Pulmonary Fibrosis Stakeholder Summit: A Joint NHLBI, Three Lakes Foundation, and Pulmonary Fibrosis Foundation Workshop Report.

Despite progress in elucidation of disease mechanisms, identification of risk factors, biomarker discovery, and the approval of two medications to slow lung function decline in idiopathic pulmonary fibrosis and one medication to slow lung function decline in progressive pulmonary fibrosis, pulmonary fibrosis remains a disease with a high morbidity and mortality. In recognition of the need to catalyze ongoing advances and collaboration in the field of pulmonary fibrosis, the NHLBI, the Three Lakes Foundation, and the Pulmonary Fibrosis Foundation hosted the Pulmonary Fibrosis Stakeholder Summit on November 8-9, 2022. This workshop was held virtually and was organized into three topic areas: 1) novel models and research tools to better study pulmonary fibrosis and uncover new therapies, 2) early disease risk factors and methods to improve diagnosis, and 3) innovative approaches toward clinical trial design for pulmonary fibrosis. In this workshop report, we summarize the content of the presentations and discussions, enumerating research opportunities for advancing our understanding of the pathogenesis, treatment, and outcomes of pulmonary fibrosis.

Folate Receptor Beta as a Direct and Indirect Target for Antibody-Based Cancer Immunotherapy.

Folate receptor beta (FRß) is a folate binding receptor expressed on myeloid lineage hematopoietic cells. FRß is commonly expressed at high levels on malignant blasts in patients with acute myeloid leukemia (AML), as well as on M2 polarized tumor-associated macrophages (TAMs) in the tumor microenvironment of many solid tumors. Therefore, FRß is a potential target for both direct and indirect cancer therapy. We demonstrate that FRß is expressed in both AML cell lines and patient-derived AML samples and that a high-affinity monoclonal antibody against FRß (m909) has the ability to cause dose- and expression-dependent ADCC against these cells in vitro. Importantly, we find that administration of m909 has a significant impact on tumor growth in a humanized mouse model of AML. Surprisingly, m909 functions in vivo with and without the infusion of human NK cells as mediators of ADCC, suggesting potential involvement of mouse macrophages as effector cells. We also found that TAMs from primary ovarian ascites samples expressed appreciable levels of FRß and that m909 has the ability to cause ADCC in these samples. These results indicate that the targeting of FRß using m909 has the potential to limit the outgrowth of AML in vitro and in vivo. Additionally, m909 causes cytotoxicity to TAMs in the tumor microenvironment of ovarian cancer warranting further investigation of m909 and its derivatives as therapeutic agents in patients with FRß-expressing cancers.

Targeted inhibition of PI3 kinase/mTOR specifically in fibrotic lung fibroblasts suppresses pulmonary fibrosis in experimental models.

Idiopathic pulmonary fibrosis (IPF) is a lethal disease with an average life expectancy of 3 to 5 years. IPF is characterized by progressive stiffening of the lung parenchyma due to excessive deposition of collagen, leading to gradual failure of gas exchange. Although two therapeutic agents have been approved from the FDA for IPF, they only slow disease progression with little impact on outcome. To develop a more effective therapy, we have exploited the fact that collagen-producing myofibroblasts express a membrane-spanning protein, fibroblast activation protein (FAP), that exhibits limited if any expression on other cell types. Because collagen-producing myofibroblasts are only found in fibrotic tissues, solid tumors, and healing wounds, FAP constitutes an excellent marker for targeted delivery of drugs to tissues undergoing pathologic fibrosis. We demonstrate here that a low-molecular weight FAP ligand can be used to deliver imaging and therapeutic agents selectively to FAP-expressing cells. Because induction of collagen synthesis is associated with phosphatidylinositol 3-kinase (PI3K) activation, we designed a FAP-targeted PI3K inhibitor that selectively targets FAP-expressing human IPF lung fibroblasts and potently inhibited collagen synthesis. Moreover, we showed that administration of the inhibitor in a mouse model of IPF inhibited PI3K activation in fibrotic lungs, suppressed production of hydroxyproline (major building block of collagen), reduced collagen deposition, and increased mouse survival. Collectively, these studies suggest that a FAP-targeted PI3K inhibitor might be promising for treating IPF.

Reprogramming of profibrotic macrophages for treatment of bleomycin-induced pulmonary fibrosis.

