gp19 is a major epitope of the bacteria Ehrlichia canis, which can be used for the detection of early acute-phase antibodies and reacts strongly with antibodies in late-acute-phase sera from experimental dogs. gp19 is encoded by a highly conserved single gene that minimizes or eliminates the potential for serologic variability.

Recombinant antigen for the diagnosis of Ehrlichiosis caused by Ehrlichia canis, a human and animal infectious disease (mainly dogs).