[Detection of Plasmodium falciparum using the plasmid Pf rep 20 probe (preliminary report)]

A cloned repetitive DNA sequence (rep 20) labeled with 32P was evaluated as diagnostic probe for P. falciparum in 39 blood samples from Hainan and Yunan provinces. Its specificity and sensitivity were studied and compared with total genomic DNA probe isolated from P. f. Hainan Fcc1/HN isolate. The pPF rep 20 probe recognized the DNA of P. f. Hainan, Yunnan and Anhui isolates, but did not hybridize with the DNA of P. vivax, P. cynomolgi, P. knowlesi and P. yoelii. The genomic probe hybridized with the DNA of 3 isolates and cross-hybridized with the DNA of all the other Plasmodium species tested, but did not hybridize with host DNA. The plasmid rep 20 probe was able to detect parasitemia level of 0.001% in 20 microliters blood from culture and 10pg DNA of 3 P. f. isolates after 3 days film exposure. It could hybridize with the blood samples of P. f. patients from Hainan and Yunnan with a sensitivity of 95% (37/39). The genomic probe could detect the same parasitemia and DNA levels as plasmid rep 20 probe for Yunnan and Anhui isolates, and 0.0001% parasitemia and 1 pg DNA for Hainan isolate. It had a sensitivity of 97% (38/39) when used to detect patient samples. The results indicated that plasmid rep 20 probe was specific and rather sensitive to DNA of P. falciparum isolates from China and may be useful in epidemiological studies.