| A model of peripheral blood monocyte-derived macrophages(MDMs)infected with PRRSV was established by gene cloning,cell culture,cellular immune and fluorescence quantitative RT-PCR.Susceptibility of Jiangsu native pig breeds(Meishan pig,Erhualian pig,Suzhong pig and Jiangquhai pig)on PRRSV was evaluated.Association of cytokine IL-8,IL-10 and TNF-a with swine PRRSV susceptibility was studied.It aimed to provide theoretical base for breeding PRRSV resistance pigs and promot mining and using of germplasm resources of Chinese native pig breeds.1 The model of peripheral blood monocyte-derived macrophages(MDMs)infected with PRRSVPRRSV NJGC strain was inoculated PAMs and MDMs cells.PRRSV replication in both cells after inoculation was detected by fluorescence quantitative PCR,and virus titer of the supernatant was determined.The results showed that,the viral load in cells reached the highest value,at 12 h after PAMs and MDMs cells was infected PRRSV in vitro,and then fell rapidly.Virus titer of PAMs and MDMs cell supernatant reached plateau phase at 12～24 h,and then turned to the decline phase.This suggested that PRRSV growth trend in PAMs and MDMs cell was the same,which proved the feasibility of the model of MDMs infected with PRRSV,it laid a foundation for studying susceptibility of PRRSV to different pig breeds.2 Evaluation of the PRRSV susceptibility of Jiangsu and Anhui native pig breedsPRRSV replication of MDMs cell in Jiangsu native pig breeds was detected by fluorescence quantitative RT-PC at different time points.Meanwhile,viral titers of the supernatant were also determined.The results showed that,PRRSV replication of MDMs cell in different pig breeds had the same growth tendency.Viral load reached a peak at 12 h,then declined rapidly at 12～18 h.Virus tite of MDMs cell supernatant performed the same trend in various breeds,reached plateau phase at 12～24 h,and then turned to the decline phase.The viral load at 12 h post infection:Meishan pig>Erhualian pig>Suzhong pig>Jiangquhai pig.And viral load of Erhualian pig was significantly higher than that of Jiangquhai pig(P<0.01).The supernatant viral titer of Jiangquhai pig was less than that of Meishan pig and Suzhong pig at 12 h.From the above can be showed that Jiangquhai pig was the relative low susceptible breed to PRRSV.Meishan and Erhualian pig may be the relative high susceptible breeds to PRRSV.3 Cytokine expressions in MDMs infected with PRRSV and the association with PRRSV susceptibilitymRNA expressions of cytokine IL-8,TNF-α and IL-10 in MDMs infected PRRSV at different time points were detected by fluorescence quantitative RT-PCR.The results showed that IL-8 mRNA expression of Jiangquhai pig was significantly higher than that of other three breeds(P<0.05)before or after infected PRRSV.IL-8 mRNA expression of Suzhong pig was significantly higher than that of Erhualian and Meishan pig before PRRSV inoculation and at 24 h after inoculation(P<0.01).These results showed that PRRSV can induce the IL-8 expression.High level IL-8 may inhibit the PRRSV replication in MDMs.TNF-α expression of MDMs in Meishan pig,Suzhong pig and Jiangquhai pig decreased at 0～6 h after infected PRRSV and then rose at 6～12 h.TNF-αexpression of Jiangquhai pig as a low-susceptible breed was always at high level.IL-10 expression of four native pig breeds decreased at 0～6 h after PRRSV inoculation and then rose afterwards.IL-10 expression in Jiangquhai pig at was significantly higher than that in Erhualian pig at 6～36 h after inoculation(P<0.05).TNF-a and IL-10 expression of Jiangquhai pig as a low-susceptible breed were at high level.These results conjectured that cytokine TNF-a and IL-10 can influence the replication of PRRSV in MDMs.In summary,the study found a model of peripheral blood monocyte-derived macrophages(MDMs)infected with PRRSV,and determined the viral load in MDMs at 12h post infection as the evaluation index of susceptibility to PRRSV,based on that Jiangsu native pig breeds was evaluated.Meanwhile,the expressions of three cytokines were also determined.The results indicated that Jiangquhai pig was the relative low-susceptible breed to PRRSV,Erhualian and Meishan pig were the relative high-susceptible breeds to PRRSV,and IL-8,IL-10 and TNF-a expression in Jiangquhai pig MDMs was higher than that of Erhualian and Meishan pigs,which laid the foundation for breeding PRRSV resistance pigs. |
