Healthy Aging Biomarkers: The INSPIRE's Contribution

The find solutions for optimizing healthy aging and increase health span is one of the main challenges for our society. A novel healthcare model based on integration and a shift on research and care towards the maintenance of optimal functional levels are now seen as priorities by the WHO. To address this issue, an integrative global strategy mixing longitudinal and experimental cohorts with an innovative transverse understanding of physiological functioning is missing. While the current approach to the biology of aging is mainly focused on parenchymal cells, we propose that age-related loss of function is largely determined by three elements which constitute the general ground supporting the different specific parenchyma: i.e. the stroma, the immune system and metabolism. Such strategy that is implemented in INSPIRE projects can strongly help to find a composite biomarker capable of predicting changes in capacity across the life course with thresholds signalling frailty and care dependence.

Revisiting the Hallmarks of Aging to Identify Markers of Biological Age

The Geroscience aims at a better understanding of the biological processes of aging, to prevent and/or delay the onset of chronic diseases and disability as well as to reduce the severity of these adverse clinical outcomes. Geroscience thus open up new perspectives of care to live a healthy aging, that is to say without dependency. To date, life expectancy in healthy aging is not increasing as fast as lifespan. The identification of biomarkers of aging is critical to predict adverse outcomes during aging, to implement interventions to reduce them, and to monitor the response to these interventions. In this narrative review, we gathered information about biomarkers of aging under the perspective of Geroscience. Based on the current literature, for each hallmark of biological aging, we proposed a putative biomarker of healthy aging, chosen for their association with mortality, age-related chronic diseases, frailty and/or functional loss. We also discussed how they could be validated as useful predictive biomarkers.

The INSPIRE Bio-Resource Research Platform for Healthy Aging and Geroscience: Focus on the Human Translational Research Cohort (The INSPIRE-T Cohort)

BACKGROUND

The Geroscience field focuses on the core biological mechanisms of aging, which are involved in the onset of age-related diseases, as well as declines in intrinsic capacity (IC) (body functions) leading to dependency. A better understanding on how to measure the true age of an individual or biological aging is an essential step that may lead to the definition of putative markers capable of predicting healthy aging.

OBJECTIVES

The main objective of the INStitute for Prevention healthy agIng and medicine Rejuvenative (INSPIRE) Platform initiative is to build a program for Geroscience and healthy aging research going from animal models to humans and the health care system. The specific aim of the INSPIRE human translational cohort (INSPIRE-T cohort) is to gather clinical, digital and imaging data, and perform relevant and extensive biobanking to allow basic and translational research on humans.

METHODS

The INSPIRE-T cohort consists in a population study comprising 1000 individuals in Toulouse and surrounding areas (France) of different ages (20 years or over - no upper limit for age) and functional capacity levels (from robustness to frailty, and even dependency) with follow-up over 10 years. Diversified data are collected annually in research facilities or at home according to standardized procedures. Between two annual visits, IC domains are monitored every 4-month by using the ICOPE Monitor app developed in collaboration with WHO. Once IC decline is confirmed, participants will have a clinical assessment and blood sampling to investigate markers of aging at the time IC declines are detected. Biospecimens include blood, urine, saliva, and dental plaque that are collected from all subjects at baseline and then, annually. Nasopharyngeal swabs and cutaneous surface samples are collected in a large subgroup of subjects every two years. Feces, hair bulb and skin biopsy are collected optionally at the baseline visit and will be performed again during the longitudinal follow up.

EXPECTED RESULTS

Recruitment started on October 2019 and is expected to last for two years. Bio-resources collected and explored in the INSPIRE-T cohort will be available for academic and industry partners aiming to identify robust (set of) markers of aging, age-related diseases and IC evolution that could be pharmacologically or non-pharmacologically targetable. The INSPIRE-T will also aim to develop an integrative approach to explore the use of innovative technologies and a new, function and person-centered health care pathway that will promote a healthy aging.

Towards a large-scale assessment of the relationship between biological and chronological aging: The INSPIRE Mouse Cohort

Aging is the major risk factor for the development of chronic diseases. After decades of research focused on extending lifespan, current efforts seek primarily to promote healthy aging. Recent advances suggest that biological processes linked to aging are more reliable than chronological age to account for an individual’s functional status, i.e. frail or robust. It is becoming increasingly apparent that biological aging may be detectable as a progressive loss of resilience much earlier than the appearance of clinical signs of frailty. In this context, the INSPIRE program was built to identify the mechanisms of accelerated aging and the early biological signs predicting frailty and pathological aging. To address this issue, we designed a cohort of outbred Swiss mice (1576 male and female mice) in which we will continuously monitor spontaneous and voluntary physical activity from 6 to 24 months of age under either normal or high fat/high sucrose diet. At different age points (6, 12, 18, 24 months), multiorgan functional phenotyping will be carried out to identify early signs of organ dysfunction and generate a large biological fluids/feces/organs biobank (100,000 samples). A comprehensive correlation between functional and biological phenotypes will be assessed to determine: 1) the early signs of biological aging and their relationship with chronological age; 2) the role of dietary and exercise interventions on accelerating or decelerating the rate of biological aging; and 3) novel targets for the promotion of healthy aging. All the functional and omics data, as well as the biobank generated in the framework of the INSPIRE cohort will be available to the aging scientific community. The present article describes the scientific background and the strategies employed for the design of the INSPIRE Mouse cohort.

