A novel monoclonal antibody against 6-sulfo sialyl Lewis x glycans attenuates murine allergic rhinitis by suppressing Th2 immune responses.

Lymphocyte homing is mediated by the interaction between L-selectin on lymphocytes and its glycoprotein ligands modified with 6-sulfo sialyl Lewis x (6-sulfo sLex) glycans on high endothelial venules (HEVs) in peripheral lymph nodes (PLNs). However, the lack of specific antibodies reactive with both human and mouse 6-sulfo sLex has limited our understanding of its function in vivo. Here, we generated a novel monoclonal antibody, termed SF1, that specifically reacts with 6-sulfo sLex expressed on HEVs in both species in a manner dependent on sulfate, fucose, and sialic acid modifications. Glycan array and biolayer interferometry analyses indicated that SF1 specifically bound to 6-sulfo sLex with a dissociation constant of 6.09 × 10-9 M. SF1 specifically bound to four glycoproteins from PLNs corresponding to the molecular sizes of L-selectin ligand glycoproteins. Consistently, SF1 inhibited L-selectin-dependent lymphocyte rolling on 6-sulfo sLex-expressing cells ex vivo and lymphocyte homing to PLNs and nasal-associated lymphoid tissues in vivo. Furthermore, SF1 significantly attenuated ovalbumin-induced allergic rhinitis in mice in association with significant suppression of Th2 immune responses. Collectively, these results suggest that SF1 can be useful for the functional analysis of 6-sulfo sLex and may potentially serve as a novel therapeutic agent against immune-related diseases.

Tumor-associated neutrophils and macrophages exacerbate antidrug IgG-mediated anaphylactic reaction against an immune checkpoint inhibitor.

BACKGROUND: With the increased use of immune checkpoint inhibitors (ICIs), side effects and toxicity are a great concern. Anaphylaxis has been identified as a potential adverse event induced by ICIs. Anaphylaxis is a life-threatening medical emergency. However, the mechanisms and factors that can potentially influence the incidence and severity of anaphylaxis in patients with cancer remain unclear. METHODS: Healthy, murine colon 26, CT26, breast 4T1, EMT6, and renal RENCA tumor-bearing mice were treated with an anti-PD-L1 antibody (clone 10F.9G2). Symptoms of anaphylaxis were evaluated along with body temperature and mortality. The amounts of antidrug antibody and platelet-activating factor (PAF) in the blood were quantified via ELISA and liquid chromatography-mass spectrometry (LC-MS/MS). Immune cells were analyzed and isolated using a flow cytometer and magnetic-activated cell sorting, respectively. RESULTS: Repeated administration of the anti-PD-L1 antibody 10F.9G2 to tumor-bearing mice caused fatal anaphylaxis, depending on the type of tumor model. After administration, antidrug immunoglobulin G (IgG), but not IgE antibodies, were produced, and PAF was released as a chemical mediator during anaphylaxis, indicating that anaphylaxis was caused by an IgG-dependent pathway. Anaphylaxis induced by 10F.9G2 was treated with a PAF receptor antagonist. We identified that neutrophils and macrophages were PAF-producing effector cells during anaphylaxis, and the tumor-bearing models with increased numbers of neutrophils and macrophages showed lethal anaphylaxis after treatment with 10F.9G2. Depletion of both neutrophils and macrophages using clodronate liposomes prevented anaphylaxis in tumor-bearing mice. CONCLUSIONS: Thus, increased numbers of neutrophils and macrophages associated with cancer progression may be risk factors for anaphylaxis. These findings may provide useful insights into the mechanism of anaphylaxis following the administration of immune checkpoint inhibitors in human subjects.

Therapeutic Effects of an Anti-sialyl Lewis X Antibody in a Murine Model of Allergic Asthma.

