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Escherichia coli is a ubiquitous commensal and pathogen that has also been recognized as a multi-sectoral indicator of antimicrobial resistance (AMR). Given that latter focus, such as on resistances to extended-spectrum cephalosporins (ESC) and carbapenems, the reported population structure of E. coli is generally biased toward resistant isolates, with sequence type (ST)131 being widely reported in humans, and ST410 and ST648 being reported in animals. In this study, we characterized 618 non-duplicate E. coli isolates collected throughout France independently of their resistance phenotype. The B2 phylogroup was over-represented (79.6%) and positively associated with the presence of numerous virulence factors (VFs), including those defining the extra-intestinal pathogenic E. coli isolates (presence of ≥2 VFs: papA, sfaS, focG, afaD, iutA, and kpsMTII) and those more specifically related to uropathogenic E. coli (cnf1, hlyD). The major STs associated with clinical isolates from dogs were by far the dog-associated ST372 (20.7%) and ST73 (20.1%), a lineage that had commonly been considered until now as human-associated. Resistance to ESC was found in 33 isolates (5.3%), along with one carbapenemase-producing isolate, and was mostly restricted to non-B2 isolates. In conclusion, the presence of virulent E. coli lineages may be the issue, rather than the presence of ESC-resistant isolates, and the risk of transmission of such virulent isolates to humans needs to be further studied.

Prion diseases belong to the family of neurodegenerative disorders. They are characterized by the presence, in the central nervous system, of host proteins that by changing conformation and forming soluble multimeric aggregates, and fibrillar amyloid plaques become neurotoxic. To date, there is no treatment capable of deeply modifying the dramatic and lethal course of those diseases. Accumulating clinical and experimental data have nevertheless shown that innate and adaptive immune agents could slow down the course of neurodegenerative pathologies. Immunotherapy has become a promising therapeutic tool, despite the fact that the outcome of the first clinical trials has not fulfilled all promises. First, we will review currently developed strategies, most of them based on the use of antibodies directed against pathogenic proteins. Then, we will discuss alternative strategies relying on cellular immunity, and we will present our latest results involving the adoptive transfer of T lymphocytes. We will conclude by discussing pending issues and questions in the quest for safe and efficient treatments against neurodegenerative diseases., Les maladies à prions appartiennent à la famille des maladies neurodégénératives. Celles-ci se caractérisent par la présence, dans le système nerveux central, de protéines constitutives de l’hôte qui en changeant de conformation et en formant, dans un premier temps, des agrégats multimériques solubles, puis secondairement des dépôts fibrillaires de type amyloïde, deviennent neurotoxiques. Il n’existe à ce jour aucun traitement de fond capable de modifier le cours dramatique et inexorable de ces pathologies. Des données cliniques et expérimentales se sont cependant récemment accumulées montrant que des effecteurs de l’immunité innée et adaptative pouvaient freiner leur développement. L’immunothérapie est devenue l’une des voies les plus prometteuses de traitement, même si les premiers résultats ne sont pas encore à la hauteur des espérances. Nous commencerons par une évaluation critique des stratégies actuellement développées, essentiellement fondées sur la mise en jeu d’anticorps dirigés contre les protéines pathogènes. Nous discuterons ensuite de l’opportunité de mettre en oeuvre des approches alternatives reposant sur l’immunité cellulaire, et présenterons nos derniers résultats concernant le transfert adoptif de lymphocytes T. Nous conclurons enfin sur une liste de questions ouvertes dont il ne sera sans doute pas possible de faire l’économie pour parvenir à des solutions thérapeutiques sûres et efficaces., Bachy Véronique, Carnaud Claude. Immunothérapie des maladies neurodégénératives: le temps est-il venu de changer de paradigme ?. In: Bulletin de l'Académie Vétérinaire de France tome 164 n°2, 2011. pp. 105-112.

