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Anionic site behavior in Leishmania and its role in the parasite-macrophage interaction
E M Saraiva1, M A Vannier-Santos, F C Silva-Filho
1Laboratório de Ultraestrutura Celular, Instituto de Biofísica Carlos Chagas Filho, Rio de Janeiro, Brasil.
Abstract:
The behavior of cationized ferritin (CF) binding sites on the surface of Leishmania mexicana amazonensis (amastigotes, infective and non-infective promastigotes) and their participation in the interaction with macrophages were evaluated. Glutaral-dehyde-fixed parasites treated with CF present a uniform labelling over the whole cell surface. However, living parasites displayed CF patches and caps. Capping was usually seen towards the anterior (flagellated) portion of the cells, where shedding phenomena took place. These processes were inhibited by sodium azide but not by low temperature (4 degrees C). CF treatment of non-infective promastigotes led to an increase in their uptake by macrophages, whereas the uptake of amastigotes or infective promastigotes was not significantly altered. The effect of CF on the parasite surface charge was analyzed by whole-cell microelectrophoresis. The mean electrophoretic mobility (EPM) of non-infective promastigotes was decreased by 26%, while once again the other parasite forms were not significantly affected. Transmission electron microscopy of mouse peritoneal macrophage cultures, fixed after interaction with CF-labelled parasites, revealed that both amastigotes and infective promastigotes quickly removed bound CF. Therefore CF was seen neither in parasite-macrophage attachment areas nor in parasitophorous vacuoles. On the contrary, non-infective promastigote-macrophage attachment areas were remarkably large and preferentially comprised CF-labelled membranes. These results strongly suggest an important participation of cell surface anionic sites in the L. mexicana amazonensis-macrophage interaction.
Insights
Cationized ferritin (CF) binding to Leishmania mexicana amazonensis surfaces affects macrophage interactions. Non-infective forms show increased uptake, suggesting anionic sites are crucial for parasite-macrophage binding.
Area of Science:
- Parasitology
- Cell Biology
- Immunology
Background:
- Leishmania mexicana amazonensis is a parasite that infects macrophages.
- Understanding parasite-host interactions is crucial for developing treatments.
Purpose of the Study:
- To investigate cationized ferritin (CF) binding sites on Leishmania mexicana amazonensis.
- To determine the role of these sites in macrophage interactions.
Main Methods:
- Parasite surface labeling with CF.
- Observation of CF capping and shedding.
- Macrophage uptake assays.
- Microelectrophoresis for surface charge analysis.
- Transmission electron microscopy (TEM).
Main Results:
- Living parasites showed CF patching and capping, inhibited by sodium azide.
- CF treatment increased non-infective promastigote uptake by macrophages.
- Microelectrophoresis indicated altered surface charge on non-infective promastigotes.
- TEM revealed preferential CF-labeled membrane attachment for non-infective promastigotes to macrophages.
Conclusions:
- Cell surface anionic sites play a significant role in Leishmania mexicana amazonensis-macrophage interactions.
- Non-infective promastigotes may utilize these anionic sites for enhanced macrophage binding.