PCR characterization of isolates from various endemic areas: diversity and turn over of Plasmodium falciparum populations are correlated with transmission.

We have previously investigated the extend of genetic diversity within Plasmodium fakiparum isolates by using an improved cultivation technique for the cloning of parasites (Mazier et al. 1984) and further characterizing those by 4 distinct typing techniques @ruilhe et al. in preparation). Two series of 33 clones derived from 2 isolates obtained in primary attack cases were produced by cloning on the day of sampling and cultivating them together with hepatocytes feeder layers, a method which was found able to promote the growth of parasites not adapted to culture conditions. Drug response and karyotype analysis demonstrated a large degree of diversity among these clones. Restriction Fragment Length Polymorphism, revealed by probing with the pPFrep20 sequence, also confirmed the above results, however showed a high degree of genetic relatedness of the clones, which was unexpected from the results of the other techniques. Finally, amplification by polymerase chain reaction (PCR) of a polymorphic region of 4 genes (see below) revealed respectively 6 and 4 patterns of allelic forms in 24 clones for each isolate. Therefore, due to genetic relatedness of the clones, PCR did not prove to be the most discriminating technique. However, in view of its great sensitivity, it has the major advantage of being able to reveal the Co-existence of distinct parasite populations in an isolate without the need to cultivate parasites in order to produce enough DNA.