Induction of innate immune responses through Nalp3 inflammasome sensing of asbestos and silica

The inhalation of airborne pollutants such as asbestos or silica is linked to inflammation of the lung, fibrosis and lung cancer. How the presence of pathogenic dust is recognised, and how chronic inflammatory diseases are triggered are poorly understood. We will se show that asbestos and silica are sensed by the Nalp3 inflammasome, whose subsequent activation leads to IL-1b secretion. Inflammasome activation is triggered by reactive oxygen species, which are generated by a NADPH oxidase upon particle phagocytosis. In a model of asbestos inhalation, Nalp3_/_ mice showed diminished recruitment of inflammatory cells to the lungs, paralleled by lower cytokine production. Our findings implicate the Nalp3 inflammasome in particulate matter-related pulmonary diseases and support its role as a major proinflammatory ''danger" receptor.

The endoplasmic reticulum: a sensor of cellular stress that modulates immune responses.

Many inflammatory and infectious diseases are characterized by the activation of signaling pathways steaming from the endoplasmic reticulum (ER). These pathways, primarily associated with loss of ER homeostasis, are emerging as key regulators of inflammation and infection. Recent advances shed light on the mechanisms linking ER-stress and immune responses.

Intrathecal immune responses to EBV in early MS.

EBV has been consistently associated with MS, but its signature in the CNS has rarely been examined. In this study, we assessed EBV-specific humoral and cellular immune responses in the cerebrospinal fluid (CSF) of patients with early MS, other inflammatory neurological diseases (OIND) and non-inflammatory neurological diseases (NIND). The neurotropic herpesvirus CMV served as a control. Virus-specific humoral immune responses were assessed in 123 consecutive patients and the intrathecal recruitment of virus-specific antibodies was expressed as antibody indexes. Cellular immune responses tested in the blood of 55/123 patients were positive in 46/55. The CD8(+) CTL responses of these 46 patients were assessed in the blood and CSF using a CFSE-based CTL assay. We found that viral capsid antigen and EBV-encoded nuclear antigen-1, but not CMV IgG antibody indexes, were increased in early MS as compared with OIND and NIND patients. There was also intrathecal enrichment in EBV-, but not CMV-specific, CD8(+) CTL in early MS patients. By contrast, OIND and NIND patients did not recruit EBV- nor CMV-specific CD8(+) CTL in the CSF. Our data, showing a high EBV-, but not CMV-specific intrathecal immune response, strengthen the association between EBV and MS, in particular at the onset of the disease.

Tumor-reactive, SSX-2-specific CD8+ T cells are selectively expanded during immune responses to antigen-expressing tumors in melanoma patients.

The SSX-2 gene encodes a tumor-specific antigen expressed in neoplasms of various histological types. By analyzing a tumor-infiltrated lymph node of a melanoma patient bearing an SSX-2-expressing tumor, we have recently identified the first SSX-2-derived CD8(+) T-cell epitope, that corresponds to peptide SSX-2(41-49), and is recognized by specific CTL in an HLA-A2 restricted fashion. Here, we have used fluorescent HLA-A2/SSX-2(41-49) peptide multimeric complexes to analyze the response to SSX-2(41-49) in melanoma patients and healthy donors. Multimer(+) CD8(+) T cells were readily detected in the majority of patients bearing SSX-2-expressing tumors and, at lower proportions, in patients with nonexpressing tumors and healthy donors. Importantly, isolated A2/SSX-2(41-49) multimer(+) CD8(+) T cells exhibited a large functional heterogeneity in terms of antigen recognition and tumor reactivity. SSX-2-specific CTLs isolated from tumor-infiltrated lymph node of antigen-expressing patients as well as from the corresponding peripheral blood mononuclear cells exhibited high functional avidity of antigen recognition and efficiently recognized antigen-expressing tumors. In contrast, SSX-2-specific CTLs isolated from patients with undetectable responses in the tumor-infiltrated lymph node, as well as from healthy donors, recognized the antigen with decreased functional avidity and were not tumor reactive. Together, these data indicate that CD8(+) T-cell responses to SSX-2(41-49) frequently occur in SSX-2-expressing melanoma patients and suggest that SSX-2(41-49)-specific CTLs of high avidity and tumor reactivity are selectively expanded during immune responses to SSX-2-expressing tumors in vivo.

