David H Walker, MDDavid H Walker, MD
Carmage and Martha Walls Distinguished Chair in Tropical Diseases
Executive Director, Center for Biodefense and Emerging Infectious Diseases
Departments of Pathology and Microbiology & Immunology
Phone: (409) 772-2856
Fax: (409) 772-2500
Email: dwalker@utmb.edu

Education: MD, 1969, Vanderbilt University, School of Medicine, Nashville, TN
BA, 1965, Davidson College, Davidson, NC

Overview: Immunity to and pathogenesis of arthropod-transmitted obligately intracellular bacterial infections (Rickettsia and Ehrlichia).

Research Interests

My research interests are broadly in the area of obligately intracellular bacteria that are transmitted by arthropod vectors. Three research topics are focused on immune mechanisms against rickettsiae, oriemtiae and ehrlichiae and identification of the secreted and surface 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 remain productive lines of investigation. In contrast, human ehrlichioses are truly emerging tick-transmitted infectious diseases that were unknown until recently and are causing increasingly prevalent, severe infections. Nearly everything regarding ehrlichial pathogenesis and immunity is in the process of being discovered and investigated at present for these novel organisms.

Scrub typhus caused by Orientia tsutsugamushi affects 1 million persons annually with 10% lethality. Vaccine development is an urgent need, but the mechanisms of immunity are poorly understood. My investigative armamentarium includes outstanding mouse models of spotted fever, scrub typhus, and typhus rickettsioses and monocytotropic ehrlichioses, including a tick-transmission model, which lend themselves to the study of pathogenesis as well as immunity.

The molecular studies of rickettsiae have focused on major immunodominant outer membrane proteins, including S-layer proteins, surface proteins with hydrophilic domains containing multiple repeat units and candidate adhesins. Recent data revealed that non-surface exposed T-cell stimulatory antigens shared among widely divergent rickettsiae provide significant crossprotection. The molecular studies of Ehrlichia chafeensis, E. canis, and E. muris have focused on immunodominant proteins and are now using proteomic and genomic approaches to identify protective antigens. Research on our recently developed valid models of scrub typhus are being utilized to determine the mechanisms of immunity to Orientia tsutsugamushi.

Recent Publications

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