Goose RIG-I Functions In Innate Immunity Against Newcastle Isease Virus Infection

Newcastle disease is a highly contagious and fatal viral disease affecting most species of birds.Because chickens are the most susceptible birds, the disease is frequently responsible for devastatinglosses in poultry. This avian disease is caused by Newcastle disease virus (NDV)，NDV is classifiedas a member of the order Mononegavirales, family Paramyxoviridae, subfamily Paramyxovirinae.Pattern recognition receptors could recognize viral nucleic acids, then immediately initiatesignaling pathways that lead to the synthesis of multiple cytokines including type I interferon andinflammatory cytokines. They play important role in antiviral innate immunity. RIG-I like receptorsare cytoplasmic RNA helicases (including RIG-I, MDA5, LGP2), and they mainly responsible forrecognition of RNA viruses. RIG-I is essential for the recognition of a series of ssRNA viruses, whichinclude NDV.Geese are important agricultural animals, which have naturally high resistance to NDV, but thereis little research about its antiviral innate immunity, and whether there are RLRs in geese are notcleare. In this research, we firstly cloned the RIG-I gene and MDA5gene, and we transfected gooseRIG-I into HEK-293T and DF1cells to find its response to NDV infection. We also tested theexpression changes of endogenous RIG-I after infected with NDV to get a comprehensive evaluationof the role of geese RIG-I in antiviral innate immunity.1. The sequence and analysis of goose RIG-I and MDA5gene.We first identified the RLRs in geese, and we found that geese have both RIG-I gene and MDA5gene. Then we cloned the full sequence of the two genes, and analyzed amino acid alignments of thetwo genes. The goose RIG-I (gRIG-I) exhibits93.8%amino identity with duck RIG-I (dRIG-I). Thegoose MDA5also shows87.2%amino identity with chicken MDA5. We speculate that gRIG-I mayhave a similar antiviral function with dRIG-I, and play an important role in innate immunity againstNDV, but the function of gMDA5is weak.2. The influence of NDV replication after transfect with exogenous gRIG-ITo determine whether gRIG-I recognizes NDV and induces an antiviral response, HEK293Tcells were transfected with gRIG-I full and gRIG-I CARD, then challenged with5’ppp RNA orinfected with NDV Herts/33, we found the hIFN-β were all enhanced. And mRNA levels of innateimmunity genes such as IFIT-1，IP-10，IRF3were all increased. To exclude the interference ofendogenous hRIG-I in HEK-293T, DF1cells which are free of RIG-I were transfected with gRIG-Ifull and gRIG-I CARD, and infected with NDV Herts/33, we found the IFN-β promoter activity weresignificantly increased. Our results show that exogenous gRIG-I functions against NDV infection.3. The function of endogenous gRIG-I against NDV infectionTo determine whether endogenous gRIG-I elicites innate immune response upon NDV infection,we infected GEF and geese with NDV and measure the levels of gRIG-I mRNA. The levels of gRIG-ImRNA were up-regulated in GEF. And levels of gRIG-I mRNA in lung and air sac were alsoincreased. The virus titers were all dropped. In this study, we confirmed the presence of goose RIG-I gene (gRIG-I) and investigated its rolein innate immunity against NDV infection.