Publications by authors named "Nathan Standifer"

23 Publications

  • Page 1 of 1

Safety, Efficacy, and Pharmacodynamics of Tremelimumab Plus Durvalumab for Patients With Unresectable Hepatocellular Carcinoma: Randomized Expansion of a Phase I/II Study.

J Clin Oncol 2021 Sep 22;39(27):2991-3001. Epub 2021 Jul 22.

Memorial Sloan Kettering Cancer Center, New York, NY.

Purpose: This phase I/II study evaluated tremelimumab (anticytotoxic T-lymphocyte-associated antigen-4 monoclonal antibody) and durvalumab (antiprogrammed death ligand-1 monoclonal antibody) as monotherapies and in combination for patients with unresectable hepatocellular carcinoma (HCC), including a novel regimen featuring a single, priming dose of tremelimumab (ClinicalTrials.gov identifier: NCT02519348).

Patients And Methods: Patients with HCC who had progressed on, were intolerant to, or refused sorafenib were randomly assigned to receive T300 + D (tremelimumab 300 mg plus durvalumab 1,500 mg [one dose each during the first cycle] followed by durvalumab 1,500 mg once every 4 weeks), durvalumab monotherapy (1,500 mg once every 4 weeks), tremelimumab monotherapy (750 mg once every 4 weeks [seven doses] and then once every 12 weeks), or T75 + D (tremelimumab 75 mg once every 4 weeks plus durvalumab 1,500 mg once every 4 weeks [four doses] followed by durvalumab 1,500 mg once every 4 weeks). Safety was the primary end point. Secondary end points included objective response rate (ORR) by Response Evaluation Criteria in Solid Tumors v1.1 and overall survival; exploratory end points included circulating lymphocyte profiles.

Results: A total of 332 patients were enrolled (T300 + D, n = 75; durvalumab, n = 104; tremelimumab, n = 69; and T75 + D, n = 84). Tolerability was acceptable across arms, with grade ≥ 3 treatment-related adverse events occurring in 37.8%, 20.8%, 43.5%, and 24.4%, respectively. Confirmed ORRs (95% CI) were 24.0% (14.9 to 35.3), 10.6% (5.4 to 18.1), 7.2% (2.4 to 16.1), and 9.5% (4.2 to 17.9), respectively. An early expansion of CD8+ lymphocytes was associated with response across arms, with highest proliferating CD8+ lymphocyte levels occurring in the T300 + D arm. The median (95% CI) overall survival was 18.7 (10.8 to 27.3), 13.6 (8.7 to 17.6), 15.1 (11.3 to 20.5), and 11.3 (8.4 to 15.0) months in the T300 + D, durvalumab, tremelimumab, and T75 + D arms, respectively.

Conclusion: All regimens were found to be tolerable and clinically active; however, the T300 + D regimen demonstrated the most encouraging benefit-risk profile. The unique pharmacodynamic activity and association with ORR of the T300 + D regimen further support its continued evaluation in HCC.
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http://dx.doi.org/10.1200/JCO.20.03555DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8445563PMC
September 2021

Resistance to durvalumab and durvalumab plus tremelimumab is associated with functional STK11 mutations in non-small-cell lung cancer patients and is reversed by STAT3 knockdown.

Cancer Discov 2021 Jul 6. Epub 2021 Jul 6.

Research and Development, MedImmune LLC.

Mutations in the STK11 (LKB1) gene regulate resistance to PD-1/PD-L1 blockade. This study evaluated this association in patients with nonsquamous non-small-cell lung cancer enrolled in three Phase 1/2 trials. STK11 mutations were associated with resistance to the anti-PD-L1 antibody durvalumab (alone/with the anti-CTLA-4 antibody tremelimumab) independently of KRAS mutational status, highlighting STK11 as a potential driver of resistance to checkpoint blockade. Retrospective assessments of tumor tissue, whole blood and serum revealed a unique immune phenotype in patients with STK11 mutations, with increased expression of markers associated with neutrophils (i.e. CXCL2, IL6), Th17 contexture (i.e. IL17A) and immune checkpoints. Associated changes were observed in the periphery. Reduction of STAT3 in the tumor microenvironment using an antisense oligonucleotide reversed immunotherapy resistance in preclinical STK11 knockout models. These results suggest that STK11 mutations may hinder response to checkpoint blockade through mechanisms including suppressive myeloid cell biology, which could be reversed by STAT3-targeted therapy.
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http://dx.doi.org/10.1158/2159-8290.CD-20-1543DOI Listing
July 2021

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

Cancer Immunol Immunother 2021 Jul 9;70(7):2095-2102. Epub 2021 Jan 9.

