Autoreactive CD8+ T-cells are highly dependent on CD8 for activation and as such targeting CD8 is an effective way of blocking autoreactive CD8+ T-cell activation

Autoimmune diseases such as type I diabetes (TID) and multiple sclerosis (MS) are chronic conditions that have a significant impact on quality of life. CD8+ T-cells play an important role in the pathogenesis of these diseases. However, drugs that target the entire CD8+ T-cell population are not desirable because this population provides protection against infection. Accordingly, there is an urgent requirement to develop novel treatment strategies that exclusively target the autoreactive CD8+ T-cell population. CD8+ T-cells express a molecule called CD8 at their cell surface which assists with activation. We have demonstrated that autoreactive CD8+ T-cells are entirely dependent on CD8 for activation. In stark contrast, pathogen specific CD8+ T-cells are characterized by higher functional sensitivity and are relatively CD8 independent. This represents an intrinsic difference that can be exploited for therapeutic benefit. Our data suggests that “blocking anti-CD8 antibodies” can be used to block autoreactive CD8+ T-cell attack without affecting pathogen specific immunity, a key goal in the treatment of autoimmunity. The generation of “blocking anti-CD8 antibodies” offers an opportunity to develop a novel therapeutic approach that can be used to treat CD8+ T-cell mediated autoimmunity. In order to conduct a further assessment, we are currently developing a strategy for in vivo validation of the approach.

β-cell specific T-lymphocyte response has a distinct inflammatory phenotype in children with Type 1 diabetes compared with adults

AIM

To examine the hypothesis that the quality, magnitude and breadth of helper T-lymphocyte responses to β cells differ in Type 1 diabetes according to diagnosis in childhood or adulthood.

METHODS

We studied helper T-lymphocyte reactivity against β-cell autoantigens by measuring production of the pro-inflammatory cytokine interferon-γ and the anti-inflammatory cytokine interleukin-10, using enzyme-linked immunospot assays in 61 people with Type 1 diabetes (within 3 months of diagnosis, positive for HLA DRB1*0301 and/or *0401), of whom 33 were children/adolescents, and a further 91 were unaffected siblings.

RESULTS

Interferon-γ responses were significantly more frequent in children with Type 1 diabetes compared with adults (85 vs 61%; P = 0.04). Insulin and proinsulin peptides were preferentially targeted in children (P = 0.0001 and P = 0.04, respectively) and the breadth of the interferon-γ response was also greater, with 70% of children having an interferon-γ response to three or more peptides compared with 14% of adults (P < 0.0001). Islet β-cell antigen-specific interleukin-10 responses were similar in children and adults in terms of frequency, breadth and magnitude, with the exception of responses to glutamic acid decarboxylase 65, which were significantly less frequent in adults.

CONCLUSIONS

At diagnosis of Type 1 diabetes, pro-inflammatory autoreactivity is significantly more prevalent, focuses on a wider range of targets, and is more focused on insulin/proinsulin in children than adults. We interpret this as indicating a more aggressive immunological response in the younger age group that is especially characterized by loss of tolerance to proinsulin. These findings highlight the existence of age-related heterogeneity in Type 1 diabetes pathogenesis that could have relevance to the development of immune-based therapies.

A CD80-Biased CTLA4-Ig Fusion Protein with Superior In Vivo Efficacy by Simultaneous Engineering of Affinity, Selectivity, Stability, and FcRn Binding

Affinity- and stability-engineered variants of CTLA4-Ig fusion molecules with enhanced pharmacokinetic profiles could yield improved therapies with the potential of higher efficacy and greater convenience to patients. In this study, to our knowledge, we have, for the first time, used in vitro evolution to simultaneously optimize CTLA4 affinity and stability. We selected for improved binding to both ligands, CD80 and CD86, and screened as dimeric Fc fusions directly in functional assays to identify variants with stronger suppression of in vitro T cell activation. The majority of CTLA4 molecules showing the largest potency gains in primary in vitro and ex vivo human cell assays, using PBMCs from type 1 diabetes patients, had significant improvements in CD80, but only modest gains in CD86 binding. We furthermore observed different potency rankings between our lead molecule MEDI5265, abatacept, and belatacept, depending on which type of APC was used, with MEDI5265 consistently being the most potent. We then created fusions of both stability- and potency-optimized CTLA4 moieties with human Fc variants conferring extended plasma t1/2 In a cynomolgus model of T cell-dependent Ab response, the CTLA4-Ig variant MEDI5265 could be formulated at >100 mg/ml for s.c. administration and showed superior efficacy and significantly prolonged serum t1/2 The combination of higher stability and potency with prolonged pharmacokinetics could be compatible with very infrequent, s.c. dosing while maintaining a similar level of immune suppression to more frequently and i.v. administered licensed therapies.