The INSPIRE research initiative: a program for GeroScience and healthy aging research going from animal models to humans and the healthcare system

Aging is the most important risk factor for the onset of several chronic diseases and functional decline. Understanding the interplays between biological aging and the biology of diseases and functional loss as well as integrating a function-centered approach to the care pathway of older adults are crucial steps towards the elaboration of preventive strategies (both pharmacological and non-pharmacological) against the onset and severity of burdensome chronic conditions during aging. In order to tackle these two crucial challenges, ie, how both the manipulation of biological aging and the implementation of a function-centered care pathway (the Integrated Care for Older People (ICOPE) model of the World Health Organization) may contribute to the trajectories of healthy aging, a new initiative on Gerosciences was built: the INSPIRE research program. The present article describes the scientific background on which the foundations of the INSPIRE program have been constructed and provides the general lines of this initiative that involves researchers from basic and translational science, clinical gerontology, geriatrics and primary care, and public health.

[Immune tolerance and control of CNS autoimmunity: from animal models to MS patients]

INTRODUCTION

Multiple sclerosis (MS) is a chronic inflammatory disease resulting in demyelination and axonal loss within the central nervous system (CNS). An autoimmune reaction directed against CNS antigens contributes to the disease process. Since the CNS has long been considered as an immune privileged site, how such an immune response can develop locally has remained enigmatic. Recent data, mostly based on the study of animal models for MS, have shown that the CNS is in fact more permissive to the development of immune responses than previously thought. This observation is counterbalanced by the fact that immune tolerance to neural antigens can be induced outside the CNS. This review focuses on the mechanisms preventing CNS autoimmunity, which act in three separate tissues.

STATE OF THE ART

In the thymus, expression of CNS auto-antigens promotes partial protection, notably through elimination of autoreactive T cells. In the secondary lymphoid organs, the remaining autoreactive T cells are kept under control by the thymus-derived naturally occurring regulatory T cells of the CD4(+) Foxp3(+) phenotype. In the CNS, multiple mechanisms including the local activation of regulatory T cells further limit autoimmunity.

CONCLUSIONS AND PERSPECTIVES

A better understanding of the induction of regulatory T cells, of their mechanisms of action, and of approaches to manipulate them in vivo may offer new therapeutic opportunities for MS patients.

Changes in enteric neurone phenotype and intestinal functions in a transgenic mouse model of enteric glia disruption

AIMS

The influence of enteric glia on the regulation of intestinal functions is unknown. Our aim was to determine the phenotype of enteric neurones in a model of glia alterations and the putative changes in intestinal motility and permeability.

METHODS

Transgenic mice expressing haemagglutinin (HA) in glia were used. Glia disruption was induced by injection of activated HA specific CD8+ T cells. Control mice consisted of non-transgenic littermates injected with activated HA specific CD8+ T cells. Immunohistochemical staining for choline acetyltransferase (ChAT), substance P (SP), vasoactive intestinal peptide (VIP), and nitric oxide synthase (NOS) was performed on jejunal submucosal plexus (SMP) and myenteric plexus (MP). Neurally induced jejunal muscle activity was characterised in vitro. Gastrointestinal transit and paracellular permeability were measured using fluorescein isothiocyanate-dextran markers.

RESULTS

CD3 positive T cells infiltrates were observed in the MP of transgenic mice. In the SMP, the proportions of VIP and SP positive neurones decreased in transgenic mice compared with control mice. ChAT remained unchanged. In the MP, the proportions of ChAT and NOS positive neurones increased and decreased, respectively, in transgenic mice. In contrast, VIP and SP remained unchanged. Neurally mediated jejunal relaxation was lower in transgenic mice than in controls. This relaxation was reduced by NG-nitro-L-arginine methyl ester in control mice but not in transgenic mice. Gastrointestinal transit was delayed and intestinal permeability increased in transgenic mice compared with control mice.

CONCLUSION

Glia disruption induces changes in the neurochemical coding of enteric neurones, which may partly be responsible for dysfunctions in intestinal motility and permeability.

Treatment of multiple sclerosis patients with interferon-beta primes monocyte-derived macrophages for apoptotic cell death

Although interferon (IFN)-beta has shown a significant clinical benefit in multiple sclerosis (MS), its mechanism of action remains unclear. We found that IFN-beta treatment of patients with MS resulted in a significant increase in apoptotic cell death (measured by annexin V staining and nuclear fragmentation) of monocyte-derived macrophages, as compared with cells derived from patients before treatment. Stimulation of the cells with IFN-beta in vitro resulted in an even further increase of annexin V binding, as well as increased Fas (CD 95, APO-1) expression. However, no increased Fas expression, apoptotic monocytes, or monocytopenia were observed upon in vivo treatment. This indicates that IFN-beta does not deliver a death signal to monocytes but rather primes for subsequent macrophage apoptosis upon activation or differentiation.

[Contribution of biology to diagnosis of multiple sclerosis]

The analysis of the cerebrospinal fluid is the only biological test included in the diagnostic criteria for MS. A search for intrathecal IgG synthesis by isoelectrofocussing should always be performed when the cerebrospinal fluid is analyzed for a possible diagnosis of MS. Intrathecal IgG synthesis is detected in about 95 p. 100 of MS cases. However, it is not specific for MS and only signs the inflammatory nature of the nervous system lesions. In our opinion, analysis of the CSF should be proposed systematically for primary progressive MS, in most cases of monosymptomatic demyelinating syndromes, and according to the clinical context and the result of the MRI analyses in the remaining forms. To date, no prognostic criteria can be drawn from the analysis of the CSF. Other biological tests can be performed in order to eliminate other diagnosis. These tests only have a great interest in atypical forms of the disease.

