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Factors affecting the ability of isolated Plasmodium knowlesi merozoites to attach to and invade erythrocytes
Abstract:
Plasmodium knowlesi merozoites were prepared by the polycarbonate sieving method of Dennis, Mitchell, Butcher & Cohen (1975). Merozoite function was assayed by their attachment to and invasion of rhesus erythrocytes at 37 degrees C. The early merozoites from the culture chamber were the most invasive, although maximum numbers of merozoites appeared later. Merozoites were most stable when incubated at room temperature (23 degrees C). At 37 and 0 degrees C invasiveness rapidly declined to zero. Attachment was rapidly lost at 37 degrees C but was retained at 0 degrees C. Attachment was unchanged in the pH range 6.8--7.9 but invasion was reduced at pH 7.9. The presence of L-fucose, D-galactose, D-glucose, D-mannose, N-acetyl-D-galactosamine or N-acetyl-D-glucosamine did not reduce invasion. Attachment and invasion were greatly reduced or abolished by the presence of 2.5 mM EDTA or EGTA, by lactoperoxidase-catalysed iodination of the merozoites, or by treatment of the merozoites with trypsin at a concentration of 1 micrograms/ml or greater for 10 min at 23 degrees C.
Insights
This study investigated Plasmodium knowlesi merozoite invasion of rhesus red blood cells. Optimal invasion occurred with early merozoites, with stability maintained at room temperature and reduced by EDTA, iodination, or trypsin.
Area of Science:
- Malariology
- Parasitology
- Cell Biology
Background:
- Plasmodium knowlesi is a significant cause of malaria in humans.
- Understanding merozoite invasion mechanisms is crucial for developing antimalarial interventions.
Purpose of the Study:
- To characterize the factors affecting Plasmodium knowlesi merozoite attachment and invasion of rhesus erythrocytes.
- To identify optimal conditions for maintaining merozoite infectivity.
Main Methods:
- Merozoites were isolated using the polycarbonate sieving method.
- Attachment and invasion assays were performed at various temperatures, pH levels, and in the presence of specific chemicals.
- Merozoite surface proteins were investigated using lactoperoxidase-catalyzed iodination and enzymatic treatment.
Main Results:
- Early merozoites exhibited the highest invasion rates.
- Merozoite invasiveness and attachment were temperature-dependent, with optimal stability at room temperature (23°C).
- Invasion was impaired at pH 7.9, while attachment was unaffected across pH 6.8–7.9. EDTA, EGTA, iodination, and trypsin significantly reduced attachment and invasion.
Conclusions:
- Plasmodium knowlesi merozoite invasion is a complex process influenced by temperature, pH, and surface molecule integrity.
- Specific surface components are critical for merozoite attachment and invasion, representing potential targets for antimalarial drugs.