Abstract
Antigenic types of Orientia tsutsugamushi in naturally infected colonies of Leptotrombidium (L.) fletcheri, L. arenicola, and L. pallidum were examined using ten monoclonal antibodies specific to the type-specific antigen proteins of prototype strains (Gilliam, Karp, Kato, Kawasaki and Kuroki) by improved immunofluorescent microscopy. All antibodies were used at a 1 : 1,000 dilution, at which the antibodies reacted specifically to only one of the prototypes used for production of the antibodies. O. tsutsugamushi in L. fletcheri reacted to three of four anti-Kato antibodies, however only one antibody reacted to O. tsutsugamushi in all individual L. fletcheri, and two antibodies reacted only to the microorganisms in some of the mites. Similar results were obtained with anti-Karp antibodies to L. arenicola and L. pallidum. Experiments with serially diluted antibodies indicated that the fluctuation occurred only with antibodies, the end-points of which were close to 1 : 1,000. Therefore, our observations suggested that a single mite was not infected with multiple strains and that each infected colony of Leptotrombidium harbored a single antigenic strain of O. tsutsugamushi that is antigenically similar but different in some degree from the prototype strains.
