Pan-neuronal expression of human mutant huntingtin protein in Drosophila impairs immune response of hemocytes

Huntington's disease (HD) is a late-onset; progressive, dominantly inherited neurological disorder marked by an abnormal expansion of polyglutamine (poly Q) repeats in Huntingtin (HTT) protein. The pathological effects of mutant Huntingtin (mHTT) are not restricted to the nervous system but systemic abnormalities including immune dysregulation have been evidenced in clinical and experimental settings of HD. Indeed, mHTT is ubiquitously expressed and could induce cellular toxicity by directly acting on immune cells. However, it is still unclear if selective expression of mHTT exon1 in neurons could induce immune responses and hemocytes' function. In the present study, we intended to monitor perturbations in the hemocytes' population and their physiological functions in Drosophila, caused by pan-neuronal expression of mHTT protein. A measure of hemocyte count and their physiological activities caused by pan-neuronal expression of mHTT protein highlighted the extent of immune dysregulation occurring with disease progression. We found that pan-neuronal expression of mHTT significantly alters crystal cells and plasmatocyte count in larvae and adults with disease progression. Interestingly, plasmatocytes isolated from diseased conditions exhibit a gradual decline in phagocytic activity ex vivo at progressive stages of the disease as compared to age-matched control groups. In addition, diseased flies displayed elevated reactive oxygen species (ROS) in circulating plasmatocytes at the larval stage and in sessile plasmatocytes of hematopoietic pockets at terminal stages of disease. These findings strongly implicate that neuronal expression of mHTT alone is sufficient to induce non-cell-autonomous immune dysregulation in vivo.

Levels of Interleukin-6 in Saliva, but Not Plasma, Correlate with Clinical Metrics in Huntington's Disease Patients and Healthy Control Subjects

Growing evidence suggests that inflammatory responses, in both the brain and peripheral tissues, contribute to disease pathology in Huntington's disease (HD), an inherited, progressive neurodegenerative disorder typically affecting adults in their 30-40 s. Hence, studies of inflammation-related markers in peripheral fluids might be useful to better characterize disease features. In this study, we measured levels of C-reactive protein (CRP), Interleukin-6 (IL-6), interleukin 1 beta (IL-1B), and alpha-amylase (AA) in saliva and plasma from n = 125 subjects, including n = 37 manifest HD patients, n = 36 premanifest patients, and n = 52 healthy controls, using immunoassays. We found increases in salivary levels of IL-6, IL-1B and CRP across different disease groups and increased levels of IL-6 in the plasma of HD patients as compared to premanifest patients and controls. The levels of salivary IL-6 were significantly correlated with each of the other salivary markers, as well as with IL-6 levels measured in plasma. Further, salivary IL-6 and IL-1B levels were significantly positively correlated with Total Motor Score (TMS) and chorea scores and negatively correlated with Total Functional Capacity (TFC) in HD patients, whereby in healthy control subjects, IL-6 was significantly negatively correlated with Montreal Cognitive Assessment (MoCA) and the Symbol Digit Modalities test (SDM). Interestingly, the plasma levels of IL-6 did not show similar correlations to any clinical measures in either HD or control subjects. These findings suggest that salivary IL-6 is particularly relevant as a potential non-invasive biomarker for HD symptoms. The advent of an effective, dependable salivary biomarker would meet the urgent need for a less invasive means of identifying and monitoring HD disease progression.

Biological Aging and the Cellular Pathogenesis of Huntington's Disease

Huntington's disease (HD) is a fatal, inherited neurodegenerative disorder caused by a mutation in the huntingtin gene (HTT). While mutant HTT is present ubiquitously throughout life, HD onset typically occurs in mid-life, suggesting that aging may play an active role in pathogenesis. Cellular aging is defined as the slow decline in stress resistance and accumulation of damage over time. While different cells and tissues can age at different rates, 9 hallmarks of aging have emerged to better define the cellular aging process. Strikingly, many of the hallmarks of aging are also hallmarks of HD pathology. Models of HD and HD patients possess markers of accelerated aging, and processes that decline during aging also decline at a more rapid rate in HD, further implicating the role of aging in HD pathogenesis. Furthermore, accelerating aging in HD mouse and patient-derived neurons unmasks HD-specific phenotypes, suggesting an active role for the aging process in the onset and progression of HD. Here, we review the overlap between the hallmarks of aging and HD and discuss how aging may contribute to pathogenesis in HD.

Origin of the Autophagosome Membrane in Mammals

Autophagy begins with the nucleation of phagophores, which then expand to give rise to the double-membrane autophagosomes. Autophagosomes ultimately fuse with lysosomes, where the cytosolic cargoes are degraded. Accumulation of autophagosomes is a hallmark of autophagy and neurodegenerative disorders including Alzheimer's and Huntington's disease. In recent years, the sources of autophagosome membrane have attracted a great deal of interests, even so, the membrane donors for autophagosomes are still under debate. In this review, we describe the probable sources of autophagosome membrane.

Cerebrospinal fluid sCD27 levels indicate active T cell-mediated inflammation in premanifest Huntington's disease

INTRODUCTION

Huntington's disease (HD) is a neurodegenerative disorder, but evidence also suggests neuroinflammation in the pathogenesis. The immune mechanisms involved and the timing of their activation need further clarification.

METHODS

A clinically well-characterized HD cohort and gene negative controls were enrolled. YKL-40 reflecting innate immunity and sCD27, a marker of adaptive immunity, were measured across disease stages. Comparisons were made with markers of neurodegeneration: neurofilament light (NFL), total-tau (T-tau), and phospho-tau (P-tau).

RESULTS

52 cross-sectional cerebrospinal fluid samples and 23 follow-up samples were analyzed. sCD27 was elevated in manifest HD and premanifest gene expansion carriers, whereas controls mostly had undetectable levels. YKL-40 showed a trend toward increase in manifest HD. sCD27 correlated with YKL-40 which in turn was closely associated to all included markers of neurodegeneration. YKL-40, NFL, and both forms of tau could all independently predict HD symptoms, but only NFL levels differed between groups after age-adjustment.

CONCLUSION

Increased sCD27 in premanifest HD is a sign of T cell-mediated neuroinflammation. This finding is novel since other reports almost exclusively have found early involvement of innate immunity. Validation of sCD27 in a larger HD cohort is needed. The role of adaptive immunity in HD needs further clarification, as it may hasten disease progression.

Role of thiamine in Huntington's disease pathogenesis: In vitro studies

BACKGROUND

Oxidative stress accompanies neurodegeneration and also causes abnormalities in thiaminedependent processes. These processes have been reported to be diminished in the brains of patients with several neurodegenerative diseases.

