The effects of rIL-17A intranasal inoculation against Streptococcus pneumoniae infection in murine models

Objective To evaluate the effects of intranasal administration of recombinant interleukin-17A(rIL-17A) on the expressions of β-Defensin-2(Defb2) and macrophage inflammatory protein(MIP) in pneumococcal pneumonia murine models.Methods Twenty-four BALB/c mice were divided randomly into normal control,pneumococcal pneumonia,and rIL-17A intervention groups ( n =8 ).Before intranasal (i.n) infection with Streptococcus pneumoniae,the mouse was treated with PBS or rIL-17Ai.n respectively.The mRNA levels of Defb2,MIP-1α and MIP-2β expression in lung tissue were detected by real-time quantity PCR.The numbers of bacteria and leukocytes in bronchoalveolar lavage fluid (BALF) were counted as well.And the concentrations of MIP-1α,MIP-2β,IFN-γ and IL-4 in BALF and in supematants of spleen cells and mediastinal lymph node cells were assayed by ELISA.Changes in lung tissue histopathology were observed with HE staining through light microscope.Results Neutrophil and macrophage numbers are higher in BALF of rIL-17A group,while the numbers of bacteria were lower,when compared with those in pneumonia group( P＜0.01 ).The expression of Defb2 and MIP-1α mRNA were up-regulated in lung after rIL17A treatment(P＜0.01 ).When compared with rIL-17A non-treated mice,rIL-17A treated mice secretedhigher levels of MIP-1α in lymph node cell culture supernatants( P＜0.01 ),higher levels of MIP-2β were observed in spleen cell and lymph node cell culture supernatants( P＜0.01 ),higher levels of IFN-T were detected in BALF( P ＜ 0.01 ) and culture supernatants of spleen cell ( P ＜ 0.01 ) and lymph node cell ( P ＜0.05),and higher levels of IL-4 were detected in BALF and spleen cell culture supernatant(P＜0.01 ).Comparative analysis have not detect a significant irflammatory cell increases in rIL-17A treated mice lung tissue; however the histopathological lesions were decreased.Conclusion Intranasal inoculation of rIL-17A can promote pulmonary neutrophil and macrophage recruitment and bacterium clearance,Intranasal inoculation of riL-17enhances the host defense against Streptococcus pneumoniae infection partly through increasing the expression levels of defensins,MIP,IFN-T and IL-4 etc. Key words: Streptococcus pneumoniae; Interleukin-17A; Macrophage inflammatory protein; Chemotactic factor