A human tissue-based functional assay platform to evaluate the immune function impact of small molecule inhibitors that target the immune system.

While the immune system is essential for the maintenance of the homeostasis, health and survival of humans, aberrant immune responses can lead to chronic inflammatory and autoimmune disorders. Pharmacological modulation of drug targets in the immune system to ameliorate disease also carry a risk of immunosuppression that could lead to adverse outcomes. Therefore, it is important to understand the 'immune fingerprint' of novel therapeutics as they relate to current and, clinically used immunological therapies to better understand their potential therapeutic benefit as well as immunosuppressive ability that might lead to adverse events such as infection risks and cancer. Since the mechanistic investigation of pharmacological modulators in a drug discovery setting is largely compound- and mechanism-centric but not comprehensive in terms of immune system impact, we developed a human tissue based functional assay platform to evaluate the impact of pharmacological modulators on a range of innate and adaptive immune functions. Here, we demonstrate that it is possible to generate a qualitative and quantitative immune system impact of pharmacological modulators, which might help better understand and predict the benefit-risk profiles of these compounds in the treatment of immune disorders.

Inhibition of RORγT Skews TCRα Gene Rearrangement and Limits T Cell Repertoire Diversity.

Recent studies have elucidated the molecular mechanism of RORγT transcriptional regulation of Th17 differentiation and function. RORγT was initially identified as a transcription factor required for thymopoiesis by maintaining survival of CD4+CD8+ (DP) thymocytes. While RORγ antagonists are currently being developed to treat autoimmunity, it remains unclear how RORγT inhibition may impact thymocyte development. In this study, we show that in addition to regulating DP thymocytes survival, RORγT also controls genes that regulate thymocyte migration, proliferation, and T cell receptor (TCR)α selection. Strikingly, pharmacological inhibition of RORγ skews TCRα gene rearrangement, limits T cell repertoire diversity, and inhibits development of autoimmune encephalomyelitis. Thus, targeting RORγT not only inhibits Th17 cell development and function but also fundamentally alters thymic-emigrant recognition of self and foreign antigens. The analysis of RORγ inhibitors has allowed us to gain a broader perspective of the diverse function of RORγT and its impact on T cell biology.

Drug-induced hemolytic anemia and thrombocytopenia associated with alterations of cell membrane lipids and acanthocyte formation.

CXCR3 is a chemokine receptor, upregulated upon activation of T cells and expressed on nearly 100% of T cells in sites of inflammation. SCH 900875 is a selective CXCR3 receptor antagonist. Thrombocytopenia and severe hemolytic anemia with acanthocytosis occurred in rats at doses of 75, 100, and 150 mg/kg/day. Massively enlarged spleens corresponded histologically to extramedullary hematopoiesis, macrophages, and hemosiderin pigment and sinus congestion. Phagocytosed erythrocytes and platelets were within splenic macrophages. IgG and/or IgM were not detected on erythrocyte and platelet membranes. Ex vivo increased osmotic fragility of RBCs was observed. Lipid analysis of the RBC membrane revealed modifications in phosphatidylcholine, overall cholesterol, and/or sphingomyelin. Platelets exhibited slender filiform processes on their plasma membranes, analogous to those of acanthocytes. The presence of similar morphological abnormalities in acanthocytes and platelets suggests that possibly similar alterations in the lipid composition of the plasma membrane have taken place in both cell types. This phenotype correlated with alterations in plasma lipids (hypercholesterolemia and low triglycerides) that occurred after SCH 900875 administration, although other factors cannot be excluded. The increased cell destruction was considered triggered by alterations in the lipid profile of the plasma membranes of erythrocytes and platelets, as reflected morphologically.

Kinetic assessment and therapeutic modulation of metabolic and inflammatory profiles in mice on a high-fat and cholesterol diet.

