Bendel C M, Hostetter M K
Department of Pediatrics, University of Minnesota, Minneapolis 55455.
J Clin Invest. 1993 Oct;92(4):1840-9. doi: 10.1172/JCI116775.
The yeast Candida albicans is the leading cause of disseminated fungal infection in neonates, immunocompromised hosts, diabetics, and postoperative patients; Candida tropicalis is the second most frequent isolate. Because the integrin analogue in C. albicans shares antigenic, structural, and functional homologies with the beta 2-integrin subunits alpha M and alpha X, we investigated the role of integrin analogues in epithelial adhesion of C. albicans and C. tropicalis. On flow cytometry with the monoclonal antibody (mAb) OKM1, surface fluorescence was highest for C. albicans and significantly reduced for C. tropicalis (P < 0.001). However, adhesion to the human epithelial cell line HeLa S3 did not differ for these two candidal species: specific adhesion was highest for C. albicans at 44.0 +/- 1.8%, and only slightly lower for C. tropicalis at 38.8 +/- 3.6% (P = NS). The disparity between expression of the integrin analogue and epithelial adhesion suggested distinct mechanisms for this process in C. albicans versus C. tropicalis. Preincubation of C. albicans with anti-alpha M mAbs, with purified iC3b (the RGD ligand for the integrin analogue), or with 9-15-mer RGD peptides from iC3b all inhibited epithelial adhesion significantly (P < 0.001-0.04). Purified fibronectin or fibronectin-RGD peptides failed to block C. albicans adhesion. In contrast, epithelial adhesion of C. tropicalis was significantly inhibited by purified fibronectin and its RGD peptides (P < or = 0.021), but not by iC3b nor the iC3b-RGD peptides. Both iC3b and fibronectin were identified on the surface of epithelial cells after growth in serum-free medium. A polyclonal antibody to C3 inhibited C. albicans adhesion while a control antibody to fibronectin was ineffective; the converse was true for C. tropicalis. These results indicate that the pathogenic yeasts C. albicans and C. tropicalis recognize distinct RGD ligands present at the surface of the epithelial cell and that these interactions can be differentially inhibited by defined RGD peptides containing appropriate flanking sequences.
白色念珠菌是新生儿、免疫功能低下宿主、糖尿病患者及术后患者播散性真菌感染的主要病因；热带念珠菌是第二常见的分离菌株。由于白色念珠菌中的整合素类似物与β2整合素亚基αM和αX具有抗原、结构和功能同源性，我们研究了整合素类似物在白色念珠菌和热带念珠菌上皮黏附中的作用。在用单克隆抗体（mAb）OKM1进行的流式细胞术中，白色念珠菌的表面荧光最高，而热带念珠菌的表面荧光显著降低（P < 0.001）。然而，这两种念珠菌对人上皮细胞系HeLa S3的黏附并无差异：白色念珠菌的特异性黏附最高，为44.0 +/- 1.8%，热带念珠菌仅略低，为38.8 +/- 3.6%（P = 无显著性差异）。整合素类似物的表达与上皮黏附之间的差异表明，白色念珠菌与热带念珠菌在此过程中存在不同机制。用抗αM单克隆抗体、纯化的iC3b（整合素类似物的RGD配体）或来自iC3b的9 - 15聚体RGD肽预孵育白色念珠菌，均显著抑制上皮黏附（P < 0.001 - 0.04）。纯化的纤连蛋白或纤连蛋白 - RGD肽未能阻断白色念珠菌的黏附。相反，纯化的纤连蛋白及其RGD肽显著抑制热带念珠菌的上皮黏附（P ≤ 0.021），但iC3b及其iC3b - RGD肽则无此作用。在无血清培养基中生长后，上皮细胞表面均鉴定出iC3b和纤连蛋白。抗C3多克隆抗体抑制白色念珠菌的黏附，而抗纤连蛋白对照抗体则无效；热带念珠菌的情况则相反。这些结果表明，致病性酵母白色念珠菌和热带念珠菌识别上皮细胞表面存在的不同RGD配体，并且这些相互作用可被含有适当侧翼序列的特定RGD肽差异性抑制。