Fibrotic diseases cause organ failure that lead to ~45% of all deaths in the United States. Activated macrophages stimulate fibrosis by secreting cytokines that induce fibroblasts to synthesize collagen and extracellular matrix proteins. Although suppression of macrophage-derived cytokine production can halt progression of fibrosis, therapeutic agents that prevent release of these cytokines (e.g., TLR7 agonists) have proven too toxic to administer systemically. Based on the expression of folate receptor ß solely on activated myeloid cells, we have created a folate-targeted TLR7 agonist (FA-TLR7-54) that selectively accumulates in profibrotic macrophages and suppresses fibrosis-inducing cytokine production. We demonstrate that FA-TLR7-54 reprograms M2-like fibrosis-inducing macrophages into fibrosis-suppressing macrophages, resulting in dramatic declines in profibrotic cytokine release, hydroxyproline biosynthesis, and collagen deposition, with concomitant increases in alveolar airspaces. Although nontargeted TLR7-54 is lethal at fibrosis-suppressing doses, FA-TLR7-54 halts fibrosis without evidence of toxicity. Taken together, FA-TLR7-54 is shown to constitute a novel and potent approach for treating fibrosis without causing dose-limiting systemic toxicities.

Depletion of activated macrophages with a folate receptor-beta-specific antibody improves symptoms in mouse models of rheumatoid arthritis.

OBJECTIVES: Most therapies for autoimmune and inflammatory diseases either neutralize or suppress production of inflammatory cytokines produced by activated macrophages (e.g., TNFα, IL-1, IL-6, IL-17, GM-CSF). However, no approved therapies directly target this activated subset of macrophages. METHODS: First, we undertook to examine whether the folate receptor beta (FR-ß) positive subpopulation of macrophages, which marks the inflammatory subset in animal models of rheumatoid arthritis, might constitute the prominent population of macrophages in inflamed lesions in humans. Next, we utilized anti-FR-ß monoclonal antibodies capable of mediating antibody-dependent cell cytotoxicity (ADCC) to treat animal models of rheumatoid arthritis and peritonitis. RESULTS: Human tissue samples of rheumatoid arthritis, Crohn's disease, ulcerative colitis, idiopathic pulmonary fibrosis, nonspecific interstitial pneumonia, chronic obstructive pulmonary disease, systemic lupus erythematosus, psoriasis, and scleroderma are all characterized by dramatic accumulation of macrophages that express FR-ß, a protein not expressed on resting macrophages or any other healthy tissues. A monoclonal antibody to FR-ß accumulates specifically in inflamed lesions of murine inflammatory disease models and successfully treats such models of rheumatoid arthritis and peritonitis. More importantly, elimination of FR-ß-positive macrophages upon treatment with an anti-FR-ß monoclonal antibody promotes the departure of other immune cells, including T cells, B cells, neutrophils, and dendritic cells from the inflamed lesions. CONCLUSIONS: These data suggest that specific elimination of FR-ß-expressing macrophages may constitute a highly specific therapy for multiple autoimmune and inflammatory diseases and that a recently developed human anti-human FR-ß monoclonal antibody (m909) might contribute to suppression of this subpopulation of macrophages.

Modeling the clinical phenotype of BTK inhibition in the mature murine immune system.

Inhibitors of Bruton's tyrosine kinase (BTK) possess much promise for the treatment of oncologic and autoimmune indications. However, our current knowledge of the role of BTK in immune competence has been gathered in the context of genetic inactivation of btk in both mice and man. Using the novel BTK inhibitor PF-303, we model the clinical phenotype of BTK inhibition by systematically examining the impact of PF-303 on the mature immune system in mice. We implicate BTK in tonic BCR signaling, demonstrate dependence of the T3 B cell subset and IgM surface expression on BTK activity, and find that B1 cells survive and function independently of BTK. Although BTK inhibition does not impact humoral memory survival, Ag-driven clonal expansion of memory B cells and Ab-secreting cell generation are inhibited. These data define the role of BTK in the mature immune system and mechanistically predict the clinical phenotype of chronic BTK inhibition.

Interleukin-21 receptor deficiency increases the initial toll-like receptor 2 response but protects against joint pathology by reducing Th1 and Th17 cells during streptococcal cell wall arthritis.

