An Overview of our Research Program
Dr. Hafler is a clinical neurologist who is trained experimentally as an immunologist. His research characterizes human immune responses to autoantigens, with the aim of developing an understanding of the underlying loss of immune regulation that leads to human autoimmune disease and identifying the genetic variations associated with human inflammatory immune responses. As a clinician actively engaged in the development of clinical trials, he is an instrumental leader in the translation of experimental findings to therapies for human diseases.
Dr. Hafler was the first to develop techniques that defined responses to self-antigens in humans, characterizing the human immune responses to the encephalitogenic protein, myelin basic protein (MBP). These efforts have led to the development of potential immunotherapeutic approaches for the treatment of human autoimmune disease (Nature 346:183, 1990). This paper demonstrated that human autoimmune disease was not due simply to central tolerance with deletion of autoreactive T cells, but instead indicated that some mechanism must exist to regulate circulating autoreactive T cells. Dr. Hafler went on to examine the structural recognition of the immunodominant MBPp85-99 peptide (J. Exp. Med. 179:279, 1994). Determination of the T cell receptor and MHC contact residues for the MBPp85-99 peptide was confirmed by x-ray crystallography of the peptide/MHC complex by Dr. Kai Wucherpfennig, a former post-doctoral fellow at Harvard Medical School. These experiments were the foundation of a series of experiments described below where structural alterations of the MBPp85-99 were used to alter the immune response and to begin defining the bases of molecular mimicry. Based on these experiments, clinical trials using altered peptide ligands of MBPp85-99 are in phase II studies. Dr. Hafler continued to work in the field of structural immunology, demonstrating that complementary mutations in an antigenic peptide allow for cross-reactivity of autoreactive T cell clones (Proc. Natl. Acad. Sci. 93:15317, 1996). More recently, he discovered that allelic variations of MHC alters peptide ligands to induce proliferation without cytotoxicity of CD8+ T cells (J Exp Med198:99, 2003). In addition, his group, in collaboration with J. Kappler and B. Huber was the first to use Class II MHC tetramers to directly identify, ex vivo, antigen reactive T cells in an immune compartment or peripheral blood (Proc Natl Acad Sci USA 97, 11433, 2000). Besides these investigation of the structural basis for recognition of self-antigens, Dr. Hafler has investigated functional consequences of T cell recognition of self-antigen, demonstrating the modulation of cytokine patterns of human autoreactive T cell clones by a single amino acid substitution of their peptide ligand(Immunity 2:373-380, 1995). This led to extensive investigation of the drug Copaxone, an FDA approved drug for MHC that acts like an MHC agonist, demonstrating that the drug acted as a “universal antigen”, and could induce the proliferation of resting peripheral blood T cells; treatment induced a profound Th2 response with more degenerate T cell receptors, leading to the hypothesis that these cross-reactive Th2 cells migrated into the CNS where they induce bystander suppression by recognition of an APL like antigen (J Clin Invest 105, 967, 2000).
Dr. Hafler is perhaps best known for his work in the field of MS research. In the early 1980’s, Dr. Hafler was the first to provide evidence for an activated peripheral immune system in patients with MS with the use of the anti-VLA and anti-CD26 mAbs (N Engl J Med 312, 1405, 1985) demonstrating that CD45RO memory T cells trafficked into the CNS. He was among the first to apply the techniques of T cell cloning to human disease, demonstrating the presence of oligoclonal T cells (J Exp Med 167, 1625, 1988, J Exp Med 175, 993, 1992), and gd T cells in the CSF and brain of patients with the MS (Proc Natl Acad Sci USA 89, 4588, 1992).
Having demonstrated that myelin reactive T cells are present in the circulation of patients with MS and normal subjects Dr. Hafler went on to demonstrate that the myelin reactive T cells are activated in patients with MS while in normal subjects, they are in a resting stage, reflecting what is observed in the EAE model (J. Exp. Med. 179:973 1994, and J. Exp. Med., 185:1585, 1997, J Immunol 160, 1532, 1998). His investigation of the CNS of brain tissue from patients with MS was the first to show increased expression of the B7 costimulatory molecules and IL-12 in an inflamed autoimmune compartment (J Exp Med182, 1985, 1995). In total, these studies provided evidence that activated, autoreactive T cells, activated in the CNS are part of the underlying cause for the multiple sclerosis. In addition to his work in MS, Dr. Hafler has made significant contributions in the field of human immunology by investigation other autoimmune diseases. He recently demonstrated that GAD65-reactive T cells are also activated in patients with autoimmune type 1 diabetes(J Clin Invest 109, 895, 2002). The broad scope of work in both basic human immunology, and in different inflammatory human diseases is a unique feature of Dr. Hafler’s contribution to the field.
