Susceptibility of Germfree Phagocyte Oxidase- and Nitric Oxide Synthase 2-Deficient Mice, Defective in the Production of Reactive Metabolites of Both Oxygen and Nitrogen, to Mucosal and Systemic Candidiasis of Endogenous Origin

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Abstract
Mice deficient for phagocyte oxidase (Phox) and nitric oxide synthase 2 (NOS2) (gp91phox−/−/NOS2−/−), defective in the production of both reactive oxygen intermediates (ROI) and reactive nitrogen intermediates (RNI), were used to investigate the role of phagocytic cells during mucosal and systemic candidiasis of endogenous origin. The alimentary tracts of germfree mice were colonized with Candida albicans wild type or each of two hyphal signaling-defective mutants (efg1/efg1 and efg1/efg1 cph1/cph1). All Candida-colonized gp91phox−/−/NOS2−/− mice were moribund within 12 to 15 days after oral inoculation. C. albicans wild-type and mutant strains colonized the alimentary tracts equally well and were able to translocate, most likely via Peyer's patches and mesenteric lymph nodes, to the internal organs and trigger the formation of abscesses; however, the wild-type and mutant strains did not survive in the abscessed murine tissues. Surprisingly, there was no significant difference in the ability of peritoneal exudate cells from gp91phox−/−/NOS2−/−, NOS2−/−, gp91phox−/−, or immunocompetent C57BL/6 mice to kill C. albicans in vitro. This suggests that anti-Candida factors other than ROI and RNI can control the growth of C. albicans and that gp91phox−/−/NOS2−/− mice die due to the inability of the host to control its inflammatory response to Candida. Correspondingly, reverse transcription-PCR analysis showed increased expression of the cytokines gamma interferon, tumor necrosis factor alpha, and the chemokines MIP-2 and KC at the site of infection, while interleukin-15 expression remained relatively unchanged between germfree and infected tissues. These studies indicate that defects in ROI and RNI enabled C. albicans to translocate and disseminate to the internal organs, resulting in an uncontrolled immune response, severe pathology, and death; however, ROI and RNI were not required for the killing of phagocytized C. albicans, indicating that other anti-Candida factors either compensate or are sufficient for the killing of phagocytized Candida.