Dysregulated Lipid Metabolism Networks Modulate T-cell Function in People with Relapsing Remitting Multiple Sclerosis.

Altered cholesterol, oxysterol, sphingolipid, and fatty acid concentrations are reported in blood, cerebrospinal fluid, and brain tissue of people with relapsing remitting multiple sclerosis (RRMS) and are linked to disease progression and treatment responses. CD4+ T cells are pathogenic in RRMS, and defective T cell function could be mediated in part by liver X receptors (LXRs) - nuclear receptors that regulate lipid homeostasis and immunity. RNA-sequencing and pathway analysis identified that genes within the 'lipid metabolism' and 'signalling of nuclear receptors' pathways were dysregulated in CD4+ T cells isolated from RRMS patients compared with healthy donors. While LXRB and genes associated with cholesterol metabolism were upregulated, other T cell LXR-target genes, including genes involved in cellular lipid uptake (inducible degrader of the LDL receptor, IDOL), and the rate-limiting enzyme for glycosphingolipid biosynthesis (UDP-glucosylceramide synthase, UGCG) were downregulated in T cells from patients with RRMS compared to healthy donors. Correspondingly, plasma membrane glycosphingolipids were reduced, and cholesterol levels increased in RRMS CD4+ T cells, an effect partially recapitulated in healthy T cells by in vitro culture with T cell receptor stimulation in the presence of serum from RRMS patients. Notably, stimulation with LXR-agonist GW3965 normalised membrane cholesterol levels, and reduced proliferation and IL17 cytokine production in RRMS CD4+ T-cells. Thus, LXR-mediated lipid metabolism pathways were dysregulated in T cells from patients with RRMS and could contribute to RRMS pathogenesis. Therapies that modify lipid metabolism could help restore immune cell function.

Exacerbated experimental arthritis in Wiskott-Aldrich syndrome protein deficiency: modulatory role of regulatory B cells.

Patients deficient in the cytoskeletal regulator Wiskott-Aldrich syndrome protein (WASp) are predisposed to varied autoimmunity, suggesting it has an important controlling role in participating cells. IL-10-producing regulatory B (Breg) cells are emerging as important mediators of immunosuppressive activity. In experimental, antigen-induced arthritis WASp-deficient (WASp knockout [WAS KO]) mice developed exacerbated disease associated with decreased Breg cells and regulatory T (Treg) cells, but increased Th17 cells in knee-draining LNs. Arthritic WAS KO mice showed increased serum levels of B-cell-activating factor, while their B cells were unresponsive in terms of B-cell-activating factor induced survival and IL-10 production. Adoptive transfer of WT Breg cells ameliorated arthritis in WAS KO recipients and restored a normal balance of Treg and Th17 cells. Mice with B-cell-restricted WASp deficiency, however, did not develop exacerbated arthritis, despite exhibiting reduced Breg- and Treg-cell numbers during active disease, and Th17 cells were not increased over equivalent WT levels. These findings support a contributory role for defective Breg cells in the development of WAS-related autoimmunity, but demonstrate that functional competence in other regulatory populations can be compensatory. A properly regulated cytoskeleton is therefore important for normal Breg-cell activity and complementation of defects in this lineage is likely to have important therapeutic benefits.

Defective inhibition of B-cell proliferation by Wiskott-Aldrich syndrome protein-deficient regulatory T cells.

Wiskott-Aldrich syndrome (WAS) is an inherited immunodeficiency characterized by high incidence of autoantibody-mediated autoimmune complications. Such a feature has been associated with defective suppressor activity of WAS protein-deficient, naturally occurring CD4(+)CD25(+)Foxp3(+) regulatory T cells on responder T cells. However, it remains to be established whether the altered B-cell tolerance reported in WAS patients and Was knockout (WKO) mice is secondary to abnormalities in the direct suppression of B-cell function by nTreg cells or to impaired regulation of T-helper function. Because activated nTreg cells are known to induce granzyme B-mediated B-cell killing, we decided to evaluate the regulatory capabilities of WKO nTregs on B lymphocytes. We found that preactivated WKO nTreg cells failed to effectively suppress B-cell proliferation and that such a defect was associated with reduced killing of B cells and significantly decreased degranulation of granzyme B. Altogether, these results provide additional mechanistic insights into the loss of immune tolerance in WAS.

Foamy virus vector-mediated gene correction of a mouse model of Wiskott-Aldrich syndrome.