Department of Medicine, University of California San Francisco, San Francisco, CA, USA.

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.
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http://dx.doi.org/10.1007/s00262-020-02833-zDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8195930PMC
July 2021

Best practices for optimization and validation of flow cytometry-based receptor occupancy assays.

Cytometry B Clin Cytom 2021 01 1;100(1):63-71. Epub 2020 Dec 1.

Flow Contract Site Laboratory, Bothell, Washington, USA.

In the development of therapeutic compounds that bind cell surface molecules, it is critical to demonstrate the extent to which the drug engages its target. For cell-associated targets, flow cytometry is well-suited to monitor drug-to-target engagement through receptor occupancy assays (ROA). The technology allows for the identification of specific cell subsets within heterogeneous populations and the detection of nonabundant cellular antigens. There are numerous challenges in the design, development, and implementation of robust ROA. Among the most difficult challenges are situations where there is receptor modulation or when the target-antigen is expressed at low levels. When the therapeutic molecules are bi-specific and bind multiple targets, these challenges are increased. This manuscript discusses the challenges and proposes best practices for designing, optimizing, and validating ROA.
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http://dx.doi.org/10.1002/cyto.b.21970DOI Listing
January 2021

Safety and Clinical Activity of MEDI1873, a Novel GITR Agonist, in Advanced Solid Tumors.

Clin Cancer Res 2020 12 4;26(23):6196-6203. Epub 2020 Sep 4.

Fox Chase Cancer Center, Philadelphia, Pennsylvania.

Purpose: The safety and preliminary efficacy of MEDI1873, an agonistic IgG1 fusion protein targeting glucocorticoid-induced TNF receptor-related protein (GITR), were evaluated in an open-label, first-in-human, phase I, dose escalation study in previously treated patients with advanced solid tumors.

Patients And Methods: Two single-patient cohorts at 1.5 and 3 mg i.v. were followed by 3+3 dose escalation in six cohorts at 7.5, 25, 75, 250, 500, and 750 mg, all every 2 weeks, for up to 52 weeks. Primary endpoints were safety and tolerability, dose-limiting toxicities (DLT), and MTD. Secondary endpoints included antitumor activity, pharmacokinetics, immunogenicity, and pharmacodynamics.

Results: Forty patients received MEDI1873. Three experienced DLTs: grade 3 worsening tumor pain (250 mg); grade 3 nausea, vomiting, and headache (500 mg); and grade 3 non-ST segment elevation myocardial infarction (750 mg). An MTD was not reached and treatment was well tolerated up to 500 mg. Most common treatment-related adverse events were headache (25%), infusion-related reaction (17.5%), and decreased appetite (17.5%). MEDI1873 exposure was dose proportional. Antidrug-antibody incidence was low. MEDI1873 increased peripheral CD4 effector memory T-cell proliferation as well as cytokines associated with effector T-cell activation at dose levels ≥75 mg. The best response was stable disease (SD) in 17 patients (42.5%), including 1 unconfirmed partial response. Eight patients (20.0%) had SD ≥24 weeks.

Conclusions: MEDI1873 showed acceptable safety up to 500 mg i.v. every 2 weeks with pharmacodynamics activity, and prolonged SD in some patients. However, further development is not planned because of lack of demonstrated tumor response.
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http://dx.doi.org/10.1158/1078-0432.CCR-20-0452DOI Listing
December 2020

Population pharmacokinetics, efficacy, and safety of moxetumomab pasudotox in patients with relapsed or refractory hairy cell leukaemia.

Br J Clin Pharmacol 2020 07 16;86(7):1367-1376. Epub 2020 Mar 16.

AstraZeneca, Gaithersburg, MD, USA.

Aims: To characterize the pharmacokinetics (PK) of moxetumomab pasudotox, an anti-CD22 recombinant immunotoxin, in adults with relapsed or refractory hairy cell leukaemia, we examined data from a phase 1 study (Study 1001; n = 49) and from the pivotal clinical study (Study 1053; n = 74).

