Cross-talk and mutual shaping between the immune system and the microbiota during an oyster's life.

The Pacific oyster lives in microbe-rich marine coastal systems subjected to rapid environmental changes. It harbours a diversified and fluctuating microbiota that cohabits with immune cells expressing a diversified immune gene repertoire. In the early stages of oyster development, just after fertilization, the microbiota plays a key role in educating the immune system.

Resistance of scallop larvae to vibriosis is associated with the front-loading of immune genes and enhanced antimicrobial response.

Mass mortality events caused by vibriosis have emerged in hatchery-reared scallop larvae from Chile, threatening scallop aquaculture. In an attempt to mitigate this emerging infectious disease and provide candidates for marker-assisted selective breeding, we tested here the existence of a genetic component of scallop resistance to the pathogen Through a dual RNA-seq approach we analyzed the basal transcriptome and the transcriptional response to infection in two resistant and two susceptible families as well as the pathogen transcriptomic response to host colonization. The results highlighted a genetic basis in the resistance of scallop larvae to the pathogen.

Functional Diversification of Oyster Big Defensins Generates Antimicrobial Specificity and Synergy against Members of the Microbiota.

Big defensins are two-domain antimicrobial peptides (AMPs) that have highly diversified in mollusks. -BigDefs are expressed by immune cells in the oyster , and their expression is dampened during the Pacific Oyster Mortality Syndrome (POMS), which evolves toward fatal bacteremia. We evaluated whether -BigDefs contribute to the control of oyster-associated microbial communities.

On the need for integrating cancer into the One Health perspective.

Recent pandemics have highlighted the urgency to connect disciplines studying animal, human, and environment health, that is, the "One Health" concept. The One Health approach takes a holistic view of health, but it has largely focused on zoonotic diseases while not addressing oncogenic processes. We argue that cancers should be an additional key focus in the One Health approach based on three factors that add to the well-documented impact of humans on the natural environment and its implications on cancer emergence.

Getting out of crises: Environmental, social-ecological and evolutionary research is needed to avoid future risks of pandemics.

The implementation of One Health/EcoHealth/Planetary Health approaches has been identified as key (i) to address the strong interconnections between risk for pandemics, climate change and biodiversity loss and (ii) to develop and implement solutions to these interlinked crises. As a response to the multiple calls from scientists on that subject, we have here proposed seven long-term research questions regarding COVID-19 and emerging infectious diseases (EIDs) that are based on effective integration of environmental, ecological, evolutionary, and social sciences to better anticipate and mitigate EIDs. Research needs cover the social ecology of infectious disease agents, their evolution, the determinants of susceptibility of humans and animals to infections, and the human and ecological factors accelerating infectious disease emergence.

The Pacific Oyster Mortality Syndrome, a Polymicrobial and Multifactorial Disease: State of Knowledge and Future Directions.

The Pacific oyster () has been introduced from Asia to numerous countries around the world during the 20th century. is the main oyster species farmed worldwide and represents more than 98% of oyster production. The severity of disease outbreaks that affect , which primarily impact juvenile oysters, has increased dramatically since 2008.

Alterins Produced by Oyster-Associated Are Antibacterial Cyclolipopeptides with LPS-Binding Activity.

Discovery after discovery, host-associated microbiota reveal a growing list of positive effects on host homeostasis by contributing to host nutrition, improving hosts' immune systems and protecting hosts against pathogens. In that context, a collection of oyster associated bacteria producing antibacterial compounds have been established to evaluate their role in non-host-derived immunity. Here, we described alterins; potent anti-Gram negative compounds produced by h-6 and h-42 isolated from different healthy oyster hemolymph.

Functional Insights From the Evolutionary Diversification of Big Defensins.

Big defensins are antimicrobial polypeptides believed to be the ancestors of β-defensins, the most evolutionary conserved family of host defense peptides (HDPs) in vertebrates. Nevertheless, big defensins underwent several independent gene loss events during animal evolution, being only retained in a limited number of phylogenetically distant invertebrates. Here, we explore the evolutionary history of this fascinating HDP family and investigate its patchy distribution in extant metazoans.

Vibrio-bivalve interactions in health and disease.

In the marine environment, bivalve mollusks constitute habitats for bacteria of the Vibrionaceae family. Vibrios belong to the microbiota of healthy oysters and mussels, which have the ability to concentrate bacteria in their tissues and body fluids, including the hemolymph. Remarkably, these important aquaculture species respond differently to infectious diseases.

Vibrio splendidus O-antigen structure: a trade-off between virulence to oysters and resistance to grazers.

