Identification of the antigenic constituents of Ehrlichia chaffeensis

Ehrlichia chaffeensis, the novel etiologic agent of human ehrlichiosis in the United States, was first isolated in 1990 and reported in 1991. To analyze the antigenic components of E. chaffeensis, we cultivated these obligate intracellular bacteria in DH82 cells, purified the ehrlichiae by renografin density gradient centrifugation, and examined the antigens by Western immunoblotting. Rabbit and human antisera to E. chaffeensis revealed more than 20 bands ranging from 20 to 200 kD. The distinct 22-kD protein was heat labile. The rest of the major immunoreactive components were heat stable