Anti-infective bovine colostrum oligosaccharides: Campylobacter jejuni as a case study

Abstract

Campylobacter jejuni is the leading cause of acute bacterial infectious diarrhea in humans. Unlike in humans, C. jejuni is a commensal within the avian host. Heavily colonized chickens often fail to display intestinal disease, and no cellular attachment or invasion has been demonstrated in-vivo. Recently, researchers have shown that the reason for the attenuation of C. jejuni virulence may be attributed to the presence of chicken intestinal mucus and more specifically chicken mucin. Since mucins are heavily glycosylated molecules this observation would suggest that glycan-based compounds may act as anti-infectives against C. jejuni. Considering this, we have investigated naturally sourced foods for potential anti-infective glycans. Bovine colostrum rich in neutral and acidic oligosaccharides has been identified as a potential source of anti-infective glycans. In this study, we tested oligosaccharides isolated and purified from the colostrum of Holstein Friesian cows for anti-infective activity against a highly invasive strain of C. jejuni. During our initial studies we structurally defined 37 bovine colostrum oligosaccharides (BCO) by HILIC-HPLC coupled with exoglycosidase digests and off-line mass spectroscopy, and demonstrated the ability of C. jejuni to bind to some of these structures, in-vitro. We also examined the effect of BCO on C. jejuni adhesion to, invasion of and translocation of HT-29 cells. BCO dramatically reduced the cellular invasion and translocation of C. jejuni, in a concentration dependent manner. Periodate treatment of the BCO prior to inhibition studies resulted in a loss of the anti-infective activity of the glycans suggesting a direct oligosaccharide-bacterial interaction. This was confirmed when the BCO completely prevented C. jejuni binding to chicken intestinal mucin, in-vitro. This study builds a strong case for the inclusion of oligosaccharides sourced from cow's milk in functional foods. However, it is only through further understanding the structure and function of milk oligosaccharides that such compounds can reach their potential as food ingredients.