Prion diseases are caused by the transconformation of a normal cellular protein, PrPc, into an infectious isoform, PrPsc, which ultimately triggers neuronal death. They are always fatal and, after transmission, they feature long incubation periods, during which prions accumulate in lymphoid tissues, infect nerves and progress to the central nervous system. In lymphoid organs, prions replicate and accumulate in follicular dendritic cells. Suppressing these cells slows down the neuro-invasion but does not totally abrogate it. This review examines the current knowledge in the roles of hematopoietic dendritic cells at different steps of the pathogenesis of prion diseases. Dendritic cells endocytose inoculated prions, permit their crossing of the intestinal epithelium and then migrate and transport them to lymphoid organs. They can carry prions to sites of neuroinvasion, and establish contacts with axons in peripheral lymph nodes or even after passage of the blood-brain barrier. However, results in the literature on the role of dendritic cells differ according to the host or the prion strain.

There is to date no effective way of preventing or curing neurodegenerative diseases such as Alzheimer disease or transmissible spongiform encephalopathies. The idea of treating those conditions by immunological approaches has progressively emerged over the last ten years. Encouraging results have been reported in Alzheimer disease and in peripheral forms of mouse prion diseases following passive injection of Abs or active immunization against the peptides or proteins presumably at the origin of those disorders. Still, major difficulties persist due to some characteristics of those conditions such as slow evolution, brain location, uncertainties regarding precise pathogenic pathways, and, above all, the fact that the target Ag is self, meaning that it is poorly immunogenic and potentially harmful if tolerance was transgressed. To analyze some of those difficulties, we are developing adoptive cell transfer approaches. In this study, lymphocytes sensitized against the prion protein in nontolerant Prnp−/− mice were transferred into histocompatible wild-type recipients which were partly or totally devoid of their own lymphocytes. Under such conditions, we found that the engrafted T lymphocytes resisted peripheral tolerance, remained reactive for several months against epitopes of the prion protein, and significantly attenuated the progression of prions in secondary lymphoid organs with subsequent delay in the evolution of the neurological disease. Interestingly, those protective T lymphocytes secreted lymphokines and migrated more readily into the host CNS but did not appear to be engaged in cooperation with host B cells for Ab production.

Monocytes acquire a dendritic cell (DC) phenotype when cultured with GM-CSF and IL-4. By contrast, CSF-1 is a potent inducer of monocyte-to-macrophage differentiation. Increasing evidence indicates that DC development is impaired in conditions characterized by CSF-1 overproduction, including pregnancy, trauma, and diverse malignancies. To study this, we have exposed newly established monocyte-derived DC cultures to conditions of CSF-1 excess. As a consequence, differentiation is skewed toward a unique intermediate phenotype, which we have termed DC-M. Such cells exhibit macrophage-like morphology with impaired allostimulatory capacity, altered cytokine production, and a distinctive cell surface immunophenotype. In light of the emerging role of caspase activation during macrophage differentiation, the activity of caspases 3, 8, and 9 was examined in DC and DC-M cultures. It is striking that DC-M cultures exhibit a delayed and progressive increase in activation of all three caspases, associated with depolarization of mitochondrial membrane potential. Furthermore, when DC-M cultures were supplemented with an inhibitor of caspase 8 or caspase 9, impairment of DC differentiation by CSF-1 was counteracted. To investigate upstream regulators of caspase activation in DC-M cultures, experiments were performed using inhibitors of proximal CSF-1 receptor signaling. These studies demonstrated that the PI-3K inhibitors, wortmannin and LY294002, antagonize the ability of CSF-1 to inhibit DC differentiation and to promote caspase activation. Together, these data identify a novel, PI-3K-dependent pathway by which CSF-1 directs delayed caspase activation in monocytes and thereby modulates DC differentiation.

