Plasmodium falciparum in culture: use of outdated erthrocytes and description of the candle jar method.

Plasmodium falciparum has been cultured continuously in a simplified technique using plastic petri dishes in a candle jar. This method has the advantage of being readily adaptable to many experiments, especially those requiring numerous replicates. Experiments using this method have allowed examination of some factors responsible for variations in parasite multiplication rates. Generally, fetal calf serum is not comparable to human serum, modifications to the RPMI 1640 medium are usually deleterious, and erythrocytes aged in citrated plasma are better for malarial cultures than freshly obtained cells; thus, erythrocytes outdated by blood-bank standards could provide a readily available supply of cells for large-scale production of malarial antigens. Continuous culture of Plasmodium falciparum in vitro was first obtained by a method providing for a slow flow of medium over a thin settled layer of human erythrocytes (Trager and Jensen, 1976; Trager, 1976). This method lends itself to partial automation and provides for continuous production of parasite material. It is not convenient, however, for the study of the many different factors that might affect growth of the parasites. For this purpose we developed a simplified method using plastic petri dishes in a candle jar. The essentials of this petri dish method have already been briefly described (Trager and Jensen, 1976). Here we present full details of the method and its application in demonstrating the feasibility of using outdated erythrocytes and for testing certain other modifications of the culture conditions. MATERIALS AND METHODS