Emmanuel Guivier

Candidatus Neoehrlichia mikurensis in bank voles, France.

To further assess the geographic occurrence, possible vectors, and prevalence of Candidatus Neoehrlichia mikurensis, we analyzed spleen tissues from 276 voles trapped close to human settlements in France; 5 were infected with the organism. Sequencing showed the isolates carried the same genotype as the bacteria that caused disease in humans and animals elsewhere in Europe.

SESAME (SEquence Sorter & AMplicon Explorer)

Summary: Characterizing genetic diversity through genotyping short amplicons is central to evolutionary biology. Next-generation sequencing (NGS) technologies changed the scale at which these type of data are acquired. SESAME is a web application package that assists genotyping of multiplexed individuals for several markers based on NGS amplicon sequencing. It automatically assigns reads to loci and individuals, corrects reads if standard samples are available and provides an intuitive graphical user interface (GUI) for allele validation based on the sequences and associated decision-making tools. The aim of SESAME is to help allele identification among a large number of sequences. Availability: SESAME and its documentation are freely available under the Creative Commons Attribution-NonCommercial-ShareAlike 3.0 Unported Licence for Windows and Linux from http://www1.montpellier.inra.fr/CBGP/NGS/ or http://tinyurl.com/ngs-sesame. Contact: emese.meglecz@univ-provence.fr Supplementary information: Supplementary data are available at Bioinformatics online.

Helminth Interaction with the Host Immune System: Short-Term Benefits and Costs in Relation to the Infectious Environment

Chronic infections imply that the parasite and the host immune system closely interact for a long time without a fatal outcome. Environmental changes encountered by hosts and parasites, such as coinfections, can deeply affect the stability of this apparent equilibrium. Our study aimed to determine the effect of the infectious environment on the costs and benefits of chronic infection with the gut nematode Heligmosomoides polygyrus in mice. Heligmosomoides polygyrus is known for its capacity to actively interfere with the host immune response by secreting molecules that can dampen immunity. We simulated bacterial coinfection of H. polygyrus-infected CBA-strain mice during the chronic phase of the infection by injecting them with Escherichia coli lipopolysaccharide. We found that infection by H. polygyrus induced only weak costs for the host (in terms of reproductive investment) and was characterized by the upregulation of both Th1 (interferon-γ) and anti-inflammatory (transforming growth factor-β) cytokines, which is favorable to parasite persistence. However, when co-occurring with the simulated bacterial infection, H. polygyrus infection was associated with a pronounced shift toward a pro-inflammatory status, which was deleterious to both the parasite and the host. Our study highlights the dynamic equilibrium reached during chronic infection, where a rapid environmental change, such as a concomitant bacterial infection, can deeply affect the outcome of the host-parasite interaction.

APPORT DE L’IMMUNOGÉNÉTIQUE À LA COMPRÉHENSION DES INTERACTIONS ENTRE LE CAMPAGNOL ROUSSÂTRE MYODES GLAREOLUS ET L’HANTAVIRUS PUUMALA

Nephropathia epidemica (NE) is a mild form of hemorrhagic fever with renal syndrome (HFRS) caused by the hantavirus Puumala (PUUV). In Europe, its distribution is fragmented, whereas the bank vole Myodes glareolus, which is the reservoir of PUUV, is common all over the continent. Determining the causes underlying this heterogeneity is of main importance to better understand and prevent the risks of NE emergence. Besides climatic and ecological hypotheses, we have proposed that the geographic variability of bank vole immune responses to PUUV infection could shape differences in PUUV prevalence, and consequently NE incidence. We have tested this hypothesis by studying polymorphisms and / or expression levels of six candidate genes involved in the immune response to PUUV (DRB-MHC, TNF-alpha promoter, TLR4, TLR7, Mx2, Integrin beta3) on ten populations of bank voles sampled in the French Ardennes, along a North-South transect including PUUV endemic and non-endemic areas. Signatures of selection have been evidenced for TNF-alpha and Mx2 genes using population genetics (FST scan) and genotype - phenotype association approaches. These genes have antiviral properties but also induce immunological damages, what make them central for driving a balance of resistance / tolerance to PUUV. Bank voles vary in their basal ability to tolerate/resist to PUUV. In high PUUV prevalence areas, TNF-alpha and Mx2 expression seemed down-regulated what suggest selection or phenotypic plasticity for higher tolerance to PUUV, at the benefit of lower immunopathological costs. Some of these results have been confirmed at the European scale.