Molecular epidemiology represents a powerful approach to elucidate the complex epidemiological cycles of multi-host pathogens, such as Anaplasma phagocytophilum. A. phagocytophilum is a tick-borne bacterium that affects a wide range of wild and domesticated animals. Here, we characterized its genetic diversity in populations of French cattle; we then compared the observed genotypes with those found in horses, dogs, and roe deer to determine whether genotypes of A. phagocytophilum are shared among different hosts. We sampled 120 domesticated animals (104 cattle, 13 horses, and 3 dogs) and 40 wild animals (roe deer) and used multilocus sequence analysis on nine loci (ankA, msp4, groESL, typA, pled, gyrA, recG, polA, and an intergenic region) to characterize the genotypes of A. phagocytophilum present. Phylogenic analysis revealed three genetic clusters of bacterial variants in domesticated animals. The two principal clusters included 98% of the bacterial genotypes found in cattle, which were only distantly related to those in roe deer. One cluster comprised only cattle genotypes, while the second contained genotypes from cattle, horses, and dogs. The third contained all roe deer genotypes and three cattle genotypes. Geographical factors could not explain this clustering pattern. These results suggest that roe deer do not contribute to the spread of A. phagocytophilum in cattle in France. Further studies should explore if these different clusters are associated with differing disease severity in domesticated hosts. Additionally, it remains to be seen if the three clusters of A. phagocytophilum genotypes in cattle correspond to distinct epidemiological cycles, potentially involving different reservoir hosts. Electronic supplementary material The online version of this article (doi:10.1186/s13567-014-0114-7) contains supplementary material, which is available to authorized users.

Prion diseases are caused by the transconformation of a normal cellular protein, PrPc, into an infectious isoform, PrPsc, which ultimately triggers neuronal death. They are always fatal and, after transmission, they feature long incubation periods, during which prions accumulate in lymphoid tissues, infect nerves and progress to the central nervous system. In lymphoid organs, prions replicate and accumulate in follicular dendritic cells. Suppressing these cells slows down the neuro-invasion but does not totally abrogate it. This review examines the current knowledge in the roles of hematopoietic dendritic cells at different steps of the pathogenesis of prion diseases. Dendritic cells endocytose inoculated prions, permit their crossing of the intestinal epithelium and then migrate and transport them to lymphoid organs. They can carry prions to sites of neuroinvasion, and establish contacts with axons in peripheral lymph nodes or even after passage of the blood-brain barrier. However, results in the literature on the role of dendritic cells differ according to the host or the prion strain.

Prion diseases are presumed to be caused by the accumulation in the brain of a pathological protein called prion protein (PrP) scrapie which results from the transconformation of cellular PrP, a ubiquitous glycoprotein expressed in all mammals. Since all isoforms of PrP are perceived as self by the host immune system, a major problem in designing efficient immunoprophylaxis or immunotherapy is to overcome tolerance. The present study was aimed at investigating whether bone-marrow-derived dendritic cells (DCs) loaded with peptides previously shown to be immunogenic in PrP-deficient mice, can overcome tolerance in PrP-proficient wild-type mice and protect them against scrapie. Results show that, in such mice, peptide-loaded DCs elicit both lymphokine release by T cells and antibody secretion against native cellular PrP. Repeated recalls with peptide-loaded DCs reduces the attack rate of 139A scrapie inoculated intraperitoneally and retards disease duration by 40 days. Most interestingly, survival time in individual mice appears to be correlated with the level of circulating antibody against native cellular PrP.

The cellular prion protein (PrPC) is a host-encoded, GPI-anchored cell surface protein, expressed on a wide range of tissues including neuronal and lymphoreticular cells. PrPC may undergo posttranslational conversion, giving rise to scrapie PrP, the pathogenic conformer considered as responsible for prion diseases. Despite intensive studies, the normal function of PrPC is still enigmatic. Starting from microscope observations showing an accumulation of PrPC at the sites of contact between T cells and Ag-loaded dendritic cells (DC), we have studied the contribution of PrPC in alloantigen and peptide-MHC-driven T/DC interactions. Whereas the absence of PrPC on the DC results in a reduced allogeneic T cell response, its absence on the T cell partner has no apparent effect upon this response. Therefore, PrPC seems to fulfill different functions on the two cell partners forming the synapse. In contrast, PrPC mobilization by Ab reduces the stimulatory properties of DC and the proliferative potential of responding T cells. The contrasted consequences, regarding T cell function, between PrPC deletion and PrPC coating by Abs, suggests that the prion protein acts as a signaling molecule on T cells. Furthermore, our results show that the absence of PrPC has consequences in vivo also, upon the ability of APCs to stimulate proliferative T cell responses. Thus, independent of neurological considerations, some of the evolutionary constraints that may have contributed to the conservation of the Prnp gene in mammalians, could be of immunological origin.

