Analysis of the uveitogenic determinant in repeat structure of retinal interphotoreceptor retinoid-binding protein (IRBP)

Cytokines in posterior uveitis: an update

T helper (Th) lymphocytes differentiate into two distinct subsets--Th1 and Th2--as defined by functional abilities and cytokine profiles. The functional differences between Th subsets are explained primarily through the activities of the cytokines they secrete. Interferon-gamma (IFN-gamma) is the signature cytokine of Th1 cells, which also produce interleukin-2 (IL-2) and tumor necrosis factor-beta (TNF-beta). IL-4 is the corresponding signature cytokine of Th2 cells, which also secrete IL-5, IL-6, IL-9, and IL-13. Recently, a few transcription factors have been identified that not only control the expression of cytokines of a particular type but also repress cytokines of other types. Human Th1 and Th2 cells not only produce a different set of cytokines but also exhibit distinct functional properties and the preferential expression of some activation markers. Pathophysiologically, the two subsets have been found to be mutually antagonistic. Various Th1 and Th2 cytokines appear to play an important role in the etiopathogenesis of posterior uveitis and its animal model, experimental autoimmune uveitis (EAU). The exact contribution of these mediators to uveitis remains to be defined. Recent studies suggest that a shift from Th1- to Th2-dominated response could be of therapeutic benefit. This review evaluates various studies in which uveitopathogenic and therapeutic potentials of various Th1 and Th2 cytokines have been investigated.

Suppression of spontaneous uveoretinitis development by non-immunopathogenic peptide immunization

BALB/c nude mice which are grafted with thymus tissue from fetal F344 rats beneath the renal capsule (hereafter referred to as TG nude mice) spontaneously develop uveoretinitis as well as other organ-localized autoimmune diseases. Active immunization with an interphotoreceptor retinoid-binding protein (IRBP)-derived peptide, amino acids 518-529 (P518-529), induced rapid development and high incidence of uveoretinitis, whereas immunization with another amino acid fragment, 1182-1194 (P1182-1194), inhibited the disease process. P1182-1194- or P518-529-specific T cell lines were established from TG nude mice. Although both were of CD4+ type, P518-529-specific T cells expressed Vbeta8 TCR while Vbeta6 expression was evident in the P1182-1194-specific cells. P518-529-specific T cells produced IL-2 and IFN-gamma, but not IL-4 or IL-10, whereas P1182-1194-specific T cells produced IL-4 and IL-10, but not IL-2 or IFN-gamma Adoptive transfer of these peptide-specific T cells into naive BALB/c nude mice resulted in development of uveoretinitis only in the P518-529 case. Furthermore, mice receiving both T cell types simultaneously did not exhibit uveoretinitis. The results indicate that the amino acid fragment of IRBP, P518-529, is uveitogenic and immunogenic in TG nude mice and induces Th1-type T cells related to uveoretinitis, whereas the amino acid fragment 1182-1194 is immunogenic but not uveitogenic, inducing Th2-type T cells which are involved in inhibition of this pathological response in TG nude mice.

Protection against generalized autoimmunity of the nervous system (GANS), a novel animal model with combined features of EAE, EAN and EAU by a recombinant HIV-1 Tat37-72 peptide-based multiple T cell epitope vaccine

A new model of multi-compartment auto-immune disease has been established to analyze the effects of polyvalent recombinant peptide vaccines. A synthetic gene encoding major pathogenic determinants for Lewis rats of guinea pig myelin basic protein (MBP68-84), bovine interphotoreceptor retinoid binding protein (IRBP1169-1191), and bovine P2 protein (P2,53-78) was used to induce Generalized Autoimmunity of the Nervous System (GANS), which is characterized by development of auto-immune infiltration of the brain and spinal cord, the eyes, the pineal organ and the peripheral nerves. Thus, this model integrates the prominent features of three auto-immune diseases: experimental autoimmune encephalomyelitis (EAE), neuritis (EAN) and uveitis (EAU). In this study, GANS was used to study the effect of HIV-1 Tat37-72 targeting peptide on vaccination by recombinant polyvalent T cell auto-antigen vaccine. Depending on the route of administration, the recombinant vaccine effectively protects against the development of auto-immune nervous system inflammation.