Asthma is an allergic disease that causes severe infiltration of leukocytes into the lungs. Leukocyte infiltration is mediated by the binding of sialyl Lewis X (sLex) glycans present on the leukocytes to E-and P-selectins present on the endothelial cells at the sites of inflammation. Here, we found that mouse eosinophils express sLex glycans, and their infiltration into the lungs and proliferation in the bone marrow were significantly suppressed by an anti-sLex monoclonal antibody (mAb) F2 in a murine model of ovalbumin-induced asthma. The percentage of eosinophils in the bronchoalveolar lavage fluid and bone marrow and serum IgE levels decreased significantly in the F2-administered mice. Levels of T helper type 2 (Th2) cytokines and chemokines, involved in IgE class switching and eosinophil proliferation and recruitment, were also decreased in the F2-administered mice. An ex vivo cell rolling assay revealed that sLex glycans mediate the rolling of mouse eosinophils on P-selectin-expressing cells. These results indicate that the mAb F2 exerts therapeutic effects in a murine model of allergen-induced asthma, suggesting that sLex carbohydrate antigen could serve as a novel therapeutic target for allergic asthma.

Forced Expression of CXCL10 Prevents Liver Metastasis of Colon Carcinoma Cells by the Recruitment of Natural Killer Cells.

CXC chemokine ligand 10 (CXCL10) is a CXC chemokine family protein that transmits signals by binding to its specific receptor, CXCR3. CXCL10 is also known as an interferon-γ-inducible chemokine involved in various biological phenomena, including chemotaxis of natural killer (NK) cells and cytotoxic T lymphocytes, that suppress tumor growth and inhibition of angiogenesis. In this study, we examined the effects of forced expression of CXCL10 in a murine colon carcinoma cell line (CT26) on growth and metastasis in syngeneic mice. We first established CT26 cells that were stably expressing murine CXCL10 (CT26/CXCL10) and compared their growth with their parental CT26 cells in vitro and in vivo. The in vitro growth of the CT26/CXCL10 and CT26 cells was comparable, whereas the in vivo growth of the CT26/CXCL10 cells in the skin was strongly suppressed. Liver metastasis of the CT26/CXCL10 cells was also significantly suppressed after intra-splenic implantation. Removal of NK cells by the administration of anti-asialo GM1 antibody canceled the suppression of subcutaneous growth and liver metastasis of CT26/CXCL10 cells. Immunofluorescence clearly showed that abundant NKp46-positive NK cells were recruited into the liver metastatic lesions of the CT26/CXCL10 cells, consistent with specific NK cell migration towards the culture supernatant from the CT26/CXCL10 cells in the chemotaxis assay using transwells. These findings indicate that CXCL10 prevents in vivo growth and metastasis of colon carcinoma cells by recruiting NK cells, suggesting that forced expression of CXCL10 in the colon tumors by gene delivery should lead to a favorable clinical outcome.

Role of MAdCAM-1-Expressing High Endothelial Venule-Like Vessels in Colitis Induced in Mice Lacking Sulfotransferases Catalyzing L-Selectin Ligand Biosynthesis.

Ulcerative colitis (UC) is a chronic inflammatory disease histologically characterized by diffuse mononuclear cell infiltrates in colonic mucosa. These inflammatory cells are considered to be recruited via high endothelial venule (HEV)-like vessels displaying mucosal addressin cell adhesion molecule 1 (MAdCAM-1), the ligand for α4ß7 integrin, and/or peripheral lymph node addressin (PNAd), an L-selectin ligand. 6- O-sulfation of N-acetylglucosamine in the carbohydrate moiety of PNAd is catalyzed exclusively by N-acetylglucosamine-6- O-sulfotransferase 1 (GlcNAc6ST-1) and GlcNAc6ST-2. To determine the role of 6- O-sulfation of N-acetylglucosamine on HEV-like vessels in UC, we used a chronic dextran sulfate sodium-induced colitis model using mice deficient in both GlcNAc6ST-1 and GlcNAc6ST-2. We found that more inflammatory cells, with expression of tumor necrosis factor α, were infiltrated in double knockout mouse colitis compared with that in wild-type mice. Moreover, the number of MAdCAM-1-positive vessels was increased in double knockout mouse colitis, and these vessels were bound by E-selectin•IgM chimeras that bind to unsulfated sialyl Lewis X (sLeX). These findings suggest that interactions between MAdCAM-1 and α4ß7 integrin and/or unsulfated sLeX and L-selectin may become a dominant mechanism for inflammatory cell recruitment in the absence of 6-sulfo sLeX and contribute to more severe colitis phenotypes seen in double knockout mice.

