Molecular study of relationship between Leishmania (Leishmania) infantum and its hosts mediated by extracellular vesicles and micro-RNAs

Abstract

Leishmaniases compose a zoonosis group caused by Leishmania genus. They affect skin, mucous, membranes and/or viscera of man, domestic and wild animals. They constitute a serious public health problem worldwide, with approximately 350-million individuals worldwide exposed to the disease. In relation to visceral leishmaniasis (VL), infected individuals have long febrile periods, weight loss, anemia and changes in internal organs such as spleen and liver, which can lead to progressive weakness and evolution to death. Despite Brazilian Control Programs, infection areas are expanding in Brazil. Domestic dogs are the largest reservoirs of VL and are of great epidemiological importance. Consequently, the high prevalence of canine visceral leishmaniasis (CVL) is associated with human cases. Since the introduction of LVC in São Paulo State, more than 175 municipalities have had LV. These data are sufficient for the development of new strategies for control, diagnosis, treatment and information for populations at risk. Recent studies demonstrate the importance of extracellular vesicles (EVs) produced by eukaryotic cells, mainly in cellular communication. EVs are found in biological fluids and are involved in carrying molecules such as micro-RNAs (miRNAs), proteins, lipids, DNA, among others. They perform specialized functions and play a key role in intercellular signaling, waste management, and immune response, among other functions. However, the importance of EVs in the mechanism of Leishmania (Leishmania) infantum infection, which causes VL, is still unclear. The aim of the present proposal is to investigate the participation of extracellular vesicles and miRNAs in the modulation of humoral and cellular immune responses in infected hosts by L. (L.) infantum. Dogs were chosen for this study, due to the epidemiological importance of this host in VL. EVs will be purified from L. (L.) infantum promastigotes maintained in axenic cultures and, subsequently, characterized by nanoparticle tracking analysis and electron microscopy (transmission and scanning). Next, interactions of EVs released by L. (L.) infantum with THP-1 phagocytic cells and with murine splenocytes will be investigated. In equality, the capacity of stimulated cells and RNA molecules extracted from dogs with CVL to produce anti and pro-inflammatory cytokines will be evaluated. In addition, the ability of these EVs to stimulate the immune response of dogs with LVC will also be investigated by immunological assays. The second part of the project will be dedicated to evaluate in sera of dogs with LVC whether miRNA species may be involved in the infection. The estimated results will be important to understand the pathogen/host relationship and to evaluate the role of EVs in LVC evolution. (AU)