Influenza virus hemagglutinin glycoproteins with different N-glycan patterns activate dendritic cells in vitro

Influenza virus hemagglutinin (HA) N-glycans play important regulatory roles in the control of virus virulence, antigenicity, receptor-binding specificity, and viral escape from the immune response. Considered essential for controlling innate and adaptive immune responses against influenza virus infections, dendritic cells (DCs) trigger proinflammatory and adaptive immune responses in hosts. In this study, we engineered Chinese hamster ovary (CHO) cell lines expressing recombinant HA from pandemic H1, H5, and H7 influenza viruses. rH1HA, rH5HA, and rH7HA were obtained as wild-type proteins or in the presence of kifunensine (KIF) or further with endo-β-N-acetylglucosaminidase-treated KIF (KIF+E) to generate single-N-acetylglucosamine (GlcNAc) N-glycans consisting of (i) terminally sialylated complex-type N-glycans, (ii) high-mannose-type N-glycans, and (iii) single-GlcNAc-type N-glycans. Our results show that high-mannose-type and single-GlcNAc-type N-glycans, but not complex-type N-glycans, are capable of inducing more active hIL12 p40, hIL12 p70, and hIL-10 production in human DCs. Significantly higher HLA-DR, CD40, CD83, and CD86 expression levels, as well reduced endocytotic capacity in human DCs, were noted in the high-mannose-type rH1HA and single-GlcNAc-type rH1HA groups than in the complex-type N-glycan rH1HA group. Our data indicate that native avian rHA proteins (H5N1 and H7N9) are more immunostimulatory than human rHA protein (pH1N1). The high-mannose-type or single-GlcNAc-type N-glycans of both avian and human HA types are more stimulatory than the complex-type N-glycans. HA-stimulated DC activation was accomplished partially through a mannose receptor(s). These results provide more understanding of the contribution of glycosylation of viral proteins to the immune responses and may have implications for vaccine development.