Rapid immunosurveillance by recirculating lymphocytes in the rat intestine: critical role of unsulfated sialyl-Lewis X on high endothelial venules of the Peyer's patches.

Naive lymphocytes systemically recirculate for immunosurveillance inspecting foreign antigens and pathogens in the body. Trafficking behavior such as the migration pathway and transit time within the gastrointestinal tract, however, remains to be elucidated. Rat thoracic duct lymphocytes (TDLs) were transferred to a congeneic host that had undergone mesenteric lymphadenectomy. The migration pathway was investigated using newly developed four-color immunohistochemistry and immunofluorescence. Donor TDLs showed rapid transition in gut tissues from which they emerged in mesenteric lymph around 4 h after intravenous injection. Immunohistochemistry showed that donor TDLs predominantly transmigrated across high endothelial venules (HEVs) at the interfollicular area of the Peyer's patches (PPs), then exited into the LYVE-1+ efferent lymphatics, that were close to the venules. The rapid recirculation depended largely on the local expression of unsulfated sialyl-Lewis X on these venules where putative dendritic cells (DCs) were associated underneath. Recruited naive T cells briefly made contact with resident DCs before exiting to the lymphatics in the steady state. In some transplant settings, however, the T cells retained contact with DCs and were sensitized and differentiated into activated T cells. In conclusion, we directly demonstrated that lymphocyte recirculation within the gut is a very rapid process. The interfollicular area of PPs functions as a strategically central site for rapid immunosurveillance where HEVs, efferent lymphatics and resident DCs converge. PPs can, however, generate alloreactive T cells, leading to exacerbation of graft-versus-host disease or gut allograft rejection.

Novel Antibodies Reactive with Sialyl Lewis X in Both Humans and Mice Define Its Critical Role in Leukocyte Trafficking and Contact Hypersensitivity Responses.

Sialyl Lewis X (sLe(x)) antigen functions as a common carbohydrate determinant recognized by all three members of the selectin family. However, its expression and function in mice remain undefined due to the poor reactivity of conventional anti-sLe(x) monoclonal antibodies (mAbs) with mouse tissues. Here, we developed novel anti-sLe(x) mAbs, termed F1 and F2, which react well with both human and mouse sLe(x), by immunizing fucosyltransferase (FucT)-IV and FucT-VII doubly deficient mice with 6-sulfo-sLe(x)-expressing cells transiently transfected with an expression vector encoding CMP-N-acetylneuraminic acid hydroxylase. F1 and F2 specifically bound both the N-acetyl and the N-glycolyl forms of sLe(x) as well as 6-sulfo-sLe(x), a major ligand for L-selectin expressed in high endothelial venules, and efficiently blocked physiological lymphocyte homing to lymph nodes in mice. Importantly, both of the mAbs inhibited contact hypersensitivity responses not only when administered in the L-selectin-dependent sensitization phase but also when administered in the elicitation phase in mice. When administered in the latter phase, F1 and F2 efficiently blocked rolling of mouse leukocytes along blood vessels expressing P- and E-selectin in the auricular skin in vivo. Consistent with these findings, the mAbs blocked P- and E-selectin-dependent leukocyte rolling in a flow chamber assay. Taken together, these results indicate that novel anti-sLe(x) mAbs reactive with both human and mouse tissues, with the blocking ability against leukocyte trafficking mediated by all three selectins, have been established. These mAbs should be useful in determining the role of sLe(x) antigen under physiological and pathological conditions.

