Peter Gribling

Importance of Cellular Microenvironment and Circulatory Dynamics in B Cell Immunotherapy

B cell immunotherapy has emerged as a mainstay in the treatment of lymphomas and autoimmune diseases. Although the microenvironment has recently been demonstrated to play critical roles in B cell homeostasis, its contribution to immunotherapy is unknown. To analyze the in vivo factors that regulate mechanisms involved in B cell immunotherapy, we used a murine model for human CD20 (hCD20) expression in which treatment of hCD20+ mice with anti-hCD20 mAbs mimics B cell depletion observed in humans. We demonstrate in this study that factors derived from the microenvironment, including signals from the B cell-activating factor belonging to the TNF family/BLyS survival factor, integrin-regulated homeostasis, and circulatory dynamics of B cells define distinct in vivo mechanism(s) and sensitivities of cells in anti-hCD20 mAb-directed therapies. These findings provide new insights into the mechanisms of immunotherapy and define new opportunities in the treatment of cancers and autoimmune diseases.

Specific Btk inhibition suppresses B cell– and myeloid cell–mediated arthritis

Brutons tyrosine kinase (Btk) is a therapeutic target for rheumatoid arthritis, but the cellular and molecular mechanisms by which Btk mediates inflammation are poorly understood. Here we describe the discovery of CGI1746, a small-molecule Btk inhibitor chemotype with a new binding mode that stabilizes an inactive nonphosphorylated enzyme conformation. CGI1746 has exquisite selectivity for Btk and inhibits both auto- and transphosphorylation steps necessary for enzyme activation. Using CGI1746, we demonstrate that Btk regulates inflammatory arthritis by two distinct mechanisms. CGI1746 blocks B cell receptor-dependent B cell proliferation and in prophylactic regimens reduces autoantibody levels in collagen-induced arthritis. In macrophages, Btk inhibition abolishes FcγRIII-induced TNFα, IL-1β and IL-6 production. Accordingly, in myeloid- and FcγR-dependent autoantibody-induced arthritis, CGI1746 decreases cytokine levels within joints and ameliorates disease. These results provide new understanding of the function of Btk in both B cell- or myeloid cell-driven disease processes and provide a compelling rationale for targeting Btk in rheumatoid arthritis.

Targeted depletion of lymphotoxin-alpha-expressing TH1 and TH17 cells inhibits autoimmune disease.

Uncontrolled T helper type 1 (TH1) and TH17 cells are associated with autoimmune responses. We identify surface lymphotoxin-α (LT-α) as common to TH0, TH1 and TH17 cells and employ a unique strategy to target these subsets using a depleting monoclonal antibody (mAb) directed to surface LT-α. Depleting LT-α–specific mAb inhibited T cell–mediated models of delayed-type hypersensitivity and experimental autoimmune encephalomyelitis. In collagen-induced arthritis (CIA), preventive and therapeutic administration of LT-α–specific mAb inhibited disease, and immunoablated T cells expressing interleukin-17 (IL-17), interferon-γ and tumor necrosis factor-α (TNF-α), whereas decoy lymphotoxin-β receptor (LT-βR) fusion protein had no effect. A mutation in the Fc tail, rendering the antibody incapable of Fcγ receptor binding and antibody-dependent cellular cytotoxicity activity, abolished all in vivo effects. Efficacy in CIA was preceded by a loss of rheumatoid-associated cytokines IL-6, IL-1β and TNF-α within joints. These data indicate that depleting LT-α–expressing lymphocytes with LT-α–specific mAb may be beneficial in the treatment of autoimmune disease.

