Influência da imunossupressão sobre a enterite experimental produzida por Giardia lamblia em modelo murino Meriones unguiculatus

Abstract

The giardiasis, cosmopolitan enteroparasitosis caused by the protozoan Giardia lamblia is among the most recurrent diarrheal diseases in developed countries and especially in developing countries, being responsible for poor digestion’s syndromes, physical and cognitive deficits in resident children. Among the groups of vulnerability in the management, include the main immunosuppressed, as a result of aggressive therapies used for the treatment of autoimmune diseases or organ transplants. In this population, giardiasis can result in chronicity and more severe infection. However, many immunodeficient individuals remain asymptomatic, although infected by the parasite for long periods. In view of this controversy, the aims of this study were to contribute to the elucidation of the subject through the evaluation of small intestinal permeability, histopathological and morphometric analysis in gerbils experimentally immunosuppressed and infected by G. lamblia. In this study were used 35 gerbils 4 to 6 weeks old distributed in 4 experimental groups: Control (CT) [n = 8], Control-infected by G. lamblia (CTIn) [n = 9], Immunosuppressed IM) [n = 9] and Immunosuppressed-infected by G. lamblia (IMIn) [n = 9]. The animals of the IM and IMIn groups received a treatment with Dexamethasone intramuscularly for 25 days for induction of immunosuppression. On the 11th experimental day, animals in the groups CTIn and IMIn were challenged with G. lamblia trophozoites remained infected for 14 days. On the 25th experimental day was administered on gerbils of all groups, a solution containing 99mTc-DTPA for evaluation of intestinal permeability. After this procedure, the euthanasia of the animals was produced, followed by collection and histopathological processing of the small intestine and spleen. The tissues were analyzed by histopathology, digital morphometry and immunohistochemistry for parasitism. Histopathological and morphometric analyzes revealed significant lesions in the duodenal mucosa of the CTIn group, with reduced villi size, hyperplastic crypts, moderate inflammatory infiltrate in the lamina propria and high rate of tissue epithelial renewal. On the other hand, in the IMIn group no inflammatory events were seen and villi were long, thin and intact. Goblet cells in the IMIn group were hyperplastic and culminated in increased production of intestinal mucus. Furthermore, in the IMI group, a significant increase in the number of G. lamblia trophozoites immunolabelled in the lumen of the animals was observed. No changes were observed in the intestinal permeability of the gerbils experienced. Thus, the reduction of intestinal damage in the intestinal mucosa of immunosuppressed animals, inferred an immune response of the host is one of the main responsible for the emergence of interactions during infection by G. lamblia in the experienced model. The protection of the intestinal gut in immunosuppressed animals, in particular, is an important action of the immune system, represented by mucus, which presents as an agent that makes it difficult for adhesion to the intestinal epithelium by G. lamblia trophozoites. The increase in the number of parasites in the gut of gerbils of the IMIn group confirms a chronicity observed in immunosuppressed men affected by giardiasis, such as gerbils as good models for the study of G. lamblia infections in immunosuppressed hosts.