WESTERN IMMUNOBLOT ANALYSIS OF EHRLICHIA-CHAFFEENSIS, EHRLICHIA-CANIS, OR E-EWINGII INFECTIONS IN DOGS AND HUMANS

Ehrlichia chaffeensis, E. canis, and E. ewingii are genetically closel y related, as determined by 16S rRNA gene base sequence comparison, bu t they exhibit biologic differences. E. chaffeensis is the etiologic a gent of human ehrlichiosis. E. canis and E. ewingii cause two distinct ly different forms of canine ehrlichiosis and infect different types o f leukocytes, monocytes and granulocytes, respectively. E. chaffeensis can also infect dogs. In the study, Western immunoblot analysis of se ra from dogs inoculated with E. chaffeensis, E. canis, or E. ewingii w as performed to determine antigenic specificity and the intensities of the reactions to purified E. chaffeensis and E. canis antigens. At 2 to 3 weeks postexposure, antisera from four dogs inoculated with E. ch affeensis reacted with 64-, 47-, 31-, and 29-kDa proteins of E. chaffe ensis but reacted poorly with E. canis antigen. In contrast, at 2 to 3 weeks postexposure, antisera from four E. canis-inoculated dogs react ed strongly with the 30-kDa major antigen of E. canis but reacted poor ly with proteins from E. chaffeensis. At 4 weeks postexposure, the ser a from three E. ewingii-inoculated dogs showed weak binding to 64- and 47-kDa proteins of both E. chaffeensis and E. canis. Convalescent-pha se sera from human ehrlichiosis patients and sera from dogs chronicall y infected with E. ewingii strongly reacted with similar sets of prote ins of E. chaffeensis and E. canis with similar intensities. However, sera from dogs chronically infected with E. canis reacted more strongl y with a greater number of E. canis proteins than with E. chaffeensis proteins. The protein specificity described in the report suggests tha t dogs with E. canis infections can be distinguished from E. chaffeens is-infected animals by Western immunoblot analysis with both E. canis and E. chaffeensis antigens.