Expression of CX3CL1 (fractalkine) in mice with endothelial-target rickettsial infection of the spotted-fever group.

Fractalkine (CX3CL1) is a chemokine expressed mainly by endothelial cells, which are the major cellular targets of rickettsiae. We used immunohistochemistry to investigate the normal expression of CX3CL1 in mice and the kinetics of expression of this chemokine throughout the course of lethal and sublethal rickettsial infections in a mouse model of spotted-fever group rickettsioses. The peak of expression of fractalkine on day 3 of infection coincided with the time of infiltration of macrophages into infected tissues and preceded the peak of rickettsial content in tissues.