Modun Belinda J, Cockayne Alan, Finch Roger, Williams Paul
2 Institute of Infections and Immunity University of Nottingham, University Hospital, Nottingham NG7 2UH, UK.
1 Department of Pharmaceutical Sciences, University of Nottingham, University Park, Nottingham NG7 2RD, UK.
Microbiology (Reading). 1998 Apr;144 ( Pt 4):1005-1012. doi: 10.1099/00221287-144-4-1005.
Staphylococci express a 42 kDa cell-wall-associated protein which functions as a receptor for the mammalian iron-binding glycoprotein transferrin. To determine whether this transferrin-binding protein (TBP) is expressed during infection, Staphylococcus aureus and Staphylococcus epidermidis were grown in vivo in chambers implanted intraperitoneally in rats. SDS-PAGE and Western blotting of cell wall proteins prepared from staphylococci recovered directly from the chambers revealed the presence of both the TBP and bacterial-surface-associated rat transferrin. To obtain evidence for the in vivo expression of the staphylococcal TBPs in humans, sera and human peritoneal dialysate (HPD) from non-infected patients undergoing continuous ambulatory peritoneal dialysis (CAPD) and sera from healthy human volunteers were screened for anti-TBP antibodies. Western immunoblots revealed that three out of ten samples from the latter group, seven out of ten HPD samples and ten of ten CAPD patient serum samples contained antibodies to the TBP of both S. aureus and S. epidermidis. To gain further insights into the appearance of TBP antibodies, HPD samples were collected over time from CAPD patients whose HPD samples taken immediately after catheter insertion lacked anti-TBP antibodies. In two of these patients, each of whom experienced an episode of peritonitis due to S. epidermidis or Staphylococcus hominis, antibodies to the TBP appeared in the HPD collected immediately post-infection. To determine whether such TBP antibodies were capable of blocking interactions between transferrin and its staphylococcal receptor, HPD immunoglobulin fractions were purified using protein A-Sepharose beads. In competition assays, these immunoglobulins blocked the binding of 125I-labelled transferrin both to whole bacteria and to the isolated 42 kDa TBPs of S. aureus and S. epidermidis. These provide evidence to show that staphylococcal TBPs are expressed in vivo during infection.
葡萄球菌表达一种42 kDa的细胞壁相关蛋白，该蛋白作为哺乳动物铁结合糖蛋白转铁蛋白的受体发挥作用。为了确定这种转铁蛋白结合蛋白（TBP）在感染期间是否表达，将金黄色葡萄球菌和表皮葡萄球菌在植入大鼠腹腔的小室中进行体内培养。对从小室中直接回收的葡萄球菌制备的细胞壁蛋白进行SDS-PAGE和蛋白质印迹分析，结果显示同时存在TBP和细菌表面相关的大鼠转铁蛋白。为了获得葡萄球菌TBP在人体内体内表达的证据，对接受持续性非卧床腹膜透析（CAPD）的未感染患者的血清和人腹膜透析液（HPD）以及健康人类志愿者的血清进行了抗TBP抗体筛查。蛋白质印迹免疫分析显示，后一组的十个样本中有三个、十个HPD样本中有七个以及十个CAPD患者血清样本中有十个含有针对金黄色葡萄球菌和表皮葡萄球菌TBP的抗体。为了进一步了解TBP抗体的出现情况，从导管插入后立即采集的HPD样本中缺乏抗TBP抗体的CAPD患者随时间收集HPD样本。在其中两名患者中，每人都经历了一次由表皮葡萄球菌或人葡萄球菌引起的腹膜炎发作，感染后立即收集的HPD中出现了针对TBP的抗体。为了确定这种TBP抗体是否能够阻断转铁蛋白与其葡萄球菌受体之间的相互作用，使用蛋白A-琼脂糖珠纯化HPD免疫球蛋白组分。在竞争试验中，这些免疫球蛋白阻断了125I标记的转铁蛋白与全菌以及金黄色葡萄球菌和表皮葡萄球菌分离的42 kDa TBP的结合。这些结果提供了证据表明葡萄球菌TBP在感染期间在体内表达。
