Clones have been derived by limiting dilution from recent isolates of Plasmodium falciparum from Africa and Brazil. These clones have been characterized for pyrimethamine and chloroquine sensitivity and/or isoenzyme type. Clones obtained from an isolate containing a mixture of GPI isoenzyme types were found to have (with one exception) only GPI-1 or GPI-2. Clones differing 1,000-fold in pyrimethamine resistance were derived from a single isolate from Brazil which was resistant to both pyrimethamine and chloroquine. Several levels of chloroquine sensitivity were observed in the isolates studied. All clones showed levels of chloroquine sensitivity similar to that of their parent isolates. The KZ1 isolate from East Africa had an intermediate level of chloroquine resistance and a flat dose-response curve and each of its clones had a similar dose-response curve, indicating that the intermediate level of chloroquine resistance did not result from the KZ1 isolate's being a mixture of clones with high and low sensitivity.
Present address: Papua New Guinea Institute of Medical Research, P.O. Box 378, Madang, Papua New Guinea.