Diagnosis of Trypanosoma evansi by the polymerase chain reaction (PCR)

抄録

Trypanosoma evansi and the three subspecies of T. brucei are indistinguishable from each other morphologically and are thought to be very closely related evolutionarily. The most notable molecular difference between T. evansi and the T. brucei subspecies is the structure of the DNA molecules found in their kinetoplast, a subcellular organelle located near the flagellar pocket. We have exploited this difference in kDNA sequence and organization to develop a polymerase chain reaction (PCR)-based assay that can distinguish between T. evansi and T. brucei. Oligonucleotide primers spaced about 370 bp apart on the T. evansi kDNA sequence generate a PCR-amplification product when total T. evansi DNA is used as the template, whereas no amplification product occurs when total DNA from T. brucei or Leishmania is the template. In contrast, when PCR primers specific for three different nuclear DNA sequences of T. brucei -a 177-bp repeat, the procyclin gene or the spliced leader gene - are used in similar PCR amplifications, identical PCR products are obtained from the T. brucei and T. evansi template DNAs. Thus, the nuclear DNA sequences of T. evansi and T. brucei are very similar, but their kDNAs are sufficiently different to serve as the basis for PCR-based diagnosis of the two trypanosome species.