Bruno Pradines

One of our missions for the army and for the national referent center of malaria is the validation of new alternative diagnostic tools. We will develop new molecular tools to detect parasites with better specificity for diagnostic and better sensitivity to track asymptomatic patients and patients carrying gametocytes in areas in pre-elimination or elimination phases. In cases where microscopic examination cannot be performed, rapid diagnostic tests (RDT) are recommended by the World Health Organization. Most products target the Plasmodium falciparum histidine-rich protein 2 (HRP2). The team showed that pfhrp2 sequence variations, particularly with regard to certain amino acid repeats, can affect the sensitivity of HRP2-based RDT. In addition, misdiagnosis may also arise from pfhrp2 gene deletions hat prevent the expression of proteins by the parasites and were reported as the cause of false-negative diagnoses. We will evaluate and map the level of potential misdiagnoses in areas where French soldiers will be stay.

Since 2008, the unit of parasitology has been involved as laboratory associated to the national referent center of malaria (CNR paludisme). We will conduct epidemiological and clinical analyses of imported malaria cases, of patients from Mayotte and French Guiana and of malaria cases from endemic areas where French soldiers are staying or could stay in future, like Ivory Coast, Republic of Central Africa, Gabon, Congo, Senegal, Djibouti, Mauritania, Congo, Cameroon, Mali. In addition, we will evaluate the in vitro susceptibility of P. falciparum parasites (ex vivo and molecular markers) and clinical efficacy in patients (travelers and soldiers) to adapt chemoprophylaxis and malaria treatment and control strategies in French armed forces and in civilian recommendations.

The resistance of malaria to most antimalarial drugs has developed in Southeast Asia and has spread to Africa. The World Health Organization (WHO) has recommended artemisinin-based combination therapy (ACT) as the first-line treatment for malaria since 2005. As recently described in Southeast Asia, the emergence of P. falciparum resistance to artemisinin and its derivatives manifests as delayed parasite clearance following treatment with either artesunate monotherapy or ACT. In areas where artemisinin resistance is emerging, the partner drugs within the combination are under increasing pressure for the selection of resistance. In this context, the identification of molecular markers of resistance to these partner drugs is urgently needed for monitoring the emergence and spread of resistance to antimalarial drugs. It is important for us to have prediction of the level of resistance to each antimalarial drug, used both in prophylaxis or treatment of uncomplicated and severe malaria, in malaria endemic areas where we will deploy French soldiers. We will try to identify molecular markers of resistance to artemisinin derivatives, lumefantrine, piperaquine, pyronaridine, methylene blue… by different approach (selection of in vitro resistant strains by antimalarial pressure in continue culture, sequencing of wide genome of in vitro resistant strains or isolates or isolates collected in patients with clinical failure, site-directed mutagenesis, …).

The team will continue to participate in the identification of new antimalarial drugs by in vitro screening in collaboration with several international departments of medical chemistry and in the development of potential antimalarial drugs, and particularly methylene blue, in collaboration with international pharmaceutical laboratories. The development of these antimalarial drugs is based on evaluation of in vitro activity against P. falciparum clones, evaluation of ex vivo activity against P. falciparum field isolates from several areas, evaluation of in vivo activity in experimental models (uncomplicated malaria and cerebral malaria), and identification of the mode of action and potential mechanisms of resistance.

Vector-borne diseases constitute a threat to the operational capacity of armed forces personnel operating outside or stationed overseas.

a. Development of serological method based on antibody response against salivary proteins from vectors

We will continue to develop tools to evaluate the risks of exposure of soldiers to vector bites by identification of biomarkers of exposure by analyzing of arthropods salivary antigenic proteins and serological responses associated with the level of exposure. These tools allowed evaluate the effectiveness of anti-vectorial strategies, estimate and predict the risk of disease transmission and monitor mosquito populations.

b. Development of new tools for vector identification and surveillance of vector populations

Arthropod species including tick and mosquito vectors can be morphologically identified using taxonomic keys for endemic species in several geographic regions. However, morphological identification can be difficult because it requires some entomological expertise, and it is difficult to identify a specimen that is damaged or at an immature stage of its life cycle. We will collaborate with the team 1 to develop the identification by Maldi-Tof MS of arthropods collected in the field in entomological surveys conducted in French military bases and in areas where French soldiers are staying or could stay in future (Ivory Coast, Republic of Central Africa, Gabon, Congo, Senegal, Djibouti, Mauritania, Congo).

c. Evaluation of the vectorial capacity of mosquitoes in presence of antimalarial drugs

The gut microbial of vector mosquitoes grows after a blood meal and limits Plasmodium infection. Some antibiotics used in malaria affect bacterial growth and positively impact mosquito survival and permissiveness to Plasmodium. We will evaluate the impact of antimalarial drugs and antiparasitic drugs on the vectorial capacity of mosquitoes on vector-borne diseases transmission.

d. Evaluation of efficacy of repellent or insecticide

We will participate on the evaluation of the efficacy of new repellents or insecticides used for treating bed nets or uniforms in French army (effect on mosquitoes in insectarium, efficacy in the field) or long-lasting bed nets.

e. Entomological investigations and evaluation of control strategies

We will participate in the monitoring of entomological status of French military bases in sub-saharan Africa (Gabon, Ivory Coast, Republic of Central Africa, Senegal, Djibouti) and French Guiana in collaboration with the team 1. This surveillance is based on identification of vectors, study of behavior and evaluation of insecticide resistance. The team created the Impact Vector project which aimed was to evaluate the vector-borne disease risks for troops in combat situations. The team will also continue to contribute by its expertise to the investigation of epidemic disease, and to participate in the development of a global strategy for vector-control for the armed services. Additionally, we will continue to participate in the evaluation of antivectorial control programs in several areas in collaboration with oversea civilians units of entomology.

Drug resistance but also poor compliance (insufficient oversight or intolerance) and under-dosing (insufficient dosage, poor absorption, drug interactions or defects in drug metabolism) may contribute to prophylactic or clinical failure. It is important to evaluate the compliance in French troops or in travellers and to determine the determinants of non-compliance to improve recommendations and strategies. These studies will be conducted in collaboration with the CESPA (Centre d’épidémiologie et de santé publique des armées, Marseille).

The emergence of new vector borne disease or outbreaks of known vector borne disease in oversea areas where French soldiers are staying will be investigated in collaboration with the CESPA (Centre d’épidémiologie et de santé publique des armées, Marseille), with the Vitrome team 1, with teams of MEPHI and the UMR 190 Emerging viral diseases.