A novel inhibitor of the alternative pathway of complement reverses inflammation and bone destruction in experimental arthritis

Complement is an important component of the innate and adaptive immune response, yet complement split products generated through activation of each of the three complement pathways (classical, alternative, and lectin) can cause inflammation and tissue destruction. Previous studies have shown that complement activation through the alternative, but not classical, pathway is required to initiate antibody-induced arthritis in mice, but it is unclear if the alternative pathway (AP) plays a role in established disease. Previously, we have shown that human complement receptor of the immunoglobulin superfamily (CRIg) is a selective inhibitor of the AP of complement. Here, we present the crystal structure of murine CRIg and, using mutants, provide evidence that the structural requirements for inhibition of the AP are conserved in human and mouse. A soluble form of CRIg reversed inflammation and bone loss in two experimental models of arthritis by inhibiting the AP of complement in the joint. Our data indicate that the AP of complement is not only required for disease induction, but also disease progression. The extracellular domain of CRIg thus provides a novel tool to study the effects of inhibiting the AP of complement in established disease and constitutes a promising therapeutic with selectivity for a single complement pathway.

Selective modulation of the expression of L-selectin ligands by an immune response

BACKGROUND The adhesion molecule L-selectin is expressed on the cell surface of lymphocytes and mediates their migration from the bloodstream into lymph nodes. L-selectin is able to recognize four glycoprotein ligands, three of which--Sgp50, Sgp90, and Sgp200--are sulphated, bind specifically to L-selectin and are synthesized by the high endothelial venules of the peripheral and mesenteric lymph nodes. One of these three sulphated L-selectin ligands, Sgp90, has been shown to be identical to the known surface marker CD34 and is expressed on the cell surface of endothelial cells. The cDNA encoding Sgp50 has been cloned, and its product, which has been designated GlyCAM-1, is secreted. The third ligand, Sgp200, is both secreted and cell-associated. We have investigated how the expression of these sulphated glycoproteins is regulated during an immune response. RESULTS Here we demonstrated that, during a primary immune response, the expression and secretion of both GlyCAM-1 and Sgp200 are reduced, recovering to normal levels 7-10 days after antigen stimulation. In contrast, the expression of cell-associated CD34 and Sgp200 is relatively unaffected. These results may account for the modest decreases in the binding of an L-selectin-IgG fusion protein to high endothelial venules of inflamed peripheral lymph nodes that have been observed after antigen exposure. In vivo experiments show that, following the decrease in the levels of secreted GlyCAM-1 and Sgp200, migration of lymphocytes from the blood stream into lymph nodes remains L-selectin-dependent, but more lymphocytes home to antigen-primed than unprimed peripheral lymph nodes. CONCLUSIONS We suggest that the secreted forms of the L-selectin ligands GlyCAM-1 and Sgp200 act as modulators of cell adhesion, and that cell-associated CD34 and Sgp200 are the ligands that mediate the initial loose binding of lymphocytes to high endothelial venules.

Identification of C-2 Hydroxyethyl Imidazopyrrolopyridines as Potent JAK1 Inhibitors with Favorable Physicochemical Properties and High Selectivity over JAK2.

Herein we report on the structure-based discovery of a C-2 hydroxyethyl moiety which provided consistently high levels of selectivity for JAK1 over JAK2 to the imidazopyrrolopyridine series of JAK1 inhibitors. X-ray structures of a C-2 hydroxyethyl analogue in complex with both JAK1 and JAK2 revealed differential ligand/protein interactions between the two isoforms and offered an explanation for the observed selectivity. Analysis of historical data from related molecules was used to develop a set of physicochemical compound design parameters to impart desirable properties such as acceptable membrane permeability, potent whole blood activity, and a high degree of metabolic stability. This work culminated in the identification of a highly JAK1 selective compound (31) exhibiting favorable oral bioavailability across a range of preclinical species and robust efficacy in a rat CIA model.

