Lactoferrin increases both resistance to Salmonella typhimurium infection and the production of antibodies in mice

Lactoferrin (Lf) is a multifunctional iron-binding glycoprotein with antibacterial and immunomodulatory activities. The antibacterial influence of orally administered bovine Lf (bLf) against murine infection caused by Salmonella typhimurium (S. typhimurium) has scarcely been explored. In the current study, Balb/c mice were treated orally for 7 days with either 5 or 100 mg of bovine lactoferrin (bLf). On day 7 of treatment, mice were intragastrically infected with a lethal or sublethal dose of colony forming units (CFU) of S. typhimurium. During treatment with bLf, feces from mice sublethally infected were harvested daily to prepare fecal suspensions, which were serially diluted and plated onto Salmonella Shigella agar to estimate CFU/g of feces. After sacrificing the animals on day 7, 14 or 21 post-infection, samples of intestinal fluid, Peyer's patches (PP), liver and spleen were collected to count the number of CFU by plate dilution. Intestinal secretions were also employed, along with serum samples, to evaluate total IgA, IgG and IgM antibodies, and those against Salmonella surface proteins and bLf by ELISA assay. In lethally infected mice both bLf doses decreased mortality. In sublethally infected mice, both bLf doses decreased bacterial shedding in feces and intestinal fluid, and also reduced bacterial colonization at PP and bacterial translocation in the liver and spleen. Levels of total and those IgG and IgM in serum and IgA in intestinal secretions against Salmonella surface proteins and bLf were enhanced with both doses of bLf. These findings suggest that the effect of bLf against the infection by S. typhimurium in mice may be the result of an antimicrobial activity linked with its modulatory effect on immunocompetent cells (from intestinal and peripheral organs) involved in antibody production.