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Infection and Immunity, November 2003, p. 6329-6337, Vol. 71, No. 11
0019-9567/03/$08.00+0     DOI: 10.1128/IAI.71.11.6329-6337.2003
Copyright © 2003, American Society for Microbiology. All Rights Reserved.

Rhodococcus equi Secreted Antigens Are Immunogenic and Stimulate a Type 1 Recall Response in the Lungs of Horses Immune to R. equi Infection

Andrea K. Kohler,1 Diana M. Stone,1 Melissa T. Hines,2 Barbara A. Byrne,3,{dagger} Debra C. Alperin,1 Linda K. Norton,1 and Stephen A. Hines1*

Department of Veterinary Microbiology and Pathology,1 Department of Veterinary Clinical Sciences, Washington State University, Pullman, Washington 99164-7040,2 Department of Veterinary Pathobiology, Purdue University, West Lafayette, Indiana 47907-20273

Received 24 March 2003/ Returned for modification 27 May 2003/ Accepted 5 August 2003

Rhodococcus equi is an opportunistic pathogen in immunocompromised humans and an important primary pathogen in young horses. Although R. equi infection can produce life-threatening pyogranulomatous pneumonia, most foals develop a protective immune response that lasts throughout life. The antigen targets of this protective response are currently unknown; however, Mycobacterium tuberculosis is a closely related intracellular pathogen and provides a model system. Based on previous studies of M. tuberculosis protective antigens released into culture filtrate supernatant (CFS), a bacterial growth system was developed for obtaining R. equi CFS antigens. Potential immunogens for prevention of equine rhodococcal pneumonia were identified by using immunoblots. The 48-h CFS contained five virulence-associated protein bands that migrated between 12 and 24 kDa and were recognized by sera from R. equi-infected foals and immune adult horses. Notably, the CFS contained the previously characterized proteins VapC, VapD, and VapE, which are encoded by genes on the R. equi virulence plasmid. R. equi CFS was also examined for the ability to stimulate a type 1-like memory response in immune horses. Three adult horses were challenged with virulent R. equi, and cells from the bronchoalveolar lavage fluid were recovered before and 1 week after challenge. In vitro stimulation of pulmonary T-lymphocytes with R. equi CFS resulted in significant proliferation and a significant increase in gamma interferon mRNA expression 1 week after challenge. These results were consistent with a memory effector response in immune adult horses and provide evidence that R. equi CFS proteins are antigen targets in the immunoprotective response against R. equi infection.

* Corresponding author. Mailing address: Department of Veterinary Microbiology and Pathology, Washington State University, Pullman, WA 99164-7040. Phone: (509) 335-6030. Fax: (509) 335-8529. E-mail: shines{at}vetmed.wsu.edu.

Editor: J. N. Weiser

{dagger} Present address: Department of Pathology, Microbiology, and Immunology, University of California, Davis, Davis, CA 95616

Infection and Immunity, November 2003, p. 6329-6337, Vol. 71, No. 11
0019-9567/03/$08.00+0     DOI: 10.1128/IAI.71.11.6329-6337.2003
Copyright © 2003, American Society for Microbiology. All Rights Reserved.



This article has been cited by other articles:

  • Martens, R. J., Cohen, N. D., Jones, S. L., Moore, T. A., Edwards, J. F. (2005). Protective Role of Neutrophils in Mice Experimentally Infected with Rhodococcus equi. Infect. Immun. 73: 7040-7042 [Abstract] [Full Text]  
  • Patton, K. M., McGuire, T. C., Fraser, D. G., Hines, S. A. (2004). Rhodococcus equi-Infected Macrophages Are Recognized and Killed by CD8+ T Lymphocytes in a Major Histocompatibility Complex Class I-Unrestricted Fashion. Infect. Immun. 72: 7073-7083 [Abstract] [Full Text]  


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