Suppressing Immune Responses Using Siglec Ligand-Decorated Anti-receptor Antibodies.

The sialic acid-binding immunoglobulin-type lectins (Siglecs) are expressed predominantly on white blood cells and participate in immune cell recognition of self. Most Siglecs contain cytoplasmic inhibitory immunoreceptor tyrosine-based inhibitory motifs characteristic of inhibitory checkpoint co-receptors that suppress cell signaling when they are recruited to the immunological synapse of an activating receptor. Antibodies to activatory receptors typically activate immune cells by ligating the receptors on the cell surface.

Coordinated changes in glycosylation regulate the germinal center through CD22.

Germinal centers (GCs) are essential for antibody affinity maturation. GC B cells have a unique repertoire of cell surface glycans compared with naive B cells, yet functional roles for changes in glycosylation in the GC have yet to be ascribed. Detection of GCs by the antibody GL7 reflects a downregulation in ligands for CD22, an inhibitory co-receptor of the B cell receptor.

Tolerogenic Nanoparticles Impacting B and T Lymphocyte Responses Delay Autoimmune Arthritis in K/BxN Mice.

Current treatments for unwanted antibody responses largely rely on immunosuppressive drugs compromising overall immunity. New approaches to achieve antigen-specific tolerance are desirable to avoid unwanted side effects. Several nanoparticle-based approaches that utilize different mechanisms to tolerize the B or T cell arms of the humoral immune response have shown promise for induction of antigen-specific tolerance, raising the possibility that they could work synergistically if combined.

Nanoparticles Displaying Allergen and Siglec-8 Ligands Suppress IgE-FcεRI-Mediated Anaphylaxis and Desensitize Mast Cells to Subsequent Antigen Challenge.

Siglec-8 is an inhibitory receptor expressed on eosinophils and mast cells. In this study, we took advantage of a novel Siglec-8 transgenic mouse model to assess the impact of modulating IgE-dependent mast cell degranulation and anaphylaxis using a liposomal platform to display an allergen with or without a synthetic glycan ligand for Siglec-8 (Sig8L). The hypothesis is that recruitment of Siglec-8 to the IgE-FcεRI receptor complex will inhibit allergen-induced mast cell degranulation.

Different genetic barriers for resistance to HA stem antibodies in influenza H3 and H1 viruses.

The discovery and characterization of broadly neutralizing human antibodies (bnAbs) to the highly conserved stem region of influenza hemagglutinin (HA) have contributed to considerations of a universal influenza vaccine. However, the potential for resistance to stem bnAbs also needs to be more thoroughly evaluated. Using deep mutational scanning, with a focus on epitope residues, we found that the genetic barrier to resistance to stem bnAbs is low for the H3 subtype but substantially higher for the H1 subtype owing to structural differences in the HA stem.

Agonist Antibody Converts Stem Cells into Migrating Brown Adipocyte-Like Cells in Heart.

We present data showing that Iodotyrosine Deiodinase (IYD) is a dual-function enzyme acting as a catalyst in metabolism and a receptor for cooperative stem cell differentiation. IYD is present both in thyroid cells where it is critical for scavenging iodine from halogenated by-products of thyroid hormone production and on hematopoietic stem cells. To close the cooperative loop, the mono- and di-Iodotyrosine (MIT and DIT) substrates of IYD in the thyroid are also agonists for IYD now acting as a receptor on bone marrow stem cells.

An agonist antibody prefers relapsed AML for induction of cells that kill each other.

Previously, we reported an agonist antibody to a cytokine receptor, Thrombopoietin receptor (TPOR) that effectively induces cytotoxic killer cells from precursor tumor cells isolated from newly diagnosed AML patients. Here, we show that the TPOR agonist antibody can induce even relapsed AML cells into killer cells more potently than newly diagnosed AML cells. After stimulation by the agonist antibody, these relapsed leukemic cells enter into a differentiation process of killer cells.

Migration-based selections of antibodies that convert bone marrow into trafficking microglia-like cells that reduce brain amyloid β.

