Estrogen-mediated immunomodulation involves reduced activation of effector T cells, potentiation of treg cells, and enhanced expression of the PD-1 costimulatory pathway

Estrogen (E2)-induced immunomodulation involves dual effects on antigen-presenting cells (APC) and CD4(+)CD25(+) regulatory T cells (Treg) but not a direct effect on effector T cells. In this report, we further investigated the effects of E2 on APC and Treg function. We found that E2 treatment in vivo strongly reduced recovery of APC from the peritoneal cavity and inhibited induction of the inflammatory cytokines interleukin (IL)-12 and interferon-gamma but enhanced secretion of IL-10. Moreover, E2-conditioned bone marrow-derived dendritic cells (BM-DC) could both enhance Treg activity and directly inhibit responder T cells in the absence of Treg cells. We examined whether this E2-induced inhibitory activity of BM-DC might involve costimulation through the recently described PD-1 pathway. Both E2 and pregnancy markedly enhanced PD-1 expression in several types of APC, including macrophages, B cells, and especially dendritic cells (DC). Similarly to E2-induced enhancement of FoxP3 expression and experimental autoimmune encephalomyelitis protection, E2-induced enhancement of PD-1(+) cells was also mediated through estrogen receptor alpha (Esr1) in DC and macrophages but not in B cells. Based on antibody inhibition studies, PD-1 interaction with its ligands, PDL-1 and especially PDL-2, could mediate either positive or negative regulatory signaling in both mature and immature E2-conditioned DC, depending, respectively, on a relatively high (10:1) or low (1:1) ratio of T cells:BM-DC. These novel findings indicate that E2-induced immunomodulation is mediated in part through potentiation in BM-DC of the PD-1 costimulatory pathway.

Treatment of passive experimental autoimmune encephalomyelitis in SJL mice with a recombinant TCR ligand induces IL-13 and prevents axonal injury

The major goal of this study was to evaluate the efficacy and mechanism of a rTCR ligand (RTL) construct (I-A(s)/proteolipid protein (PLP)-139-151 peptide = RTL401) for treatment of SJL/J mice developing passive experimental autoimmune encephalomyelitis (EAE) that did not involve coimmunization with the highly inflammatory CFA. Our results demonstrated clearly that RTL401 was highly effective in treating passive EAE, with kinetics of recovery from disease very similar to treatment of actively induced EAE. The potent RTL401 treatment effect was reflected by a partial reduction of infiltrating mononuclear cells into CNS, minimal inflammatory lesions in spinal cord, and preservation of axons injured in vehicle-treated mice during the progression of EAE. Interestingly, in the absence of CFA, RTL401 treatment strongly enhanced production of the Th2 cytokine, IL-13, in spleen, blood, and spinal cord tissue, with variable effects on other Th1 and Th2 cytokines, and no significant effect on the Th3 cytokine, TGF-beta1, or on FoxP3 that is expressed by regulatory T cells. Moreover, pretreatment of PLP-139-151-specific T cells with RTL401 in vitro induced high levels of secreted IL-13, with lesser induction of other pro- and anti-inflammatory cytokines. Given the importance of IL-13 for protection against EAE, these data strongly implicate IL-13 as a dominant regulatory cytokine induced by RTL therapy. Pronounced IL-13 levels coupled with marked reduction in IL-6 levels secreted by PLP-specific T cells from blood after treatment of mice with RTL401 indicate that IL-13 and IL-6 may be useful markers for following effects of RTL therapy in future clinical trials in multiple sclerosis.

Enhanced FoxP3 expression and Treg cell function in pregnant and estrogen-treated mice

Estrogen (E2) upregulates the FoxP3 gene that marks regulatory CD4+CD25+ T cells (Treg cells). However, E2 also inhibits the ability of antigen presenting cells (APC) to activate T cells. It is possible that these opposing functions might affect the degree of overt suppression during pregnancy and autoimmunity. To evaluate E2 effects on Treg cell function, we quantified FoxP3 levels and Treg suppression in CD4+CD25+ T cells from pregnant and E2-treated mice, and overt Treg suppression in E2- vs. placebo-pretreated mice with autoimmune encephalomyelitis. The data clearly demonstrate that enhanced expression of FoxP3, which occurs in pregnant mice and in mice treated exogenously with E2 pellets, results in a concomitant increase in functional suppression within the CD4+CD25(bright) Treg fraction of splenocytes. The similarities in FoxP3 expression and Treg cell function in E2-treated and pregnant mice implicate E2 as a major contributor for increasing Treg function during pregnancy. Surprisingly, suppression was not enhanced when Treg cells from E2-treated mice were activated with APC and CD4+CD25- responder T cells from the same E2-treated mice, a result consistent with impaired APC activation of Treg cells. In contrast, Treg suppression was strikingly enhanced in combined cell cultures from E2-pretreated mice that were protected from EAE induced with neuroantigen in complete Freund's adjuvant. These results suggest that E2 treatment may have opposing effects on Treg cells vs. APC that both contribute to overt suppression, but such effects are overcome and focused towards enhanced suppression in inflammatory environments produced during pregnancy and EAE.

TCR peptide vaccination in multiple sclerosis: boosting a deficient natural regulatory network that may involve TCR-specific CD4+CD25+ Treg cells

Vaccination with self peptides contained within T cell receptor (TCR) chains, expressed by pathogenic Th1 cells can induce a second set of regulatory T cells that can reverse paralysis in rodents with experimental encephalomyelitis, and similarly, may have the potential to regulate myelin-reactive Th1 cells in patients with multiple sclerosis (MS). In this review, we discuss our recent discovery that TCR-reactive T cells generally possess classical inhibitory activity associated with Treg cells. CD4+CD25+ TCR-reactive T cells can inhibit CD4+CD25- indicator cells stimulated with anti-CD3/anti-CD28 antibody in a dose-dependent and cell-contact-dependent manner. Additionally, CD4+CD25+ T cells from blood of healthy control donors have significant responses to a pool of discriminatory TCR peptides, including BV10S1P, BV19S20, BV13S7, BV12S2A2T, BV11S1A1T, BV21S3A1T, AV15S1, and BV12S1A1N1. Patients with MS have varying degrees of deficient responses to TCR peptides, and by association, a defect in Treg cell function as well. TCR peptide vaccination using a new tripeptide mixture emulsified in IFA produced strong T cell responses in 100% of MS recipients, a dramatic improvement over previous vaccines given i.d. in saline that induced TCR-reactive T cell responses in about 50% of recipients. Responders to vaccination had a tendency towards reduced MRI lesions, and an early indication of enhanced Treg activity mediated by TCR-reactive T cells that could provide suppression of target as well as bystander T cells. These data provide a strong foundation for future TCR vaccination studies that will critically test the ability of the tripeptide mixture to induce significantly enhanced Treg activity and possible clinical and MRI benefits in vivo.

Ethinyl estradiol treats collagen-induced arthritis in DBA/1LacJ mice by inhibiting the production of TNF-alpha and IL-1beta

We previously demonstrated the therapeutic effects of ethinyl estradiol (EE), an orally active estrogen and a component of birth control pills, in encephalitogenic autoimmune encephalomyelitis (EAE). In this study, we report the effectiveness of EE in treating collagen-induced arthritis (CIA) induced with bovine type II collagen (bCII) in DBA/1LacJ mice, a CIA susceptible strain. Both low and high doses of EE notably suppressed clinical and histological signs of CIA in a dose-dependent manner compared to vehicle-treated controls. Oral treatment with EE decreased proliferation and secretion of pro-inflammatory factors, TNF-alpha IFN-gamma, MCP-1 and IL-6 by bCII peptide-specific T cells, production of bCII-specific IgG2a antibodies, and mRNA for cytokines, chemokines and chemokine receptors in joint tissue. This is the first report demonstrating effective treatment of joint inflammation and clinical signs of CIA with orally administered ethinyl estradiol, thus supporting its possible clinical use for treating rheumatoid arthritis in humans.

Activation pathways implicate anti-HLA-DP and anti-LFA-1 antibodies as lead candidates for intervention in chronic berylliosis

CD4(+) T cells play a key role in granulomatous inflammation in the lung of patients with chronic beryllium disease. The goal of this study was to characterize activation pathways of beryllium-responsive bronchoalveolar lavage (BAL) CD4(+) T cells from chronic beryllium disease patients to identify possible therapeutic interventional strategies. Our results demonstrate that in the presence of APCs, beryllium induced strong proliferation responses of BAL CD4(+) T cells, production of superoptimal concentrations of secreted proinflammatory cytokines, IFN-gamma, TNF-alpha,and IL-2, and up-regulation of numerous T cell surface markers that would promote T-T Ag presentation. Ab blocking experiments revealed that anti-HLA-DP or anti-LFA-1 Ab strongly reduced proliferation responses and cytokine secretion by BAL CD4(+) T cells. In contrast, anti-HLA-DR or anti-OX40 ligand Ab mainly affected beryllium-induced proliferation responses with little impact on cytokines other than IL-2, thus implying that nonproliferating BAL CD4(+) T cells may still contribute to inflammation. Blockade with CTLA4-Ig had a minimal effect on proliferation and cytokine responses, confirming that activation was independent of B7/CD28 costimulation. These results indicate a prominent role for HLA-DP and LFA-1 in BAL CD4(+) T cell activation and further suggest that specific Abs to these molecules could serve as a possible therapy for chronic beryllium disease.

