HTP antimalarial screen

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BOSTON—In the search for new drugs that target the malarial parasite Plasmodium sp., researchers need methods for screening small molecule libraries that offer higher throughputs than the current Giesma staining or radiolabeling methods. Answering this challenge, scientists at Harvard Medical School and Harvard School of Public Health developed a fluorescent DNA staining technique that is amenable to automation and high-throughput screening.

As they described in Antimicrobial Agents and Chemotherapy, the researchers first determined that the fluorescent dye DAPI exhibited higher S/N when used to stain parasite DNA in infected erythrocytes than either PicoGreen or SYBR Green 1.

Furthermore, when they compared the ability of dye staining to detect infection to the standard ³H-hypoxanthine incorporation assay, the researchers found the DAPI staining was equally sensitive when using a standard plate reader. The dye method was even more sensitive, however, when screened with an automated microscope—in this case, the CellWorX imaging platform.

The researchers then determined the IC₅₀ values of common antimalarials using DAPI staining or radiolabling and found the two methods offered comparable results. Furthermore, the DAPI assay was easily optimized to work not only in 96-well plates, but also 384-well plates. And when they used the assay to screen a library of almost 80,000 small molecules, the researchers identified 900 compounds with antimalarial activity, which they expect to further characterize.