OBJECTIVE: The cytokine interleukin-21 (IL-21) can have both proinflammatory and immunosuppressive effects. The purpose of this study was to investigate the potential dual role of IL-21 in experimental arthritis in relation to Th17 cells. METHODS: Antigen-induced arthritis (AIA) and chronic streptococcal cell wall (SCW) arthritis were induced in IL-21 receptor-deficient (IL-21R(-/-) ) and wild-type mice. Knee joints, synovial tissue, and serum were analyzed for arthritis pathology and inflammatory markers. RESULTS: During AIA and chronic SCW arthritis, IL-21R deficiency protected against severe inflammation and joint destruction. This was accompanied by suppressed serum IgG1 levels and antigen-specific T cell responses. Levels of IL-17 were reduced during AIA, and synovial lymphocytes isolated during SCW arthritis for flow cytometry demonstrated that mainly IL-17+ interferon-γ (IFNγ)-positive T cells were reduced in IL-21R(-/-) mice. However, during the acute phases of SCW arthritis, significantly higher joint swelling scores were observed, consistent with enhanced tumor necrosis factor and IL-6 expression. Interestingly, IL-21R(-/-) mice were significantly less capable of up-regulating suppressor of cytokine signaling 1 (SOCS-1) and SOCS-3 messenger RNA. IL-21 stimulation also affected the Toll-like receptor 2 (TLR-2)/caspase recruitment domain 15 response to SCW fragments in vitro, indicating that impaired SOCS regulation in the absence of IL-21 signaling might contribute to the increased local activation during SCW arthritis. CONCLUSION: In contrast to the proinflammatory role of IL-21 in adaptive immunity, which drives IL-17+IFN+ cells and joint pathology during chronic experimental arthritis, IL-21 also has an important immunosuppressive role, presumably by inhibiting TLR signaling via SOCS-1 and SOCS-3. If this dual role of IL-21 in various immune processes is present in human disease, it could make IL-21 a difficult therapeutic target in rheumatoid arthritis.

Selective inhibition of BTK prevents murine lupus and antibody-mediated glomerulonephritis.

Autoantibody production and immune complex deposition within the kidney promote renal disease in patients with lupus nephritis. Thus, therapeutics that inhibit these pathways may be efficacious in the treatment of systemic lupus erythematosus. Bruton's tyrosine kinase (BTK) is a critical signaling component of both BCR and FcR signaling. We sought to assess the efficacy of inhibiting BTK in the development of lupus-like disease, and in this article describe (R)-5-amino-1-(1-cyanopiperidin-3-yl)-3-(4-[2,4-difluorophenoxy]phenyl)-1H-pyrazole-4-carboxamide (PF-06250112), a novel highly selective and potent BTK inhibitor. We demonstrate in vitro that PF-06250112 inhibits both BCR-mediated signaling and proliferation, as well as FcR-mediated activation. To assess the therapeutic impact of BTK inhibition, we treated aged NZBxW_F1 mice with PF-06250112 and demonstrate that PF-06250112 significantly limits the spontaneous accumulation of splenic germinal center B cells and plasma cells. Correspondingly, anti-dsDNA and autoantibody levels were reduced in a dose-dependent manner. Moreover, administration of PF-06250112 prevented the development of proteinuria and improved glomerular pathology scores in all treatment groups. Strikingly, this therapeutic effect could occur with only a modest reduction observed in anti-dsDNA titers, implying a critical role for BTK signaling in disease pathogenesis beyond inhibition of autoantibody production. We subsequently demonstrate that PF-06250112 prevents proteinuria in an FcR-dependent, Ab-mediated model of glomerulonephritis. Importantly, these results highlight that BTK inhibition potently limits the development of glomerulonephritis by impacting both cell- and effector molecule-mediated pathways. These data provide support for evaluating the efficacy of BTK inhibition in systemic lupus erythematosus patients.

In vivo imaging implicates CCR2(+) monocytes as regulators of neutrophil recruitment during arthritis.