The Wiskott-Aldrich syndrome (WAS) is an X-linked disorder characterized by eczema, thrombocytopenia and immunodeficiency. Hematopoietic cell transplantation can cure the disease and gene therapy is being tested as an alternative treatment option. In this study, we assessed the use of foamy virus (FV) vectors as a gene transfer system for WAS, using a Was knockout (KO) mouse model. Preliminary experiments using FV vectors expressing the green fluorescent protein under the transcriptional control of the endogenous WAS promoter or a ubiquitously acting chromatin opening element allowed us to define transduction conditions resulting in high (>40%) and long-term in-vivo marking of blood cells after transplantation. In following experiments, Was KO mice were treated with FV vectors containing the human WAS complementary DNA (cDNA). Transplanted animals expressed the WAS protein (WASp) in T and B lymphocytes, as well as platelets and showed restoration of both T-cell receptor-mediated responses and B-cell migration. We also observed recovery of platelet adhesion and podosome formation in dendritic cells (DCs) of treated mice. These data demonstrate that FV vectors can be effective for hematopoietic stem cell (HSC)-directed gene correction of WAS.

The cellular amount of the common gamma-chain influences spontaneous or induced cell proliferation.

Mutations of the IL2RG encoding the common gamma-chain (gamma(c)) lead to the X-linked SCID disease. Gene correction through ex vivo retroviral transduction restored the immunological impairment in the most of treated patients, although lymphoproliferative events occurred in five of them. Even though in two cases it was clearly documented an insertional mutagenesis in LMO2, it is conceivable that gamma(c) could have a role per se in malignant lymphoproliferation. The gamma(c) is a shared cytokine receptor subunit, involved also in growth hormone (GH) receptor signaling. Through short interfering RNA or using X-linked SCID B lymphoblastoid cell lines lacking gamma(c), we demonstrate that self-sufficient growth was strongly dependent on gamma(c) expression. Furthermore, a correlation between gamma(c) amount and the extent of constitutive activation of JAK3 was found. The reduction of gamma(c) protein expression also reduced GH-induced proliferation and STAT5 nuclear translocation in B lymphoblastoid cell lines. Hence, our data demonstrate that gamma(c) plays a remarkable role in either spontaneous or GH-induced cell cycle progression depending on the amount of protein expression, suggesting a potential role as enhancing cofactor in lymphoproliferation.

Using Serum Metabolomics to Predict Development of Anti-drug Antibodies in Multiple Sclerosis Patients Treated With IFNß.

Background: Neutralizing anti-drug antibodies (ADA) can greatly reduce the efficacy of biopharmaceuticals used to treat patients with multiple sclerosis (MS). However, the biological factors pre-disposing an individual to develop ADA are poorly characterized. Thus, there is an unmet clinical need for biomarkers to predict the development of immunogenicity, and subsequent treatment failure. Up to 35% of MS patients treated with beta interferons (IFNß) develop ADA. Here we use machine learning to predict immunogenicity against IFNß utilizing serum metabolomics data. Methods: Serum samples were collected from 89 MS patients as part of the ABIRISK consortium-a multi-center prospective study of ADA development. Metabolites and ADA were quantified prior to and after IFNß treatment. Thirty patients became ADA positive during the first year of treatment (ADA+). We tested the efficacy of six binary classification models using 10-fold cross validation; k-nearest neighbors, decision tree, random forest, support vector machine and lasso (Least Absolute Shrinkage and Selection Operator) logistic regression with and without interactions. Results: We were able to predict future immunogenicity from baseline metabolomics data. Lasso logistic regression with/without interactions and support vector machines were the most successful at identifying ADA+ or ADA- cases, respectively. Furthermore, patients who become ADA+ had a distinct metabolic response to IFNß in the first 3 months, with 29 differentially regulated metabolites. Machine learning algorithms could also predict ADA status based on metabolite concentrations at 3 months. Lasso logistic regressions had the greatest proportion of correct classifications [F1 score (accuracy measure) = 0.808, specificity = 0.913]. Finally, we hypothesized that serum lipids could contribute to ADA development by altering immune-cell lipid rafts. This was supported by experimental evidence demonstrating that, prior to IFNß exposure, lipid raft-associated lipids were differentially expressed between MS patients who became ADA+ or remained ADA-. Conclusion: Serum metabolites are a promising biomarker for prediction of ADA development in MS patients treated with IFNß, and could provide novel insight into mechanisms of immunogenicity.

