A novel subset of putative stem/progenitor CD34⁺Oct-4⁺ cells is the major target for SARS coronavirus in human lung

Identification of the nature of severe acute respiratory syndrome (SARS)-infected cells is crucial toward understanding the pathogenesis. Using multicolor colocalization techniques, we previously reported that SARS⁺ cells in the lung of fatally infected patients expressed the only known functional receptor, angiotensin-converting enzyme 2, and also a binding receptor, liver/lymph node–specific ICAM-3–grabbing non-integrin (CD209L). In this study, we show that SARS-infected cells also express the stem/progenitor cell markers CD34 and Oct-4, and do not express cytokeratin or surfactant. These putative lung stem/progenitor cells can also be identified in some non-SARS individuals and can be infected by SARS-coronavirus ex vivo. Infection of these cells may contribute to the loss of lung repair capacity that leads to respiratory failure as clinically observed.