OBJECTIVES

The aim of this work was to conduct a comparative analysis of the impact of supplemented thiamine on the viability of human B lymphocytes with CAG abnormal expanded huntingtin gene (mHTT) (GM13509) and control, B lymphocytes without mHTT (GM14467) through the following studies: determination of the supplemented thiamine concentrations, which are effective for cell growth stimulation after incubation in thiamine deficit conditions; determination of cell capability to intake the exogenous thiamine; evaluation of exogenous thiamine influence on the profile of the genes related to thiamine and energy metabolism; determination of ATP synthesis and activities of thiamine-dependent enzymes, KGDHC and BCKDHC in the intact cells and upon the exogenous thiamine.

MATERIAL AND METHODS

The following methods were used: EZ4U test for cell growth analysis; HPLC for determination of thiamine intake and ATP synthesis, qRT-PCR for evaluation of the gene profiles and spectrophotometric method for KGDHC and BCKDHC activities determination.

RESULTS

Maximal cell growth stimulation was observed at 2.5 mM in GM14467 up to 135% of the control culture and at 5.0 mM in GM13509 cells up to 165% of the control culture. Native levels of total ATP and KGDHC and BCKDHC activities in both cell types were comparable and did not changed upon thiamine deficit or supplementation. GM13509 cells showed more of an increase in growth stimulation upon thiamine supplementation than GM14467 cells and this effect was reflected in the increase of intracellular thiamine concentration.

CONCLUSIONS

The above results and reported changes in expression of GAPDH, IDH1 and SLC19A3 genes observed upon thiamine deficit conditions suggest that intracellular thiamine status and energy metabolism can have a role in HD pathogenesis.

Increased irritability, anxiety, and immune reactivity in transgenic Huntington's disease monkeys

Although the most notable clinical symptoms of Huntington's disease (HD) are motor disturbances and brain atrophy, other symptoms include cognitive dysfunction, emotional and hormonal dysregulation. Emotional dysregulation (irritability, anger/aggression, and anxiety) and increased inflammation are early emerging symptoms which can be detected decades before the onset of motor symptoms in HD patients. Despite the advances in understanding the genetic causes of HD there is still no cure or preventative treatment. Thus, to better understand the pathogenesis of HD and develop effective treatments, a holistic understanding of HD is needed, as well as animal models that replicate the full spectrum of HD symptoms. The current study examined the emotional, hormonal, and gene expression responses to an acute stressor of adult male transgenic HD rhesus monkeys (n=2) as compared to wild-type controls (n=2). Results revealed that HD monkeys expressed increased anxiety and irritability/aggression as compared to controls. Reactive cortisol response to the stressor was similar between groups. However, HD monkeys exhibited increased pro-inflammatory cytokines and higher induction of immune pathway genes as compared to controls. Overall, results reveal that HD monkeys exhibit these early emerging symptoms of HD and may be an effective animal model to facilitate the development of new therapeutics for HD patients.

Mutant Huntingtin Does Not Affect the Intrinsic Phenotype of Human Huntington's Disease T Lymphocytes

Huntington’s disease is a fatal neurodegenerative condition caused by a CAG repeat expansion in the huntingtin gene. The peripheral innate immune system is dysregulated in Huntington’s disease and may contribute to its pathogenesis. However, it is not clear whether or to what extent the adaptive immune system is also involved. Here, we carry out the first comprehensive investigation of human ex vivo T lymphocytes in Huntington’s disease, focusing on the frequency of a range of T lymphocyte subsets, as well as analysis of proliferation, cytokine production and gene transcription. In contrast to the innate immune system, the intrinsic phenotype of T lymphocytes does not appear to be affected by the presence of mutant huntingtin, with Huntington’s disease T lymphocytes exhibiting no significant functional differences compared to control cells. The transcriptional profile of T lymphocytes also does not appear to be significantly affected, suggesting that peripheral immune dysfunction in Huntington’s disease is likely to be mediated primarily by the innate rather than the adaptive immune system. This study increases our understanding of the effects of Huntington’s disease on peripheral tissues, while further demonstrating the differential effects of the mutant protein on different but related cell types. Finally, this study suggests that the potential use of novel therapeutics aimed at modulating the Huntington’s disease innate immune system should not be extended to include the adaptive immune system.

Increased central microglial activation associated with peripheral cytokine levels in premanifest Huntington's disease gene carriers

Previous studies have shown activation of the immune system and altered immune response in Huntington's disease (HD) gene carriers. Here, we hypothesized that peripheral and central immune responses could be concurrent pathophysiological events and represent a global innate immune response to the toxic effects of mutant huntingtin in HD gene carriers. We sought to investigate our hypothesis using [(11)C]PK11195 PET as a translocator protein (TSPO) marker of central microglial activation, together with assessment of peripheral plasma cytokine levels in a cohort of premanifest HD gene carriers who were more than a decade from predicted symptomatic conversion. Data were also compared to those from a group of healthy controls matched for age and gender. We found significantly increased peripheral plasma IL-1β levels in premanifest HD gene carriers compared to the group of normal controls (P=0.018). Premanifest HD gene carriers had increased TSPO levels in cortical, basal ganglia and thalamic brain regions (P<0.001). Increased microglial activation in somatosensory cortex correlated with higher plasma levels of IL-1β (rs=0.87, P=0.013), IL-6 (rs=0.85, P=0.013), IL-8 (rs=0.68, P=0.045) and TNF-α (rs=0.79; P=0.013). Our findings provide first in vivo evidence for an association between peripheral and central immune responses in premanifest HD gene carriers, and provide further supporting evidence for the role of immune dysfunction in the pathogenesis of HD.

The choreography of neuroinflammation in Huntington's disease

Currently, the concept of 'neuroinflammation' includes inflammation associated with neurodegenerative diseases, in which there is little or no infiltration of blood-derived immune cells into the brain. The roles of brain-resident and peripheral immune cells in these inflammatory settings are poorly understood, and it is unclear whether neuroinflammation results from immune reaction to neuronal dysfunction/degeneration, and/or represents cell-autonomous phenotypes of dysfunctional immune cells. Here, we review recent studies examining these questions in the context of Huntington's disease (HD), where mutant Huntingtin (HTT) is expressed in both neurons and glia. Insights into the cellular and molecular mechanisms underlying neuroinflammation in HD may provide a better understanding of inflammation in more complex neurodegenerative disorders, and of the contribution of the neuroinflammatory component to neurodegenerative disease pathogenesis.

