Early changes in the circulating T cells are associated with clinical outcomes after PD-L1 blockade by durvalumab in advanced NSCLC patients.

Immune checkpoint inhibitors (ICI) are designed to activate exhausted tumor-reactive T cells thereby leading to tumor regression. Durvalumab, an ICI that binds to the programmed death ligand-1 (PD-L1) molecule, is approved as a consolidation therapy for treatment of patients with stage III, unresectable, non-small cell lung cancer (NSCLC). Immunophenotypic analysis of circulating immune cells revealed increases in circulating proliferating CD4 + and CD8 + T cells earlier after durvalumab treatment. To examine durvalumab's mechanism of action and identify potential predictive biomarkers, we assessed the circulating T cells phenotypes and TCR genes of 71 NSCLC patients receiving durvalumab enrolled in a Phase I trial (NCT01693562, September 14, 2012). Next-generation sequencing of TCR repertoire was performed on these NSCLC patients' peripheral blood samples at baseline and day 15. Though patients' TCR repertoire diversity showed mixed responses to the treatment, patients exhibiting increased diversity on day 15 attained significantly longer overall survival (OS) (median OS was not reached vs 17.2 months for those with decreased diversity, p = 0.015). We applied network analysis to assess convergent T cell clonotypes indicative of an antigen-driven immune response. Patients with larger TCR clusters had improved OS (median OS was not reached vs 13.1 months for patients with smaller TCR clusters, p = 0.013). Early TCR repertoire diversification after durvalumab therapy for NSCLC may be predictive of increased survival and provides a mechanistic basis for durvalumab pharmacodynamic activity.

ECM components guide IL-10 producing regulatory T-cell (TR1) induction from effector memory T-cell precursors.

We describe a role for ECM as a biosensor for inflammatory microenvironments that plays a critical role in peripheral immune tolerance. We show that hyaluronan (HA) promotes induction of Foxp3- IL-10-producing regulatory T cells (TR1) from conventional T-cell precursors in both murine and human systems. This is, to our knowledge, the first description of an ECM component inducing regulatory T cells. Intact HA, characteristic of healing tissues, promotes induction of TR1 capable of abrogating disease in an IL-10-dependent mouse colitis model whereas fragmentary HA, typical of inflamed tissues, does not, indicating a decisive role for tissue integrity in this system. The TR1 precursor cells in this system are CD4(+)CD62L(-)FoxP3(-), suggesting that effector memory cells assume a regulatory phenotype when they encounter their cognate antigen in the context of intact HA. Matrix integrity cues might thereby play a central role in maintaining peripheral tolerance. This TR1 induction is mediated by CD44 cross-linking and signaling through p38 and ERK1/2. This induction is suppressed, also in a CD44-dependent manner, by osteopontin, a component of chronically inflamed ECM, indicating that CD44 signaling serves as a nexus for fate decisions regarding TR1 induction. Finally, we demonstrate that TR1 induction signals can be recapitulated using synthetic matrices. These results reveal important roles for the matrix microenvironment in immune regulation and suggest unique strategies for immunomodulation.

Phase 1/2 study of monalizumab plus durvalumab in patients with advanced solid tumors.

BACKGROUND: The combination of monalizumab (anti-NKG2A/CD94) and durvalumab (anti-programmed death ligand-1) may promote antitumor immunity by targeting innate and adaptive immunity. This phase 1/2 study of monalizumab and durvalumab evaluated safety, antitumor activity, and pharmacodynamics in patients with advanced solid tumors. MAIN BODY: Immunotherapy-naïve patients aged ≥18 years with advanced disease, Eastern Cooperative Oncology Group performance status of 0-1, and 1-3 prior lines of systemic therapy in the recurrent/metastatic setting were enrolled. In part 1 (dose escalation), patients received durvalumab 1500 mg every 4 weeks (Q4W) with increasing doses of monalizumab Q2W/Q4W (n=15). Dose expansion in part 1 included patients with cervical cancer (n=15; durvalumab 1500 mg Q4W and monalizumab 750 mg Q2W) or metastatic microsatellite stable (MSS)-colorectal cancer (CRC) (n=15; durvalumab 1500 mg Q4W and monalizumab 750 mg Q4W). In part 2 (dose expansion), patients with MSS-CRC (n=40), non-small cell lung cancer (NSCLC; n=20), MSS-endometrial cancer (n=40), or ovarian cancer (n=40) received durvalumab 1500 mg Q4W and monalizumab 750 mg Q2W. The primary endpoint was safety. Secondary endpoints included antitumor activity per Response Evaluation Criteria In Solid Tumors version 1.1 (RECIST v1.1). Exploratory analyses included assessment of T-cell and natural killer (NK) cell activation and proliferation in peripheral blood and the tumor microenvironment (TME). The study enrolled 185 patients (part 1, 45; part 2, 140). No dose-limiting toxicities were observed and the maximum tolerated dose was not reached. In part 2, the most common treatment-related adverse events were fatigue (12.1%), asthenia (9.3%), diarrhea (9.3%), pruritus (7.9%), and pyrexia (7.1%). In the expansion cohorts, response rates were 0% (cervical), 7.7% (MSS-CRC), 10% (NSCLC), 5.4% (ovarian), and 0% (MSS-endometrial). Sustained NK cell activation, CD8+ T-cell proliferation, increased serum levels of CXCL10 (C-X-C motif chemokine ligand 10) and CXCL11, and increased tumor infiltration of CD8+ and granzyme B+ cells were observed. CONCLUSIONS: Although efficacy was modest, monalizumab plus durvalumab was well tolerated and encouraging immune activation was observed in the peripheral blood and TME. TRIAL REGISTRATION NUMBER: NCT02671435.

