Perfil transcricional e alterações histopatológicas na Leishmaniose visceral canina

Abstract

Background: Dog is the main domestic reservoir of Leishmania infantum in Brazil. Those animals present a wide spectrum of clinical manifestations, varying from weight loss, anemia to hepatosplenomegaly and skin lesions. The goal of this study was to evaluate the gene expression profile in the spleen and peripheral blood cells from naturally Leishmania-infected dogs and to study the histology of the spleen, liver, gut and skin, in order to determine possible molecular pathways and histopathological process underlying the mechanisms related to disease progression and resistance. Methodology: 21 dogs was studied and a sub group (n=8) was selected for transcriptomic studies. In addition, spleen, liver, gut and blood parasitism were estimated by qPCR and parasite was isolated from the spleen by culture. Total RNA was extracted and cDNA libraries were constructed and sequenced in an Illumina platform. The reads obtained were filtered and aligned against Canis familiaris genome using Bowtie. Differential gene expression was analyzed using the Cufflinks workflow, functional annotation and molecular features for each gene was obtained from Gene Ontology and KEGG database using STRINGdb. A fragment of liver, gut, skin and another spleen fragment were collected, processed and stained by HE and immunofluorescence for histopathological analysis. Results: Parasite load estimated in the spleen and liver were strongly associated, however no correlation was observed between them and circulating parasite estimation. Approximately, 756 genes were upregulated in the spleens of symptomatic dogs, as CTLA4, CCL2 and IL27, furthermore, about 1,190 genes were downregulated in the same group of animals, as BMP6, C1QB and C1QC. We found that NK cells activation, toll-like and NOD-like receptors pathways are highly expressed in the spleen of symptomatic dogs, while GPI-anchors synthesis and immunoproteasome activation related genes are downregulated in these animals. Additionally, we observed that in symptomatic animals, the cytoarchitecture of spleen is altered, with partial loss of the delimitation between white and red pulp. Furthermore, an intense inflammatory infiltrate in the liver, gut and skin of these animals. Confirming the RNA-Seq findings, we observed by immunofluorescence CTLA4, CCR7 and NLRP3 are overexpressed the spleen of symptomatic dogs. Conclusions: These findings suggest that misregulation of innate immunity is involved in CVL and an efficient antigen presentation maybe decisive for resistance to clinical signs development and tissue integrity during L. infantum infection in dogs.