The role of the immune system in Huntington's disease

Huntington's disease (HD) is characterized by a progressive course of disease until death 15-20 years after the first symptoms occur and is caused by a mutation with expanded CAG repeats in the huntingtin (htt) protein. Mutant htt (mhtt) in the striatum is assumed to be the main reason for neurodegeneration. Knowledge about pathophysiology has rapidly improved discussing influences of excitotoxicity, mitochondrial damage, free radicals, and inflammatory mechanisms. Both innate and adaptive immune systems may play an important role in HD. Activation of microglia with expression of proinflammatory cytokines, impaired migration of macrophages, and deposition of complement factors in the striatum indicate an activation of the innate immune system. As part of the adaptive immune system, dendritic cells (DCs) prime T-cell responses secreting inflammatory mediators. In HD, DCs may contain mhtt which brings the adaptive immune system into the focus of interest. These data underline an increasing interest in the peripheral immune system for pathomechanisms of HD. It is still unclear if neuroinflammation is a reactive process or if there is an active influence on disease progression. Further understanding the influence of inflammation in HD using mouse models may open various avenues for promising therapeutic approaches aiming at slowing disease progression or forestalling onset of disease.

Intrabodies as neuroprotective therapeutics

The process of misfolding of proteins that can trigger a pathogenic cascade leading to neurodegenerative diseases largely originates intracellularly. It is possible to harness the specificity and affinity of antibodies to counteract either protein misfolding itself, or the aberrant interactions and excess stressors immediately downstream of the primary insult. This review covers the emerging field of engineering intracellular antibody fragments, intrabodies and nanobodies, in neurodegeneration. Huntington's disease has provided the clearest proof of concept for this approach. The model systems and readouts for this disorder power the studies, and the potential to intervene therapeutically at early stages in known carriers with projected ages of onset increases the chances of meaningful clinical trials. Both single-chain Fv and single-domain nanobodies have been identified against specific targets; data have allowed feedback for rational design of bifunctional constructs, as well as target validation. Intrabodies that can modulate the primary accumulating protein in Parkinson's disease, alpha-synuclein, are also reviewed, covering a range of domains and conformers. Recombinant antibody technology has become a major player in the therapeutic pipeline for cancer, infectious diseases, and autoimmunity. There is also tremendous potential for applying this powerful biotechnology to neurological diseases.

Human pluripotent stem cell therapy for Huntington's disease: technical, immunological, and safety challenges human pluripotent stem cell therapy for Huntington's disease: technical, immunological, and safety challenges

Intra-striatal transplantation of homotypic fetal tissue at the time of peak striatal neurogenesis can provide some functional benefit to patients suffering from Huntington's disease. Currently, the only approach shown to slow down the course of this condition is replacement of the neurons primarily targeted in this disorder, although it has been transient and has only worked with a limited number of patients. Otherwise, this dominantly inherited neurodegenerative disease inevitably results in the progressive decline of motricity, cognition, and behavior, and leads to death within 15 to 20 years of onset. However, fetal neural cell therapy of Huntington's disease, as with a similar approach in Parkinson's disease, is marred with both technical and biological hurdles related to the source of grafting material. This heavily restricts the number of patients who can be treated. A substitute cell source is therefore needed, but must perform at least as well as fetal neural graft in terms of brain recovery and reconstruction, while overcoming its major obstacles. Human pluripotent stem cells (embryonic in origin or induced from adult cells through genetic reprogramming) have the potential to meet those challenges. In this review, the therapeutic potential in view of 4 major issues is identified during fetal cell therapy clinical trials: 1) logistics of graft procurement, 2) quality control of the cell preparation, 3) immunogenicity of the graft, and 4) safety of the procedure.

Mapping of the epitope of monoclonal antibody 2B4 to the proline-rich region of human Huntingtin, a region critical for aggregation and toxicity

Huntington's disease is a neurodegenerative disease caused by a polyglutamine (polyQ) expansion in Huntingtin, which provokes aggregation of a proteolytic amino-terminal fragment of the affected protein encompassing the polyQ expansion. Accumulation of mutant Huntingtin somehow triggers cellular dysfunction and leads to a progressive degeneration of striatal neurons. Despite considerable efforts, the function of Huntingtin as well as the precise molecular mechanisms by which the expanded polyQ elicits cellular dysfunction remain unclear. In addition, no treatment is available to prevent, cure, or even slow down the progression of this devastating disorder. Antibodies are valuable tools to understand protein function and disease mechanisms. Here, we have identified the epitope recognized by the mAb 2B4, a broadly used antibody generated against the amino-terminal region of Huntingtin, which detects both aggregated and soluble Huntingtin. The 2B4 antibody specifically recognizes amino acids 50-64 of human Huntingtin but not the murine homologous region. Furthermore, the 2B4 epitope resides within the proline-rich region of Huntingtin, which is critical for polyQ aggregation and toxicity. These properties suggest that the 2B4 antibody might be useful in antibody-based therapeutic strategies.

Proteomic Profiling of Plasma in Huntington's Disease Reveals Neuroinflammatory Activation and Biomarker Candidates

Huntington's disease (HD) causes widespread CNS changes and systemic abnormalities including endocrine and immune dysfunction. HD biomarkers are needed to power clinical trials of potential treatments. We used multiplatform proteomic profiling to reveal plasma changes with HD progression. Proteins of interest were evaluated using immunoblotting and ELISA in plasma from 2 populations, CSF and R6/2 mice. The identified proteins demonstrate neuroinflammation in HD and warrant further investigation as possible biomarkers.

The therapeutic potential of intrabodies in neurologic disorders: focus on Huntington and Parkinson diseases

Single-chain Fv and single-domain antibodies retain the binding specificity of full-length antibodies but they can be cloned, selected, engineered, and manipulated as genes. When expressed intracellularly in mammalian cells these intracellular antibodies, or intrabodies, have the potential to alter the folding, interactions, modifications, or subcellular localization of their targets. These reagents have previously been developed as therapeutics against cancer and HIV. Since misfolded and accumulated intracellular proteins characterize several major neurodegenerative disorders, including Huntington disease (HD) and Parkinson disease, these disorders are prime candidates for intrabody therapy. In this article we review the extension of intrabody technology to the nervous system. Studies of HD have been used to develop the approach and anti-synuclein strategies are in the early stages of development. Such neurodegenerative diseases are therefore poised for engineered antibody approaches, which can provide a pipeline of novel therapeutics and new drug discovery tools.

