Short-term culture ofPlasmodium knowlesi

The culture method developed by Geiman and co-workers has been modified to give average multiplication rates for Plasmodium knowlesi of at least six-fold in 24 h. Individual modifications have been assessed on the basis of parasite multiplication and [ 3 H]leucine incorporation into parasite protein. The second cycle of in vitro development which is particularly influenced by the conditions of culture was improved by: (i) culture of washed parasitized red cells in a medium containing dialysed homologous serum screened for its ability to support parasite growth; (ii) addition of ATP, Co-enzyme A (or pantothenate) and glutamine. We thank Mr E. D. Dennis and Miss Susan Wanstall for technical assistance. This work was supported by grants from the Medical Research Council and the World Health Organization.