Objective: To investigate the cell types infected by severe acute respiratory syndrome-associated coronavirus (SARS-CoV) in lung tissues and explore the mechanism of lung injury in SARS.
Methods: In-situ hybridization(ISH) and immunohistochemistry(IHC) double staining was applied to study the lung tissues from 7 SARS cases of Beijing and one of Anhui province. According to SARS-CoV genome sequence, the cDNA probe was synthesized and labelled by digoxin. Immunohistochemically, antibodies of cytokeratin(CK), CD34, CD68, Vimentin and CD3 were applied to demonstrate bronchial epithelial cells, type II pneumocytes, endothelial cells, macrophages, fibroblasts and T cells respectively.
Results: The positive results of in-situ hybridization showed that the lung tissues of all cases expressed SARS-CoV RNA, and positive signals displayed in cytoplasms (purple-blue, NBP-BCIP. ISH-IHC double staining showed that positive signals of both ISH (purple-blue NBT-BCIP and IHC (red-brown, AEC expressed in the cytoplasms (purple and red). The positive results of double staining indicated that bronchial epithelial cells, type II pneumocytes, endothelial cells, macrophages, fibroblasts and T lymphocytes were diffusely infected by SARS-CoV.
Conclusion: This study of ISH-IHC double staining in lung tissues of SARS patients showed that bronchial epithelial cells, type II pneumocytes, endothelial cells, macrophages, T lymphocytes and fibroblasts were attacked diffusely in SARS lungs. Various types of cells damaged by SARS-CoV and inflammatory mediators released by those cells play an important role in the pathogenesis of lung injury in SARS.