A systematic comparison of kinetic modelling methods generating parametric maps for [(11)C]-(R)-PK11195

[(11)C]-(R)-PK11195 is presently the most widely used radiotracer for the monitoring of microglia activity in the central nervous system (CNS). Microglia, the resident immune cells of the brain, play a critical role in acute and chronic diseases of the central nervous system and in host defence against neoplasia. The purpose of this investigation was to evaluate the reliability and sensitivity of five kinetic modelling methods for the formation of parametric maps from dynamic [(11)C]-(R)-PK11195 studies. The methods we tested were the simplified reference tissue model (SRTM), basis pursuit, a simple target-to-reference ratio, the Logan plot and a wavelet based Logan plot. For the reliability assessment, the test-retest data consisted of four Alzheimer's patients that were scanned twice at approximately a six-week interval. For the sensitivity assessment, comparison of [(11)C]-(R)-PK11195 binding in Huntington's disease (HD) patients and normal subjects was performed using a group contrast to localize significant increases in mean pixel volume of distribution (VD) in HD. In all instances, a reference region kinetic extracted by a supervised clustering technique was used as input function. Reliability was assessed by use of the intra-class correlation coefficient (ICC) across a wide set of anatomical regions and it was found that the wavelet-based Logan plot, basis pursuit and SRTM gave the highest ICC values on average. The same methods produced the highest z-scores resulting from increases in mean striatal VD in HD patients compared with controls. The reference-to-target ratio and the Logan graphical approach were significantly less reliable and less sensitive.

Alloimmunisation to donor antigens and immune rejection following foetal neural grafts to the brain in patients with Huntington's disease

BACKGROUND

The brain is deemed "immunologically privileged" due to sparse professional antigen-presenting cells and lymphatic drainage, and to the blood-brain barrier. Although the actual extent of this privilege is controversial, there is general consensus about the limited need in intracerebral neural grafts for immunosuppressive regimens comparable to those used in other cases of allotransplantation. This has led over the past fifteen years to the use of either short-term or even no immunosuppression in most clinical trials with foetal neural transplant in patients with Parkinson's and Huntington's disease.

METHODOLOGY/PRINCIPAL FINDINGS

We report biological demonstration of alloimmunisation without signs of rejection in four grafted patients out of 13 studied during the course of a clinical trial involving fetal neural transplantation in patients with Huntington's Disease. Biological, radiological and clinical demonstration of an ongoing rejection process was observed in a fifth transplanted patient. The rejection process was, however, fully reversible under immunosuppressive treatment and graft activity recovered within six months.

CONCLUSIONS/SIGNIFICANCE

There had been, up to date, no report of documented cases that could have cast a doubt on those procedures. Our results underline the need for a reconsideration of the extent of the so-called immune privilege of the brain and of the follow-up protocols of patients with intracerebral grafts. It also suggests that some of the results obtained in past studies with foetal neural transplants may have been biased by an unrecognized immune response to donor cells.

Imaging microglial activation in Huntington's disease

Activated microglia have been proposed to play a major role in the pathogenesis of Huntington's Disease (HD). PK11195 is a ligand which binds selectively to peripheral benzodiazepine binding sites, a type of receptor selectively expressed by activated microglia in the central nervous system. Using (11)C-(R)-PK11195 positron emission tomography (PET), we have recently shown in vivo evidence of increased microglial activation in both symptomatic and presymptomatic HD gene carriers and that the degree of microglial activation in the striatum correlates with the severity of striatal dopamine D2 receptor dysfunction measured with (11)C-raclopride PET. Our findings indicate that microglial activation is an early process in the HD pathology, occurring before the onset of symptoms. The close spatial and temporal relationship between microglial activation and neuronal dysfunction lends further support to the pathogenic link between the two processes in HD. Further longitudinal studies are needed to fully elucidate this link.

Intrabody applications in neurological disorders: progress and future prospects

Single-chain Fv and single-domain antibodies retain the binding specificity of full-length antibodies, but they can be expressed as single genes in phage or yeast surface-display libraries, thus allowing efficient in vitro selection from a naive human repertoire. Selected genes can then be expressed intracellularly in mammalian cells as intrabodies, with the potential for alteration of the folding, interactions, modifications, or subcellular localization of their targets. These reagents have been developed as therapeutics against cancer and HIV. Since misfolded and accumulated intracellular proteins characterize a wide range of neurodegenerative disorders, they are also potentially useful intrabody targets. Here, we review the extension of intrabody technology to the nervous system, in which studies of Huntington's disease have been used to develop the approach, and anti-synuclein and -beta-amyloid strategies are in the early stages of development. Research on several other neurodegenerations, including Parkinson's, Alzheimer's, and prion diseases, provides support for the development of intrabodies directed against specific targets, or possibly against more common downstream targets, as novel therapeutics and as drug discovery tools.

HIV encephalitis simulating Huntington's disease

Complications from human immunodeficiency virus (HIV)/acquired immune deficiency syndrome are notorious for mimicking other neurological diseases. We describe a case of HIV encephalitis presenting with the classic clinical features of Huntington's Disease in a woman without known HIV risk factors or other clinical stigmata suggestive of immunosuppression. This case reminds us that HIV should be part of the differential diagnosis in unexplainable neurological diseases.

Suppression of Huntington's disease pathology in Drosophila by human single-chain Fv antibodies

Misfolded neuronal proteins have been identified in a number of neurodegenerative disorders and have been implicated in the pathogenesis of diseases that include Alzheimer's disease, Parkinson's disease, prion-based dementia, Huntington's disease (HD), and other polyglutamine diseases. Although underlying mechanisms remain the subject of ongoing research, it is clear that aberrant processing, protein degradation, and aggregate formation or spurious protein association of the abnormal neuronal proteins may be critical factors in disease progression. Recent work in these diseases has demonstrated in vitro that specific engineered antibody species, peptides, or other general agents may suppress the formation of aggregates. We have modified an approach with intracellularly expressed single-chain Fv (sFv) antibodies (intrabodies) that bind with unique HD protein epitopes. In cell and tissue culture models of HD, anti-N-terminal huntingtin intrabodies (C4 sFv) reduce aggregation and cellular toxicity. Here, we present the crucial experiment of intrabody-mediated in vivo suppression of neuropathology, using a Drosophila model of HD. In the presence of the C4 sFv intrabody, the proportion of HD flies surviving to adulthood increases from 23% to 100%, and the mean and maximum lifespan of adult HD flies is significantly prolonged. Neurodegeneration and formation of visible huntingtin aggregates are slowed. We conclude from this investigation that engineered intrabodies are a potential new class of therapeutic agents for the treatment of neurodegenerative diseases. They may also serve as tools for drug discovery and validation of sites on mutant neuronal proteins that could be exploited for rational drug design.