HLA, molecular mimicry and multiple sclerosis

Multiple sclerosis (MS) is an inflammatory demyelinating disease of the central nervous system in which an autoimmune response most probably contributes to pathogenesis. To date, the best characterized susceptibility-associated gene has been mapped to the HLA complex. The HLA-DRB1*1501 - DRB5*0101 - DQA1*0102 - DQB1*0602 haplotype is both associated and linked to MS in different ethnic groups. The locus within the HLA class II region encoding the MS-susceptibility gene is under intensive investigation. Epidemiological studies, however, have suggested that environmental antigens also play a critical role in MS pathogenesis. One of the ways a pathogen could trigger autoimmune disease is via immunological cross-reactivity or molecular mimicry. This concept argues that a microbial peptide with certain degree of homology to a self peptide can stimulate pathogenic self-reactive specific T cells to cause an autoimmune disease. Many microbial agents have regions of sequences that may serve as binding motifs for HLA-DR2. HLA genetics and molecular mimicry may therefore be intimately interlinked in the disease process. In the present review, we focus on the HLA association with MS and the role of microbial antigens in MS, with special reference to the molecular mimicry hypothesis.

EFNS task force report: a questionnaire-based survey on the service provision and quality assurance for determination of diagnostic autoantibody tests in European neuroimmunology centres. European Federation of Neurological Societies

Autoantibodies to a wide variety of neural components are frequently sought in the sera of patients with neurological diseases suspected to have an antibody-associated autoimmune basis. Variations in assay methodology and availability are likely to exist throughout European diagnostic immunology centres, and interlaboratory discrepancies in performance for some assays have been reported. The availability of quality assurance is largely unknown. In this questionnaire-based EFNS task force, all 18 national representatives of the Neuroimmunology Panel within the EFNS were invited to estimate the service provision within their country; 12 panel members responded. From these responses, it emerged that a range of assays are being performed throughout European centres, involving over 20 separate antigens, using a broad array of immunodetection techniques. With the exception of the estimation of anti-AChR antibodies for the diagnosis of myasthenia gravis, no systematic quality assurance schemes are available, this being conducted on an ad hoc basis, or not at all. Since quality is a central component of assay sensitivity and specificity, we conclude that there is an urgent need to introduce pan-European quality assurance schemes, based on provision of positive and negative test sera from a central source, and in which all neuroimmunology laboratories should participate.

Systemic administration of agonist peptide blocks the progression of spontaneous CD8-mediated autoimmune diabetes in transgenic mice without bystander damage

Insulin-dependent diabetes is an autoimmune disease targeting pancreatic beta-islet cells. Recent data suggest that autoreactive CD8+ T cells are involved in both the early events leading to insulitis and the late destructive phase resulting in diabetes. Although therapeutic injection of protein and synthetic peptides corresponding to CD4+ T cell epitopes has been shown to prevent or block autoimmune disease in several models, down-regulation of an ongoing CD8+ T cell-mediated autoimmune response using this approach has not yet been reported. Using CL4-TCR single transgenic mice, in which most CD8+ T cells express a TCR specific for the influenza virus hemagglutinin HA512-520 peptide:Kd complex, we first show that i.v. injection of soluble HA512-520 peptide induces transient activation followed by apoptosis of Tc1-like CD8+ T cells. We next tested a similar tolerance induction strategy in (CL4-TCR x Ins-HA)F1 double transgenic mice that also express HA in the beta-islet cells and, as a result, spontaneously develop a juvenile onset and lethal diabetes. Soluble HA512-520 peptide treatment, at a time when pathogenic CD8+ T cells have already infiltrated the pancreas, very significantly prolongs survival of the double transgenic pups. In addition, we found that Ag administration eliminates CD8+ T cell infiltrates from the pancreas without histological evidence of bystander damage. Our data indicate that agonist peptide can down-regulate an autoimmune reaction mediated by CD8+ T cells in vivo and block disease progression. Thus, in addition to autoreactive CD4+ T cells, CD8+ T cells may constitute targets for Ag-specific therapy in autoimmune diseases.

Delayed and separate costimulation in vitro supports the evidence of a transient "excited" state of CD8+ T cells during activation

Although the two-signal model for T cell activation states that a signal-1 through the TCR and a costimulatory signal-2 are required for optimal stimulation, it is now clear that the requirement for costimulation can be bypassed under certain conditions. We previously reported that this is the case for naive CD8+ T cells in vitro. In the present study we tested the effect of signal-2 when delivered after signal-1 has been disrupted. Naive CD8+ T cells from TCR transgenic mice were stimulated in vitro by using immobilized recombinant single-chain MHC molecules alone as signal-1. This signal was then stopped after different lengths of time, and anti-CD28 mAb as signal-2 was given either immediately or after a time lag. We found that signal-2 can potentiate a short signal-1 when added sequentially. Moreover, a time lag between the two signals does not abolish this potentiation. If the strength of signal-1, but not its duration, is increased, then the time lag between the delivery of signals 1 and 2 can be lengthen without loss of potentiation. Together, our results indicate that the two signals do not need to be delivered concomitantly to get optimal T cell activation. We suggest that the CD8+ T cells can reach a transient "excited" state after being stimulated with signal-1 alone, characterized by the cell's ability to respond to separate and delayed signal-2.

