The long term objective of this proposal is to improve our understanding of the mechanisms of pathogenesis of ehrlichial diseases and related tick-borne rickettsial pathogens of humans and animals. These pathogens include ehrlichial infections of humans caused by Ehrlichia chaffeensis and the causative agent of human granulocytic ehrlichiosis as well as E. canis, E. equi, Cowdria ruminantium and Anaplasma marginale infections of animals. A common feature of infections caused by these rickettsial pathogens is their ability to persist in human and/or animal reservoir hosts and cause long-term infection. Long-term infections of animal reservoir hosts effectively maintain the pathogens in the environment and ensure onward transmission by the tick vector. It has been recognized recently that these rickettsiae also share several features at the molecular level. They synthesize similar major outer membrane proteins (MSP2 homologs) that are strongly recognized by sera from infected humans and animals and that can be encoded by multigene families. MSP2 homologs have been proposed as diagnostic antigens in several of these rickettsial species and are known to be at least partially protective antigens against challenge infection with live rickettsiae. However, sequence variation of MSP2 homologs may limit use of these antigens for diagnosis or vaccination and may be a factor in long term persistence of the rickettsiae. MSP2 was initially defined in A. marginale and infections of cattle with this rickettsia provide an excellent model for analyzing mechanisms of persistence and the influence of sequence variation in MSP2. In this proposal, the molecular mechanisms of sequence variation in gene transcripts encoding MSP2 (msp2) will be defined.
The specific aims are: 1) Define the complete structure of an msp2 gene RNA transcript in Anaplasma marginale; 2) Determine variable and conserved regions of msp2 gene transcripts in acute and persistent infections with A. marginale; 3) Characterize protein expression from msp2 gene transcripts in acute and persistent infections with A. marginale; 4) Determine the genomic mechanisms of msp2 variation in A. marginale; 5) Compare msp2 RNA transcripts in A. marginale and in the agent of human granulocytic ehrlichiosis. This study will provide a basis for comparison of pathogenic mechanisms involving MSP2 variation in these rickettsiae, particularly in the closely related rickettsiae causing anaplasmosis and human granulocytic ehrlichiosis.

Agency
National Institute of Health (NIH)
Institute
National Institute of Allergy and Infectious Diseases (NIAID)
Type
Research Project (R01)
Project #
3R01AI045580-01S1
Application #
6221283
Study Section
Bacteriology and Mycology Subcommittee 2 (BM)
Program Officer
Baker, Phillip J
Project Start
2000-02-01
Project End
2003-06-30
Budget Start
2000-02-01
Budget End
2000-06-30
Support Year
1
Fiscal Year
2000
Total Cost
$25,587
Indirect Cost
Name
University of Florida
Department
Pathology
Type
Schools of Veterinary Medicine
DUNS #
073130411
City
Gainesville
State
FL
Country
United States
Zip Code
32611
Granquist, Erik G; Stuen, Snorre; Crosby, Liliana et al. (2010) Variant-specific and diminishing immune responses towards the highly variable MSP2(P44) outer membrane protein of Anaplasma phagocytophilum during persistent infection in lambs. Vet Immunol Immunopathol 133:117-24
Wamsley, Heather L; Barbet, Anthony F (2008) In situ detection of Anaplasma spp. by DNA target-primed rolling-circle amplification of a padlock probe and intracellular colocalization with immunofluorescently labeled host cell von Willebrand factor. J Clin Microbiol 46:2314-9
Granquist, Erik G; Stuen, Snorre; Lundgren, Anna M et al. (2008) Outer membrane protein sequence variation in lambs experimentally infected with Anaplasma phagocytophilum. Infect Immun 76:120-6
Palmer, Guy H; Futse, James E; Knowles Jr, Donald P et al. (2006) Insights into mechanisms of bacterial antigenic variation derived from the complete genome sequence of Anaplasma marginale. Ann N Y Acad Sci 1078:15-25
Barbet, Anthony F; Lundgren, Anna M; Alleman, A Rick et al. (2006) Structure of the expression site reveals global diversity in MSP2 (P44) variants in Anaplasma phagocytophilum. Infect Immun 74:6429-37
Noh, Susan M; Brayton, Kelly A; Knowles, Donald P et al. (2006) Differential expression and sequence conservation of the Anaplasma marginale msp2 gene superfamily outer membrane proteins. Infect Immun 74:3471-9
Brayton, Kelly A; Kappmeyer, Lowell S; Herndon, David R et al. (2005) Complete genome sequencing of Anaplasma marginale reveals that the surface is skewed to two superfamilies of outer membrane proteins. Proc Natl Acad Sci U S A 102:844-9
Rodriguez, Jose-Luis; Palmer, Guy H; Knowles Jr, Donald P et al. (2005) Distinctly different msp2 pseudogene repertoires in Anaplasma marginale strains that are capable of superinfection. Gene 361:127-32
Zika, Eleni; Fauquier, Lucas; Vandel, Laurence et al. (2005) Interplay among coactivator-associated arginine methyltransferase 1, CBP, and CIITA in IFN-gamma-inducible MHC-II gene expression. Proc Natl Acad Sci U S A 102:16321-6
Brown, Wendy C; Palmer, Guy H; Brayton, Kelly A et al. (2004) CD4+ T lymphocytes from Anaplasma marginale major surface protein 2 (MSP2) vaccinees recognize naturally processed epitopes conserved in MSP3. Infect Immun 72:3688-92

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