Thermostable Keystone bacteria maintain the functional diversity of the Ixodes scapularis microbiome under heat stress

Variations in the composition and diversity of tick microbiome due to high temperatures may influence the hierarchy of community members as a response to environmental change. Modifications in the community structure are hypothesized to drive alterations in the presence and/or abundance of functional pathways in the bacterial metagenome. In this study, this hypothesis was tested by using published 16S rRNA datasets of Ixodes scapularis males incubated at different temperatures (i.e., 4, 20, 30, and 37 degrees C) in a laboratory setting. Changes in community structure and functional profiles in response to temperature shifts were measured using co-occurrence networks and metagenome inference. Results from laboratory-reared ticks were then compared with those of field-collected ticks. The results from laboratory-reared ticks showed that high temperature altered the structure of the microbial community and decreased the number of keystone taxa. Notably, four taxa were identified as keystone in all the temperatures, and the functional diversity of the tick microbiome was contained in the four thermostable keystone their associated bacterial taxa. Three of the thermostable keystone taxa were also found in free-living ticks collected in Massachusetts. Moreover, the comparison of functional profiles of laboratory-reared and field-collected ticks revealed the existence of an important set of metabolic pathways that were common among the different datasets. Similar to the laboratory-reared ticks, the keystone taxa identified in field-collected ticks alongside their consortia (co-occurring taxa) were sufficient to retain the majority of the metabolic pathways in the functional profile. These results suggest that keystone taxa are essential in the stability and the functional resiliency of the tick microbiome under heat stress

Rapid evolution of a novel protective symbiont into keystone taxon in Caenorhabditis elegans microbiota

Protective microbes have a major role in shaping host–pathogen interactions, but their relative importance in the structure of the host microbiota remains unclear. Here, we used a network approach to characterize the impact of a novel, experimentally evolved ‘protective microbial symbiont’ (Enterococcus faecalis) on the structure and predicted function of the natural microbiota of the model organism Caenorhabditis elegans. We used microbial network analysis to identify keystone taxa and describe the hierarchical placement of protective and non-protective symbionts in the microbiota. We found that early colonization with symbionts produce statistically significant changes in the structure of the community. Notably, only the protective E. faecalis became a keystone taxon in the nematode microbiota. Non-protective lineages of the same bacterial species remained comparatively unimportant to the community. Prediction of functional profiles in bacterial communities using PICRUSt2 showed that the presence of highly protective E. faecalis decreased the abundance of ergothioneine (EGT) biosynthesis pathway involved in the synthesis of the antioxidant molecule EGT, a potential public good. These data show that in addition to direct antagonism with virulent pathogens, keystone protective symbionts are linked to modified bacterial community structure and possible reductions in public goods, potentially driving decreased antioxidant defense. We suggest that this response could suppress infection via wholesale microbial community changes to further benefit the host. These findings extend the concept of protective symbionts beyond bodyguards to ecosystem engineers

Decontamination protocols affect the internal microbiota of ticks

Studies on the microbiota of ticks have promoted hypotheses about the combined effects of the bacterial community, its functional contributions to the tick’s physiology or probable competition effects with some tick-borne pathogens. However, knowledge on the origin of the microbiota of newly hatched larvae is missing. This study aimed to elucidate the source(s) of the microbiota in unfed tick larvae, addressing the composition of the “core microbiota” and the best ways to decontaminate eggs for microbiota studies. We applied laboratory degree bleach washes and/or ultraviolet light treatments on engorged Rhipicephalus australis females and/or their eggs. No significant effects of these treatments on the reproductive parameters of females and the hatching rates of eggs were observed. However, the different treatments did show striking effects on the composition of the microbiota. The results indicated that bleach washes disrupted the internal tick microbiota in females, implying that bleach may have entered the tick and subsequently affected the microbiota. Furthermore, the analyses of results demonstrated that the ovary is a main source of tick microbiota, while the contribution of Gené’s organ (a part of the female reproductive system that secretes a protective wax coat onto tick eggs) or the male’s spermatophore requires further investigation. Further studies are needed to identify best practice protocols for the decontamination of ticks for microbiota studies

Constitutive and ghrelin-dependent GHSR1a activation impairs CaV2.1 and CaV2.2 currents in hypothalamic neurons

