Innate Immune Response Mechanism Of Guinea Pigs Against Influenza A Virus Infection

Influenza A viruses (family Orthomyxoviridae) are enveloped negative-strand RNA viruses, causes the most prevalent infection of the respiratory tract in humans. In the past120years, there have been approximately5IV pandemics, all of those cause high morbidity and mortality in the world. In these years, researchers found that most influenza virus strains could induce animal models death and produce "Cytokine Strom", but the mechanism was not understand. In this study, we chose guinea pigs as mammalian model for research the innate immune response. Typically, guinea pigs do not show signs of disease and could clear the viruses upon infection with influenza. Choosing the guinea pigs as model, we can research the response characteristics of pattern recognition receptors, effectors molecular, cytokine and chemokine. It will provide reference to study the antivirus function of innate immunity.Firstly, in order to study the roles of IFN-β，IL-10, IL-18, IL-8, IP-10, TLR7, TLR8, RIG-1, MDA5, NLR, STAT1, MAVS, MX1, PKR, Caspase-1, TNF, IFN-y, IL-1β, CCL2, CCL5, TLR3, we have established a real-time PCR to detect mRNA expression by SYBR Green I. The results showed that the detection method was established successfully and verified.All the genes had similar amplification efficiency, so we could analysis dates by ΔΔCt methodsIn the study, we infected guinea pigs by four strains influenza A viruses (two strains of H1N1subtype and two strains of H5N1subtype) with different pathogenicity. Viral replication titer in lungs and nasal washes of guinea pigs upon infection H1-XD, H1-UI-182, H5-132, H5-LW type virus were assessed, the result showed in the nasal washes EID50was up to1045/ml,1052/ml,105.75/ml,101.98/ml. In the lungs EID50was up to105.5/ml,102.5/ml,105.25/ml,102.25/ml. Virus was not detected in the guinea pig infected virus for5days. The results showed that both H1N1and H5N1virus could replicate in lungs of guinea pigs and can be cleared in3to5days without clinic symptom upon infection.In order to elucidate the characteristics of innate immunity in guinea pigs upon infection with influenza, we analyze the mRNA expression levels in lungs by real-time PCR methods. The results showed upon infection with H1N virus which showed diversity in pathogenicity in mice, there were no obvious changes in the expression of pattern recognition receptors, effectors molecules, cytokines and chemokines. However, difference with H1N1virus, guinea pig infected with H5N1virus which showed diversity in pathogenicity in mice, the RIG-1and MDA5increased significantly in lungs, the effectors molecules Mxl and PKR were also increased. The results showed that guinea pig can activate innate immunity against influenza virus. Interestingly, the levels of cytokines and chemokines in guinea pig have no obvious changes. Especially, neither IL-1β,I1-8and TNF-a did increase significantly. It suggested guinea pigs distinguished from other mammals could escape from perpetuating inflammatory response. All the results in this study suggested we could clarify the role of innate immune response against influenza virus infection by further research to provide a new thought on the research of human highly pathogenic influenza viral pathogenesis.