Research Description:

Antigen Sequestration and Pathogenesis in Leishmania-Infected Cell

Leishmaniasis is a chronic disease that can manifest itself as visceral, cutaneous, or mucocutaneous lesions depending on the species of Leishmania. Leishmania parasites exist in two morphological forms during their life cycle: the motile, flagellated promastigote found in the insect vector, and the amotile amastigote that resides primarily within macrophages in the mammalian host. There is evidence that suggests that parasite persistence in the infected host might occur because T cells are minimally able to recognize infected cells. The mechanism that underlies this defect in antigen presentation is not known.

In order to better understand how Leishmania parasites are able to inhibit presentation of their antigens, we have elected to study trafficking of host cell molecules that play critical roles in antigen presentation. Our primary focus will be on the class II major histocompatibility complex (MHC-II). We plan to study its recruitment to the parasitophorous vacuole, the compartment in which the parasite occupies while inside the macrophage over a 48-hour infection course. The experimental approach will be to perform immunofloresence assays on infected cells, which will allow MHC-II localization to be visualized by microscopy. In addition, isolated vacuoles will be subjected to western blot analysis for more sensitive analyses of the protein content of parasitophorous vacuoles. By analyzing the distribution of MHC-II in the infected macrophage at different time points, we will achieve a better understanding of when MHC-II is recruited to the parasitophorous vacuole and which cellular events accompany this process. We also plan to assess how the pathway of parasite entry affects MHC II trafficking into the parasitophorous vacuole. It is known that parasites can be internalized through several phagocytic receptors on the macrophage surface and that differential engagement of these receptors can affect Leishmania pathogenesis.