Identification of HLA-DRB1*1501–Restricted T-cell Epitopes from Prostate-Specific Antigen

The development of immunotherapy for prostate cancer based on the induction of autoimmunity to prostate tissue is very attractive because prostate is not a vital organ beyond the reproductive years. CD4 T cells play an important role in the development of antitumor immune responses, yet the identification of naturally processed MHC Class II-restricted epitopes derived from prostate differentiation antigens has not been described. To facilitate the search for prostate-specific antigen (PSA)-derived MHC class II-restricted peptides, we immunized mice transgenic for HLA-DRB1*1501 with human PSA and showed a robust dose-dependent immune response to the antigen. Screening a library of overlapping 20-mer peptides that span the entire PSA sequence identified two 20-mer peptides, PSA(171-190) and PSA(221-240), which were responsible for this reactivity. Immunization of DR2b transgenic mice with these peptides induced specific responses to the peptide and whole PSA. Identified peptides were used to stimulate CD4 T cells from HLA-DRB1*1501+ patients with a rare condition, granulomatous prostatitis, and who seem to have a preexisting immune response directed against the prostate gland. We previously showed a linkage of granulomatous prostatitis to HLA-DRB1*1501, suggesting that this disease may have an autoimmune etiology. Peptide-specific CD4 T-cell lines were generated from the peripheral blood of these patients as well as one patient with prostate cancer. These lines also recognized whole, processed PSA in the context of HLA-DRB1*1501. This study will be instrumental in understanding the interaction between circulating self-reactive T cells, organ-specific autoimmunity, and antitumor immune response. The use of these peptides for the immunotherapy of prostate cancer is under investigation.

Middle-Age Male Mice Have Increased Severity of Experimental Autoimmune Encephalomyelitis and Are Unresponsive to Testosterone Therapy

Treatment with sex hormones is known to protect against experimental autoimmune encephalomyelitis (EAE), an animal model of multiple sclerosis. However, little is known about how age affects the course of EAE or response to hormone treatment. This study demonstrates striking differences between middle-age vs young C57BL/6 male mice in the clinical course of EAE and response to both testosterone (T4) and estrogen (E2) hormone therapy. Unlike young males that developed an acute phase of EAE followed by a partial remission, middle-age males suffered severe chronic and unremitting EAE that was likely influenced by alterations in the distribution and function of splenic immunocytes and a significant reduction in suppressive activity of CD4+CD25+ regulatory T cells in the spleen and spinal cord. Middle-age males had reduced numbers of splenic CD4+ T cells that were generally hypoproliferative, but enhanced numbers of splenic macrophages and MHC class II-expressing cells, and increased secretion of the proinflammatory factors IFN-gamma and MCP-1. Surprisingly, middle-age males were unresponsive to the EAE-protective effects of T4 and had only a transient benefit from E2 treatment; young males were almost completely protected by both hormone treatments. T4 treatment of young males inhibited proliferation of myelin oligodendrocyte glycoprotein 35-55-specific T cells and secretion of TNF-alpha and IFN-gamma. The effects of T4 in vivo and in vitro were reversed by the androgen receptor antagonist, flutamide, indicating that the regulatory effects of T4 were mediated through the androgen receptor. These data are the first to define age-dependent differences in EAE expression and response to hormone therapy.

HLA-DRB1*1501 risk association in multiple sclerosis may not be related to presentation of myelin epitopes

Susceptibility to multiple sclerosis (MS) is associated genetically with human leucocyte antigen (HLA) class II alleles, including DRB1*1501, DRB5*0101, and DQB1*0602, and it is possible that these alleles contribute to MS through an enhanced ability to present encephalitogenic myelin peptides to pathogenic T cells. HLA-DRB1*1502, which contains glycine instead of valine at position 86 of the P1 peptide-binding pocket, is apparently not genetically associated with MS. To identify possible differences between these alleles in their antigen-presenting function, we determined if T-cell responses to known DRB1*1501-restricted myelin peptides might be diminished or absent in transgenic (Tg) DRB1*1502-expressing mice. We found that Tg DRB1*1502 mice had moderate to strong T-cell responses to several myelin peptides with favorable DRB1*1501 binding motifs, notably myelin oligodendrocyte glycoprotein (MOG)-35-55 (which was also encephalitogenic), proteolipid protein (PLP)-95-116, and MOG-194-208, as well as other PLP and MOG peptides. These peptides, with the exception of MOG-194-208, were also immunogenic in healthy human donors expressing either DRB1*1502 or DRB1*1501. In contrast, the DRB1*1502 mice had weak or absent responses to peptides with unfavorable DRB1*1501 binding motifs. Overall, none of the DRB1*1501-restricted myelin peptides tested selectively lacked immunogenicity in association with DRB1*1502. These results indicate that the difference in risk association with MS of DRB1*1501 versus DRB1*1502 is not due to a lack of antigen presentation by DRB1*1502, at least for this set of myelin peptides, and suggest that other mechanisms involving DRB1*1501 may account for increased susceptibility to MS.

T lymphocytes do not directly mediate the protective effect of estrogen on experimental autoimmune encephalomyelitis

Gender influences mediated by 17 beta-estradiol (E2) have been associated with susceptibility to and severity of autoimmune diseases such as diabetes, arthritis, and multiple sclerosis. In this regard, we have shown that estrogen receptor-alpha (Esr1) is crucial for the protective effect of 17 beta-estradiol (E2) in murine experimental autoimmune encephalitis (EAE), an animal model of multiple sclerosis. The expression of estrogen receptors among various immune cells (eg, T and B lymphocytes, antigen-presenting cells) suggests that the therapeutic effect of E2 is likely mediated directly through specific receptor binding. However, the target immune cell populations responsive to E2 treatment have not been identified. In the current study, we induced EAE in T-cell-deficient, severe combined immunodeficient mice or in immunocompetent mice with encephalitogenic T cells from wild-type Esr1+/+ or Esr1 knockout (Esr1-/-) donors and compared the protective E2 responses. The results showed that E2-responsive, Esr1+/+ disease-inducing encephalitogenic T cells were neither necessary nor sufficient for E2-mediated protection from EAE. Instead, the therapeutic response appeared to be mediated through direct effects on nonlymphocytic, E2-responsive cells and down-regulation of the inflammatory response in the central nervous system. These results provide the first demonstration that the protective effect of E2 on EAE is not mediated directly through E2-responsive T cells and raise the alternative possibility that nonlymphocytic cells such as macrophages, dendritic cells, or other nonlymphocytic cells are primarily responsive to E2 treatment in EAE.

Decreased FOXP3 levels in multiple sclerosis patients

Autoimmune diseases such as multiple sclerosis (MS) may result from the failure of tolerance mechanisms to prevent expansion of pathogenic T cells. Our study is the first to establish that MS patients have abnormalities in FOXP3 message and protein expression levels in peripheral CD4+ CD25+ T cells (Tregs) that are quantitatively related to a reduction in functional suppression induced during suboptimal T-cell receptor (TCR) ligation. Of importance, this observation links a defect in functional peripheral immunoregulation to an established genetic marker that has been unequivocally shown to be involved in maintaining immune tolerance and preventing autoimmune diseases. Diminished FOXP3 levels thus indicate impaired immunoregulation by Tregs that may contribute to MS. Future studies will evaluate the effects of therapies known to influence Treg cell function and FOXP3 expression, including TCR peptide vaccination and supplemental estrogen.

Rationally designed mutations convert complexes of human recombinant T cell receptor ligands into monomers that retain biological activity

Single-chain human recombinant T cell receptor ligands derived from the peptide binding/TCR recognition domain of human HLA-DR2b (DRA*0101/DRB1*1501) produced in Escherichia coli with and without amino-terminal extensions containing antigenic peptides have been described previously. While molecules with the native sequence retained biological activity, they formed higher order aggregates in solution. In this study, we used site-directed mutagenesis to modify the β-sheet platform of the DR2-derived RTLs, obtaining two variants that were monomeric in solution by replacing hydrophobic residues with polar (serine) or charged (aspartic acid) residues. Size exclusion chromatography and dynamic light scattering demonstrated that the modified RTLs were monomeric in solution, and structural characterization using circular dichroism demonstrated the highly ordered secondary structure of the RTLs. Peptide binding to the `empty' RTLs was quantified using biotinylated peptides, and functional studies showed that the modified RTLs containing covalently tethered peptides were able to inhibit antigen-specific T cell proliferation in vitro, as well as suppress experimental autoimmune encephalomyelitis in vivo. These studies demonstrated that RTLs encoding the Ag-binding/TCR recognition domain of MHC class II molecules are innately very robust structures, capable of retaining potent biological activity separate from the Ig-fold domains of the progenitor class II structure, with prevention of aggregation accomplished by modification of an exposed surface that was buried in the progenitor structure.

