ABSTRACT
The 56-kilodalton protein genes of Orientia tsutsugamushi TA678, TA686, TA716, TA763 strains were amplified by PCR. The amplified products were sequenced and cloned into pIH821 vector. The recombinant proteins were expressed in Escherichia coli as fusion proteins with maltose binding protein. The recombinant proteins were purified and used for the sensitization of sheep RBCs and the reactivity of the recombinant 56-kDa proteins of Orientia tsutsugamushi TA 678, TA686, TA716 strains were analyzed with 40 sera from scrub typhus patients in Korea, 40 sera from scrub typhus in Thailand, Malaysia and Philippines. The 56-kDa protein coding DNA sequence of Orientia tsutsugamushi TA678, TA686, TA716 show 70 to 88% homology with other known strains and four variable regions are also observed. 39 of 40 sera from scrub typhus patients in Korea showed the strongest reactivity to the recombinant protein of Boryong strain and one sera showed the strongest reactivity to the recombinant protein of Gilliam strain. 14 of 40 sera from patients in Thailand, Malaysia and Philippines showed the strongest reactivity to the recombinant protein of TA686 strain and 12 sera showed the strongest reactivity to the recombinant protein of TA716 strain. No serum from patients in Thailand, Malaysia and Philippines showed the strongest reactivity to the recombinant protein of Boryong strain.