Unveiling P. vivax invasion pathways in Duffy-negative individuals.

Vivax malaria has long been thought to be absent from sub-Saharan Africa owing to the high proportion of individuals lacking the Duffy antigen receptor for chemokines (DARC) in their erythrocytes. The interaction between P. vivax Duffy-binding protein (PvDBP) and DARC is assumed to be the main pathway used by merozoites to invade reticulocytes. However, the increasing number of reports of vivax malaria cases in genotypically Duffy-negative (DN) individuals has raised questions regarding the P. vivax invasion pathway(s). Here, we show that a subset of DN erythroblasts transiently express DARC during terminal erythroid differentiation and that P. vivax merozoites, irrespective of their origin, can invade DARC+ DN erythroblasts. These findings reveal that a large number of DN individuals may represent a silent reservoir of deep P. vivax infections at the sites of active erythropoiesis with low or no parasitemia, and it may represent an underestimated biological problem with potential clinical consequences in sub-Saharan Africa.

Potential hidden Plasmodium vivax malaria reservoirs from low parasitemia Duffy-negative Ethiopians: Molecular evidence.

BACKGROUND: The interaction between the Plasmodium vivax Duffy-binding protein and the corresponding Duffy Antigen Receptor for Chemokines (DARC) is primarily responsible for the invasion of reticulocytes by P. vivax. The Duffy-negative host phenotype, highly prevalent in sub-Saharan Africa, is caused by a single point mutation in the GATA-1 transcription factor binding site of the DARC gene promoter. The aim of this study was to assess the Duffy status of patients with P. vivax infection from different study sites in Ethiopia. METHODS: A cross-sectional study was conducted from February 2021 to September 2022 at five varying eco-epidemiological malaria endemic sites in Ethiopia. Outpatients who were diagnosed with P. vivax infection (pure and mixed P. vivax/P. falciparum) by microscopy and Rapid Diagnostic Test (RDT) were subjected to PCR genotyping at the DARC promoter. The associations between P. vivax infection, host genotypes and other factors were evaluated. RESULT: In total, 361 patients with P. vivax infection were included in the study. Patients with pure P. vivax infections accounted for 89.8% (324/361), while the remaining 10.2% (37/361) had mixed P. vivax/P. falciparum infections. About 95.6% (345/361) of the participants were Duffy-positives (21.2% homozygous and 78.8%, heterozygous) and 4.4% (16/361) were Duffy-negatives. The mean asexual parasite density in homozygous and heterozygous Duffy-positives was 12,165 p/µl (IQR25-75: 1,640-24,234 p/µl) and11,655 p/µl (IQR25-75: 1,676-14,065 p/µl), respectively, significantly higher than that in Duffy-negatives (1,227p/µl; IQR25-75: 539-1,732p/µl). CONCLUSION: This study confirms that Duffy-negativity does not provide complete protection against P. vivax infection. The development of P. vivax-specific elimination strategies, including alternative antimalarial vaccines should be facilitated by a better understanding of the epidemiological landscape of vivax malaria in Africa. More importantly, low parasitemia associated with P. vivax infections in Duffy-negative patients may represent hidden reservoirs of transmission in Ethiopia.

Vivax malaria in Duffy-negative patients shows invariably low asexual parasitaemia: implication towards malaria control in Ethiopia.

BACKGROUND: The increase in detections of Plasmodium vivax infection in Duffy-negative individuals in Africa has challenged the dogma establishing the unique P. vivax Duffy Binding Protein-Duffy antigen receptor for chemokines (PvDBP-DARC) pathway used by P. vivax merozoites to invade reticulocytes. Information on the impact of Duffy antigen polymorphisms on the epidemiology of P. vivax malaria remains elusive. The objective of this study was to determine the distribution of asexual parasitaemia of P. vivax according to the Duffy antigen polymorphisms in Ethiopia. METHODS: DNA was extracted from dried blood spots (DBS) collected from prospectively recruited 138 P. vivax-infected patients from health centres. The identification and estimation of P. vivax asexual parasitaemia were performed by microscopic examination and quantitative real-time polymerase chain reaction (PCR). Duffy genotyping was conducted by DNA sequencing in a total of 138 P.vivax infected samples. RESULTS: The proportion of Duffy-negatives (FY*BES/FY*BES) in P. vivax infected patients was 2.9% (4/138). Duffy genotype FY*B/FY*BES (48.6%) was the most common, followed by FY*A/FY*BES genotype (25.4%). In one patient, the FY*02 W.01/FY*02 N.01 genotype conferring a weak expression of the Fyb antigen was observed. All P.vivax infected Duffy-negative patients showed low asexual parasitaemia (≤ 110 parasites/µL). The median P. vivax parasitaemia in Duffy-negative patients (53 parasites/µL) was significantly lower than those found in homozygous and heterozygous individuals (P < 0.0001). CONCLUSION: Plasmodium vivax in Duffy-negative patients shows invariably low asexual parasitaemia. This finding suggests that the pathway used by P. vivax to invade Duffy-negative reticulocytes is much less efficient than that used in Duffy-positives. Moreover, the low asexual parasitaemia observed in Duffy-negative individuals could constitute an 'undetected silent reservoir', thus likely delaying the elimination of vivax malaria in Ethiopia.