T-cell hybridoma specific for myelin oligodendrocyte glycoprotein-35-55 peptide produced from HLA-DRB1*1501-transgenic mice

The goal of this study was to establish an unlimited and standardized source of humanized myelin peptide-specific T cells for in vitro testing of biological function. Thus, we perpetuated myelin oligodendrocyte glycoprotein (MOG)-35-55 peptide-specific T cells obtained from immunized HLA-DRB1*1501-transgenic (Tg) mice by somatic fusions with BW5147 thymoma cells or BW5147 T-cell receptor (TCR) alpha(-)beta(-) variant (BW5147 variant) cells. The resulting T-cell hybridomas responded strongly to both mouse MOG-35-55 (42S) and human MOG-35-55 peptide (42P), regardless of which peptide was used for initial immunization, and were DRB1*1501 restricted. The MOG-35-55-reactive T-cell hybridomas were CD3(+)CD4(+)CD8(-) and expressed intracellular Th1 cytokines upon concanavalin A stimulation. Clones from either human MOG-35-55- or mouse MOG-35-55-selected hybridomas uniquely expressed the TCR BV8 gene in combination with AV17 and AV11 genes. V gene analyses confirmed the expression of TCR AV1, AV11, AV16, BV1, and BV5 gene segments in the widely used fusion partner BW5147 and demonstrated deletion of TCR AV1, AV11, and BV1 in the BW5147 variant. T-cell hybridomas were positively stained with anti-TCR beta-chain antibody on the cell surface, whereas neither BW5147 nor its variant had positive TCR surface expression. For functional application, we found that a monomeric form of the human HLA-DR2-derived recombinant T-cell receptor ligand (RTL) covalently linked to human MOG-35-55 peptide specifically inhibited proliferation of a hybridoma clone selected with human MOG-35-55 but not a different hybridoma clone selected with myelin basic protein. The RTL-induced inhibition in vitro of the human MOG-35-55 peptide-specific hybridoma reflected the ability of the RTL to inhibit experimental autoimmune encephalomyelitis induced by human MOG-35-55 peptide in HLA-DR2 transgenic mice. Thus, the MOG-35-55 peptide-specific T-cell hybridoma from DR2-Tg mice represents a novel humanized T-cell reagent useful for standardized biological screening of both DR2-restricted stimulation and RTL-dependent inhibition of response to human MOG-35-55 peptide.

Veterans Administration support for medical research: opinions of the endangered species of physician‐scientists 1

Over the past three decades the Veterans Affairs (VA) Research program has evolved into a powerful, peer-reviewed funding mechanism for basic and translational research that has resulted in numerous important contributions to medical science and improvements in patient care. Continuity in VA Merit Review funding has fostered and nurtured the scientific careers of a large number of physician-scientists who have remained devoted to the mission of performing creative and innovative research that affects the patient care mission of the VA. VA medical research policies have undergone a major overhaul in the past year. Although many of these changes (de-emphasizing bench research and revamping the peer review process) have recently been reversed, the future direction of VA research remains in flux. The goal of this manuscript is to demonstrate the importance of the Merit Review medical research funding mechanism not just to the VA, but to the entire nation's health care system. To achieve this goal, the opinions of 65 established VA medical investigators were obtained regarding the past success and future direction of VA research. The conclusions reached include the following. 1) Merit Review research funding has been essential to the training, recruitment, and retention of productive VA physician-scientists. 2) The VA research program has contributed both basic and clinical innovations that have led to improvements in medical care. Contributions of VA researchers to excellence in many aspects of patient care at VA hospitals have been extraordinary. 3) Development of initiatives that entice outstanding Ph.D.'s to develop their careers in the VA has been crucial to the success of the program. 4) The VA research program has fostered a mutually beneficial relationship with affiliated medical schools. 5) Better methods to quantify VA research contributions and outcomes are essential for future program development.

Estrogen treatment induces a novel population of regulatory cells, which suppresses experimental autoimmune encephalomyelitis

Multiple sclerosis (MS) is a debilitating neurological disease characterized by a progressive loss of motor and sensory function, eventually leading to paralysis and death. The primary cause of neurological impairment is demyelination of the central nervous system (CNS) caused by an inflammatory autoimmune response. Previous studies have shown that the severity of MS is reduced during pregnancy, suggesting that the increased level of sex hormones may reduce the autoimmune response. Recently, we have shown that estrogen treatment confers protection from experimental autoimmune encephalomyelitis (EAE), which is an animal model for MS. However, the cellular basis of estrogen's action remains unknown. In the current study, we demonstrate that estrogen treatment led to the induction of a novel subpopulation of regulatory cells in spleen and CNS, which also occurs naturally in pregnant mice. These previously uncharacterized cells display a low level expression of CD45 (CD45(dim)) and no detectable expression of many cell surface markers related to TCR signaling, including CD3 and TCR. However, these cells retained expression of VLA-4, an extracellular protein involved in cellular migration. Several lines of evidence suggest that these novel cells, defined as CD45(dim)VLA-4(+) cells, may play a role in the protective effects of estrogen in EAE. Injection of purified CD45(dim)VLA-4(+) cells conferred protection from spontaneous EAE (Sp-EAE). In contrast, injection of CD45(high)VLA-4(+) cells exacerbated the disease course. CD45(dim)VLA-4(+) cells also suppressed antigen-specific proliferation of primed lymphocytes in coculture. A better understanding of how CD45(dim)VLA-4(+) cells suppress the harmful immune response of EAE may help in explaining the induction of immune tolerance during pregnancy and lead to novel therapeutic approaches to combat MS and other autoimmune diseases.

Cutting Edge: Estrogen Drives Expansion of the CD4+CD25+ Regulatory T Cell Compartment

CD4(+)CD25(+) regulatory T cells are crucial to the maintenance of tolerance in normal individuals. However, the factors regulating this cell population and its function are largely unknown. Estrogen has been shown to protect against the development of autoimmune disease, yet the mechanism is not known. We demonstrate that estrogen (17-beta-estradiol, E2) is capable of augmenting FoxP3 expression in vitro and in vivo. Treatment of naive mice with E2 increased both CD25(+) cell number and FoxP3 expression level. Further, the ability of E2 to protect against autoimmune disease (experimental autoimmune encephalomyelitis) correlated with its ability to up-regulate FoxP3, as both were reduced in estrogen receptor alpha-deficient animals. Finally, E2 treatment and pregnancy induced FoxP3 protein expression to a similar degree, suggesting that high estrogen levels during pregnancy may help to maintain fetal tolerance. In summary, our data suggest E2 promotes tolerance by expanding the regulatory T cell compartment.

Estrogen receptor-1 (Esr1) and -2 (Esr2) regulate the severity of clinical experimental allergic encephalomyelitis in male mice

Estrogens and estrogen-receptor signaling function in establishing and regulating the female immune system and it is becoming increasingly evident that they may play a similar role in males. We report that B10.PL/SnJ male mice with a disrupted estrogen receptor-1 (alpha) gene (Esr1(-/-)) develop less severe clinical experimental allergic encephalomyelitis (EAE) compared to either Esr1(+/-) or wild-type (Esr1(+/+)) controls when immunized with myelin basic protein peptide Ac1-11 (MBP(Ac1-11)). In contrast, the disease course in B10.PL/SnJ male mice with a disrupted estrogen receptor-2 (beta) gene (Esr2(-/-)) does not differ from that of wild-type (Esr2(+/+)) mice. However, Esr2(+/-) mice do develop more severe clinical disease with an earlier onset indicating that heterosis at Esr2 plays a significant role in regulating EAE in males. No significant differences in central nervous system histopathology or MBP(Ac1-11)-specific T-cell responses as assessed by proliferation and interleukin-2 production were observed as a function of either Esr1 or Esr2 genotype. An analysis of cytokine/chemokine secretion by MBP(Ac1-11)-specific T cells revealed unique Esr1 and Esr2 genotype-dependent regulation. Interferon-gamma secretion was found to be negatively regulated by Esr1 whereas interleukin-6 and tumor necrosis factor-alpha secretion exhibited classical Esr2 gene dose responses. Interestingly, MCP-1 displayed distinctively unique patterns of genotype-dependent regulation by Esr1 and Esr2. The contribution of the hematopoietic and nonhematopoietic cellular compartments associated with the heterotic effect at Esr2 in regulating the severity of clinical EAE was identified using reciprocal hematopoietic radiation bone marrow chimeras generated between male wild-type and Esr2(+/-) mice. Wild-type --> Esr2(+/-) mice exhibited EAE equivalent in severity to that seen in Esr2(+/-) --> Esr2(+/-) control constructs; both of which were more severe than the clinical signs observed in Esr2(+/-) --> wild-type and wild-type --> wild-type mice. These results indicate that the heterotic effect at Esr2 is a function of the nonhematopoietic compartment.

Myelin oligodendrocyte glycoprotein-35–55 peptide induces severe chronic experimental autoimmune encephalomyelitis in HLA-DR2-transgenic mice

The use of HLA class II-transgenic (Tg) mice has facilitated identification of antigenic T cell epitopes that may contribute to inflammation in T cell-mediated diseases such as rheumatoid arthritis and multiple sclerosis (MS). In this study, we compared the encephalitogenic activity of three DR2-restricted myelin determinants [mouse (m) myelin oligodendrocyte glycoprotein (MOG)-35-55, human (h)MOG-35-55 and myelin basic protein (MBP)-87-99] in Tg mice expressing the MS-associated DR2 allele, DRB1*1501. We found that mMOG-35-55 peptide was strongly immunogenic and induced moderately severe chronic experimental autoimmune encephalomyelitis (EAE) with white matter lesions after a single injection in Freund's complete adjuvant followed by pertussis toxin. hMOG-35-55 peptide,which differs from mMOG-35-55 peptide by a proline for serine substitution at position 42, was also immunogenic, but not encephalitogenic, and was only partially cross-reactive with mMOG-35-55. In contrast, MBP-87-99, which can induce EAE in double-Tg mice expressing both HLA-DR2 and a human MBP-specific TCR, was completely non-encephalitogenic in HLA-DR2-Tg mice lacking the human TCR transgene. These findings demonstrate potent encephalitogenic activity of the mMOG-35-55 peptide in association with HLA-DR2, thus providing a strong rationale for further study of hMOG-35-55 peptide as a potential pathogenic determinant in humans.

