Studies On The Immune Regulation Of CGAS-STING-STAT6 Pathway In Response To PCV2 Invasion

PCV2 is a circular small DNA virus,which is the main pathogen of the Postweaning Multisystemic Wasting Syndrome.Besides,It caused a number of disease such as Porcine Dermatitis Nephropathy Syndrome、Proliferation Necrotizing Pneumonia、Porcine Reproductive Respiratory Syndrome and infectious congenital tremors in piglets.At present,PMWS is pandemic in the world wide and caused a great losses in each of country.PCV2 mainly infected the immune system,which is able to long-term exist in the monocytes.tissue cells and thymus macrophages.PCV2 infection can lead to a strong immune suppression.The number of B cells and T cells(mainly CD4+and CD8+)is significantly decreased after PCV2 infection,which can result in T cell immune response damage,e.g.IL28 and IFN-γ expression is significantly reduced in PCV2 positive porcine cells.Although the mechanism of PCV2 infection-induced immune response has been widely studied,how PCV2 escape the recognition and cytotoxicity of immune system is still unknown.In this dissertation,we explored the immune evasion of PCV2 in ST cells.Our data found that PCV2 can be recognized by DNA immune pathways leading to the downstream cascade of effects.Antiviral factor STAT6 is a significantly increased following PCV2 infection.We demonstrate that PCV2 has ability to escape from the surveillance under the innate immune DNA and RNA pathways.Especially we find that PCV2 is able to inhibit the phosphorylation of IRF3,which is the active form for the protein.IRF3 is a transcription factor that activates the type I interferon expression upon viral infection.Meanwhile,it can inhibit the phosphorylation of STAT6 downstream the related pathways.We demonstrate that the anti-PCV2 ability of STAT6 through construction of PK-15 cell line which the stat6 gene has been knocked out by the CRISPR/Cas9 technology.In addition,we successfully obtained the ORF3 knockout PCV2 strain based on the CRISPR/Cas9 technology.Our studies reveal the possible mechnisms involved in PCV2 infection and evasion,and provide a novel direction for making effective vaccines.