Search

Ex vivoassays of platelet function critically inform mechanistic and clinical hematology studies, where effects of divergent blood processing methods on platelet composition are apparent, but unspecified.

Sampling of saliva for diagnosing Plasmodium falciparuminfections is a safe, non-invasive alternative to sampling of blood. However, the use of saliva presents a challenge because lower concentrations of parasite DNA are present in saliva compared to peripheral blood. Therefore, a sensitive method is needed for detection of parasite DNA in saliva. This study utilized two recently reported “ultra-sensitive” PCR assays based on detection of the P. falciparummitochondrial cox3gene and the multi-copy nuclear varATSgene. The ultra-sensitive assays have an advantage over standard 18S rRNA gene-based PCR assay as they target genes with higher copy numbers per parasite genome. Stored saliva DNA samples from 60 Cameroonian individuals with infections previously confirmed by 18S rRNA gene PCR in peripheral blood were tested with assays targeting the cox3and varATSgenes. Overall, the standard 18S rRNA gene-based PCR assay detected P. falciparumDNA in 62% of the stored saliva DNA samples, whereas 77 and 68% of the samples were positive with assays that target the cox3and varATSgenes, respectively. Interestingly, the ultra-sensitive assays detected more P. falciparuminfections in stored saliva samples than were originally detected by thick-film microscopy (41/60 = 68%). When stratified by number of parasites in the blood, the cox3assay successfully detected more than 90% of infections using saliva when individuals had > 1000 parasites/μl of peripheral blood, but sensitivity was reduced at submicroscopic parasitemia levels. Bands on electrophoresis gels were distinct for the cox3assay, whereas faint or non-specific bands were sometimes observed for varATSand 18S rRNA that made interpretation of results difficult. Assays could be completed in 3.5 and 3 h for the cox3and varATSassays, respectively, whereas the 18S rRNA gene assays required at least 7 h. This study demonstrates that a PCR assay targeting the cox3gene detected P. falciparumDNA in more saliva samples than primers for the 18S rRNA gene. Non-invasive collection of saliva in combination with the proposed cox3primer-based PCR assay could potentially enhance routine testing of P. falciparumduring disease surveillance, monitoring, and evaluation of interventions for malaria elimination.

High-avidity antibodies (Abs) are acquired after a few Plasmodium falciparuminfections in low transmission areas, but it remains unclear if Ab avidity to different merozoite antigens increases with age in individuals with persistent antigenemia and, if so, when a fully mature Ab response occurs. The study used plasma samples collected between 1996 and 1998 from 566 individuals aged 4 to 84?years in Simbok, Cameroon, where residents received an estimated 1.6 infectious mosquito bites/person/night.