Immunostimulatory glucose polymers known as beta-glucans have been studied for many years. Our laboratory has prepared and characterized a novel microparticulate beta-glucan (MG) from the budding yeast Saccharomyces cerevisiae. Because MG particles are rapidly phagocytized by murine peritoneal macrophages and induce the expression of B7 costimulatory molecules, we hypothesized that MG could serve as a vaccine adjuvant to enhance specific immune responses. Here, we describe a procedure for conjugating the test vaccine antigen bovine serum albumin (BSA) to MG via water-soluble carbodiimide linkage. Conjugates with up to 0.4 mg of BSA/mg MG were prepared. MG/BSA conjugates were still actively phagocytized by mouse peritoneal macrophages. When used to immunize mice by the intradermal route, these conjugates enhanced the primary IgG antibody response to BSA in a manner comparable to the prototypic complete Freund's adjuvant. Although primary oral immunization with MG/BSA caused no increase in serum anti-BSA antibody titers, booster immunization elicited a significant anti-BSA antibody response. These results suggest that protein antigens can be conjugated to MG via a carbodiimide linkage and that these conjugates provide an adjuvant effect for stimulating the antibody response to the protein antigens.
"An overview of all required steps to synthesize these antibody functionalized GPs is given in Figure 1. First, protein G was conjugated to the particles via carbodiimide crosslinker chemistry   . Briefly, BSA-FITC GPs (500 µg/ml) were centrifuged (500 g, 5 min) and resuspended in 1 ml 2-(N-morpholino)ethanesulfonic acid (MES) buffer (0.1 M MES; pH 6.0). "
[Show abstract][Hide abstract] ABSTRACT: Enteric diseases still have a devastating impact on global health. Oral vaccination is crucial to prevent intestinal infections, since only vaccines delivered to the intestinal tract elicit potent immune responses at the site of pathogen entry. However, oral vaccines encounter multiple barriers, including poor uptake and tolerance mechanisms, preventing the immune system to react to innocuous environmental antigens. Antigen delivery systems combined with selective targeting seem a promising strategy to overcome these obstacles. The current study evaluates the capacity of aminopeptidase N (APN)-targeted β-glucan microparticles (GPs) as antigen delivery system. Antibodies against APN, an intestinal epithelial receptor, are efficiently oriented conjugated to GPs via the biolinker protein G. The resultant microparticles were analyzed for their antigen load, adjuvanticity and interaction with enterocytes and dendritic cells (DCs). Functionalization of GPs with antibodies neither impedes antigen load nor adjuvanticity. In addition, targeting to APN increases the uptake of microparticles by enterocytes and DCs, leading to an enhanced maturation of the latter as evidenced by an upregulation of maturation markers and a strong pro-inflammatory cytokine response. Finally, oral administration of APN-targeted antigen-loaded particles to piglets elicits higher serum antigen-specific antibody responses as compared to control particles. Taken together, these data support the use of APN-targeted GPs for oral delivery of antigens.
Journal of Controlled Release 10/2015; DOI:10.1016/j.jconrel.2015.10.025 · 7.71 Impact Factor
"This was surprising because a number of studies have used β-glucan supplementation as a method of improving immune responses. Many studies demonstrating positive effects of β-glucans on immunity have used Balb/c mice (Berner et al., 2008; Harnack et al., 2009; Torello et al., 2010; Zhou et al., 2009), thus we are confident that this mouse model is appropriate for studies such as the one described here. "
[Show abstract][Hide abstract] ABSTRACT: Influenza virus is a serious health concern. β-glucans derived from plants, bacteria, and fungi have been shown to potentiate immune system responses including those elicited by vaccination. However, in these studies β-glucan was administered as an adjuvant in the vaccine preparation. We hypothesized that addition of a commercially available whole glucan particle supplement to the diet would improve immune response to primary and secondary influenza vaccination in mice. β-glucan was added to pelleted diet and fed to mice at concentrations designed to deliver 0 (control), 1.8 or 90 mg·kg(-1)·day(-1) to each mouse. Influenza vaccine was given intramuscularly in the left hindlimb and primary and secondary responses were assessed. Supplementation with β-glucan was not effective in boosting immune responses to the vaccine, either in the primary or secondary vaccination experiments. Surprisingly, addition of particulate β-glucan to the vaccine itself also failed to elicit a greater antibody response. These observations suggest that this particular form of β-glucan is ineffective in boosting immune response to intramuscular influenza vaccination. Further study is warranted to determine if the use of different mouse models, different vaccine delivery systems, or β-glucans purified from different strains of bacteria, fungi, or plants could improve outcomes using this or similar protocols.
[Show abstract][Hide abstract] ABSTRACT: beta-Glucans derived from fungal cell walls have potential uses as immunomodulating agents and vaccine adjuvants. Yeast glucan particles (YGPs) are highly purified Saccharomyces cerevisiae cell walls composed of beta1,6-branched beta1,3-d-glucan and free of mannans. YGPs stimulated secretion of the proinflammatory cytokine tumor necrosis factor alpha (TNF-alpha) in wild-type murine bone marrow-derived myeloid dendritic cells (BMDCs) but did not stimulate interleukin-12p70 (IL-12p70) production. A purified soluble beta1,6-branched beta1,3-d-glucan, scleroglucan, also stimulated TNF-alpha in BMDCs. These two beta-glucans failed to stimulate TNF-alpha in Dectin-1 (beta-glucan receptor) knockout BMDCs. Costimulation of wild-type BMDCs with beta-glucans and specific Toll-like receptor (TLR) ligands resulted in greatly enhanced TNF-alpha production but decreased IL-12p70 production compared with TLR agonists alone. The upregulation of TNF-alpha and downregulation of IL-12p70 required Dectin-1, but not IL-10. Gamma interferon (IFN-gamma) priming did not overcome IL-12p70 reduction by beta-glucans. Similar patterns of cytokine regulation were observed in human monocyte-derived dendritic cells (DCs) costimulated with YGPs and the TLR4 ligand lipopolysaccharide. Finally, costimulation of BMDCs with YGPs and either the TLR9 ligand, CpG, or the TLR2/1 ligand, Pam(3)CSK(4), resulted in upregulated secretion of IL-1alpha and IL-10 and downregulated secretion of IL-1beta, IL-6, and IFN-gamma-inducible protein 10 but had no significant effects on IL-12p40, keratinocyte-derived chemokine, monocyte chemotactic protein 1, or macrophage inflammatory protein alpha, compared with the TLR ligand alone. Thus, beta-glucans have distinct effects on cytokine responses following DC stimulation with different TLR agonists. These patterns of response might contribute to the skewing of immune responses during mycotic infections and have implications for the design of immunomodulators and vaccines containing beta-glucans.
Infection and immunity 04/2009; 77(5):1774-81. DOI:10.1128/IAI.00086-09 · 3.73 Impact Factor
Data provided are for informational purposes only. Although carefully collected, accuracy cannot be guaranteed. The impact factor represents a rough estimation of the journal's impact factor and does not reflect the actual current impact factor. Publisher conditions are provided by RoMEO. Differing provisions from the publisher's actual policy or licence agreement may be applicable.