Microbiota Diversity Within and Between the Tissues of Two Wild Interbreeding Species

Understanding the role of microbiota as reproductive barriers or sources of adaptive novelty in the fundamental biological phenomenon of speciation is an exciting new challenge necessitating exploration of microbiota variation in wild interbreeding species. We focused on two interbreeding cyprinid species, Chondrostoma nasus and Parachondrostoma toxostoma, which have geographic distributions characterized by a mosaic of hybrid zones. We described microbiota diversity and composition in the three main teleost mucosal tissues, the skin, gills and gut, in the parental parapatric populations. We found that tissue type was the principal determinant of bacterial community composition. In particular, there was strong microbiota differentiation between external and internal tissues, with secondary discrimination between the two species. These findings suggest that specific environmental and genetic filters associated with each species have shaped the bacterial communities, potentially reflecting deterministic assemblages of bacteria. We defined the core microbiota common to both Chondrostoma species for each tissue, highlighting the occurrence of microbe-host genome interactions at this critical level for studies of the functional consequences of hybridization. Further investigations will explore to what extend these specific tissue-associated microbiota signatures could be profoundly altered in hybrids, with functional consequences for post-mating reproductive isolation in relation to environmental constraints.

Early life infection and host senescence

&NA; Advanced age is often associated with a chronic inflammatory status and inflammatory diseases. It has been suggested that exposure to infectious agents that stimulate the inflammatory response at early ages might have carry over effects in terms of accelerated senescence and increased mortality at late ages. However, not all pathogens and parasites have pro‐inflammatory effects. In particular, parasitic nematodes have been shown to dampen the inflammatory response and to prevent or alleviate the symptoms of inflammatory diseases. We, therefore, tentatively predicted that early infection with a parasite that has anti‐inflammatory properties might postpone aging. We tested this idea using the association between the nematode Heligmosomoides polygyrus and its rodent host. In addition to the infection with H. polygyrus, we also activated the systemic inflammatory response with an Escherichia coli LPS injection, to explore the effect of H. polygyrus under control and inflammatory conditions. In addition to lifespan, we also assessed several biomarkers of aging, once the infection had been cleared. We found that both treatments (H. polygyrus infection and LPS challenge) reduced longevity. Most of the biomarkers of aging were affected by the previous infection status, suggesting that mice exposed to the nematode had an accentuated senescent phenotype. These results show that infection with immunomodulatory parasites per se does not prolong host lifespan and rather support the view that infection in early life accelerates the rate of aging.

Early Plasmodium-induced inflammation does not accelerate aging in mice

Aging is associated with a decline of performance leading to reduced reproductive output and survival. While the antagonistic pleiotropy theory of aging has attracted considerable attention, the molecular/physiological functions underlying the early‐life benefits/late‐life costs paradigm remain elusive. We tested the hypothesis that while early activation of the inflammatory response confers benefits in terms of protection against infection, it also incurs costs in terms of reduced reproductive output at old age and shortened longevity. We infected mice with the malaria parasite Plasmodium yoelii and increased the inflammatory response using an anti‐IL‐10 receptor antibody treatment. We quantified the benefits and costs of the inflammatory response during the acute phase of the infection and at old age. In agreement with the antagonistic pleiotropy hypothesis, the inflammatory response provided an early‐life benefit, since infected mice that were treated with anti‐IL‐10 receptor antibodies had reduced parasite density and anemia. However, at old age, mice in all treatment groups had similar levels of C‐reactive protein, reproductive output, survival rate, and lifespan. Overall, our results do not support the hypothesis that the benefits of a robust response to malaria infection in early life incur longer term fitness costs.

Life history adjustments to intestinal inflammation in a gut nematode

ABSTRACT Many parasitic nematodes establish chronic infections. This implies a finely tuned interaction with the host immune response in order to avoid infection clearance. Although a number of immune interference mechanisms have been described in nematodes, how parasites adapt to the immune environment provided by their hosts remains largely unexplored. Here, we used the gastrointestinal nematode Heligmosomoides polygyrus to investigate the plasticity of life history traits and immunomodulatory mechanisms in response to intestinal inflammation. We adopted an experimental model of induced colitis and exposed worms to intestinal inflammation at two different developmental stages (larvae and adults). We found that H. polygyrus responded to intestinal inflammation by up-regulating the expression of a candidate gene involved in the interference with the host immune response. Worms infecting mice with colitis also had better infectivity (earlier adult emergence in the intestinal lumen and higher survival) compared with worms infecting control hosts, suggesting that H. polygyrus adjusted its life history schedule in response to intestinal inflammation. Summary: Phenotypic plasticity of life history traits in a nematode can be an effective mechanism to adapt to intestinal inflammation.