The growth hormone secretagogue receptor type 1a (GHSR1a) has the highest constitutive activity of any G protein coupled receptor (GPCR). GHSR1a mediates the action of the hormone ghrelin and, its activation increases transcriptional and electrical activity in hypothalamic neurons. It is known that GHSR1a is present at some specific GABAergic presynaptic terminals; however, its impact on neurotransmitter release remains elusive. The voltage gated calcium channels, CaV2.1 and CaV2.2, control neurotransmitter release at presynaptic terminals and their activities are modulated by many GPCRs. Here we show that constitutive as well as agonist-dependent GHSR1a activation trigger a strong impairment of both CaV2.1 and CaV2.2 currents in rat and mouse neurons and in a heterologous expression system. Constitutive GHSR1a activity reduces CaV2 currents by a Gi/o-dependent mechanism that involves persistent reduction in channel density at plasma membrane, whereas, ghrelin-dependent GHSR1a inhibition is reversible and involves altered CaV2 current gating via a Gq-dependent pathway. Thus, we show that GHSR1a differentially inhibits CaV2 channels by Gi/o- or Gq-protein pathways depending on its activation mode. Moreover, we present evidence suggesting that GHSR1a-mediated inhibition of CaV2 impairs GABA release in hypothalamic neurons, a mechanism that could contribute to neuronal activation by the disinhibition of postsynaptic neurons

Rôle fonctionnel des bactéries clés dans les interactions hôte-microbiote-pathogène : implications pour le contrôle des maladies à transmission vectorielle

Les agents pathogènes animaux et humains, principalement ceux transmis par les arthropodes qui se nourrissent de sang tels que les tiques et les moustiques, constituent un problème de santé publique mondial. Bien que plusieurs stratégies aient été développées et utilisées pour lutter contre les maladies à transmission vectorielle (MTV), la moitié de la population mondiale vit encore aujourd'hui à risque de MTV. Par conséquent, la recherche de nouvelles stratégies pour bloquer les MTV avec de meilleurs résultats est nécessaire. Plusieurs études soulignent le rôle central que joue le microbiome vectoriel sur la physiologie des vecteurs et la compétence vectorielle. La perturbation du microbiome du vecteur a été proposée comme moyen de contrôle des MTV. Dans la présente thèse, nous avons utilisé des réseaux microbiens pour étudier l'importance des bactéries clés dans le microbiote du vecteur et nous proposons des vaccins anti-microbiote comme outil de manipulation précise du microbiome du vecteur, avec des implications pour l'étude des interactions vecteur-microbiote et le contrôle des MTV. Les résultats obtenus ont montré que les taxons clés sont des membres bactériens importants et influents du microbiote du vecteur. Premièrement, nous avons démontré que les taxons clés ont un rôle important dans le maintien de la stabilité fonctionnelle du microbiome des tiques sous stress thermique. Deuxièmement, en ciblant les taxons clés du microbiote vecteur avec des anticorps de l'hôte, nous avons montré que les vaccins anti-microbiote diminuent la colonisation des agents pathogènes chez les tiques et les moustiques.Plus précisément, nous avons montré que le ciblage des taxons clés à l'aide d'un vaccin anti-microbiote diminue la connectivité des taxons clés dans le réseau microbien, ce qui a un impact écologique en cascade entraînant une modulation importante du profil taxonomique et fonctionnel du microbiote des tiques. Notamment, la perturbation du microbiome des tiques a réduit la colonisation de Borrelia afzelii, l'agent causal de la borréliose de Lyme en Europe, chez les tiques Ixodes ricinus. Ce résultat ne se limitait pas au vecteur tique puisque nous avons également démontré que la perturbation de microbiote des moustiques diminuait également le développement de Plasmodium relictum, l'agent causal du paludisme aviaire, dans son vecteur naturel Culex quinquefasciatus. Dans l'ensemble, ces résultats montrent (i) le rôle important des taxons clés sur l'assemblage de la communauté bactérienne vectorielle (ii) la pertinence des vaccins anti-microbiote comme outil de microbiologie de précision pour l'étude des interactions vecteur-microbiote et la perturbation du microbiome du vecteur en tant que moyens de contrôler les MTV et (iii) l'impact majeur que le microbiote vecteur a sur la colonisation des agents pathogènes au sein du vecteur. Les résultats de la thèse éclaireront de nouvelles approches pour développer des vaccins bloquant la transmission et ainsi, contrôler les MTV.Animal and human pathogens, principally those transmitted by blood feeding arthropods such as tick and mosquitoes are a global public health concern. Although several strategies were developed and used to control vector-borne diseases (VBDs), half of the world's population still lives today at risk of VBDs. Therefore, the search of new strategies to block VBDs with better outcomes is needed. Several studies emphasize the pivotal role that vector microbiome has on vector fitness and vector competence. Vector microbiome perturbation has been proposed as a mean for the control of VBDs. In the present thesis, we used a network approach to study the relevance of keystone bacteria in vector microbiota and propose anti-microbiota vaccines as a tool for the precise manipulation of vector microbiome, with implications for the study of vector-microbiota interactions and the control of VBDs. The results obtained showed that keystone taxa are important and influential bacterial members of the vector microbiota. Firstly, we demonstrated that keystone taxa have an important role maintaining the functional stability of tick microbiome under heat stress. Secondly, targeting keystone taxa of vector microbiota with host antibodies we showed that anti-microbiota vaccines decrease pathogen colonization in ticks and mosquitoes.Specifically, we showed that targeting keystone taxa using anti-microbiota vaccine decrease the connectedness of keystone taxa in the microbial network which has a cascading ecological impact resulting in an extensive modulation of the taxonomic and functional profile of tick microbiota. Notably, the perturbation of tick microbiome reduced Borrelia afzelii, the causative agent of Lyme borreliosis in Europe, colonization within Ixodes ricinus ticks. This outcome was not limited to the tick vector since we also demonstrated that perturbation of mosquitoes also decreased Plasmodium relictum, the causative agent of avian malaria, development in its natural vector Culex quinquefasciatus. Altogether, these results show (i) the important role of keystone taxa on vector bacterial community assembly (ii) the suitability of anti-microbiota vaccines as a precision microbiology tool for the study of vector-microbiota interactions and the perturbation of vector microbiome as a means to control VBDs and (iii)the major impact that vector microbiota has on pathogen colonization within the vector. The results of the thesis will inform novel approaches to develop transmission-blocking vaccines and control VBDs

