Quantification of malaria antigens PfHRP2 and pLDH by quantitative suspension array technology in whole blood, dried blood spot and plasma.

BACKGROUND: Malaria diagnostics by rapid diagnostic test (RDT) relies primarily on the qualitative detection of Plasmodium falciparum histidine-rich protein 2 (PfHRP2) and Plasmodium spp lactate dehydrogenase (pLDH). As novel RDTs with increased sensitivity are being developed and implemented as point of care diagnostics, highly sensitive laboratory-based assays are needed for evaluating RDT performance. Here, a quantitative suspension array technology (qSAT) was developed, validated and applied for the simultaneous detection of PfHRP2 and pLDH in a variety of biological samples (whole blood, plasma and dried blood spots) from individuals living in different endemic countries. RESULTS: The qSAT was specific for the target antigens, with analytical ranges of 6.8 to 762.8 pg/ml for PfHRP2 and 78.1 to 17076.6 pg/ml for P. falciparum LDH (Pf-LDH). The assay detected Plasmodium vivax LDH (Pv-LDH) at a lower sensitivity than Pf-LDH (analytical range of 1093.20 to 187288.5 pg/ml). Both PfHRP2 and pLDH levels determined using the qSAT showed to positively correlate with parasite densities determined by quantitative PCR (Spearman r = 0.59 and 0.75, respectively) as well as microscopy (Spearman r = 0.40 and 0.75, respectively), suggesting the assay to be a good predictor of parasite density. CONCLUSION: This immunoassay can be used as a reference test for the detection and quantification of PfHRP2 and pLDH, and could serve for external validation of RDT performance, to determine antigen persistence after parasite clearance, as well as a complementary tool to assess malaria burden in endemic settings.

Surveillance of the efficacy of artesunate and mefloquine combination for the treatment of uncomplicated falciparum malaria in Cambodia.

Artesunate and mefloquine combination treatment has been used since 2000 in Cambodia as the first-line drug for the treatment of uncomplicated falciparum malaria. In order to assess its efficacy and safety, the national malaria control programme conducted 14 therapeutic efficacy studies with the drug combination between 2001 and 2004 at nine sites. In 2001 and 2002, co-blister packs of artesunate and mefloquine were used, whereas in 2003 and 2004, drugs were given individually from a bulk pack at a total dose of 12 mg/kg of artesunate and 25 mg/kg of mefloquine over 3 days. A total of 1025 patients were enrolled over the 4 years and 977 were follow-up during the period of 28 days. The PCR-corrected cure rates ranged from 85.7% to 100% with an overall cure rate of 95.8% (920/960). The studies in 2002 showed also that co-blister packs used on the basis of age and not on the basis of weight could lead to underdosed regimens but without any detectable effect on the treatment outcome. The follow-up period was extended from 28 to 42 days in three sites in 2004. A total of 219 among 255 were follow-up until day 42. The cure rate decreased but not significantly from 90.1% (73/81) with 28 days follow-up to 79.3% (46/58) with 42 days follow-up in Pailin, whereas the cure rate remained at 100% in the two other sites. Side effects were common, especially dizziness, but were mild and transient and patients recovered without any medical intervention.

Efficacy and safety of dihydroartemisinin-piperaquine (Artekin) in Cambodian children and adults with uncomplicated falciparum malaria.

The safety and efficacy of a novel combination of dihydroartemisinin (DHA) and piperaquine, Artekin (Holleykin Pharmaceuticals), were assessed in 106 patients (76 children and 30 adults) with uncomplicated falciparum malaria from 2 remote areas in Cambodia. Age-based doses were given at 0, 8, 24, and 32 h. Mean total DHA and piperaquine doses were 9.1 and 73.9 mg/kg, respectively, for children and 6.6 and 52.9 mg/kg for adults. All patients became aparasitemic within 72 h. Excluding the results for 1 child who died on day 4, there was a 96.9% 28-day cure rate (98.6% in children and 92.3% in adults). Patients who had recrudescent infection received low doses of Artekin. Side effects were reported by 22 patients (21%) but did not necessitate premature cessation of therapy. Although Artekin is a promising and inexpensive option for antimalarial therapy, further efficacy and pharmacokinetic studies are needed, especially for its use in children.