Fernandez-Miyakawa Mariano E, Fisher Derek J, Poon Rachael, Sayeed Sameera, Adams Vicki, Rood Julian I, McClane Bruce A, Uzal Francisco A
California Animal Health and Food Safety Laboratory--San Bernardino Branch, University of California-Davis, 105 West Central Avenue, San Bernardino, CA 92408, USA.
Infect Immun. 2007 Mar;75(3):1443-52. doi: 10.1128/IAI.01672-06. Epub 2007 Jan 8.
Clostridium perfringens is capable of producing up to 15 toxins, including alpha-toxin (CPA), beta-toxin (CPB), epsilon-toxin (ETX), enterotoxin, beta2-toxin (CPB2), and perfringolysin O. Type B isolates, which must produce CPA, CPB, and ETX, are associated with animal illnesses characterized by sudden death or acute neurological signs, with or without intestinal damage. Type B pathogenesis in ruminants is poorly understood, with some animals showing lesions and clinical signs similar to those caused by either type C or type D infections. It is unknown whether host or environmental conditions are dominant for determining the outcome of type B disease or if disease outcomes are determined by variable characteristics of type B isolates. To help clarify this issue, 19 type B isolates were evaluated for toxin production during late-log-phase growth via quantitative Western blotting and by biological activity assays. Most type B isolates produced CPB levels similar to those produced by type C isolates in vitro and have the potential to produce genotype C-like disease. The lethality of type B isolate supernatants administered intravenously to mice was evaluated with or without prior trypsin treatment, and monoclonal antibody neutralization studies also were performed. Correlation analyses comparing toxin levels in type B supernatants versus lethality and neutralization studies both found that the main contributor to lethality without pretreatment with trypsin was CPB, whereas neutralization studies indicated that CPB and ETX were both important after trypsin pretreatment. At least part of the CPB produced by type B isolates remained active after trypsin treatment. However, the overall lethalities of most supernatants were lower after trypsin pretreatment. Also, there was a significant association between ETX, CPB2, and CPA production in vitro among type B isolates. However, our results suggest that both CPB and ETX are likely the most important contributors to the pathogenesis of C. perfringens type B infections in domestic animals.
产气荚膜梭菌能够产生多达15种毒素，包括α毒素（CPA）、β毒素（CPB）、ε毒素（ETX）、肠毒素、β2毒素（CPB2）和产气荚膜梭菌溶血素O。B型菌株必须产生CPA、CPB和ETX，与以猝死或急性神经症状为特征的动物疾病相关，伴有或不伴有肠道损伤。反刍动物中B型致病机制了解甚少，一些动物表现出与C型或D型感染引起的病变和临床症状相似。尚不清楚宿主或环境条件在决定B型疾病结局方面是否占主导地位，或者疾病结局是否由B型菌株的可变特征决定。为了帮助阐明这个问题，通过定量蛋白质免疫印迹法和生物活性测定法，对19株B型菌株在对数生长后期的毒素产生情况进行了评估。大多数B型菌株产生的CPB水平与体外C型菌株产生的水平相似，并且有可能产生基因型C样疾病。对静脉注射给小鼠的B型菌株上清液进行了有或没有预先胰蛋白酶处理的致死率评估，并且还进行了单克隆抗体中和研究。比较B型上清液中的毒素水平与致死率和中和研究的相关性分析均发现，未经胰蛋白酶预处理时致死率的主要贡献者是CPB，而中和研究表明胰蛋白酶预处理后CPB和ETX都很重要。B型菌株产生的至少部分CPB在胰蛋白酶处理后仍保持活性。然而，胰蛋白酶预处理后大多数上清液的总体致死率较低。此外，B型菌株体外ETX、CPB2和CPA产生之间存在显著关联。然而，我们的结果表明，CPB和ETX可能都是家畜产气荚膜梭菌B型感染发病机制的最重要贡献者。
