Günther Juliane, Czabanska Anna, Bauer Isabel, Leigh James A, Holst Otto, Seyfert Hans-Martin
Institute for Genome Biology, Leibniz Institute for Farm Animal Biology (FBN), Wilhelm-Stahl-Allee 2, 18196, Dummerstorf, Germany.
Division of Structural Biochemistry, Research Center Borstel, Leibniz-Center for Medicine and Biosciences, Parkallee 1-40, 23845, Borstel, Germany.
Vet Res. 2016 Jan 7;47:13. doi: 10.1186/s13567-015-0287-8.
Streptococcus uberis is frequently isolated from the mammary gland of dairy cattle. Infection with some strains can induce mild subclinical inflammation whilst others induce severe inflammation and clinical mastitis. We compared here the inflammatory response of primary cultures of bovine mammary epithelial cells (pbMEC) towards S. uberis strains collected from clinical or subclinical cases (seven strains each) of mastitis with the strong response elicited by Escherichia coli. Neither heat inactivated nor live S. uberis induced the expression of 10 key immune genes (including TNF, IL1B, IL6). The widely used virulent strain 0140J and the avirulent strain, EF20 elicited similar responses; as did mutants defective in capsule (hasA) or biofilm formation (sub0538 and sub0539). Streptococcus uberis failed to activate NF-κB in pbMEC or TLR2 in HEK293 cells, indicating that S. uberis particles did not induce any TLR-signaling in MEC. However, preparations of lipoteichoic acid (LTA) from two strains strongly induced immune gene expression and activated NF-κB in pbMEC, without the involvement of TLR2. The immune-stimulatory LTA must be arranged in the intact S. uberis such that it is unrecognizable by the relevant pathogen receptors of the MEC. The absence of immune recognition is specific for MEC, since the same S. uberis preparations strongly induced immune gene expression and NF-κB activity in the murine macrophage model cell RAW264.7. Hence, the sluggish immune response of MEC and not of professional immune cells to this pathogen may aid establishment of the often encountered belated and subclinical phenotype of S. uberis mastitis.
乳房链球菌经常从奶牛的乳腺中分离出来。某些菌株感染可诱发轻度亚临床炎症，而其他菌株则诱发严重炎症和临床乳腺炎。我们在此比较了牛乳腺上皮细胞（pbMEC）原代培养物对从乳腺炎临床或亚临床病例（各7株）中分离的乳房链球菌菌株的炎症反应，以及大肠杆菌引发的强烈反应。热灭活或活的乳房链球菌均未诱导10个关键免疫基因（包括TNF、IL1B、IL6）的表达。广泛使用的强毒株0140J和无毒株EF20引发了相似的反应；缺乏荚膜（hasA）或生物膜形成缺陷的突变体（sub0538和sub0539）也是如此。乳房链球菌未能激活pbMEC中的NF-κB或HEK293细胞中的TLR2，这表明乳房链球菌颗粒未在MEC中诱导任何TLR信号传导。然而，来自两株菌株的脂磷壁酸（LTA）制剂在pbMEC中强烈诱导免疫基因表达并激活NF-κB，且不涉及TLR2。免疫刺激LTA在完整的乳房链球菌中必定是以某种方式排列，使其无法被MEC的相关病原体受体识别。免疫识别的缺失对MEC具有特异性，因为相同的乳房链球菌制剂在小鼠巨噬细胞模型细胞RAW264.7中强烈诱导免疫基因表达和NF-κB活性。因此，MEC而非专业免疫细胞对这种病原体的免疫反应迟缓，可能有助于乳房链球菌乳腺炎常见的迟发性和亚临床表型的形成。
