Ozone exposure in the culture medium inhibits enterovirus 71 virus replication and modulates cytokine production in rhabdomyosarcoma cells

In the present study, the effects of ozone exposure on enterovirus 71 (EV71) replication and related cytokine production were investigated. Rhabdomyosarcoma cells (RD) were exposed to 0.5, 1, 1.5 and 2ppm ozone or filtered air under different exposure regimens before or after infection for 1 or 2 h. The results revealed that at a proper concentration of ozone, e.g., 1.5 or 2 ppm, ozone exposure restricted virus production, prolonged survival time of cells and modulated cytokine production related to EV71 infection. Upon exposure of non-infected cells to ozone at 1.5 or 2 ppm for 1 h, the production of IL-1 beta, IL-6 and TNF-alpha. was primed and boosted by the subsequent EV71 infection, generating an inhibitory effect on EV71 replication during the post-infection period of 48 h. While infected cells were exposed to ozone for 2 h at 1.5 or 2 ppm, ozone did not affect cytokine production by RD cells in response to EV71 infection. The data showed that ozone effect on induction of cytokine was only found in uninfected cells. The ozone-induced cytokines produced prior to the onset of EV71 infection generated antiviral effects, which proved beneficial in suppressing the subsequent EV71 infection. (C) 2007 Elsevier B.V. All rights reserved.