Étude de la différenciation des lymphocytes T CD8+ effecteurs et mémoires : rôle de la cellule présentatrice d’antigène et de la voie de signalisation Notch

Lors d’une infection par un pathogène, des lymphocytes T CD8+ naïfs (LTn) spécifiques de l’antigène sont activés, prolifèrent et se différencient en LT effecteurs (LTe). Les LTe produisent différentes cytokines et acquièrent une activité cytotoxique menant à l’élimination du pathogène. Seulement 5 à 10 % des LTe survivront et se différencieront en LT mémoires (LTm), qui sont capables de répondre plus rapidement lors d’une seconde infection par le même pathogène, contribuant au succès de la vaccination. Toutefois, la compréhension de l’ensemble des mécanismes régulant le développement des LTe et des LTm demeure incomplète. Afin de mieux comprendre les signaux requis pour la différenciation des LT CD8+ lors de la réponse immune, nous avons posé deux hypothèses. Nous avons d’abord proposé que différentes cellules présentatrices d’antigène (CPA) fournissent différents signaux au moment de la reconnaissance antigénique influençant ainsi le devenir des LT CD8+. Vu leur potentiel d’utilisation en immunothérapie, nous avons comparé la capacité d’activation des LT CD8+ par les lymphocytes B activés via le CD40 (CD40-B) et les cellules dendritiques (CD). Nous avons montré que l’immunisation avec des CD40-B induit une réponse effectrice mais, contrairement à l’immunisation avec des CD, pratiquement aucun LTm n’est généré. Les LTe générés sont fonctionnels puisqu’ils sécrètent des cytokines, ont une activité cytotoxique et contrôlent une infection avec Listeria monocytogenes (Lm). Nous proposons qu’une sécrétion plus faible de cytokines par les CD40 B ainsi qu’une interaction plus courte et moins intime avec les LT CD8+ comparativement aux CD contribuent au défaut de différenciation des LTm observé lors de la vaccination avec les CD40-B. Ensuite, nous posé l’hypothèse que, parmi les signaux fournis par les CPA au moment de la reconnaissance antigénique, la voie de signalisation Notch influence le développement des LTe, mais aussi des LTm CD8+ en instaurant un programme génétique particulier. D’abord, grâce à un système in vitro, le rôle de la signalisation Notch dans les moments précoces suivant l’activation du LT CD8+ a été étudié. Ce système nous a permis de démontrer que la voie de signalisation Notch régule directement l’expression de la molécule PD-1. Ensuite, grâce à des souris où il y a délétion des récepteurs Notch1 et Notch2 seulement chez les LT CD8+ matures, un rôle de la voie de signalisation Notch dans la réponse immune des LT CD8+ a été démontré. Nos résultats démontrent que suite à une infection avec Lm ou à une immunisation avec des CD, la signalisation Notch favorise le développement de LTe, exprimant fortement KLRG1 et faiblement CD127, destinés à mourir par apoptose. Toutefois, la signalisation Notch n’a pas influencé la génération de LTm. De façon très intéressante, l’expression des récepteurs Notch influence la production d’IFN- en fonction du contexte d’activation. En effet, suite à une infection avec Lm, l’absence des récepteurs Notch n’affecte pas la production d’IFN- par les LTe, alors qu’elle est diminuée suite à une immunisation avec des CD suggérant un rôle dépendant du contexte pour la voie de signalisation Notch. Nos résultats permettent une meilleure compréhension des signaux fournis par les différentes CPA et de la voie de signalisation Notch, donc des mécanismes moléculaires régulant la différenciation des LT CD8+ lors de la réponse immunitaire, ce qui pourrait ultimement permettre d’améliorer les stratégies de vaccination.Following an infection with a pathogen, antigen-specific naive CD8+ T lymphocytes (Tn) will proliferate and differentiate into effector (Te) cells. Those Te cells will produce different cytokines and acquire a cytotoxic activity, leading to pathogen clearance. Only 5 to 10 % of Te cells will survive and differentiate into memory CD8+ T lymphocytes (Tm) able to respond rapidly following a second encounter with the same pathogen, contributing to the success of vaccination. However, the mechanisms regulating Te and Tm cells development remain incompletely understood. To better understand the signals required for CD8+ T lymphocytes during an immune response, we proposed two hypotheses. First, we propose that different antigen presenting cells (APCs) can deliver different signals to CD8+ T lymphocytes at the time of priming leading to different outcome. Given their potential for use in immunotherapy, we compared the ability of CD40 activated B lymphocytes (CD40-B) and dendritic cells (DCs) to activate CD8+ T lymphocytes. We have shown that CD40-B cell immunisation leads to an effector response but very few Tm cells are generated compared to DC immunisation. The Te cells generated following CD40-B cell immunisation are functional because they secrete cytokine, are cytotoxic and control a Listeria monocytogenes (Lm) infection. We propose that CD40-B cells secrete less cytokines and interact during shorter period of time with the CD8+ T lymphocytes, without engulfment, contributing to the decreased Tm generation observed following immunisation with CD40-B cells. Second, among the signals provided by APC at the time of CD8+ T lymphocyte priming, we have hypothesised that the Notch signalling pathway influences Te and Tm cell differentiation by inducing a particular genetic program. Using an in vitro system, we first studied the role of the Notch signalling pathway in the hours following CD8+ T lymphocyte priming. We demonstrated that Notch signalling directly regulates PD-1 expression. Then, studying mice where Notch1 and Notch2 receptor genes are deleted only in mature CD8+ T lymphocytes, we characterised the role of the Notch signalling pathway on Te and Tm differentiation during an immune response. Our results show that following Lm infection or a DC immunisation, the Notch signalling pathway promotes the differentiation of short lived effector cells Te cells (KLRG1highCD127low) meant to die by apoptosis. However, the Notch signalling pathway did not influence the generation of CD8+ Tm cells. Most interestingly, IFN- regulation by the Notch signalling pathway depends on the activation context. Indeed, following Lm infection, lack of Notch receptors does not impact IFN- secretion by Te cells while it is significantly decreased following a DC immunisation suggesting a context dependant role for the Notch signalling pathway. Our findings provide a better understanding of the key signals provided by APC as well as the Notch signalling pathway, and thus the molecular mechanisms leading to CD8+ lymphocyte effector and memory generation which is crucial as this knowledge may ultimately lead to improved vaccination

