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Infection and Immunity, April 2008, p. 1572-1580, Vol. 76, No. 4
0019-9567/08/$08.00+0     doi:10.1128/IAI.01466-07
Copyright © 2008, American Society for Microbiology. All Rights Reserved.

A Variable-Length PCR Target Protein of Ehrlichia chaffeensis Contains Major Species-Specific Antibody Epitopes in Acidic Serine-Rich Tandem Repeats{triangledown}

Tian Luo,1 Xiaofeng Zhang,1 Abdul Wakeel,1 Vsevolod L. Popov,1 and Jere W. McBride1,2,3,4*

Departments of Pathology,1 Microbiology and Immunology,2 Center for Biodefense and Emerging Infectious Diseases,3 Sealy Center for Vaccine Development, University of Texas Medical Branch, Galveston, Texas 775554

Received 1 November 2007/ Returned for modification 5 December 2007/ Accepted 10 January 2008

Ehrlichia chaffeensis and E. canis have a small subset of tandem repeat (TR)-containing proteins that elicit strong host immune responses and are associated with host-pathogen interactions. In a previous study, we molecularly characterized a highly conserved 19-kDa major immunoreactive protein (gp19) of E. canis and identified the corresponding TR-containing ortholog variable-length PCR target (VLPT) protein in E. chaffeensis. In this study, the native 32-kDa VLPT protein was identified and the immunodeterminants defined in order to further understand the molecular basis of the host immune response to E. chaffeensis. Synthetic and/or recombinant polypeptides corresponding to various regions of VLPT were used to localize major antibody epitopes to the TR-containing region. Major antibody epitopes were identified in three nonidentical repeats (R2, R3, and R4), which reacted strongly with antibodies in sera from an E. chaffeensis-infected dog and human monocytotropic ehrlichiosis patients. VLPT-R3 and VLPT-R2 reacted most strongly with antibody, and the epitope was further localized to a nearly identical proximal 17-amino-acid region common between these repeats that was species specific. The epitope in R4 was distinct from that of R2 and R3 and was found to have conformational dependence. VLPT was detected in supernatants from infected cells, indicating that the protein was secreted. VLPT was localized on both reticulate and dense-core cells, and it was found extracellularly in the morula fibrillar matrix and associated with the morula membrane.

* Corresponding author. Mailing address: Department of Pathology, University of Texas Medical Branch, Galveston, TX 77555-0609. Phone: (409) 747-2498. Fax: (409) 747-2455. E-mail: jemcbrid{at}utmb.edu

{triangledown} Published ahead of print on 22 January 2008.

Editor: R. P. Morrison

Infection and Immunity, April 2008, p. 1572-1580, Vol. 76, No. 4
0019-9567/08/$08.00+0     doi:10.1128/IAI.01466-07
Copyright © 2008, American Society for Microbiology. All Rights Reserved.



This article has been cited by other articles:

  • Zhu, B., Nethery, K. A., Kuriakose, J. A., Wakeel, A., Zhang, X., McBride, J. W. (2009). Nuclear Translocated Ehrlichia chaffeensis Ankyrin Protein Interacts with a Specific Adenine-Rich Motif of Host Promoter and Intronic Alu Elements. Infect. Immun. 77: 4243-4255 [Abstract] [Full Text]  
  • Luo, T., Zhang, X., McBride, J. W. (2009). Major Species-Specific Antibody Epitopes of the Ehrlichia chaffeensis p120 and E. canis p140 Orthologs in Surface-Exposed Tandem Repeat Regions. CVI 16: 982-990 [Abstract] [Full Text]  
  • Wakeel, A., Kuriakose, J. A., McBride, J. W. (2009). An Ehrlichia chaffeensis Tandem Repeat Protein Interacts with Multiple Host Targets Involved in Cell Signaling, Transcriptional Regulation, and Vesicle Trafficking. Infect. Immun. 77: 1734-1745 [Abstract] [Full Text]  


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