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). Methods: 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. Results: 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 µ 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. Conclusion: 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 N^G-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.