T-cell vaccination: from basics to the clinic

Prospects for a T-cell receptor vaccination against myasthenia gravis

T-cell receptor (TCR) vaccination has been proposed as a specific therapy against autoimmune diseases. It is already used in clinical trials, which are supported by pharmaceutical companies for the treatment of multiple sclerosis, rheumatoid arthritis and psoriasis. Current vaccine developments are focusing on enhancement of immunogenicity as well as selecting the best route of immunization and adjuvant to favor the therapeutic effect. In the meantime, academic laboratories are tackling the regulatory mechanisms involved in the beneficial effect of the vaccines to further understand how to control the therapeutic tool. Indeed, several examples in experimental models of autoimmune diseases indicate that any specific therapy may rely on a delicate balance between the pathogenic and regulatory mechanisms. This review presents a critical analysis of the potential of such therapy in myasthenia gravis, a prototype antibody-mediated disease. Indeed, a specific pathogenic T-cell target population and a TCR-specific regulatory mechanism mediated by anti-TCR antibodies and involved in protection from the disease have recently been identified in a patient subgroup. The presence of spontaneous anti-TCR antibodies directed against the pathogenic T-cells that may be boosted by a TCR vaccine provides a rationale for such therapy in myasthenia gravis. The development of this vaccine may well benefit from experience gained in the other autoimmune diseases in which clinical trials are ongoing.

Sercarzian immunology--In memoriam. Eli E. Sercarz, 1934-2009

During his long career as a principal investigator and educator, Eli Sercarz trained over 100 scientists. He is best known for developing hen egg white lysozyme (HEL) as a model antigen for immunologic studies. Working in his model system Eli furthered our understanding of antigen processing and immunologic tolerance. His work established important concepts of how the immune system recognizes antigenic determinants processed from whole protein antigens; specifically he developed the concepts of immunodominance and crypticity. Later in his career he focused more on autoimmunity using a variety of established animal models to develop theories on how T cells can circumvent tolerance induction and how an autoreactive immune response can evolve over time. His theory of "determinant spreading" is one of the cornerstones of our modern understanding of autoimmunity. This review covers Eli's entire scientific career outlining his many seminal discoveries.

Immunization with autologous T cells enhances in vivo anti-tumor immune responses accompanied by up-regulation of GADD45β

Immunization with inactivated autoreactive T cells may induce idiotype anti-idiotypic reactions to deplete autoreactive T cells, which are involved in autoimmune diseases. However, it is unknown whether attenuated activated healthy autologous T-cell immunization could increase anti-tumor immune responses. To this end, C57Bl/6 mice were immunized with attenuated activated autologous T cells. The splenocytes from immunized mice showed a higher proliferative ability than that from naive mice. The special phenotype analysis showed that there were more CD8+ T cells and CD62L+ T cells in immunized mice after 24 h of culture with 10% fetal calf serum complete medium in vitro (P<0.01). These results demonstrated that this immunization may activate T cells in vivo. Furthermore, the splenocytes from immunized mice revealed resistance to activation-induced cell death (AICD) in vitro. To further study the relative genes that are responsible for the higher proliferation and resistance to AICD, the expression of Fas/Fas ligand (FasL) and GADD45b was measured by real-time PCR. The results indicated that GADD45beta transcription was higher in the splenocytes from immunized mice than that in the naive mice. In addition, the Fas expression showed a parallel higher, but FasL did not change obviously. To investigate the biologic functions induced by immunization in vivo, a tumor model was established by EL-4 tumor cell inoculation in C57/Bl mice. Mice receiving autologous T-cell immunization had significantly inhibited tumor growth in vivo (P<0.01). This study implicated that immunization with attenuated activated autologous T cells enhances anti-tumor immune responses that participate in tumor growth inhibition.

CD4+ regulatory T cell responses induced by T cell vaccination in patients with multiple sclerosis

Immunization with irradiated autologous T cells (T cell vaccination) is shown to induce regulatory T cell responses that are poorly understood. In this study, CD4(+) regulatory T cell lines were generated from patients with multiple sclerosis that received immunization with irradiated autologous myelin basic protein-reactive T cells. The resulting CD4(+) regulatory T cell lines had marked inhibition on autologous myelin basic protein-reactive T cells and displayed two distinctive patterns distinguishable by the expression of transcription factor Foxp3 and cytokine profile. The majority of the T cell lines had high Foxp3 expression and secreted both IFN-gamma and IL-10 as compared with the other pattern characteristic of low Foxp3 expression and predominant production of IL-10 but not IFN-gamma. CD4(+) regulatory T cell lines of both patterns expressed CD25 and reacted with activated autologous T cells but not resting T cells, irrespective of antigen specificity of the target T cells. It was evident that they recognized preferentially a synthetic peptide corresponding to residues 61-73 of the IL-2 receptor alpha chain. T cell vaccination correlated with increased Foxp3 expression and T cell reactivity to peptide 61-73. The findings have important implications in the understanding of the role of CD4(+) regulatory T cell response induced by T cell vaccination.

