Abstract
This study investigated the effects of repeated oronasal treatment with lipopolysaccharide (LPS) on the humoral immune responses in saliva, vaginal mucus, and the plasma markers of the acute phase response in periparturient dairy cows. One hundred pregnant Holstein cows were administered either 3 increasing doses of LPS (n = 50) as follows: 1) 0.01 µg/kg body weight (BW) on d −28, 2) 0.05 µg/kg BW on d −25, and −21, and 3) 0.1 µg/kg BW on d −18, and −14, or sterile saline solution (controls; n = 50) oronasally for 3 consecutive wk starting at 28 d before parturition. Intensive sampling was conducted on thirty cows (n = 15/group). Multiple saliva, vaginal mucus and blood samples were collected around parturition and analyzed for total immunoglobulin-(Ig)A, plasma serum amyloid A (SAA), lipopolysaccharide-binding protein (LBP), anti-LPS IgA, IgG, IgM, tumour necrosis factor(TNF)-α, and interleukin(IL)-1. Results regarding total secretory IgA (sIgA) antibodies showed greater concentrations in the saliva and an overall tendency for higher total sIgA in the vaginal mucus of the LPS-treated cows. Treatment had no effect on plasma sIgA, IgG, IgM anti-LPS antibodies, haptoglobin, SAA, LBP, TNF-α, and IL-1. Treatments by time interactions were observed for SAA and IL-1 with lowered concentrations of both variables in the plasma of LPS-treated cows after parturition. Overall, repeated oronasal LPS treatment clearly enhanced total sIgA antibodies in the saliva, stimulated their production in vaginal mucus shortly before calving, and lowered plasma IL-1 around parturition, but showed limited effects on markers of the acute phase response in the plasma in dairy cows around parturition.
Highlights
The period around parturition is often characterized by major biochemical and immunological alterations in dairy cows, which increase the odds for health problems postpartum [1,2,3]
Research has demonstrated that the cell-free LPS in the rumen fluid translocates through rumen and colon tissues and that it is found in the systemic circulation, triggering activation of an acute phase response (APR) [6,7,8,9]
The study conducted by Bryn et al [5] demonstrated that LPS induces monocytes to produce prostaglandin E2 (PGE2) that directly suppress T-cell functions and adaptive immune responses, suggesting a role for LPS in the immunosuppression observed during transition period
Summary
The period around parturition is often characterized by major biochemical and immunological alterations in dairy cows, which increase the odds for health problems postpartum [1,2,3]. The exact mechanism(s) behind the lowered immune competence in periparturient dairy cows is not completely understood; the endocrinological changes and the increased metabolic stress around parturition are believed to play a role [1, 2, 4]. The presence of lipopolysaccharide (LPS), a cell-wall component of Gram-negative bacteria (GNB), has been suggested as a factor playing a role in immunosuppression of transition dairy cows [5]. The study conducted by Bryn et al [5] demonstrated that LPS induces monocytes to produce prostaglandin E2 (PGE2) that directly suppress T-cell functions and adaptive immune responses, suggesting a role for LPS in the immunosuppression observed during transition period. Free LPS in the uterine lumen during early postpartum induces PGE2 secretion by the uterine endometrium [10,11,12]
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