Low Percentage of Signal Regulatory Protein α/ß+ Memory B Cells in Blood Predicts Development of Anti-drug Antibodies (ADA) in Adalimumab-Treated Rheumatoid Arthritis Patients.

An important goal for personalized treatment is predicting response to a particular therapeutic. A drawback of biological treatment is immunogenicity and the development of antibodies directed against the drug [anti-drug antibodies (ADA)], which are associated with a poorer clinical outcome. Here we set out to identify a predictive biomarker that discriminates rheumatoid arthritis (RA) patients who are more likely to develop ADA in response to adalimumab, a human monoclonal antibody against tumor necrosis factor (TNF)α. By taking advantage of an immune-phenotyping platform, LEGENDScreen™, we measured the expression of 332 cell surface markers on B and T cells in a cross-sectional adalimumab-treated RA patient cohort with a defined ADA response. The analysis revealed seven differentially expressed markers (DEMs) between the ADA+ and ADA- patients. Validation of the DEMs in an independent prospective European cohort of adalimumab treated RA patients, revealed a significant and consistent reduced frequency of signal regulatory protein (SIRP)α/ß-expressing memory B cells in ADA+ vs. ADA- RA patients. We also assessed the predictive value of SIRPα/ß expression in a longitudinal RA cohort prior to the initiation of adalimumab treatment. We show that a frequency of < 9.4% of SIRPα/ß-expressing memory B cells predicts patients that will develop ADA, and consequentially fail to respond to treatment, with a receiver operating characteristic (ROC) area under the curve (AUC) score of 0.92. Thus, measuring the frequency of SIRPα/ß-expressing memory B cells in patients prior to adalimumab treatment may be clinically useful to identify a subgroup of active RA subjects who are going to develop an ADA response and not gain substantial clinical benefit from this treatment.

Monocyte NOTCH2 expression predicts IFN-ß immunogenicity in multiple sclerosis patients.

Multiple sclerosis (MS) is an autoimmune disease characterized by CNS inflammation leading to demyelination and axonal damage. IFN-ß is an established treatment for MS; however, up to 30% of IFN-ß-treated MS patients develop neutralizing antidrug antibodies (nADA), leading to reduced drug bioactivity and efficacy. Mechanisms driving antidrug immunogenicity remain uncertain, and reliable biomarkers to predict immunogenicity development are lacking. Using high-throughput flow cytometry, NOTCH2 expression on CD14+ monocytes and increased frequency of proinflammatory monocyte subsets were identified as baseline predictors of nADA development in MS patients treated with IFN-ß. The association of this monocyte profile with nADA development was validated in 2 independent cross-sectional MS patient cohorts and a prospective cohort followed before and after IFN-ß administration. Reduced monocyte NOTCH2 expression in nADA+ MS patients was associated with NOTCH2 activation measured by increased expression of Notch-responsive genes, polarization of monocytes toward a nonclassical phenotype, and increased proinflammatory IL-6 production. NOTCH2 activation was T cell dependent and was only triggered in the presence of serum from nADA+ patients. Thus, nADA development was driven by a proinflammatory environment that triggered activation of the NOTCH2 signaling pathway prior to first IFN-ß administration.

Advances in understanding regulatory myeloid cells.

The Regulatory Myeloid Cells -- International Immunopharmacology Conference in October 21-24, 2010 reviewed the recent advances in our understanding of the biological mechanisms of expansion, activation, metabolism and mechanisms of T-cell suppression of Myeloid Derived Suppressor Cells (MDSC). Lectures were focused on the control of the microenvironment and cytokines needed for myelopoiesis, interactions with the neoplastic surrounding cells for a negative immune control, and the role of MDSC in cancer promotion. The complexity of the tumor microenvironment and opportunities for therapeutic interventions by targeting, and/or manipulating MDSCs was emphasized. A better understanding of the crosstalk between myelo- and lymphoid arms of the immune system and of the metabolic alterations contributing to cancer phenotype provide new insights for the development of more efficient tumor immunotherapy strategies. This meeting report aims to provide the readers with a summary of the research highlights on human and mouse MDSCs presented in the meeting.

Impaired in vitro regulatory T cell function associated with Wiskott-Aldrich syndrome.

