Teresa P. DiLorenzo

Identification of the β cell antigen targeted by a prevalent population of pathogenic CD8+ T cells in autoimmune diabetes

Type 1 diabetes is an autoimmune disease in which autoreactive T cells attack and destroy the insulin-producing pancreatic β cells. CD8+ T cells are essential for this β cell destruction, yet their specific antigenic targets are largely unknown. Here, we reveal that the autoantigen targeted by a prevalent population of pathogenic CD8+ T cells in nonobese diabetic mice is islet-specific glucose-6-phosphatase catalytic subunit-related protein (IGRP). Through tetramer technology, IGRP-reactive T cells are readily detected in islets and peripheral blood directly ex vivo. The human IGRP gene maps to a diabetes susceptibility locus, suggesting that IGRP also may be an antigen for pathogenic T cells in human type 1 diabetes and, thus, a new, potential target for diagnostic and therapeutic approaches.

Identification of a CD8 T Cell That Can Independently Mediate Autoimmune Diabetes Development in the Complete Absence of CD4 T Cell Helper Functions

Previous work has indicated that an important component for the initiation of autoimmune insulin-dependent diabetes mellitus (IDDM) in the NOD mouse model entails MHC class I-restricted CD8 T cell responses against pancreatic β cell Ags. However, unless previously activated in vitro, such CD8 T cells have previously been thought to require helper functions provided by MHC class II-restricted CD4 T cells to exert their full diabetogenic effects. In this study, we show that IDDM development is greatly accelerated in a stock of NOD mice expressing TCR transgenes derived from a MHC class I-restricted CD8 T cell clone (designated AI4) previously found to contribute to the earliest preclinical stages of pancreatic β cell destruction. Importantly, these TCR transgenic NOD mice (designated NOD.AI4αβ Tg) continued to develop IDDM at a greatly accelerated rate when residual CD4 helper T cells were eliminated by introduction of the scid mutation or a functionally inactivated CD4 allele. In a previously described stock of NOD mice expressing TCR transgenes derived from another MHC class I-restricted β cell autoreactive T cell clone, IDDM development was retarded by elimination of residual CD4 T cells. Hence, there is variability in the helper dependence of CD8 T cells contributing to the development of autoimmune IDDM. The AI4 clonotype represents the first CD8 T cell with a demonstrated ability to progress from a naive to functionally activated state and rapidly mediate autoimmune IDDM development in the complete absence of CD4 T cell helper functions.

Individual Nonobese Diabetic Mice Exhibit Unique Patterns of CD8+ T Cell Reactivity to Three Islet Antigens, Including the Newly Identified Widely Expressed Dystrophia Myotonica Kinase

Spontaneous autoimmune diabetes development in NOD mice requires both CD8+ and CD4+ T cells. Three pathogenic CD8+ T cell populations (represented by the G9C8, 8.3, and AI4 clones) have been described. Although the Ags for G9C8 and 8.3 are known to be insulin and islet-specific glucose-6-phosphatase catalytic subunit-related protein, respectively, only mimotope peptides had previously been identified for AI4. In this study, we used peptide/MHC tetramers to detect and quantify these three pathogenic populations among β cell-reactive T cells cultured from islets of individual NOD mice. Even within age-matched groups, each individual mouse exhibited a unique distribution of β cell-reactive CD8+ T cells, both in terms of the number of tetramer-staining populations and the relative proportion of each population in the islet infiltrate. Thus, the inflammatory process in each individual follows its own distinctive course. Screening of a combinatorial peptide library in positional scanning format led to the identification of a peptide derived from dystrophia myotonica kinase (DMK) that is recognized by AI4-like T cells. Importantly, the antigenic peptide is naturally processed and presented by DMK-transfected cells. DMK is a widely expressed protein that is nonetheless the target of a β cell-specific autoimmune response.

Selective delivery of beta cell antigen to dendritic cells in vivo leads to deletion and tolerance of autoreactive CD8+ T cells in NOD mice.