[Role of autoimmunity in multiple sclerosis]

A number of evidences indicate that an antigen-specific immune reaction is responsible for the formation and/or the maintenance of multiple sclerosis (MS) lesions. This disease is characterized by the following: 1), an infiltration of the white matter of the brain and spinal cord by inflammatory cells; 2), the T and B lymphocytes, present in the lesions or in the cerebrospinal fluid of patients, show signs of activation; i.e., the classic IgG oligoclonal bands of the cerebrospinal fluid (activation of B lymphocytes) and the presence of activation markers on the surface of the T lymphocytes; 3), the presence of an association, and a linkage between the disease and the genes of the HLA complex. The HLA molecules are implicated in the presentation of the antigen to the T lymphocytes; 4), finally, it should be noted that the therapeutic approaches aimed at reducing (immunosuppressants) or at modulating (beta-interferon, copolymer 1) the immune responses have a positive effect on this disease, whereas those treatments which activate the immune system (gamma-interferon) have a negative effect.

Cytokines in genetic susceptibility to multiple sclerosis: a candidate gene approach. French Multiple Sclerosis Genetics Group

The immune system is involved in the pathophysiology of multiple sclerosis (MS) but the initiating antigen(s) is not yet identified. Since cytokines control both the intensity and the quality of the immune response they may be relevant candidates for the genetic susceptibility to MS. To analyze the contribution of type 1 and type 2 cytokine and cytokine receptor genes in the genetic susceptibility to MS, we have examined, in 116 French MS sibpairs, whether there is significant linkage between MS and 15 cytokine or cytokine receptor genes using 31 highly polymorphic genetic markers. The data were analyzed using the maximum likelihood score and the transmission disequilibrium approaches. None of the candidate genes tested was significantly linked to MS on the whole population. However, after stratification of the analysis on the basis of sharing (or not) of the HLA-DRB1*1501 allele, indication of linkage was found for the IL2-RB gene. These findings suggest that the IL2-RB locus contributes to the genetic susceptibility in a subgroup of MS patients.

[Environment, genetics and immunology in multiple sclerosis]

The cause of multiple sclerosis remains unknown. Epidemiological studies indicate that it is a multi-factorial disease. The environmental factors are still unknown. No virus has been yet demonstrated to play a role in multiple sclerosis. The role of HLA in the genetic susceptibility has been known since the seventies; the detailed analysis is underway. Immunological factors playing a role in the course of multiple sclerosis are better known and may serve as basis to new therapeutical approaches.

Chromosome 17q22-q24 and multiple sclerosis genetic susceptibility. American-French Multiple Sclerosis Genetic Group

Recently, genome-wide searches for multiple sclerosis (MS) susceptibility genes have suggested that the chromosome 17q22-q24 region might contain susceptibility genes in two sets of families of different ethnic backgrounds (Finnish and British). Therefore, we decided to test this region in two sets of families of different ethnic backgrounds (American and French), but collected according to the same diagnostic criteria. All lod-score values were non-significant. Moreover, we could exclude that the 17q22-24 region might contain a gene increasing the sibling recurrence risk of MS over 1.4, rendering the existence of such a gene very unlikely, at least in the group of tested families.

Localized proton magnetic resonance spectroscopy in relapsing remitting versus secondary progressive multiple sclerosis

OBJECTIVE

To determine the efficacy of MRS in discriminating between relapsing remitting (RR) and secondary progressive (SP) MS.

METHODS

MRS at long and short echo times was carried out in 104 patients with MS stratified for clinical course (RR or SP), and the results were compared with those of 15 control subjects. Normal-appearing white matter (NAWM) was studied in 55 patients, and a high-T2-signal area on MRI in 49 others.

RESULTS

At long echo times, there was a highly significant decrease in the ratios N-acetyl-aspartate/creatine (NAA/Cr) and NAA/ choline (Cho) in high-T2-signal areas and in the NAWM in patients with an SP course compared with control subjects and patients with an RR course. There was a significant negative correlation between these ratios and clinical disability measured by Expanded Disability Status Scale score, which was independent of disease duration. Discriminant values between patients with RR and SP courses were found in the NAWM (NAA/Cr = 1.75 and NAA/Cho = 1.5), but not in high-T2-signal areas. At short echo times, there was a significant increase in the ratio myoinositol/Cr in high-signal areas of patients with an SP course compared with control subjects, and the presence of abnormal resonances in the lesions and NAWM for free amino acids and lipids (in 30% and 8%, respectively) and GLX complex (glutamine, glutamate, gamma-aminobutyric acid; 16% and 20%, respectively).

CONCLUSIONS

Studying normal-appearing white matter on MRI with MRS allows discrimination between relapsing remitting and secondary progressive patients. In the NAWM of patients with MS and an SP course, severe axonal loss/dysfunction is negatively correlated to clinical disability and independent of the duration of the disease.

Encephalitis after hepatitis B vaccination: recurrent disseminated encephalitis or MS?

OBJECTIVE

To describe clinical and MRI features of patients with a disease suggestive of CNS inflammation after hepatitis B vaccination.

METHODS

Eight patients with confirmed CNS inflammation occurring less than 10 weeks after hepatitis B vaccination are described. They received follow-up clinically and on MRI for a mean period of 18 months.

RESULTS

Clinical and MRI findings were compatible with acute disseminated encephalomyelitis. However, clinical follow-up, repeated MRI, or both showed the persistence of inflammatory activity, which makes this encephalitis more suggestive of MS than of acute disseminated encephalomyelitis.

CONCLUSION

The persistent inflammatory activity observed clinically and on MRI in these patients is comparable with that usually observed in MS. Epidemiologic studies are currently testing the hypothesis of a triggering role of hepatitis B vaccination in CNS demyelination.