Role of high endothelial venule-expressed heparan sulfate in chemokine presentation and lymphocyte homing.

Lymphocyte homing to peripheral lymph nodes (PLNs) is mediated by multistep interactions between lymphocytes and high endothelial venules (HEVs). Heparan sulfate (HS) has been implicated in the presentation of chemokines on the surface of HEVs during this process. However, it remains unclear whether this cell surface presentation is a prerequisite for lymphocyte homing. In this study, we generated conditional knockout (cKO) mice lacking Ext1, which encodes a glycosyltransferase essential for HS synthesis, by crossing Ext1(flox/flox) mice with GlcNAc6ST-2-Cre transgenic mice expressing Cre recombinase in HEVs. Immunohistochemical studies indicated that HS expression was specifically eliminated in PLN HEVs but retained in other blood vessels in the cKO mice. The accumulation of a major secondary lymphoid tissue chemokine, CCL21, on HEVs was also abrogated without affecting CCL21 mRNA levels, indicating that HS presents CCL21 on HEVs in vivo. Notably, a short-term lymphocyte homing assay indicated that lymphocyte homing to PLNs was diminished in the cKO mice by 30-40%. Consistent with this result, contact hypersensitivity responses were also diminished in the cKO mice. The residual lymphocyte homing to PLNs in the cKO mice was dependent on pertussis toxin-sensitive Gi protein signaling, in which lysophosphatidic acid-mediated signaling was partly involved. These results suggest that chemokine presentation by HS on the surface of HEVs facilitates but is not absolutely required for lymphocyte homing.

Enhancement of cell-cell contact by claudin-4 in renal epithelial Madin-Darby canine kidney cells.

Claudin-4 regulates ion permeability via a paracellular pathway in renal epithelial cells, but its other physiological functions have not been examined. We found that hyperosmotic stress increases claudin-4 expression in Madin-Darby canine kidney cells. Here, we examined whether claudin-4 affects cell motility, cell association, and the intracellular distribution of endogenous junctional proteins. Doxycycline-inducible expression of claudin-4 did not change endogenous levels of claudin-1, claudin-2, claudin-3, occludin, E-cadherin, and ZO-1. Claudin-4 overexpression increased cell association and decreased cell migration without affecting cell proliferation. Doxycycline did not change cell junctional protein levels, cell association or cell migration in mock-transfected cells. The insolubility of claudin-1 and -3 in Triton X-100 was increased by claudin-4 overexpression, but that of claudin-2, occludin, ZO-1, and E-cadherin was unchanged. Immunocytochemistry showed that claudin-4 overexpression increases the accumulation of claudin-1 and -3 in tight junctions (TJs). Furthermore, claudin-4 overexpression increased the association of claudin-4 with claudin-1 and -3. These results suggest that claudin-4 accumulates claudin-1 and -3 in TJs to enhance cell-cell contact in renal tubular epithelial cells.

Essential role of peripheral node addressin in lymphocyte homing to nasal-associated lymphoid tissues and allergic immune responses.

Nasal-associated lymphoid tissue (NALT) is a mucosal immune tissue that provides immune responses against inhaled antigens. Lymphocyte homing to NALT is mediated by specific interactions between lymphocytes and high endothelial venules (HEVs) in NALT. In contrast to HEVs in other mucosal lymphoid tissues, NALT HEVs strongly express peripheral node addressins (PNAds) that bear sulfated glycans recognized by the monoclonal antibody MECA-79. We investigated the role of PNAd in lymphocyte homing to NALT using sulfotransferase N-acetylglucosamine-6-O-sulfotransferase (GlcNAc6ST) 1 and GlcNAc6ST-2 double knockout (DKO) mice. The expression of PNAd in NALT HEVs was eliminated in DKO mice. Short-term homing assays indicated that lymphocyte homing to NALT was diminished by 90% in DKO mice. Production of antigen-specific IgE and the number of sneezes in response to nasally administered ovalbumin were also substantially diminished. Consistently, the NALT of DKO mice showed reduced production of IL-4 and increased production of IL-10 together with an increase in CD4(+)CD25(+) regulatory T cells (T(reg) cells). Compared with the homing of CD4(+)CD25(-) conventional T cells, the homing of CD4(+)CD25(+) T(reg) cells to NALT was less dependent on the L-selectin-PNAd interaction but was partially dependent on PSGL-1 (P-selectin glycoprotein ligand 1) and CD44. These results demonstrate that PNAd is essential for lymphocyte homing to NALT and nasal allergic responses.

