ABSTRACT

Objective: Porphyromonas gulae, a major periodontal pathogen in animals, possesses fimbriae that have been classified into three genotypes (A, B, C) based on the diversity of fimA genes encoding fimbrillin protein (FimA). P. gulae strains with type C fimbriae were previously shown to be more virulent than other types. In this study, we further examined the host toxicity mediated by P. gulae fimbriae by constructing recombinant FimA (rFimA) expression vectors for each genotype and raised antibodies to the purified proteins.

Methods and Results: All larvae died within 204 h following infection with P. gulae type C at the low-dose infection, whereas type A and B did not. Among fimA types, the survival rates of the larvae injected with rFimA type C were remarkably decreased, while the survival rates of the larvae injected with rFimA type A and type B were greater than 50%. Clindamycin treatment inhibited the growth of type C strains in a dose-dependent manner, resulting in an increased rate of silkworm survival. Finally, type C rFimA-specific antiserum prolonged the survival of silkworm larvae stimulated by infection with P. gulae type C strain or injection of rFimA type C protein.

Conclusion: These results suggested that type C fimbriae have high potential for enhancement of bacterial pathogenesis, and that both clindamycin and anti-type C rFimA-specific antibodies are potent inhibitors of type C fimbriae-induced toxicity. This is the first report to establish a silkworm infection model using P. gulae for toxicity assessment.

摘要

目的：卟啉gulae，在动物体内的主要牙周病原菌，拥有已分为基础上的多样性三种基因型（A，B，C）菌毛FIMA编码菌毛蛋白（FIMA）的基因。先前已证明具有C型菌毛的古拉氏疟原虫菌株比其他类型更具毒力。在这项研究中，我们通过构建每种基因型的重组FimA（rFimA）表达载体和针对纯化蛋白的抗体，进一步检查了古拉氏菌介导的宿主毒性。

方法和结果：在小剂量感染下，所有幼虫在感染C型古拉氏菌后204小时内死亡，而A和B型则没有。在fimA类型中，注射rFimA C型的幼虫的存活率显着降低，而注射rFimA A型和B型的幼虫的存活率大于50％。克林霉素治疗以剂量依赖性方式抑制C型菌株的生长，从而提高了蚕的存活率。最后，C型rFimA特异性抗血清可延长感染C. gulae C型菌株或注射rFimA C型蛋白刺激的蚕幼虫的存活。

结论：这些结果表明C型菌毛具有增强细菌发病机理的潜力，而克林霉素和抗C型rFimA特异性抗体均是C型菌毛诱导的毒性的有效抑制剂。这是第一个使用古拉氏疟原虫建立家蚕感染模型进行毒性评估的报告。