title: Transcript heterogeneity of the p44 multigene family in a human granulocytic ehrlichiosis agent transmitted by ticks.
abstract: Human granulocytic ehrlichiosis (HGE) is an emerging tick-borne zoonosis caused by a strain of Anaplasma phagocytophila called the HGE agent, an obligatory intracellular bacterium. The agent expresses immunodominant 44-kDa outer membrane proteins (P44s) encoded by a multigene family. The present study established an experimental process for transmission of the HGE agent from infected mice (a reservoir model) to nymphal Ixodes scapularis ticks (a biological vector) and subsequently to horses (a patient model) by the adult infected ticks. Overall, a total of 20 different p44 transcripts were detected in the mammals, ticks, and cell cultures. Among them, a transcript from a p44-18 gene was major at acute stage in mice and horses but minor in ticks. Both mRNA and protein produced from the p44-18 gene were detected in the HGE agent cultivated in HL-60 cells at 37 degrees C, but their expression levels decreased in the organisms cultivated at 24 degrees C, suggesting that temperature is one of the factors that influence the expression of members of the p44 multigene family. Several additional p44 transcripts that were not detected in the mammals at the acute stage of infection were detected in ticks. Phylogenetic analysis of the 20 different p44 transcripts revealed that the major transcripts found in mammals and ticks were distinct, suggesting a difference in surface properties between populations of the HGE agent in different host environments. The present study provides new information for understanding the role of the p44 multigene family in transmission of the HGE agent between mammals and ticks.
authors.affiliation: Department of Veterinary Biosciences, College of Veterinary Medicine, The Ohio State University, Columbus, Ohio 43210-1093, USA.
authors.forename: Ning
authors.initials: N
authors.lastname: Zhi
authors.forename: Norio
authors.initials: N
authors.lastname: Ohashi
authors.forename: Tomoko
authors.initials: T
authors.lastname: Tajima
authors.forename: Jason
authors.initials: J
authors.lastname: Mott
authors.forename: Roger W
authors.initials: RW
authors.lastname: Stich
authors.forename: Debra
authors.initials: D
authors.lastname: Grover
authors.forename: Sam R
authors.initials: SR
authors.lastname: Telford
authors.forename: Quan
authors.initials: Q
authors.lastname: Lin
authors.forename: Yasuko
authors.initials: Y
authors.lastname: Rikihisa
mesh_terms: D000595:Amino Acid Sequence; D000709:Anaplasma / Q000235:genetics*; D000818:Animals; D001425:Bacterial Outer Membrane Proteins / Q000235:genetics*; D003001:Cloning, Molecular; D016873:Ehrlichiosis / Q000235:genetics* / Q000635:transmission; D018740:Genetic Heterogeneity; D006736:Horses; D018884:Ixodes; D051379:Mice; D008811:Mice, Inbred DBA; D008969:Molecular Sequence Data; D005810:Multigene Family; D012329:RNA, Bacterial / Q000235:genetics*; D012333:RNA, Messenger / Q000235:genetics*; D017422:Sequence Analysis, DNA; D017386:Sequence Homology, Amino Acid; D013987:Ticks / Q000382:microbiology
chemical_list: D001425:Bacterial Outer Membrane Proteins; D012329:RNA, Bacterial; D012333:RNA, Messenger; C450839:p44 protein, Anaplasma phagocytophila