Mary A. Franke

Effects of Cytokines and Fluconazole on the Activity of Human Monocytes against Candida albicans

ABSTRACT This study evaluates the effects of cytokines, used singly and in combination, on the microbicidal activity of human monocyte-derived macrophages (MDM) against intracellular Candida albicans in the presence and absence of fluconazole. In the absence of fluconazole, the addition of tumor necrosis factor alpha (TNF-α), interleukin-1β (IL-1β), gamma interferon (IFN-γ), or IL-4 had no effect on the growth of C. albicans. In contrast, the addition of granulocyte-macrophage colony-stimulating factor (GM-CSF) resulted in decreased growth (P < 0.05), while the addition of IL-10 resulted in increased growth (P < 0.01). In the presence of fluconazole, only the addition of IFN-γ resulted in an increase in the growth of C. albicans. In the presence or absence of fluconazole, all cytokine combinations except IFN-γ plus GM-CSF caused significant decreases in growth (P < 0.01). IL-10 and IL-4 did not influence the activity of TNF-α or IL-1β. In the absence or presence of C. albicans the addition of fluconazole, all of the cytokines studied, and combinations of fluconazole and selected cytokines caused increases in nitric oxide (NO) production (P < 0.01). Similar observations were made for superoxide (O2−) only in the presence of C. albicans. The greatest concentrations of NO and O2− were produced when C. albicansalone was present in the assays. Our results demonstrate that in the presence of low concentrations of fluconazole (0.1 times the MIC), selected cytokines and their combinations significantly increase the microbicidal activity of MDM against intracellular C. albicans.

Pseudomonas aeruginosa cytotoxin as a pathogenicity factor in a systemic infection of leukopenic mice

The effect of Pseudomonas aeruginosa cytotoxin was assessed in leukopenic outbred Swiss male mice (20 g) using a high cytotoxin-producing strain (PA158) and its cytotoxin-deficient isogenic mutant (PA114F5) generated by Tn7::Tn5 transposon mutagenesis of PA158. Leukopenia was induced by intraperitoneal (i.p.) administration of cyclophosphamide (150 micrograms/g). Anesthetized mice were infected via a 4 mm incision on the shaved back with 300 CFU/mouse (9 LD50; expected death rate 85%). Precleared mouse cytotoxin-specific heat inactivated rabbit polyclonal antibody (RPA) was administered i.p. (0.2 ml) 24 hr before challenge. Controls received i.p. normal rabbit serum, RPA, cyclophosphamide alone, or a sham procedure. Challenge with the high cytotoxin-producing strain PA158 caused earlier and a significantly greater mortality than that observed with a cytotoxin-deficient strain PA114F5 (P < 0.01). Cytotoxin-specific polyclonal antibody was protective. Pretreatment with antibody decreased the mortality rate following challenge with PA158 from 88.9% to 27.8% (P < 0.01). Pretreatment with antibody decreased the mortality rate following challenge with PA114F5 from 27.8% to 5.6% (P < 0.05). These results demonstrate that P. aeruginosa cytotoxin contributes to the pathogenicity of the organism and that cytotoxin antibody is protective in a systemic P. aeruginosa infection in leukopenic mice.