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Labeled probes inserted in the macrophage membrane are transferred to the parasite surface and internalized during
1Laboratório de Biologia Celular e Tecidual, Centro de Biociências e Biotecnologia, Universidade Estadual do Norte Fluminense, Rio de Janeiro, RJ, Brasil.
Abstract:
Tachyzoites of Toxoplasma gondii attach to the macrophage surface and are internalized either by a phagocytic process, which can be inhibited by cytochalasin D, or by an active process, independent of host cell actin. Previous studies have shown that parasite attachment induces the secretion of macromolecules found in the apical organelles (micronemes and rhoptries) and subsequent/concomitant parasite internalization with the formation of a membrane-bound vacuole known as the parasitophorous vacuole. In the present study we labeled the macrophage surface with fluorescent probes that bind to proteins (DiIC16) and lipids (DTAF) and then allowed control or cytochalasin-D-treated cells to interact with untreated or antibody-coated tachyzoites of T. gondii. The interaction was interrupted at different time points by fixation and the distribution of the probes was analyzed by confocal laser scanning microscopy. Following attachment of the parasites to the macrophage surface, intense labeling of the parasite surface was observed, suggesting transfer of components of the macrophage surface to the parasite surface. Nonadherent parasites were not labeled. Immediately after attachment, most of the parasites were internalized and labeling of the internalized parasites as well as of the parasitophorous vacuole, probably of its membrane, was evident, indicating that surface components of the macrophage are involved in the formation of the parasitophorous vacuole.
Insights
Macrophage surface components transfer to tachyzoites of Toxoplasma gondii during invasion, aiding parasitophorous vacuole formation. This process is crucial for understanding host-pathogen interactions in toxoplasmosis.
Area of Science:
- Cell biology
- Immunology
- Parasitology
Background:
- Toxoplasma gondii tachyzoites invade macrophages via actin-dependent or independent pathways.
- Parasite attachment triggers secretion and internalization, forming a parasitophorous vacuole.
Purpose of the Study:
- To investigate the role of macrophage surface components in Toxoplasma gondii internalization and parasitophorous vacuole formation.
Main Methods:
- Macrophages were labeled with fluorescent probes for proteins and lipids.
- Interaction with T. gondii tachyzoites was analyzed using confocal microscopy.
- Cytochalasin D was used to differentiate invasion pathways.
Main Results:
- Macrophage surface components were transferred to the tachyzoite surface upon attachment.
- Internalized tachyzoites and the parasitophorous vacuole membrane showed labeling.
- This transfer was specific to adherent parasites.
Conclusions:
- Macrophage surface proteins and lipids are incorporated into the tachyzoite surface during invasion.
- These host-derived components are involved in the formation of the parasitophorous vacuole.
- This highlights a novel host-pathogen interaction mechanism in T. gondii infection.