The Role Of Several Host Factors In Porcine Circovirus Type 2 Infection

Porcine circovirus type 2 causes Porcine circovirus diseases or Porcine circovirus-associated diseases(PCVD/PCVAD),which seriously affects the global pig industry.PCV2 infection,such as attachment,disassembly,replication,assembly,and release,mainly depends on host factors.Therefore,researches on the roles of host factors in the viral infection process is expected to elucidate the pathogenic mechanism of the virus.Based on the RNA-Seq analysis results of PCV2 infected PK-15 cells,we screened host factors that might involve in PCV2 infection in the present study.As a result,18 differential expressed genes were screened,including 12 up-regulated genes and 6 down-regulated genes.Meanwhile,RT-qPCR method was used to verify these results and found that the levels of mRNA of HMGB2,CLDN6,TNFSF4,THBS1,and IFNGR1 genes were similar to the RNA-Seq results,while the expression of BCL2L11 gene is opposite to the result of RNA-Seq.Among the 12 up-regulated genes,the levels of mRNA of IL23 A,SAA2,CD40,CCL3L1,CCL4,STAT2,OASL,and ISG15 was similar to RNA-Seq results,and the expression levels of IL6,IRF1,CXCL10,and IL28 were opposite to RNA-Seq results.The upstream regulators of 3-hydroxy-3-methylglutaryl-coenzyme A reductase are adenosine 5'-monophosphate-activated protein kinase(AMPK)and protein phosphatase 2A(PP2A),which regulates HMGCR activity by phosphorylation and dephosphorylation of serine at position 872 of HMGCR,respectively.We previously found that PCV2 promotes the level of HMGCR phosphorylation,thereby promoting PCV2 proliferation at the early stages of PCV2 infection,but the mechanism through which HMGCR regulates PCV2 infection has not been elucidated.Transcriptomics analysis revealed that AMPK was up-regulated during PCV2 infection,but no difference in PP2 A.Therefore,we proposed that AMPK mainly regulates HMGCR activity during PCV2 infection.Here,Western blotting,co-immunoprecipitation and other methods were performed to verify this hypothesis.The results showed that PCV2 infection promoted AMPK and PP2 A activity and inhibited HMGCR activity.In early PCV2 infection,AMPK played a major role in regulating HMGCR activity,while PP2 A has little effect on HMGCR activity.Besides,the results of Co-IP experiments further confirmed that HMGCR interacts with the Cap and Rep proteins of PCV2.Myeloid cell nuclear differentiation antigen-like protein(MNDAL)is a member of the interferon-induced proteins P200 family.P200 family proteins are involved in various viral infections,but whether MNDAL affects PCV2 infection has not been reported.Transcriptomics results revealed that PCV2 promoted MNDAL gene expression,therefore,MNDAL was further evaluated in this study.The role of MNDAL in PCV2 infection was studied by constructing a stable expression porcine MNDAL cell line.The results showed that overexpression of MNDAL significantly promoted PCV2 proliferation,and MNDAL inhibited apoptosis of PK-15 cells during PCV2 infection.In summary,the PCV2 infection is regulated by a variety of host factors.Therefore,studying the role of host factors in the PCV2 infection is helpful to understand the pathogenic mechanism of PCV2 and provide new ideas for antiviral therapy.