Tregs in T cell vaccination: exploring the regulation of regulation

T cell vaccination (TCV) activates Tregs of 2 kinds: anti-idiotypic (anti-id) and anti-ergotypic (anti-erg). These regulators furnish a useful view of the physiology of T cell regulation of the immune response. Anti-id Tregs recognize specific effector clones by their unique TCR CDR3 peptides; anti-id networks of CD4+ and CD8+ Tregs have been described in detail. Here we shall focus on anti-erg T regulators. Anti-erg T cells, unlike anti-id T cells, do not recognize the clonal identity of effector T cells; rather, anti-erg T cells recognize the state of activation of target effector T cells, irrespective of their TCR specificity. We consider several features of anti-erg T cells: their ontogeny, subset markers, and target ergotope molecules; mechanisms by which they regulate other T cells; mechanisms by which they get regulated; and therapeutic prospects for anti-erg upregulation and downregulation.

Homeostatic control of immunity by TCR peptide-specific Tregs

Regulation of the immune response is a multifaceted process involving lymphocytes that function to maintain both self tolerance as well as homeostasis following productive immunity against microbes. There are 2 broad categories of Tregs that function in different immunological settings depending upon the context of antigen exposure and the nature of the inflammatory response. During massive inflammatory conditions such as microbial exposure in the gut or tissue transplantation, regulatory CD4+CD25+ Tregs broadly suppress priming and/or expansion of polyclonal autoreactive responses nonspecifically. In other immune settings where initially a limited repertoire of antigen-reactive T cells is activated and expanded, TCR-specific negative feedback mechanisms are able to achieve a fine homeostatic balance. Here I will describe experimental evidence for the existence of a Treg population specific for determinants that are derived from the TCR and are expressed by expanding myelin basic protein-reactive T cells mediating experimental autoimmune encephalomyelitis, an animal prototype for multiple sclerosis. These mechanisms ensure induction of effective but appropriately limited responses against foreign antigens while preventing autoreactivity from inflicting escalating damage. In contrast to CD25+ Tregs, which are most efficient at suppressing priming or activation, these specific Tregs are most efficient in controlling T cells following their activation.

The heuristics of biologic theory: the case of self-nonself discrimination

Mel Cohn has responded to our critique of the minimal model of self-nonself discrimination proposed by Langman and him. In this response to Mel Cohn, we summarize the essential differences between our points of view and highlight one criterion (of many) for preferring one theory to another in the complex field of biology: a preferred theory, rather than solving a problem, is heuristic. A good theory is one that activates a scientist to perform experiments that are novel and productive.

Inflammation and therapeutic vaccination in CNS diseases

The spectrum of inflammatory diseases of the central nervous system has been steadily expanding from classical autoimmune disorders such as multiple sclerosis to far more diverse diseases. Evidence now suggests that syndromes such as Alzheimer's disease and stroke have important inflammatory and immune components and may be amenable to treatment by anti-inflammatory and immunotherapeutic approaches. The notion of 'vaccinating' individuals against a neurodegenerative disorder such as Alzheimer's disease is a marked departure from classical thinking about mechanism and treatment, and yet therapeutic vaccines for both Alzheimer's disease and multiple sclerosis have been validated in animal models and are in the clinic. Such approaches, however, have the potential to induce unwanted inflammatory responses as well as to provide benefit.

T-cell vaccination for autoimmune diseases: immunologic lessons and clinical experience in multiple sclerosis

Autoreactive T-cells are regulated under the normal conditions and play an important role in autoimmune pathologies when they are dysregulated as a result of genetic, environmental and other unknown factors associated with various autoimmune diseases. The immune regulation of autoreactive T-cells may be regained by activating the regulatory network, such as the idiotype anti-idiotypic network. Immunization with inactivated autoreactive T-cells (T-cell vaccination) can be used as a powerful means of activating the idiotype anti-idiotypic network to deplete specific subsets of autoreactive T-cells potentially involved in autoimmune conditions. It induces regulatory immune responses that closely resemble the in vivo situation, where the immune system is challenged by clonal activation and expansion of given T-cell populations in various autoimmune diseases. Recent clinical trials in multiple sclerosis have begun to reveal the role of T-cell vaccination in the understanding of in vivo regulation of autoreactive T-cells and in the development of effective therapeutic strategies for multiple sclerosis and other autoimmune conditions. In this article, we will review the recent advances in T-cell vaccination in relationship to the regulatory mechanism induced by T-cell vaccination and the potential of T-cell vaccination as a treatment for T-cell-mediated autoimmune diseases. Current issues and thoughts related to the preparation of T-cell vaccine, the relevant sources of autoimmune T-cells and epitope spreading are also discussed.