Frequent enrichment for CD8 T cells reactive against common herpes viruses in chronic inflammatory lesions: towards a reassessment of the physiopathological significance of T cell clonal expansions found in autoimmune inflammatory processes

We recently evidenced a dramatic enrichment for T cells reactive against Epstein-Barr virus (EBV) within inflamed joints of two rheumatoid arthritis patients. To assess the generality of this phenomenon and its relevance to autoimmunity, we studied the responses of CD8 T cells from patients with either acute or chronic inflammatory diseases (rheumatoid arthritis: n = 18, ankylosing spondylitis: n = 5, psoriatic arthritis: n = 4, Reiter's syndrome: n = 3, arthrosis: n = 2, uveitis: n = 2, multiple sclerosis: n = 2, encephalitis: n = 1) against viral proteins derived from EBV and another common herpes virus, human cytomegalovirus (CMV). T cell responses against EBV and/or CMV epitopes were frequently observed within CD8 T cells derived from chronic inflammatory lesions, irrespective of their location (knee, eye, brain) and autoimmune features. In most cases, CD8 T cells derived from affected organs yielded stronger anti-viral T cell responses than CD8 T cells derived from patients' PBL, even in chronic inflammatory diseases devoid of autoimmune features or induced by defined bacterial agents. Taken together, these results suggest that the presence of virus-specific T cells within inflamed lesions of patients suffering from autoimmune diseases is a general phenomenon associated with chronic inflammation rather than the initiating cause of the autoimmune process. Since this phenomenon was sometimes associated with long-term T repertoire biases within inflamed lesions, the physiopathological significance of T cell clonal expansions found in a recurrent fashion within chronically inflamed autoimmune lesions should be interpreted with caution.

Cell-mediated autoimmunity in paraneoplastic neurological syndromes with anti-Hu antibodies

Paraneoplastic encephalomyelitis or subacute sensory neuronopathy associated with small-cell lung cancer (SCLC) and high titers of anti-HuD antibodies, also called the "anti-Hu syndrome," is believed to result from an immune response triggered by tumor antigens and misdirected to the neurons. To further assess the issue of cell-mediated immunity in this disease, the peripheral blood lymphocyte surface phenotype was studied in 15 patients suffering from the anti-Hu syndrome (seropositive group) and in two control groups consisting of 12 seronegative SCLC patients without neurological syndrome and 15 healthy volunteers. In addition, the recombinant human HuD protein was used to stimulate in vitro peripheral blood mononuclear cells of 10 seropositive patients and of 10 patients from each control group. Phenotypic analysis of the peripheral blood lymphocytes revealed a significant increase of the memory helper (CD45RO+CD4+) T cells in the seropositive group in comparison with the two control groups. Antigen-specific proliferation of peripheral blood mononuclear cells, measured by [3H]thymidine uptake after HuD antigen stimulation, was much higher in the seropositive group than in the two control groups, and phenotypic analysis of proliferating cells revealed a significant expansion of the CD45RO subpopulation of T cells in the seropositive group. Furthermore, after HuD stimulation, a significant increase of the interferon-gamma/interleukin-4 ratio was found in culture supernatants of the seropositive group compared with seronegative SCLC patients and normal controls. Taken together, these results indicate that HuD protein is an antigenic target for autoreactive CD4+ T cells, presumably of the Th1 subtype, which could therefore be directly involved in cell-mediated injury of the nervous system as well as in antitumoral immunity.

The pathophysiology of paraneoplastic neurological syndromes

Paraneoplastic neurological diseases are a group of neurological disorders associated with neoplastic tumors but not due to tumoral extension, metabolic, infectious, vascular or toxic complications of these tumors or their treatment. In the majority of paraneoplastic neurological disorders, circulating autoantibodies directed against neurons have been found in the serum and/or the CSF suggesting, and in some cases implicating, autoimmunity in the pathophysiology of these diseases. The finding of autoimmune phenomena during the course of paraneoplastic neurological disorders is of importance: from a practical point of view, since the detection of anti-neuronal autoantibodies is of great diagnostic help and should lead to the thorough search of the associated tumor often at an early stage of its development; from a theoretical point of view, these disorders represent a peculiar type of molecular mimicry. Tumoral neontigens having structural homology or identity with neuronal autoantigens elicit autoreactivity. The immunological effector mechanisms involved in the pathophysiology of paraneoplastic syndromes appear to differ according to the disease: autoantibodies are pathogenic in Lambert-Eaton syndrome whereas, in paraneoplastic cerebellar degeneration and in the Hu syndrome, the cellular immune response might play a greater role.

Antigen-dependent and -independent Ca2+ responses triggered in T cells by dendritic cells compared with B cells

Dendritic cells (DCs) are much more potent antigen (Ag)-presenting cells than resting B cells for the activation of naive T cells. The mechanisms underlying this difference have been analyzed under conditions where ex vivo DCs or B cells presented known numbers of specific Ag-major histocompatibility complex (MHC) complexes to naive CD4(+) T cells from T cell antigen receptor (TCR) transgenic mice. Several hundred Ag-MHC complexes presented by B cells were necessary to elicit the formation of a few T-B conjugates with small contact zones, and the resulting individual T cell Ca2+ responses were all-or-none. In contrast, Ag-specific T cell Ca2+ responses can be triggered by DCs bearing an average of 30 Ag-MHC complexes per cell. Formation of T-DC conjugates is Ag-independent, but in the presence of the Ag, the surface of the contact zone increases and so does the amplitude of the T cell Ca2+ responses. These results suggest that Ag is better recognized by T cells on DCs essentially because T-DC adhesion precedes Ag recognition, whereas T-B adhesion requires Ag recognition. Surprisingly, we also recorded small Ca2+ responses in T cells interacting with unpulsed DCs. Using DCs purified from MHC class II knockout mice, we provide evidence that this signal is mostly due to MHC-TCR interactions. Such an Ag-independent, MHC-triggered calcium response could be a survival signal that DCs but not B cells are able to deliver to naive T cells.

