A Study On Specific CD4~+T Cellular Immune Characteristics And Pathogenesis Of Influenza Virus In Lung

BackgroundInfluenza caused by influenza virus can not only cause outbreaks,but also seasonal epidemics,which can often cause severe pneumonia and fatal acute lung injury,strong transmission,difficult to prevent,causing serious social panic and national economic losses.Most current influenza vaccine studies focus on surface proteins of influenza virus that induce neutralizing antibodies,but the limited duration of antibodies and the high mutation rate of surface proteins result in poor protection.Anti-influenza virus T cells mainly target conserved antigens with low internal mutation rate,and exist for a long time.Therefore,the specific cellular immune response has a more broad spectrum and lasting protective effect.Nowadays,international studies on influenza immunity focus more on CD8~+T cell immune response,and relatively few on CD4~+T cells(such as NP311 CD4~+T cell)that recognize conserved peptide segments of influenza virus.Hence,elucidating CD4~+T cell immune response is beneficial to strengthen the study of influenza pathogenic mechanisms and promote the development of novel vaccines.ObjectivesThe H1N1 infection model of influenza A virus was constructed to elucidate the epitope-specific CD4~+T cell immune response characteristics of influenza virus in different anatomical sites of lung,which are airway,between airway and parenchyma,parenchyma and vasculature,to analyze the phenotypic characteristics of NP311specific memory CD4~+T cells in different anatomical sites of the lung,and to elucidate the role of influenza virus NP311 epitope-specific CD4~+T cells in virus infection.MethodsConstruct influenza(A/WSN/33)C57BL/6 mouse infection model,record the weight change rate and survival rate of mice,as well as test the lung pathological injury and virus titer of mice.Virus specific T cellular immune response detection:in vivo antibody labeling method combined with flow cytometry,the NP311 specific CD4~+T cells of different anatomical parts of the lung were detected.the dynamic changes of immune response of cells at different times of natural infection and post-immuno-infection,,polypeptide affinity,multi-cytokine expression,and memory-specific cell phenotypes.The mice were treated with intranasal and intraperitoneal administration CD4~+depleting antibody GK1.5,monitored the body weight changes and survival of mice with or without VRP immunization after challenged with WSN.ResultsThe mouse model C57BL/6 WSN infection was successfully constructed,and it was found that there were four groups of NP311 specific CD4~+T cells in the respiratory tract:airway,middle state of airway and pulmonary parenchyma pulmonary parenchyma,and blood vessel.Among them,airway,and lung parenchyma and lung parenchyma NP311 CD4~+T cell response peak on the 10 days post infection.Moreover,NP311 CD4~+T cells in the airway have the strongest polypeptide affinity and multifactor expression ability.Memory NP311 CD4~+T cells in parenchyma has the CD4~+Trm phenotypes.VRP-EMC-N160-NP311 vaccine induces memory NP311CD4~+T cells in mice.Memory NP311 CD4~+cells promote NP366 CD8~+cell responses.The further use of GK1.5 depletion antibody,through different drug delivery methods to remove different parts of CD4~+T cells,proved that in WSN infection,the airway CD4~+T cells have pathogenic role.ConclusionsBy this study,four groups of NP311 CD4~+T cells with different anatomical sites in the respiratory tract of mice after influenza infection were elucidated,with their respective phenotypic characteristics and response abilities.To further clarify the pathogenic effect of NP311 CD4~+T cells in the airway,effectively fill the gap CD4~+T cell research in respiratory influenza virus infection,which is of great significance for the analysis of influenza virus pathogenic mechanism and the development of new influenza virus vaccines.