Research Paper Murine model of invasive pulmonary Aspergillosis: Follow-up of tissue injury, fungal burden and mortality with distinct elastase production strains R.L.H. Silva a, *, E. Rosa-Milani b , M.O. Brunaldi a , C.M.L. Maffei b a Department of Pathology and Legal Medicine, Ribeira˜o Preto Medical School, University of Sa˜o Paulo, Avenida Bandeirantes, 3900 Ribeira˜o Preto, 14049-900 Sa˜o Paulo, Brazil b Department of Cellular and Molecular Biology and Pathogenic Bioagents, Ribeira˜o Preto Medical School, University of Sa˜o Paulo, Avenida Bandeirantes, 3900 Ribeira ˜o Preto, 14049-900 Sa ˜o Paulo Brazil 1. Introduction Individuals with neutropenia and taking high doses of corticosteroids, immunosuppressors or chemotherapeutics have an elevated risk of developing opportunistic mycosis [1,2]. Envi- ronmental microorganisms such as Aspergillus fumigatus are constantly inhaled and may cause invasive pulmonary Aspergillo- sis (IPA) in these patients. In this way, the tissue injuries are induced by the interaction between the host’s defense and the pathogen virulence [3]. The inhaled spores adhere to the mucus produced by epithelial cells, facilitating their removal. These physical barriers, which are assisted by mechanical defenses such as sneezing and coughing, contribute for the clearance of spores [4]. Phagocytes from the innate immune system essentially mediate the pulmonary defense against A. fumigatus. The alveolar macrophages eliminate conidia, phagocyting them, whereas neutrophils destroy the germinative forms (hyphae) through the production and release of free oxygen radicals [5,6]. If the immune system is not competent, the conidia germinate, generating hyphae that invade the tissue and lead to the development of IPA. In addition to its ability to grow at several temperatures (thermotolerance) and its production of small conidia (2–3 mm), A. fumigatus has several virulence factors. These factors are essential for the establishment and maintenance of IPA. They include:  gliotoxin [7,8], which is a potent inhibitor of the mucociliary system that compromises the expulsion of inhaled conidia and also inhibits the action of phagocytic cells and T lymphocytes;  catalases [9,10], which are compounds that participate in the ablation of substances derived from the oxygen produced by macrophages and polymorphonuclear cells;  proteases such as elastases [11–13], which are involved in the invasion of pulmonary tissue, rich in elastin, and other virulence factors. In order to contribute to the study of the pathophysiological mechanisms of IPA, we established a model of neutrophil depletion in mice treated with the monoclonal antibody Gr-1/Ly-6G. Then, we evaluated the follow-up of the pulmonary tissue response in these animals and in immunocompetent mice infected with two strains of A. fumigatus presenting different elastase production patterns. Journal de Mycologie Me ´ dicale xxx (2018) xxx–xxx A R T I C L E I N F O Article history: Received 7 July 2018 Received in revised form 15 October 2018 Accepted 16 October 2018 Available online xxx Keywords: Experimental IPA Aspergillus fumigatus Gr-1/Ly-6G monoclonal antibodies Elastase Fungal burden Histopathological studies A B S T R A C T To study invasive pulmonary Aspergillosis (IPA), we depleted neutrophils in mice using the monoclonal antibody anti-Gr-1/Ly-6G. Immunocompetent and neutropenic mice were infected via intratracheal with conidia of Aspergillus fumigatus clinical isolates, characterized as either higher or lower elastase producers. Neutropenic animals exhibited 100% mortality in 5 days, for both strains, and were observed survival curves overlapped, lungs with angioinvasion, rupture of bronchial and vascular walls, associated with exuberance of conidia filamentation. The immunocompetent animals infected with the lower elastase producer strain presented with upregulated inflammatory processes, and a lack of conidia filamentation in the tissue. The fungal burden in the lungs was not different in the immunocompetent and neutropenic groups. These findings confirm the protective role of neutrophils against A. fumigatus and suggest that the fungal elastinolytic activity is not a critical virulence factor but may be involved in tissue injury.  C 2018 Elsevier Masson SAS. All rights reserved. * Corresponding author. Rua Dona Maria Janasi Biagioni, 463, Apartamento 66, 14801-309 Araraquara, Sa ˜o Paulo, Brazil. E-mail addresses: raphaelholanda1983@gmail.com (R.L.H. Silva), beterosa@fmrp.usp.br (E. Rosa-Milani), brunaldifam@uol.com.br (M.O. Brunaldi), cmlmaffe@fmrp.usp.br (C.M.L. Maffei). G Model MYCMED-842; No. of Pages 8 Please cite this article in press as: Silva RLH, et al. Murine model of invasive pulmonary Aspergillosis: Follow-up of tissue injury, fungal burden and mortality with distinct elastase production strains. Journal De Mycologie Me ´ dicale (2018), doi:10.1016/ j.mycmed.2018.10.003 10.1016/j.mycmed.2018.10.003 1156-5233/$ – see front matter  C 2018 Elsevier Masson SAS. All rights reserved.