Antigenic and genotypic variation in Orientia tsutsugamushi and its relation to virulence.

恙虫病恙虫病恙虫病病原菌具有多种抗原变异和对小鼠的不同毒力。为了明确该药物的多样性及其与致病性的关系，对日本和台湾新分离的许多菌株进行了血清分型和基因分型，检测了15种类型特异性单克隆抗体的反应性及其56KDa型特异性抗原蛋白基因的PCR-RFLP图谱。结果表明，日本34株分离株可分为Gilliam、Karp、Kawasaki和Kuroki 4种亚型，但每种亚型的分离株又可分别分为Gilliam、Karp、Kawasaki和Kuroki 3、3、4和2种亚型。台湾10株分离株可分为6个Karp亚型和1个Gilliam型。此外，所有台湾分离株均可与日本分离株区分。这些结果表明，该病原菌分离株在型和亚型水平上存在许多变异。在对小鼠的致病性方面，Gilliam型和Karp型分离株大多表现出高毒力，Kawasaki型和Kuroki型分离株均表现出无毒性，提示其致病性与其血清型之间存在一定的关系。在进行这些研究的过程中，我们成功克隆并测序了该微生物的16SrRNA基因。直到最近，这种微生物一直被认为是立克次体属的成员，并被指定为恙虫病立克次体。然而，我们之前对该微生物的许多研究和本研究的16SrRNA基因同源性分析结果表明，该微生物应该从立克次体属中分离出来。因此，我们建议将该微生物分类为东方菌属（Orientia gen.nov）。这一建议被《国际系统细菌学杂志》接受。

Various antigenic variants and diversity of virulence to mice are recognized among the pathogenic agents of scrub typhus, Orientiatsutsugamushi. To clarify the variety of this agent, and its relation to pathogenicity, sero-and geno-typing of many newly isolated strains in Japan and Taiwan was performed by testing reactivity of the isolates with 15 type-specific monoclonal antibodies and PCR-RFLP patterns of their 56KDa type-specific antigenic protein gene. The results obtained indicated that 34 isolates in Japan were classified into 4types of Gilliam, Karp, Kawasaki and Kuroki, but the isolates of each type were further divided into 3,3,4, and 2 subtypes of Gilliam, Karp, Kawasaki and Kuroki, respectively. Ten isolates in Taiwan were clasified into 6 subtypes of Karp and 1 Gilliam type. Additionally, all Taiwan isolates could be distinguished from Japanese isolated. These results indicated that many variants in type and subtype levels exist among the isolates of this pathogenic agent. On pathogenicity to mice, most isolates off Gilliam and Karp types showed high virulence but all isolates of Kawasaki and Kuroki types were avirulent, suggesting the existence of a certain relationship between the pathogenicity and their serotypes.During the cause of these studies, we succeeded the cloning and sequencing of 16SrRNA gene of this microbe. Till quite recently, this microbe has been considered as a member of the genus Rickettsia and designated as Rickettsia tsutsugamushi. However, our many previous studies on this microorganism and the results of 16SrRNA gene homology analysis in the present study indicated that this microbe should be separated from the genus Rickettsia. Therefore we proposed to classify this microbe into Orientia gen.nov., as Orientia tsutsugamushi comb.nov.This proposal was accepted in the International Journal of Systematic Bacteriology.