Protozoaires et moisissures : décryptage des mécanismes moléculaires qui détournent la machinerie cellulaire de l'hôte

The co-evolution of pathogens and their target hosts has led to the establishment of close and complex interactions between them. From protozoa to moulds, the interactions set up during host colonisation allow the parasite to escape or even to control the host to divert its resources, which can lead to cell exhaustion and programmed cell death for the benefit of the parasite.Throughout my scientific career, I have been lucky enough to be part of several research teams interested, as I was, in understanding the ability of parasites to manipulate the biology of their host cell and the danger signals it triggers. Thus, during my master's and doctoral studies, and my postdoctoral position, I studied intracellular protozoa such as Neospora caninum and Plasmodium sp. After my recruitment as associate professor at the EnvA, I wanted to apply the knowledge acquired in the understanding of the cellular interaction between the mould Aspergillus fumigatus and the cells responsible for the first line of lung defence.While Neospora is responsible for the severe economic losses associated with abortion in cattle, Plasmodium infection continues to have devastating consequences for the health and livelihoods of people around the world. The intracellular nature of these two parasites is an example of their ability to camouflage themselves from host defence mechanisms at the cellular and immune level.In the first part of this paper, I show the importance of regulating the expression of parasitic surface proteins and those produced by secretory vesicles during the invasion and transformation within the host cell, such as SAG1 and BSR4 in Neospora, or PLP1 and RON4 in Plasmodium.The characterisation and manipulation of the genes expressing these proteins has allowed the development of strategies for the early diagnosis and/or prevention of infection.While host cell manipulation is an expected mechanism in intracellular protists, this ability is not well known in other eukaryotes such as the mould Aspergillus fumigatus. This opportunistic fungus is capable of causing various forms of mycosis in humans and animals. Thus, aspergillosis can be responsible for disabling and even fatal respiratory disorders and serious economic losses in the poultry sector.In the second part of this paper, I explain how the outcome of aspergillosis infection depends on early innate response mechanisms activated in two avian hosts by molecular patterns associated with the surface of A. fumigatus. The stimulation of the pro-inflammatory response, but also the production of certain immunoglobulins appears to be essential to ensure colonisation of the respiratory parenchyma to the detriment of its function in the affected birds, with varying degrees of success depending on the affected avian species.Finally, in the research team that I have just joined within the UMR-BIPAR (ANSES, EnvA, INRAe), I will continue with this co-evolutionary approach, but this time by exploring the more complex interaction between a protozoan (Babesia) and its vector (Ixodidae tick). I will take advantage of the cutting-edge tools and techniques developed by my team to analyse their cellular interactions and propose means of controlling and preventing piroplasmosis, a scourge for animal health and a growing public health concern worldwide

Aspergillosis in Wild Birds

The ubiquitous fungi belonging to the genus Aspergillus are able to proliferate in a large number of environments on organic substrates. The spores of these opportunistic pathogens, when inhaled, can cause serious and often fatal infections in a wide variety of captive and free-roaming wild birds. The relative importance of innate immunity and the level of exposure in the development of the disease can vary considerably between avian species and epidemiological situations. Given the low efficacy of therapeutic treatments, it is essential that breeders or avian practitioners know the conditions that favor the emergence of Aspergillosis in order to put adequate preventive measures in place

Phase hépatique du paludisme : voies d’entrée des sporozoïtes de Plasmodium

Les sporozoïtes de Plasmodium sont transmis par des moustiques du genre Anopheles, migrent jusqu’au foie et infectent les hépatocytes de l’hôte, où les parasites se multiplient et se différencient avant d’infecter les globules rouges : il s’agit de la phase pré-érythrocytaire de l’infection, asymptomatique et obligatoire. L’invasion des hépatocytes constitue une cible idéale pour des approches anti-paludiques prophylactiques, mais les mécanismes impliqués dans cette étape restent mal connus. Les parasites du phylum Apicomplexa infectent leurs cellules cibles à travers une structure spécifique, appelée jonction, pour former une vacuole parasitophore, essentielle au développement du parasite. La tétraspanine CD81, l’un des récepteurs du virus de l’hépatite C, joue un rôle crucial lors de l’infection du foie par les sporozoïtes de Plasmodium. CD81 intervient à la phase précoce de l’infection, probablement au niveau de l’entrée du sporozoïte. Le rôle précis de CD81 au cours de l’infection reste à définir, mais l’hypothèse actuelle est que CD81 intervient indirectement, en régulant l’activité d’un ou plusieurs autres facteurs essentiels, d’origine hépatocytaire ou parasitaire, au sein de microdomaines membranaires enrichis en tétraspanines

