Dassanayake Rohana P, Liu Weiguo, Davis William C, Foreyt William J, Srikumaran Subramaniam
Department of Microbiology and Pathology, Washington State University, Pullman, WA 99164-7040, USA.
J Wildl Dis. 2008 Jul;44(3):743-7. doi: 10.7589/0090-3558-44.3.743.
Mannheimia haemolytica is an important cause of pneumonia in bighorn sheep (BHS; Ovis canadensis). Leukotoxin (Lkt), the primary virulence determinant of M. haemolytica, induces cytolysis of all subsets of leukocytes. Previously, we have shown that CD18, the beta subunit of beta2-integrins, mediates Lkt-induced cytolysis. However, it is not clear whether CD18 of all three beta2-integrins, LFA-1, Mac-1, and CR4, mediates Lkt-induced cytolysis. The objective of this study was to determine whether BHS LFA-1 (CD11a/CD18) serves as a receptor for Lkt. Plasmids encoding cDNA for BHS CD11a and CD18 were cotransfected into Lkt-resistant HEK-293 cells. Flow cytometric analysis of transfectants confirmed cell surface expression of BHS LFA- 1, Lkt-LFA-1 binding and Lkt-induced intra-cellular calcium elevation. More importantly, the transfectants were efficiently lysed by Lkt in a concentration-dependent manner. Collectively, these results indicate that BHS LFA-1 serves as a functional receptor for M. haemolytica Lkt.
溶血曼氏杆菌是大角羊（BHS；加拿大盘羊）肺炎的一个重要病因。白细胞毒素（Lkt）是溶血曼氏杆菌的主要毒力决定因素，可诱导所有白细胞亚群的细胞溶解。此前，我们已经表明，β2整合素的β亚基CD18介导Lkt诱导的细胞溶解。然而，尚不清楚三种β2整合素LFA-1、Mac-1和CR4的CD18是否都介导Lkt诱导的细胞溶解。本研究的目的是确定BHS LFA-1（CD11a/CD18）是否作为Lkt的受体。将编码BHS CD11a和CD18 cDNA的质粒共转染到对Lkt耐药的HEK-293细胞中。对转染子的流式细胞术分析证实了BHS LFA-1在细胞表面的表达、Lkt-LFA-1结合以及Lkt诱导的细胞内钙升高。更重要的是，转染子被Lkt以浓度依赖的方式有效裂解。总体而言，这些结果表明BHS LFA-1作为溶血曼氏杆菌Lkt的功能性受体。