Plasmodium vivax blood stage invasion pathways: Contribution of omics technologies in deciphering molecular and cellular mechanisms.

Vivax malaria is an infectious disease caused by Plasmodium vivax, a parasitic protozoan transmitted by female Anopheline mosquitoes. Historically, vivax malaria has often been regarded as a benign self-limiting infection due to the observation of low parasitemia in Duffy-positive patients in endemic transmission areas and the virtual absence of infections in Duffy-negative individuals in Sub Saharan Africa. However, the latest estimates show that the burden of the disease is not decreasing in many countries and cases of vivax infections in Duffy-negative individuals are increasingly reported throughout Africa. This raised questions about the accuracy of diagnostics and the evolution of interactions between humans and parasites. For a long time, our knowledge on P. vivax biology has been hampered due to the limited access to biological material and the lack of robust in vitro culture methods. Consequently, little is currently known about P. vivax blood stage invasion mechanisms. The introduction of omics technologies with novel and accessible techniques such as third generation sequencing and RNA sequencing at single cell level, two-dimensional electrophoresis, liquid chromatography, and mass spectrometry, has progressively improved our understanding of P. vivax genetics, transcripts, and proteins. This review aims to provide broad insights into P. vivax invasion mechanisms generated by genomics, transcriptomics, and proteomics and to illustrate the importance of integrated multi-omics studies.

Le paludisme à Plasmodium vivax est une maladie infectieuse causée par un parasite protozoaire Plasmodium vivax, transmis par les moustiques Anophèle femelles. Historiquement, le paludisme à P. vivax a souvent été considéré comme une infection bénigne en raison de l'observation d'une faible parasitémie chez les patients Duffy-positifs dans les zones d'endémie et de la quasi-absence d'infections chez les individus Duffy-négatifs vivant majoritairement en Afrique subsaharienne. Cependant, les dernières estimations montrent que le poids de la maladie ne diminue pas dans de nombreux pays et que des cas d'infections à P. vivax chez des individus Duffy-négatifs sont de plus en plus souvent observés en Afrique. Cela soulève des interrogations sur la précision des diagnostics et l'évolution des interactions hôte-parasite. Pendant longtemps, nos connaissances sur la biologie de P. vivax ont été entravées par un accès limité au matériel biologique et un manque de méthodes robustes pour la culture in vitro. Par conséquent, nous n'avons encore que peu d'informations concernant les mécanismes d'invasion des stades sanguins de P. vivax. L'introduction des technologies dites « omiques ¼, avec le développement de techniques innovantes et abordables telles que le séquençage d'ADN de troisième génération, le séquençage ARN à l'échelle de la cellule « single-cell ¼, l'électrophorèse bidimensionnelle, la chromatographie liquide et la spectrométrie de masse, a progressivement amélioré notre compréhension des gènes, des transcrits et des protéines de P. vivax. Cette revue a non seulement pour but de fournir un aperçu général des mécanismes d'invasion de P. vivax acquis grâce aux techniques génomiques, transcriptomiques et protéomiques mais également d'illustrer l'importance de la complémentarité de ces approches.

[The digital portfolio as the cornerstone of clinical learning]. / Le portfolio numérique comme clé de voûte de l'apprentissage clinique.

The 2009 training reference frame was designed in accordance with the development of students' learning capacities and the French health context. As part of this necessary development, nurse training is based on a three-party contract between the student, the trainer and the internship tutor. The portfolio, used as an assessment aid and a tool to monitor learning, makes the progress and the acquisition of skills visible during the three years of training. As it is digitised, information concerning the internship can be shared in real time.

[Outpatient medication usage during hospitalization]. / Utilisation des médicaments achetés en ville par les patients hospitalisés: quelles mesures correctives proposer?

OBJECTIVE: To study the frequency and circumstances of patients' use of outpatient medications prescribed by their GP during hospitalization and to assess means of reducing this use. METHOD: A prevalence study of medication use was conducted at Saint Joseph's Hospital in Paris. On one day, we used a specific questionnaire to interview 151 patients in 11 different units about the type and amount of medications they had brought with them to the hospital and the type and amount they had used. RESULTS: Overall, 61% had brought their prescription medication with them, and 36% had used some of it, sometimes without informing the medical staff. In 75% of these cases, these drugs were available from the hospital pharmacy. DISCUSSION: Possible corrective steps include both technological improvements (computerized prescription) and organizational measures: systematic inquiry about and consideration of outpatient prescriptions at admission, use of validated prescription/substitution aids (Comedims), and patient information and education about drug substitutions and interactions.