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Bovine κ-casein inhibits human rotavirus (HRV) infection via direct binding of glycans to HRV

Authors
  • Inagaki, M.
  • Muranishi, H.
  • Yamada, K.
  • Kakehi, K.
  • Uchida, K.
  • Suzuki, T.
  • Yabe, T.
  • Nakagomi, T.
  • Nakagomi, O.
  • Kanamaru, Y.1, 2, 3, 4, 5
  • 1 United Graduate School of Agricultural Science
  • 2 Faculty of Applied Biological Sciences
  • 3 Faculty of Pharmaceutical Science
  • 4 Central R&D Laboratory
  • 5 Department of Molecular Microbiology and Immunology
Type
Published Article
Journal
Journal of Dairy Science
Publisher
American Dairy Science Association
Publication Date
Jan 01, 2014
Accepted Date
Jan 17, 2014
Identifiers
DOI: 10.3168/jds.2013-7792
Source
Elsevier
Keywords
License
Unknown

Abstract

Human rotavirus (HRV) is a major etiologic agent of severe infantile gastroenteritis. κ-Casein (κ-CN) from both human and bovine mature milk has been reported to have anti-HRV activity; however, the mechanism of this activity is poorly understood. The present study examined the molecular basis for the protective effect of bovine κ-CN derived from late colostrum (6–7 d after parturition) and from mature milk. Among the components of casein, κ-CN is the only glycosylated protein that has been identified. Therefore, we investigated whether the glycan residues in κ-CN were involved in the anti-HRV activity. Desialylated CN obtained by neuraminidase treatment exhibited anti-HRV activity, whereas deglycosylated CN obtained by o-glycosidase treatment lacked antiviral activity, indicating that glycans were responsible for the antiviral activity of CN. Furthermore, an evanescent-field fluorescence-assisted assay showed that HRV particles directly bound to heated casein (at 95°C for 30 min) in a viral titer–dependent manner. Although the heated κ-CN retained inhibitory activity in a neutralization assay, the activity was weaker than that observed before heat treatment. Our findings indicate that the inhibitory mechanism of bovine κ-CN against HRV involves direct binding to viral particles via glycan residues. In addition, heat-labile structures in κ-CN may play an important role in maintenance of κ-CN binding to HRV.

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