[The possible mechanism of lung injury induced by severe acute respiratory syndrome coronavirus spike glycoprotein].

OBJECTIVE: To investigate the role of severe acute respiratory syndrome coronavirus (SARS-CoV) in the induction of acute lung injury by promoting the synthesis of chemokine/cytokines in human endothelial cells.

METHODS: Twenty-three SARS patients were enrolled in this study, comprising 15 male and 8 female, aged 27 - 55 years, mean (36 +/- 6) years. They were treated at Guangzhou Institute of Respiratory Disease from February to May in 2003. Chemokines/cytokines in the blood of patients with SARS were dynamically screened by liquid chip system. The lung was studied histopathologically using immunohistochemical technique. Spike glycoprotein of SARS-CoV was recombined by using insect-baculovirus expression system and Nickel affinity Magnet Beads, and then used to stimulate cultured human umbilical vein endothelial cells (HUVEC). Morphological changes of HUVEC were observed by microscope. Levels of chemokines/cytokines involved in immunoreaction in response to virus infection were detected in the supernatants of those cells cultured with the Spike glycoprotein by liquid chip system.

RESULTS: Interferon-gamma inducible protein 10 (IP-10) was markedly elevated in the blood during the early stage of SARS [(7,600 +/- 2,400) ng/L, P < 0.01], and remained at a high level in the progressive stage [(8,100 +/- 2,300) ng/L, P < 0.01] and the end stage [(8,000 +/- 2,800) ng/L, P < 0.01] until convalescence [(1,250 +/- 450) ng/L, P > 0.05]. Moreover, IP-10 was highly expressed in the lung. Vacuoles appeared in part of HUVEC after Spike glycoprotein stimulation. As time going on, the HUVEC turned to be round in shape and even disrupted. Under normal condition, no detectable IP-10 was found in HUVEC. A high level of IP-10 [(179 +/- 34), (889 +/- 212), (1,676 +/- 199) ng/L, all P < 0.05] was detected in the HUVEC 12 h after Spike glycoprotein (5, 20, 40 mg/L) stimulation respectively, and presented with a significant dose-dependent response.

CONCLUSIONS: (1) A significant increase of IP-10 activity in the blood was found in patients with SARS-CoV infection, and remained at a high level until the stage of convalescence. A strong IP-10 protein expression was also found in SARS-CoV infected lung in autopsy. (2) The Spike glycoprotein of SARS-CoV induced a high level of IP-10 in endothelial cells, which in turn damaged endothelial cells. (3) The Spike glycoprotein of SARS-CoV induced IP-10 production by a way independent of IFN-gamma.