Most prevalent arthropod-borne viral disease in tropical and subtropical countries, dengue remains a major public health concern worldwide. Dengue virus (DENV) is transmitted to humans by the bite of Aedes spp. mosquitoes, and can cause disease with a wide range of severities, from inapparent infection to classical dengue fever and severe, potentially fatal, forms of dengue. There are no specific antiviral therapeutics for dengue to date and the potential efficiency of a recently licensed vaccine remains uncertain. Current vector control measures regularly fail to prevent and control the emergence of epidemics. There is an urgent need to guide new vector control tools in order to determine the most effective interventions. Dengue is caused by one of four serotypes (DENV-1 to -4). DENV circulation and evolution are characterized by extensive genetic diversity and rapid turnover of DENV genotypes or lineages, including genotype replacements within the same serotype, leading to changes in dengue epidemiology or severity. However, the factors driving DENV evolution are still poorly understood. One promising strategy aiming at blocking DENV transmission involves the release of Aedes aegypti mosquitoes colonized by the endosymbiotic bacterium Wolbachia. This strategy is currently deployed in 12 countries including Noumea, New Caledonia (NC) by the World Mosquito Program (WMP). However, although promising results, this method might have limitations in the future. Indeed the impact of Wolbachia deployment on DENV evolution is unknown. In DenWOlution, we will take advantage of the release of wMel-infected Ae. aegypti in Noumea to investigate the reciprocal impact of the Wolbachia strategy and DENV evolution prior, during and after the intervention. NC represents an ideal setting to study the dynamics underlying DENV transmission and evolution under environmental constraints because: Ae. aegypti is the main vector for arboviruses, an effective arbovirus and entomological surveillance network has been in place for decades; DENV epidemiology is currently evolving from epidemic to endemic. In our project, we hypothesize that wMel-infected Ae. aegypti will shape both the evolution and the epidemiological dynamics of DENV in NC, and that DENV evolution upon environmental changes (Wolbachia-driven selective pressure) will ultimately impair the efficiency of the Wolbachia strategy. Thus, we intend to: i) Determine if DENV previous evolution in NC was stochastic or deterministic and how it impacted DENV epidemiological pattern; ii) Determine the reciprocal impact between DENV evolution and the Wolbachia strategy and iii) Model the impact of Wolbachia on DENV epidemiological profile in the upcoming years in the specific context of NC. Based on the analysis of over 250 DENV samples, the novelty of the DenWOlution project relies on its extensive spatio-temporal characterization of DENV evolution. This will allow us to monitor in real time any adaptive process in response to the Wolbachia strategy. With a combination of in vitro, in vivo and modelling studies, DenWOlution will improve our understanding of DENV evolution and dengue epidemiological dynamics in the population. Furthermore, as many places are implementing the Wolbachia strategy, it is of importance to anticipate the consequences of the interactions between and the reciprocal impact of DENV evolution and Wolbachia intervention. Results arising from this project will inform not only the applications and limitations of the Wolbachia strategy but also any strategy aiming at controlling DENV transmission. DenWOlution will allow us to anticipate the development of future strategies for the control of Ae. aegypti-borne viruses.

Leptospirosis is a severe bacterial disease with highest impact in the Tropics. Recent data show a growing incidence in Europe (France, Belgium, Croatia, the Netherlands). Leptospirosis affects 1 million humans yearly, killing 58,900, but remains neglected and attracts insufficient attention. One century ago, Noguchi outlined its epidemiology and pointed the role of the survival of leptospires “in nature”. Leptospires chronically colonize the kidneys of mammals and are shed in the environment, where humans get infected. Animal-environment-human interactions determine patterns of disease; thus understanding the ecology of leptospires in ecosystems is critical. Yet, leptospirosis has mostly been studied as a zoonosis; environmental determinants of transmission have not been an active field of research. Early work identified conditions for Leptospira survival; however, recent work show that assumptions need be revisited. It is assumed that pathogens only survive in soil or freshwater; yet no resistance form was ever evidenced. The ability of the environment to support the survival of leptospires is a cornerstone of leptospirosis epidemiology. SpIRAL aims at filling the gaps in knowledge of Leptospira habitat outside a host. SpIRAL goals are to (1) identify the environmental abiotic factors that impact Leptospira survival in soils and freshwater, (2) characterize the microbiota that shelter Leptospira in the environment (3) model the dynamics of Leptospira dispersion upon rainfall and (4) generate a spatial map of leptospirosis risk integrating environmental, ecological and climatic parameters. This holistic approach of the environmental component of leptospirosis will yield new knowledge and avenues for a better control of the disease, also making the case for other environment-borne infections. SpIRAL will take benefit of the expertise developed in New Caledonia in the fields of leptospirosis and soil sciences. A full knowledge of Leptospira environmental habitats will be acquired, requiring