CD4 T-cell epitopes of human alpha B-crystallin

Of potential importance to multiple sclerosis (MS), oligodendroglial alpha B-crystallin is expressed and associated with the myelin sheath at the earliest stage of MS lesion development. We selected T-cell lines specific for human alpha B-crystallin from peripheral blood mononuclear cells (PBMC) of HLA-DR2 homozygous MS patients and found that the alpha B-crystallin-specific T-cells were CD4+ and restricted by DRB1*1501, and expressed Th1 cytokines. The CD4 T-cell epitopes of human alpha B-crystallin were determined by proliferation of alpha B-crystallin-specific T-cell lines to 17 20-mer synthetic overlapping peptides spanning the entire molecule of human alpha B-crystallin. It was found that the HLA-DR2 donor-derived alpha B-crystallin-specific T-cell lines proliferated to alpha B-crystallin peptides 21-40, 41-60, and to a lesser extent, 131-150. These T-cell proliferation responses were associated with intracellular expression of interleukin-2 (IL-2) and secretion of interferon-gamma (IFN-gamma), and tumor necrosis factor-alpha (TNF-alpha). The amino acid sequences of these peptides were compatible with predicted HLA-DR2-restricted binding motifs. PBMC of an early active MS patient proliferated to the epitope-containing peptides significantly better than did those of later stage MS patients or healthy controls. Taken together, these findings suggest that autoreactive alpha B-crystallin-specific Th1 cells may have the potential to contribute to MS pathogenesis.

Specificity of regulatory CD4+CD25+ T cells for self-T cell receptor determinants

Although the phenotypic and regulatory properties of the CD4(+)CD25(+) T cell lineage (Treg cells) have been well described, the specificities remain largely unknown. We demonstrate here that the CD4(+)CD25(+) Treg population includes the recognition of a broad spectrum of human TCR CDR2 determinants found in the germline V gene repertoire as well as that of a clonotypic nongermline-encoded CDR3beta sequence present in a recombinant soluble T cell receptor (TCR) protein. Regulatory activity was demonstrated in T cell lines responsive to TCR but not in T cell lines responsive to control antigens. Inhibitory activity of TCR-reactive T cells required cell-cell contact and involved CTLA-4, GITR, IL-10, and IL-17. Thus, the T-T regulatory network includes Treg cells with specificity directed toward self-TCR determinants.

17Beta-estradiol treatment profoundly down-regulates gene expression in spinal cord tissue in mice protected from experimental autoimmune encephalomyelitis

It is now well documented that experimental autoimmune encephalomyelitis (EAE) can be effectively prevented by estrogen therapy. Previously, we identified a limited set of genes that were altered in spleens of mice protected from EAE by 17beta-estradiol (E2) treatment. As a continuation of these studies, we present here transcriptional changes in genes expressed in spinal cord tissue. The Affymetrix microarray system was used to screen more than 12,000 genes from E2-treated double transgenic (BV8S2 and AV4) female mice protected from EAE vs. control mice with severe EAE. We found that estrogen therapy had a profound inhibitory effect on the expressions of many immune-related genes in spinal cords. Estrogen significantly affected the transcription of 315 genes, 302 of which were down-regulated and only 13 that were up-regulated by > or = 2.4 fold. A number of genes encoding the histocompatibility complex, cytokines/receptors, chemokines, adhesion molecules, and signal transduction proteins were strongly down-regulated (> 20 fold) in estrogen-treated mice to levels similar to those of the spinal cord tissue from unmanipulated mice. The identification of genes with altered expression patterns in the spinal cords of estrogen-treated mice provides unique insight into the process that ultimately results in protection against EAE.

Monomeric Recombinant TCR Ligand Reduces Relapse Rate and Severity of Experimental Autoimmune Encephalomyelitis in SJL/J Mice through Cytokine Switch

Our previous studies demonstrated that oligomeric recombinant TCR ligands (RTL) can treat clinical signs of experimental autoimmune encephalomyelitis (EAE) and induce long-term T cell tolerance against encephalitogenic peptides. In the current study, we produced a monomeric I-A(s)/PLP 139-151 peptide construct (RTL401) suitable for use in SJL/J mice that develop relapsing disease after injection of PLP 139-151 peptide in CFA. RTL401 given i.v. or s.c. but not empty RTL400 or free PLP 139-151 peptide prevented relapses and significantly reduced clinical severity of EAE induced by PLP 139-151 peptide in SJL/J or (C57BL/6 x SJL)F(1) mice, but did not inhibit EAE induced by PLP 178-191 or MBP 84-104 peptides in SJL/J mice, or MOG 35-55 peptide in (C57BL/6 x SJL/J)F(1) mice. RTL treatment of EAE caused stable or enhanced T cell proliferation and secretion of IL-10 in the periphery, but reduced secretion of inflammatory cytokines and chemokines. In CNS, there was a modest reduction of inflammatory cells, reduced expression of very late activation Ag-4, lymphocyte function-associated Ag-1, and inflammatory cytokines, chemokines, and chemokine receptors, but enhanced expression of Th2-related factors, IL-10, TGF-beta3, and CCR3. These results suggest that monomeric RTL therapy induces a cytokine switch that curbs the encephalitogenic potential of PLP 139-151-specific T cells without fully preventing their entry into CNS, wherein they reduce the severity of inflammation. This mechanism differs from that observed using oligomeric RTL therapy in other EAE models. These results strongly support the clinical application of this novel class of peptide/MHC class II constructs in patients with multiple sclerosis who have focused T cell responses to known encephalitogenic myelin peptides.

Opposing roles for TGF-β1 and TGF-β3 isoforms in experimental autoimmune encephalomyelitis

Hormones can exert significant protective effects on autoimmune diseases by activating immunoregulatory mechanisms. One of the possible mechanisms of hormonal protection might be through the anti-inflammatory effects of the TGF-beta molecule. The present study investigated the changes in expression of two TGF-beta isoforms, TGF-beta1 and TGF-beta3, in C57BL/6 and TCR transgenic (T/R+) B10.PL mice that manifested or were protected against clinical signs of experimental autoimmune encephalomyelitis (EAE) with 17beta-estradiol (E2) treatment. We here demonstrate an inverse relationship between expression of TGF-beta1 that is enhanced in mice with EAE, and TGF-beta3 that is enhanced in E2-protected mice. The differential expression of TGF-beta isoforms was observed in spinal cord tissue but not spleen. Additionally TGF-beta1 expression was evident both in whole spinal cord tissue and mononuclear cells isolated from inflamed tissue, in contrast to TGF-beta3 that was only detected in spinal cord tissue but not in mononuclear cells. Further studies revealed that CD3 and especially MAC-1 positive cells were the main source of TGF-beta1 in the mononuclear CNS population. Of crucial importance, the TGF-beta3 isoform displayed anti-proliferative properties towards encephalitogenic cells in vitro. We propose that the TGF-beta1 and TGF-beta3 isoforms play opposing roles in the expression of EAE.

Functional assay for human CD4+CD25+ Treg cells reveals an age-dependent loss of suppressive activity

CD4+CD25+ regulatory T cells (Treg cells) prevent T cell-mediated autoimmune diseases in rodents. To develop a functional Treg assay for human blood cells, we used FACS- or bead-sorted CD4+CD25+ T cells from healthy donors to inhibit anti-CD3/CD28 activation of CD4+CD25- indicator T cells. The data clearly demonstrated classical Treg suppression of CD4+CD25- indicator cells by both CD4+CD25(+high) and CD4+CD25(+low) T cells obtained by FACS or magnetic bead sorting. Suppressive activity was found in either CD45RO- (naive) or CD45RO+ (memory) subpopulations, was independent of the TCR signal strength, required cell-cell contact, and was reversible by interleukin-2 (IL-2). Of general interest is that a wider sampling of 27 healthy donors revealed an age- but not gender-dependent loss of suppressive activity in the CD4+CD25+ population. The presence or absence of suppressive activity in CD4+CD25+ T cells from a given donor could be demonstrated consistently over time, and lack of suppression was not due to method of sorting, strength of signal, or sensitivity of indicator cells. Phenotypic markers did not differ on CD4+CD25+ T cells tested ex vivo from suppressive vs. nonsuppressive donors, although, upon activation in vitro, suppressive CD4+CD25+ T cells had significantly higher expression of both CTLA-4 and GITR than CD4+CD25- T cells from the same donors. Moreover, antibody neutralization of CTLA-4, GITR, IL-10, or IL-17 completely reversed Treg-induced suppression. Our results are highly consistent with those reported for murine Treg cells and are the first to demonstrate that suppressive activity of human CD4+CD25+ T cells declines with age.

