During meiosis, DNA double-strand breaks initiates homologous recombination at specific loci called hotspots. In many mammals, their localization corresponds to specific DNA sequences bound by the zinc finger (ZnF) array of PRDM9. A remarkable property of PRDM9 is the high diversity and fast evolution of its ZnF domain. The consequence is the fast evolution of recombination map for species having a PRDM9 for hotspot localisation, and thus higher adaptive potential. PRDM9 appears in the last common ancestor of metazoans but its partial or complete loss have been surprisingly reported in many taxa. Species lacking a full-length PRDM9 have evolutionary stable hotspots that are located near promoter-like regions, that are evicted by PRDM9. The involvement of PRDM9 in meiotic recombination has not been yet explored outside vertebrate species, one reason being that invertebrate model species have no PRDM9. Here, we propose to fill these gaps by investigating PRDM9 function in meiotic recombination in four closely-related species of freshwater snails for which we recently identified full-length PRDM9 conservation by exploring their recently published genome assemblies. The MeioSnail project will address the following questions: Where are meiotic hotspots located along the genome? Is PRDM9 essential for meiotic progress and fertility? Can we find evidence of PRDM9 function in the localisation of hotspots? We will use complementary approaches such as population genomics, genotyping of PRDM9 zinc finger array, molecular mapping, histology and genetic manipulation of snail. We will take advantage of the unique collection of biological material, as well as the molecular methods and tools developed and mastered for one snail species in the laboratory hosting the project. Providing the first exploration of PRDM9 role outside vertebrates will help to understand if this mechanism controlling the distribution of meiotic recombination is conserved across the tree of life.

To meet the demographic pressure, the livestock industry must intensify production while striving for sustainable management. With the emergence and re-emergence of infectious diseases, improving animal health and welfare is a key aspect of this challenge. Among the most prevalent pathogens is a group of atypical bacteria belonging to the genus Mycoplasma. While antibiotic treatments are facing an alarming rate of resistance, vaccines are only available for a very limited number of species and often provide insufficient protection. The RAMbo-V project intends to build on advances in bacterial genome engineering to pave the way for the development of synthetic vaccines against Mycoplasma bovis, a livestock pathogen associated with emerging episodes worldwide. This will be done by adapting and improving genetic tools recently developed in other mycoplasma species and using a high-throughput strategy for large-scale mapping of highly conserved antibody epitopes in the M. bovis pan-proteome. To engineer an avirulent vaccine chassis and secure its genetic stability, virulence factors non-essential for laboratory growth will be deleted from the M. bovis genome together with mobile genetic elements and chromosomal regions contributing to horizontal gene flows. Finally, the surface of M. bovis will be redesigned to allow optimal expression of selected epitopes through the use of a transmembrane carrier and the locking of surface variation mechanisms. By exploring an innovative vaccine strategy, RAMbo-V will have a positive impact on animal production and its dependence on antimicrobials. RAMbo-V will thus contribute to the development of sustainable food systems that manage demographic pressure with environmental, societal, and ethical challenges.

In all countries, women are less affected than men by severe forms of COVID-19 at all ages. It has been proposed that the gender bias in the severity of COVID-19 may be linked to a biological effect of sex resulting in a relative deficiency of innate antiviral immunity in men compared to women. As the sex bias is seen in people >50 years-old and persists in aged people, sex hormone effects in female are unlikely to explain these differences. We hypothesize that gene dosage effects due to X-chromosome inactivation (XCI) escape could possibly contribute to the sex differences in COVID-19. We have shown that TLR7 encoded by the X chromosome escapes XCI in the immune cells of women, and that the TLR7 protein is expressed at a higher level in women even after menopause. Since TLR7 is the Toll receptor involved in the innate and adaptive immune response against single-stranded RNA viruses, we hypothesized that this mechanism could account for the best innate immune responses to RNA viruses observed in women. In this proposal, we will test the role of the escape from XCI of Tlr7 in the production of type I interferons and in the vaccine response to SARS-CoV2 in mice. We will also assess whether there is a gender bias in the functional response of human plasmacytoid dendritic cells (pDCs) in response to SARS-CoV2. This project will provide new fundamental and conceptual knowledge on the nature of the immune mechanism underlying the female predominance in the innate and adaptive immunity induced by Tlr7 in response to SARS-CoV2. These results could open avenues for the development of new vaccine strategies against the COVID-19 pandemic and make it possible to adapt certain therapeutic strategies according to sex for personalized medicine.

