Liu Yongxia, Chen Wei, Ali Tariq, Alkasir Rashad, Yin Jinhua, Liu Gang, Han Bo
Department of Clinical Medicine, College of Veterinary Medicine, China Agricultural University, Yuan Ming Yuan West Road No. 2, Haidian District, Beijing 100193, China.
Toxins (Basel). 2014 Dec 19;6(12):3552-67. doi: 10.3390/toxins6123552.
Staphylococcal enterotoxins (SEs) are powerful superantigenic toxins produced by Staphylococcus aureus (S. aureus). They can cause food poisoning and toxic shock. However, their impact on bovine mammary epithelial cells (bMECs) is still unknown. In this study, the distribution of SE genes was evaluated in 116 S. aureus isolates from bovine mastitis, and the most prevalent genes were seh (36.2%), followed by sei (12.1%), seg (11.2%), ser (4.3%), sec (3.4%), sea (2.6%) and sed (1.7%). To better understand the effect of staphylococcal enterotoxin H (SEH) on bMECs, the seh gene was cloned and inserted into the prokaryotic expression vector, pET28a, and transformed into Escherichia coli BL21 (DE3). The recombinant staphylococcal enterotoxin H (rSEH) was expressed and purified as soluble protein. Bioactivity analysis showed that rSEH possessed the activity of stimulating lymphocytes proliferation. The XTT assay showed that 100 μg/mL of rSEH produced the cytotoxic effect on bMECs, and fluorescence microscopy and flow cytometry analysis revealed that a certain dose of rSEH is effective at inducing bMECs apoptosis in vitro. This indicates that SEs can directly lead to cellular apoptosis of bMECs in bovine mastitis associated with S. aureus.
葡萄球菌肠毒素（SEs）是由金黄色葡萄球菌（S. aureus）产生的强效超抗原毒素。它们可导致食物中毒和中毒性休克。然而，它们对牛乳腺上皮细胞（bMECs）的影响仍然未知。在本研究中，评估了116株来自牛乳腺炎的金黄色葡萄球菌分离株中SE基因的分布情况，最常见的基因是seh（36.2%），其次是sei（12.1%）、seg（11.2%）、ser（4.3%）、sec（3.4%）、sea（2.6%）和sed（1.7%）。为了更好地了解葡萄球菌肠毒素H（SEH）对bMECs的影响，将seh基因克隆并插入原核表达载体pET28a中，然后转化到大肠杆菌BL21（DE3）中。重组葡萄球菌肠毒素H（rSEH）得以表达并纯化出可溶性蛋白。生物活性分析表明，rSEH具有刺激淋巴细胞增殖的活性。XTT检测表明，100μg/mL的rSEH对bMECs产生细胞毒性作用，荧光显微镜和流式细胞术分析显示，一定剂量的rSEH在体外可有效诱导bMECs凋亡。这表明SEs可直接导致与金黄色葡萄球菌相关的牛乳腺炎中bMECs的细胞凋亡。