The protective effect of 17beta-estradiol on experimental autoimmune encephalomyelitis is mediated through estrogen receptor-alpha

Low-dose estrogen (E2) treatment significantly inhibits the clinical signs and histopathological lesions of experimental autoimmune encephalomyelitis (EAE), and is being used in clinical trials to treat multiple sclerosis. To assess the role of intracytoplasmic estrogen receptors in mediating suppression of EAE, we studied mice with disrupted estrogen receptor-alpha (Esr1) and -beta (Esr2) genes. We demonstrate that the protective effect of E2 is abrogated in B6.129-Esr1(tm1Unc) mice (Esr1-/-) but not in B6.129-Esr2(tm1Unc) mice (Esr2-/-). The loss of E2-mediated protection from EAE in Esr1-/- mice immunized with the encephalitogenic MOG-35-55 peptide was manifested phenotypically by the development of severe acute clinical signs and histopathological lesions even in the presence of moderately high serum E2 levels. This is in contrast to C57BL/6 wild-type (WT) mice and Esr2-/- mice in which E2 treatment resulted in comparable serum levels and markedly suppressed clinical signs of EAE and abolished inflammatory lesions in the CNS. This pattern showing a lack of E2-dependent inhibition of EAE in Esr1-/- mice was mirrored by an enhanced rather than a reduced secretion of TNF-alpha, IFN-gamma, and interleukin (IL)-6 in MOG-specific splenocytes and a lack of inhibition of message for inflammatory cytokines, chemokines and chemokine receptors in CNS tissue. These results indicate that the immunomodulatory effects of E2 in EAE are dependent on Esr1 and not Esr2 signaling.

CNS gene expression pattern associated with spontaneous experimental autoimmune encephalomyelitis

Transgenic mice with T-cell receptor (TCR) specific for myelin basic protein (MBP)-Ac1-11 peptide and homozygous for the RAG-1 mutation (T/R- mice) spontaneously develop acute progressive experimental autoimmune encephalomyelitis (Sp-EAE) mediated by CD4+ T cells. Microarray analysis of spinal cord tissue obtained from symptomatic versus non-symptomatic T/R- mice revealed strongly upregulated transcripts for genes involved in antigen presentation and processing, signal transduction, transcription regulation, metabolism, development, cell cycle, and many other processes involved in the induction of clinical and pathological signs of Sp-EAE. Several highly expressed genes were related directly to inflammation, including cytokines/receptors, chemokines/receptors, acute phase, complement molecules, and others. Many CNS-specific genes were also upregulated in sick mice. Abundance of message for the Tg TCR BV8S2 gene as well as several monocyte/macrophage-associated genes would suggest that both components play a crucial role in the pathogenesis of Sp-EAE. The profile of transcriptional changes found during the development of Sp-EAE provides the first description of the encephalitogenic process in the absence of purposeful immunization with myelin peptides and immune-enhancing adjuvants. This unique approach is the first to implicate molecules and pathways that contribute naturally to onset of paralysis and demyelination, and thus may provide unique insights and novel treatment strategies for human diseases such as multiple sclerosis.

Recombinant TCR ligand induces early TCR signaling and a unique pattern of downstream activation

Recombinant TCR ligands (RTLs) consisting of covalently linked alpha(1) and beta(1) domains of MHC class II molecules tethered to specific antigenic peptides represent minimal TCR ligands. In a previous study we reported that the rat RTL201 construct, containing RT1.B MHC class II domains covalently coupled to the encephalitogenic guinea pig myelin basic protein (Gp-MBP(72-89)) peptide, could prevent and treat actively and passively induced experimental autoimmune encephalomyelitis in vivo by selectively inhibiting Gp-MBP(72-89) peptide-specific CD4(+) T cells. To evaluate the inhibitory signaling pathway, we tested the effects of immobilized RTL201 on T cell activation of the Gp-MBP(72-89)-specific A1 T cell hybridoma. Activation was exquisitely Ag-specific and could not be induced by RTL200 containing the rat MBP(72-89) peptide that differed by a threonine for serine substitution at position 80. Partial activation by RTL201 included a CD3zeta p23/p21 ratio shift, ZAP-70 phosphorylation, calcium mobilization, NFAT activation, and transient IL-2 production. In comparison, anti-CD3epsilon treatment produced stronger activation of these cellular events with additional activation of NF-kappaB and extracellular signal-regulated kinases as well as long term increased IL-2 production. These results demonstrate that RTLs can bind directly to the TCR and modify T cell behavior through a partial activation mechanism, triggering specific downstream signaling events that deplete intracellular calcium stores without fully activating T cells. The resulting Ag-specific activation of the transcription factor NFAT uncoupled from the activation of NF-kappaB or extracellular signal-regulated kinases constitutes a unique downstream activation pattern that accounts for the inhibitory effects of RTL on encephalitogenic CD4(+) T cells.

Recombinant TCR ligand induces tolerance to myelin oligodendrocyte glycoprotein 35-55 peptide and reverses clinical and histological signs of chronic experimental autoimmune encephalomyelitis in HLA-DR2 transgenic mice

In a previous study, we demonstrated that myelin oligodendrocyte glycoprotein (MOG)-35-55 peptide could induce severe chronic experimental autoimmune encephalomyelitis (EAE) in HLA-DR2(+) transgenic mice lacking all mouse MHC class II genes. We used this model to evaluate clinical efficacy and mechanism of action of a novel recombinant TCR ligand (RTL) comprised of the alpha(1) and beta(1) domains of DR2 (DRB1*1501) covalently linked to the encephalitogenic MOG-35-55 peptide (VG312). We found that the MOG/DR2 VG312 RTL could induce long-term tolerance to MOG-35-55 peptide and reverse clinical and histological signs of EAE in a dose- and peptide-dependent manner. Some mice treated with lower doses of VG312 relapsed after cessation of daily treatment, but the mice could be successfully re-treated with a higher dose of VG312. Treatment with VG312 strongly reduced secretion of Th1 cytokines (TNF-alpha and IFN-gamma) produced in response to MOG-35-55 peptide, and to a lesser degree purified protein derivative and Con A, but had no inhibitory effect on serum Ab levels to MOG-35-55 peptide. Abs specific for both the peptide and MHC moieties of the RTLs were also present after treatment with EAE, but these Abs had only a minor enhancing effect on T cell activation in vitro. These data demonstrate the powerful tolerance-inducing therapeutic effects of VG312 on MOG peptide-induced EAE in transgenic DR2 mice and support the potential of this approach to inhibit myelin Ag-specific responses in multiple sclerosis patients.

Transfer of severe experimental autoimmune encephalomyelitis by IL-12- and IL-18-potentiated T cells is estrogen sensitive

The aim of this study was to evaluate the roles of IL-18 and IL-12 in potentiating the encephalitogenic activity of T cell lines specific for myelin oligodendrocyte glycoprotein (MOG(35-55)). MOG-specific T cells stimulated with anti-CD3 and anti-CD28 in the presence of IL-12 or IL-18 alone transferred only mild experimental autoimmune encephalomyelitis (EAE) into a low percentage of recipients. However, T cells cocultured with both cytokines transferred aggressive clinical and histological EAE into all recipients. Coculture of T cells with IL-12 enhanced the secretion of IFN-gamma, but not TNF-alpha, whereas coculture with IL-18 enhanced the secretion of TNF-alpha, but not INF-gamma. However, coculture with both IL-18 and IL-12 induced high levels of both TNF-alpha and IFN-gamma. Additionally, IL-12 selectively enhanced mRNA expression of CCR5, whereas IL-18 selectively enhanced the expression of CCR4 and CCR7, and CCR4 and CCR5 were coexpressed on the surface of T cells cocultured with IL-12 and IL-18. Finally, estrogen treatment, previously found to inhibit both TNF-alpha and IFN-gamma production, completely abrogated all signs of passive EAE. These data demonstrate that optimal potentiation of encephalitogenic activity can be achieved by conditioning MOG-specific T cells with the combination of IL-12 and IL-18, which, respectively, induce the secretion of IFN-gamma/CCR5 and TNF-alpha/CCR4/CCR7, and that estrogen treatment, which is known to inhibit both proinflammatory cytokines, can completely ablate this aggressive form of passive EAE.

Oral feeding with ethinyl estradiol suppresses and treats experimental autoimmune encephalomyelitis in SJL mice and inhibits the recruitment of inflammatory cells into the central nervous system

There is much interest in the possible ameliorating effects of estrogen on various autoimmune diseases. We previously established the protective effects of 17 beta-estradiol (E2) on experimental autoimmune encephalomyelitis (EAE). In the current study we investigated the effectiveness of oral treatment with ethinyl estradiol (EE) on EAE and the mechanisms involved. Ethinyl estradiol is a semisynthetic estrogen compound found in birth control pills, and its chemical structure allows this compound to retain activity when given orally. We found that oral EE, like E2, drastically suppressed EAE induced by proteolipid protein 139-151 peptide when given at initiation of EAE. However, unlike E2, EE reduced clinical severity when given after the onset of clinical signs. Treatment with EE significantly decreased the secretion of proinflammatory cytokines (IFN-gamma, TNF-alpha, and IL-6) by activated T cells as well as the expression of a key matrix metalloproteinase, disease-mediating chemokines/receptors, and IgG2a levels, but increased the expression of TGF-beta 3 in the CNS. The absence of infiltrating lymphocytes together with the suppression of cytokines, matrix metalloproteinase, and chemokines/receptors suggests that EE, like E2, protects mice from EAE by inhibiting the recruitment of T cells and macrophages into the CNS. These results suggest that oral ethinyl estradiol might be a successful candidate as therapy for multiple sclerosis.