Prevention of diabetes in NOD mice by a mutated I-Ab transgene

Susceptibility to the human autoimmune disease IDDM is strongly associated with those haplotypes of the major histocompatibility complex (MHC) carrying DQB1 alleles that do not encode aspartic acid at codon 57. Similarly, in a spontaneous animal model of this disease, the NOD mouse, the genes of the MHC play an important role in the development of diabetes. The DQB1 homolog in NOD mice, I-Ab(g7), encodes a histidine at codon 56 and a serine at codon 57, while all other known I-Ab alleles encode proline and aspartic acid, respectively, at these positions. We therefore mutated the NOD I-Ab allele to encode proline at position 56 and aspartic acid at position 57 and introduced this allele onto the NOD genetic background to study the effect of these substitutions on susceptibility to diabetes. No transgenic mice developed diabetes by 8 months of age, and transgenic mice had markedly reduced lymphocytic infiltration in the pancreas compared with nontransgenic littermates. Furthermore, splenocytes from transgenic mice failed to proliferate or secrete gamma-interferon in response to a panel of beta-cell autoantigens, although the mice did produce beta-cell specific antibodies. Interestingly, the proportion of IgG1 and IgE relative to IgG2a comprising these autoantibodies was much greater in transgenic mice compared with nontransgenic control mice. Finally, T-cells from transgenic mice inhibited the adoptive transfer of diabetes to irradiated recipients. This inhibition was partially reversed by treatment of the recipients with a combination of anti-interleukin (IL)-4 and anti-IL-10 monoclonal antibodies. Thus, a transgenic class II MHC allele encoding aspartic acid at B57 prevents diabetes, in part, by promoting the production of IL-4 and IL-10, which interfere with the effector phase of the diabetic process.

A systematic study of oligodendrocyte growth factors as candidates for genetic susceptibility to MS. French Multiple Sclerosis Genetics Group

OBJECTIVE

To test 23 genes coding for growth factors and their receptors as candidates for MS genetic susceptibility in 84 multiplex families of French origin by linkage analysis.

BACKGROUND

Epidemiologic studies have indicated that genetic susceptibility in MS exists. To identify MS susceptibility genes, association and linkage studies were performed with candidate genes suggested by the pathology of MS. The most consistent result was genetic association and linkage of MS to human leukocyte antigen (HLA) DR15. Recent advances in the knowledge of MS pathology have suggested that the oligodendrocyte, the myelin-forming cell in the CNS, and its growth factors might play a crucial role in MS.

METHODS

Fifty-two polymorphic markers within or flanking 23 candidate genes were used. Data were analyzed with the maximum likelihood score (MLS) approach. We also searched for a genetic interaction with HLA.

RESULTS

Negative results were obtained for all candidate genes. The lower limits of the relative risk (Xs) possibly excluded for any candidate gene ranged from 1.3 to 2.8. Positive MLS values (up to 0.93) were observed for transforming growth factor beta 3 (TGFbeta3) in HLA DR15-associated families, suggesting a possible role for this growth factor in interaction with HLA.

CONCLUSIONS

Oligodendrocyte growth factors do not play a significant role in MS genetic susceptibility, at least in the tested sample. TGFbeta3, the only gene highlighted by this study, deserves further analysis.

[Experimental autoimmune encephalomyelitis]

Experimental autoimmune encephalomyelitis is an induced inflammatory and demyelinating disease of the central nervous system widely used as an animal model for multiple sclerosis. New insights into its pathophysiology have been possible due to recent immunological concepts. New therapeutical approaches have been designed and tested in experimental autoimmune encephalomyelitis and are now entering the clinical setting.

Antagonistic action of IFN-beta and IFN-gamma on high affinity Fc gamma receptor expression in healthy controls and multiple sclerosis patients

Monocyte-macrophage activation by IFN-gamma is characterized by a pronounced increase of high affinity Fc receptors for IgG (Fc gamma RI), capable of triggering respiratory burst, phagocytosis, Ab-dependent cytotoxicity, and release of proinflammatory cytokines. In view of the antagonism of IFN-beta on IFN-gamma action, of interest in the chronic inflammatory disorder multiple sclerosis, we examined the possible effect of IFN-beta on IFN-gamma induction of Fc gamma RI gene expression. We found that IFN-beta significantly down-regulated IFN-gamma-induced Fc gamma RI surface expression in peripheral blood monocytes from healthy donors, in a dose- and time-dependent manner. This down-regulation of Fc gamma RI surface levels did not correspond to a decrease in Fc gamma RI mRNA, suggesting a posttranscriptional effect of IFN-beta. Down-regulation of Fc gamma RI surface expression correlated with diminished cellular signaling through Fc gamma RI, since the IFN-gamma-induced increase in Fc gamma receptor-triggered respiratory burst was nearly completely abrogated by simultaneous addition of IFN-beta. Finally, the same antagonism between both IFNs on Fc gamma RI surface expression was observed in peripheral blood monocytes derived from multiple sclerosis patients; inhibition by IFN-beta was even increased (82+/-11%), as compared with healthy controls (67+/-4%). These results may partially help explain the beneficial effect of IFN-beta in multiple sclerosis.

