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Infection and Immunity, July 2007, p. 3604-3613, Vol. 75, No. 7
0019-9567/07/$08.00+0     doi:10.1128/IAI.02028-06
Copyright © 2007, American Society for Microbiology. All Rights Reserved.

Virulence Potential of Ehrlichia chaffeensis Strains of Distinct Genome Sequences{triangledown} ,{dagger}

Koshiro Miura and Yasuko Rikihisa*

Department of Veterinary Biosciences, The Ohio State University, 1925 Coffey Rd., Columbus, Ohio 43210

Received 26 December 2006/ Returned for modification 6 March 2007/ Accepted 4 April 2007

Human monocytic ehrlichiosis, one of the most frequent life-threatening tick-borne zoonoses, is caused by Ehrlichia chaffeensis that lacks endotoxin and peptidoglycan. While sequence polymorphisms in several genes in E. chaffeensis strains have been reported, global genomic divergence and biological differences among strains are unknown. The objectives of the present study were to compare the genome sequences of strains of E. chaffeensis and to examine the virulence potentials of the strains with defined genome sequences. Genomic DNA was extracted from purified E. chaffeensis strains Wakulla and Liberty, and comparative genome hybridization was performed using a densely tiled microarray of 147,027 chromosome positions of the E. chaffeensis strain Arkansas genome. The results revealed that 4,663 and 5,325 positions in the chromosomes of strains Wakulla and Liberty, respectively, were different from those in the chromosome of strain Arkansas, including three common major polymorphic chromosomal regions. Of various functional categories, the differences were most concentrated in genes predicted to encode cell envelope proteins. Of all the open reading frames (ORFs), 21 omp-1 (p28 gene) paralogs, nine genes encoding hypothetical proteins, two genes encoding ankyrin repeat proteins, and hemE contained the most differences. Several highly polymorphic ORFs were confirmed by sequencing. When the E. chaffeensis strains were inoculated into severe combined immunodeficiency mice, the order of the severity of clinical signs and the bacterial burden detected in mice was Wakulla > Liberty > Arkansas. Severe diffuse inflammation and granulomatous inflammation were evident in the livers of mice infected with strains Wakulla and Arkansas, respectively, but not in the livers of mice infected with strain Liberty. These results revealed distinct virulence phenotypes of E. chaffeensis strains with defined genome sequences.

* Corresponding author. Mailing address: Department of Veterinary Biosciences, The Ohio State University, 1925 Coffey Rd., Columbus, OH 43210. Phone: (614) 292-9677. Fax: (614) 292-6473. E-mail: rikihisa.1{at}osu.edu

{triangledown} Published ahead of print on 16 April 2007.

{dagger} Supplemental material for this article may be found at http://iai.asm.org/.

Editor: V. J. DiRita

Infection and Immunity, July 2007, p. 3604-3613, Vol. 75, No. 7
0019-9567/07/$08.00+0     doi:10.1128/IAI.02028-06
Copyright © 2007, American Society for Microbiology. All Rights Reserved.



This article has been cited by other articles:

  • Miura, K., Rikihisa, Y. (2009). Liver Transcriptome Profiles Associated with Strain-Specific Ehrlichia chaffeensis-Induced Hepatitis in SCID Mice. Infect. Immun. 77: 245-254 [Abstract] [Full Text]  


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