Type 1 diabetes (T1D) is an autoimmune disease resulting from defects in central and peripheral tolerance and characterized by T cell-mediated destruction of islet β cells. Cytotoxic CD8+ T cells, reactive to β cell antigens, are required for T1D development in the NOD mouse model of the disease, and CD8+ T cells specific for β cell antigens can be detected in the peripheral blood of T1D patients. It has been evident that in nonautoimmune-prone mice, dendritic cells (DCs) present model antigens in a tolerogenic manner in the steady state, e.g., in the absence of infection, and cause T cells to proliferate initially but then to be deleted or rendered unresponsive. However, this fundamental concept has not been evaluated in the setting of a spontaneous autoimmune disease. To do so, we delivered a mimotope peptide, recognized by the diabetogenic CD8+ T cell clone AI4, to DCs in NOD mice via the endocytic receptor DEC-205. Proliferation of transferred antigen-specific T cells was initially observed, but this was followed by deletion. Tolerance was achieved because rechallenge of mice with the mimotope peptide in adjuvant did not induce an immune response. Thus, targeting of DCs with β cell antigens leads to deletion of autoreactive CD8+ T cells even in the context of ongoing autoimmunity in NOD mice with known tolerance defects. Our results provide support for the development of DC targeting of self antigens for treatment of chronic T cell-mediated autoimmune diseases.

Structural genomics of protein phosphatases.

The New York SGX Research Center for Structural Genomics (NYSGXRC) of the NIGMS Protein Structure Initiative (PSI) has applied its high-throughput X-ray crystallographic structure determination platform to systematic studies of all human protein phosphatases and protein phosphatases from biomedically-relevant pathogens. To date, the NYSGXRC has determined structures of 21 distinct protein phosphatases: 14 from human, 2 from mouse, 2 from the pathogen Toxoplasma gondii, 1 from Trypanosoma brucei, the parasite responsible for African sleeping sickness, and 2 from the principal mosquito vector of malaria in Africa, Anopheles gambiae. These structures provide insights into both normal and pathophysiologic processes, including transcriptional regulation, regulation of major signaling pathways, neural development, and type 1 diabetes. In conjunction with the contributions of other international structural genomics consortia, these efforts promise to provide an unprecedented database and materials repository for structure-guided experimental and computational discovery of inhibitors for all classes of protein phosphatases.

Developmental control of CD8+ T cell–avidity maturation in autoimmune diabetes

The progression of immune responses is generally associated with an increase in the overall avidity of antigen-specific T cell populations for peptide-MHC. This is thought to result from preferential expansion of high-avidity clonotypes at the expense of their low-avidity counterparts. Since T cell antigen-receptor genes do not mutate, it is puzzling that high-avidity clonotypes do not predominate from the outset. Here we provide a developmental basis for this phenomenon in the context of autoimmunity. We have carried out comprehensive studies of the diabetogenic CD8 T cell population that targets residues 206-214 of the beta cell antigen islet-specific glucose-6-phosphatase catalytic subunit-related protein (IGRP(206-214)) and undergoes avidity maturation as disease progresses. We find that the succession of IGRP(206-214)-specific clonotypes with increasing avidities during the progression of islet inflammation to overt diabetes in nonobese diabetic mice is fueled by autoimmune inflammation but opposed by systemic tolerance. As expected, naive high-avidity IGRP(206-214)-specific T cells respond more efficiently to antigen and are significantly more diabetogenic than their intermediate- or low-avidity counterparts. However, central and peripheral tolerance selectively limit the contribution of these high-avidity T cells to the earliest stages of disease without abrogating their ability to progressively accumulate in inflamed islets and kill beta cells. These results illustrate the way in which incomplete deletion of autoreactive T cell populations of relatively high avidity can contribute to the development of pathogenic autoimmunity in the periphery.

HLA-A*0201-Restricted T Cells from Humanized NOD Mice Recognize Autoantigens of Potential Clinical Relevance to Type 1 Diabetes

In both humans and NOD mice, particular MHC genes are primary contributors to development of the autoreactive CD4+ and CD8+ T cell responses against pancreatic β cells that cause type 1 diabetes (T1D). Association studies have suggested, but not proved, that the HLA-A*0201 MHC class I variant is an important contributor to T1D in humans. In this study, we show that transgenic expression in NOD mice of HLA-A*0201, in the absence of murine class I MHC molecules, is sufficient to mediate autoreactive CD8+ T cell responses contributing to T1D development. CD8+ T cells from the transgenic mice are cytotoxic to murine and human HLA-A*0201-positive islet cells. Hence, the murine and human islets must present one or more peptides in common. Islet-specific glucose-6-phosphatase catalytic subunit-related protein (IGRP) is one of several important T1D autoantigens in standard NOD mice. Three IGRP-derived peptides were identified as targets of diabetogenic HLA-A*0201-restricted T cells in our NOD transgenic stock. Collectively, these results indicate the utility of humanized HLA-A*0201-expressing NOD mice in the identification of T cells and autoantigens of potential relevance to human T1D. In particular, the identified antigenic peptides represent promising tools to explore the potential importance of IGRP in the development of human T1D.