Methods: Data from both studies were pooled (n = 123) to develop a population PK model. Covariates included demographics, disease state, liver and kidney function, prior treatment, and antidrug antibodies (ADAs). Exposure-response and exposure-safety were analysed separately by study. A 1-compartment model with linear elimination from the central compartment and 2 clearance (CL) rates was developed.

Results: Moxetumomab pasudotox was cleared more rapidly after cycle 1, day 1 (CL = 24.7 L/h) than subsequently (CL = 3.76 L/h), with high interindividual variability (116 and 109%, respectively). In Study 1053, patients with ADA titres >10 240 showed ~4-fold increase in CL. Higher exposures (≥median) were related to higher response rates, capillary leak syndrome and increased creatinine (Study 1053 only), or grade ≥3 adverse events (Study 1001 only). Clinical benefits were still observed in patients with lower exposure or high ADA titres.

Conclusion: Despite a high incidence of immunogenicity with increased clearance, moxetumomab pasudotox demonstrated efficacy in hairy cell leukaemia.
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http://dx.doi.org/10.1111/bcp.14250DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7318999PMC
July 2020

Recruiting the Immune System Against Disease: Lessons for Clinical and Systems Pharmacology.

CPT Pharmacometrics Syst Pharmacol 2019 07 24;8(7):436-439. Epub 2019 May 24.

Pfizer, Andover, Massachusetts, USA.

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http://dx.doi.org/10.1002/psp4.12416DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6656934PMC
July 2019

Moxetumomab pasudotox in relapsed/refractory hairy cell leukemia.

Leukemia 2018 08 20;32(8):1768-1777. Epub 2018 Jul 20.

City of Hope National Medical Center, Duarte, CA, USA.

This is a pivotal, multicenter, open-label study of moxetumomab pasudotox, a recombinant CD22-targeting immunotoxin, in hairy cell leukemia (HCL), a rare B cell malignancy with high CD22 expression. The study enrolled patients with relapsed/refractory HCL who had ≥2 prior systemic therapies, including ≥1 purine nucleoside analog. Patients received moxetumomab pasudotox 40 µg/kg intravenously on days 1, 3, and 5 every 28 days for ≤6 cycles. Blinded independent central review determined disease response and minimal residual disease (MRD) status. Among 80 patients (79% males; median age, 60.0 years), durable complete response (CR) rate was 30%, CR rate was 41%, and objective response rate (CR and partial response) was 75%; 64 patients (80%) achieved hematologic remission. Among complete responders, 27 (85%) achieved MRD negativity by immunohistochemistry. The most frequent adverse events (AEs) were peripheral edema (39%), nausea (35%), fatigue (34%), and headache (33%). Treatment-related serious AEs of hemolytic uremic syndrome (7.5%) and capillary leak syndrome (5%) were reversible and generally manageable with supportive care and treatment discontinuation (6 patients; 7.5%). Moxetumomab pasudotox treatment achieved a high rate of independently assessed durable response and MRD eradication in heavily pretreated patients with HCL, with acceptable tolerability.
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http://dx.doi.org/10.1038/s41375-018-0210-1DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6087717PMC
August 2018

Evaluation of assay interference and interpretation of CXCR4 receptor occupancy results in a preclinical study with MEDI3185, a fully human antibody to CXCR4.

Cytometry B Clin Cytom 2016 Mar 15;90(2):209-19. Epub 2015 Dec 15.

Clinical Pharmacology & DMPK, Medimmune, LLC, Mountain View, California, 94043.

Background: Receptor occupancy (RO) assays provide a means to measure the direct interaction of therapeutics with their cell surface targets. Free receptor assays quantify cell-surface receptors not bound by a therapeutic while total receptor assays quantify the amount of target on the cell surface.

Methods: We developed both a flow cytometry-based free RO assay to detect free surface CXCR4, and a total surface CXCR4 assay. In an effort to evaluate potential displacement interference, we performed in vitro experiments to compare on-cell affinity with the IC50 values from in vitro and in vivo from the free CXCR4 assay. We determined free and total surface CXCR4 on circulating blood cells in cynomolgus monkeys dosed with MEDI3185, a fully human monoclonal antibody to CXCR4.