The infiltration of neutrophils and monocytes is a prominent feature of inflammatory diseases including human rheumatoid arthritis. Understanding how neutrophil recruitment is regulated during pathogenesis is crucial for developing anti-inflammatory therapies. We optimized the K/B×N serum-induced mouse arthritis model to study neutrophil trafficking dynamics in vivo using two-photon microscopy. Arthritogenic serum was injected subcutaneously into one hind footpad to induce a local arthritis with robust neutrophil recruitment. Using this approach, we showed that the depletion of monocytes with clodronate liposomes impaired neutrophil recruitment specifically at the transendothelial migration step. The depletion of CCR2(+) monocytes with the monoclonal antibody MC-21 reproduced these effects, implicating CCR2(+) monocytes as key regulators of neutrophil extravasation during arthritis initiation. However, monocyte depletion did not prevent neutrophil extravasation in response to bacterial challenge. These findings suggest that anti-inflammatory therapies targeting monocytes may act in part through antagonizing neutrophil extravasation at sites of aseptic inflammation.

IL-21 receptor is required for the systemic accumulation of activated B and T lymphocytes in MRL/MpJ-Fas(lpr/lpr)/J mice.

MRL/MpJ-Fas(lpr/lpr)/J (MRL(lpr)) mice develop lupus-like disease manifestations in an IL-21-dependent manner. IL-21 is a pleiotropic cytokine that can influence the activation, differentiation, and expansion of B and T cell effector subsets. Notably, autoreactive CD4(+) T and B cells spontaneously accumulate in MRL(lpr) mice and mediate disease pathogenesis. We sought to identify the particular lymphocyte effector subsets regulated by IL-21 in the context of systemic autoimmunity and, thus, generated MRL(lpr) mice deficient in IL-21R (MRL(lpr).IL-21R(-/-)). Lymphadenopathy and splenomegaly, which are characteristic traits of the MRL(lpr) model were significantly reduced in the absence of IL-21R, suggesting that immune activation was likewise decreased. Indeed, spontaneous germinal center formation and plasma cell accumulation were absent in IL-21R-deficient MRL(lpr) mice. Correspondingly, we observed a significant reduction in autoantibody titers. Activated CD4(+) CD44(+) CD62L(lo) T cells also failed to accumulate, and CD4(+) Th cell differentiation was impaired, as evidenced by a significant reduction in CD4(+) T cells that produced the pronephritogenic cytokine IFN-γ. T extrafollicular helper cells are a recently described subset of activated CD4(+) T cells that function as the primary inducers of autoantibody production in MRL(lpr) mice. Importantly, we demonstrated that T extrafollicular helper cells are dependent on IL-21R for their generation. Together, our data highlighted the novel observation that IL-21 is a critical regulator of multiple pathogenic B and T cell effector subsets in MRL(lpr) mice.

Imidazo[1,5-a]quinoxalines as irreversible BTK inhibitors for the treatment of rheumatoid arthritis.

Imidazo[1,5-a]quinoxalines were synthesized that function as irreversible Bruton's tyrosine kinase (BTK) inhibitors. The syntheses and SAR of this series of compounds are presented as well as the X-ray crystal structure of the lead compound 36 in complex with a gate-keeper variant of ITK enzyme. The lead compound showed good in vivo efficacy in preclinical RA models.

Inter-regulation of Th17 cytokines and the IL-36 cytokines in vitro and in vivo: implications in psoriasis pathogenesis.

Accumulating evidence indicates that IL-1 family members and Th17 cytokines have a pathogenic role in psoriasis. We investigated the regulatory interactions of the IL-1-like IL-36 cytokine family and the Th17 cytokines in the context of skin inflammation. We observed increased gene expression of all three IL-36 cytokines in a Th17-dominant psoriasis-like animal model. The induction was downregulated by neutralizing IL-22. Expression of the IL-36s was also induced in cultured primary human keratinocytes (KC) by IL-17A and tumor necrosis factor (TNF)-α, and IL-22 synergized with IL-17A and TNF-α. Furthermore, the IL-36s directly induced their own expression and the production of proinflammatory mediators (TNF-α, IL-6, IL-8) in KC. These functions were markedly enhanced with the addition of IL-17A or TNF-α to the cultures. Similarly, IL-36α and IL-36ß augmented IL-17A-mediated induction of antibacterial peptides. Finally, we show that the increased gene expression of IL-36 correlated with Th17 cytokines in the lesions of psoriatic patients. Our results indicate that the IL-36 cytokines are not only regulated by Th17 cytokines, but that they themselves can regulate the expression and enhance the function of Th17 cytokines. We propose that a feedback loop between the IL-36 and Th17 cytokines is involved in driving cytokine expression in psoriatic tissues.