Experimental autoimmune uveitis: molecular mimicry and oral tolerance

Intraocular inflammatory disease or uveitis, which affects the uveal tract and the retina of the eyes in human, is the major cause of visual impairment. Experimental autoimmune uveitis (EAU) is a T-cell-mediated autoimmune disease directed against retinal proteins and has been studied in several mammalian species including subhuman primates as a model for human posterior uveitis. Autoimmune responses provoked by molecular mimicry occur when the nonself and host determinants are similar enough to cross-react yet different enough to break immunological tolerance, and is one of the proposed mechanisms for induction of autoimmune diseases. Therapeutic immunomodulatory strategies have been used to induce antigen-specific peripheral immune tolerance in animal models of T-cell-mediated autoimmune diseases by oral administration of autoantigens. Oral tolerance leads to unique mechanisms of tissue and disease-specific immunosuppression, which would circumvent the immunotherapeutic problem of multiple target tissue autoreactivity. Several groups have investigated the effects of delivering autoantigens across gastric mucosal surfaces. This review briefly discusses molecular mimicry and the mechanism of induction of oral tolerance with respect to immunopathogenesis of T-cell-mediated autoimmune disease in general and EAU in particular.

Generalized autoimmunity of the nervous system (GANS) induced by a recombinant protein composed of major pathogenic determinants of MBP, IRBP, and P2 protein: suppression of inflammation by a monoclonal antibody against activated rat T line cells

We have developed a new model of generalized autoimmunity of the rat nervous system to study differential immunoregulation, barrier-function, and parenchymal inflammatory processes. We designed a multicomponent synthetic gene encoding major pathogenic determinants for Lewis rats of myelin basic protein (MBP), interphotoreceptor retinoid binding protein (IRBP), and P2 protein. Immunization with the recombinant protein induces a monophasic disease with inflammatory lesions in the eye, brain, spinal cord, and peripheral nerves. Rats recovered from GANS were tolerant against the induction of experimental autoimmune encephalomyelitis (EAE), neuritis (EAN), and uveoretinitis (EAU) by immunization with synthetic autoantigen-peptides/CFA. To demonstrate an application of GANS we have used a monoclonal antibody raised against encephalitogenic rat T lymphocytes. We show that this monoclonal antibody is suppressing not only inflammatory cell infiltration of brain and spinal cord, but as well of the eyes and the peripheral nervous system.

Acute anterior uveitis: clinical and experimental aspects

Acute anterior uveitis (AAU) or iritis is an inflammatory disorder of the anterior structures of the eye that may be associated with a number of disease entities. A significant proportion of patients will have no evidence of an underlying disorder and are labeled as idiopathic. Within this group approximately 50% will possess the human leukocyte antigen, HLA-B27, and some will have an associated spondyloarthropathy such as ankylosing spondylitis or Reiter's syndrome. Nevertheless, a number of HLA-B27-positive patients have no apparent underlying rheumatic disorder. The potential interplay of HLA-B27 and certain infective agents in the pathogenesis of AAU is discussed with particular reference to Yersinia species. Presentation of a uveitogenic peptide, similar to the arthritogenic peptide model in spondyloarthropathies, may be a mechanism involved in the development of AAU. Experimental models in animals have increased our understanding of the roles of retinal proteins and bacterial peptides, as well as T cells and cytokines, in the pathogenesis of uveitis. As in animal models of arthritis, certain retinal peptides (in conjunction with adjuvant therapy) can induce uveitis in animals. The treatment of isolated AAU usually involves topical medication and the prognosis is good. Occasional cases, especially those associated with systemic disorders, may require the addition of systemic corticosteroids or other immunosuppressive medications.