe reproductive failure in sows and respiratory distress in piglets and growing pigs.Since it' s first reported in the United States in 1987,it has been spread to most countries and caused large economically lost. In China a highly pathogenic disease which is characterized by high-fever, high morbidity and mortality rate was outbreaked in the South in 2006, and then spread quickly to surrounding areas, to 2007, it had been all over most provinces in my country.Now Most experts believe that PRRSV is induced by a variation of the highly pathogenic strain of PRRSV, and other pathogenic micro-organisms mixing infections and high temperature and high humidity conditions.1 In this study, porcine reproductive and respiratory syndrome virus isolated by Marc-145 cells from a pig farm of Hubei province, where pigs were infected with porcine reproductive and respiratory syndrome virus in 2006, named HuBl.2 Using RT-PCR, IFA, the isolated strains were identified, and by Marc-145 cells, the proliferation of the virus were completed, the measurement of TCID50 and identification of physical and chemical properties.3 By comparison of PRRSV HuBl strain ORF5 sequence with PRRSV strain, finding that it was 85.6-99.5% homo logy with standard strain and other strains, it was demonstrate to be PRRSV.4 By using RT-PCR methods and nucleotide sequencing it was proved that PRRSV HuBl strain NSP2 gene was molecular characteristics of variant PRRSV strains.5 by Nano-based glycyrrhizin interaction with PRRSV in vitro, researchers demonstrated that nano-based glycyrrhizic acid has the ability of anti-PRRSV-infected cells, and with the reduction of the virus TCID50 its effective role of the concentrations decreased in a dose-dependent. The half effective inhibitory concentration of Nano-based glycyrrhizin was: PRRSV 105TCID50,174μg/ml; PRRSV 104TCID50,141μg/ml; PRRSV 103TCID50, 37.9μg/ml; PRRSV 102 TCID50,8.84μg/ml.6 Using fluorescence quantitative PCR method, a preliminary proof of Nano-based glycyrrhizin does not damage the RNA of PRRSV, it may damage envelope protein of the virus, or binding with the envelope protein of virus, blocking viral envelope with the host cell specificity of the ligand combination, so that PRRSV can not be adsorbed on the surface of the host cell membrane, so that PRRSV has lost the ability to infect host cells.