Autophagosome-like vacuole formation in Huntington's disease lymphoblasts

In an effort to clarify cellular abnormalities in Huntington's disease without the confounding factor of gross degeneration and postmortem alterations associated with studies of the brain, we have examined HD patient lymphoblasts. We report pronounced vacuole formation in patients. The vacuoles possess huntingtin remnants and cathepsin B staining, a lysosomal marker, suggesting autophagy. The number and size of vacuoles parallel the number of polyglutamine repeats in patients. Treatment with staurosporine, which augments apoptosis, leads to increased vacuole formation in Huntington's disease cells but does not influence control cells. Our findings provide direct evidence for abnormalities in Huntington's disease tissues outside the brain under basal conditions. Autophagic cellular alterations may be utilized as peripheral markers of Huntington's disease pathology.

Antigliadin antibodies in Huntington's disease

The relevance of gluten sensitivity in sporadic and hereditary ataxia pathogenesis is unclear. The authors found high antigliadin antibody titers in 23 of 52 (44%) patients with Huntington's disease (HD), suggesting a previously unrecognized association between HD and gluten sensitivity. The results further question "gluten ataxia" as a distinct disease entity and raise the possibility that antigliadin antibodies in ataxia and other neurodegenerative diseases may be an epiphenomenon, the mechanisms of which remain to be investigated.

Huntington's disease transgenic mice are resistant to global cerebral ischemia

Excitotoxicity plays a key role in ischemic neuronal death and is also one of the candidate mechanisms contributing to neurodegeneration in Huntington's disease (HD). Unexpectedly we have now found that transgenic mice expressing exon 1 of a mutant human HD gene (R6/1) are protected against global cerebral ischemia (GCI), installed by temporary bilateral occlusion of the carotid arteries. Whereas wild type mice showed a substantial neuronal damage in the hippocampus following 15, 20 and 60 min of GCI, transgenic mice were partially protected after 15 and 20 minutes of hypoxemia. This tolerance to ischemia is not blocked by pretreatment of mice with cycloheximide, an unspecific protein synthesis inhibitor. We conclude that this form of tolerance to ischemia in HD transgenic mice--although somewhat reminiscent of ischemic tolerance after ischemic preconditioning--is therefore independent of short term expression of endogenous neuroprotective proteins.

Geldanamycin activates a heat shock response and inhibits huntingtin aggregation in a cell culture model of Huntington's disease

Huntington's disease (HD) is a progressive neurodegenerative disorder with no effective treatment. Geldanamycin is a benzoquinone ansamycin that binds to the heat shock protein Hsp90 and activates a heat shock response in mammalian cells. In this study, we show by using a filter retardation assay and immunofluorescence microscopy that treatment of mammalian cells with geldanamycin at nanomolar concentrations induces the expression of Hsp40, Hsp70 and Hsp90 and inhibits HD exon 1 protein aggregation in a dose-dependent manner. Similar results were obtained by overexpression of Hsp70 and Hsp40 in a separate cell culture model of HD. This is the first demonstration that huntingtin protein aggregation in cells can be suppressed by chemical compounds activating a specific heat shock response. These findings may provide the basis for the development of a novel pharmacotherapy for HD and related glutamine repeat disorders.

Transplanted fetal striatum in Huntington's disease: phenotypic development and lack of pathology

Neural and stem cell transplantation is emerging as a potential treatment for neurodegenerative diseases. Transplantation of specific committed neuroblasts (fetal neurons) to the adult brain provides such scientific exploration of these new potential therapies. Huntington's disease (HD) is a fatal, incurable autosomal dominant (CAG repeat expansion of huntingtin protein) neurodegenerative disorder with primary neuronal pathology within the caudate-putamen (striatum). In a clinical trial of human fetal striatal tissue transplantation, one patient died 18 months after transplantation from cardiovascular disease, and postmortem histological analysis demonstrated surviving transplanted cells with typical morphology of the developing striatum. Selective markers of both striatal projection and interneurons such as dopamine and c-AMP-related phosphoprotein, calretinin, acetylcholinesterase, choline acetyltransferase, tyrosine hydroxylase, calbindin, enkephalin, and substance P showed positive transplant regions clearly innervated by host tyrosine hydroxylase fibers. There was no histological evidence of immune rejection including microglia and macrophages. Notably, neuronal protein aggregates of mutated huntingtin, which is typical HD neuropathology, were not found within the transplanted fetal tissue. Thus, although there is a genetically predetermined process causing neuronal death within the HD striatum, implanted fetal neural cells lacking the mutant HD gene may be able to replace damaged host neurons and reconstitute damaged neuronal connections. This study demonstrates that grafts derived from human fetal striatal tissue can survive, develop, and are unaffected by the disease process, at least for 18 months, after transplantation into a patient with HD.

Degradation of tryptophan in neurodegenerative disorders

In patients with neurodegenerative disorders, namely Alzheimer's disease and Huntington's disease, we compared serum concentrations of tryptophan, kynurenine and the kynurenine per tryptophan ratio with concentrations of soluble immune activation markers. Significantly lower tryptophan concentrations were observed in the patients, and lower tryptophan levels as well as higher kynurenine levels and higher kynurenine per tryptophan ratios correlated with higher concentrations of neopterin, and soluble receptors for TNF and interleukin-2. In both groups of patients tryptophan concentrations correlated inversely with the degree of mental retardation. No such association existed for the duration of the disease. The data show that systemic chronic immune activation in patients with Alzheimer's disease and Huntington's disease is associated with significant degradation of tryptophan, which is most likely due to activation of indoleamine (2,3)-dioxygenase by immunologic stimuli. Further studies will be necessary to investigate a potential role of tryptophan degradation in the pathogenesis of neurodegenerative disorders.

Increased complement biosynthesis by microglia and complement activation on neurons in Huntington's disease

In this study complement activation and biosynthesis have been analysed in the brains of Huntington's disease (HD) (n = 9) and normal (n = 3) individuals. In HD striatum, neurons, myelin and astrocytes were strongly stained with antibodies to C1q, C4, C3, iC3b-neoepitope and C9-neoepitope. In contrast, no staining for complement components was found in the normal striatum. Marked astrogliosis and microgliosis were observed in all HD caudate and the internal capsule samples but not in normal brain. RT-PCR analysis and in-situ hybridisation were carried out to determine whether complement was synthesised locally by activated glial cells. By RT-PCR, we found that complement activators of the classical pathway C1q C chain, C1r, C4, C3, as well as the complement regulators, C1 inhibitor, clusterin, MCP, DAF, CD59, were all expressed constitutively and at much higher level in HD brains compared to normal brain. Complement anaphylatoxin receptor mRNAs (C5a receptor and C3a receptor) were strongly expressed in HD caudate. In general, we found that the level of complement mRNA in normal control brains was from 2 to 5 fold lower compared to HD striatum. Using in-situ hybridisation, we confirmed that C3 mRNA and C9 mRNA were expressed by reactive microglia in HD internal capsule. We propose that complement produced locally by reactive microglia is activated on the membranes of neurons, contributing to neuronal necrosis but also to proinflammatory activities. Complement opsonins (iC3b) and anaphylatoxins (C3a, C5a) may be involved in the recruitment and stimulation of glial cells and phagocytes bearing specific complement receptors.

