UTMB Department of Pathology

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Host-Parasite Mechanisms of Rickettsial Diseases

Rickettsia are obligately intracellular bacteria that are transmitted by ticks, lice and fleas. Although recent and historical reports of the clinical impact of rickettsial infections on society have been observed especially during times of war and famine, a detailed knowledge of how the bacteria causes disease is incomplete. Therefore, the focus of my research is to identify the bacterial molecules involved in the pathogenesis of host cells by the rickettsia and to delineate their roles in the host-parasite relationship. To accomplish this goal my laboratory is following two lines of investigation. The first line is the analysis of global gene expression of rickettsia during specific events during the course of pathogenesis through utilization of bacterial microarrays. Through this process we have been able to identify, clone and express rickettsial genes that are important in the establishment of infection, including genes responsible for attachment, invasion and evasion of host cell immunity. This approach will also identify key molecules from the bacteria that may serve as novel targets for therapeutic or diagnostic intervention The second line of investigation is to determine the genetic factors from the host that are responsible for resistance or susceptibility of the host to rickettsial diseases. Thus far, we have been able to identify several distinct biological pathways that are active only in rickettsia-resistant hosts.

I am also working on a collaborative projects with Drs. Nahed Ismail, Juan Olano, Jere McBride, Xue-jie Yu and David Walker an the development of improved and more sensitive diagnostic tests for rickettsial diseases.

1. LaBruna MB, Whitworth T, Horta MC, BOUYER DH, McBride JW, Pinter A, Popov VL, Gennari SM, Walker DH: 2004. Rickettsia species infecting Amblyomma cooperi ticks from an endemic area for the Brazilian spotted fever in the state of Sao Paulo, Brazil. Journal of Clinical Microbiology.42:90-98
2. Ndip LM, BOUYER DH, Travasso da Rosa APA, Titanji VPK, Tesh RB, Walker DH: 2004. The frequent occurrence of spotted fever group rickettsiosis and a high prevalence of antibodies to arbovirus among febrile patients attending clinics in a costal region of Cameroon. Emerging Infectious Diseases. 10:432-437
3. Ndip L, Fokam E, BOUYER, DH, Ndip R, Titanji PK, Walker DH McBride J: 2004. Detection of Rickettsia africae in patients and ticks along the coastal region of Cameroon. The American Journal of Tropical Medicine and Hygiene. 71:363-7
4. Labruna MB, Whitworth T, BOUYER DH, McBride J, Carmago LMA, Carmago EP, Popov V, Walker DH: 2004. Rickettsia bellii and Rickettsia amblyommii in Amblyomma ticks from the state of Rondonia, Western Amazon, Brazil. J Medical Entomology.41:533-7
5. Lewin MR, BOUYER DH, Walker, DH, Musher DH: 2003, Rickettsia sibirica infection in members of scientific expeditions to northern Asia. Lancet 362:1201-2
6. Zavala-Velazquez JE, Zavala-Castro JE, Vado-Solis I, Ruiz-Sosa JA, Moron C, BOUYER DH, Walker DH: 2002. Identification of Ctenocephalides felis fleas as a host of Ricketsia felis, the agent of a spotted fever rickettsiosis in Yucatan, Mexico. Vector Borne and Zoonotic Diseases. 2:69-75
7. Moron CG, BOUYER DH, Yu X-J, Foil LD, Crocquet-Valdes P, Walker DH: 2001. Comparative phylogenetic analysis of the rompB genes of Rickettsia felis and Rickettsia prowazekii European human and North American flying squirrel strains. The American Journal of Tropical Medicine and Hygiene. 62:598-603
8. BOUYER DH, Stenos J, Crocquet-Valdes P, Moron CG, Popov VL, Zavala-Velazquez JE, Foil LD, Stothard DR, Azad AF, Walker DH: 2001. Rickettsia felis: the molecular characterization of a new member of the spotted fever group. International Journal of Systematic and Evolutionary Microbiology. 51:339-347

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