In vitro quantitative analysis of (3)H-uracil incorporation by Sarcocytis neurona to determine efficacy of anti-protozoal agents.

The research paper is about an experiment to measure the replication of a harmful parasite, Sarcocystis neurona, which causes equine protozoal myeloencephalitis (EPM) in horses. The experiment involved the use of various anti-parasitic drugs and a herbicide, Glyphosate, and the measurement of how these affect the parasite’s proliferation using a semi-automated assay incorporation of radioactive carbon-labeled uracil.

Experiment Setup

• The experiment sought to understand how parasite-specific incorporation of radioactive-tagged uracil ((3)H-uracil) reflects the replication process of Sarcocystis neurona, a protozoa associated with equine protozoal myeloencephalitis (EPM).
• Additionally, the researchers evaluated much-used anti-parasite drugs such as pyrimethamine, sulfadiazine, sulfamethoxazole, diclazuril, atovaquone, and tetracycline. The inclusion of glyphosate, typically a herbicide, was an unorthodox choice, potentially making this aspect of the study, a preliminary investigation of its anti-parasitic potential.
• The drugs were tested on varying densities of S. neurona parasites in a microtiter plate format to quantify the consumption of (3)H-uracil using semi-automated processes involving a plate harvester and a liquid scintillation counter.

Results

• The researchers found that their assay was most reliable when testing the anti-protozoal drugs on parasite densities greater than 90,000 individual merozoites (a life-stage form of the protozoan) per well.
• The herbicide Glyphosate showed reduced parasite proliferation even with as few as 900 individual merozoites. This makes Glyphosate the most potent agent tested in the experiment, even more so than pyrimethamine, the most widely used drug to treat EPM.
• However, the study notes that despite its potency in vitro (i.e., in the lab), data regarding the in vivo (inside a living organism) usage of Glyphosate are lacking, and it is unlikely that the compound can penetrate the central nervous system, where S. neurona actually affects horses.

Implications and Further Research

• According to the paper, the (3)H-uracil incorporation approach has potential for high throughput in clinical settings because of its quantitative results and suitability for semi-automation.
• Nevertheless, the study’s authors suggest further studies using a wider range of drug concentrations with optimally sized merozoite populations, to precisely define the potency of these potential anti-parasitic agents.