The protective effects of lactoferrin feeding against endotoxin lethal shock in germfree piglets

Abstract

The unique germfree, colostrum-deprived, immunologically "virgin" piglet model was used to evaluate the ability of lactoferrin (LF) to protect against lethal shock induced by intravenously administered endotoxin. Piglets were fed LF or bovine serum albumin (BSA) prior to challenge with intravenous Escherichia coli lipopolysaccharide (LPS), and temperature, clinical symptoms, and mortality were tracked for 48 h following LPS administration. Prefeeding with LF resulted in a significant decrease in piglet mortality compared to feeding with BSA (16.7 versus 73.7% mortality, P < 0.001). Protection against the LPS challenge by LF was also correlated with both resistance to induction of hypothermia by endotoxin and an overall increase in wellness, as quantified by a toxicity score developed for these studies. In vitro studies using a flow cytometric assay system demonstrated that LPS binding to porcine monocytes was inhibited by LF in a dose-dependent fashion, suggesting that the mechanism of LF action in vivo may be inhibition of LPS binding to monocytes/macrophages and, in turn, prevention of induction of monocyte/macrophage-derived inflammatory-toxic cytokines.

FIG. 1

Effect of LF on the rectal temperatures (A, B, C, D) and toxicity scores (a, b, c, d) of GF piglets injected i.v. with LPS. LF or BSA (2,000 mg) was fed by gastric tube every 8 h for 1 day, followed by i.v. injection of LPS at 750 μg/kg, and GF piglets were maintained on 20 mg of LF or BSA per ml of Nursoy diet, and then rectal temperatures and toxicity scores were measured at 0, 1, 2, 3, 6, 9, 12, 20, 24, 28, 32, 36, 44, and 48 h after injection. †, death.

FIG. 2

Effect of LF on rectal temperatures (A, B, C, D) and toxicity scores (a, b, c, d) of GF piglets injected i.v. with LPS. LF or BSA (2,000 mg) was fed by gastric tube every 8 h for 1 day, followed by i.v. injection of 750 or 850 μg of LPS per kg, and GF piglets were maintained on 20 mg of LF or BSA per ml of Nursoy diet, and then rectal temperatures and toxicity scores were measured at 0, 1, 2, 3, 6, 9, 12, 20, 24, 28, 32, 36, 44, and 48 h after injection. †, death.

FIG. 3

Effect of anti-CD14 MAb on LPS binding to porcine monocytes. Percent binding of LPS to porcine monocytes without the anti-CD14 MAb (open symbols) and with the anti-CD14 MAb (2 μg) (closed symbols) is shown. SPF, specific pathogen free.

FIG. 4

Percent inhibition of LPS binding to porcine monocytes by LF. Porcine PBMs (5 × 10⁶/ml) were incubated with various concentrations of LF, and then LPS-FITC binding was analyzed by flow cytometer, and percent inhibition was calculated as described in Materials and Methods. SPF, specific pathogen free.