Recombinant Soluble CD14 Reduces Severity of Intramammary Infection byEscherichia coli

Abstract

The interaction among gram-negative bacteria, the innate immune system, and soluble CD14 (sCD14) has not been well documented. The effect of recombinant bovine sCD14 (rbosCD14) on milk somatic cell count (SCC), bacterial clearance, and cytokine production was investigated by using a bovine intramammary Escherichia coli infection model. We first determined whether rbosCD14 would increase the SCC during a lipopolysaccharide (LPS) challenge. Three quarters of each of six healthy lactating cows were injected with either 0.3 g of LPS, 0.3 g of LPS plus 100 g of rbosCD14, or saline. In comparison with quarters injected with LPS alone, the SCC was twofold higher (P < 0.05) in quarters injected with LPS plus rbosCD14 after the challenge. We therefore hypothesized that when E. coli bacteria invade the mammary gland, sCD14 in milk would interact with LPS and rapidly recruit neutrophils from the blood to eliminate the bacteria before establishment of infection. To test this hypothesis, two quarters of each of nine healthy cows were challenged with either 50 CFU of E. coli plus saline or 50 CFU of E. coli plus 100 g of rbosCD14. Quarters challenged with E. coli plus rbosCD14 had a more rapid recruitment of neutrophils, which was accompanied by a faster clearance of bacteria, lower concentrations of tumor necrosis factor alpha and interleukin-8 in milk, and milder clinical symptoms, than challenged quarters injected with saline. Results indicate that increasing the concentration of sCD14 in milk may be a potential strategy with which to prevent or reduce the severity of infection by coliform bacteria.

Morphometric analysis of proinflammatory cytokines in mammary glands of sows suggests an association between clinical mastitis and local production of IL-1beta, IL-6 and TNF-alpha

“…Possibly, in these sows there may be abundant and regulated release of anti-inflammatory mediators [40,53], limiting the production of the inflammatory cytokines. However, in accordance with our results, previous studies in cows have shown a significant increase in the proinflammatory cytokines at the level of both mRNA [33,37] and protein [6,11,26,32,45,48,54] in either mammary tissues or milk collected from the infected glands following intramammary inoculation with E. coli. The results here indicate that the development of clinical symptoms of coliform mastitis in the sow is associated with a locally increased proinflammatory cytokine production in response to intramammary E. coli infection.…”

Serum amyloid A and TNF? in serum and milk during experimental endotoxin mastitis

“…LPS stimulates mammary monocytes and macrophages to produce pro-inflammatory cytokines such as tumor necrosis factor α (TNFα) and interleukins 1, 6 and 8 (IL-1, IL-6, IL-8) [15,32]. These in turn act both locally and systemically, attracting polymorphonuclear neutrophils (PMN) from the 652 T. Lehtolainen et al circulation to the infection site and inducing the production of acute phase proteins (APP) in the liver.…”

“…by possibly inducing the production of IL-1, IL-6 and IL-8 [22,33]. TNFα is not a potential chemoattractant but can prime neutrophils to express adhesion molecules and thus support PMN migration [15]. The cytokine IL-8 is a potent chemoattractant for neutrophils and can be released without TNFα at the early stages of LPS-induced inflammation [15,23].…”

“…TNFα is not a potential chemoattractant but can prime neutrophils to express adhesion molecules and thus support PMN migration [15]. The cytokine IL-8 is a potent chemoattractant for neutrophils and can be released without TNFα at the early stages of LPS-induced inflammation [15,23]. On the contrary, at a later stage of inflammation the effect of TNFα may turn deleterious to the host if the production of TNFα increases to high levels [15].…”

“…The cytokine IL-8 is a potent chemoattractant for neutrophils and can be released without TNFα at the early stages of LPS-induced inflammation [15,23]. On the contrary, at a later stage of inflammation the effect of TNFα may turn deleterious to the host if the production of TNFα increases to high levels [15]. Several authors have found correlations between the severity of response and concentrations of TNFα in the blood or milk [3,8,9,20]; in other studies, no direct correlation has been seen [10,19].…”