Anti-invasive activity of bovine colostrum and whey proteins against Salmonella Typhimurium

Bovine colostrum, non-inmunoglobulin G (non-IgG) fraction, obtained after passing colostral whey through a protein G-agarose affinity chromatography column, and selected whey proteins (alpha-lactalbumin, beta-lactoglobulin, lactoferrin and lactoperoxidase) were tested for anti-invasive activity against Salmonella Typhimurium SL 1344 invasion of HeLa cells.; Bovine colostrum and non-IgG fraction decreased S. Typhimurium invasion of cultured HeLa cells by 98 and 66% respectively. In an attempt to find the anti-invasive compound(s) in non-IgG fraction of bovine colostral whey, lactoferrin, alpha-lactalbumin, beta-lactoglobulin and lactoperoxidase were tested for their effect on HeLa cell invasion by S. Typhimurium. All tested whey proteins except lactoperoxidase, at concentrations up to 10 mg mL-1, significantly (p < 0.05) reduced invasion. There was a significant linear relation ( p < 0.05) between whey protein concentration and anti-invasive activity when protein concentration ranged between 0 and 8 mg mL-1 . Anti-invasive activity of alpha-lactalbumin and beta-lactoglobulin at the highest concentration used (15 mg mL-1) was not significantly (p > 0.05) different from anti-invasive activity at 8 mg mL-1. Lactoferrin at 15 mg mL-1 had significantly higher anti-invasive activity than at 8 mg mL -1. Lactoferrin showed the highest anti-invasive activity (78%) of the three whey proteins at 15 mg mL-1. Whey proteins, at the concentrations used, were not cytotoxic to HeLa cells.; Random Centroid Optimization program was used in an attempt to formulate a mixture of lactoferrin, alpha-lactalbumin and beta-lactoglobulin with improved anti-invasive activity. In comparison to individual proteins, all mixtures had lower anti-invasive activity per mg protein suggesting antagonistic interactions among the tested whey proteins. Tested whey proteins were not bactericidal nor bacteriostatic at 10 and 15 mg mL-1 and did not promote aggregation of S. Typhimurium. Preincubation of HeLa cells with selected whey proteins and including the washing step before challenging with S. Typhimurium almost eliminated anti-invasive activity for beta-lactoglobulin and reduced the anti-invasive activity of alpha-lactalbumin and lactoferrin by 40 and 50% respectively. Preincubation of S. Typhimurium with the tested whey proteins prior to invasion also resulted in reduced anti-invasive activity. Results suggest the potential of lactoferrin, alpha-lactalbumin and beta-lactoglobulin for being considered as bioactive ingredients in food formulation.