The effect of neonatal pneumococcal pneumonia on vitamin A and its relationship with pulmonary immunity and airway responsiveness

TIAN Yonglu; TIAN Qingqing; CHEN Yunxiu; PENG Xin; ZHANG Qiyu; LI Yuanyuan; TIAN Xiaoyin; ZHANG Guangli; LUO Zhengxiu

doi:10.13431/j.cnki.immunol.j.20170177

Abstract：To investigate the effect of neonatal Streptococcus pneumoniae pneumonia (S.pp) on vitamin A status and its relationship with pulmonary immunity and airway responsiveness,neonatal (1-week-old) Balb/c mice were infected intranasally in conscious with 2 × 107 CFU of S.pneumoniae (D39) in 5 μl of PBS (S.pp group),while,mock-infected mice were intranasally with 5 μl of PBS (control group).Mice in S.pp+VA group were infected with S.pneumoniae and then administrated orally with a dose of 20 IU/g of VA for 4 consecutive days,while mice in control group was administrated the same dose of VA dissolved solute (rapeseed oil).To evaluate the effect of neonatal S.pp on vitamin A status in mice,we monitored vitamin A levels in lung,serum,and liver on 7,14,21,28 days post infection by HPLC;five weeks after infection,lung tissue slices were made and stained with HE to observe the lung pathology.Airway hyperresponsiveness (AHR) was measured in conscious and unrestrained mice by means of whole-body plethysmography.The levels of IL-4,IL-5,IL-13,IL-17A and IFN-γin BALF were examined by ELISA;and the levels of Th1,Th2 and Foxp3+Treg were determined by flow cytometry.Here we found that after neonatal S.pp,the VA status in lung decreased until the fourth week after infection,and the serum VA decreased until the 14th day after infection,while the VA level in the liver showed no significant difference.Data showed that the lung inflammatory cells infiltration in S.pp + VA group was alleviated,as compared with neonatal S.pp group;concentration of IFN-γin BALF of S.pp+VA group was significantly higher than that in the neonatal S.pp group (P＜0.01),while concentrations of IL-4,IL-5,IL-13 and IL-17A were significantly lower (P＜0 05).Th1 and Foxp3+ Treg cells were significant higher in S.pp+VA group as compared with the neonatal S.pp group (P＜0.01),while Th2 cells in S.pp+VA group were significantly lower than that in the neonatal S.pp group (P＜0.01).Furthermore,the ratio of Th1/Th2 was significantly increased in S.pp+VA group as compared with the neonatal S.pp group (P＜0.001).Besides,we found that airway hyperresponsiveness in S.pp + VA group was significantly lower than that in the neonatal S.pp group (P＜0.001).Taken together,neonatal S.pp can decrease lung VA significantly;supplementation of VA after neonatal S.pp can reduce lung inflammatory cells infiltration,improve the expression of Foxp3+Treg cells in lung,correct the imbalance of Th1/Th2 and inhibit the formation of airway hyperresponsiveness.