Results: We devised an approach to evaluate displacement interference during assay development and showed that our free assay demonstrated little to no displacement interference. After dosing cynomolgus monkeys with MEDI3185, we observed dose-dependence in the magnitude and duration of receptor occupancy and found CXCR4 to increase on lymphocytes, monocytes, and granulocytes. In a multiple dose study, we observed time points where surface CXCR4 appeared fully occupied but MEDI3185 was not detectable in serum. These paradoxical results represented a type of assay interference, and by comparing pharmacokinetic, ADA and total CXCR4 results, the most likely reason for the free CXCR4 results was the emergence of neutralizing anti-drug antibodies (ADA). The total CXCR4 assay was unaffected by ADA and provided a reliable marker of target modulation in both in vivo studies.
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http://dx.doi.org/10.1002/cyto.b.21327DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5064743PMC
March 2016

Receptor occupancy assessment by flow cytometry as a pharmacodynamic biomarker in biopharmaceutical development.

Cytometry B Clin Cytom 2016 Mar 31;90(2):117-27. Epub 2015 Jul 31.

Department of Clinical Pharmacology and DMPK, Medimmune, LLC, Mountain View, California, 94043.

Receptor occupancy (RO) assays are designed to quantify the binding of therapeutics to their targets on the cell surface and are frequently used to generate pharmacodynamic (PD) biomarker data in nonclinical and clinical studies of biopharmaceuticals. When combined with the pharmacokinetic (PK) profile, RO data can establish PKPD relationships, which are crucial for informing dose decisions. RO is commonly measured by flow cytometry on fresh blood specimens and is subject to numerous technical and logistical challenges. To ensure that reliable and high quality results are generated from RO assays, careful assay design, key reagent characterization, data normalization/reporting, and thorough planning for implementation are of critical importance during development. In this article, the authors share their experiences and perspectives in these areas and discuss challenges and potential solutions when developing and implementing a flow cytometry-based RO method in support of biopharmaceutical drug development.
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http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5042057PMC
http://dx.doi.org/10.1002/cyto.b.21259DOI Listing
March 2016

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

PLoS One 2012 12;7(1):e29949. Epub 2012 Jan 12.

Translational Research Program, Benaroya Research Institute, Seattle, Washington, United States of America.

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.
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http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0029949PLOS
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3257230PMC
May 2012

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

Proc Natl Acad Sci U S A 2011 May 25;108(19):7938-43. Epub 2011 Apr 25.

Benaroya Research Institute at Virginia Mason, Seattle, WA 98101, USA.

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.
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http://dx.doi.org/10.1073/pnas.1017360108DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3093524PMC
May 2011

Short-term IL-1beta blockade reduces monocyte CD11b integrin expression in an IL-8 dependent fashion in patients with type 1 diabetes.

Clin Immunol 2010 Aug 18;136(2):170-3. Epub 2010 May 18.

Benaroya Research Institute, Seattle, WA, USA.

Objective: Interleukin 1-beta (IL-1beta) is a major inflammatory cytokine. Blockade of the IL-1beta pathway is therapeutically efficacious in type 2 diabetes, but the mechanistic effects on the immune system are incompletely understood.

Research Design: We administered an IL-1 receptor antagonist, anakinra, to 7 type 1 diabetes patients in order to investigate the immunologic and metabolic effects of this drug. Mechanistic assays were performed before and after drug administration.

Results: A novel signature was observed, with reduced serum interleukin 8 (IL-8) levels and reduced CD11b integrin expression on monocytes associated with increased CXCR1 expression.

Conclusions: This set of linked phenotypes suggests that blockade of the IL-1beta pathway results in the reduced ability of mononuclear cells to traffic to sites of inflammation. Mechanistic studies from large scale trials using IL-1 blockade in type 1 diabetes should focus on changes in monocyte trafficking and the IL-8 pathway.
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http://dx.doi.org/10.1016/j.clim.2010.04.009DOI Listing
August 2010

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

J Immunol 2010 Jun 30;184(11):6067-75. Epub 2010 Apr 30.

Department of Cellular and Structural Biology, The University of Texas Health Science Center at San Antonio, San Antonio, TX 78229-3900, USA.

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.
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http://dx.doi.org/10.4049/jimmunol.0901618DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2895814PMC
June 2010

Recurrence of type 1 diabetes after simultaneous pancreas-kidney transplantation, despite immunosuppression, is associated with autoantibodies and pathogenic autoreactive CD4 T-cells.

Diabetes 2010 Apr 19;59(4):947-57. Epub 2010 Jan 19.

