Our preliminary studies and those of others clearly demonstrate a dominance of a single species of spotted fever group rickettsiae in ixodid tick vectors, Dermacentor variabilis and D. andersoni. Extensive tick surveys in Montana, Ohio, California, and Maryland revealed the dominance of nonpathogenic rickettsiae in tick populations. The presence of nonpathogenic tick symbionts may account for the low infection rates of Rickettsia rickettsii in D. andersoni and D. variabilis thus resulting in patchy distribution of human cases of Rocky Mountain spotted fever in the US. This project was initiated to investigate the molecular consequences and epidemiological significance of multiple rickettsial infections in ticks. We have proposed that the interactive effects between obligate intracellular rickettsiae within individual ticks may be of sufficient relevance and magnitude to alter the vector competence of ticks. Thus, we have focused on rickettsial symbionts acquired transovarially by D. variabilis ticks, namely Rickettsia montanensis and R. peacockii. We have investigated the prevalence and relative efficiency of transovarial interference of R. montanensis within D. variabilis ticks as mediated by R. rhipicephali. We have also focused on the D. variabilis genes that are differentially expressed in response to rickettsial infection within tick ovarian tissues. We have constructed several tissue-specific cDNA libraries from infected and uninfected D. variabilis. For the renewal application, we are proposing to further refine and characterize molecular mechanisms underlying transovarial interference. Studies under first aim define the functional role of identified molecules that initiate the exclusion of secondary rickettsial infections of tick ovaries.
The second aim will be focused on investigating the role of the selected tick molecules in the maintenance and transmission of rickettsiae. ? ?

Agency
National Institute of Health (NIH)
Institute
National Institute of Allergy and Infectious Diseases (NIAID)
Type
Research Project (R01)
Project #
5R01AI043006-09
Application #
7259470
Study Section
Special Emphasis Panel (ZRG1-TMP (99))
Program Officer
Costero, Adriana
Project Start
1998-03-01
Project End
2009-06-30
Budget Start
2007-07-01
Budget End
2008-06-30
Support Year
9
Fiscal Year
2007
Total Cost
$246,409
Indirect Cost
Name
University of Maryland Baltimore
Department
Microbiology/Immun/Virology
Type
Schools of Medicine
DUNS #
188435911
City
Baltimore
State
MD
Country
United States
Zip Code
21201
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Gulia-Nuss, Monika; Nuss, Andrew B; Meyer, Jason M et al. (2016) Genomic insights into the Ixodes scapularis tick vector of Lyme disease. Nat Commun 7:10507
Gillespie, Joseph J; Kaur, Simran J; Rahman, M Sayeedur et al. (2015) Secretome of obligate intracellular Rickettsia. FEMS Microbiol Rev 39:47-80
Gillespie, Joseph J; Phan, Isabelle Q H; Scheib, Holger et al. (2015) Structural Insight into How Bacteria Prevent Interference between Multiple Divergent Type IV Secretion Systems. MBio 6:e01867-15
Pelc, Rebecca S; McClure, Jennifer C; Kaur, Simran J et al. (2015) Disrupting protein expression with Peptide Nucleic Acids reduces infection by obligate intracellular Rickettsia. PLoS One 10:e0119283
Smith, Todd A; Driscoll, Timothy; Gillespie, Joseph J et al. (2015) A Coxiella-like endosymbiont is a potential vitamin source for the Lone Star tick. Genome Biol Evol 7:831-8
Pelc, R S; McClure, J C; Sears, K T et al. (2014) Defending the fort: a role for defensin-2 in limiting Rickettsia montanensis infection of Dermacentor variabilis. Insect Mol Biol 23:457-65
Gillespie, Joseph J; Driscoll, Timothy P; Verhoeve, Victoria I et al. (2014) Genomic diversification in strains of Rickettsia felis Isolated from different arthropods. Genome Biol Evol 7:35-56
Petchampai, N; Sunyakumthorn, P; Guillotte, M L et al. (2014) Molecular and functional characterization of vacuolar-ATPase from the American dog tick Dermacentor variabilis. Insect Mol Biol 23:42-51
Rahman, M Sayeedur; Gillespie, Joseph J; Kaur, Simran Jeet et al. (2013) Rickettsia typhi possesses phospholipase A2 enzymes that are involved in infection of host cells. PLoS Pathog 9:e1003399

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