Influence of IL-22 cytokine on Mycobacterium leprae multiplication: baciloscopic and histopathologic analysis in IL-22 knockout mice

Abstract

Leprosy is a chronic infectious disease caused by Mycobacterium leprae. Currently, according to the World Health Organization, more than 200,000 new leprosy cases are registered annually, mainly in countries in development located in Africa, Asia, and South America, with shows an important public health problem. This disease affects mainly the skin, peripheral nervous system, and based on clinical and histopathological characteristics, it can be classified in two polar forms (tuberculoid and lepromatous), beyond borderline forms and leprosy reactions. In this context, the immunologic response has a fundamental role in the determination of disease pathogeneses, once it is observed influence of Th1 and Th2 subpopulation in leprosy immunopathogenesis, highlights Th1 patterns in tuberculoid polo and Th2 in lepromatous polo. However, recent studies have reported the involvement of other T cells subpopulations (such as regulatory T cells and Th17) on leprosy pathogenesis, and that preliminary results were obtained in our laboratory (JP FAPESP project 2009/06122-5) have corroborated with these results. Additionally, results of this project demonstrated a significant increase in the IL-22 cytokine expression in skin lesions of patients with leprosy when compared to control (health skin), suggesting the involvement of other subpopulations in the immunoregulation of diseases, such as Th22 and Th17, that characteristically produce IL-22. Thus, due to the importance of the role of IL-22 recently reported in several diseases such as rheumatoid arthritis, Crohn's disease, and dermatological disorders such as psoriasis and allergic dermatitis, and based on the preliminary results previously mentioned, this project aims to assess the influence of IL-22 cytokine in experimental leprosy (according to Shepard's technique), specifically in response to M. leprae inoculation assessed by bacillary multiplication, as well as by histopathological characteristics of sites of bacillary multiplication (footpad), by comparative analysis of wild-type mice (C57BL/6) and IL-22 knockout. (AU)