Studies On The Difference Of PRRSV Infectious And PRRSV ADE

Porcine reproductive and respiratory syndrome (PRRS), which is caused by Porcine reproductive and respiratory syndrome virus (PRRSV), is an infectious disease characterized by breathing obstacle of piglets and abortion of pregnant sow. PRRSV genome is a single-stranded, positive-sense RNA,easy to mutate.PRRSV can induce persistent infection and immunosuppression, and has antibody-dependent enhancement effect in the process of infectious. Therefore, the study of mechanism of PRRSV infectious,especially the difference of PRRSV infectious and PRRSV ADE, has pround meaning for prevent and cure PRRS.In this study, we analysis the difference of PRRSV vaccine strain Hn-3/06 and variant strain Hn-1/06 infectious.Using real-time PCR to detect the dynamic variation of PRRSV RNA copies in serum samples, the specific antibody and IFN-αlevel were detected by ELISA method, neutralization tests were used to detect neutralization antibody titers.The results showed that the dynamic variation of PRRSV RNA copies in pigs were unity,infectious ability of variant strain was a little strong than vaccine strain.ELISA antibody and neutralization antibody appeared much later, titers lower,the first groups'ELISA antibody level higher than the second groups'. Both of the two PRRSV strains can not induce pigs generated determinable IFN-α, the results indicated that infected of PRRSV can cause immunosuppression of pigs, and immunosuppression ability of variant strain are stronger than vaccine strain.The results of second infection test showed that, no viremia emerged when homology virus infectious, and viremia can be reduced to 7 days when allotype virus infectious. PRRSV infectious can induce pigs generate immunoprotection ability, the cross immunoprotection ability of PRRSV is lower than auto immunoprotection ability. So, humoral immunity may not play the important role in the process of anti PRRSV infectious.The ADE of PRRSV infection were studied in both vitro and vivo experiments. Vitro test results showed that, all homology virus-antibodies complex, allotype virus-antibodies complex and uninfected immune complex can enhance the infectivity of PRRSV. Vivo test results proved that inoculate PRRSV vaccine to persistent infectious pigs can obviously enhanced the replication of viruses, that is contribute to reveal the mechanism of PRRSV ADE. We used mouse anti FcγRIIB serum blocked the PAM cells, to observe different concentrations of infected and uninfected immune complex's accommodate to PRRSV infectivity,in order to reveal the function of FcγRIIB in the process of PRRSV infect PAM cells.The data of selective blockade of inhibitory Fcγreceptor suggest that, the infectivity of PRRSV are enhanced no matter immune complex participate or not, and it proved that blocked inhibitory receptor can enhance the ADE ability of PRRSV, therefore, FcγRIIB can regulate PRRSV ADE. This study has significant meaning for making clear of mechanism of PRRSV ADE.