The role of human milk secretory IgA in protecting infants from bacterial enteritis

Bovine milk derived skimmed milk powder and whey protein concentrate modulates Citrobacter rodentium shedding in the mouse intestinal tract

Skimmed milk powder (SMP) and whey protein concentrate (WPC) were manufactured from fresh milk collected from cows producing high or low Immunoglobulin (Ig) A levels in their milk. In addition commercial products were purchased for use as diluent or control treatments. A murine enteric disease model (Citrobacter rodentium) was used to assess whether delivery of selected bioactive molecules (IgA, IgG, Lactoferrin (Lf)) or formulation delivery matrix (SMP, WPC) affected faecal shedding of bacteria in C. rodentium infected mice. In trial one, faecal pellets collected from mice fed SMP containing IgA (0.007-0.35 mg/mL), IgG (0.28-0.58 mg/mL) and Lf (0.03-0.1 mg/mL) contained fewer C. rodentium (cfu) compared to control mice fed water (day 8, p < 0.04, analysis of variance (ANOVA) followed by Fisher's unprotected least significant difference (ULSD)). In trial two, WPC containing IgA (0.35-1.66 mg/mL), IgG (0.58-2.36 mg/mL) and Lf (0.02-0.45 mg/mL) did not affect C. rodentium shedding, but SMP again reduced faecal C. rodentium levels (day 12, p < 0.04, ANOVA followed by Fisher's ULSD). No C. rodentium was detected in sham phosphate-buffered saline inoculated mice. Mice fed a commercial WPC shed significantly greater numbers of C. rodentium over 4 consecutive days (Fishers ULSD test), compared to control mice fed water. These data indicate that SMP, but not WPC, modulates faecal shedding in C. rodentium-infected mice and may impact progression of C. rodentium infection independently of selected bioactive concentration. This suggests that food matrix can impact biological effects of foods.