Erythrocyte invasion profiles are associated with a common invasion ligand polymorphism in Senegalese isolates of Plasmodium falciparum.

Plasmodium falciparum parasites use multiple ligand-receptor interactions to invade human erythrocytes. Variant expression levels of members of the PfRh and PfEBA ligand families are associated with the use of different erythrocyte receptors, defining invasion pathways. Here we analyse a major polymorphism, a large sequence deletion in the PfRh2b ligand, and erythrocyte invasion profiles in uncultured Senegalese isolates. Parasites vary considerably in their use of sialic acid-containing and protease-sensitive erythrocyte receptors for invasion. The erythrocyte selectivity index was not related to invasion pathway usage, while parasite multiplication rate was associated with enhanced use of a trypsin-resistant invasion pathway. PfRh2b protein was expressed in all parasite isolates, although the PfRh2b deletion was present in a subset (approximately 68%). Parasites with the PfRh2b deletion were found to preferentially utilize protease-resistant pathways for erythrocyte invasion. Sialic acid-independent invasion is reduced in parasites with the PfRh2b deletion, but only in isolates derived from blood group O patients. Our results suggest a significant role for PfRh2b sequence polymorphism in discriminating between alternative erythrocyte receptors for invasion and as a possible determinant of virulence.

[Evaluation of malaria rapid diagnostic test Optimal-IT® pLDH along the Plasmodium falciparum distribution limit in Mauritania]. / Evaluation du test de diagnostic rapide du paludisme OptiMal-IT® pLDH à la limite de la distribution de Plasmodium falciparum en Mauritanie.

Performance of the malaria Rapid Diagnostic Test (RDT) OptiMal-IT® was evaluated in Mauritania where malaria is low and dependent on a short transmission season. Slide microscopy was considered as the reference method of diagnosis. Febrile patients with suspected malaria were recruited from six health facilities, 3 urban and 3 rural, during two periods (December 2011 to February 2012, and August 2012 to March 2013). Overall, 780 patients were sampled, with RDT and thick blood film microscopy results being obtained for 759 of them. Out of 774 slides examined, of which 200 were positive, P. falciparum and P. vivax mono-infections were detected in 63.5% (127) and 29.5% (59), while P. falciparum/P. vivax coinfections were detected in 7% (14). Both species were observed in all study sites, although in significantly different proportions. The proportions of thick blood film and OptiMal-IT® RDT positive individuals was 26.3% and 30.3% respectively. Sensitivity and specificity of OptiMal-IT® RDT were 89% [95% CI, 84.7-93.3] and 91.1% [88.6-93.4]. Positives and negative predictive values were 78.1% [72.2-83.7] and 95.9% [94.1-97.5]. These diagnostic values are similar to those generally reported elsewhere, and support the use of RDTs as the main diagnostic tool for malaria in Mauritanian health facilities. In the future, choice of RDTs to be used must take account of thermostability in a hot, dry environment and their ability to detect P. falciparum and P. vivax.

[Use of dried blood spots in early diagnosis of HIV-1 infection in children born to HIV-infected mothers as part of the prevention of mother-to-child transmission in Benin]. / Utilisation des prélèvements capillaires sur buvard dans le diagnostic précoce de l'infection à VIH-1 chez des enfants nés de mères infectées dans le cadre de la prévention de la transmission mère-enfant au Bénin.

The goal of this study was to evaluate using the molecular diagnosis, infection transmission rate of HIV in children born to HIV-1 positive mothers as part of the prevention of mother-to-child transmission (PMTCT) in Benin. The sample consisted of 524 dried blood spots (DBS) of children born to HIV-1 positive mothers, from 30 sites (PMTCT) taken between October 2009 and June 2010. The diagnosis of HIV-1 was performed by the qualitative detection of viral nucleic acids (RNA and DNA) in DBS on filter paper using the Abbott RealTime(®) HIV-1 Qualitative assay. We found that 51 DBS were positive (9.7%) and 473 were negative (90.3%). The failure rate of PMTCT among 420 mothers who received antiretroviral prophylaxis was 6.7% (28/420). This failure rate was significantly higher among children born to infected mothers on antiretroviral monotherapy than on triple therapy (HAART). The results of our study enrich the data in the literature on highly active antiretroviral chemoprophylaxis to reduce the transmission of HIV-1 from mother to child.