Immunogenicity of human embryonic stem cell-derived beta cells

AIMS/HYPOTHESIS

To overcome the donor shortage in the treatment of advanced type 1 diabetes by islet transplantation, human embryonic stem cells (hESCs) show great potential as an unlimited alternative source of beta cells. hESCs may have immune privileged properties and it is important to determine whether these properties are preserved in hESC-derived cells.

METHODS

We comprehensively investigated interactions of both innate and adaptive auto- and allo-immunity with hESC-derived pancreatic progenitor cells and hESC-derived endocrine cells, retrieved after in-vivo differentiation in capsules in the subcutis of mice.

RESULTS

We found that hESC-derived pancreatic endodermal cells expressed relatively low levels of HLA endorsing protection from specific immune responses. HLA was upregulated when exposed to IFNγ, making these endocrine progenitor cells vulnerable to cytotoxic T cells and alloreactive antibodies. In vivo-differentiated endocrine cells were protected from complement, but expressed more HLA and were targets for alloreactive antibody-dependent cellular cytotoxicity and alloreactive cytotoxic T cells. After HLA compatibility was provided by transduction with HLA-A2, preproinsulin-specific T cells killed insulin-producing cells.

CONCLUSIONS/INTERPRETATION

hESC-derived pancreatic progenitors are hypoimmunogenic, while in vivo-differentiated endocrine cells represent mature targets for adaptive immune responses. Our data support the need for immune intervention in transplantation of hESC-derived pancreatic progenitors. Cell-impermeable macro-encapsulation may suffice.

Rebranding asymptomatic type 1 diabetes: the case for autoimmune beta cell disorder as a pathological and diagnostic entity

The asymptomatic phase of type 1 diabetes is recognised by the presence of beta cell autoantibodies in the absence of hyperglycaemia. We propose that an accurate description of this stage is provided by the name 'Autoimmune Beta Cell Disorder' (ABCD). Specifically, we suggest that this nomenclature and diagnosis will, in a proactive manner, shift the paradigm towards type 1 diabetes being first and foremost an immune-mediated disease and only later a metabolic disease, presaging more active therapeutic intervention in the asymptomatic stage of disease, before end-stage beta cell failure. Furthermore, we argue that accepting ABCD as a diagnosis will be critical in order to accelerate pharmaceutical, academic and public activities leading to clinical trials that could reverse beta cell autoimmunity and halt progression to symptomatic insulin-requiring type 1 diabetes. We recognize that there are both opportunities and challenges in the implementation of the ABCD concept but hope that the notion of 'asymptomatic autoimmune disease' as a disorder will be widely discussed and eventually accepted.

Stimulated urine C-peptide creatinine ratio vs serum C-peptide level for monitoring of β-cell function in the first year after diagnosis of Type 1 diabetes

AIMS

To determine if urine C-peptide/creatinine ratio is a useful tool for monitoring β-cell function in new-onset Type 1 diabetes.

METHODS

Data were obtained from a prospective immunomodulation study in people with Type 1 diabetes ≤ 3 months from diagnosis, with a standard mixed-meal tolerance test and measurement of urine C-peptide/creatinine ratio carried out at 0, 3, 6, 9 and 12 months. The change in the insulin-dose-adjusted HbA_1c level was also correlated with the change in serum/urine C-peptide level during the 12-month follow-up period.

RESULTS

A significant reduction in urine C-peptide/creatinine ratio, measured after a mixed-meal, was reached at 9 months (-45.4%), whilst the reduction in stimulated serum C-peptide level reached significance after 3 months (-54.7%) in placebo-treated participants. Neither change in stimulated serum C-peptide nor change in urine C-peptide level correlated with each other, and nor did change in insulin-dose-adjusted HbA_1c level in the first 6 months, but all measures correlated significantly in the second half of the 12-month follow-up period.