One goal of regenerative medicine is to repair damaged tissue. This requires not only generating new cells of the proper phenotype, but also selecting for those that properly integrate into sites of injury. In our laboratory we are using a cell-migration-based in vivo selection system to generate antibodies that induce cells to both differentiate and selectively localize to different tissues.

Human CD22 Inhibits Murine B Cell Receptor Activation in a Human CD22 Transgenic Mouse Model.

CD22, a sialic acid-binding Ig-type lectin (Siglec) family member, is an inhibitory coreceptor of the BCR with established roles in health and disease. The restricted expression pattern of CD22 on B cells and most B cell lymphomas has made CD22 a therapeutic target for B cell-mediated diseases. Models to better understand how in vivo targeting of CD22 translates to human disease are needed.

Encapsulating an Immunosuppressant Enhances Tolerance Induction by Siglec-Engaging Tolerogenic Liposomes.

Unwanted antibody responses significantly impact human health, and current options for treating deleterious antibody responses largely rely on broad immunosuppressants that can compromise overall immunity. A desirable alternative is to induce antigen-specific immune tolerance. We have shown that co-presentation of antigen and ligands of B cell sialic acid-binding immunoglobulin-like lectins (Siglecs) on a liposomal nanoparticle induces antigen-specific tolerance.

Siglec-F is a novel intestinal M cell marker.

Intestinal microfold (M) cells are epithelial cells primarily present on Peyer's patches (PPs) in the small intestine. The ability of M cells to shuttle antigens into the PP for appropriate immune responses makes M cells a target for next-generation oral vaccine delivery. In this regard, discovery of M cell-specific receptors are of great interest, which could act as molecular tags for targeted delivery of cargo to M cells.

Unmasking of CD22 Co-receptor on Germinal Center B-cells Occurs by Alternative Mechanisms in Mouse and Man.

CD22 is an inhibitory B-cell co-receptor whose function is modulated by sialic acid (Sia)-bearing glycan ligands. Glycan remodeling in the germinal center (GC) alters CD22 ligands, with as yet no ascribed biological consequence. Here, we show in both mice and humans that loss of high affinity ligands on GC B-cells unmasks the binding site of CD22 relative to naive and memory B-cells, promoting recognition of trans ligands.

Systemic blockade of sialylation in mice with a global inhibitor of sialyltransferases.

Sialic acid terminates glycans of glycoproteins and glycolipids that play numerous biological roles in health and disease. Although genetic tools are available for interrogating the effects of decreased or abolished sialoside expression in mice, pharmacological inhibition of the sialyltransferase family has, to date, not been possible. We have recently shown that a sialic acid analog, 2,4,7,8,9-pentaacetyl-3Fax-Neu5Ac-CO2Me (3F-NeuAc), added to the media of cultured cells shuts down sialylation by a mechanism involving its intracellular conversion to CMP-3F-NeuAc, a competitive inhibitor of all sialyltransferases.

Disubstituted Sialic Acid Ligands Targeting Siglecs CD33 and CD22 Associated with Myeloid Leukaemias and B Cell Lymphomas.

The siglec family of sialic acid-binding proteins are endocytic immune cell receptors that are recognized as potential targets for cell directed therapies. CD33 and CD22 are prototypical members and are validated candidates for targeting acute myeloid leukaemia and non-Hodgkin's lymphomas due to their restricted expression on myeloid cells and B-cells, respectively. While nanoparticles decorated with high affinity siglec ligands represent an attractive platform for delivery of therapeutic agents to these cells, a lack of ligands with suitable affinity and/or selectivity has hampered progress.

Mucosal immunization with a Staphylococcus aureus IsdA-cholera toxin A2/B chimera induces antigen-specific Th2-type responses in mice.

Staphylococcus aureus is a leading cause of opportunistic infection worldwide and a significant public health threat. The iron-regulated surface determinant A (IsdA) adhesin is essential for S. aureus colonization on human nasal epithelial cells and plays an important role in iron acquisition and resistance to human skin defenses.