Type I interferons are the main antiviral cytokines. They stimulate the expression of antiviral effectors and regulate the activation of various immune cells. However, type I interferons may not always be beneficial during a viral infection, as they can cause an excessive inflammation leading to immunopathology. In the case of COVID-19, the balance between the beneficial and the detrimental effects of type I interferons could be very precarious. Experimental studies in SARS-CoV-1 infected mice and clinical investigations in COVID-19 patients indicate that an early type I interferon response could be beneficial, while a delayed type I interferon response could be detrimental to the host. Thus, the timing of the type I interferon production could be a critical determinant of the pathophysiology of SARS-CoV-2 infection. The aim of the TIMING project is to test this hypothesis in an animal model of SARS-CoV-2 infection. We will administer type I interferon at various time points post-infection and investigate how the timing of the type I interferon response modulates the clinical course of infection. By combining virological analyses with profiling of the immune response, our project will lead to a better understanding of the pathophysiology of COVID-19 and may lead to the identification of biological markers that correlate with type I interferon therapeutic efficacy.

Understanding the factors that influence parasite transmission is of central interest to both the public health and evolutionary biology research community. The central aim of this proposal is to identify the genetic, epigenetic and transcriptomic basics of the timing of cercarial shedding pattern in Schistosoma mansoni, a parasitic fluke that infects 67 million people in South America, Middle-East and Africa. This approach is both ambitious and innovative in the field of parasitology; it will focus on the cercarial shedding of the parasite which constitutes the most important life-trait for schistosome transmission to humans. Our project will be the first using the multifaceted contribution of the three "omics", genomics, epigenomics and transcriptomics, in order to analyze the basics of the timing of cercarial shedding in schistosomes, the agents of the second most important parasitic disease in the world after malaria in terms of public health and economic impact. The life cycle of schistosomes includes a snail host in which schistosome larvae multiplicate clonally and hundreds to thousands of motile cercariae larvae are released into the water where they infect humans or rodents. The timing of cercarial release from the snail varies among populations and overlaps with the activity patterns of their vertebrate hosts. Most S. mansoni populations that primarily infect humans shed cercariae larvae in late morning, while parasite populations that primarily infect rodents shed cercariae in late afternoon or night. Schistosome parasites are unusual among parasites of humans because they are gonochoric, so genetic crosses can be staged, and the complete lifecycle can be easily maintained in the laboratory. The complete genome sequence and the growing molecular tool kit now allows genomic, epigenomic and functional characterizations. Our project is developed according to three aims. Aim 1 will use linkage mapping to identify the genome regions and candidate genes underlying cercarial shedding rhythms. We have already completed the cross between nocturnally and diurnally shedding parasites from Oman and identified a genome region on chr. 1 that determines this trait. Field missions will permit to collect natural samples of diurnal/nocturnal shedding chronotypes in order to validate our experimental results. Aim 2 will use epigenomic tools to identify the genome regions and candidate genes all along the circadian rhythm of cercarial shedding. We have already found a difference between acetylation for two histone H3 amino acid positions, H3K9 and H3K14 in 107 genomic regions for the nocturnally shedding Omanese strain between the hour of the shedding peak and a period with no shedding. Aim 3 will use RNAseq to examine rhythms in expression of nocturnal and diurnal shedding parasites from Oman across 12 hr light-12 hr dark cycles, to investigate the metabolic pathways underlying control of cercarial release. While this project aims to answer fundamental questions about parasite biology, there may also be implications for parasite control using interventions against S. mansoni in the snail host parasite. We note that targeted genetic interventions that aim to make vectors refractory to pathogen infection are a rapidly developing approach to control of mosquito borne diseases. Improved understanding of the pathways involved in cercarial release and the interactions between snail and parasite could make this approach feasible for disrupting schistosome transmission from the snail host. This project may have a high public health impact on the transmission control of schistosomiasis both in high and low endemic countries and even in countries where schistosomiasis is emergent, as recently shown by us in France (Corsica). This project fits very well in the "Vie, Santé, bien être" challenge of the ANR and SNR.