CONCLUSION

Mixed-meal-stimulated urine C-peptide/creatinine ratio was similar to, although less sensitive than, stimulated serum C-peptide level in monitoring β-cell function during the first year after diagnosis. Because the former is significantly less invasive, it warrants inclusion in further studies in Type 1 diabetes and may represent an attractive alternative outcome measure in cohort studies and in children.

Targeted suppression of autoreactive CD8+ T-cell activation using blocking anti-CD8 antibodies

CD8⁺ T-cells play a role in the pathogenesis of autoimmune diseases such as multiple sclerosis and type 1 diabetes. However, drugs that target the entire CD8⁺ T-cell population are not desirable because the associated lack of specificity can lead to unwanted consequences, most notably an enhanced susceptibility to infection. Here, we show that autoreactive CD8⁺ T-cells are highly dependent on CD8 for ligand-induced activation via the T-cell receptor (TCR). In contrast, pathogen-specific CD8⁺ T-cells are relatively CD8-independent. These generic differences relate to an intrinsic dichotomy that segregates self-derived and exogenous antigen-specific TCRs according to the monomeric interaction affinity with cognate peptide-major histocompatibility complex class I (pMHCI). As a consequence, “blocking” anti-CD8 antibodies can suppress autoreactive CD8⁺ T-cell activation in a relatively selective manner. These findings provide a rational basis for the development and in vivo assessment of novel therapeutic strategies that preferentially target disease-relevant autoimmune responses within the CD8⁺ T-cell compartment.

Hydrophobic CDR3 residues promote the development of self-reactive T cells

Studies of individual T cell antigen receptors (TCRs) have shed some light on structural features that underlie self-reactivity. However, the general rules that can be used to predict whether TCRs are self-reactive have not been fully elucidated. Here we found that the interfacial hydrophobicity of amino acids at positions 6 and 7 of the complementarity-determining region CDR3β robustly promoted the development of self-reactive TCRs. This property was found irrespective of the member of the β-chain variable region (Vβ) family present in the TCR or the length of the CDR3β. An index based on these findings distinguished Vβ2(+), Vβ6(+) and Vβ8.2(+) regulatory T cells from conventional T cells and also distinguished CD4(+) T cells selected by the major histocompatibility complex (MHC) class II molecule I-A(g7) (associated with the development of type 1 diabetes in NOD mice) from those selected by a non-autoimmunity-promoting MHC class II molecule I-A(b). Our results provide a means for distinguishing normal T cell repertoires versus autoimmunity-prone T cell repertoires.

Hotspot autoimmune T cell receptor binding underlies pathogen and insulin peptide cross-reactivity

The cross-reactivity of T cells with pathogen- and self-derived peptides has been implicated as a pathway involved in the development of autoimmunity. However, the mechanisms that allow the clonal T cell antigen receptor (TCR) to functionally engage multiple peptide–major histocompatibility complexes (pMHC) are unclear. Here, we studied multiligand discrimination by a human, preproinsulin reactive, MHC class-I–restricted CD8⁺ T cell clone (1E6) that can recognize over 1 million different peptides. We generated high-resolution structures of the 1E6 TCR bound to 7 altered peptide ligands, including a pathogen-derived peptide that was an order of magnitude more potent than the natural self-peptide. Evaluation of these structures demonstrated that binding was stabilized through a conserved lock-and-key–like minimal binding footprint that enables 1E6 TCR to tolerate vast numbers of substitutions outside of this so-called hotspot. Highly potent antigens of the 1E6 TCR engaged with a strong antipathogen-like binding affinity; this engagement was governed though an energetic switch from an enthalpically to entropically driven interaction compared with the natural autoimmune ligand. Together, these data highlight how T cell cross-reactivity with pathogen-derived antigens might break self-tolerance to induce autoimmune disease.