A viral peptide with limited homology to a self peptide can induce clinical signs of experimental autoimmune encephalomyelitis

Molecular mimicry has been suggested as a mode of autoreactive T cell stimulation in autoimmune diseases. Myelin basic protein (MBP) peptide 1-11 induces experimental autoimmune encephalomyelitis (EAE) in susceptible strains of mice. Here we show that a herpesvirus Saimiri (HVS) peptide, AAQRRPSRPFA, with a limited homology to MBP1-11 peptide, ASQKRPSQRHG (underlined letters showing homology), can stimulate a panel of MBP-11-specific T cell hybridomas and more importantly cause EAE in mice. We demonstrate that this is due to cross-recognition of these two peptides by TCRs. Results presented in this communication are the first demonstration that a viral peptide with homology at just 5 amino acids with a self peptide can induce clinical signs of EAE in mice. These findings have important implications in understanding the breakdown of T cell tolerance to self Ags in autoimmune diseases by means of cross-reactivity with unrelated peptides.

T cell receptor V beta 5 and V beta 17 clonal diversity in cerebrospinal fluid and peripheral blood lymphocytes of multiple sclerosis patients

To better characterize the cellular immune response taking place in the MS central nervous system, we investigated the blood and CSF T cell receptor (TCR) V beta 5 and V beta 17 repertoire in HLA-typed patients with recently diagnosed MS or other neurological diseases (OND). Using a RT-PCR based technique, we analysed directly ex vivo the CDR3 size of TCR beta chains utilizing V beta 5 (eight patients with MS and one with OND) or V beta 17 (eight patients with MS and six with OND) gene segments on paired blood-CSF samples. Globally, the analysis of V beta 5-J beta and V beta 17-J beta repertoire showed a less diverse pattern in the CSF samples than in the corresponding peripheral blood lymphocytes both in MS and in OND patients. However, we did not detect any recurrent clonal expansion within the V beta 5+ T cells in MS patients, underlining the potential limits of V beta 5-based immunotherapy in MS. We found an expanded T cell population using the same V beta 17-J beta 1.6 combination with identical CDR3 length in the CSF of three MS patients and none of the control patients. These results suggest selective expansion of T cells expressing this segment gene in the MS central nervous system.

Role of co-stimulation in CD8+ T cell activation

The two-signal model states that activation of naive T cells requires a signal 1 stimulus through the TCR and a co-stimulatory signal 2. By contrast, signal 1 alone is sufficient for pre-activated T cells. Recently, however, it has been shown that under certain conditions T cells can bypass the requirement for co-stimulation. For example, CD28-deficient mice, when immunized with lymphocytic choriomeningitis virus, mount a vigorous cytotoxic T lymphocyte response and clear the virus. As a continuous effort to unravel the mechanisms of T cell activation, we previously reported activation of hybridoma T cells by recombinant single-chain MHC molecules in the absence of antigen-presenting cells. In such reconstitution experiments, since the signals delivered to the T cells are well controlled, the contribution of any known or unknown signals can be ruled out. In the present study, we analyzed the requirements for activation of naive T cells by using splenocytes from TCR transgenic mice as a source of responding cells. We observed that naive CD8+ T cells are fully activated by signal 1 alone, but that co-stimulation lowers their activation threshold. Previously activated T cells are fully responsive, even when the first stimulation was performed in the absence of co-stimulation. They display a low activation threshold and are insensitive to co-stimulation. The physiological relevance of this finding and its consequences for immunotherapy as well as for our understanding of self-tolerance are discussed.

Systemic autoimmune features and multiple sclerosis: a 5-year follow-up study

OBJECTIVES

To evaluate in patients with multiple sclerosis (MS) the occurrence of clinical systemic signs and biological autoimmune abnormalities, including positive titers of antinuclear antibodies and antiphospholipid antibodies, suggestive of autoimmune diseases that may affect the central nervous system. Also, to compare the clinical and magnetic resonance imaging features and evolution of MS in patients with and without autoimmune abnormalities.

DESIGN AND PATIENTS

Prospective study of 161 patients fulfilling the criteria of having probable or definite MS hospitalized in our institution between November 1990 and June 1992.

RESULTS

Among the 161 patients, 84 (52.1%) had at least 1 clinical and/or biological general sign suggestive of an autoimmune disease; 64 were followed up for 4 to 5 years. The diagnosis of MS was confirmed in 50 patients and is still pending in 14 of them. No significant difference was found between patients with MS who were free of autoimmune features and those with autoimmune abnormalities (MS plus) concerning the age of disease onset, the presenting symptoms and signs, symptoms found on neurologic examination, and the course of the disease. For all patients with confirmed MS, general signs were found in 13.3%, positive titers of antinuclear antibodies in 26%, and positive titers of antiphospholipid antibodies in 6.2%.

CONCLUSIONS

Patients with MS with autoimmune features, including those with titers of antinuclear antibodies of 1:100 or less and/or antiphospholipid antibodies, are not different than others with MS, and therefore should not be excluded from clinical trials.

Lack of association between human leukocyte antigens and the anti-Hu syndrome in patients with small-cell lung cancer

We compared the human leukocyte antigen alleles found in a group of 17 patients with small-cell lung cancer (SCLC), paraneoplastic neurologic syndromes (PNS), and high titers of anti-Hu autoantibodies with those in 30 patients with SCLC but no PNS and no anti-Hu antibodies (control group). There was no difference between the two groups, suggesting that specific haplotypes are not required for the development of the "anti-Hu syndrome."