Direct Cytotoxic and Indirect, Immune-Mediated Effects of Local Anesthetics Against Cancer

International audienceLocal anesthetics are frequently employed during surgery in order to control peri-and postoperative pain. Retrospective studies have revealed an unexpected correlation between increased long-term survival and the use of local anesthetics during oncological surgery. This effect of local anesthetics might rely on direct cytotoxic effects on malignant cells or on indirect, immune-mediated effects. It is tempting to speculate, yet needs to be formally proven, that the combination of local anesthetics with oncological surgery and conventional anticancer therapy would offer an opportunity to control residual cancer cells. This review summarizes findings from fundamental research together with clinical data on the use of local anesthetics as anticancer standalone drugs or their combination with conventional treatments. We suggest that a better comprehension of the anticancer effects of local anesthetics at the preclinical and clinical levels may broadly improve the surgical treatment of cancer

Immunological Effects of Epigenetic Modifiers

Epigenetic alterations are associated with major pathologies including cancer. Epigenetic dysregulation, such as aberrant histone acetylation, altered DNA methylation, or modified chromatin organization, contribute to oncogenesis by inactivating tumor suppressor genes and activating oncogenic pathways. Targeting epigenetic cancer hallmarks can be harnessed as an immunotherapeutic strategy, exemplified by the use of pharmacological inhibitors of DNA methyltransferases (DNMT) and histone deacetylases (HDAC) that can result in the release from the tumor of danger-associated molecular patterns (DAMPs) on one hand and can (re-)activate the expression of tumor-associated antigens on the other hand. This finding suggests that epigenetic modifiers and more specifically the DNA methylation status may change the interaction of chromatin with chaperon proteins including HMGB1, thereby contributing to the antitumor immune response. In this review, we detail how epigenetic modifiers can be used for stimulating therapeutically relevant anticancer immunity when used as stand-alone treatments or in combination with established immunotherapies

Influence of microbiota-driven natural antibodies on dengue transmission

Dengue has had a significant global health impact, with a dramatic increase in incidence over the past 50 years, affecting more than 100 countries. The absence of a specific treatment or widely applicable vaccine emphasizes the urgent need for innovative strategies. This perspective reevaluates current evidence supporting the concept of dual protection against the dengue virus (DENV) through natural antibodies (NAbs), particularly anti-α-Gal antibodies induced by the host’s gut microbiome (GM). These anti-α-Gal antibodies serve a dual purpose. Firstly, they can directly identify DENV, as mosquito-derived viral particles have been observed to carry α-Gal, thereby providing a safeguard against human infections. Secondly, they possess the potential to impede virus development in the vector by interacting with the vector’s microbiome and triggering infection-refractory states. The intricate interplay between human GM and NAbs on one side and DENV and vector microbiome on the other suggests a novel approach, using NAbs to directly target DENV and simultaneously disrupt vector microbiome to decrease pathogen transmission and vector competence, thereby blocking DENV transmission cycles