Increased expression of interleukin-22 by synovial Th17 cells during late stages of murine experimental arthritis is controlled by interleukin-1 and enhances bone degradation.

OBJECTIVE: Interleukin-22 (IL-22) is a mediator in antimicrobial responses and inflammatory autoimmune diseases. Although IL-22 and its receptor, IL-22R, have been identified in the synovium of rheumatoid arthritis patients, the source of IL-22 and its contribution to disease pathogenicity remain to be established. This study was undertaken to investigate the regulation of IL-22 by Th17 cells in vitro and to evaluate the potential for IL-22 depletion in an experimental arthritis model using mice deficient in the IL-1 receptor antagonist (IL-1Ra-/-). METHODS: Naive murine T cells were cultured under conditions leading to polarization of the cells into subsets of Th1, Th2, induced Treg, and Th17. Cytokines were measured in the culture supernatants, and the cells were analyzed by fluorescence-activated cell sorting. Tissue samples from the inflamed ankle synovium of IL-1Ra-/- mice were isolated, and messenger RNA levels of marker genes were quantified. IL-1Ra-/- mice were treated with neutralizing anti-IL-22 antibodies. Synovial cells were isolated from the inflamed tissue and sorted into fractions for analysis of cytokine production. RESULTS: In vitro tests showed that Th17 cells produced high levels of IL-22 after stimulation with IL-1 or IL-23. Interestingly, a synergistic increase in the production of IL-22 was observed after combining IL-1 and IL-23. In vivo, IL-1Ra-/- mice displayed a progressive erosive arthritis, characterized by up-regulation of IL-17 in mildly and severely inflamed tissue, whereas the levels of IL-22 and IL-22R were increased only in severely inflamed synovia. Anti-IL-22 treatment of IL-1Ra-/- mice significantly reduced the inflammation and bone erosion. Analysis of isolated single cells from the inflamed synovia revealed that IL-22 was mainly produced by IL-17-expressing T cells. CONCLUSION: These findings suggest that IL-22 plays an important role in IL-1-driven chronic joint destruction.

Distinct in vitro binding properties of the anti-CD20 small modular immunopharmaceutical 2LM20-4 result in profound and sustained in vivo potency in cynomolgus monkeys.

OBJECTIVES: To characterize the in vitro binding and effector function properties of CD20-directed small modular immunopharmaceutical (SMIP) 2LM20-4, and to compare its in vivo B-cell depletion activity with the mutated 2LM20-4 P331S [no in vitro complement-dependent cytotoxicity (CDC)] and rituximab in cynomolgus monkeys. METHODS: Direct binding is examined in flow cytometry, confocal microscopy, scatchard and lipid raft assays. Effector function assays include CDC and Fc-mediated cellular toxicity. In the 6-month-long in vivo B-cell depletion study, single i.v. dosages of 1 or 10 mg/kg of anti-CD20 proteins were administered to monkeys and B-cell counts were monitored in peripheral blood, bone marrow and lymph nodes. RESULTS: 2LM20-4 has lower saturation binding to human primary B cells and recruits fewer CD20 molecules into lipid rafts compared with rituximab; however, it induces higher in vitro CDC. In competitive binding, 2LM20-4 only partially displaces rituximab, suggesting that it binds to a fraction of CD20 molecules within certain locations of the plasma membrane as compared with rituximab. In monkeys, 2LM20-4 had more sustained B-cell depletion activity than rituximab in peripheral blood and had significantly more profound and sustained activity than 2LM20-4 P331S and rituximab in the lymph nodes. CONCLUSIONS: SMIP 2LM20-4, which binds to a fraction of CD20 molecules as compared with rituximab, has more potent in vitro CDC, and more potent and sustained B-cell depletion activity in cynomolgus monkeys. Our work has considerable clinical relevance since it provides novel insights related to the emerging B-cell depletion therapies in autoimmune diseases.

IL-21 receptor is critical for the development of memory B cell responses.

