Avaliação da reação inflamatória induzida por Leishmania braziliensis resistente ou susceptível ao antimônio no modelo da bolsa de ar subcutânea

Abstract

Tegumentar leishmaniasis is one of the most important neglected infectious parasitic diseases. It is caused by parasites belonging to the genus Leishmania, transmited by sandflies form genus Lutzomyia, and has L. (Viannia) braziliensis as the most relevant etiologic agent in Brazil. This disease shows a broad spectrum of clinical manifestations, which depend on both hot’s immune response and species and strain of Leishmania that is infecting it. The knowledge of the onset of the immune response during the first hours after L. (V.) braziliensis infection is essential for the understanding of the disease, hence its importance in infection control or establishment. Glucantime is the first choice medicine for treating leishmaniasis in Brazil, but the uprise of resistant strains is one of its main problems. In the present work the air pouch model was performed using BALB/c mice to assess the initial inflammatory response caused by two strains of L. (V.) braziliensis, one of which is susceptible to treatment by antimony, while the other resists it. In order to address it, BALB/c mice had air pouches made on their backs, using antimony resistant ou susceptible L. braziliensis inocula, or saline (negative control). 12 h after stimulation, the air pouch exudate was collected to assess cell recruitment and phenotype. The resistant strain showed an inferior leukocyte recruitment (246.7 ± 27.88 x 104 cells/ml) when compared to the susceptible strain (525 ± 77.76 x 104 cells/ml), along with dicreased recruitment of macrophages (15.05 ± 2.468 x 104 cells/ml) and lymphocytes (5.061 ± 0.8926 x 104 cells/ml) in the differential counting, again compared to the susceptible strain (macrophages: 41.09 ± 10.97 x 104 cells/ml; lymphocytes: 12.22 ± 3.654 x 104 cells/ml), suggesting that the resistant strain has the ability to be less noticed by the host’s immune system. Other than that a higher number of neutrophils was detected in the exudates of both strains, which may serve as transient hosts for promastigotes. It is likely that the macrophages collected are not be in a pro-inflammatory state, therefore contributing to the low lymphocyte recruitment. In short those mechanisms may provide the resistant parasite a safe place to be in and a silent way of entering its host cell, enhancing its survivability.