Respiratory burst by dengue-virus-induced cytotoxic factor

ABSTRACT

This study investigates the induction and release of the superoxide anion [O-2] and hydrogen peroxide [H2O2] by mouse spleen cells on stimulation with dengue type 2 virus [DV] and a DV-induced cytokine, the cytotoxic factor [mCF]. Normal mice or their spleen cell cultures were inoculated with DV or mCF. At different time periods, the spleen cell supernatants were assayed for the production of O-2 and H2O2. Inoculation of DV in spleen cell cultures resulted in peak production of O-2 and H2O2 at 48 and 72 h, respectively, while in DV-infected mouse spleen, the maximum production was on days 7 and 8, which correlated with the appearance of mCF in the milieu. Maximum O-2 and H2O2 production occurred at 45 min and 1 h after inoculation of 5 micro g of mCF. Pretreatment of mCF with anti-mCF-antiserum inhibited O-2 and H2O2 release indicating the specificity of the induction by mCF. The enriched subpopulations of macrophages and T cells produced O-2 and H2O2 and not B cells. Treatment of the cells with superoxide dismutase increased H2O2 release but inhibited O-2 release and the cytotoxicity in a dose-dependent manner. This showed that O-2 is responsible for the cytotoxic activity of mCF and not H2O2. In conjunction with our earlier findings that pretreatment with NG-monomethyl-L-arginine inhibited mCF-induced production of NO and the cytotoxicity, it is concluded that the presence of both O-2 and NO is required for the cytotoxic activity of mCF, thereby indicating a possible role of peroxynitrite