Novel Mouse Models of Fungal Asthma

Abstract

Alternaria alternata is a ubiquitous fungus and a major allergen associated with the development of asthma. Inhalation of intact spores is the primary cause of human exposure to fungal allergen. However, allergen-rich cultured fungal filtrates are oftentimes used in the current models of fungal sensitization that do not fully reflect real-life exposures. Thus, establishing novel spore exposure models is imperative. In this study, we established novel fungal exposure models of both adult and neonate to live spores. We examined pathophysiological changes in the spore models as compared to the non-exposure controls and also to the conventional filtrate models. While both Alternaria filtrate- and spore-exposed adult BALB/c mice developed elevated airway hyperresponsiveness (AHR), filtrates induced a greater IgE mediated response and higher broncholavage eosinophils than spores. In contrast, the mice exposed to Alternaria spores had higher numbers of neutrophils. Both exposures induced comparable levels of lung tissue inflammation and mucous cell metaplasia (MCM). In the neonatal model, exposure to Alternaria spores resulted in a significant increase of AHR in both adult and neonatal mice. Increased levels of IgE in both neonatal and adult mice exposed to spores was associated with increased eosinophilia in the treatment groups. Adult demonstrated increased numbers of lymphocytes that was paralleled by increased IgG1 production. Both adults and neonates demonstrated similarly increased eosinophilia, IgE, tissue inflammation and MCM.

Keywords: AHR; Alternaria; asthma; fungus; lung; pathophysiology.

Figure 1

Alternaria-induced AHR. Mice were exposed to Alternaria filtrates, spores, or HBSS controls. Peak resistance after methacholine challenge was presented as Mean ± SEM, n = 8/group. *P < 0.05.

Figure 2

BAL cell counts and serology in the filtrate or spore model. Data represents mean ± SEM, n = 8-10/group. *P < 0.05. (A–D) Differential cell counts. Different cell types in BAL samples were counted from these mice and presented as the total cell number. (E, F) Serological testing for total serum IgE and IgG1. (G, H) BAL IL-13 and IL-17 in the mice treated with spores. (I, J) BAL IL-13 and IL-17 in the mice treated with filtrates.

Figure 3

Histological analyses of the filtrate or spore model. *p < 0.05, n = 8. (A) H&E scores. (B) Example H&E images. (C) PAS scores. (D) Example PAS images.

Figure 4

Alternaria spore-induced AHR in adults or neonates. Adult mice or neonates were exposed to spores or HBSS controls. Peak resistance after methacholine challenge was presented as Mean ± SEM, n = 8/group. *P < 0.05.

Figure 5

BAL cell counts and serology in adults or neonates. Data represents mean ± SEM, n = 8-10/group. *P < 0.05. (A–D) Differential cell counts. Different cell types in BAL samples were counted from these mice and presented as the total cells. (E, F) Serological testing for total serum IgE and IgG1.

Figure 6

Histology analyses of adults and neonates. *p < 0.05, n = 8. (A) H&E scores. (B) Example H&E images. (C) PAS scores. (D) Example PAS images.