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Infection and Immunity, November 2008, p. 4823-4832, Vol. 76, No. 11
0019-9567/08/$08.00+0     doi:10.1128/IAI.00484-08
Copyright © 2008, American Society for Microbiology. All Rights Reserved.

Total, Membrane, and Immunogenic Proteomes of Macrophage- and Tick Cell-Derived Ehrlichia chaffeensis Evaluated by Liquid Chromatography-Tandem Mass Spectrometry and MALDI-TOF Methods{triangledown} ,{dagger}

Gwi-Moon Seo,1 Chuanmin Cheng,1 John Tomich,2 and Roman R. Ganta1*

Department of Diagnostic Medicine/Pathobiology, College of Veterinary Medicine,1 Department of Biochemistry, College of Arts and Sciences, Kansas State University, Manhattan, Kansas 665062

Received 18 April 2008/ Returned for modification 5 June 2008/ Accepted 7 August 2008

Ehrlichia chaffeensis, a tick-transmitted rickettsial, is the causative agent of human monocytic ehrlichiosis. To examine protein expression patterns, we analyzed total, membrane, and immunogenic proteomes of E. chaffeensis originating from macrophage and tick cell cultures. Total proteins resolved by one-dimensional gel electrophoresis and subjected to liquid chromatography-electrospray ionization ion trap mass spectrometry allowed identification of 134 and 116 proteins from macrophage- and tick cell-derived E. chaffeensis, respectively. Because a majority of immunogenic proteins remained in the membrane fraction, individually picked total and immunogenic membrane proteins were also surveyed by liquid chromatography-tandem mass spectrometry and matrix-assisted laser desorption ionization-time of flight methods. The analysis aided the identification of 48 additional proteins. In all, 278 genes of the E. chaffeensis genome were verified as functional genes. They included genes for DNA and protein metabolism, energy metabolism and transport, membrane proteins, hypothetical proteins, and many novel proteins of unknown function. The data reported in this study suggest that the membrane of E. chaffeensis is very complex, having many expressed proteins. This study represents the first and the most comprehensive analysis of E. chaffeensis-expressed proteins. This also is the first study confirming the expression of nearly one-fourth of all predicted genes of the E. chaffeensis genome, validating that they are functionally active genes, and demonstrating that classic shotgun proteomic approaches are feasible for tick-transmitted intraphagosomal bacteria. The identity of novel expressed proteins reported in this study, including the large selection of membrane and immunogenic proteins, will be valuable in elucidating pathogenic mechanisms and developing effective prevention and control methods.

* Corresponding author. Mailing address: Department of Diagnostic Medicine/Pathobiology, College of Veterinary Medicine, Kansas State University, 1800 Denison Avenue, Manhattan, KS 66506. Phone: (785) 532-4612. Fax: (785) 532-4851. E-mail: rganta{at}vet.k-state.edu

{triangledown} Published ahead of print on 18 August 2008.

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

Editor: R. P. Morrison

Infection and Immunity, November 2008, p. 4823-4832, Vol. 76, No. 11
0019-9567/08/$08.00+0     doi:10.1128/IAI.00484-08
Copyright © 2008, American Society for Microbiology. All Rights Reserved.



This article has been cited by other articles:

  • Barbet, A. F., Byrom, B., Mahan, S. M. (2009). Diversity of Ehrlichia ruminantium Major Antigenic Protein 1-2 in Field Isolates and Infected Sheep. Infect. Immun. 77: 2304-2310 [Abstract] [Full Text]  


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