Leishmania ssp. are protozoan parasites transmitted to vertebrates by the bite of female phlebotomine insects. They have two main forms in their life cycle: promastigotes and amastigotes. The amastigotes live preferably in macrophages, "professional phagocytes" capable of destroying pathogens. They are able to circumvent the microbicidal activity of macrophages, survive and multiply inside them. This ability is due to several molecules produced by the parasite, called virulence factors, which help their internalization and proliferation inside the macrophage. The protein LaLRR17 of L. (L) amazonensis contains in its central region six leucine-rich repeats (LRRs). The LRR motifs of various organisms are usually involved in protein-protein interactions. LaLRR17 is expressed in promastigotes and amastigotes, and was detected in the cytoplasm of the infected macrophage. Parasites overexpressing this protein showed increased infectivity in vitro. It is therefore plausible to assume that LaLRR17 participates in interactions with macrophage molecules, and that these interactions may modulate the response of the host cell. However, we do not know which molecules from the macrophage interact with LaLRR17. Phage display is a technique based on protein expression in synthetic phage capsids that has been used for various purposes including the identification of protein ligands. The application of Phage Display over the recombinant LaLRR17 may identify ligands of this protein in the macrophage and explain its contribution to the virulence of the parasite. Furthermore, analysis of the location and effects of the protein during infection of macrophages will give more information about the role of LaLRR17 in the interaction between Leishmania and its host cell.
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