Activated immune system in patients with Huntington's disease

Abnormalities of immune system compartments were determined in 12 patients with Huntington's disease (eight males, four females; age 42.4+/-11.7 years) and 11 controls (7 males, 4 females; age 47.0+/-12.0). All patients were free from infectious diseases. Serum concentrations of a panel of serum soluble markers of immune activation were investigated, namely neopterin, 55-kDa-type soluble tumor necrosis factor receptor (sTNF-R), interleukin-2-receptor (sIL-2R), kynurenine, tryptophan, immunoglobulins (Ig) A, M and G as well as routine laboratory tests. Compared to controls, we found significantly higher serum levels of IgA (p<0.01), sTNF-R, sIL-2R, neopterin, and complement component C3 (all p<0.05), and serum tryptophan was decreased (p<0.001). Higher concentrations of circulating immune complexes, cardiolipin antibodies, IgM, neopterin and lower tryptophan were associated with loss of cognitive function as assessed by the mini-mental-test. Five patients died within 1 year after measurements were performed. In these patients IgM, circulating immune complexes and neopterin concentrations were higher compared to survivors and serum tryptophan was lower. The data indicate an activation of various immune system compartments in Huntington's disease and that systemic immunological alterations might be important in the course of the disease.

Neuronal cell transplantation for Parkinson's and Huntington's diseases

The brain constitutes a privileged transplantation site. Under appropriate conditions neuronal tissues can survive transplantation into the damaged brain, integrate with the host, and alleviate functional impairments associated with neurological disease. The experimental techniques have been developed to the point of clinical application with demonstrable benefit in Parkinson's disease, and similar applications in Huntington's disease appear to be imminent. Nevertheless, present techniques require use of embryonic/fetal tissues which will limit the availability of donors for the foreseeable future. There is an active search for alternative sources of tissue that are equally effective but more readily available, including engineered cells, expanded stem/precursor cells, and xenografts.

Polyglutamine expansion as a pathological epitope in Huntington's disease and four dominant cerebellar ataxias

A polyglutamine expansion (encoded by a CAG repeat) in specific proteins causes neurodegeneration in Huntington's disease (HD) and four other disorders, by an unknown mechanism thought to involve gain of function or toxicity of the mutated protein. The pathological threshold is 37-40 glutamines in three of these diseases, whereas the corresponding normal proteins contain polymorphic repeats of up to about 35 glutamines. The age of onset of clinical manifestations is inversely correlated to the length of the polyglutamine expansion. Here we report the characterization of a monoclonal antibody that selectively recognizes polyglutamine expansion in the proteins implicated in HD and in spinocerebellar ataxia (SCA) 1 and 3. The intensity of signal depends on the length of the polyglutamine expansion, and the antibody also detects specific pathological proteins expected to contain such expansion, in SCA2 and in autosomal dominant cerebellar ataxia with retinal degeneration, whose genes have not yet been identified.

SMI-32 antibody against non-phosphorylated neurofilaments identifies a subpopulation of cultured cortical neurons hypersensitive to kainate toxicity

SMI-32, an antibody against a non-phosphorylated neurofilament epitope identifies a subpopulation of human cortical neurons preferentially lost in Alzheimer's or Huntington's disease. In murine cortical cultures SMI-32 labeled a small subset of neurons exhibiting enhanced vulnerability to kainate toxicity. Most SMI-32(+) neurons were GABAergic and exhibited kainate-activated Co2+ uptake. Thus expression of Ca2+ permeable AMPA or kainate receptor-gated channels likely underlies the heightened vulnerability of SMI-32(+) cortical neurons to kainate.

Effects of striatal excitotoxicity on huntingtin-like immunoreactivity

The relationship between the specific neuronal loss observed in Huntington's disease and the mutation in the IT15 gene responsible for this disease remains obscure. Using an antipeptide antibody against amino acids 3114-3141 of the human huntington protein, we demonstrate that striatal injection of quinolinic acid in mice induces increased immunoreactivity for huntington in some remaining neurons but not in glial cells. This increase is apparent in both neuronal cell bodies and in cell processes in the white matter six hours after excitotoxic challenge. This finding suggests that huntington may be involved in the response to excitotoxic stress in these neurons.

Normal and expanded Huntington's disease gene alleles produce distinguishable proteins due to translation across the CAG repeat

BACKGROUND

An expanded CAG trinucleotide repeat is the genetic trigger of neuronal degeneration in Huntington's disease (HD), but its mode of action has yet to be discovered. The sequence of the HD gene places the CAG repeat near the 5' end in a region where it may be translated as a variable polyglutamine segment in the protein product, huntingtin.

MATERIALS AND METHODS

Antisera directed at amino acid stretches predicted by the DNA sequence upstream and downstream of the CAG repeat were used in Western blot and immunohistochemical analyses to examine huntingtin expression from the normal and the HD allele in lymphoblastoid cells and postmortem brain tissue.

RESULTS

CAG repeat segments of both normal and expanded HD alleles are indeed translated, as part of a discrete approximately 350-kD protein that is found primarily in the cytosol. The difference in the length of the N-terminal polyglutamine segment is sufficient to distinguish normal and HD huntingtin in a Western blot assay.

CONCLUSIONS

The HD mutation does not eliminate expression of the HD gene but instead produces an altered protein with an expanded polyglutamine stretch near the N terminus. Thus, HD pathogenesis is probably triggered by an effect at the level of huntingtin protein.