Endogenous CD4+BV8S2- T cells from TG BV8S2+ donors confer complete protection against spontaneous experimental encephalomyelitis (Sp-EAE) in TCR transgenic, RAG-/- mice

To investigate regulatory mechanisms which naturally prevent autoimmune diseases, we adopted the genetically restricted immunodeficient (RAG-1(-/-)) myelin basic protein (MBP)-specific T cell receptor (TCR) double transgenic (T/R-) mouse model of spontaneous experimental autoimmune encephalomyelitis (Sp-EAE). Sp-EAE can be prevented after transfer of CD4+splenocytes from naïve immunocompetent mice. RAG-1+ double transgenic (T/R+) mice do not develop Sp-EAE due to the presence of a very small population (about 2%) of non-Tg TCR specificities. In this study, CD4+BV8S2+ T cells that predominate in T/R+ mice, and three additional populations, CD4+BV8S2-, CD4-CD8-BV8S2+, and CD4-CD8+BV8S2+ T cells that expanded in T/R+ mice after immunization with MBP-Ac1-11 peptide, were studied for their ability to prevent Sp-EAE in T/R- mice. Only the CD4+BV8S2- T cell population conferred complete protection against Sp-EAE, similar to unfractionated splenocytes from non-Tg donors, whereas CD4-CD8-BV8S2+ and CD4+BV8S2+ T cells conferred partial protection. In contrast, CD4-CD8+BV8S2+ T cells had no significant protective effects. The highly protective CD4+BV8S2- subpopulation was CD25+, contained non-clonotypic T cells, and uniquely expressed the CCR4 chemokine receptor. Protected recipient T/R- mice had marked increases in CD4+CD25+ Treg-like cells, retention of the pathogenic T cell phenotype in the spleen, and markedly reduced inflammation in CNS tissue. Partially protective CD4+BV8S2+ and CD4- CD8-BV8S2+ subpopulations appeared to be mainly clonotypic T cells with altered functional properties. These three Sp-EAE protective T cell subpopulations possessed distinctive properties and induced a variety of effects in T/R- recipients, thus implicating differing mechanisms of protection.

Estrogen inhibition of EAE involves effects on dendritic cell function

Estrogen has been found to have suppressive effects on the induction of experimental autoimmune encephalomyelitis (EAE), an animal model for the human disease multiple sclerosis. We have investigated the effects of 17beta-estradiol (E2) treatment on dendritic cells (DCs) in two different mouse models of EAE. The frequency of CD11b(+)/CD11c(+) DCs was significantly decreased in the brain of mice protected from EAE induction by E2 treatment. In addition, the frequency of CD11c(+)/CD8alpha(+) DCs producing tumor necrosis factor (TNF)alpha and interferon (IFN)gamma in the spleen of E2-treated mice was dramatically decreased compared to that in control mice with EAE, demonstrating an effect of E2 on DC function. In order to examine E2 effects on DCs in more detail, splenic DCs were cultured in the presence of granulocyte-macrophage colony-stimulating factor (GM-CSF) and interleukin (IL)-4 to promote maturation. E2 pretreatment was found to suppress the ability of cultured DCs bearing a mature phenotype to present Ag to myelin basic protein (MBP)-specific T cells. Analysis of cytokine production demonstrated that E2 decreased TNFalpha, IFNgamma and IL-12 production in mature DCs. In addition, MBP-specific T cells cocultured with E2-pretreated mature DCs in the presence of antigen demonstrated a shift towards production of Th2 cytokines IL-4 and IL-10 and a concomitant decrease in the production of Th1 cytokines TNFalpha and IFNgamma. Thus, E2 treatment appears to have multiple effects on the DC population, which may contribute to a down-regulation or block in the activation of Th1 cells involved in the induction of EAE.

A synthetic androstene derivative and a natural androstene metabolite inhibit relapsing-remitting EAE

Experimental allergic encephalomyelitis (EAE), a Th1 polarized demyelinating disease of the central nervous system (CNS), shares many pathological and clinical similarities with multiple sclerosis (MS), and thus represents an attractive animal model for this disease. The goal of this study was to evaluate the suppressive effects of fluasterone (HE2500), a synthetic androstene derivative, and androstenetriol (HE2200), a natural androstene hormone on EAE. SJL mice were immunized with proteolipid protein (PLP) 139-151 peptide/CFA to induce EAE. Starting on day -7, animals were given daily injections (s.c.) of derivatives (3.0 mg) in vehicle, or vehicle alone for 33 days. Both HE2500 and HE2200 significantly delayed the onset, reduced the peak clinical score and cumulative disease index of EAE, and prevented or significantly attenuated relapses. Lower doses or other routes of administration were less effective. Moreover, T cells from treated mice had significantly reduced PLP 139-151-specific T cell proliferation responses and reduced numbers of TNF-alpha- and IFN-gamma-producing cells in the CNS. Daily treatment of B10.PL mice with HE2500, starting on day 0, completely prevented the development of disease in these animals. Finally, SJL mice treated with HE2500 at EAE onset showed significantly reduced mean clinical scores. Thus, these compounds, which have been reported to have a few androgenic or estrogenic side effects, appear to have a potent inhibitory activity in EAE. These observations suggest that HE2500 and/or HE2200 limit the production of autoimmune Th1 associated cytokines, and ultimately may be beneficial for patients with MS or other autoimmune diseases.

Estrogen inhibits systemic T cell expression of TNF-alpha and recruitment of TNF-alpha(+) T cells and macrophages into the CNS of mice developing experimental encephalomyelitis

Estrogen treatment has been found to have suppressive activity in several models of autoimmunity. To investigate the mechanism of 17 beta-estradiol (E2) suppression of experimental autoimmune encephalomyelitis, we evaluated E2 effects on TNF-alpha expression in the central nervous system (CNS) and spleen of C57BL/6 mice immunized with MOG 35-55/CFA. Kinetic analysis demonstrated that E2 treatment drastically decreased the recruitment of total inflammatory cells as well as TNF-alpha(+) macrophages and T cells into the CNS at disease onset. In contrast, E2 had only moderate effects on the relatively high constitutive TNF-alpha expression by resident CNS microglial cells. E2 treatment also had profound inhibitory effects on expression of TNF-alpha by splenic CD4(+) T cells, including those responsive to MOG 35-55 peptide. We propose that the mechanism of E2 protection may involve both systemic inhibition of TNF-alpha expression and local (CNS) recruitment of inflammatory cells, with modest effects on TNF-alpha expression by resident CNS microglial cells.

Effects of cytokine deficiency on chemokine expression in CNS of mice with EAE

Although both cytokines and chemokines have been implicated in the pathogenesis of clinical and histological EAE, their interactions in vivo have not yet been clearly established. To address this issue, we evaluated expression of chemokines and receptors in the CNS of wild-type control and cytokine deficient mice at the peak of EAE induced with MOG-35-55 peptide in CFA. Our results demonstrate that: 1) expression of most chemokines/receptors was drastically inhibited in TNF-alpha deficient mice, and was reflective of delayed onset and reduced severity of EAE; 2) distinct patterns of chemokine expression occurred in various other cytokine knockout mice that did not significantly affect expression of clinical EAE; 3) there was a strong association between expression of MIP-1alpha, MIP-2 and MCP-1 in CNS and overall severity of EAE in wild-type and cytokine knockout mice; and 4) among CNS infiltrating cells at the peak of EAE, macrophages and CD8+ T cells were the primary cellular source of most of the chemokines. Of note, we present evidence that TNF-alpha may be involved in regulating RANTES and MIP-1alpha, and that IL-4 may be involved in regulating MCP-1. Our results not only identify the cellular source of chemokines in CNS, but also implicate MIP-1alpha, MIP-2, and MCP-1 in controlling CNS inflammation and severity of EAE.

Inhibitory effects of incomplete Freund's adjuvant on experimental autoimmune encephalomyelitis

Freund's incomplete adjuvant (IFA), an aqueous/oil emulsion that is widely used in combination with antigenic proteins and peptides to induce tolerance, is considered to be immunologically inert. However, sporadic reports indicate that IFA may itself have inhibitory properties on induction of adjuvant induced arthritis and spontaneous diabetes. In the current study, the effects of IFA/saline were evaluated on the induction of experimental autoimmune encephalomyelitis (EAE) in three different strains of mice. IFA/saline given i.p. in two doses of > 100 microl 10 days apart were found to inhibit EAE induction to varying degrees in all three strains of mice in a dose dependent fashion. The IFA/saline injections inhibited both mitogen and antigen-induced T cell proliferation, induced elevated secretion of IFN-gamma and IL-10 by neuroantigen specific T cells, and reduced expression of cytokines, chemokines, and chemokine receptors of CNS-infiltrating mononuclear cells. These data demonstrate for the first time a direct inhibitory effect of IFA/saline on EAE, and re-emphasize the need to properly control experiments using IFA to induce antigen-specific tolerance.

Evaluation of the effects of 17beta-estradiol (17beta-e2) on gene expression in experimental autoimmune encephalomyelitis using DNA microarray

The aim of this study was to identify immune-related genes affected by treatment with 17beta-estradiol (17beta-E2) that contribute to protection of T cell antigen receptor double transgenic mice from experimental autoimmune encephalomyelitis (EAE). The Affymetrix microarray system was used to screen more than 12,000 genes from E2-treated mice protected from EAE vs. control mice with severe EAE. In general, E2 treatment affected about 10% of the genes tested, but only 18 cytokine, chemokine/receptor, adhesion molecule, or activation genes were up- or down-regulated more than 2.4-fold by E2 treatment. Down-regulated genes included TNFalpha (an important proinflammatory cytokine in EAE); peptidoglycan recognition proteins (Pgrp); regulated on activation, normal T cell expressed and secreted (RANTES); and neural cell adhesion molecule (MCP-1). Up-regulated genes included cytotoxic T lymphocyte antigen-4 (CTLA-4; known to inhibit T cell activation), TGFbeta3, IL-18, and two interferon-gamma-induced genes, the chemokines: monocyte chemoattractant protein-1 (MCP-1) and macrophage inflammatory protein-1beta (MIP-1beta), vascular cell adhesion molecule (VCAM), and disintegrin metalloprotease (thought to regulate TNFalpha production). These results implicate a limited set of known and previously unsuspected E2-sensitive genes that may be crucial for inhibition of EAE and potentially the human disease, multiple sclerosis.

