Faculty

David H. Walker, M.D.

Professor and Chair
dwalker@utmb.edu
Keiller, Route 0609
Departments of Pathology and Microbiology & Immunology
Phone: (409)772-2856
Fax: (409)772-2500

Education:	M.D. | 1969 | Vanderbilt University, School of Medicine, Nashville, TN
	B.A. | 1965 | Davidson College, Davidson, NC

Overview

Immunity to and pathogenesis of arthropod-transmitted obligate 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. Two research projects currently funded by the NIH are focused on immune mechanisms against rickettsiae and ehrlichiae and identi?cation of the immuno-dominant 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 infectious diseases that were unknown until recently and are causing increasingly prevalent, severe infections. Nearly everything regarding ehrlichial life cycle, pathogenesis and immunity is in the process of being discovered and investigated at present for these novel organisms. My research on immunity pursues hypotheses involving studies of dendritic cells, cytokines, chemokines, cytotoxic T-lymphocytes, regulatory T cells, nitric oxide, antibodies, endothelial biology and intracellular killing. My investigative armamentarium includes outstanding mouse models of spotted fever and typhus rickettsioses and monocytotropic ehrlichioses, 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 signi?cant crossprotection. The molecular studies of Ehrlichia chaffeensis, E. canis, and E. muris have focused on surface-exposed immuno¬dominant proteins and a multigene family of immunodominant 28 kDa surface proteins, and are now using proteomic and genomic approaches to identify protective antigens.

Other projects include the genomic sequencing of selected microorganisms, development of vaccines against E. canis and development of new diagnostic tests utilizing our patented genes sponsored by the Clayton Foundation, and a Fogarty training grant on emerging and reemerging rickettsial diseases in Mexico, Brazil, and Cameroon. The latter offers opportunities for ?eld and laboratory work in tropical locations.

My research is greatly enhanced by collaborative efforts involving the molecular expertise of Drs. Xuejie Yu, Jere McBride and Donald Bouyer, the immunologic knowledge and skills of Drs. Nahed Gustavo Valbuena and Lynn Soong, the ultrastructural expertise of Dr. Vsevolod Popov, and the cell biology skills of Dr. Juan Olano including confocal microscopy and ? ow cytometry.

By virtue of the breadth and depth of this collaborative team and competitively funded projects, there are numerous opportunities for student rotation and dissertation projects in molecular microbiology, immunity and microbial pathogenesis. New initiatives include molecular countermeasures against bioterrorism by microbial agents and vector biology of tick- and ?ea-borne ehrlichial and rickettsial infections. tor biology of tick- and flea-borne ehrlichial and rickettsial infections.

Recent Publications

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