Exploitation of SPR to Investigate the Importance of Glycan Chains in the Interaction between Lactoferrin and Bacteria

Abstract

Bovine lactoferrin (LF) has been shown to prevent adhesion to and invasion of mammalian cell lines by pathogenic bacteria, with evidence for direct bacterial binding by the milk glycoprotein. However, the glycosylation pattern of LF changes over the lactation cycle. In this study, we aim to investigate the effect that this variation has on the milk glycoprotein's ability to interact with pathogens. Surface plasmon resonance technology was employed to compare the binding of LF from colostrum (early lactation) and mature milk (late lactation) to a panel of pathogenic bacteria (Staphylococcus aureus, Escherichia coli, Cronobacter sakazakii, Streptococcus pneumoniae, Pseudomonas aeruginosa, Listeria monocytogenes and Salmonella typhimurium). Novel interactions with LF were identified for C. sakazakii, S. pneumoniae and P. aeruginosa with the highest binding ability observed for mature milk LF in all cases, with the exception of S. typhimurium. The difference in bacterial binding observed may be as a result of the varying glycosylation profiles. This work demonstrates the potential of LF as a functional food ingredient to prevent bacterial infection.

Keywords: bacterial binding; glycosylation; lactation; lactoferrin; surface plasmon resonance.

Figure 1

Increasing concentrations of Staphylococcus aureus DPC 5971 (red) and Escherichia coli O157:H7 P1432 (blue) injected over the surface of a streptavidin (SA) chip with mature LF immobilised to evaluate effect of increasing bacterial numbers on the response units (RU) response.

Figure 2

RU changes following exposure of a panel of pathogenic bacteria to LF from colostrum (white) or mature milk (grey) immobilised on a Biacore SA chip. E. coli P1432 was identified as a negative control and its response was marked as the minimum requirement for consideration as a positive interaction (black horizontal line). All bacteria were applied at a concentration of 1 × 10⁸ CFU·mL⁻¹.