Recombinant bovine soluble CD14 reduces severity of experimental Escherichia coli mastitis in mice
Résumé
Endotoxin, or lipopolysaccharide (LPS), is responsible for pathogenesis of infections induced by Gram-negative bacteria, such as E. coli. The cellular response to LPS is modulated by interactions among LPS, LPS-binding protein (LBP) and CD14. Accumulated evidence shows that the soluble form of CD14 (sCD14) competes with membrane-bound CD14 (mCD14) for LPS and plays a pivotal role in regulating bacterial infection and septic shock caused by Gram-negative bacteria. Recombinant bovine sCD14 (rbosCD14) was produced by transfected insect sf/9 cells and its biological function was evaluated in mice. Eighty-one 8-week old BALB/cj female mice were randomly assigned to two groups, and injected intraperitoneally with either LPS (8 $\mu$g/g of body weight, $n = 41$) or LPS plus rbosCD14 (6.8 $\mu$g/g of body weight, $n = 40$). Survival rate at 24 h after injection for mice injected with either LPS or LPS plus rbosCD14 was 30 and 72%, respectively ($P < 0.01$). At 48 h survival rate was 7 and 37%, respectively ($P < 0.01$). To investigate the protective effect of rbosCD14 on experimentally induced mastitis in mice, two abdominal contralateral mammary glands of 7 lactating BALB/cj mice were injected through the teat canal with 10-20 colony-forming units (CFU) of Escherichia coli. One gland simultaneously received rbosCD14 (6 $\mu$g) and the other saline. At 24 h after challenge, glands that received rbosCD14 had less swelling and hemorrhaging, significantly lower bacterial counts ($P < 0.05$) and lower concentrations of TNF-$\alpha$ ($P < 0.05$). Results indicate that rbosCD14 is biologically functional and reduces mortality in mice from endotoxin shock and severity of intramammary infection by E. coli.
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