Characterization of Epstein-Barr virus-specific immune responses and of the novel cytokine interleukin-26 in patients with multiple sclerosis

RÉSUMÉ La sclérose en plaques (SEP) est une maladie démyélinisante du système nerveux central (SNC) qui touche le plus souvent de jeunes femmes. Bien qu'elle ait été décrite pour la première fois il y a plus de 200 ans, son étiologie n'est pas encore complètement comprise. Contrairement à d'autres maladies purement génétiques, l'épidémiologie de la SEP ne peut être que partiellement expliquée par des facteurs génétiques. Ceci suggère que des facteurs environnementaux pourraient être impliqués dans la pathogenèse de la SEP. Parmi ceux-ci, le virus d'Epstein-Barr (EBV) est un excellent candidat, comme cela a été démontré par de larges études séroépidémiologiques ainsi que pax l'évaluation de la réponse cellulaire dans le sang. Bien que le SNC soit en fait la cible des réponses immunitaires anormales dans la SEP, peu d'études ont été accomplies sur les réponses immunitaires spécifiques à EBV dans ce compartiment. Ceci est particulièrement vrai chez des patients vivants chez lesquels des biopsies sont rarement effectuées, ainsi que pour les réponses cellulaires car très peu de cellules immunitaires peuvent être obtenues du SNC. Nous avons donc développé des conditions de cultures et un readout nous permettant d'étudier le nombre réduit de cellules disponibles dans le liquide céphalo-rachidien (LCR), qui représente le seul matériel pouvant être obtenu du SNC de patients SEP vivants. Nous avons trouvé que les réponses cellulaires et humorales spécifiques à EBV étaient augmentées dans le LCR des patients SEP comparé à du sang pairé, ainsi que par rapport à des patients avec d'autres maladies neurologiques inflammatoires et noninflammatoires. Afin de déterminer si les réponses immunitaires augmentées contre EBV étaient spécifiques à ce virus ou si elles reflétaient simplement une hyperactivation immunitaire aspécifique, nous avons comparé les réponses spécifiques à EBV avec celles spécifiques au cytomegalovirus (CNN). En effet, comme EBV, CNN est un herpesvirus neurotropique qui peut établir des infections latentes, mais ce dernier n'est pas considéré comme étant associé à la SEP. De façon intéressante, les réponses immunitaires spécifiques à CNN trouvées dans le LCR étaient plus basses que dans le sang, et ceci dans toutes les catégories de patients. Ces données suggèrent qu'une réactivation d'EBV pourrait avoir lieu dans le SNC des patients SEP à un stade précoce de la maladie et renforcent fortement l'hypothèse qu'EBV pourrait avoir un rôle déclencheur dans cette maladie. Ainsi, il pourrait être intéressant d'explorer si un traitement ou un vaccin efficace contre EBV peut prévenir le développement de la SEP. On ne connaît toujours pas la raison pour laquelle les réponses immunitaires spécifiques à EBV sont augmentées chez les patients SEP. Une hypothèse est que la réponse immunitaire est qualitativement différente chez les patients SEP par rapports aux contrôles. Pour examiner ceci, nous avons évalué le profile cytokinique de lymphocytes T CD4+ et CD8+ stimulés par EBV, mais nous n'avons pas pu mettre en évidence de différence remarquable entre patients SEP et sujets sains. Cette question reste donc ouverte et d'autres études sont justifiées. Il n'existe pas de marqueur fiable de la SEP. Ici, nous avons trouvé que la cytokine IL-26, récemment décrite, était augmentée dans les lymphocytes T CD8+ des patients avec une SEP secondairement progressive comparé à des patients SEP en poussée, des patients avec une SEP primairement progressive, des patients avec d'autres maladies neurologiques inflammatoires, ou des sujets sains. De plus, nous avons identifié des types de cellules dérivées du cerveau (astrocytes, oligodendrocytes et neurones) qui exprimaient le récepteur de l'IL-26. Ceci ouvre la voie à d'autres études afin de mieux comprendre la fonction de l'II.-26 et son interaction avec la. SEP. SUMMARY : Multiple sclerosis (MS) is a demyelinating disease affecting the central nervous system (CNS), mostly in young female adults. Although it was first described 200 years ago, its etiology is still not completely understood. Contrary to other purely genetic diseases, genetics can explain only part of MS epidemiology. Therefore, environmental factors that might be involved in MS pathogenesis were searched for. Among them, Epstein-Barr virus (EBV) is a strong potential candidate, such as shown by large seroepidemiological studies and cellular immune response assessments in the blood. Although the CNS is the actual target of abnormal immune responses in MS, few studies have been performed on EBV-specific immune responses in this compartment. This is particularly true for live patients, from which biopsy material is almost never available, and for cellular immune responses, since very few immune cells are available from the CNS. We therefore developed culture conditions and a readout that were compatible with the study of the reduced number of cells found in the cerebrospinal fluid (CSF), the only readily available material from the CNS of live ' MS patients. We found that EBV-specific cellular and humoral immune responses were increased in the CSF of MS patients as compared with paired blood, as well as compared with the CSF of patients with other inflammatory and non-inflammatory neurological diseases. To determine whether the enhanced immune responses against EBV were specific of this virus or simply reflected an aspecific immune hyperactivation, we compared the EBV- with the cytomegalovirus (CMV)-specific immune responses. Indeed, like EBV, CMV is a neurotrophic herpesvirus that can establish latent infections, but the latter is not considered to be associated with MS. Interestingly, CSF CMV-specific immune responses were lower than blood ones and this, in all patient categories. These findings suggest that EBV reactivation may be taking place in the CNS of patients at the early stages of MS and strengthen the hypothesis that EBV may have a triggering role in this disease. Therefore, it might be interesting to explore whether an efficient anti-EBV drug or vaccine is able to prevent MS development. The reason why EBV-specific immune responses are increased in MS patients is still missing. One hypothesis might be that the immune response against EBV is qualitatively different in MS patients as compared with controls. To examine this, we assessed the cytokine mRNA profile of EBV-stimulated CD4+ and CD8+ T cells, but could not find any remarkable difference between MS patients and healthy controls. Therefore, this question remains open and fiirther studies are warranted. Reliable disease markers are lacking for MS. Here, we found that the recently described cytokine IL-26 was increased in CD8+ T cells of patients with secondary progressive MS as compared with relapsing MS, primary progressive MS, other inflammatory neurological diseases and healthy controls. Moreover, we identified brain cell types (astrocytes, oligodendrocytes and neurons) that expressed the IL-26 receptor, paring the way for further studies to understand IL-26 function and its interaction with MS.

