Adiaspore development and morphological characteristics in a mouse adiaspiromycosis model
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RESEARCH ARTICLE
Open Access
Adiaspore development and morphological characteristics in a mouse adiaspiromycosis model Asuka Takeshige1†, Mie Nakano1†, Daisuke Kondoh1†, Yuma Tanaka1, Akio Sekiya1, Takashi Yaguchi2, Hidefumi Furuoka1 and Takahito Toyotome1,2,3*
Abstract Lesions of adiaspiromycosis, a respiratory disease affecting wild animals, have been found mainly in dead mammals and free-living mammals captured for surveillance. No report has described an investigation of adiaspore formation progress in the lung. After establishing an experimental mouse model of intratracheal adiaspiromycosis infection with the causative agent Emmonsia crescens, we observed adiaspore development. The spores grew and reached a plateau of growth at 70 days post-infection. The median adiaspore diameter showed a plateau of around 40 μm. The characteristic three-layer cell-wall structure of adiaspores was observed in the lung at 70 days post-infection. We examined infection with a few spores, which revealed that adiaspores in the mouse lung progressed from intratracheal infection of at least 400 spores. Moreover, we developed adiaspores in vitro by culture in fetal bovine serum. Although most spores broke, some large spores were intact. They reached about 50 μm diameter. Thick cell walls and dense granules were found as common points between in vitro adiaspores and in vivo adiaspores. These models are expected to be useful for additional investigations of E. crescens adiaspores and adiaspiromycosis. Keywords: adiaspiromycosis, adiaspore, Emmonsia crescens Introduction Emmonsia crescens (Ajellomyces crescens), a dimorphic fungus found in soil worldwide [1], is known to be the causative agent of adiaspiromycosis, a pulmonary disease causing granulomatous lesions in humans [2] and animals, especially in small mammals [1–7] and rarely in large animals [8, 9]. Although the prevalence of adiaspiromycosis in animals remains unknown, Borman reported adiaspiromycosis in 28.7% of free-living wild mammals from the southwestern UK [10]. Reported human cases of adiaspiromycosis are few, with disease courses varying *Correspondence: [email protected] † Asuka Takeshige, Mie Nakano and Daisuke Kondoh contributed equally to this study 1 Department of Veterinary Medicine, Obihiro University of Agriculture and Veterinary Medicine, Inada‑cho, Obihiro, Hokkaido 080‑8555, Japan Full list of author information is available at the end of the article
from mild to fatal [2]. Studies have been done of wild animals captured with traps or found dead incidentally, then subsequently diagnosed as having adiaspiromycosis during necropsy. Because no report of the literature has described a study of the disease course from spore acquisition to mature adiaspore formation in the lung, related details have remained unknown. At around 25 °C, E. crescens grows as hyphae. However, the fungus forms adiaspores in mammalian hosts at around 37 °C [11]. A few infection models have been reported. An inhalation model has been used with rabbits [12] to analyze humoral immun
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