A salutogenic approach to disaster recovery: the case of the Lac-Mégantic rail disaster

In July 2013, a train carrying crude oil derailed in Lac-Mégantic (Canada). This disaster provoked a major fire, 47 deaths, the destruction of 44 buildings, a massive evacuation, and an unparalleled oil spill. Since 2013, Public Health has undertaken several actions to address this challenging situation, using both quantitative and qualitative methods. Community-based surveys were conducted in Lac-Mégantic in 2014, 2015 and 2018. The first two surveys showed persistent and widespread health needs. Inspired by a salutogenic approach, Public Health has shifted its focus from health protection to health promotion. In 2016, a Day of Reflection was organized during which a map of community assets and an action plan for the community recovery were co-constructed with local stakeholders. The creation of an Outreach Team is an important outcome of this collective reflection. This team aims to enhance resilience and adaptive capacity. Several promising initiatives arose from the action plan—all of which greatly contributed to mobilize the community. Interestingly, the 2018 survey suggests that the situation is now evolving positively. This case study stresses the importance of recognizing community members as assets, rather than victims, and seeking a better balance between health protection and health promotion approaches

The “Lac-Mégantic tragedy” seen through the lens of the EnRiCH community resilience framework for high-risk populations

Setting : On July 6, 2013, a train carrying oil derailed in downtown Lac-Mégantic (Quebec, Canada), causing major human, environmental, and economic impacts. We aim to describe, and learn from, public health strategies developed to enhance community resilience following the train derailment though the lens of the EnRiCH Community Resilience Framework for High-Risk Populations. Intervention : Annual population-level surveys were conducted in Lac-Mégantic and surrounding areas to assess the long-term impacts of the disaster. Findings suggested that a solid upstream investment towards the development of adaptive capacity was needed. A “Day of Reflection” bringing together local stakeholders and citizens was organized, inspiring the elaboration of an innovative action plan. Leaders advocated for funding to support its implementation, leading to a substantial investment from the provincial government. Through a wide range of actions, the plan aims to bring psychosocial services closer to people, stay connected with the community, and foster community engagement. Outcomes : Several lessons have been identified. After a disaster, there needs to be a balanced focus between the gaps/needs and strengths/capacities of a community. Moreover, public health actors must collaborate closely, all along the continuum of the upstream-downstream paradigm, with local organizations and citizens. Implications : This unique experience, supported by an empirically-based framework, suggests that three vital ingredients are required for success in recovering from a disaster: (1) fostering community strengths and valuing citizen participation, (2) a strong political commitment to support upstream actions, and (3) a public health team able to support these actions. Contexte : Le 6 juillet 2013, un train transportant du pétrole déraillait au centre-ville de Lac-Mégantic (Québec, Canada), causant des impacts majeurs sur le plan humain, environnemental et économique. Notre objectif est de décrire les stratégies de santé publique développées pour favoriser la résilience communautaire suivant la tragédie ferroviaire et d’en tirer des leçons, à travers la lentille du « EnRiCH Community Resilience Framework for High-Risk Populations ». Intervention : Des enquêtes populationnelles ont été réalisées annuellement à Lac-Mégantic et les environs pour examiner les conséquences à long terme de la catastrophe. Les résultats suggèrent qu’un important effort en amont était nécessaire afin de développer la capacité d’adaptation. Une journée de réflexion rassemblant des partenaires locaux et des citoyens a été organisée, inspirant l’élaboration d’un plan d’action innovant. Les leaders ont plaidé pour l’obtention d’un financement afin de soutenir son implantation, ce qui a mené à un investissement substantiel du gouvernement du Québec. À travers un large éventail d’actions, le plan vise à rapprocher les services psychosociaux de la population, rester connecté avec la communauté et promouvoir la mobilisation communautaire. Retombées : Plusieurs leçons ont été tirées. Après une catastrophe, on doit porter une attention à la fois sur les lacunes/besoins et les forces/capacités de la communauté. De plus, les acteurs de santé publique doivent collaborer étroitement, autant en amont qu’en aval, avec les organisations locales et les citoyens. Implications : Cette expérience unique, soutenue par un cadre fondé sur des données empiriques, suggère que trois composantes sont essentielles au succès du rétablissement post-catastrophe: (1) la valorisation des forces de la communauté et de la participation citoyenne, (2) un engagement politique fort pour soutenir les actions en amont, et (3) une équipe de santé publique capable de soutenir ces actions

