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The hypothesis that Candida albicans isolate (CR1) from an HIV-infected individual induced apoptosis of macrophages was examined by optical microscopy, binding of annexin V-FITC and analyses of DNA degradation (TUNEL tests and agarose gel electrophoresis). Resident murine peritoneal macrophages co-incubated for 5–15 min with C. albicans CR1 bound annexin V, whereas macrophages incubated with either heat-inactivated strain CR1, C. albicans 577 (isolated from a patient with mucocutaneous candidiasis) or C. albicans FCF14 (a mutant that did not produce proteases and phospholipases) did not bind annexin for up to 2 h of observation. However, macrophages exposed to C. albicans CR1 did not present the pattern of DNA degradation typical of apoptosis. Macrophages became increasingly permeable to propidium iodide from 30 min to 2 h after their exposure to C. albicans CR1. Most of the phagocytosed C. albicans CR1 yeast cells switched to germ-tubes inside the macrophages after incubation for 1–2 h. These results show that macrophages exposed to C. albicans CR1 presented early signs of apoptosis but progressed to necrosis, and suggest that Candida strains that readily switch to germ-tubes inside those apoptotic cells might have a competitive advantage in vivo because released germ-tubes resist further attack by macrophages.
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