Regulatory B cells shape the development of Th2 immune responses in BALB/c mice infected with Leishmania major through IL-10 production.

Recent evidence indicates that B cells are required for susceptibility to infection with Leishmania major in BALB/c mice. In this study, we analyzed the role of the IL-10 produced by B cells in this process. We showed that B cells purified from the spleen of BALB/c mice produced IL-10 in response to stimulation with L. major in vitro. In vivo, early IL-10 mRNA expression is detected after L. major infection in B cells from draining lymph nodes of susceptible BALB/c, but not of resistant C57BL/6 mice. Although adoptive transfer of naive wild-type B cells prior to infection in B cell-deficient BALB/c mice restored Th2 cell development and susceptibility to infection with L. major of these otherwise resistant mice, adoptive transfer of IL-10(-/-) B cells mice did not. B cells stimulated by L. major, following in vitro or in vivo encounter, express the CD1d and CD5 molecules and the IL-10 produced by these cells downregulate IL-12 production by L. major-stimulated dendritic cells. These observations indicate that IL-10 secreting B cells are phenotypically and functionally regulatory B cells. Altogether these results demonstrate that the IL-10 produced by regulatory CD1d+ CD5+ B cells in response to L. major is critical for Th2 cell development in BALB/c mice.

Activated group 3 innate lymphoid cells promote T-cell-mediated immune responses.

Group 3 innate lymphoid cells (ILC3s) have emerged as important cellular players in tissue repair and innate immunity. Whether these cells meaningfully regulate adaptive immune responses upon activation has yet to be explored. Here we show that upon IL-1β stimulation, peripheral ILC3s become activated, secrete cytokines, up-regulate surface MHC class II molecules, and express costimulatory molecules. ILC3s can take up latex beads, process protein antigen, and consequently prime CD4(+) T-cell responses in vitro. The cognate interaction of ILC3s and CD4(+) T cells leads to T-cell proliferation both in vitro and in vivo, whereas its disruption impairs specific T-cell and T-dependent B-cell responses in vivo. In addition, the ILC3-CD4(+) T-cell interaction is bidirectional and leads to the activation of ILC3s. Taken together, our data reveal a novel activation-dependent function of peripheral ILC3s in eliciting cognate CD4(+) T-cell immune responses.

The influence of environmental conditions on immune responses, morphology and recapture probability of nestling house martins (Delichon urbica)

Nestling birds produced later in the season are hypothesized to be of poor quality with a low probability of survival and recruitment. In a Spanish population of house martins (Delichon urbica), we first compared reproductive success, immune responses and morphological traits between the first and the second broods. Second, we investigated the effects of an ectoparasite treatment and breeding date on the recapture rate the following year. Due probably to a reverse situation in weather conditions during the experiment, with more rain during rearing of the first brood, nestlings reared during the second brood were in better condition and had stronger immune responses compared with nestlings from the first brood. Contrary to other findings on house martins, we found a similar recapture rate for chicks reared during the first and the second brood. Furthermore, ectoparasitic house martin bugs had no significant effect on the recapture rate. Recaptured birds had similar morphology but higher immunoglobulin levels when nestlings compared with non-recaptured birds. This result implies that a measure of immune function is a better predictor of survival than body condition per se.

