BackgroundEarly distinction between refractory M. pneumoniae pneumonia (RMPP) and non-RMPP (NRMPP) is still difficult. The community-acquired respiratory distress syndrome (CARDS) toxin can induce inflammatory and histopathological phenotypes associated with M. pneumoniae infection. This study aimed to investigate the clinical significance of CARDS toxin and pro-inflammatory cytokines in children with RMPP and to explore whether CARDS toxin can induce TNF-α expression.MethodsLevels of CARDS toxin and cytokines in BALF from control and children with MPP were determined by real-time PCR and ELISA, respectively. A receiver-operating characteristic (ROC) analysis was performed to assess the diagnostic values of CARDS toxin, TNF-α, and IL-6 in RMPP. The recombinant CARDS toxin was constructed and prepared at different concentrations for stimulation of RAW264.7 cells. After co-culture with CARDS toxin, cytokines were detected by ELISA and the mRNA levels were measured by real-time PCR. Effects of CARDS toxin and TNF-α on inflammatory cell infiltration and mucus secretion in mouse lungs were also evaluated.ResultsLevels of CARDS toxin, TNF-α and IL-6 in bronchoalveolar lavage fluid (BALF) were significantly higher in RMPP cases compared with NRMPP cases. Furthermore, TNF-α had better diagnostic ability for differentiation of RMPP with AUC of 0.824 and Youden index of 0.692 compared with CARDS toxin and IL-6. Moreover, CARDS toxin was positively correlated with TNF-α level in MPP cases. In vitro assay revealed that CARDS toxin induced RAW264.7 macrophages to secrete TNF-α. Further in vivo assay showed that TNF-α deletion partially abrogated the CARDS toxin-mediated induction of inflammatory cell infiltration and mucus secretion in mouse lungs.ConclusionsThe high co-expression of TNF-α and CARDS toxin in BALF is a good diagnostic biomarker for differentiating children with RMPP and NRMPP.

中文翻译：

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TNF-α和CARDS毒素的高共表达是难治性肺炎支原体肺炎的良好预测因子

背景早期区分难治性肺炎支原体肺炎（RMPP）和非肺炎支原体肺炎（NRMPP）仍然很困难。社区获得性呼吸窘迫综合征 (CARDS) 毒素可诱发与肺炎支原体感染相关的炎症和组织病理学表型。本研究旨在探讨CARDS毒素和促炎细胞因子在RMPP患儿中的临床意义，探讨CARDS毒素是否能诱导TNF-α的表达。分别为实时 PCR 和 ELISA。进行受试者操作特征 (ROC) 分析以评估 CARDS 毒素、TNF-α 和 IL-6 在 RMPP 中的诊断价值。构建并制备了不同浓度的重组卡毒素，用于刺激 RAW264.7 细胞。与CARDS毒素共培养后，通过ELISA检测细胞因子并通过实时PCR测量mRNA水平。还评估了卡毒素和 TNF-α 对小鼠肺部炎症细胞浸润和粘液分泌的影响。 结果 RMPP 病例支气管肺泡灌洗液 (BALF) 中卡毒素、TNF-α 和 IL-6 的水平显着高于 NRMPP案件。此外，与CARDS毒素和IL-6相比，TNF-α对RMPP的分化具有更好的诊断能力，AUC为0.824，Youden指数为0.692。此外，在 MPP 病例中，CARDS 毒素与 TNF-α 水平呈正相关。体外试验表明，CARDS 毒素诱导 RAW264.7 巨噬细胞分泌 TNF-α。