a substantial amount of information on the ecosystems allowing or oppositely impairing their viability. First a collection of georeferenced soils and sediments will be collected and characterized (physical and chemical soil analysis, presence of virulent leptospires in situ, prokaryotic and eukaryotic microbiota). Their ability to support the survival of Leptospira will be assessed in vitro using microcosms. The interaction of pathogenic leptospires with soil particles, with Free-Living Ameoba or in natural biofilms will also be studied, providing further insight into their environmental lifestyle. Taking benefit of a site fully equipped for hydrology, we will also study and model the dispersion of Leptospira during rainfalls, known triggers of leptospirosis outbreaks. The model will be established in the pilot watershed then evaluated in other areas of high incidence. The information gained on Leptospira dynamics in water under the influence of rain will prove for prevention. Data of SpIRAL together with known leptospirosis risk factors will be analyzed spatially to establish and evaluate a spatial map of disease risk. This model will be used to study the relative weights of risk factors and to translate research findings into health benefits. SpIRAL aims to provide a comprehensive understanding of the ecosystem in the persistence of- and dynamics of exposure to- leptospirosis. It will address knowledge gaps on basic aspects of Leptospira lifestyle outside a host, key determinants of human disease, and will provide an integrated, data-rich and comprehensive and generalizable picture of Leptospira environmental habitat. Shifting the paradigm of leptospirosis epidemiology from a zoonosis to an environment-borne infection, SpIRAL aims to better understand epidemiology and infer risk management strategies for a better control of the disease.

Context and objectives. Currently, 700,000 deaths are yearly attributed to antimicrobial resistance (AMR) in the world and this number is estimated to increase to 10 million by 2050. Indeed, the widespread use of antibiotics has led to the emergence of ‘superbugs’ such as Methicillin-resistant Staphylococcus aureus (MRSA) difficult to treat with existing medicines. This fosters the discovery of new efficient antibiotic treatments against severe human infectious diseases and related sepsis that is still associated with dramatic mortality rate. Immune-mediated inflammatory diseases (IMIDs) also represent a major global health issue with an incidence in Western society that approximates 5–7%. Cytokines are critical inflammatory mediators produced to trigger the host immune response during infections and are also major drivers of inflammatory response in IMIDs pathogenesis. Recent drug development focused on the regulation of inflammatory cytokines or on the inhibition of the Janus kinases (JAKs)/signal transducer and activator of transcription proteins (STATs) signaling pathways or Jakinibs approved for treatment of IMIDs. However, considering refractory patients and opportunistic diseases related to immunosuppressive mechanisms, drug developments are undergoing and focus on new molecules inhibiting cytokines or JAK-STAT signaling pathways. Marine microalgaes and bacteria produce anti-inflammatory and antimicrobial molecules of high pharmacological value. Bioprospecting campaigns in New Caledonia led to the characterization of microalgaes and marine bacteria producing bioactive molecules for blue biotechnology applications. We hypothesize novel bioactive marine natural products (MNPs) to be discovered from New Caledonian marine biodiversity and will characterize antibacterial and immunomodulatory MNPs from New Caledonian marine microalgaes and bacteria available from the collections of the IFREMER/ADECAL Technopole and the private start-up BIOTECAL. Brief methodological description. We will study effects of MNPs on drug resistant bacteria and immunomodulatory effects of host immune response during inflammatory phase. More specifically, microalgae extracts (MAEs) and marine bacteria exopolysaccharides (EPSs) will be tested towards drug-resistant bacterial strains isolated from the environment, from the territorial hospital center (CHT-NC) and from local patients, including Methicillin-resistant Staphylococcus aureus (MRSA), Ceftazidime-resistant Pseudomonas aeruginosa (CRPA), Vancomycin-resistant Enterococcus faecium (VRE) and Carbapenem-resistant Enterobacteriaceae (CRE). Antimicrobial activity of the MNPs will be determined by agars diffusion and microdilution methods. We will use in vitro models of induced human (PMA-treated THP-1 monocyte) and murine (RAW264.7 cells) macrophages to evaluate the potential regulation of major inflammatory cytokines using ELISA and RT-qPCR techniques. Inhibition of JAK-STAT signaling pathways will also be investigated using Western Blot and TransAM assays. Expected impacts of the project. The project CHARM will investigate complementary bioactivities to identify innovative molecules to be proposed as platform molecules for pharmaceuticals in the field of antibacterial and immunomodulatory sectors, and results will be useful to improve the value-added chain in the field of MNPs and blue technology in New Caledonia. Thus, this project answers the need for a sustainable exploitation of marine bioresources and therefore contributes to the National Strategy for the Bioeconomy. It also contributes to the valorization of the biodiversity of the French Overseas and respond to the specification of the “Livre Bleu Outre-Mer” validated by the Ministry of Overseas. Long-term applications are expected in the sector of pharmaceutical industry with partnership with the private sector.