Phenotype and function of protective T cell immune responses in HIV.

PURPOSE OF REVIEW: Definition of T cell immune correlates in HIV infection remains a lofty goal towards our understanding of the HIV-specific immune response. This review will focus upon recent developments and controversies in our understanding of protective T cell responses against HIV. RECENT FINDINGS: It has become clear that multiple functions and phenotypic markers of T cells must be assessed to accurately characterize the complexity of CD4 and CD8 T cell responses. While evidence indicates that a hallmark of protective immune responses in HIV infection is the presence of 'polyfunctional' T cell responses, a disconnect remains between the function and phenotype of effective HIV-specific T cells. Moreover, there may be inherent differences in the ability of specific human leukocyte antigen class I families to promote CD8 T cell effector versus polyfunctional responses. It remains to be determined how polyfunctional responses arise in HIV infection, which functions are important for control, and whether surface phenotype markers provide an indication of protective capacity. SUMMARY: Polyfunctional and phenotypic assessment of T cell responses have clearly advanced our understanding of HIV specific immune responses. Critical questions remain, however, especially whether polyfunctional T cell responses control, or are controlled by, HIV replication.

Subversion of host immune responses by viral superantigens.

Recent experiments with mouse mammary tumor virus indicate that expression of a virally encoded superantigen by B cells and its subsequent recognition by T cells are essential steps for amplification of infection and virus transmission. Preliminary results suggest that superantigens may also be expressed during retroviral infection in humans.

Immune responses to airborne fungi and non-invasive airway diseases.

Inhalation of fungal particles is a ubiquitous way of exposure to microorganisms during human life; however, this exposure may promote or exacerbate respiratory diseases only in particular exposure conditions and human genetic background. Depending on the fungal species and form, fungal particles can induce symptoms in the lung by acting as irritants, aeroallergens or pathogens causing infection. Some thermophilic species can even act in all these three ways (e.g. Aspergillus, Penicillium), mesophilic species being only involved in allergic and/or non-allergic airway diseases (e.g. Cladosporium, Alternaria, Fusarium). The goal of the present review is to present the current knowledge on the interaction between airborne fungal particles and the host immune system, to illustrate the differences of immune sensing of different fungal species and to emphasise the importance of conducting research on non-conventional mesophilic fungal species. Indeed, the diversity of fungal species we inhale and the complexity of their composition have a direct impact on fungal particle recognition and immune system decision to tolerate or respond to those particles, eventually leading to collateral damages promoting airway pathologies.

Malt1 protease inactivation efficiently dampens immune responses but causes spontaneous autoimmunity.

The protease activity of the paracaspase Malt1 has recently gained interest as a drug target for immunomodulation and the treatment of diffuse large B-cell lymphomas. To address the consequences of Malt1 protease inactivation on the immune response in vivo, we generated knock-in mice expressing a catalytically inactive C472A mutant of Malt1 that conserves its scaffold function. Like Malt1-deficient mice, knock-in mice had strong defects in the activation of lymphocytes, NK and dendritic cells, and the development of B1 and marginal zone B cells and were completely protected against the induction of autoimmune encephalomyelitis. Malt1 inactivation also protected the mice from experimental induction of colitis. However, Malt1 knock-in mice but not Malt1-deficient mice spontaneously developed signs of autoimmune gastritis that correlated with an absence of Treg cells, an accumulation of T cells with an activated phenotype and high serum levels of IgE and IgG1. Thus, removal of the enzymatic activity of Malt1 efficiently dampens the immune response, but favors autoimmunity through impaired Treg development, which could be relevant for therapeutic Malt1-targeting strategies.

Cytomegalovirus (CMV)-specific cellular immune responses.

A large percentage of healthy individuals (50-90%) is chronically infected with Cytomegalovirus (CMV). Over the past few years, several techniques were developed in order to monitor CMV-specific T-cell responses. In addition to the identification of antigen-specific T cells with peptide-loaded MHC complexes, most of the current strategies to identify CMV-specific T cells are centered on the assessment of the functions of memory T cells including their ability to mediate effector function, to proliferate or to secrete cytokines following antigen-specific stimulation. The investigation of these functions has allowed the characterization of the CMV-specific T-cell responses that are present during different phases of the infection. Furthermore, it has also been shown that the combination of virus-specific CD4 and CD8 T-cell responses are critical components of the immune response in the control of virus replication.