Dissimilar peptidase production by avirulent and virulent promastigotes of Leishmania braziliensis: inference on the parasite proliferation and interaction with macrophages.

In the present paper, we have analysed the cellular and extracellular proteolytic activity profiles in 2 distinct Leishmania braziliensis strains: a recently isolated (virulent) and a laboratory-adapted (avirulent) strain. Quantitative and qualitative differences on the peptidase expression were observed in both strains. For instance, low-molecular mass acidic cysteine peptidase activities were detected exclusively in the virulent strain. Similarly, metallopeptidase activities were mainly produced by L. braziliensis virulent promastigotes. Interestingly, metallo- and cysteine peptidase activities were drastically reduced after several in vitro passages of the virulent strain. Western blotting, flow cytometry and fluorescence microscopy analyses were performed to detect homologous of the major leishmania metallopeptidase (gp63) and cysteine peptidase (cpb) in virulent and avirulent strains of L. braziliensis. Our results revealed that the virulent strain produced higher amounts of gp63 and cpb molecules, detected both in the surface and cytoplasm regions, than the avirulent counterpart. Metallo- (1,10-phenanthroline and EGTA) and cysteine peptidase (E-64) inhibitors arrested the growth of L. braziliensis virulent strain in a dose-dependent manner, as well as the association index with peritoneal murine macrophages. Conversely, these peptidase inhibitors did not affect either the proliferation or the cellular interaction of the avirulent strain. Corroborating these findings, the pre-treatment of the virulent strain with both anti-peptidase antibodies promoted a prominent reduction in the interaction with macrophages, while the association index of the avirulent strain to macrophage was only slightly diminished. Moreover, the spent culture medium from virulent strain significantly enhanced the association index between avirulent strain and macrophages, and this effect was reversed by 1,10-phenanthroline. Collectively, the results presented herein suggest that peptidases participate in several crucial processes of L. braziliensis.