Imaging antigen recognition by naive CD4+ T cells: compulsory cytoskeletal alterations for the triggering of an intracellular calcium response

Antigen recognition was analyzed at the single-cell level by using for the first time T cells which were not altered by in vitro selection, transfection or immortalization. The first consequence of antigen recognition by ex vivo naive CD4+ T cells from T cell receptor (TCR)-transgenic mice is the formation of a "contact zone" with the B cell presenting the antigen. The T cell intracellular calcium (Ca2+) response begins after a delay of 30 s on average, following the formation of the contact zone. The T cell response is entirely inhibited by either protein tyrosine kinase or actin polymerization inhibitors but, surprisingly, it is insensitive to inhibitors of phosphoinositide 3-kinase. Moreover, inhibition of microtubule polymerization and use of Ca2+-free medium do not prevent the beginning of the T cell response, but do reduce the stability of the contact zone and/or the amplitude of the Ca2+ plateau. The critical involvement of the cytoskeleton in antigen recognition on B cells introduces a checkpoint in T cell activation: the initial TCR engagement triggers a Ca2+ response only after an amplification step corresponding to a cytoskeleton-controlled increase in the number of engaged TCR.

Systemic antigen in the treatment of T-cell-mediated autoimmune diseases

Systemic injection of antigen is one of the approaches that reproducibly induces effective antigen-specific hyporesponsiveness. Here, Roland Liblau and colleagues discuss the cellular and molecular bases of such tolerance, review the current use of this therapeutic strategy in experimental organ-specific autoimmune diseases and analyse what steps are necessary to make this approach suitable for clinical use.

Enrichment of antigen-specific T lymphocytes by panning on immobilized MHC-peptide complexes

Numerous studies have focused on characterizing and monitoring antigen-specific T cells during the course of an immune response. Mostly indirect methods were used to circumvent the low frequency of T cell precursors and the inherent complexity of T cell receptor (TcR)-MHC-peptide interactions. Here, we took advantage of peptide-specific adhesion induced by immobilized MHC-peptide complexes. We describe a simple technique which allows enrichment in antigen-specific T lymphocytes among a heterogeneous CD8+ T cell population. Enrichment of T cells according to their specificity should facilitate their characterization and provide an attractive tool for immunotherapy.

Experimental autoimmune encephalomyelitis in IL-4-deficient mice

Experimental autoimmune encephalomyelitis (EAE) in an inflammatory demyelinating disease which usually follows a monophasic course. Autoreactive Th1 CD4+ T cells are responsible for the lesions, whereas autoreactive Th2 CD4+ T cells can, upon adoptive transfer, suppress the disease process. However, the role of IL-4 and Th2 cells in the spontaneous remission of EAE and in the prevention of relapses is not known. We have addressed these issues using IL-4-deficient mice in which the differentiation of Th2 CD4+ T cells is severely compromised. The clinical course of actively induced EAE was compared in IL-4+/+, IL-4+ /- and IL-4-/- mice on the PL/J genetic background. No significant differences were noted between groups for the frequency, severity and duration of EAE, and the frequency of relapses. Our results indicate that IL-4, despite its well-documented regulatory role in EAE, is not necessary for the spontaneous remission of disease or for the prevention of relapses. Therefore, in the absence of IL-4, overlapping or compensatory immunoregulatory mechanisms can restrict an inflammatory response within the central nervous system.

Schwann cell transplantation and myelin repair of the CNS

Studies with experimental models of dysmyelination and demyelination have shown that rodent Schwann cells including a Schwann cell line, transplanted in the central nervous system compete with host oligodendrocytes to remyelinate denuded central axons of the spinal cord. The myelin produced by transplanted SC around these central nervous system axons is structurally normal and restores, secure nerve conduction. In the presence of a favorable substrate, transplanted Schwann cells migrate over considerable distances (several mm) and are recruited by a demyelinated lesion which they will partially repair Thus Schwann cells, which can also support axonal growth, may be instrumental in central nervous system repair. In addition, the possibility of obtaining large quantities of human and non-human primate Schwann cells, makes it possible to consider autologous Schwann cell transplantation as a potential therapy for demyelinating or traumatic diseases. The various differences which may exist between rodents and humans, however, require further investigation of this possibility in a non-human primate model of demyelination. These experiments should provide not only insights on the potential of autologous transplantation in primates but also a better understanding of the process of central remyelination.

Gene transfer to the central nervous system by transplantation of cerebral endothelial cells

A cerebral endothelial immortalized cell line was used in transplantation experiments to deliver gene products to the adult rat brain. Survival of grafted cells was observed for at least 1 year, without any sign of tumor formation. When genetically modified to express bacterial beta-galactosidase and transplanted into the striatum, these cells were shown, by light and electron microscope analysis, to integrate into the host brain parenchyma and microvasculature. Following implantation into the striatum and nucleus basalis of adult rats, endothelial cells engineered to secrete mouse beta-nerve growth factor (NGF) induced the formation of a dense network of low-affinity NGF receptor-expressing fibers near the implantation sites. This biological response was observed from 3 to 8 weeks after engraftment. The present study establishes the cerebral endothelial cell as an efficient vector for gene transfer to the central nervous system.

CD8(+) T cell-mediated spontaneous diabetes in neonatal mice

Transgenic mice that express the influenza virus hemagglutinin (HA) on pancreatic islet beta cells (ins-HA) demonstrate tolerance of HA even after immunization with influenza virus. Surprisingly, when Ins-HA mice were mated with a transgenic mouse expressing a TCR specific for an epitope of HA that is restricted by MHC class I H-2Kd (Clone-4 TCR), the resulting double transgenic (Ins-HA x Clone-4 TCR)F1 neonates developed spontaneous autoimmune diabetes immediately after birth and died within 10 days. This represents a unique situation in which all safeguards within the immune system that normally maintain tolerance of self-antigens in the neonate are insufficient.