Wiskott-Aldrich syndrome (WAS) is a primary immunodeficiency characterized by the contradictory coexistence of impaired T-cell function and exaggerated T-cell-mediated pathology, including autoimmunity and eczema. WAS protein (WASp)-deficient mice are also immunodeficient and can develop autoimmune disease. Since defects in regulatory T-cells (Treg) are associated with autoimmunity, we examined the presence and function of these cells in WAS patients and WASp-deficient mice. We found that CD4(+)CD25(+)FOXP3(+) Treg cells can develop in the absence of WASp expression. However, Treg cells both from WASp-deficient mice and from four out of five WAS patients studied showed impaired in vitro suppressor function. In WASp-deficient mice, this defect could be partially rescued by pre-activation with IL-2, suggesting that inadequate cell activation may play a role in WASp-deficient Treg dysfunction. These findings may provide insights into the complex pathophysiology and paradoxical phenotypes of WAS and suggest new therapeutic modalities for autoimmunity in these patients.

Functional interaction of common gamma-chain and growth hormone receptor signaling apparatus.

We previously reported on an X-linked SCID (X-SCID) patient, who also had peripheral growth hormone (GH) hyporesponsiveness and abnormalities of the protein phosphorylation events following GH receptor (GHR) stimulation. In the present study, we examined a potential role of common cytokine receptor gamma-chain (gammac) in GHR signaling using EBV-transformed lymphocytes from healthy subjects and gammac-negative X-SCID patients. We demonstrated that the proliferative response to GH stimulation of the B cell lines of gammac-negative patients was impaired despite a comparable cellular expression of GHR molecules to controls. In patients, after GH stimulation, no phosphorylation of STAT5 was observed. In addition, the molecule localization through confocal microscopy revealed that in B cell lines of patients no nuclear translocation of STAT5b following GH stimulation occurred differently from controls. Biochemical analysis of the nuclear extracts of gammac-negative cell lines provided further evidence that the amount of STAT5b and its phosphorylated form did not increase following GH stimulation. In patients, cells reconstituted with wild-type gammac abnormal biochemical and functional events were restored resulting in nuclear translocation of STAT5. Confocal experiments revealed that GHR and gammac were colocalized on the cell membrane. Our study demonstrates the existence of a previously unappreciated relationship between GHR-signaling pathway and gammac, which is required for the activation of STAT5b in B cell lines. These data also confirm that growth failure in X-SCID is primarily related to the genetic alteration of the IL2RG gene.

Cutaneous manifestations as presenting sign of autoimmune lymphoproliferative syndrome in childhood.

Autoimmune lymphoproliferative syndrome is a disorder due to a defect of lymphocyte apoptosis, whose clinical manifestations consist of hyperplasia of lymphoid tissues and autoimmune diseases. We report on a 26-month-old child who presented with frequent eruptions of weals and angioedema without any apparent triggering factor, who subsequently developed an erythematopapular rash with a histological pattern of a lymphoplasmacellular infiltrate. Familial anamnesis revealed a history of lymphoadenomegaly and massive spleen and liver enlargement in her sister. Functional and molecular analysis led to a diagnosis of type 1a autoimmune lymphoproliferative syndrome. Immunophenotyping of the cutaneous lesion revealed the presence of an inflammatory infiltrate with a considerably high number of Langerhans cells. Cutaneous features such as urticaria, angioedema and vasculitis in children with a personal and familial history of hyperplasia of lymphoid tissues may be a presenting sign of a systemic disease, such as autoimmune lymphoproliferative syndrome.

Atypical features of familial hemophagocytic lymphohistiocytosis.

Familial hemophagocytic lymphohistiocytosis (FHLH) is a rare, rapidly progressive disorder of early childhood characterized by uncontrolled activation of T cells and macrophages. Although perforin gene mutations have been described in a proportion of patients with FHLH, the genotype/phenotype correlation is still limited. Only a few patients with late onset clinical manifestations have been reported. The biochemical and immunologic alterations in the asymptomatic phase are not well known. We report on a family in which 2 fraternal twins both homozygous for a perforin mutation previously described as causative of the disease, markedly differed in phenotypic expression of FHLH. The twins also had a second novel heterozygous mutation. Natural killer (NK) activity was severely impaired in the patient and was normal in the asymptomatic fraternal twin. Our report highlights that FHLH may present after a long disease-free interval during which biochemical or immunologic alterations may be not evident, thus implying a role for interfering factors.