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Clinical and Vaccine Immunology, June 2007, p. 669-677, Vol. 14, No. 6
1071-412X/07/$08.00+0     doi:10.1128/CVI.00042-07
Copyright © 2007, American Society for Microbiology. All Rights Reserved.

Experimental Infection of Neonatal Foals with Rhodococcus equi Triggers Adult-Like Gamma Interferon Induction{triangledown}

Stephanie Jacks,1 Steeve Giguère,1* P. Cynda Crawford,2 and William L. Castleman3

Department of Large Animal Clinical Sciences,1 Department of Small Animal Clinical Sciences,2 Department of Infectious Diseases and Pathology, College of Veterinary Medicine, University of Florida, Gainesville, Florida 326103

Received 20 January 2007/ Returned for modification 12 March 2007/ Accepted 22 March 2007

Rhodococcus equi is a facultative intracellular pathogen that causes pneumonia in young foals but does not induce disease in immunocompetent adult horses. Clearance of R. equi depends mainly on gamma interferon (IFN-{gamma}) production by T lymphocytes, whereas the predominance of interleukin 4 (IL-4) is detrimental. Young foals, like neonates of many other species, are generally deficient in the ability to produce IFN-{gamma}. The objective of this study was to compare the cytokine profiles, as well as cell-mediated and antibody responses, of young foals to those of adult horses following intrabronchial challenge with R. equi. The lymphoproliferative responses of bronchial lymph node (BLN) cells to concanavalin A were significantly higher in foals than in adult horses. In contrast, adult horses had significantly higher lymphoproliferative responses to R. equi antigens than did foals. Infected foals had significantly lower IL-4 mRNA expression but significantly higher IFN-{gamma} expression and IFN-{gamma}/IL-4 ratio in R. equi-stimulated BLN lymphocytes than did infected adults. Infection with R. equi in foals resulted in a significant increase in the percentage of T lymphocytes and CD4+ T lymphocytes in bronchoalveolar lavage fluid in association with a significant decrease in the percentage of these cell populations in BLNs. Infection of foals also resulted in a marked increase in serum immunoglobulin Ga (IgGa) and IgGb levels, resulting in concentrations in serum that were significantly higher than those of adult horses. This study demonstrates that the immune response to R. equi in foals is not biased toward IL-4 and is characterized by the predominant induction of IFN-{gamma}.

* Corresponding author. Mailing address: Department of Large Animal Clinical Sciences, College of Veterinary Medicine, University of Florida, P.O. Box 100136, 2015 S.W. 16th Ave., Gainesville, FL 32610. Phone: (352) 392-4700, ext. 5678. Fax: (208) 460-3930. E-mail: gigueres{at}mail.vetmed.ufl.edu

{triangledown} Published ahead of print on 4 April 2007.

Clinical and Vaccine Immunology, June 2007, p. 669-677, Vol. 14, No. 6
1071-412X/07/$08.00+0     doi:10.1128/CVI.00042-07
Copyright © 2007, American Society for Microbiology. All Rights Reserved.



This article has been cited by other articles:

  • Muscatello, G., Gilkerson, J. R., Browning, G. F. (2009). Detection of Virulent Rhodococcus equi in Exhaled Air Samples from Naturally Infected Foals. J. Clin. Microbiol. 47: 734-737 [Abstract] [Full Text]  
  • Flaminio, M. J. B. F., Nydam, D. V., Marquis, H., Matychak, M. B., Giguere, S. (2009). Foal Monocyte-Derived Dendritic Cells Become Activated upon Rhodococcus equi Infection. CVI 16: 176-183 [Abstract] [Full Text]  


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