The kinetics of metabolic and inflammatory parameters associated with obesity were evaluated in a murine diet-induced obesity (DIO) model using a diet high in fat and cholesterol. Cellular infiltration and mediator production were assessed and shown to be therapeutically modulated by the PPARgamma agonist rosiglitazone. C57BL/6 mice were maintained on a 45% fat/ 0.12% cholesterol (HF/CH) or Chow diet for 3, 6, 16, or 27 weeks. Flow cytometry was employed to monitor peripheral blood monocytes and adipose tissue macrophages (ATM). Gene expression and protein analysis methods were used to evaluate mediator production from total epididymal fat (EF), stromal vascular fraction (SVF), and sorted SVF cells. To investigate therapeutic intervention, mice were fed a HF/CH diet for 12 weeks and then a diet formulated with rosiglitazone (5 mg/kg) for an additional 6 weeks. A HF/CH diet correlated with obesity and a dramatic proinflammatory state. Therapeutic intervention with rosiglitazone attenuated the HF/CH induced inflammation. In addition, a novel population was found that expressed the highest levels of the pro-inflammatory mediators CCL2 and IL-6.

Characterization of a murine keyhole limpet hemocyanin (KLH)-delayed-type hypersensitivity (DTH) model: role for p38 kinase.

Molecular and cellular assessment of dermal delayed-type hypersensitivity (DTH) responses is a useful approach for evaluating the mechanism of action (MOA) of immunomodulatory agents. In the present report, we characterized the delayed-type hypersensitivity response induced by keyhole limpet hemocyanin (KLH), and validated its utility by evaluating an immunomodulator, BIRB-796. Intradermal KLH challenge of the ear pinna following subcutaneous antigen sensitization resulted in a pronounced skin inflammation that peaked at 24-48h. At the molecular level, there was an activation of 3 mitogen-activated protein kinases (MAPKs: p38, JNK and ERK), an induction of the chemokines CCL2/JE, CXCL2/Mip-2, CXCL1/KC, CCL3/Mip-1alpha CCL4/Mip-1beta and CXCL10/IP-10, and expression of the cytokines IL-1beta and IL-10 in the ear parenchyma. Modulation of TNFalpha protein level was only detected in ex-vivo ear whole organ cultures (EWOC). Consistent with this inflammatory profile there was an infiltration of neutrophils and mononuclear cells into the ear parenchyma. BIRB-796, a potent allosteric p38 MAPK inhibitor attenuated the ear swelling response, which correlated with a reduced inflammatory profile. BIRB-796 inhibited p38 but not JNK or ERK kinase activation, decreased multiple chemokines which correlated with a decrease in the infiltration of neutrophils and macrophages; CD4 T cells were modesty reduced. Similarly, there was a decrease of levels of cytokines including IL-1beta, IL-10 and TNFalpha. These data support the utility of this model for evaluating immunomodulators on skin inflammation and suggest that modulation of p38 kinase may be of therapeutic value for the treatment of inflammatory skin conditions.

Chronic treatment with the gamma-secretase inhibitor LY-411,575 inhibits beta-amyloid peptide production and alters lymphopoiesis and intestinal cell differentiation.

Inhibition of gamma-secretase, one of the enzymes responsible for the cleavage of the amyloid precursor protein (APP) to produce the pathogenic beta-amyloid (Abeta) peptides, is an attractive approach to the treatment of Alzheimer disease. In addition to APP, however, several other gamma-secretase substrates have been identified (e.g. Notch), and altered processing of these substrates by gamma-secretase inhibitors could lead to unintended biological consequences. To study the in vivo consequences of gamma-secretase inhibition, the gamma-secretase inhibitor LY-411,575 was administered to C57BL/6 and TgCRND8 APP transgenic mice for 15 days. Although most tissues were unaffected, doses of LY-411,575 that inhibited Abeta production had marked effects on lymphocyte development and on the intestine. LY-411,575 decreased overall thymic cellularity and impaired intrathymic differentiation at the CD4(-)CD8(-)CD44(+)CD25(+) precursor stage. No effects on peripheral T cell populations were noted following LY-411,575 treatment, but evidence for the altered maturation of peripheral B cells was observed. In the intestine, LY-411,575 treatment increased goblet cell number and drastically altered tissue morphology. These effects of LY-411,575 were not seen in mice that were administered LY-D, a diastereoisomer of LY-411,575, which is a very weak gamma-secretase inhibitor. These studies show that inhibition of gamma-secretase has the expected benefit of reducing Abeta in a murine model of Alzheimer disease but has potentially undesirable biological effects as well, most likely because of the inhibition of Notch processing.