Maintenance of immune tolerance to a neo-self acetylcholine receptor antigen with aging: implications for late-onset autoimmunity.

Age-related changes in immune regulation are likely to account for the age-associated increase in serum autoantibody levels and in certain autoimmune disorders, such as myasthenia gravis (MG). To demonstrate directly a loss of immune tolerance in older individuals, responses to the acetylcholine receptor, the autoantigen in MG, were assessed in transgenic mice expressing the Torpedo californica acetylcholine receptor (TAChR) alpha-chain as a neo-self Ag. T cells from young transgenic mice had been shown to be tolerant to p146-162, the TAChR alpha-chain peptide that dominated young nontransgenic T cell responses in vitro. The immunodominance of p146-162 was not lost with age; fine specificity was preserved. Moreover, T cell tolerance to p146-162, as well as to other epitopes of the TAChR alpha-chain extracellular domain, was maintained in old transgenic mice. Even multiple TAChR immunizations coupled with the MG-enhancing cytokine, IL-12, did not break tolerance. In addition, T cells exhibiting CD4 upregulation, an early activation marker, were reduced in frequency equivalently in old and young transgenic animals, suggesting that immune regulation in this model was not impacted by aging. Moreover, B cell tolerance was also maintained with age. The persistence of immune tolerance was accompanied by an increase in the proportion of T regulatory cells; it is speculated that this may compensate for deficiencies in central tolerance that occur owing to thymic involution. In summary, our study reveals, for the first time, that some immune tolerance mechanisms do survive aging; this suggests that certain late-onset autoimmune disorders may be induced by a specific insult that disrupts immune homeostasis.

Assessment of seasonal influenza A virus-specific CD4 T-cell responses to 2009 pandemic H1N1 swine-origin influenza A virus.

Very limited evidence has been reported to show human adaptive immune responses to the 2009 pandemic H1N1 swine-origin influenza A virus (S-OIV). We studied 17 S-OIV peptides homologous to immunodominant CD4 T epitopes from hemagglutinin (HA), neuraminidase (NA), nuclear protein (NP), M1 matrix protein (MP), and PB1 of a seasonal H1N1 strain. We concluded that 15 of these 17 S-OIV peptides would induce responses of seasonal influenza virus-specific T cells. Of these, seven S-OIV sequences were identical to seasonal influenza virus sequences, while eight had at least one amino acid that was not conserved. T cells recognizing epitopes derived from these S-OIV antigens could be detected ex vivo. Most of these T cells expressed memory markers, although none of the donors had been exposed to S-OIV. Functional analysis revealed that specific amino acid differences in the sequences of these S-OIV peptides would not affect or partially affect memory T-cell responses. These findings suggest that without protective antibody responses, individuals vaccinated against seasonal influenza A may still benefit from preexisting cross-reactive memory CD4 T cells reducing their susceptibility to S-OIV infection.

Changes in autoreactive T cell avidity during type 1 diabetes development.

The activation threshold for antigen-specific T cell responses is dependent on the avidity of the trimolecular interaction between TCR, antigen, and MHC. We compared CD4+ T cell avidities for the diabetes-associated autoantigen glutamic acid decarboxylase 555-567 (GAD 555) among serial samples from autoantibody-positive subjects at high risk of progression to type 1 diabetes (T1D). T cells from three at-risk subjects demonstrated significant avidity increases (p<0.05 by F test) over time. This avidity shift correlated with the outgrowth of T cells expressing TCR BV 9, 15, 17 or 20 that demonstrated higher GAD 555 tetramer-binding levels compared to cells expressing other TCR BV genes. Similar analysis of autoantibody-negative, first-degree relatives and T1D patients did not demonstrate similar changes in avidity. These data implicate the outgrowth of T cells expressing higher affinity TCR in a process of antigen-specific T cell avidity maturation during the pre-clinical stage of T1D.