Rudimentary TCR signaling triggers default IL-10 secretion by human Th1 cells

Understanding the process of inducing T cell activation has been hampered by the complex interactions between APC and inflammatory Th1 cells. To dissociate Ag-specific signaling through the TCR from costimulatory signaling, rTCR ligands (RTL) containing the alpha1 and beta1 domains of HLA-DR2b (DRA*0101:DRB1*1501) covalently linked with either the myelin basic protein peptide 85-99 (RTL303) or CABL-b3a2 (RTL311) peptides were constructed to provide a minimal ligand for peptide-specific TCRs. When incubated with peptide-specific Th1 cell clones in the absence of APC or costimulatory molecules, only the cognate RTL induced partial activation through the TCR. This partial activation included rapid TCR zeta-chain phosphorylation, calcium mobilization, and reduced extracellular signal-related kinase activity, as well as IL-10 production, but not proliferation or other obvious phenotypic changes. On restimulation with APC/peptide, the RTL-pretreated Th1 clones had reduced proliferation and secreted less IFN-gamma; IL-10 production persisted. These findings reveal for the first time the rudimentary signaling pattern delivered by initial engagement of the external TCR interface, which is further supplemented by coactivation molecules. Activation with RTLs provides a novel strategy for generating autoantigen-specific bystander suppression useful for treatment of complex autoimmune diseases.

Diminished frequency of interleukin-10-secreting, T-cell receptor peptide-reactive T cells in multiple sclerosis patients might allow expansion of activated memory T cells bearing the cognate BV gene

T cells responsive to T-cell receptor (TCR) determinants may regulate pathogenic Th1 responses in patients with multiple sclerosis (MS) through interleukin (IL)-10-dependent bystander suppression. In this study, innate IL-10- and interferon (IFN)-gamma-secreting T cells responsive to TCR peptides were quantified in peripheral blood mononuclear cells of MS patients and healthy controls (HC) using the ELISPOT assay. Most HC had vigorous IL-10 but low IFN-gamma frequencies to BV5S2 and BV6S1 peptides. In contrast, MS patients had significantly lower IL-10 frequency responses to the TCR peptides but normal responses to concanavalin A. Patients undergoing TCR-peptide vaccination had moderate responses that fluctuated in concert with vaccination. In an MS patient and HC, expression of BV6S1 by activated memory T cells was inversely associated with the presence of IL-10-secreting BV6S1-reactive T cells. These results suggest that MS patients have diminished frequencies of innate TCR-reactive T cells that may allow oligoclonal expansion of activated autoreactive Th1 effector cells expressing cognate V genes.

17 beta-estradiol inhibits cytokine, chemokine, and chemokine receptor mRNA expression in the central nervous system of female mice with experimental autoimmune encephalomyelitis

Cytokines and chemokines govern leukocyte trafficking, thus regulating inflammatory responses. In this study, the anti-inflammatory effects of low dose 17 beta-estradiol were evaluated on chemokine, chemokine receptor, and cytokine expression in the spinal cords (SC) of BV8S2 transgenic female mice during acute and recovery phases of experimental autoimmune encephalomyelitis (EAE). In EAE protected mice, 17 beta-estradiol strongly inhibited mRNA expression of the chemokines RANTES, MIP-1 alpha, MIP-2, IP-10, and MCP-1, and of the chemokine receptors CCR1, CCR2 and CCR5 at both time points. Conversely, ovariectomy, which abrogated basal 17 beta-estradiol levels and increased the severity of EAE, enhanced the expression of MIP-1 alpha and MIP-2 that were over-expressed by inflammatory mononuclear cells in SC. 17 beta-estradiol inhibited expression of LT-beta, TNF-alpha, and IFN-gamma in SC, but had no effect on IL-4 or IL-10, indicating reduced inflammation but no deviation toward a Th2 response. Interestingly, elevated expression of CCR1 and CCR5 by lymph node cells was also inhibited in 17 beta-estradiol treated mice with EAE. Low doses of 17 beta-estradiol added in vitro to lymphocyte cultures had no direct effect on the activation of MBP-Ac1-11 specific T cells, and only at high doses diminished production of IFN-gamma, but not IL-12 or IL-10. These results suggest that the beneficial effects of 17 beta-estradiol are mediated in part by strong inhibition of recruited inflammatory cells, resulting in reduced production of inflammatory chemokines and cytokines in CNS, with modest effects on encephalitogenic T cells that seem to be relatively 17 beta-estradiol insensitive.

TCR peptide therapy in human autoimmune diseases

Inflammatory Th1 cells reacting to tissue/myelin derived antigens likely contribute to the pathogenesis of diseases such as multiple sclerosis (MS), rheumatoid arthritis (RA), and psoriasis. One regulatory mechanism that may be useful for treating autoimmune diseases involves an innate second set of Th2 cells specific for portions of the T cell receptor of clonally expanded pathogenic Th1 cells. These Th2 cells are programmed to respond to internally modified V region peptides from the T cell receptor (TCR) that are expressed on the Th1 cell surface in association with major histocompatibility molecules. Once the regulatory Th2 cells are specifically activated, they may inhibit inflammatory Th1 cells through a non-specific bystander mechanism. A variety of strategies have been used by us to identify candidate disease-associated TCR V genes present on pathogenic Th1 cells, including BV5S2, BV6S5, and BV13SI in MS, BV3, BV14, and BV17 in RA, and BV3 and BV13S1 in psoriasis. TCR peptides corresponding to the mid region of these BV genes were found to be consistently immunogenic in vivo when administered either i.d. in saline or i.m. in incomplete Freund's adjuvant (IFA). In MS patients, repeated injection of low doses of peptides (100-300 microg) significantly boosted the number of TCR-reactive Th2 cells. These activated cells secreted cytokines, including IL-10, that are known to inhibit inflammatory Th1 cells. Cytokine release could also be induced in TCR-reactive Th2 cells by direct cell-cell contact with Th1 cells expressing the target V gene. These findings indicate the potential of regulatory Th2 cells to inhibit not only the target Th1 cells, but also bystander Th1 cells expressing different V genes specific for other autoantigens. TCR peptide vaccines have been used in our studies to treat a total of 171 MS patients (6 trials), 484 RA patients (7 trials), and 177 psoriasis patients (2 trials). Based on this experience in 824 patients with autoimmune diseases, TCR peptide vaccination is safe and well tolerated, and can produce significant clinical improvement in a subset of patients that respond to immunization. TCR peptide vaccination represents a promising approach that is well-suited for treating complex autoimmune diseases.

Low-dose estrogen therapy ameliorates experimental autoimmune encephalomyelitis in two different inbred mouse strains

It has been proposed that homeostatic levels of estrogen can enhance female susceptibility to autoimmunity, whereas the heightened levels of estrogen associated with pregnancy are protective. This hypothesis was tested using the mouse model of experimental autoimmune encephalomyelitis (EAE). Diestrus (<100 pg/ml in serum) levels of 17beta-estradiol were found to significantly reduce the clinical manifestations of active EAE in both male and female mice. Estriol was also effective but at doses below those previously established for pregnancy. The reduction in disease severity was accompanied by a coincident reduction in the number and size of inflammatory foci in the CNS of estrogen (17beta-estradiol or estriol)-treated mice. Recipients of encephalitogenic T cells from low-dose estrogen-treated mice developed less severe paralysis than mice receiving T cells from placebo-treated mice. A modest shift in Th1/Th2 balance suggested that low dose estrogen therapy could bias the immune reaction toward a protective anti-inflammatory cytokine response. However, estrogen treatment at the onset of active EAE failed to reduce disease severity, a result that is consistent with the hypothesis that naive cells are more sensitive to sex hormones than differentiated effector cells. These data suggest that treatment with low doses of estrogen can reduce the capacity of developing myelin-reactive T cells to initiate disease and challenges the idea that increased susceptibility to autoimmunity in females is dependent on homeostatic levels of estrogen.

T lymphocytes promote the development of bone marrow-derived APC in the central nervous system

Certain cells within the CNS, microglial cells and perivascular macrophages, develop from hemopoietic myelomonocytic lineage progenitors in the bone marrow (BM). Such BM-derived cells function as CNS APC during the development of T cell-mediated paralytic inflammation in diseases such as experimental autoimmune encephalomyelitis and multiple sclerosis. We used a novel, interspecies, rat-into-mouse T cell and/or BM cell-transfer method to examine the development and function of BM-derived APC in the CNS. Activated rat T cells, specific for either myelin or nonmyelin Ag, entered the SCID mouse CNS within 3-5 days of cell transfer and caused an accelerated recruitment of BM-derived APC into the CNS. Rat APC in the mouse CNS developed from transferred rat BM within an 8-day period and were entirely sufficient for induction of CNS inflammation and paralysis mediated by myelin-specific rat T cells. The results demonstrate that T cells modulate the development of BM-derived CNS APC in an Ag-independent fashion. This previously unrecognized regulatory pathway, governing the presence of functional APC in the CNS, may be relevant to pathogenesis in experimental autoimmune encephalomyelitis, multiple sclerosis, and/or other CNS diseases involving myelomonocytic lineage cells.

