In Vitro Culture and Drug Sensitivity Assay of Plasmodium falciparum with Nonserum Substitute and Acute-Phase Sera

The short-term in vitro growth of Plasmodium falciparum parasites in the asexual erythrocytic stage and the in vitro activities of eight standard antimalarial drugs were assessed and compared by using RPMI 1640 medium supplemented with 10% nonimmune human serum, 10% autologous or homologous acute-phase serum, or 0.5% Albumax I (lipid-enriched bovine serum albumin). In general, parasite growth was maximal with autologous (or homologous) serum, followed by Albumax I and nonimmune serum. The 50% inhibitory concentrations (IC(50)s) varied widely, depending on the serum or serum substitute. The comparison of IC(50)s between assays with autologous and nonimmune sera showed that monodesethylamodiaquine, halofantrine, pyrimethamine, and cycloguanil had similar IC(50)s. Although the IC(50)s of chloroquine, monodesethylamodiaquine, and dihydroartemisinin were similar with Albumax I and autologous sera, the IC(50)s of all test compounds obtained with Albumax I differed considerably from the corresponding values obtained with nonimmune serum. Our results suggest that Albumax I and autologous and homologous sera from symptomatic, malaria-infected patients may be useful alternative sources of serum for in vitro culture of P. falciparum isolates in the field. However, autologous sera and Albumax I do not seem to be suitable for the standardization of isotopic in vitro assays for all antimalarial drugs.