| Summary: | 碩士 === 國防醫學院 === 微生物及免疫學研究所 === 93 === Tsutsugamushi diease, also known as Scrub typhus, is an acute infection disease caused by Orientia tsutsugamushi. Orientia tsutsugamushi is a obligate intracellular bacterium. The wild rodents are the most important reservoir keeping the larval mites (chiggers). Scrub typhus is transmitted to humans from field mice and rats through the bite of mites that live on the animals. The diagnosis of scrub typhus have been performed mainly by the methods of indirect immunofluorescent assay. However, the development of other simple and accurate diagnosic methods, such as enzyme-linked immunosorbent assay (ELISA), is still being investigated. The gene encoding the 56kD outer membrane protein of Orientia tsutsugamushi KM19-24 strain was amplified by PCR and cloned into the expression vector pET32a. The similarity of Gilliam and KM19-24 p56 gene is 99% by DNA sequence analysis. When IPTG was added, the recombinant 75kDa-p56 protein was expressed in E.coli BL21(DE3) and formed inclusion bodies. The recombinant 75kDa-p56 protein was purified by fast performance liquid chromatography (FPLC) and was used as antigen for ELISA to screen samples. The sensitivity and specificity were 100% and 85.7% as demonstrated by using the 38 human sera as sample.To analyze the cross-reactivity of different strain of O.tsutsugamushi, we used anti-O. tsutsugamushi human sera and anti-Karp p56 rabbit sera. The results showed that different strain of O. tsutsugamushi had less cross-reactivity and suggest that the KM19-24 strain 56kD protien is an suitable type-specific immunodiagnostic antigen for ELISA.
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