Lectin-mediated binding and sialoglycans of porcine surfactant protein D synergistically neutralize influenza A virus.van Eijk, M., Rynkiewicz, M.J., Khatri, K., Leymarie, N., Zaia, J., White, M.R., Hartshorn, K.L., Cafarella, T.R., van Die, I., Hessing, M., Seaton, B.A., Haagsman, H.P.
(2018) J Biol Chem 293: 10646-10662
- PubMed: 29769321
- DOI: 10.1074/jbc.RA117.001430
- Primary Citation of Related Structures:
- PubMed 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) to interact with IAV ...
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) 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 neck-CRD 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 nonlectin-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 Asn-303 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 Lewis Y structures, whereas RhNCRD bound polylactosamine-containing glycans. The 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.
From the Department of Infectious Diseases and Immunology, Faculty of Veterinary Medicine, Utrecht University, 3584 CL Utrecht, The Netherlands.