Estudo comparativo de cepas de Leishmania infantum ? avalia??o da susceptibilidade a antimoniais e da express?o de microRNAS em macr?fagos J774.A1 e camundongos balb/c experimentalmente infectados.

Programa de P?s-Gradua??o em Ci?ncias Farmac?uticas. CIPHARMA, Escola de Farm?cia, Universidade Federal de Ouro Preto.A Leishmania infantum ? um protozo?rio agente etiol?gico da leishmaniose visceral, doen?a negligenciada e fatal na aus?ncia de tratamento. Este protozo?rio pode apresentar varia??es biol?gicas, podendo alterar a express?o de microRNAs em macr?fagos e em ?rg?os alvos da infec??o. Os microRNAs s?o mol?culas de RNA end?geno de cerca de 22 nucleot?deos, n?o codificadores de prote?nas, envolvidos numa s?rie de processos no organismo. Neste contexto, foi realizado um estudo comparativo utilizando duas cepas de L. infantum, a MHOM/BR/1972/BH46 e a MCAM/BR/2008/OP46, isoladas, respectivamente, de amostra humana e de c?o sintom?tico naturalmente infectado. As cepas foram avaliadas em macr?fagos J774.A1 e camundongos BALB/c. In vitro foram avaliadas a infectividade e a susceptibilidade a antimoniais. In vivo foi avaliada a carga parasit?ria no f?gado, ba?o e medula ?ssea pela t?cnica de dilui??o limitante. A express?o do miR-122 e do miR-155, microRNAs que foi determinada, respectivamente, no f?gado e no ba?o dos animais e a express?o do miR-155 foi tamb?m determinada nos macr?fagos. Os resultados deste trabalho demonstraram que a cepa OP46 foi menos suscept?vel aos antimoniais utilizados. Observou-se uma maior carga parasit?ria no ba?o e medula ?ssea dos animais infectados com a cepa OP46 quando comparado com os animais infectados com a cepa BH46. Al?m disso, ocorreu um aumento na massa do ba?o dos animais infectados com a cepa OP46 quando este grupo foi comparado ao grupo de animais n?o infectados. Em rela??o ? express?o dos microRNAs, observou-se diferen?a significativa na express?o do miR-155 em macr?fagos infectados com as duas cepas em compara??o com c?lulas n?o infectadas, sendo que os macr?fagos infectados com a cepa OP46 mostraram uma maior express?o deste microRNA. No entanto, n?o houve diferen?a ao se analisar a express?o do miR-155 e do miR-122 in vivo. Assim, neste estudo foi observado que a cepa OP46 foi mais infectante para camundongos BALB/c, menos suscept?vel a antimoniais al?m de provocar um aumento na express?o de miR-155 em macr?fagos infectados.Leishmania infantum is a protozoan responsible for causing visceral leishmaniasis (VL). This neglected disease is severe and fatal if untreated. Different L.infantum strains may have different behavior ?in vitro? and ?in vivo?. These strains can also induce a change in the expression of microRNAs in infected macrophages in vitro and in target organs of the infection. MicroRNAs are small endogenous molecules of about 22 nucleotides, non-coding RNAs that are involved in a number of processes in the body, including in the immune system response. In this respect, the infectivity in two L. infantum strains, MHOM/BR/1972/BH46, isolated from a human case and, MCAM/BR/2008/OP46, isolated from a symptomatic infected dog was characterized using J774 macrophages and BALB/c mice. Thus, in this work, In vitro tests were performed to evaluate the infectivity and susceptibility of the two strains to antimonials. The parasite burden was assessed in liver, spleen and bone marrow using the serial limiting dilution technique. In addition, miR-122 was evaluated on liver fragments from infected animals and miR-155 was evaluated on infected J774 macrophages and spleen fragments from infected animals to relate their expression to the infection.Our results showed that the OP46 strain was less susceptible to the antimonials used. A higher parasite burden was observed in the spleen and bone marrow in the animals infected with L. infantum OP46 strain compared to BH46 strain. Furthermore, an increase in spleen weight was observed in the animals infected with OP46 strain compared to non-infected control group. In relation to the expression of the microRNAs, a significant difference in the expression level of miR155 was observed in J774 macrophages infected with both L. infantum strains compared to uninfected cells, with a higher level of expression in cells infected with OP46. However, no difference in the expression level of miRNAs, miR-122 and miR-155 was observed respectively in liver and the spleen and from infected animals. Thus, in this study it was observed that the OP 46 strain was more infective for BALB/c mice, less susceptible to antimonials, besides causing an increase in miR-155 expression in infected macrophages