A major debate in evolutionary biology is whether virulence is maintained as an adaptive trait and/or evolves to non-virulence. In the environment, virulence traits of non-obligatory parasites are subjected to diverse selective pressures and trade-offs. Here, we focus on a population of Vibrio splendidus that displays moderate virulence for oysters.

A Sustained Immune Response Supports Long-Term Antiviral Immune Priming in the Pacific Oyster, Crassostrea gigas.

Over the last decade, innate immune priming has been evidenced in many invertebrate phyla. If mechanistic models have been proposed, molecular studies aiming to substantiate these models have remained scarce. We reveal here the transcriptional signature associated with immune priming in the oyster Oysters were fully protected against Ostreid herpesvirus 1 (OsHV-1), a major oyster pathogen, after priming with poly(I·C), which mimics viral double-stranded RNA.

The Ancestral N-Terminal Domain of Big Defensins Drives Bacterially Triggered Assembly into Antimicrobial Nanonets.

Big defensins, ancestors of β-defensins, are composed of a β-defensin-like C-terminal domain and a globular hydrophobic ancestral N-terminal domain. This unique structure is found in a limited number of phylogenetically distant species, including mollusks, ancestral chelicerates, and early-branching cephalochordates, mostly living in marine environments. One puzzling evolutionary issue concerns the advantage for these species of having maintained a hydrophobic domain lost during evolution toward β-defensins.

Resistance of the oyster pathogen Vibrio tasmaniensis LGP32 against grazing by Vannella sp. marine amoeba involves Vsm and CopA virulence factors.

Vibrios are ubiquitous in marine environments and opportunistically colonize a broad range of hosts. Strains of Vibrio tasmaniensis present in oyster farms can thrive in oysters during juvenile mortality events and behave as facultative intracellular pathogen of oyster haemocytes. Herein, we wondered whether V.

Species-specific mechanisms of cytotoxicity toward immune cells determine the successful outcome of infections.

species cause infectious diseases in humans and animals, but they can also live as commensals within their host tissues. How subverts the host defenses to mount a successful infection remains poorly understood, and this knowledge is critical for predicting and managing disease. Here, we have investigated the cellular and molecular mechanisms underpinning infection and colonization of 2 virulent species in an ecologically relevant host model, oyster, to study interactions with marine species.

Gene Duplication Drives the Evolution of Redundant Regulatory Pathways Controlling Expression of the Major Toxic Secreted Metalloproteases in LGP32.

CsrBs are bacterial highly conserved and multiple-copy noncoding small RNAs (sRNAs) that play major roles in cell physiology and virulence. In the genus, they are known to be regulated by the two-component system VarS/VarA. They modulate the well-characterized quorum sensing pathway controlling virulence and luminescence in and , respectively.

Oyster Farming, Temperature, and Plankton Influence the Dynamics of Pathogenic Vibrios in the Thau Lagoon.

species have been associated with recurrent mass mortalities of juvenile oysters threatening oyster farming worldwide. However, knowledge of the ecology of pathogens in affected oyster farming areas remains scarce. Specifically, there are no data regarding (i) the environmental reservoirs of populations pathogenic to oysters, (ii) the environmental factors favoring their transmission, and (iii) the influence of oyster farming on the persistence of those pathogens.

Massive Gene Expansion and Sequence Diversification Is Associated with Diverse Tissue Distribution, Regulation and Antimicrobial Properties of Anti-Lipopolysaccharide Factors in Shrimp.

Anti-lipopolysaccharide factors (ALFs) are antimicrobial peptides with a central β-hairpin structure able to bind to microbial components. Mining sequence databases for ALFs allowed us to show the remarkable diversity of ALF sequences in shrimp. We found at least seven members of the ALF family (Groups A to G), including two novel Groups (F and G), all of which are encoded by different loci with conserved gene organization.

Inefficient immune response is associated with microbial permissiveness in juvenile oysters affected by mass mortalities on field.

Since 2008, juvenile Crassostrea gigas oysters have suffered from massive mortalities in European farming areas. This disease of complex etiology is still incompletely understood. Triggered by an elevated seawater temperature, it has been associated to infections by a herpes virus named OsHV-1 as well as pathogenic vibrios of the Splendidus clade.

The One Health Concept: 10 Years Old and a Long Road Ahead.

Over the past decade, a significant increase in the circulation of infectious agents was observed. With the spread and emergence of epizootics, zoonoses, and epidemics, the risks of pandemics became more and more critical. Human and animal health has also been threatened by antimicrobial resistance, environmental pollution, and the development of multifactorial and chronic diseases.