Virulence comparisons of Aspergillus nidulans mutants are confounded by the inflammatory response of p47phox-/- mice

Abstract

While investigating the requirement for phagosomal alkalinization in the host defense against pulmonary aspergillosis, we observed high morbidity of p47(phox)(-/-) mice infected with pH-insensitive Aspergillus nidulans mutants despite a paucity of fungal growth. Fatal infection also resulted from a normally avirulent p-aminobenzoate auxotroph. This demonstrates that p47(phox)(-/-) murine immunity contributes significantly to A. nidulans lethality. These data have wider implications for microbial virulence studies with p47(phox)(-/-) mice.

FIG. 1.

A. nidulans pH mutants cause disease similar to that caused by the wild type in p47^phox−/− mice. Wild-type, alkaline-nonresponsive, and alkaline-adapted A. nidulans strains show similar histopathological features of disease progression in p47^phox−/− mice. Lungs were removed 48 h after infection with 10⁶ A. nidulans conidiospores of the wild-type, alkaline-nonresponsive (C209), and alkaline-adapted (C14) strains. GMS-stained sections reveal equivalent fungal burdens, while hematoxylin-and-eosin (HE) staining shows a massive influx of PMNs.

FIG. 2.

Characterization of pulmonary aspergillosis in p47^phox−/− mice. (A) Time to 20% weight loss of p47^phox−/− mice following intranasal infection with 10⁵, 10⁴, or 10³ A. nidulans wild-type conidiospores. (B) Mean body temperature (°C) of p47^phox−/− mice following A. nidulans wild-type infection with 10⁵, 10⁴ (fatal infection and nonfatal infection), and 10³ conidiospores. 129sv parental wild-type mice infected with 10⁵ A. nidulans wild-type conidiospores and saline-inoculated p47^phox−/− mice served as controls. (C) Histopathological analysis of pulmonary aspergillosis in p47^phox−/− mice receiving 10⁵ or 10⁴ A. nidulans wild-type conidiospores at day 4 postinfection, 10³ A. nidulans wild-type conidiospores at day 21 postinfection, or 10⁶ A. nidulans p-aminobenzoate auxotroph 302 (pabaA1) conidiospores at day 4 postinfection. Arrows indicate positioning of ungerminated conidiospores.