Dendritic Cells Guide Islet Autoimmunity through a Restricted and Uniquely Processed Peptidome Presented by High-Risk HLA-DR

Identifying T cell epitopes of islet autoantigens is important for understanding type 1 diabetes (T1D) immunopathogenesis and to design immune monitoring and intervention strategies in relationship to disease progression. Naturally processed T cell epitopes have been discovered by elution from HLA-DR4 of pulsed B lymphocytes. The designated professional APC directing immune responses is the dendritic cell (DC). To identify naturally processed epitopes, monocyte-derived DC were pulsed with preproinsulin (PPI), glutamic acid decarboxylase (65-kDa isoform; GAD65), and insulinoma-associated Ag-2 (IA-2), and peptides were eluted of HLA-DR3 and -DR4, which are associated with highest risk for T1D development. Proteome analysis confirmed uptake and processing of islet Ags by DC. PPI peptides generated by DC differed from those processed by B lymphocytes; PPI signal-sequence peptides were eluted from HLA-DR4 and -DR3/4 that proved completely identical to a primary target epitope of diabetogenic HLA-A2-restricted CD8 T cells. HLA-DR4 binding was confirmed. GAD65 peptides, eluted from HLA-DR3 and -DR4, encompassed two core regions overlapping the two most immunodominant and frequently studied CD4 T cell targets. GAD65 peptides bound to HLA-DR3. Strikingly, the IA-2 ligandome of HLA-DR was exclusively generated from the extracellular part of IA-2, whereas most previous immune studies have focused on intracellular IA-2 epitopes. The newly identified IA-2 peptides bound to HLA-DR3 and -DR4. Differential T cell responses were detected against the newly identified IA-2 epitopes in blood from T1D patients. The core regions to which DC may draw attention from autoreactive T cells are largely distinct and more restricted than are those of B cells. GAD65 peptides presented by DC focus on highly immunogenic T cell targets, whereas HLA-DR-binding peptides derived from IA-2 are distinct from the target regions of IA-2 autoantibodies.

Discovery of a Selective Islet Peptidome Presented by the Highest-Risk HLA-DQ8trans Molecule

HLA-DQ2/8 heterozygous individuals are at far greater risk for type 1 diabetes (T1D) development by expressing HLA-DQ8trans on antigen-presenting cells compared with HLA-DQ2 or -DQ8 homozygous individuals. Dendritic cells (DC) initiate and shape adaptive immune responses by presenting HLA-epitope complexes to naïve T cells. To dissect the role of HLA-DQ8trans in presenting natural islet epitopes, we analyzed the islet peptidome of HLA-DQ2, -DQ8, and -DQ2/8 by pulsing DC with preproinsulin (PPI), IA-2, and GAD65. Quality and quantity of islet epitopes presented by HLA-DQ2/8 differed from -DQ2 or -DQ8. We identified two PPI epitopes solely processed and presented by HLA-DQ2/8 DC: an HLA-DQ8trans-binding signal-sequence epitope previously identified as CD8 T-cell epitope and a second epitope that we previously identified as CD4 T-cell epitope with increased binding to HLA-DQ8trans upon posttranslational modification. IA-2 epitopes retrieved from HLA-DQ2/8 and -DQ8 DC bound to HLA-DQ8cis/trans. No GAD65 epitopes were eluted from HLA-DQ. T-cell responses were detected against the novel islet epitopes in blood from patients with T1D but scantly detected in healthy donor subjects. We report the first PPI and IA-2 natural epitopes presented by highest-risk HLA-DQ8trans. The selective processing and presentation of HLA-DQ8trans-binding islet epitopes provides insight in the mechanism of excessive genetic risk imposed by HLA-DQ2/8 heterozygosity and may assist immune monitoring of disease progression and therapeutic intervention as well as provide therapeutic targets for immunotherapy in subjects at risk for T1D.

Adjuvanted influenza-H1N1 vaccination reveals lymphoid signatures of age-dependent early responses and of clinical adverse events

Adjuvanted vaccines afford invaluable protection against disease, and the molecular and cellular changes they induce offer direct insight into human immunobiology. Here we show that within 24 h of receiving adjuvanted swine flu vaccine, healthy individuals made expansive, complex molecular and cellular responses that included overt lymphoid as well as myeloid contributions. Unexpectedly, this early response was subtly but significantly different in people older than ∼35 years. Wide-ranging adverse clinical events can seriously confound vaccine adoption, but whether there are immunological correlates of these is unknown. Here we identify a molecular signature of adverse events that was commonly associated with an existing B cell phenotype. Thus immunophenotypic variation among healthy humans may be manifest in complex pathophysiological responses.

