Phylogenetic Analysis Of Orf Virus Luan Strain And The Impact Of Innate Immune Gene Expression In Host Induced By ORFV

Orf is an acute,contact zoonotic infectious disease caused by ORFV(Orf virus,ORFV),which belongs to the genus Parapoxvirus of Poxviridae.The disease is highly contagious and epidemic in groups.At present,infection has been reported in different parts of the world.However,there is still little information on the genetic and evolutionary characteristics of ORFV molecules.In addition,the host's innate immune response to ORFV infection is still largely unclear.Therefore,in order to enrich the molecular genetic characteristics of ORFV in Anhui province and the natural immune response after infection,this study conducted a series of studies.In this study,PCR,cell culture,electron microscopy and immunohistochemistry were used to confirm that caused by ORFV that a suspected Orf infection in a sheep farm in Lu'an City,Anhui Province in 2018 and named AH/LA/2018 strain.The B2L and F1L genes were cloned,amplified and sequenced,and the genetic evolutionary tree was constructed.At the same time,the isolate strain was determined by TCID50,the artificial infection animal test was carried out.Real-time fluorescence quantitative PCR was used to systematically analyze the expression of natural immune-related genes in peripheral blood mononuclear cells(PBMC)of goats infected with ORFV in different time periods.The results showed that the nucleotide(nt)and amino acid(aa)of B2L gene of ORFV AH/LA/2018 had 96.1%-99.8%and 96.4%-99.7%homology with other ORFV strains,respectively.The phylogenetic tree showed that ORFV AH/LA/18 strain was close to Nantou strain.The nucleotide and amino acid sequence analysis of F1L gene showed that the homology between ORFV AH/LA/2018 strain and other ORFV strains was 96.3%-99.6%and 95.6%-100%,respectively.The phylogenetic tree showed that it was closest to SDLC and SDTA strains.In addition,ORFV infection could significantly induce the expression of IFN-? and IFN-? mRNA in peripheral blood mononuclear cells and enhance the production of inflammatory cytokines,including IL-1?,IL-6,IL-8,TNF-?.At the same time,it can also induce the activation of STAT3,a key cytokine in JAK/STAT signaling pathway,and the increased expression of some antiviral protein genes,such as IFITM 1,ISG 15 and ISG20.It is worth noting that ORFV infection can up-regulate the expression of Toll-like receptors TLR-2,TLR4,TLR8,TLR9 and the key molecules cGAS,DDX41 and STING genes in STING pathway.In summary,this study is the first systematic genetic evolution analysis of Anhui Luan isolates of ORFV,the results will contribute to a better understanding of the molecular genetic characteristics of ORFV and early prevention and control of the spread of ORFV.At the same time,studies have shown that the early stage of ORFV infection may activate innate immune response in the host by relying on TLR2/4/8/9 and STING pathway.In order to induce the production of a variety of cytokines and downstream key antiviral protein expression for defense.The results provide new insights into the interaction between ORFV and host and its pathogenesis.