The use of PCR genotyping in the assessment of recrudescence or reinfection after antimalarial drug treatment.

In the past, assessment of drug efficacy against Plasmodium falciparum malaria has been performed by microscopy, screening for parasites in blood smears. However, in areas of high endemicity, reappearing parasites might be derived from new inoculations and could be classified falsely as treatment failures. Recently, a number of studies have used polymerase chain reaction (PCR) analysis of detectable parasites after drug administration to discriminate new infections from true recrudescence. The feasibility, high sensitivity and high resolution of this technique proves that it will be practical and highly valuable in studies on both drug resistance and vaccine efficacy as well as the testing of novel antimalarial drugs. In this article, Georges Snounou and Hans-Peter Beck discuss the uncertainties in the interpretation of data inherent to the technical limitations of the PCR technique, and the constraints imposed by the biology of the parasite. They suggest that although genotyping can provide strong evidence for differentiating between true recrudescence and reinfection, it must be interpreted with caution. They also propose strategies that might help minimize these uncertainties.

Assessment of the humoral and cell-mediated immunity against the Plasmodium falciparum vaccine candidates circumsporozoite protein and SPf66 in adults living in highly endemic malarious areas of Papua New Guinea.

To assess natural immunity against the circumsporozoite (CS) protein and the synthetic vaccine SPf66, immunologic studies were carried out in a highly endemic malarious area of Papua New Guinea. Antibody prevalence, antibody titers, and T cell proliferation against both antigens were measured in 214 adults. Immunologic data were analyzed with respect to longitudinal malariologic and morbidity data. Evidence of genetic traits such as glucose-6-phosphate dehydrogenase deficiency and ovalocytosis was analyzed. Antibody prevalence was high, with 79% and 84% for CS protein and SPf66, respectively, while T cell proliferation was infrequent and low, with 14% and 12% responders, respectively. Anti-CS protein antibodies increased with age but showed no association to malaria indices or morbidity. No protective value was observed with T cell responses or with humoral response to SPf66. These results provide a first description of naturally developed immunity against SPf66 and suggest further studies in to fully understand the mechanism of immunity against this antigen.