Glycomaterials for immunomodulation via affinity-dependent regulation of soluble lectin bioactivity

摘要

Introduction: Recognition of cell surface glycans by carbohydrate-binding proteins (i.e. "lectins") modulates numerous aspects of innate and adaptive immune cell function, which has led to increasing recent interest in lectins as targets for immunotherapy and immunomodulation. However, lectin-glycan interactions are a double-edged sword in immunity - they provide outside-in signals that direct healthy immune responses, such as inflammation resolution and antigen-specific tolerance, which can be hijacked during progression of immunopathologies, such as tumor immune phvilege and viral infection. Thus, effective therapeutics must be designed to either enhance or inhibit lectin-glycan interactions according to the intended immunological outcome. Toward that end, here we describe glycosylated biomaterials that can inhibit lectin bioactivity via non-covalent capture within lectin-rich environments, or harness lectin bioactivity via controlled release into lectin-poor environments. Specifically, we created a glycopeptide, N(n-acetylglucosamine)-SGSG-QQKFQFQFEQQ (GlcNAc-Q11), which self-assembles into nanofibers under aqueous conditions. The pendant glycan moieties along the nanofiber confer non-covalent lectin-binding properties that can be tailored by varying glycan concentration or chemistry. Methods: Peptides were synthesized using established methods. Nanofibers were prepared by dissolving lyophilized peptides in water, then diluting these stock solutions 10-fold with 1x phosphate-buffered saline (pH 7.4). Lectin binding and release were assessed via trypophan fluorescence. Microgels were fabricated by diluting aqueous mixtures of WGA and Q11/GlcNAc-Q11 nanofibers in ethanol, according to established methods. WGA bioactivity was assessed using a Jurkat T cell apoptosis assay that measures cell protease activity. Results: GlcNAc-Q11 nanofibers bound WGA in a GlcNAc-concentration dependent manner, while nanofibers displaying the disaccharide, n-acetyllactosamine (LacNAc), failed to bind WGA (Figure 1a). Conversely, LacNAc-Q11 nanofibers preferentially bound a LacNAc-binding lectin, galectin-1 (data not shown). Glycopeptide nanofibers inhibited WGA- or galectin-mediated apoptosis of Jurkat T cells in a GlcNAc- or LacNAc-concentration dependent manner (Figure 1 b-c), respectively, likely by sequestering the lectin away from the cell surface. WGA was efficiently encapsulated into microgels fabricated via desolvation of mixed Q11/GlcNAc-Q11 nanofibers. Microgels released encapsulated WGA payloads into lectin-poor environments, with kinetics that could be tailored by varying GlcNAc content of the nanofibers (Figure 1 d). Released WGA induced Jurkat T cell apoptosis with similar activity as stock lectin, demonstrating that WGA bioactivity was maintained during encapsulation and release (Figure 1 e). Conclusions: Glycosylated biomaterials can regulate lectin bioactivity via affinity-dependent mechanisms. In particular, glycopeptide nanofibers that capture lectins within a lectin-rich environment can maintain T cell viability. Conversely, microgels that release lectin payloads into lectin-poor environments can induce T cell apoptosis. Thus, glycosylated biomaterials hold promise for creating therapeutics that can enhance or inhibit lectin-glycan interactions to elicit desired immunological responses.