COMPARATIVE TEST OF DNA PROBES FOR DETECTION OF PLASMODIUM-VIVAX CIRCUMSPOROZOITE PROTEIN POLYMORPHS VK-247 AND VK-210

Oligonucleotide probes specific to the characteristic repeat sequences of two alleles of the circumsporozoite protein gene of Plasmodium viv ax (VK 210 and VK 247) were selected, synthesized, and tested on match ed blood and sporozoite DNA amplified by polymerase chain reaction fro m 182 cases naturally acquired in Thailand. Probe results were compare d to those of circumsporozoite phenotype-specific ELISAs used to evalu ate sporozoites from the same cases. There was a 96% agreement between probe results for blood and for sporozoites. Although there was also a nearly complete agreement between probe and ELISA results for cases producing only VK 210 or VK 247 sporozoites, the probes detected 45% m ore mixed infections than did the ELISAs when used to test specimens f rom western and southern Thailand; there was no discrepancy when mixed cases from Cambodia were tested. Examination of Southern blots from a mbiguous mixed cases demonstrated the presence of both genes, suggesti ng suppression of VK 247 in some mixed cases to numbers below those de tectable by the ELISA.