Phase hépatique du paludisme : voies d’entrée des sporozoïtes de Plasmodium

Les sporozoïtes de Plasmodium sont transmis par des moustiques du genre Anopheles, migrent jusqu’au foie et infectent les hépatocytes de l’hôte, où les parasites se multiplient et se différencient avant d’infecter les globules rouges : il s’agit de la phase pré-érythrocytaire de l’infection, asymptomatique et obligatoire. L’invasion des hépatocytes constitue une cible idéale pour des approches anti-paludiques prophylactiques, mais les mécanismes impliqués dans cette étape restent mal connus. Les parasites du phylum Apicomplexa infectent leurs cellules cibles à travers une structure spécifique, appelée jonction, pour former une vacuole parasitophore, essentielle au développement du parasite. La tétraspanine CD81, l’un des récepteurs du virus de l’hépatite C, joue un rôle crucial lors de l’infection du foie par les sporozoïtes de Plasmodium. CD81 intervient à la phase précoce de l’infection, probablement au niveau de l’entrée du sporozoïte. Le rôle précis de CD81 au cours de l’infection reste à définir, mais l’hypothèse actuelle est que CD81 intervient indirectement, en régulant l’activité d’un ou plusieurs autres facteurs essentiels, d’origine hépatocytaire ou parasitaire, au sein de microdomaines membranaires enrichis en tétraspanines

Detection and Control of Dermatophytosis in Wild European Hedgehogs (Erinaceus europaeus) Admitted to a French Wildlife Rehabilitation Centre

The rising number of European hedgehogs (Erinaceus europaeus) admitted every year to wildlife rehabilitation centres might be a source of concern to animal and public health since transmissible diseases, such as dermatophytosis, can be easily disseminated. This study seeks to evaluate the frequency of dermatophyte detection in hedgehogs admitted to a wildlife rehabilitation centre located near Paris, France, and to assess the risk of contamination in the centre in order to adapt prevention measures. A longitudinal cohort study was performed on 412 hedgehogs hosted at the Wildlife Animal Hospital of the Veterinary College of Alfort from January to December 2016. Animals were sampled once a month for fungal culture. Dermatophyte colonies were obtained from 174 out of 686 skin samples (25.4%). Besides Trichophyton erinacei, Trichophyton mentagrophytes and Nannizzia gypsea were also found. Dermatophyte detection seemed to be associated with the presence of skin lesions, while more than one-third of T. erinacei-positive animals were asymptomatic carriers. Healing required several months of treatment with topical and systemic azoles, but dermatophytosis did not seem to reduce the probability of release. Daily disinfection procedures and early detection and treatment of infected and asymptomatic carriers succeeded in limiting dermatophyte transmission between hedgehogs and humans

Cellular and molecular insights on the regulation of innate immune responses to experimental aspergillosis in chicken and turkey poults

International audienceAcross the world, many commercial poultry flocks and captive birds are threatened by infection with Aspergillus fumigatus. Susceptibility to aspergillosis varies among birds; among galliform birds specifically, morbidity and mortality rates seem to be greater in turkeys than in chickens. Little is known regarding the features of avian immune responses after inhalation of Aspergillus conidia, and to date, scarce information on inflammatory responses during aspergillosis exists. Thus, in the present study, we aimed to improve our understanding of the interactions between A. fumigatus and economically relevant galliform birds in terms of local innate immune responses. Intra-tracheal aerosolization of A. fumigatus conidia in turkey and chicken poults led to more severe clinical signs and lung lesions in turkeys, but leukocyte recovery from lung lavages was higher in chickens at 1dpi only. Interestingly, only chicken CD8+ T lymphocyte proportions increased after infection. Furthermore, the lungs of infected chickens showed an early upregulation of pro-inflammatory cytokines, including IL-1β, IFN-γ and IL-6, whereas in turkeys, most of these cytokines showed a downregulation or a delayed upregulation. These results confirmed the importance of an early pro-inflammatory response to ensure the development of an appropriate anti-fungal immunity to avoid Aspergillus dissemination in the respiratory tract. In conclusion, we show for the first time that differences in local innate immune responses between chickens and turkeys during aspergillosis may determine the outcome of the disease

