Bovine Lactoferrin Decreases Cholera-Toxin-Induced Intestinal Fluid Accumulation in Mice by Ganglioside Interaction

Fulton P Rivera,Sandra Bezada,María Bernal,Theresa J Ochoa,Rina Meza,Roberto Valencia,Anicia M Medina,Ryan C Maves,Min Wu

doi:10.1371/journal.pone.0059253

Abstract

Secretory diarrhea caused by cholera toxin (CT) is initiated by binding of CT’s B subunit (CTB) to GM1-ganglioside on the surface of intestinal cells. Lactoferrin, a breast milk glycoprotein, has shown protective effect against several enteropathogens. The aims of this study were to determine the effect of bovine-lactoferrin (bLF) on CT-induced intestinal fluid accumulation in mice, and the interaction between bLF and CT/CTB with the GM1-ganglioside receptor. Fluid accumulation induced by CT was evaluated in the mouse ileal loop model using 56 BALB/c mice, with and without bLF added before, after or at the same time of CT administration. The effect of bLF in the interaction of CT and CTB with GM1-ganglioside was evaluated by a GM1-enzyme-linked immunosorbent assay. bLF decreased CT-induced fluid accumulation in the ileal loop of mice. The greatest effect was when bLF was added before CT (median, 0.066 vs. 0.166 g/cm, with and without bLF respectively, p<0.01). We conclude that bLF decreases binding of CT and CTB to GM1-ganglioside, suggesting that bLF suppresses CT-induced fluid accumulation by blocking the binding of CTB to GM1-ganglioside. bLF may be effective as adjunctive therapy for treatment of cholera diarrhea.

Highlights

Diarrheal disease due to enteric infection is a major cause of death among children under five years of age, especially in developing countries
The inhibitory effect of bLF on H10407 was irondependent, with iron reversing the growth inhibition (Figure 1B). We evaluated whether this effect on growth was bacteriostatic or bacteriocidal
Bacteria whose growth was significantly inhibited by bLF (OD600 0.098 vs 0.520, bLF vs control, respectively) had normal growth when put into media without bLF (OD600 0.570 vs 0.545, lactoferrin vs control, respectively)

Summary

Introduction

Diarrheal disease due to enteric infection is a major cause of death among children under five years of age, especially in developing countries. Vibrio cholerae causes the most severe disease, while enterotoxigenic Escherichia coli (ETEC) is responsible for the largest number cases. ETEC is a major cause of diarrhea in adult travelers from industrialized countries to the developing world. The major virulence factors of these bacteria are their homologous enterotoxins, cholera toxin (CT) and heat-labile enterotoxin (LT), respectively. These toxins are examples of bacterial AB5 toxins, consisting of one enzymatically active A subunit (CTA or LTA) that assemble with five B subunits (CTB or LTB) which are responsible for the toxins’ binding properties [1]

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