Rat RT1.B-transfected fibroblast lines process and present myelin antigens and activate T cells to induce experimental autoimmune encephalomyelitis

The genes encoding the Lewis rat RT1.B molecule (MHC Class II I-A equivalent) were transfected and expressed in mouse DAP.3 fibroblast cells together with the gene encoding the mouse ICAM-1 molecule. Both molecules were stably expressed on the cell surface of DAP.3 cells under longterm culture conditions. The RT1.B/mICAM-1 transfectants presented antigen in a specific manner to a RT1. B-restricted rat T cell hybridoma specific for the 69-89 peptide of myelin basic protein (BP). In addition, the transfectants were able to present antigen to a BP69-89-specific rat T cell line. Presentation to a RT1.D (MHC Class II I-E equivalent)-restricted BP87-99-specific T cell line was minimal. Production of the Th1 cytokine IFN-gamma by BP69-89-specific T cells when stimulated by RT1.B/mICAM-1 transfectants correlated very well with proliferation to specific antigen. Moreover, RT1.B-transfected DAP.3 cells sufficiently stimulated BP69-89-specific T cells such that they were able to transfer experimental autoimmune encephalomyelitis (EAE) to Lewis rat recipients. Thus, the RT1.B molecule is functionally expressed on the surface of transfected Dap.3 fibroblasts and is capable of MHC Class II-restricted, antigen-specific presentation to rat T cells.

Human TCR as antigen: homologies and potentially cross-reactive HLA-DR2-restricted epitopes within the AV and BV CDR2 loops

The major function of the T-cell receptor is to confer antigen specificity to T cells. However, nascent TCR proteins that are not assembled into functional heterodimers may be processed and displayed with self MHC molecules on the T-cell surface, and are thought to be the genesis of autoregulatory T cells that can limit inflammatory responses through T-T network interactions. In previous work, we and others have exploited this natural regulatory system using TCR peptides to amplify regulatory T cells that potentially can treat human autoimmune diseases such as multiple sclerosis (MS) and arthritis. The development of this approach is limited by the diversity of human TCR V gene sequences, and by lack of knowledge of exactly which regions of the V gene proteins are immunogenic in association with various MHC alleles. To identify similar amino acid sequences within and among human V gene families that might have immunologic cross reactivity, we aligned 74 known AV and 109 known BV protein sequences into homologous groups using the ClustalX program. Moreover, with a focus on CDR2 peptides that have previously been used to induce regulatory T cells in clinical trials, we established homologous peptide groups, and then identified the optimal amino acid motifs for binding to two alleles, HLA-DRB1*1501 and DRB5*0101, that have been associated with susceptibility to MS. From this analysis, > 75% of AV and BV CDR2 sequences were predicted to bind with at least moderate avidity to each of the DR2 alleles, thus enhancing the likelihood that they could be antigenic. Further ordering of putative TCR contact residues revealed a different set of homology groupings, including many intrafamily sequence matches and some interfamily matches that might allow immunological cross reactivity. Particularly striking were DRB1*1501-restricted IH-S and IY-S motifs shared by BV11, BV12, and BV13 and BV3, BV12, BV13, and BV17 family members, respectively, and DRB5*0101-restricted RL-H and RL-Y motifs shared by BV11, BV12, and BV13 and BV13 and BV17 family members, respectively. This analysis may be useful in designing an array of clinically useful homologous peptides with optimal MHC binding properties and highly cross-reactive TCR binding motifs.

Regulation of encephalitogenic T cells with recombinant TCR ligands

We have previously described recombinant MHC class II beta1 and alpha1 domains loaded with free antigenic peptides with potent inhibitory activity on encephalitogenic T cells. We have now produced single-chain constructs in which the peptide Ag is genetically encoded within the same exon as the linked beta1 and alpha1 domains, overcoming the problem of displacement of peptide Ag from the peptide binding cleft. We here describe clinical effects of recombinant TCR ligands (RTLs) comprised of the rat RT1.B beta1alpha1 domains covalently linked to the 72-89 peptide of guinea pig myelin basic protein (RTL-201), to the corresponding 72-89 peptide from rat myelin basic protein (RTL-200), or to cardiac myosin peptide CM-2 (RTL-203). Only RTL-201 possessed the ability to prevent and treat active or passive experimental autoimmune encephalomyelitis. Amelioration of experimental autoimmune encephalomyelitis was associated with a selective inhibition of proliferation response and cytokine production by Ag-stimulated lymph node T cells and a drastic reduction in the number of encephalitogenic and recruited inflammatory cells infiltrating the CNS. The exquisitely selective inhibition could be observed between molecules that differ by a single methyl group (the single amino acid residue difference between RTL-200 (threonine) and RTL-201 (serine) at position 80 of the myelin basic protein peptide). These novel RTLs provide a platform for developing potent and selective human diagnostic and therapeutic agents for treatment of autoimmune disease.

Immunoregulation of encephalitogenic MBP-NAc1-11-reactive T cells by CD4+ TCR-specific T cells involves IL-4, IL-10 and IFN-gamma

The generation of TCR transgenic (Tg) mice expressing a BV8S2 (Vbeta8 subfamily 2) chain specific for the encephalitogenic NAc1-11 region of MBP provides a unique system for evaluating the mechanisms involved in anti-TCR immunoregulation of EAE. In a previous study, we showed that vaccination with BV8S2 protein induced specific T cells that inhibited proliferation responses and encephalitogenic activity of MBP-reactive T cells in vitro, and resulted in a skewed production of Th2 cytokines by the MBP-reactive T cells. These data suggested that regulation of the encephalitogenic T cells was mediated by inhibitory cytokines rather than through a deletional mechanism. In the current study, we have employed the BV8S2 Tg mouse model to address the issue of which cytokines produced by anti-TCR-reactive T cells can regulate the function of encephalitogenic Th1 cells. Utilizing neutralizing anti-cytokine antibodies to reverse inhibitory effects of supernatants from BV8S2-specific T cells, we found that IL-4, IL-10, and to a lesser extent, IFN-gamma and TGF-beta, were the major regulatory cytokines responsible for inhibiting encephalitogenic activity, proliferation, and IFN-gamma secretion of MBP-NAc1-11-reactive Th1 cells. These results indicate that cytokine regulation is the major mechanism through which TCR specific CD4+ T cells regulate encephalitogenic and potentially other bystander Th1 cells.

Estrogen potentiates treatment with T-cell receptor protein of female mice with experimental encephalomyelitis

Transgenic mice expressing the BV8S2 chain, which is specific for the myelin basic protein determinant Ac1-11, possess a naturally induced set of regulatory T cells directed against BV8S2. Further activation of anti-BV8S2 T cells in male mice with recombinant BV8S2 protein can inhibit IFN-gamma release by Ac1-11-specific T cells through a cytokine-driven mechanism and prevent induction of experimental autoimmune encephalomyelitis (EAE). In contrast, naive female mice possess fewer anti-BV8S2-reactive T cells, and treatment with BV8S2 delayed but did not prevent EAE. We here demonstrate that combining T-cell receptor (TCR) vaccination with supplemental estrus doses of estrogen potentiated IL-10 production by anti-BV8S2-reactive T cells and induced Ac1-11-specific T cells to produce IL-10 and TGF-beta. This combined treatment resulted in full protection against EAE, which was not observed with either therapy alone. These findings imply that supplemental estrogen can enhance the efficacy of TCR-based immunotherapy for autoimmune diseases that predominate in females.

Reduced chemokine and chemokine receptor expression in spinal cords of TCR BV8S2 transgenic mice protected against experimental autoimmune encephalomyelitis with BV8S2 protein

The perivascular transmigration and accumulation of macrophages and T lymphocytes in the CNS of mice with experimental autoimmune encephalomyelitis (EAE) may be partly regulated by low m.w. chemotactic cytokines. Using the RNase protection assay and ELISA, we quantified expression of chemokines and chemokine receptors in the spinal cord (SC), brain, and lymph nodes of BV8S2 transgenic mice that developed or were protected from EAE by vaccination with BV8S2 protein. In paralyzed control mice, the SC had increased cellular infiltration and strong expression of the chemokines RANTES, IFN-inducible 10-kDa protein, and monocyte chemoattractant protein-1 and the cognate chemokine receptors CCR1, CCR2, and CCR5, with lower expression of macrophage-inflammatory protein (MIP)-1alpha, MIP-1beta, and MIP-2; whereas brain had less infiltration and a lower expression of a different pattern of chemokines and receptors. In TCR-protected mice, there was a decrease in the number of inflammatory cells in both SC and brain. In SC, the reduced cellular infiltrate afforded by TCR vaccination was commensurate with profoundly reduced expression of chemokines and their cognate chemokine receptors. In brain, however, TCR vaccination did not produce significant changes in chemokine expression but resulted in an increased expression of CCR3 and CCR4 usually associated with Th2 cells. In contrast to CNS, lymph nodes of protected mice had a significant increase in expression of MIP-2 and MIP-1beta but no change in expression of chemokine receptors. These results demonstrate that TCR vaccination results in selective reduction of inflammatory chemokines and chemokine receptors in SC, the target organ most affected during EAE.