We previously found that scavenger receptor cysteine-rich gp-340 (glycoprotein-340), isolated from lung or saliva, directly inhibits human IAVs (influenza A viruses). We now show that salivary gp-340 has broad antiviral activity against human, equine and porcine IAV strains. Although lung and salivary gp-340 are identical in protein sequence, salivary gp-340 from one donor had significantly greater antiviral activity against avian-like IAV strains which preferentially bind sialic acids in α(2,3) linkage. A greater density of α(2,3)-linked sialic acids was present on the salivary gp-340 from this donor as compared with salivary gp-340 from another donor or several preparations of lung gp-340. Hence, the specificity of sialic acid linkages on gp-340 is an important determinant of anti-IAV activity. Gp-340 binds to SP-D (surfactant protein D), and we previously showed that lung gp-340 has co-operative interactions with SP-D in viral neutralization and aggregation assays. We now report that salivary gp-340 can, in some cases, strongly antagonize certain antiviral activities of SP-D. This effect was associated with greater binding of salivary gp-340 to the carbohydrate recognition domain of SP-D as compared with the binding of lung gp-340. These findings may relate to inter-individual variations in innate defence against highly pathogenic IAV and to effects of aspiration of oral contents on SP-D-mediated lung functions.
Salivary agglutinin and lung scavenger receptor cysteine-rich glycoprotein 340 have broad anti-influenza activities and interactions with surfactant protein D that vary according to donor source and sialylation
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Kevan L. Hartshorn, Antoon Ligtenberg, Mitchell R. White, Martin van Eijk, Max Hartshorn, Lily Pemberton, Uffe Holmskov, Erika Crouch; Salivary agglutinin and lung scavenger receptor cysteine-rich glycoprotein 340 have broad anti-influenza activities and interactions with surfactant protein D that vary according to donor source and sialylation. Biochem J 15 January 2006; 393 (2): 545–553. doi: https://doi.org/10.1042/BJ20050695
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