Evidence for a preferential loss of enkephalin immunoreactivity in the external globus pallidus in low grade Huntington's disease using high resolution image analysis

Previous studies have shown that in advanced cases of Huntington's disease, enkephalin-immunoreactive striatal projections to the external globus pallidus may be more affected than substance P-containing striatal projections to the inner segment of the pallidum [Reiner A. et al. (1988) Proc. natn. Acad. Sci. U.S.A. 85, 5733-5737]. Other immunohistochemical [Ferrante R. J. et al. (1990) Soc. Neurosci. Abstr. 16, 1120] and neurochemical observations [Storey E. and Beal M.F. (1993) Brain 116, 1201-1222] suggest no difference in the loss of these peptide-containing pathways in Huntington's disease. In view of the potential significance of this issue for understanding the neuropathological process in Huntington's disease, we examined the globus pallidus in control and Huntington's disease brains, using a quantitative approach which involved high resolution image analysis of 7 microns frozen sections to determine the overall density of peptide-immunoreactive terminals. Results showed that in the controls there was no significant difference between the density of enkephalin- and substance P-immunoreactive terminals in the external and internal globus pallidus, respectively. In all Huntington's disease brains, including grade 1 cases, enkephalin-immunoreactive terminals in the external globus pallidus were significantly reduced compared to substance P-positive boutons in the internal segment of the adjacent section. In comparison to controls, enkephalin immunoreactivity in all Huntington's disease cases was significantly lower; substance P-immunoreactive terminals in the internal globus pallidus were significantly lower than controls in some of the grade 2 cases and in the grade 3 cases.(ABSTRACT TRUNCATED AT 250 WORDS)

Brain extracts containing a Huntington disease antigen inhibit [3H]kainate binding and block synaptosomal amino acid transport

Fractions isolated from mammalian brain which had previously been shown to inhibit the rate of migration of peripheral blood leukocytes taken from Huntington disease cases, and also to inhibit [3H]kainic acid binding, were characterized further. By use of repeated ultrafiltration onto a 1000D MW cutoff filter, and by the isolation and extensive washing of an enriched ammonium sulfate fraction, their activity was shown not to be due to the presence of endogenous glutamate, and to be relatively selective for brain glutamate receptor binding sites. Inhibitory activity at [3H]GABA, 5-[3H]hydroxytryptamine 5HT1 and dopamine D1 or D2 binding sites was much weaker or absent. Factor extracts were also shown to act as non-competitive inhibitors of synaptosomal amino acid transport: increasing concentrations of the factor had no significant effect on the KM for the uptake of either [3H]glutamate or [3H]GABA, but at a final concentration of 66 micrograms protein x ml-1 had reduced the VMAX for [3H]glutamate uptake to approximately 20% of control, and the VMAX for [3H]GABA uptake to approximately 40% of control. This may enhance the factor's potential excitotoxicity.

Expression of the CD15 epitope in the human magnocellular basal forebrain system

The distribution of the carbohydrate epitope 3-fucosyl-N-acetyl-lactosamine (CD15) has been immunocytochemically evaluated in coronal paraffin sections through the magnocellular basal forebrain system--the nucleus basalis of Meynert, the nucleus of the diagonal band of Broca and the medial septal nucleus--of 202 human brains. The brains derived from differently aged controls (n = 54) and from patients suffering from organic brain diseases (n = 129) or psychiatric disorders (n = 19). In 30 cases dementia was clinically diagnosed. CD15 first appeared around birth when it became localized on singular astrocytes. The astrocyte number and process density steadily increased, and at approximately 12 years the typical adult-type pattern was acquired. Considerable variations in the expression patterns were noted with regard to the astrocyte number, the intensity in immunostaining and the process relations of CD15-positive astrocytes with the magnocellular neurons. In the light of these variations, and of conflicting additional changes in other areas of most diseased brains, it was difficult to correlate different intensities and patterns to specific diseases. The results, however, provide evidence for an increase in CD15 expression and in process network density of astrocytes in the lateral part of the nucleus basalis of Meynert in cases of Huntington's disease.

Two-site enzyme immunoassay for beta NGF applied to human patient sera

Nerve growth factor (NGF) supports sympathetic and sensory neurons in the peripheral nervous system and serves functions in the development and maintenance of cholinergic neurons in the basal forebrain. NGF distribution can be studied with the use of a sensitive two-site enzyme immunoassay (EIA). The monoclonal antibody 27/21 to mouse NGF was recently shown to effectively block the activity of both recombinant human NGF and native mouse NGF, and a two-site EIA using monoclonal antibody 27/21 was optimized. We have now applied this assay to examine NGF levels in normal human serum and serum from Parkinson, Alzheimer, and Huntington patients. To further test the specificity of conjugate binding, dilutions of the human sera were preincubated with an excess of monoclonal NGF antibody 27/21 in solution. With this strategy it was possible to completely block the signal obtained using the two-site EIA. Furthermore, we show that recombinant BDNF and NT-3 do not cross-react with monoclonal antibody 27/21 under our conditions. We found low levels of specific NGF immunoreactivity in normal human sera (0.4 +/- 0.1 ng/ml). Significantly lower levels of NGF were found in sera from patients with Parkinson's and Huntington's disease whereas sera from Alzheimer patients showed only slight reductions in the NGF level. Two patients who had received intracerebral NGF infusions (one with Parkinson's and other with Alzheimer's disease) showed significantly elevated serum levels of NGF during the period of infusion. Due to an inhibitory activity in human serum, it was impossible to demonstrate the low levels of NGF activity in the human serum samples using explanted embryonic sympathetic ganglia, even after concentration by pressure dialysis. Thus, the serum levels are below the limit to evoke a response in NGF-sensitive neurons and thus to expect any physiological effect. Nevertheless, the levels measured may be used as indicators in clinical conditions such as Parkinson's and Huntington's disease.

Oligoclonal free kappa and lambda bands in the cerebrospinal fluid of patients with multiple sclerosis and other neurological diseases. An immunoaffinity-mediated capillary blot study

We describe an affinity-mediated capillary blotting technique for the detection of free kappa or lambda light chains in native cerebrospinal fluid (CSF) after isoelectric focusing in agarose gel. Interferences by light chains bound to immunoglobulins were carefully excluded. An absolute amount of 20-50 ng of free kappa or lambda Bence-Jones proteins were detectable by this method, under the form of several discrete bands with isoelectric points between 5 and 8.5. No free light chains were observed in CSF and sera from patients without neurological disorders (n = 26). Such bands were present in most CSF samples in the case of central nervous system (CNS) infections, except in aseptic meningitis. In a group of 48 multiple sclerosis (MS) patients, 44 (92%) displayed oligoclonal free kappa bands restricted to the CSF; oligoclonal IgG bands were observed in 40 cases, and oligoclonal free lambda bands in 33. In this group, the presence of CSF free light chain bands was highly correlated with their absolute levels (p less than 0.001). In other neurological diseases (n = 44), oligoclonal free kappa and free lambda bands were detected much more rarely, in seven (16%) and four (9%) cases respectively. Surprisingly, the CSF from three unrelated patients with Huntington's disease (out of five tested) contained both oligoclonal IgG and free kappa bands.