Associations between resilience, community belonging, and social participation among community-dwelling older adults: results from the Eastern Townships Population Health Survey

Objective : To examine the associations between resilience, community belonging, and social participation, and the moderating effect of resilience on the association between community belonging and social participation among community-dwelling older adults. Design : Cross-sectional; secondary analyses of the Eastern Townships Population Health Survey. Setting : Community. Participants : A sample (N=4541) of women (n=2485) and men (n=2056) aged ≥60 years was randomly selected according to area. Most participants had <14 years of schooling, owned their dwelling, were retired, had 1 or 2 chronic conditions, and did not have depressive symptoms. Interventions : Not applicable. Main Outcome Measures : Self-reported data on age, education, depressive symptoms, social participation, community belonging, and resilience were collected by phone interviewer–administered questionnaire. A social participation scale measured frequency of participation in 8 community activities. A 4-point Likert scale ranging from “very strong” to “very weak” estimated sense of belonging to the local community. Social participation and sense of belonging questions came from Statistics Canada surveys. Resilience was assessed with the 10-item Connor-Davidson Resilience Scale, capturing the ability to cope with adversity. Results : Controlling for age, education, and psychological distress, greater resilience and community belonging were associated with greater social participation among women (R2=.13; P<.001) and men (R2=.09; P<.001). The association between community belonging and social participation varied as a function of resilience, especially in men. Greater community belonging further enhanced social participation, especially among women (P=.03) and men (P<.01) with greater resilience (moderator effect). Conclusions : Resilience moderates the association between community belonging and social participation among community-dwelling older women and, especially, men. Interventions targeting social participation should consider the potential impact of resilience on improving community belonging. Future studies should investigate why resilience moderates associations between community belonging and social participation, and how to enhance resilience among older adults

Medium-term effects of a train derailment on the physical and psychological health of men

In July 2013, the derailment of a train caused the death of 47 people and the destruction of Lac-Mégantic’s downtown area (Canada). Three years after this event, a population survey was conducted among a representative sample of 800 adults, including 282 men. Several significant differences were observed among respondents of a survey based on their level of exposure to this tragedy, including their physical (changes in physical health) and psychological health (post-traumatic stress disorder, mood and anxiety disorders, psychological distress, signs of depression, consultation of social workers and psychologists) as well as their use of prescribed (anxiolytics and antidepressants) and nonprescribed drugs. Such results can be explained by the nature, magnitude, and cause of the event

Post-disaster health status of train derailment victims with posttraumatic growth

In July 2013, a train derailment causing explosions and a fire in downtown Lac-Mégantic (Municipalité Régionale de Comté du Granit, Quebec, Canada) resulted in the death of 47 people and the destruction of many homes and other buildings. This article compares the physical and psychological health of 624 adults from the Granit area exposed to this disaster three years after the tragedy, comparing based on the presence or absence of posttraumatic growth. Women, people with high levels of social support, lower levels of education, and with lower incomes were more likely to show posttraumatic growth. For psychological health, the presence of post-traumatic stress symptoms and the use of antidepressants were positively related to posttraumatic growth. Our study demonstrates that, over time, many people managed to initiate a recovery process and to see benefits from this disaster

