Lectin-mediated binding and sialoglycans of porcine surfactant protein D synergistically neutralize influenza A virus
van Eijk, Martin; Rynkiewicz, Michael J; Khatri, Kshitij; Leymarie, Nancy; Zaia, Joseph; White, Mitchell R; Hartshorn, Kevan L; Cafarella, Tanya R; van Die, Irma; Hessing, Martin; Seaton, Barbara A; Haagsman, Henk P
(2018) Journal of Biological Chemistry, volume 293, issue 27, pp.
(Article)
Abstract
Innate immunity is critical in the early containment of influenza A virus (IAV) infection, and surfactant protein D (SP-D) plays a crucial role in the pulmonary defense against IAV. In pigs, which are important intermediate hosts during the generation of pandemic IAVs, SP-D uses its unique carbohydrate recognition domain (CRD)
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to interact with IAV. An N-linked CRD-glycosylation provides interactions with the sialic acid binding site of IAV, and a tripeptide loop at the lectin binding site facilitates enhanced interactions with IAV glycans. Here, to investigate both mechanisms of IAV neutralization in greater detail, we produced an N-glycosylated neckCRD fragment of porcine SP-D (RpNCRD) in HEK293 cells. X-ray crystallography disclosed that the N-glycan did not alter the CRD backbone structure including the lectin site conformation, but revealed a potential second non-lectin binding site for glycans. IAV hemagglutination inhibition, IAV aggregation and neutralization of IAV infection studies showed that RpNCRD, unlike the human analogue RhNCRD, exhibits potent neutralizing activity against pandemic A/Aichi/68 (H3N2), enabled by both porcine-specific structural features of its CRD. MS analysis revealed an N-glycan site-occupancy of >98% at Asn303 of RpNCRD with complex-type, heterogeneously branched and predominantly α(2,3) sialylated oligosaccharides. Glycan binding array data characterized both RpNCRD and RhNCRD as mannose-type lectins. RpNCRD also bound LewisY structures whereas RhNCRD bound polylactosamine-containing glycans. Presence of the N-glycan in the CRD increases the glycan binding specificity of RpNCRD. These insights increase our understanding of porcine-specific innate defense against pandemic IAV and may inform the design of recombinant SP-D-based antiviral drugs.
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Keywords: host–pathogen interaction, innate immunity, influenza virus, collectin, N-linked glycosylation, sialic acid, antiviral agent, structural biology, drug design, viral immunology, porcine immunology, pulmonary defense, recombinant protein, surfactant protein D
ISSN: 0021-9258
Publisher: American Society for Biochemistry and Molecular Biology Inc.
Note: Published under license by The American Society for Biochemistry and Molecular Biology, Inc.
(Peer reviewed)
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