Immunological status in Huntington's disease

The immunological status of patients with Huntington's disease was studied and compared with that of an age-matched control group. No remarkable abnormalities in lymphocyte subpopulations were observed. The percentage of B cells, CD4+, CD8+, DR+ cells and stimulated cells bearing Tac receptors remained unchanged. The proliferative response to mitogens and the production of interleukin-1 (Il-1) were decreased, whereas the IgG level was increased. It is possible that changes in the levels of neurotransmitters affect the immunological function in basal ganglia disease.

Neural grafting in a rat model of Huntington's disease: striosomal-like organization of striatal grafts as revealed by acetylcholinesterase histochemistry, immunocytochemistry and receptor autoradiography

Grafts of fetal striatum were implanted in the form of a cell suspension into the brains of rats with prior ibotenic acid lesions of the caudate-putamen. The grafts were placed in three different sites: the lesioned caudate-putamen, or the denervated (but otherwise undamaged) globus pallidus and substantia nigra. After 3-6 months survival the grafts were investigated by means of immunohistochemistry and receptor autoradiography in combination with routine histology and acetylcholinesterase histochemistry. The grafts placed within the lesioned caudate-putamen were at least 10-fold larger larger than those placed in the substantia nigra region, with the grafts placed in the globus pallidus being of intermediate size. In all locations the acetylcholinesterase staining had an uneven, patchy distribution, which was most pronounced in the grafts located within the caudate-putamen. These patches did not bear any obvious relationship to variations in density of the neuronal perikarya within the grafted tissue. Many of the neuropeptide-immunoreactive neuron types present in the normal striatum, such as those containing substance P, [Met]enkephalin, somatostatin, cholecystokinin and neuropeptide Y were also detected in the grafted striatum along with acetylcholinesterase-positive staining. Acetylcholinesterase-positive, [Met]enkephalin-positive, substance P-positive and tyrosine hydroxylase-positive markers all showed uneven, patchy distributions in the grafts. This was also the case for the distribution of dopamine D2 and opiate receptors (as revealed by [3H]spiroperidol and [3H]diprenorphine autoradiography, respectively), whereas muscarinic receptor binding was even throughout the grafts. As is the case in the so-called striosomal patches (neurochemically defined compartments) in the immature intact striatum during the early postnatal period, patches of high acetylcholinesterase staining in the grafts showed partial correspondence with patches of high [Met]enkephalin fibre staining, and dopamine receptor density, and (although to a lesser degree) also with patches of high opiate receptor density and high substance P-immunoreactivity. This correspondence of patches also occurred between tyrosine hydroxylase fibre staining and acetylcholinesterase staining as revealed by grafts placed into the substantia nigra. These results suggest that the fetal striatal cell suspension grafts will give rise to a fairly normal range of striatal neuron and receptor types and that they develop at least some of the striosomal features characteristic for the normal striatum.(ABSTRACT TRUNCATED AT 400 WORDS)

Elevated levels of a glycoprotein antigen (P-80) in gray and white matter of brain from victims of multiple sclerosis

The levels of a glycoprotein reactive with monoclonal antibody (MAb) 44D10 in white and gray matter from brains of victims of several neurological diseases, including Multiple Sclerosis, Alzheimer's, Parkinson's and Huntington's diseases, were compared to that of normal individuals. The concentration of antigen reactive with MAb 44D10 was elevated in both gray and white matter of all MS brains examined, but not in brains with other neurological diseases. The increase in the concentration of antigen varied amongst the MS brains, such that the levels of antigen were only slightly increased in 2 of the 6 MS brains whereas 2 to 4 fold higher levels were found in the other 4 brains. Increased levels of antigen were detected in gray matter of MS brains, whereas this antigen was either not detected or present in very low levels in gray matter homogenates prepared from age-matched normal brains. MAb Leu 1, which reacts with T lymphocytes, was not absorbed by normal and MS brain tissue suggesting the increase in antigen reactive with MAb 44D10 in MS brain homogenates was not associated with non-specific infiltration by T lymphocytes. Comparison of the purified antigen from MS gray matter and normal white matter by gel electrophoresis demonstrated that MAb 44D10 was reacting with a similar protein in both tissues with an apparent molecular weight of 80K. We have named this molecule P-80 glycoprotein.

Material prepared from normal brain inhibits migration of leukocytes from Huntington's disease patients

Material inhibiting migration of leukocytes in vitro from Huntington's disease patients, was obtained from human brain removed at autopsy. The active material was present in brainstem, basal ganglia and cerebellum but not in cerebral cortex. It could be recovered at autopsy up to 21.5 h after death, but not from patients who had died following prolonged anoxia. It was susceptible to heating and to freezing and thawing. Its activity was preserved in acid medium to pH 3, and its iso-electric point was around pH 5. Activity was present in the fraction eluted from gel filtration with molecular weight of 1.9 X 10(5). Protein, carbohydrate, lipid and nucleic acid could be identified in the active material, and its activity depended on intact protein and carbohydrate moieties. Sialic acid, although present, did not contribute to antigenicity. Extraction with lipid solvents abolished activity.

Evidence of T-lymphocyte functional impairment in Huntington's disease

Huntington's Disease (HD) is a degenerative neurological disorder with autosomal dominant transmission. Although immunological defect(s) have been postulated, no confirmed laboratory evidence for this exists. In the present study we observed activated T cells in the peripheral blood of HD patients (using 4F2 monoclonal antibody), whereas the percentage of T cells bearing T-cell activation markers such as HLA-DR and MLR4 antigens was normal. We then studied T cells of HD patients in some functional assays. Since it has been suggested that autologous mixed lymphocyte reaction (AMLR) includes several immune mechanisms in which distinct cell subsets interact and perform distinct regulatory functions, it is conceivable that the remarkable deficiency of AMLR herein observed in HD patients results from some abnormal immune regulation which may contribute to the pathology of this condition. Additional experiments demonstrated a defect of AMLR in three asymptomatic young sibs of HD patients, and coculture experiments between T cells of patients (as responders) and non-T cells of their sibs (as stimulators), and vice versa, produced no proliferative response. Subnormal responsiveness in allogeneic MLR was also observed. Normal or enhanced PHA-induced production of both IL-2 and IFN-gamma in vitro was detected. These experimental data suggest a cellular branch of the immune system in HD; however, they do not indicate if this defect is primary or secondary to the disease itself.