Proteomic characteristics of bronchoalveolar lavage fluid in critical COVID-19 patients.

Zeng, Hao-Long; Di, Chen; Yan, Jingjun; Yang, Qing; Han, Qiang-Qiang; Li, Shu-Sheng; Cheng, Liming

Up to 10-20% of patients with Coronavirus Disease 2019 (COVID-19) develop a severe pulmonary disease due to immune dysfunction and cytokine dysregulation. However, the extracellular proteomic characteristics in respiratory tract of these critical COVID-19 still remains to be investigated. In the present study, we performed a quantitative proteomic analysis of the bronchoalveolar lavage fluid (BALF) from patients with critical COVID-19 and from non-COVID-19 controls. Our study identified 358 differentially expressed BALF proteins (p < 0.05), among which 41 were significantly changed after using the Benjamini-Hochberg correction (q < 0.05). The up-regulated signaling was found to be mainly involved in inflammatory signaling and response to oxidative stress. A series of increased extracellular factors including Tenascin-C (TNC), Mucin-1 (KL-6 or MUC1), Lipocalin-2 (LCN2), periostin (POSTN), Chitinase 3-like 1 (CHI3L1 or YKL40), S100A12, as well as the antigens including lymphocyte antigen 6D /E48 antigen (LY6D), CD9 antigen, CD177 antigen, prostate stem cell antigen (PSCA) were identified. Among which, the pro-inflammatory factor TNC and KL-6, that were further validated in serum of another thirty-nine COVID-19 patients and healthy controls, showing high potentials of being biomarkers or therapeutic candidates for COVID-19. This BALF proteome associated with COVID-19 would also be a valuable resource for researches on anti-inflammatory medication and understanding the molecular mechanisms of host response.