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UBC Theses and Dissertations

Anti-invasive activity of Bovine colostrum and whey proteins against Salmonella typhimurium Noei, Azita Madadi


Bovine colostrum, non-immunoglobulin G (non-IgG) fraction, obtained after passing colostral whey through a protein G-agarose affinity chromatography column, and selected whey proteins (a-lactalbumin, P-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, a-lactalbumin, Blactoglobulin 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 cclactalbumin and P-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, a-lactalbumin and P-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 (3-lactoglobulin and reduced the anti-invasive activity of a-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, alactalbumin and P-lactoglobulin for being considered as bioactive ingredients in food formulation.

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