A major part of the work by Dr. Hafler has been in the understanding of the regulation of T cell responses to autoantigens. In the early 1980s, it was shown that addition of peptide antigen to T cell cultures resulted in a lack of responsiveness to the antigen. This led to fundamental work examining the mechanism of this non-responsiveness, and the demonstration that this form of T cell anergy was related to presentation of antigen in a T cell-T cell interaction. This anergy was shown to be due to early signaling defects in the human T cells that were anergized by T cell presentation of autoantigen and that the anergy required cell to cell contact. In subsequent investigations, it was shown that direct T-T cell contact is required, and individual T cells can not self-present peptide antigen T cell presentation of antigen requires cell-to-cell contact for proliferation and anergy induction: differential MHC requirements for superantigen and autoantigen (J. Immunol. 151:649, 1993). In addition to this basic work on T–T interactions, Dr. Hafler has examined the consequences blocking B7/CTLA-4 interactions, demonstrating the paradoxical inhibition of T cell function in response to CTLA-4 blockade depending upon the strength of signal through the TCR, (Nat Med 6, 211, 2000).
Dr. Hafler has had a long interest in understanding the immune response to microbial diseases, including Lyme Disease and HTLV-I associated myelopathy. He determined the structural basis for T cell recognition of the immunodominant epitope of the HTLV-I virus, taxp11-19, demonstrating that the tyrosine at position 15 was a critical T cell receptor contact residue and alteration of this residue from a tyrosine to alanine resulted in a peptide that could differentially stimulate T cell clones to be cytotoxic but not be induced to secrete cytokines, proliferate or autophosphorylate the p56lck CD4 associated molecule (Proc. Natl. Acad. Sci. (USA) 92:4036, 1995). This was among the first demonstrations that cytotoxicity can be dissociated from proliferation, which has been confirmed in murine models of T cell antigen recognition. The determination of the T cell receptor and the contact residues for these peptides were confirmed by the late Don Wiley in his x-ray crystallography of the T cell receptor MHC HTLV-I tax 11-19 crystal structure.
Continuing on the question of how autoreactive T cells are regulated, Dr. Hafler in collaboration with J. Strominger found a functional alteration in the homologous NK 1.1 like Va24 JaQ invariant T cells in identical twin pairs discordant for diabetes. Specifically, the Va24 JaQ T cells no longer secreted IL-4 in diabetics, whereas discordant twins that do not have diabetes exhibit significant secretion of both IL-4 and g-IFN. These were among the first data to show an alteration of these potentially regulatory T cells in human autoimmune disease (Nature, 391, 177, 1998). More recently, Dr. Hafler developed a method to examine regulatory CD4+CD25+ T cells in humans, recognizing that it was the CD4+CD25high T cells represented the T regulatory T cells (J Immunol 169, 6210, 2002). More importantly, he was the first to demonstrate a defect in the function of these regulatory cells in patients with MS (J Exp Med 199, 971, 2004).
Besides his work in basic human immunology and clinical immunology related to human disease, as a neurologist, Dr. Hafler has been involved in the translation of findings at the bench to clinical trials. He and Dr. Weiner were the first to infuse anti-T cell mAbs into patients with autoimmune disease (J Immunol 141, 131, 1988). He has has been extensively involved in human clinical trials, and is presently engaged in the investigations with CTLA-4 Ig fusion proteins and Rapamycin in patients with MS.
In recent years, Dr. Hafler performed a sabbatical with Eric Lander at the Whitehead Institute at MIT where he co-established the International MS Genetic Consortium. He led, along with his MIT colleagues, the first human whole genome admixture study (Am J Hum Genet 74, 979, 2004) of patients with MS.
Dr. Hafler has played a major leadership role in the field of human immunology. As co-founder of the Federation of Clinical Immunology Societies, he was one of the organizers of the International Congress of Immunology/FOCIS meeting in Montreal. Dr. Hafler is a former incumbent of the prestigious Harry Weaver Award of the National MS Society, and is a Jacob Javits Scholar of the NIH NINDS. He was elected as a member of the American Neurologic Society and the American Society of Clinical Investigation. He presently serves on the editorial boards of the Journal of Clinical Investigation and of the Journal of Experimental Medicine and is on the ISI most highly cited index of investigators.
In July 2010, Dr. Hafler moved his laboratory from Harvard Medical School to Yale, where it is presently very active in continuing to explore the genetic basis of autoimmune diseases like Multiple Sclerosis. Concurrently, Dr. Hafler also serves as the Gilbert H. Glaser Professor and Chairman Department of Neurology, Yale School of Medicine and is the Neurologist-in-Chief of the Yale-New Haven Hospital.