Activity of immunoglobulin G-coated red cell ghosts containing pentamidine against macrophage-contained Leishmania in
Abstract:
Pentamidine is an antileishmanial agent that is often toxic at therapeutic dosages. The obligate intramacrophage localization of Leishmania indicates that encapsulation of pentamidine within a carrier phagocytized by macrophages (IgG-coated sheep red cell ghosts) might improve activity. In in vitro experiments, treatment of infected mouse macrophages for 1 hour with a mean of 1.4 micrograms of encapsulated drug resulted in a calculated drug concentration of 180 micrograms/ml macrophage, and in 73% suppression of organism multiplication within the macrophages after 4-5 days of further cultivation. In comparison, 27 micrograms unencapsulated drug/ml was needed for similar suppression. Electron microscopic examination 5 hours after phagocytosis of IgG-ghosts revealed that 95% of organisms were adjacent to ghosts in phagolysosomes. Fusion of drug carrier with phagolysosome containing drug target is therefore an important step in carrier-mediated parasite suppression in this model. These results suggest that IgG-coated erythrocyte ghosts containing pentamidine have potential as an antileishmanial formation.
Insights
Encapsulating the antileishmanial drug pentamidine in IgG-coated red blood cell ghosts significantly enhanced its activity against Leishmania within macrophages. This targeted delivery system reduced toxicity and improved efficacy compared to the unencapsulated drug.
Area of Science:
- Parasitology
- Drug Delivery Systems
- Immunology
Background:
- Pentamidine is a crucial antileishmanial agent but exhibits toxicity at therapeutic doses.
- Leishmania parasites reside within macrophages, necessitating targeted drug delivery strategies.
- Encapsulation of pentamidine in phagocytizable carriers may enhance efficacy and reduce host toxicity.
Purpose of the Study:
- To evaluate the efficacy of pentamidine encapsulated in IgG-coated sheep red blood cell ghosts against Leishmania.
- To determine if this targeted delivery system improves antileishmanial activity compared to unencapsulated pentamidine.
- To investigate the mechanism of action, focusing on the interaction between drug carriers and infected macrophages.
Main Methods:
- In vitro culture of Leishmania-infected mouse macrophages.
- Treatment with encapsulated and unencapsulated pentamidine.
- Quantification of parasite multiplication suppression.
- Electron microscopy to visualize drug carrier-parasite interaction within phagolysosomes.
Main Results:
- Encapsulated pentamidine achieved 73% suppression of Leishmania multiplication at a lower effective concentration compared to the unencapsulated form.
- Electron microscopy confirmed that 95% of Leishmania parasites were adjacent to IgG-ghosts within phagolysosomes 5 hours post-phagocytosis.
- Successful fusion of drug carriers with parasitized phagolysosomes was observed, indicating effective drug delivery.
Conclusions:
- IgG-coated erythrocyte ghosts serve as an effective carrier for pentamidine delivery to Leishmania-infected macrophages.
- This targeted approach shows potential for improving antileishmanial therapy by enhancing drug activity and potentially reducing systemic toxicity.
- The fusion of drug carriers with phagolysosomes is a key mechanism for this carrier-mediated parasite suppression.
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