Development and Preclinical Characterization of a Humanized Antibody Targeting CXCL12

Purpose: Our goal was to develop a potent humanized antibody against mouse/human CXCL12. This report summarized its in vitro and in vivo activities. Experimental Design: Cell surface binding and cell migration assays were used to select neutralizing hamster antibodies, followed by testing in several animal models. Monoclonal antibody (mAb) 30D8 was selected for humanization based on its in vitro and in vivo activities. Results: 30D8, a hamster antibody against mouse and human CXCL12α, CXCL12β, and CXCL12γ, was shown to dose-dependently block CXCL12α binding to CXCR4 and CXCR7, and CXCL12α-induced Jurkat cell migration in vitro. Inhibition of primary tumor growth and/or metastasis was observed in several models. 30D8 alone significantly ameliorated arthritis in a mouse collagen-induced arthritis model (CIA). Combination with a TNF-α antagonist was additive. In addition, 30D8 inhibited 50% of laser-induced choroidal neovascularization (CNV) in mice. Humanized 30D8 (hu30D8) showed similar in vitro and in vivo activities as the parental hamster antibody. A crystal structure of the hu30D8 Fab/CXCL12α complex in combination with mutational analysis revealed a “hot spot” around residues Asn44/Asn45 of CXCL12α and part of the RFFESH region required for CXCL12α binding to CXCR4 and CXCR7. Finally, hu30D8 exhibited fast clearance in cynomolgus monkeys but not in rats. Conclusion: CXCL12 is an attractive target for treatment of cancer and inflammation-related diseases; hu30D8 is suitable for testing this hypothesis in humans. Clin Cancer Res; 19(16); 4433–45. ©2013 AACR.

Reduced mortality in murine cytomegalovirus infected mice following prophylactic murine interferon-γ treatment

Efficacy of recombinant DNA-derived murine IFN-gamma was investigated in a murine model of cytomegalovirus infection. Treatment of 3-week-old Swiss Webster mice with murine IFN-gamma prior to infection with murine cytomegalovirus (MCMV) significantly reduced mortality due to MCMV infection. Efficacy was dose-dependent and was observed using either intraperitoneal or intramuscular injection as the route of administration. Two doses, one at 24 h and one at 4 h prior to MCMV infection, were required for optimum efficacy, and doses administered after MCMV infection had no apparent effect. Reduced infectious MCMV titers were observed in critical organs of IFN-gamma treated mice and histopathologic lesions induced by MCMV infection were in general less severe and resolved sooner than lesions in untreated mice. Results in this murine model of cytomegalovirus infection suggest that IFN-gamma treatment may be useful as prophylactic therapy for human cytomegalovirus infections when a high probability of exposure to the virus exists and consequences of infection may be severe.

CRIg mediates early Kupffer cell responses to adenovirus

Whereas adenoviral vectors are known to activate the complement cascade, leading to fixation of C3 proteins to the viral capsid, the consequences of this activation for viral clearance from the circulation are not known. Liver KCs, the macrophage population responsible for early uptake and elimination of many blood‐borne pathogens, express CRIg, a complement receptor for C3 proteins. Here, we find that CRIg is important for the early elimination of C3‐coated adenoviral vectors from the sinusoidal bloodstream by KCs. We further demonstrate that by acting as a critical receptor for adenovirus phagocytosis, CRIg plays an important role in regulating virus‐induced KC death and depletion of these cells from the liver sinusoidal lumen. Our study thus identifies a critical pathway regulating KC function and survival in response to systemic viral infection.

A P-selectin-immunoglobulin G chimera is protective in a rabbit ear model of ischemia-reperfusion

BACKGROUND Neutrophils have been shown to play a role in ischemia-reperfusion injury, and the initial interaction of neutrophils with the endothelium is mediated through the selectin family of adhesion molecules. Thus the purpose of these studies was to determine whether a P-selectin-IgG chimera was protective in a model of ischemia-reperfusion injury. METHODS The model used was a rabbit ear model of ischemia-reperfusion. Selectin-IgG chimeras were given at the time of reperfusion of the tissue, and their efficacy was compared with an anti-CD18 antibody (MHM23). RESULTS The P-selectin-IgG was as protective in this model as an anti-CD18 antibody. The chimera did not mediate its effect by causing the animals to become neutropenic. CONCLUSIONS P-selectin plays a role in ischemia-reperfusion injury. This is in agreement with data from other groups. The fact that the chimera was effective in this model suggests that carbohydrates or small molecule mimics of carbohydrates would be effective in this model. Such antiinflammatory agents may have fewer side effects in terms of increased risk of sepsis.