Drug resistance in the most deadly human malaria parasite, Plasmodium falciparum, has become the major concern in disease control strategies. It thus has motivated worldwide efforts to look for new antimalarial drugs and to develop high-throughput screenings for these new compounds. Although the microscopic evaluation of parasite mortality in the antimalarial tests remains as a "gold standard" to validate new tests, it is not suitable for massive screenings. The first highthroughput assay system to evaluate parasite sensitivity was based on the measurement of the metabolic activity of the parasite by a radioactive marker, [³H]-labelled hypoxanthine. Although this method is highly accurate and precise, it poses the problems of handling radioisotopes. To overcome this limitation, two other non-isotopic tests that measure parasite antigens by immune detection, namely lactate dehydrogenase, pLDH and Histidine-Rich Protein II, HRP2, were developed. Although these methods have been validated through comparisons with the microscopic and isotope methods, the present cost-per-reaction limits their value in large-scale studies. More recently, a new test based on SYBER Green I-based fluorescence has been developed. Although it offers several advantages as low cost and easily handling, SYBER green is an intercalating agent that will detect indiscriminately any contaminant DNA. We report here the development of an alternative, luminescence-based in vitro assay to screen new drugs against P. falciparum. The assay is based on a transgenic P. falciparum parasite clone stably and highly expressing luciferase throughout the asexual blood stages. Thus, after drug exposure the parasite survival is evaluated by enzyme activity. The results demonstrated high sensitivity and reproducibility of the test when compared to the isotopic method suggesting that this assay could be convenient for high-throughput screening of antimalarial drugs against P. falciparum. In addition it is simple, fast and inexpensive. Further validations of this assay will be presented.

(*correspondence hernando@icb.usp.br)

Acknowledgements: we thank Dr. Silvano Wendel, Director of the "Banco de Sangue do Hospital Sírio Libanês" for the kind supply of blood and serum for the in vitro culture of P. falciparum. The laboratory of HAP is supported by FAPESP (ID 01/09401-0) and "Conselho Nacional de Desenvolvimento Científico e Tecnológico" CNPq (ID 302572/2002-3).