A possible role for human papillomaviruses in head and neck cancer

Human papillomaviruses (HPVs) cause benign tumors in the respiratory tract. Mounting evidence suggests that they also play a role in the etiology of a subset of head and neck cancers. Carcinomas in patients with a history of recurrent respiratory papillomatosis clearly are caused by persisting HPV interacting with one or more carcinogenic agents. Verrucous carcinomas of the oral cavity, tonsillar and tongue carcinomas are strongly linked with HPVs, based on molecular epidemiologic data. Tonsillar cancers have been shown to express HPV RNA, presumed necessary to induce and maintain a carcinoma, supporting a viral etiology. This paper reviews the molecular and cellular basis for considering HPVs as causttive agents of cancer, and reviews the literature that considers the possible role of HPVs in head and neck cancer.

Improved Outcomes in NOD Mice Treated with a Novel Th2 Cytokine-Biasing NKT Cell Activator

Activation of CD1d-restricted invariant NKT (iNKT) cells by α-galactosylceramide (αGalCer) significantly suppresses development of diabetes in NOD mice. The mechanisms of this protective effect are complex, involving both Th1 and Th2 cytokines and a network of regulatory cells including tolerogenic dendritic cells. In the current study, we evaluated a newly described synthetic αGalCer analog (C20:2) that elicits a Th2-biased cytokine response for its impact on disease progression and immunopathology in NOD mice. Treatment of NOD mice with αGalCer C20:2 significantly delayed and reduced the incidence of diabetes. This was associated with significant suppression of the late progression of insulitis, reduced infiltration of islets by autoreactive CD8+ T cells, and prevention of progressive disease-related changes in relative proportions of different subsets of dendritic cells in the draining pancreatic lymph nodes. Multiple favorable effects observed with αGalCer C20:2 were significantly more pronounced than those seen in direct comparisons with a closely related analog of αGalCer that stimulated a more mixed pattern of Th1 and Th2 cytokine secretion. Unlike a previously reported Th2-skewing murine iNKT cell agonist, the αGalCer C20:2 analog was strongly stimulatory for human iNKT cells and thus warrants further examination as a potential immunomodulatory agent for human disease.

Lentiviral vectors encoding human immunodeficiency virus type 1 (HIV-1)-specific T-cell receptor genes efficiently convert peripheral blood CD8 T lymphocytes into cytotoxic T lymphocytes with potent in vitro and in vivo HIV-1-specific inhibitory activity.

ABSTRACT The human immunodeficiency virus type 1 (HIV-1)-specific CD8 cytotoxic T-lymphocyte (CTL) response plays a critical role in controlling HIV-1 replication. Augmenting this response should enhance control of HIV-1 replication and stabilize or improve the clinical course of the disease. Although cytomegalovirus (CMV) or Epstein-Barr virus (EBV) infection in immunocompromised patients can be treated by adoptive transfer of ex vivo-expanded CMV- or EBV-specific CTLs, adoptive transfer of ex vivo-expanded, autologous HIV-1-specific CTLs had minimal effects on HIV-1 replication, likely a consequence of the inherently compromised qualitative function of HIV-1-specific CTLs derived from HIV-1-infected individuals. We hypothesized that this limitation could be circumvented by using as an alternative source of HIV-1-specific CTLs, autologous peripheral CD8+ T lymphocytes whose antigen specificity is redirected by transduction with lentiviral vectors encoding HIV-1-specific T-cell receptor (TCR) α and β chains, an approach used successfully in cancer therapy. To efficiently convert peripheral CD8 lymphocytes into HIV-1-specific CTLs that potently suppress in vivo HIV-1 replication, we constructed lentiviral vectors encoding the HIV-1-specific TCR α and TCR β chains cloned from a CTL clone specific for an HIV Gag epitope, SL9, as a single transcript linked with a self-cleaving peptide. We demonstrated that transduction with this lentiviral vector efficiently converted primary human CD8 lymphocytes into HIV-1-specific CTLs with potent in vitro and in vivo HIV-1-specific activity. Using lentiviral vectors encoding an HIV-1-specific TCR to transform peripheral CD8 lymphocytes into HIV-1-specific CTLs with defined specificities represents a new immunotherapeutic approach to augment the HIV-1-specific immunity of infected patients.