A mannose-binding lectin from helianthus annuus recognizes GP120 from HIV-1 and promotes phonotype maturation in dendritic cells

Abstract

Background: Plant lectins have potential use in biomedicine as antimicrobial reagents due to their binding specificity to glycoconjugates. Helja is a mannose-binding lectin isolated from sunflower seeds. Half of the molecular mass of the HIV-1 envelope glycoprotein (gp120) is constituted by high-mannose and complex N-glycans. The aim of this work is to analyze if Helja could recognize gp120 and induce dendritic cell maturation. Methods: Helja was purified from Helianthus annuus seeds on a D-mannose-agarose affinity chromatography. Potential molecular interaction between Helja and recombinant gp120 (M Group, B Subtype, SinoBiological, USA) was evaluated by dot blot and ligand blot approaches using anti-Helja antibodies. Bone marrow dendritic cells (BMDCs) were cultured in complete RPMI medium supplemented with FLT3-L. Cellular activation state was evaluated in Helja-treated BMDCs by measuring membrane proteins (CD86, CD40, MHCII, CD11c, CD80, Clec9a, Ly6G, SIPRα, CD103, SiglecH) by FACS. Results: The interaction of Helja with gp120 was initially detected in dot blot assays by immunodetection of lectin bound to viral protein immobilized on nitrocellulose membranes. This interaction was confirmed in ligand blot assays by detecting a signal whose molecular weight corresponds to gp120 (95 kDa). On the other hand, the presence of Helja (10 µg/ml) in BMDC culture induced an upregulation of MHCII, MHCI, CD80, CD40 and CD86 (n=3, **p<0.01 Helja-treated BMDCs vs controls, *p<0.05 Helja+LPS-treated BMDCs vs LPS control). No changes in Clec9a, Ly6G, SIRPα, CD103 and SiglecH were detected. Conclusions: These results suggest that Helja induces dendritic cell maturation, important to promote immune activation, and recognizes specific glycosidic residues and arrangements on the HIV-1 envelope protein which could have a potential biomedical use as a phyto-neutralizing agent in viral infection.