The Effects Of PCV2for Myd88-NF-κB Signal Pathway In Piglet’s Liver

Porcine circovirus type2(PCV2), the primary pathogen of porcine circovirus disease (PCVD), can lead to acute phase response(APR) and dramatic changes of acute phase proteins(APPs) in the liver and sera. Based on replicating piglet PCV2infection model, we researched on myeloid differentiation factor88(MyD88), nuclear factor kappa B (NF-κB) and its related proteins in the piglet liver, then explored the relationship between MyD88-NF-kappa B signaling pathways and APPs. Our study will provide a theoretical basis for the pathogenesis and prevention of PCVD in the clinical.Thirty one piglets which were free of PCV2and PRRSV antibody and antigen were chosen as the experiment animals, randomly distributed in two groups:the control group (n=16), the experiment group (n=15). Every piglet in experiment group was inoculated with PCV2, and the livers were collected at0day-post-infected(DPI) from4piglets of control group, then preserved at-80℃. At14DPI, livers were collected from4piglets of control group and5piglets of experiment group. At21and35DPI, the method were adopted as same as before. The nucleus and cytoplasm protein were extracted from liver tissues. The protein level of p65in nucleus, phosphorylation-IκBa and MyD88in cytoplasm were detected by Western blot, and NF-κB DNA binding activity were detected by electrophoretic mobility shift assay (EMSA). The results of Western blot showed that nucleus NF-κB/p65protein content were significantly higher on day14and21post infection than on day0, and significantly increased (P<0.05) when compared with control group on the same DPI. It increased along with time and reached a peak on the21DPI, then attack at35DPI. The results of EMSA showed that the NF-κB DNA binding activity had similar result with NF-KB/p65. The results of Western blot showed that phosphorylation-IκBa increased first then decreased with time, at21DPI significantly increased(P<0.05), and there was no change on other DPI. The tendency of MyD88was same with NF-κB/p65. All results explained that PCV2can activite NF-κB by MyD88; then degradation of IκBα phosphorylation made NF-κB nucleus translocation. After NF-κB binding with DNA, it can regulate assistance cytokine transcription and expression.Our laboratory once mensured the APP mRNA in liver by RT-PCR and APPs concentration in sera by ELISA. Compared them with this experiment, and made use of correlation analysis. The results were as follows:correlation between MyD88and NF-κB/P65(P<0.05), correlation coefficient was0.566, indicating that MyD88was an important mediator which activated NF-κB/P65signaling pathway. Between NF-κB/P65and SAA, Pig-MAP correlation were existed(P<0.05), correlation coefficients were0.669and0.471. Between NF-κB/P65and CRP, AAQ HP, ApoA-I, there was no correlation (P>0.05),they shows NF-κB/P65made a role of regulating the SAA, Pig-MAP of production. MyD88、p-IκBa and liver APPs mRNA and serum APPs analysis results show there was no correlation between them (P>0.05), correlation was not significant The results indicated MyD88、p-IκBa can regulate APPs production through NF-κB signal pathway.