Recognition of HLA class I-restricted beta-cell epitopes in type 1 diabetes.

Type 1 diabetes results from the autoimmune destruction of insulin-producing pancreatic beta-cells by cytotoxic T-lymphocytes (CTLs). In humans, few beta-cell epitopes have been reported, thereby limiting the study of beta-cell-specific CTLs in type 1 diabetes. To identify additional epitopes, HLA class I peptide affinity algorithms were used to identify a panel of peptides derived from the beta-cell proteins islet amyloid polypeptide (IAPP), islet-specific glucose-6-phosphatase catalytic subunit-related protein (IGRP), insulin, insulinoma-associated antigen 2 (IA-2), and phogrin that were predicted to bind HLA-A*0201. Peripheral blood mononuclear cells from 24 HLA-A*0201 recent-onset type 1 diabetic patients and 11 nondiabetic control subjects were evaluated for gamma-interferon secretion in response to peptide stimulation in enzyme-linked immunospot assays. We identified peptides IAPP9-17, IGRP215-223, IGRP152-160, islet IA-2(172-180), and IA-2(482-490) as novel HLA-A*0201-restricted T-cell epitopes in type 1 diabetic patients. Interestingly, we observed a strong inverse correlation between the binding affinity of beta-cell peptides to HLA-A*0201 and CTL responses against those peptides in recent-onset type 1 diabetic patients. In addition, we found that self-reactive CTLs with specificity for an insulin peptide are frequently present in healthy individuals. These data suggest that many beta-cell epitopes are recognized by CTLs in recent-onset type 1 diabetic patients. These epitopes may be important in the pathogenesis of type 1 diabetes.

Identification of Novel HLA-A*0201-restricted epitopes in recent-onset type 1 diabetic subjects and antibody-positive relatives.

Cytotoxic T-lymphocytes (CTLs) are considered to be essential for beta-cell destruction in type 1 diabetes. However, few islet-associated peptides have been demonstrated to activate autoreactive CTLs from type 1 diabetic subjects. In an effort to identify novel epitopes, we used matrix-assisted algorithms to predict peptides of glial fibrillary acidic protein (GFAP), prepro-islet amyloid polypeptide (ppIAPP), and islet-specific glucose-6-phosphatase catalytic subunit-related protein (IGRP) that likely bind to HLA-A*0201 with a strong affinity and contain a COOH-terminal proteasomal cleavage site. Seven peptides stabilized HLA-A*0201 expression in binding assays and were used to stimulate peripheral blood mononuclear cells and were evaluated for granzyme B secretion. We found that 5 of 13 type 1 diabetic subjects and 4 of 6 antibody-positive relatives exhibited greater numbers of granzyme B-secreting cells in response to at least one putative epitope compared with healthy control subjects. The most prevalent responses in antibody-positive and type 1 diabetic subjects were to ppIAPP(9-17). Other peptides recognized by type 1 diabetic or antibody-positive subjects included GFAP(143-151), IGRP(152-160), and GFAP(214-222). These data implicate peptides of ppIAPP, GFAP, and IGRP as CTL epitopes for a heterogenous CD8(+) T-cell response in type 1 subjects and antibody-positive relatives.

A hierarchy of T cell receptor motifs determines responsiveness to the immunodominant epitope in experimental autoimmune myasthenia gravis.

The predominant murine T lymphocyte population responding to Talpha146-162, the immunodominant epitope in EAMG, expresses the TCRBV 6 gene segment. However, cells expressing other TCRBV gene segments also react with this peptide. In order to more precisely characterize the Talpha146-162-specific TCR repertoire, we isolated CD4high cells from peptide-immunized mice. The majority of CD4high cells utilized an acidic TCR beta chain CDR3 motif regardless of TCRBV gene usage. Analysis of T cell clones demonstrated a fourfold higher avidity of Vbeta6+ than non-Vbeta6 cells for Talpha146-162 indicating that a hierarchy of TCR motifs determines T cell responsiveness in EAMG.

Discovery of T cell antigens by high-throughput screening of synthetic minigene libraries.

The identification of novel T cell antigens is central to basic and translational research in autoimmunity, tumor immunology, transplant immunology, and vaccine design for infectious disease. However, current methods for T cell antigen discovery are low throughput, and fail to explore a wide range of potential antigen-receptor interactions. To overcome these limitations, we developed a method in which programmable microarrays are used to cost-effectively synthesize complex libraries of thousands of minigenes that collectively encode the content of hundreds of candidate protein targets. Minigene-derived mRNA are transfected into autologous antigen presenting cells and used to challenge complex populations of purified peripheral blood CD8+ T cells in multiplex, parallel ELISPOT assays. In this proof-of-concept study, we apply synthetic minigene screening to identify two novel pancreatic islet autoantigens targeted in a patient with Type I Diabetes. To our knowledge, this is the first successful screen of a highly complex, synthetic minigene library for identification of a T cell antigen. In principle, responses against the full protein complement of any tissue or pathogen can be assayed by this approach, suggesting that further optimization of synthetic libraries holds promise for high throughput antigen discovery.