Novel anti-carbohydrate antibodies reveal the cooperative function of sulfated N- and O-glycans in lymphocyte homing.

Cell surface glycans play pivotal roles in immune cell trafficking and immunity. Here we present an efficient method for generating anti-carbohydrate monoclonal antibodies (mAbs) using gene-targeted mice and describe critical glycans in lymphocyte homing. We immunized sulfotransferase GlcNAc6ST-1 and GlcNAc6ST-2 doubly deficient mice with sulfotransferase-overexpressing Chinese hamster ovary cells and generated two mAbs, termed S1 and S2. Both S1 and S2 bound high endothelial venules (HEVs) in the lymphoid organs of humans and wild-type mice, but not in those of doubly deficient mice. Glycan array analysis indicated that both S1 and S2 specifically bound 6-sulfo sialyl Lewis X and its defucosylated structure. Interestingly, S2 inhibited lymphocyte homing to peripheral lymph nodes by 95%, whereas S1 inhibited it by only 25%. S2 also significantly inhibited contact hypersensitivity responses and L-selectin-dependent leukocyte adhesion to HEVs. Immunohistochemical and Western blot analyses indicated that S1 preferentially bound sulfated O-glycans, whereas S2 bound both sulfated N- and O-glycans in HEVs. Furthermore, S2 strongly inhibited the N-glycan-dependent residual lymphocyte homing in mutant mice lacking sulfated O-glycans, indicating the importance of both sulfated N- and O-glycans in lymphocyte homing. Thus, the two mAbs generated by a novel method revealed the cooperative function of sulfated N- and O-glycans in lymphocyte homing and immune surveillance.

Conditional gene targeting in mouse high endothelial venules.

High endothelial venules (HEVs) are specialized blood vessels of secondary lymphoid organs composed of endothelial cells with a characteristic cuboidal morphology. Lymphocytes selectively adhere to and migrate across HEVs to initiate immune responses. In this study, we established a novel transgenic mouse line expressing Cre recombinase under the transcriptional control of the gene encoding HEV-expressed sulfotransferase, N-acetylglucosamine-6-O-sulfotransferase 2 (GlcNAc6ST-2), using bacterial artificial chromosome recombineering. Crossing these transgenic mice with the ROSA26 reporter strain, which expresses lacZ following Cre-mediated recombination, and staining the resulting progeny with 5-bromo-4-chloro-5-indolyl-beta-D-galactoside indicated that Cre recombinase was specifically expressed in mAb MECA79-reactive HEVs in secondary lymphoid organs but not in any other blood vessels of the transgenic mice. The expression of Cre recombinase correlated with a developmental switch, from immature, mAb MECA367-reactive HEVs to mature, mAb MECA79-reactive HEVs in neonatal lymph nodes. In addition to the HEVs, Cre recombinase was also strongly expressed in the colonic villi, which recapitulated the intrinsic expression of GlcNAc6ST-2 as confirmed in GlcNAc6ST-2(GFP/GFP) knock-in mice and by RT-PCR. Furthermore, treatment with an antimicrobial agent revealed that the colonic expression of Cre recombinase in the transgenic mice was regulated by commensal bacteria in the colon. In addition, Cre recombinase was expressed in a small subset of cells in the brain, testis, stomach, small intestine, and lung. In view of the restricted expression of Cre recombinase, this transgenic mouse line should be useful for elucidating tissue-specific gene functions using the Cre/loxP system.