Innate and adaptive immunity to human beta cell lines: implications for beta cell therapy

AIMS/HYPOTHESIS

Genetically engineered human beta cell lines provide a novel source of human beta cells to study metabolism, pharmacology and beta cell replacement therapy. Since the immune system is essentially involved in beta cell destruction in type 1 diabetes and after beta cell transplantation, we investigated the interaction of human beta cell lineswith the immune system to resolve their potential for immune intervention protocol studies.

METHODS

Human pancreatic beta cell lines (EndoC-βH1 and ECi50) generated by targeted oncogenesis in fetal pancreas were assessed for viability after innate and adaptive immune challenges. Beta cell lines were pre-conditioned with T helper type 1 (Th1) cytokines or high glucose to mimic inflammatory and hyperglycaemia-stressed conditions. Beta cells were then co-cultured with auto- and alloreactive cytotoxic T cells (CTL), natural killer (NK) cells, supernatant fraction from activated autoreactive Th1 cells, or alloantibodies in the presence of complement or effector cells.

RESULTS

Low HLA expression protected human beta cell lines from adaptive immune destruction, but it was associated with direct killing by activated NK cells. Autoreactive Th1 cell inflammation, rather than glucose stress, induced increased beta cell apoptosis and upregulation of HLA, increasing beta cell vulnerability to killing by auto- and alloreactive CTL and alloreactive antibodies.

CONCLUSIONS/INTERPRETATION

We demonstrate that genetically engineered human beta cell lines can be used in vitro to assess diverse immune responses that may be involved in the pathogenesis of type 1 diabetes in humans and beta cell transplantation, enabling preclinical evaluation of novel immune intervention strategies protecting beta cells from immune destruction.

Proinsulin multi-peptide immunotherapy induces antigen-specific regulatory T cells and limits autoimmunity in a humanized model

Peptide immunotherapy (PIT) is a targeted therapeutic approach, involving administration of disease-associated peptides, with the aim of restoring antigen-specific immunological tolerance without generalized immunosuppression. In type 1 diabetes, proinsulin is a primary antigen targeted by the autoimmune response, and is therefore a strong candidate for exploitation via PIT in this setting. To elucidate the optimal conditions for proinsulin-based PIT and explore mechanisms of action, we developed a preclinical model of proinsulin autoimmunity in a humanized HLA-DRB1*0401 transgenic HLA-DR4 Tg mouse. Once proinsulin-specific tolerance is broken, HLA-DR4 Tg mice develop autoinflammatory responses, including proinsulin-specific T cell proliferation, interferon (IFN)-γ and autoantibody production. These are preventable and quenchable by pre- and post-induction treatment, respectively, using intradermal proinsulin-PIT injections. Intradermal proinsulin-PIT enhances proliferation of regulatory [forkhead box protein 3 (FoxP3(+))CD25(high) ] CD4 T cells, including those capable of proinsulin-specific regulation, suggesting this as its main mode of action. In contrast, peptide delivered intradermally on the surface of vitamin D3-modulated (tolerogenic) dendritic cells, controls autoimmunity in association with proinsulin-specific IL-10 production, but no change in regulatory CD4 T cells. These studies define a humanized, translational model for in vivo optimization of PIT to control autoimmunity in type 1 diabetes and indicate that dominant mechanisms of action differ according to mode of peptide delivery.

More tricks with tetramers: a practical guide to staining T cells with peptide-MHC multimers

Analysis of antigen-specific T-cell populations by flow cytometry with peptide-MHC (pMHC) multimers is now commonplace. These reagents allow the tracking and phenotyping of T cells during infection, autoimmunity and cancer, and can be particularly revealing when used for monitoring therapeutic interventions. In 2009, we reviewed a number of 'tricks' that could be used to improve this powerful technology. More recent advances have demonstrated the potential benefits of using higher order multimers and of 'boosting' staining by inclusion of an antibody against the pMHC multimer. These developments now allow staining of T cells where the interaction between the pMHC and the T-cell receptor is over 20-fold weaker (K(D) > 1 mm) than could previously be achieved. Such improvements are particularly relevant when using pMHC multimers to stain anti-cancer or autoimmune T-cell populations, which tend to bear lower affinity T-cell receptors. Here, we update our previous work to include discussion of newer tricks that can produce substantially brighter staining even when using log-fold lower concentrations of pMHC multimer. We further provide a practical guide to using pMHC multimers that includes a description of several common pitfalls and how to circumvent them.

