The disclosure provides fusion proteins comprising a carbohydrate recognition domain of an innate immunity receptor and a heterologous polypeptide. The fusion proteins of the disclosure may be used, for example, to fingerprint polysaccharide compositions and to purify polysaccharide compositions. Polysaccharide compositions include those isolated from Ganoderma lucidum (Reishi). The methods and reagents of the disclosure may also be used to identify innate immunity receptors and cell types that bind to polysaccharide compositions (including polysaccharide compositions associated with pathogens), whereupon modulators of the identified receptors can then be obtained. The fusion proteins also may be used to inhibit the interaction between a polysaccharide composition and an innate immunity receptor on a cell surface. The methods and reagents of the disclosure are used in one example to determine that the DLVR1 innate immunity receptor on macrophages interacts with Dengue virus (DV), and that DLVR1 is responsible for DV-mediated secretion of proinflammatory cytokines from macrophages. The disclosure also provides DVLR1 antibodies that prevent the secretion of proinflammatory cytokines by DV-infected macrophages.