Impairment of leukocyte trafficking in a murine pleuritis model by IL-4 and IL-10.

We have characterized leukocyte migration to the pleural cavity in a methylated-BSA (mBSA)-induced model of murine delayed-type hypersensitivity and evaluated the ability of IL-4 and IL-10 to modulate this response. Neutrophils, macrophages, T cells, and dendritic cells migrated to the pleural cavity in a time-dependent fashion following direct intrapleural antigen challenge, with neutrophils comprising the majority of exudate leukocytes in the cavity within the first 24 h and the number of mononuclear cells increasing at later times. Real-time quantitative PCR analysis of infiltrating leukocytes revealed a marked elevation of steady-state mRNA levels of IL-1beta and TNFalpha and the chemokines KC, MIP-2, CXCL9, CXCL10, CXCL11, CCL2, CCL3, and CCL4 at 6 h postchallenge, which diminished over time. In contrast, gammaIFN mRNA levels were maximal at 24 h and CCL5 expression was sustained throughout 72 h. ELISA analysis of pleural exudate fluid revealed significant elevations of KC and CCL2 protein levels at 6 h postantigen challenge and a peak increase in gammaIFN protein at 24 h, confirming our mRNA observations. Administration of recombinant murine IL-4 or IL-10 prior to challenge significantly blocked cell trafficking to the pleural cavity as well as peak levels of exudate gammaIFN, with IL-4 being more potent in impairing these responses. IL-4 administration also increased the proportion of naive T cells in the pleural cavity, as judged by CD62L and CD45RB expression. These results indicate that this in vivo model demonstrates a pattern of events associated with Th1-mediated leukocyte trafficking and underscore the potential utility of this in vivo model for evaluating therapeutic inhibitors of leukocyte trafficking.

Posttransplantation cyclophosphamide facilitates engraftment of major histocompatibility complex-identical allogeneic marrow in mice conditioned with low-dose total body irradiation.

Cyclophosphamide (Cy) has been studied extensively for its immunosuppressive properties and is frequently combined with total body irradiation (TBI) as conditioning prior to HLA-identical allogeneic blood or marrow transplantation (alloBMT) in humans. Because Cy is most effective at suppressing host-versus-graft reactions when the drug is given after the transplantation (Mayumi H et al. Transplant Proc. 1986;18:363-369), we investigated whether posttransplantation Cy could prevent rejection of allogeneic marrow in mice conditioned with low-dose TBI. In a mouse model, posttransplantation Cy reduced the dose of TBI required from 500 cGy to < or = 200 cGy for the engraftment of 10 million major histocompatibility complex (MHC)-identical marrow cells in 100% of recipients. In animals conditioned with low-dose TBI and posttransplantation Cy, donor chimerism was proportional to the dose of TBI, was present in multiple hematopoietic lineages, and was associated with the indefinite survival of donor-strain skin grafts. In contrast, animals conditioned with either TBI alone or posttransplantation Cy alone failed to achieve engraftment after alloBMT and contained antidonor cytotoxic T-cells. Although <5% donor chimerism could be induced without TBI by transplanting > or = 50 million MHC-identical cells and administering posttransplantation Cy, the addition of low-dose TBI reduced the dose of donor cells required for alloengraftment and increased long-term donor chimerism to >50%. These data demonstrate that low-dose TBI and posttransplantation Cy cooperate to prevent graft rejection following the transplantation of standard doses of MHC-identical marrow cells.