The tick-transmitted rickettsial pathogens Anaplasma phagocytophilum and A. marginale cause potentially fatal, acute or chronic disease of man and animals. The genomes of both bacteria contain contingency loci;the organisms interact with host immunity by recombination of functional pseudogenes into expression sites needing major surface antigens. These organisms represent valuable models for the study of coevolution because of variable levels of natural selection due to immunity imposed by hosts, obligate drift imposed by transmission through ticks and hosts, and strategies of hyper-recombination utilized by the pathogens. Despite theories of optimal recombination strategies for pathogenic bacteria, particular strategies are highly variable. Few studies have combined experimental, field, genomic, and theory-based research to investigate the evolution and emergence of new chronic infectious disease. Our long-term goals are to limit disease emergence through a study of molecular and evolutionary interactions between hosts, vectors and pathogens that lead to persistence.
The specific aims are: 1. To determine if multiple closely-related strains of A. phagocytophilum with different host tropisms may circulate in natural ecosystems. 2. To sequence the genomes of the Hoopa WR and AP-variant 1 strains of A. phagocytophilum. 3. To experimentally describe the kinetics of infection by different strains of A. phagocytophilum in host species that typically undergoes persistent or limited infections, and 4. To model the evolution and emergence of A. phagocytophilum genospecies. The rationale is that field studies will document coevolved pathogen-host species associations;experimental research will show how reservoir and infection-limiting hosts differ in their imposition of natural selection via immunity;genome studies will reveal how the phenology of bacterial expression of surface antigens through hyper-recombination differs in these hosts;and theoretical modeling will integrate laboratory and field-collected data to investigate coevolutionary, microbiological, and ecological factors underlying the emergence and maintenance of A. phagocytophilum infection. Ultimately, understanding evolutionary factors in A. phagocytophilum-host interactions and disease mechanisms will contribute to our ability to control chronic infections caused by pathogenic bacteria and provide management approaches that limit the emergence of these and other vector-borne diseases.

National Institute of Health (NIH)
National Institute of General Medical Sciences (NIGMS)
Research Project (R01)
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Vector Biology Study Section (VB)
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Eckstrand, Irene A
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University of Florida
Schools of Veterinary Medicine
United States
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Foley, Janet (2015) Mini-review: Strategies for Variation and Evolution of Bacterial Antigens. Comput Struct Biotechnol J 13:407-16
Aureli, Sara; Galuppi, Roberta; Ostanello, Fabio et al. (2015) Abundance of questing ticks and molecular evidence for pathogens in ticks in three parks of Emilia-Romagna region of Northern Italy. Ann Agric Environ Med 22:459-66
Foley, Janet; Piovia-Scott, Jonah (2014) Vector biodiversity did not associate with tick-borne pathogen prevalence in small mammal communities in northern and central California. Ticks Tick Borne Dis 5:299-304
Barbet, Anthony F; Al-Khedery, Basima; Stuen, Snorre et al. (2013) An emerging tick-borne disease of humans is caused by a subset of strains with conserved genome structure. Pathogens 2:544-55
Rejmanek, Daniel; Freycon, Pauline; Bradburd, Gideon et al. (2013) Unique strains of Anaplasma phagocytophilum segregate among diverse questing and non-questing Ixodes tick species in the western United States. Ticks Tick Borne Dis 4:482-7
Al-Khedery, Basima; Lundgren, Anna M; Stuen, Snorre et al. (2012) Structure of the type IV secretion system in different strains of Anaplasma phagocytophilum. BMC Genomics 13:678
Aureli, Sara; Foley, Janet E; Galuppi, Roberta et al. (2012) Anaplasma phagocytophilum in ticks from parks in the Emilia-Romagna region of northern Italy. Vet Ital 48:413-23
Rejmanek, Daniel; Foley, Patrick; Barbet, Anthony et al. (2012) Antigen variability in Anaplasma phagocytophilum during chronic infection of a reservoir host. Microbiology 158:2632-41
Dark, Michael J; Lundgren, Anna M; Barbet, Anthony F (2012) Determining the repertoire of immunodominant proteins via whole-genome amplification of intracellular pathogens. PLoS One 7:e36456
Rejmanek, Daniel; Foley, Patrick; Barbet, Anthony et al. (2012) Evolution of antigen variation in the tick-borne pathogen Anaplasma phagocytophilum. Mol Biol Evol 29:391-400

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