Human norovirus inhibition by a human milk oligosaccharide

Abstract

Human noroviruses are the leading cause of outbreaks of acute gastroenteritis. Norovirus interactions with histo-blood group antigens (HBGAs) are known to be important for an infection. In this study, we identified the HBGA binding pocket for an emerging GII genotype 17 (GII.17) variant using X-ray crystallography. The GII.17 variant bound the HBGA with an equivalent set of residues as the leading pandemic GII.4 variants. These structural data highlights the conserved nature of HBGA binding site between prevalent GII noroviruses. Noroviruses also interact with human milk oligosaccharides (HMOs), which mimic HBGAs and may function as receptor decoys. We previously showed that HMOs inhibited the binding of rarely detected GII.10 norovirus to HBGAs. We now found that an HMO, 2'-fucosyllactose (2'FL), additionally blocked both the GI.1 and GII.17 noroviruses from binding to HBGAs. Together, these findings provide evidence that 2'FL might function as a broadly reactive antiviral against multiple norovirus genogroups.

Human Milk Oligosaccharides as Promising Antivirals

“…In the GII noroviruses, the coordination occurs at a dimeric interface of the P domain dimer and involves residues from both monomers (Figure A). In both the pandemic GII.4 and rapidly evolving GII.17 strains, the HBGA binding pocket is remarkably similar and accounts for various HBGA types ( Table ) …”

“…This can be utilized by HMOs, structurally similar to HBGA epitopes to provide antiviral protection. Indeed, structural analysis revealed that 2′FL occupied the HBGAs’ binding pocket of GII.10 and the emerging GII.17 norovirus strain in a manner that was essentially identical to HBGAs. The coordination of 2′FL was also preserved among three complexes (Figure B and C).…”

“…Estimated by porcine gastric mucin and saliva‐based HBGA blockade assays, the efficacy of the 2′FL inhibition was lower against more dominant noroviruses. The half‐maximal inhibitory concentrations (IC 50 ) for 2′FL were in the 5–30, 20–64, 13–20, and 38–50 m m ranges for GII.10, GII.4, GII.17, and GI.1 norovirus VLPs, respectively . Considering that the concentration of 2′FL in human milk is 2–4 m m , one may expect that 2′FL acts as a weak natural antiviral in human milk.…”

“…In both the pandemic GII.4 and rapidly evolving GII.17 strains, the HBGA binding pocket is remarkably similar and accounts for various HBGA types ( Table 1). [68,69,72] The similarity of the HBGA binding pocket among the most clinically relevant GII noroviruses indicates that it may serve as a site of vulnerability. This can be utilized by HMOs, structurally similar to HBGA epitopes to provide antiviral protection.…”

“…The terminal fucose binding was mediated through a number of hydrophilic and hydrophobic contacts from highly conserved amino residues (Thr348, Arg349, Asp378, Gly443, and Tyr444), whereas the remaining disaccharide units were relatively less engaged by the capsid proteins. Interestingly, despite the apparent differences in the HBGA recognitions sites, GI.1 norovirus (Norwalk) capsid also bound [70,73] GII.10 (Vietnam 026) A type, H type, Le b , Le y , Le x 2 FL, 3FL [14,60] GII.4 (VA387) n/d 2 FL, LNFP III, 3FL [73,75] GII.4 (UNSW) A-type, B type, Le x n/d [69] GII.4 (Saga) A-type, B type, Le b , Le y , Le x n/d [69] GII.17 (Kawasaki 308) A-type, B type 2 FL [72] Rotavirus P [4] (DS-1) A-type, H-type I, and Le b HBGAs n/d [88] P [6] (RV3) A-type, H-type I, and Le x HBGAs n/d [88] P [8] (WA) H-type I, and Le b HBGAs, GM1 LNDFH I [88] P [11] (N155) type 1 and type 2 HBGA precursors LNT, LNnT [95] P [14] (HAL1166) A-type HBGAs n/d [89] P [19] (MC345) A-type I, B type I, H-type I LNFP I, LNT [88] P [4] (LD26) n/d LNDFH I [88] P [9] (K8) A-type HBGAs n/d [89,91] P [6] (ST3) H-type I LNFP I, LNT [88] Influenza Influenza A SA-α2,6-Gal 6 SL [102] Human strains H1N1, A/Brisbane/59/2007 SA-α2,6-Gal 6 SL, HMOs with the SA-α2,6-Gal-β1,4-GlcNAc moiety [94] H1N1, A/Oklahoma/447/2008 SA-α2,6-Gal Figure 4D). Both, the terminal fucose and the central galactose, were captured by the GI.1 capsid residues (Gln342, Asp344, Asp327, Ser377, and Pro378).…”