Development of long-term humoral immunity, characterized by the formation of long-lived plasma cells (PCs) in the bone marrow and memory B cells, is a critical component of protective immunity to pathogens, and as such it is the major goal of vaccination. However, the mechanisms involved in the generation of long-term humoral immunity remain poorly understood. In this study, we used IL-21R-deficient (IL-21R.KO) mice to examine the role of the IL-21 pathway in the development of the B cell memory response. Primary IgG serum Ab responses to the T cell-dependent Ag 4-hydroxy-3-nitrophenylacetyl (NP) hapten conjugated to chicken γ globulin were delayed in IL-21R.KO mice, but reached normal titers within 3 to 4 wk of immunization. IL-21R.KO mice formed germinal centers and generated normal numbers of PCs in their bone marrow. Additionally, memory B cell formation was similar in wild-type and IL-21R.KO mice. However, NP-specific memory B cells and PCs failed to expand following secondary immunization of IL-21R.KO mice, and consequently, secondary IgG Ab responses to NP hapten conjugated to chicken γ globulin were significantly impaired. These results identify the IL-21 pathway as a critical component of the memory B cell response.

The cPLA2α inhibitor efipladib decreases nociceptive responses without affecting PGE2 levels in the cerebral spinal fluid.

The contribution of central PGE(2) levels to the nociceptive response in rats was assessed and the effects of the selective cPLA(2)α inhibitor efipladib, and pain therapies of different classes on these responses was determined. An inflammatory pain model was optimized in rats so that PGE(2) levels in the cerebrospinal fluid (CSF) could be directly correlated to the nociceptive response. Since efipladib appears to have limited permeation of the blood-brain barrier, we used this compound to determine the extent of pain reversal resulting primarily from peripheral, but not central, inhibition of the arachidonic acid (AA) pathway. The nociceptive response was significantly inhibited by orally administered efipladib, yet spinal fluid levels of PGE(2) and temperature measurements were unaffected compared to vehicle-treated animals. Conversely, intrathecal (IT) administration of efipladib reduced PGE(2) levels in the CSF by 45-60%, yet there was no effect on the nociceptive response. With COX-2 selective inhibitors and ibuprofen, a return of the nociceptive response developed over time, despite complete inhibition of PGE(2) in the spinal fluid. The opposite was true with low doses of indomethacin: inhibition of the nociceptive response was observed despite the lack of effect on central PGE(2) levels. Our results demonstrate that levels of PGE(2) in the spinal fluid do not directly correlate with the nociceptive response and that blocking cPLA(2)α in the periphery significantly decreases inflammatory pain.

IL-22 induces an acute-phase response.

IL-22 is made by a unique set of innate and adaptive immune cells, including the recently identified noncytolytic NK, lymphoid tissue-inducer, Th17, and Th22 cells. The direct effects of IL-22 are restricted to nonhematopoietic cells, its receptor expressed on the surface of only epithelial cells and some fibroblasts in various organs, including parenchymal tissue of the gut, lung, skin, and liver. Despite this cellular restriction on IL-22 activity, we demonstrate that IL-22 induces effects on systemic biochemical, cellular, and physiological parameters. By utilizing adenoviral-mediated delivery of IL-22 and systemic administration of IL-22 protein, we observed that IL-22 modulates factors involved in coagulation, including fibrinogen levels and platelet numbers, and cellular constituents of blood, such as neutrophil and RBC counts. Furthermore, we observed that IL-22 induces thymic atrophy, body weight loss, and renal proximal tubule metabolic activity. These cellular and physiological parameters are indicative of a systemic inflammatory state. We observed that IL-22 induces biochemical changes in the liver including induction of fibrinogen, CXCL1, and serum amyloid A that likely contribute to the reported cellular and physiological effects of IL-22. Based on these findings, we propose that downstream of its expression and impact in local tissue inflammation, circulating IL-22 can further induce changes in systemic physiology that is indicative of an acute-phase response.

The DTH effector response and IL-2 are unaffected by cyclosporine A in autoimmune B6D2F1 mice.

Delayed-type hypersensitivity (DTH) is classically defined as inflammation involving activated Th1 cells and cytokine production. DTH paw swelling, along with the cytokines IL-2, IFNγ, MCP-1 and TNFα, were inhibited in Balb/c mice by cyclosporine A (CsA). Surprisingly, the DTH response in the B6D2F1 mice was unaffected by CsA, despite a decrease in TNFα and IFNγ levels. IL-2 levels, however, were not decreased. To determine if the IL-2 production in the B6D2F1 strain is occurring through CD28-mediated costimulation, both CsA and CTLA-4Ig were administered. Paw swelling and IL-2 levels were decreased, indicating a role for costimulation. Co-administration of temsirolimus and CsA also reduced DTH and IL-2 levels in B6D2F1 mice, demonstrating involvement of the mTORC1 pathway. These results indicate that the cell activation pathways responsible for DTH differ with mouse strain. It is important to understand these differences in order to accurately interpret the results using potential therapeutic agents.

