Role of cell surface mannose residues in host cell invasion by Trypanosoma cruzi.

The role of mannose residues on the membranes of Trypanosoma cruzi and its host cells in their association (surface binding plus internalization of the parasite) leading to infection was studied. Used in this work were the bloodstream (trypomastigote), intracellular (amastigote) and insect-transmissible (metacyclic trypomastigote) forms of the parasite; mouse macrophages and rat heart myoblasts were used as the host cells. Removal of mannose residues from the surface of all forms of the parasite by treatment with alpha-mannosidase produced a marked increase in their respective abilities to associate with either host cell. The increase was more pronounced with the bloodstream and insect-derived trypomastigotes (which can penetrate cell membranes) than with the amastigotes (which can not do so). By contrast, mannosidase treatment of the macrophages and the myoblasts caused a significant decrease in the ability of these cells to associate with either bloodstream or insect-derived trypomastigote forms. The capacity of mannosidase-treated macrophages to take up the non-invasive amastigotes was also reduced. These results, as a whole, suggest that mannose residues on the surface of the parasite modulate their binding to macrophages and myoblasts and that mannose residues on the surface of these host cells play a role in cell association with the parasite.