Dr. Walker's research interests are broadly in the area of obligately intracellular bacteria that are transmitted by arthropod vectors focused on immune mechanisms against rickettsiae, ehrlichiae and Orientia tsutsugamushi and identification of the protein antigens that stimulate immunity. Although the diseases caused by rickettsiae include many long known and feared life threatening infections such as Rocky Mountain spotted fever and epidemic typhus, elucidation of their molecular composition and effector immune mechanisms remains productive lines of investigation. In contrast, human ehrlichioses are truly emerging infectious diseases that are causing increasingly prevalent, severe infections. Ehrlichial pathogenesis and immunity are in the process of being discovered and investigated at present for these novel organisms. His focus has also added the neglected tropical rickettsial disease, scrub typhus.
His investigative armamentarium includes outstanding mouse models of spotted fever and typhus rickettsioses, monocytotropic ehrlichioses, and scrub typhus which lend themselves to the study of pathogenesis as well as immunity. Other projects include development of vaccines against Rickettsia rickettsii, R. prowazekii, E. canis, E. chaffeensis, and O. tsutsugamushi, development of new diagnostic tests utilizing patented intellectual property sponsored by the Clayton Foundation, and international collaborations in Mexico and Colombia with opportunities for field and laboratory work in tropical locations.
His research is greatly enhanced by collaborative efforts involving the molecular expertise of Drs. Jere McBride and Donald Bouyer, immunologic knowledge and skills of Dr. Rong Fang, the ultrastructural expertise of Dr. Vsevolod Popov, and the vector biology skills of Dr. Tais Saito. New initiatives include vector biology of tick-borne ehrlichial and rickettsial infections.