Discrete T cell populations with specificity for a neo-self-antigen bear distinct imprints of tolerance.

Mice expressing the Torpedo acetylcholine receptor alpha-chain as a neo-self-Ag exhibit a reduced frequency of T cells responding to the immunodominant epitope Talpha146-162 indicating a degree of tolerance. We characterized tolerance induction in these animals by analyzing the residual Talpha146-162-responsive T cell population and comparing it to that of nontransgenic littermates. Using CD4(high) sorting, we isolated the vast majority of Ag-reactive T cells from both strains of mice. Quantitative studies of the CD4(high) populations in transgenic mice following immunization with Talpha146-162 revealed a diminished expansion of cells expressing the canonical TCRBV6 but not other TCRBV gene segments when compared with nontransgenic littermates. In addition, CD4(high) cells from transgenic mice were functionally hyporesponsive to Talpha146-162 in terms of proliferation and cytokine secretion regardless of TCRBV gene segment use. TCR sequence analysis of transgenic Vbeta6(+)CD4(high) cells revealed a reduced frequency of cells expressing a conserved motif within the TCRbeta CDR3. Thus, the canonical Talpha146-162 responsive, Vbeta6(+) population demonstrates both quantitative and qualitative deficits that correlate with an altered TCR repertoire whereas the non-Vbeta6 population in transgenic mice exhibits only a reduction in peptide responsiveness, a qualitative defect. These data demonstrate that discrete autoreactive T cell populations with identical peptide/MHC specificity in Torpedo acetylcholine receptor-alpha-transgenic animals bear distinct tolerance imprints.

Cytotoxic herpes simplex type 2-specific, DQ0602-restricted CD4 T+-cell clones show alloreactivity to DQ0601.

Alloreactivity is one of the most serious problems in organ transplantation. It has been hypothesized that pre-existing alloreactive T cells are actually cross-reacting cells that have been primed by the autologous major histocompatibility complex (MHC) and a specific peptide. CD8+ cytotoxic T lymphocytes that are alloreactive and recognize a virus-peptide that is presented by the autologous MHC have been reported. Here we demonstrate a cross-reactivity that exists between DQ0602 restricted, herpes simplex type 2 VP16 40-50 specific CD4+ T-cell clones, which can be alloreactive to DQ0601. Though most of the DQ0602 restricted T-cell clones we isolated from two different donors were not alloreactive, weakly cross-reacting T-cell clones could be isolated from both donors. Two strongly cross-reacting T-cell clones with high affinity interaction of their T-cell receptor (TCR) with both DQ0602/VP16 40-50 and DQ0601 could be isolated from one donor. DNA sequencing of the a fragment of the Vbeta gene used in their TCR confirmed that these two T cells indeed are two independent clones. These clones are cytotoxic and produce cytokines of a T helper 2-like pattern. Possible implications in a DR-matched transplantation setting are discussed.

Kv1.3 channels are a therapeutic target for T cell-mediated autoimmune diseases.

Autoreactive memory T lymphocytes are implicated in the pathogenesis of autoimmune diseases. Here we demonstrate that disease-associated autoreactive T cells from patients with type-1 diabetes mellitus or rheumatoid arthritis (RA) are mainly CD4+ CCR7- CD45RA- effector memory T cells (T(EM) cells) with elevated Kv1.3 potassium channel expression. In contrast, T cells with other antigen specificities from these patients, or autoreactive T cells from healthy individuals and disease controls, express low levels of Kv1.3 and are predominantly naïve or central-memory (T(CM)) cells. In T(EM) cells, Kv1.3 traffics to the immunological synapse during antigen presentation where it colocalizes with Kvbeta2, SAP97, ZIP, p56(lck), and CD4. Although Kv1.3 inhibitors [ShK(L5)-amide (SL5) and PAP1] do not prevent immunological synapse formation, they suppress Ca2+-signaling, cytokine production, and proliferation of autoantigen-specific T(EM) cells at pharmacologically relevant concentrations while sparing other classes of T cells. Kv1.3 inhibitors ameliorate pristane-induced arthritis in rats and reduce the incidence of experimental autoimmune diabetes in diabetes-prone (DP-BB/W) rats. Repeated dosing with Kv1.3 inhibitors in rats has not revealed systemic toxicity. Further development of Kv1.3 blockers for autoimmune disease therapy is warranted.