Prion diseases or transmissible subacute spongiform encephalopathies (TSSE) are fatal neurodegenerative conditions, for which there is so far no known treatment or prevention. Promising results achieved in the field of Alzheimer disease give however some reasons to hope that individuals with the disease or individuals at risk might benefit from similar immunoprophylactic or immunotherapeutic approaches. This article reviews current knowledge on the immunology of prion diseases. In the first section we describe the known routes of prion lymphoinvasion from the periphery to the sites of neuroinvasion. The second section focuses on the mediators of innate immunity mobilized within the central nervous system and on their ambivalent role in the pathogenesis of the disease. The final section describes the vaccine approaches aimed at stimulating adaptive immunity and at creating, in association with the mediators of the innate immune system, a defence barrier against prions., Les maladies à prions ou encéphalopathies spongiformes subaiguës transmissibles (ESST) sont des affections neurodégénératives fatales, contre lesquelles il n’existe à ce jour aucun traitement ou prophylaxie connu. Des résultats encourageants obtenus dans la maladie d’Alzheimer, laissent toutefois espérer que des approches immunoprophylactiques ou immunothérapeutiques puissent un jour être mises en oeuvre chez des sujets atteints d’ESST ou chez des sujets à risque. Ce mémoire vise à faire le point dans ce domaine. Dans une première partie, nous décrivons les voies connues de la lymphoinvasion dans les formes acquises de maladie, voies à travers lesquelles les prions progressent au sein même du système lymphoïde, depuis la périphérie jusqu’au sytème nerveux central. Dans une deuxième partie, nous mettons l’accent sur les agents de l’immunité innée mobilisés dans le système nerveux central et sur leur rôle ambivalent dans la pathogénie des ESST. Enfin, la dernière partie est consacrée aux approches vaccinales destinées à stimuler l’immunité adaptative et à construire, en collaboration avec le système immunitaire inné, une barrière défensive contre l’agent pathogène., Carnaud Claude, Bachy Véronique. Perspectives immunoprophylactiques et immunothérapeutiques contre les maladies à prions. In: Bulletin de l'Académie Vétérinaire de France tome 159 n°1, 2006. pp. 15-29.

T lymphocytes of fetal origin found in maternal circulation after gestation have been reported as a possible cause for autoimmune diseases. During gestation, mothers acquire CD34+CD38+ cells of fetal origin that persist decades. In this study, we asked whether fetal T and B cells could develop from these progenitors in the maternal thymus and bone marrow during and after gestation. RAG−/−-deficient female mice (Ly5.2) were mated to congenic wild-type Ly5.1 mice (RAG+/+). Fetal double-positive T cells (CD4+CD8+) with characteristic TCR and IL-7R expression patterns could be recovered in maternal thymus during the resulting pregnancies. We made similar observations in the thymus of immunocompetent mothers. Such phenomenon was observed overall in 12 of 68 tested mice compared with 0 of 51 controls (p = 0.001). T cells could also be found in maternal spleen and produced IFN-γ in the presence of an allogenic or an Ag-specific stimulus. Similarly, CD19+IgM+ fetal B cells as well as plasma Igs could be found in maternal RAG−/− bone marrow and spleen after similar matings. Our results suggest that during gestation mothers acquire fetal lymphoid progenitors that develop into functional T cells. This fetal cell microchimerism may have a direct impact on maternal health.