Toxocara cati and Toxoplasma gondii in French Birds of Prey

International audienceParasites have developed many strategies to ensure their development, multiplication, and dissemination, including the use of reservoir hosts that are often nondomesticated species. Despite drastic reductions in their populations, wild birds remain widespread worldwide and could constitute some of these reservoirs. We focused on the identification of wild bird species harboring parasite stages in their muscles. Breast muscles of 327 birds of 27 different species were collected at three different sites in France. After artificial digestion, isolated nematode larvae were identified by PCR sequencing or restriction fragment length polymorphism (PCR-RFLP). Toxocara cati was identified mainly in birds of prey. The presence of anti-Toxoplasma antibodies was investigated by modified agglutination test on muscle fluids. Anti-Toxoplasma antibodies were detected in 65 out of 166 samples from various bird species. Avifauna, particularly birds of prey, could help on the surveillance of parasite circulation and play a role as sentinel species

Toxocara cati and Toxoplasma gondii in French Birds of Prey

International audienceParasites have developed many strategies to ensure their development, multiplication, and dissemination, including the use of reservoir hosts that are often nondomesticated species. Despite drastic reductions in their populations, wild birds remain widespread worldwide and could constitute some of these reservoirs. We focused on the identification of wild bird species harboring parasite stages in their muscles. Breast muscles of 327 birds of 27 different species were collected at three different sites in France. After artificial digestion, isolated nematode larvae were identified by PCR sequencing or restriction fragment length polymorphism (PCR-RFLP). Toxocara cati was identified mainly in birds of prey. The presence of anti-Toxoplasma antibodies was investigated by modified agglutination test on muscle fluids. Anti-Toxoplasma antibodies were detected in 65 out of 166 samples from various bird species. Avifauna, particularly birds of prey, could help on the surveillance of parasite circulation and play a role as sentinel species

Malaria Sporozoites Traverse Host Cells within Transient Vacuoles

International audiencePlasmodium sporozoites are deposited in the host skin by Anopheles mosquitoes. The parasites migrate from the dermis to the liver, where they invade hepatocytes through a moving junction (MJ) to form a replicative parasitophorous vacuole (PV). Malaria sporozoites need to traverse cells during progression through host tissues, a process requiring parasite perforin-like protein 1 (PLP1). We find that sporozoites traverse cells inside transient vacuoles that precede PV formation. Sporozoites initially invade cells inside transient vacuoles by an active MJ-independent process that does not require vacuole membrane remodeling or release of parasite secretory organelles typically involved in invasion. Sporozoites use pH sensing and PLP1 to exit these vacuoles and avoid degradation by host lysosomes. Next, parasites enter the MJ-dependent PV, which has a different membrane composition, precluding lysosome fusion. The malaria parasite has thus evolved different strategies to evade host cell defense and establish an intracellular niche for replication

A rapid and robust selection procedure for generating drug-selectable marker-free recombinant malaria parasites

International audienceExperimental genetics have been widely used to explore the biology of the malaria parasites. The rodent parasites Plasmodium berghei and less frequently P. yoelii are commonly utilised, as their complete life cycle can be reproduced in the laboratory and because they are genetically tractable via homologous recombination. However, due to the limited number of drug-selectable markers, multiple modifications of the parasite genome are difficult to achieve and require large numbers of mice. Here we describe a novel strategy that combines positive-negative drug selection and flow cytometry-assisted sorting of fluorescent parasites for the rapid generation of drug-selectable marker-free P. berghei and P. yoelii mutant parasites expressing a GFP or a GFP-luciferase cassette, using minimal numbers of mice. We further illustrate how this new strategy facilitates phenotypic analysis of genetically modified parasites by fluorescence and bioluminescence imaging of P. berghei mutants arrested during liver stage development