Abstract
Infectious bronchitis virus (IBV) is a highly contagious avian coronavirus. IBV causes substantial worldwide economic losses in the poultry industry. Vaccination with live-attenuated viral vaccines, therefore, are of critical importance. Live-attenuated viral vaccines, however, exhibit the potential for reversion to virulence and recombination with virulent field strains. Therefore, alternatives such as subunit vaccines are needed together with the identification of suitable adjuvants, as subunit vaccines are less immunogenic than live-attenuated vaccines. Several glycan-based adjuvants directly targeting mammalian C-type lectin receptors were assessed in vitro using chicken bone marrow-derived dendritic cells (BM-DCs). The β-1-6-glucan, pustulan, induced an up-regulation of MHC class II (MHCII) cell surface expression, potentiated a strong proinflammatory cytokine response, and increased endocytosis in a cation-dependent manner. Ex vivo co-culture of peripheral blood monocytes from IBV-immunised chickens, and BM-DCs pulsed with pustulan-adjuvanted recombinant IBV N protein (rN), induced a strong recall response. Pustulan-adjuvanted rN induced a significantly higher CD4+ blast percentage compared to either rN, pustulan or media. However, the CD8+ and TCRγδ+ blast percentage were significantly lower with pustulan-adjuvanted rN compared to pustulan or media. Thus, pustulan enhanced the efficacy of MHCII antigen presentation, but apparently not the cross-presentation on MHCI. In conclusion, we found an immunopotentiating effect of pustulan in vitro using chicken BM-DCs. Thus, future in vivo studies might show pustulan as a promising glycan-based adjuvant for use in the poultry industry to contain the spread of coronaviridiae as well as of other avian viral pathogens.
Highlights
Outbreaks of infection caused by coronaviridiae, such as infectious bronchitis virus (IBV), cause substantial economic losses in the poultry industry worldwide
bone marrow-derived dendritic cells (BM-Dendritic cells (DCs)) MHC class II (MHCII) Surface Expression Is Up Regulated by Pustulan, Mannan, and Chitosan
The activation of chicken BM-DCs was analysed to assess the immunostimulatory potential of the glycan-based ligands pustulan, mannan, furfurman, chitosan, monomycolyl glycerol (MMG) and TDB
Summary
Outbreaks of infection caused by coronaviridiae, such as infectious bronchitis virus (IBV), cause substantial economic losses in the poultry industry worldwide. Live-attenuated viral vaccines have good immunogenicity and are commonly used to induce protection against IBV [1]. The activation of the humoral immune system has been shown to be important for IBV-vaccine-induced protection using live-attenuated viral vaccines [2]. Live-attenuated viral vaccines exhibit the potential for reversion to virulence as well as the recombination with virulent field strains with the outcome of a new variant [6]. This makes it desirable to find alternatives such as subunit or inactivated viral vaccines. Subunit- or inactivated viral-based vaccines are far less immunogenic compared to live-attenuated vaccines. Immunopotentiating agents (adjuvants) are needed to boost vaccine efficacy [7,8]
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