Diabetes Research Institute, Leonard Miller School of Medicine, University of Miami, Miami, Florida, USA.

Objective: To investigate if recurrent autoimmunity explained hyperglycemia and C-peptide loss in three immunosuppressed simultaneous pancreas-kidney (SPK) transplant recipients.

Research Design And Methods: We monitored autoantibodies and autoreactive T-cells (using tetramers) and performed biopsy. The function of autoreactive T-cells was studied with in vitro and in vivo assays.

Results: Autoantibodies were present pretransplant and persisted on follow-up in one patient. They appeared years after transplantation but before the development of hyperglycemia in the remaining patients. Pancreas transplant biopsies were taken within approximately 1 year from hyperglycemia recurrence and revealed beta-cell loss and insulitis. We studied autoreactive T-cells from the time of biopsy and repeatedly demonstrated their presence on further follow-up, together with autoantibodies. Treatment with T-cell-directed therapies (thymoglobulin and daclizumab, all patients), alone or with the addition of B-cell-directed therapy (rituximab, two patients), nonspecifically depleted T-cells and was associated with C-peptide secretion for >1 year. Autoreactive T-cells with the same autoantigen specificity and conserved T-cell receptor later reappeared with further C-peptide loss over the next 2 years. Purified autoreactive CD4 T-cells from two patients were cotransplanted with HLA-mismatched human islets into immunodeficient mice. Grafts showed beta-cell loss in mice receiving autoreactive T-cells but not control T-cells.

Conclusions: We demonstrate the cardinal features of recurrent autoimmunity in three such patients, including the reappearance of CD4 T-cells capable of mediating beta-cell destruction. Markers of autoimmunity can help diagnose this underappreciated cause of graft loss. Immune monitoring during therapy showed that autoimmunity was not resolved by the immunosuppressive agents used.
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http://dx.doi.org/10.2337/db09-0498DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2844842PMC
April 2010

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

J Virol 2010 Apr 13;84(7):3312-9. Epub 2010 Jan 13.

Benaroya Research Institute at Virginia Mason, Seattle, WA 98101, USA.

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.
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http://dx.doi.org/10.1128/JVI.02226-09DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2838145PMC
April 2010

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

Clin Immunol 2009 Sep 23;132(3):312-20. Epub 2009 May 23.

Benaroya Research Institute at Virginia Mason, Seattle, WA 98101, USA.

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.
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http://dx.doi.org/10.1016/j.clim.2009.04.013DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2720757PMC
September 2009

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

J Immunol 2007 Mar;178(6):3544-50

Department of Microbiology and Immunology, University of Texas Health Science Center, San Antonio, TX 78229, USA.

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.
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http://dx.doi.org/10.4049/jimmunol.178.6.3544DOI Listing
March 2007

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

Proc Natl Acad Sci U S A 2006 Nov 6;103(46):17414-9. Epub 2006 Nov 6.

Department of Physiology and Biophysics, University of California, Irvine, CA 92697, USA.

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.
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http://dx.doi.org/10.1073/pnas.0605136103DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC1859943PMC
November 2006

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

Diabetes 2006 Nov;55(11):3068-74

Department of Pathology and Laboratory Medicine, Child and Family Research Institute, University of British Columbia and British Columbia Children's Hospital, 4480 Oak St., Vancouver, British Columbia V6H 3V4, Canada.

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.
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http://dx.doi.org/10.2337/db06-0065DOI Listing
November 2006

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

Diabetes 2006 Nov;55(11):3061-7

Benaroya Research Institute at Virginia Mason, 1201 Ninth Ave., Room 260, Seattle WA, 98101, USA.

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.
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http://dx.doi.org/10.2337/db06-0066DOI Listing
November 2006

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

Immunology 2006 Mar;117(3):350-7

Research Institute at Virginia Mason, WA 98101, USA.

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.
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http://dx.doi.org/10.1111/j.1365-2567.2005.02308.xDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC1782233PMC
March 2006

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

J Neuroimmunol 2003 Dec;145(1-2):68-76

Department of Microbiology and Immunology, University of Texas Health Science Center at San Antonio, 7703 Floyd Curl Dr, San Antonio, TX 78229-3900, USA.

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.
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http://dx.doi.org/10.1016/j.jneuroim.2003.09.007DOI Listing
December 2003
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