Looking for capacities rather than vulnerabilities: the moderating effect of health assets on the associations between adverse social position and health

To increase capacities and control over health, it is necessary to foster assets (i.e. factors enhancing abilities of individuals or communities). Acting as a buffer, assets build foundations for overcoming adverse conditions and improving health. However, little is known about the distribution of assets and their associations with social position and health. In this study, we documented the distribution of health assets and examined whether these assets moderate associations between adverse social position and self-reported health. A representative population-based cross-sectional survey of adults in the Eastern Townships, Quebec, Canada (n = 8737) was conducted in 2014. Measures included assets (i.e. resilience, sense of community belonging, positive mental health, social participation), self-reported health (i.e. perceived health, psychological distress), and indicators of social position. Distribution of assets was studied in relation to gender and social position. Logistic regressions examined whether each asset moderated associations between adverse social position and self-reported health. Different distributions of assets were observed with different social positions. Women were more likely to participate in social activities while men were more resilient. Resilience and social participation were moderators of associations between adverse social position (i.e. living alone, lower household income) and self-reported health. Having assets contributes to better health by increasing capacities. Interventions that foster assets and complement current public health services are needed, especially for people in unfavorable situations. Health and social services decision-makers and practitioners could use these findings to increase capacities and resources rather than focusing primarily on preventing diseases and reducing risk factors

Development of Real-Time Isothermal Amplification Assays for On-Site Detection of Phytophthora infestans in Potato Leaves

Real-time loop-mediated isothermal amplification (LAMP) and recombinase polymerase amplification (RPA) assays were developed targeting the internal transcribed spacer 2 region of the ribosomal DNA of Phytophthora infestans, the potato late blight causal agent. A rapid crude plant extract (CPE) preparation method from infected potato leaves was developed for on-site testing. The assay's specificity was tested using several species of Phytophthora and other potato fungal and oomycete pathogens. Both LAMP and RPA assays showed specificity to P. infestans but also to the closely related species P. andina, P. mirabilis, P. phaseoli, and P. ipomoeae, although the latter are not reported as potato pathogen species. No cross-reaction occurred with P. capsici or with the potato pathogens tested, including P. nicotianae and P. erythroseptica. The sensitivity was determined using P. infestans pure genomic DNA added into healthy CPE samples. Both LAMP and RPA assays detected DNA at 50 fg/μl and were insensitive to CPE inhibition. The isothermal assays were tested with artificially inoculated and naturally infected potato plants using a Smart-DART platform. The LAMP assay effectively detected P. infestans in symptomless potato leaves as soon as 24 h postinoculation. A rapid and accurate on-site detection of P. infestans in plant material using the LAMP assay will contribute to improved late blight diagnosis and early detection of infections and facilitate prompt management decisions

Abdominal adipocyte populations in women with visceral obesity

Visceral obesity is independently related to numerous cardiometabolic alterations, with adipose tissue dysfunction as a central feature. Objective: To examine whether omental (OM) and subcutaneous (SC) adipocyte size populations in women relate to visceral obesity, cardiometabolic risk factors and adipocyte lipolysis independent of total adiposity. Design and Methods: OM and SC fat samples were obtained during gynecological surgery in 60 women [mean age: 46.1±5.9 years; mean BMI: 27.1±4.5 kg/m2 (range: 20.3-41.1 kg/m2)]. Fresh samples were treated with osmium tetroxide and were analyzed with a Multisizer Coulter. Cell size distributions were computed for each sample with exponential and Gaussian function fits. Results: Computed tomography-measured visceral fat accumulation was the best predictor of larger cell populations as well as the percentage of small cells in both OM and SC fat (p<0.0000 for all). Accordingly, women with visceral obesity had larger cells in the main population and higher proportion of small adipocytes independent of total adiposity (p≤0.05). Using linear regression analysis, we found that women characterized by larger-than-predicted adipocytes in either OM or SC adipose tissue presented higher visceral adipose tissue area, increased percentage of small cells and HOMAir index as well as higher OM adipocyte isoproterenol-, forskolin- and dibutyryl cAMP- stimulated lipolysis compared to women with smaller-than predicted adipocytes, independent of total adiposity (p≤0.05). Conclusion: Excess visceral adipose tissue accumulation is a strong marker of both adipocyte hypertrophy and increased number of small cells in either fat compartment, which relates to higher insulin resistance index and lipolytic response, independent of total adiposity