Selective functional inhibition of JAK-3 is sufficient for efficacy in collagen-induced arthritis in mice.

OBJECTIVE: All gamma-chain cytokines signal through JAK-3 and JAK-1 acting in tandem. We undertook this study to determine whether the JAK-3 selective inhibitor WYE-151650 would be sufficient to disrupt cytokine signaling and to ameliorate autoimmune disease pathology without inhibiting other pathways mediated by JAK-1, JAK-2, and Tyk-2. METHODS: JAK-3 kinase selective compounds were characterized by kinase assay and JAK-3-dependent (interleukin-2 [IL-2]) and -independent (IL-6, granulocyte-macrophage colony-stimulating factor [GM-CSF]) cell-based assays measuring proliferation or STAT phosphorylation. In vivo, off-target signaling was measured by IL-22- and erythropoietin (EPO)-mediated models, while on-target signaling was measured by IL-2-mediated signaling. Efficacy of JAK-3 inhibitors was determined using delayed-type hypersensitivity (DTH) and collagen-induced arthritis (CIA) models in mice. RESULTS: In vitro, WYE-151650 potently suppressed IL-2-induced STAT-5 phosphorylation and cell proliferation, while exhibiting 10-29-fold less activity against JAK-3-independent IL-6- or GM-CSF-induced STAT phosphorylation. Ex vivo, WYE-151650 suppressed IL-2-induced STAT phosphorylation, but not IL-6-induced STAT phosphorylation, as measured in whole blood. In vivo, WYE-151650 inhibited JAK-3-mediated IL-2-induced interferon-gamma production and decreased the natural killer cell population in mice, while not affecting IL-22-induced serum amyloid A production or EPO-induced reticulocytosis. WYE-151650 was efficacious in mouse DTH and CIA models. CONCLUSION: In vitro, ex vivo, and in vivo assays demonstrate that WYE-151650 is efficacious in mouse CIA despite JAK-3 selectivity. These data question the need to broadly inhibit JAK-1-, JAK-2-, or Tyk-2-dependent cytokine pathways for efficacy.

Tumor necrosis factor alpha blockade exacerbates murine psoriasis-like disease by enhancing Th17 function and decreasing expansion of Treg cells.

OBJECTIVE: Patients with psoriasis and psoriatic arthritis respond well to tumor necrosis factor alpha (TNFalpha) blockers in general; however, there is now mounting evidence that a small cohort of patients with rheumatoid arthritis who receive TNFalpha blockers develop psoriasis. This study was undertaken to explore the mechanisms underlying TNFalpha blockade-induced exacerbation of skin inflammation in murine psoriasis-like skin disease. METHODS: Skin inflammation was induced in BALB/c scid/scid mice after they received CD4+CD45RB(high)CD25- (naive CD4) T cells from donor mice. These mice were treated with either anti-interleukin-12 (anti-IL-12)/23p40 antibody or murine TNFRII-Fc fusion protein and were examined for signs of disease, including histologic features, various cytokine levels in the serum, and cytokine or FoxP3 transcripts in the affected skin and draining lymph node (LN) cells. In a separate study, naive CD4+ T cells were differentiated into Th1 or Th17 lineages with anti-CD3/28 magnetic beads and appropriate cytokines in the presence or absence of TNFalpha. Cytokine gene expression from these differentiated cells was also determined. RESULTS: Neutralization of TNFalpha exacerbated skin inflammation and markedly enhanced the expression of the proinflammatory cytokines IL-1beta, IL-6, IL-17, IL-21, and IL-22 but suppressed FoxP3 expression in the skin and reduced the number of FoxP3-positive Treg cells in the draining LNs. TNFalpha also demonstrated a divergent role during priming and reactivation of naive T cells. CONCLUSION: These results reveal a novel immunoregulatory role of TNFalpha on Th17 and Treg cells in some individuals, which may account for the exacerbation of skin inflammation in some patients who receive anti-TNF treatments.