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Virulence of Sporothrix schenckii conidia and yeast cells, and their susceptibility to nitric oxide
Author(s) -
Fernandes K. S. S.,
Coelho A. L. J.,
Bezerra L. M. Lopes,
BarjaFidalgo C.
Publication year - 2000
Publication title -
immunology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.297
H-Index - 133
eISSN - 1365-2567
pISSN - 0019-2805
DOI - 10.1046/j.1365-2567.2000.00125.x
Subject(s) - sporothrix schenckii , microbiology and biotechnology , virulence , biology , yeast , nitric oxide , conidium , catalase , superoxide dismutase , sporotrichosis , biochemistry , oxidative stress , immunology , botany , gene , endocrinology
Summary The involvement of nitric oxide (NO) in macrophage (Mφ) fungicidal activity against Sporothrix schenckii , and the relationship between NO susceptibility and the differential virulence of conidia and yeast cells, were investigated. Confirming a previously reported correlation between the length of time in culture and virulence of S. schenckii , conidia isolated from 12‐day mycelial cultures ( Ss ‐12) were less virulent to mice than conidia from 7‐day cultures ( Ss ‐7) or yeast cells. Indicative of NO production, infected animals showed a significant increase in serum levels of nitrite that was lower in mice infected with Ss ‐12 than in mice infected with Ss ‐7 or yeast. Stimulation of murine Mφ with interferon‐γ (IFN‐γ) induced NO production and inhibition of fungal growth. The cytotoxic activity of Mφ against Ss ‐12 was significantly greater than against Ss ‐7 or yeast cells, the highly virulent fungal forms. The addition of NO synthase inhibitors abrogated Mφ cytotoxic activity against all fungal forms. The phagocytic activity of Mφ against Ss ‐7 was significantly lower than against Ss ‐12 or yeast cells. Although the ingestion of fungal cells triggered the oxidative burst in Mφ, the fungicidal activity was not altered in the presence of superoxide dismutase (SOD) and catalase. In addition, Ss ‐12 and yeast cells were more susceptible than Ss ‐7 to the direct fungicidal activity of the NO donors S ‐nitroso‐ N ‐acetyl‐ dl ‐penicillamine (SNAP), S‐nitrosoglutathione (GSNO) and 3‐morpholinosydnonimine (SIN‐1). The results of this study indicate that NO is a key cytotoxic mediator involved in the murine Mφ defence against S. schenckii , and that the virulence of Ss ‐7, Ss ‐12 and yeast cells may be related to a differential susceptibility to NO.