Characterization of the autoimmune response against the nerve tissue S100β in patients with type 1 diabetes

Type 1 diabetes results from destruction of insulin-producing beta cells in pancreatic islets and is characterized by islet cell autoimmunity. Autoreactivity against non-beta cell-specific antigens has also been reported, including targeting of the calcium-binding protein S100β. In preclinical models, reactivity of this type is a key component of the early development of insulitis. To examine the nature of this response in type 1 diabetes, we identified naturally processed and presented peptide epitopes derived from S100β, determined their affinity for the human leucocyte antigen (HLA)-DRB1*04:01 molecule and studied T cell responses in patients, together with healthy donors. We found that S100β reactivity, characterized by interferon (IFN)-γ secretion, is a characteristic of type 1 diabetes of varying duration. Our results confirm S100β as a target of the cellular autoimmune response in type 1 diabetes with the identification of new peptide epitopes targeted during the development of the disease, and support the preclinical findings that autoreactivity against non-beta cell-specific autoantigens may have a role in type 1 diabetes pathogenesis.

Heterogeneity in the Locomotory Behavior of Human Monocyte Subsets over Human Vascular Endothelium In Vitro

Human monocytes comprise three distinct subsets, defined by their relative expression of CD14 and CD16. These subsets appear to have different functional roles within homeostasis and inflammation, but little is known about the manner in which they interact with macro- and microvascular endothelial cells, a key enabling component for the fulfillment of their functional roles. In the present study, we examined the locomotory behavior of the three major human monocyte subsets over human endothelial monolayers subjected to physiologically relevant levels of shear flow in vitro. Each subset was shown to preferentially perform different types of locomotory behavior in a resting state. A long-range crawling behavior, similar to the "patrolling" behavior of murine Ly6C(-) monocytes, was observed in CD14(+)CD16(-) and CD14(dim)CD16(+) monocytes, but not in CD14(+)CD16(+) monocytes. CD14(dim)CD16(+) and CD14(+)CD16(+) monocytes showed a preference for adhering to microvascular over macrovascular endothelium, whereas CD14(+)CD16(-) monocytes showed the opposite. Transendothelial migration was not observed in CD14(dim)CD16(+) monocytes during the 30-min observation period. Long-range crawling behavior in CD14(dim)CD16(+) monocytes was abrogated by blockade of ICAM1, VCAM1, or CX3CL1, in contrast with CD14(+)CD16(-) monocytes, which only required ICAM1 for this behavior. These studies indicate the existence of subtype-specific human monocyte migratory behavior patterns with distinct adhesion molecule dependence, which may assist in elucidating their physiological function and relevance to disease.

β-cell-specific CD8 T cell phenotype in type 1 diabetes reflects chronic autoantigen exposure

Autoreactive CD8 T cells play a central role in the destruction of pancreatic islet β-cells that leads to type 1 diabetes, yet the key features of this immune-mediated process remain poorly defined. In this study, we combined high-definition polychromatic flow cytometry with ultrasensitive peptide-human leukocyte antigen class I tetramer staining to quantify and characterize β-cell-specific CD8 T cell populations in patients with recent-onset type 1 diabetes and healthy control subjects. Remarkably, we found that β-cell-specific CD8 T cell frequencies in peripheral blood were similar between subject groups. In contrast to healthy control subjects, however, patients with newly diagnosed type 1 diabetes displayed hallmarks of antigen-driven expansion uniquely within the β-cell-specific CD8 T cell compartment. Molecular analysis of selected β-cell-specific CD8 T cell populations further revealed highly skewed oligoclonal T cell receptor repertoires comprising exclusively private clonotypes. Collectively, these data identify novel and distinctive features of disease-relevant CD8 T cells that inform the immunopathogenesis of type 1 diabetes.