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Clinical and diagnostic laboratory immunology2003; 10(2); 208-215; doi: 10.1128/cdli.10.2.208-215.2003

Clearance of virulent but not avirulent Rhodococcus equi from the lungs of adult horses is associated with intracytoplasmic gamma interferon production by CD4+ and CD8+ T lymphocytes.

Abstract: Rhodococcus equi is a gram-positive bacterium that infects alveolar macrophages and causes rhodococcal pneumonia in horses and humans. The virulence plasmid of R. equi appears to be required for both pathogenicity in the horse and the induction of protective immunity. An understanding of the mechanisms by which virulent R. equi circumvents protective host responses and by which bacteria are ultimately cleared is important for development of an effective vaccine. Six adult horses were challenged with either virulent R. equi or an avirulent, plasmid-cured derivative. By using a flow cytometric method for intracytoplasmic detection of gamma interferon (IFN-gamma) in equine bronchoalveolar lavage fluid (BALF) cells, clearance of the virulent strain was shown to be associated with increased numbers of pulmonary CD4(+) and CD8(+) T lymphocytes producing IFN-gamma. There was no change in IFN-gamma-positive cells in peripheral blood, suggesting that a type 1 recall response at the site of challenge was protective. The plasmid-cured strain of R. equi was cleared in horses without a significant increase in IFN-gamma-producing T lymphocytes in BALF. In contrast to these data, a previous report in foals suggested an immunomodulating role for R. equi virulence plasmid-encoded products in downregulating IFN-gamma expression by equine CD4(+) T lymphocytes. Intracytoplasmic detection of IFN-gamma provides a method to better determine whether modulation of macrophage-activating cytokines by virulent strains occurs uniquely in neonates and contributes to their susceptibility to rhodococcal pneumonia.
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Publication Date: 2003-03-11 PubMed ID: 12626444PubMed Central: PMC150533DOI: 10.1128/cdli.10.2.208-215.2003Google Scholar: Lookup
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  • Comparative Study
  • Journal Article
  • Research Support
  • Non-U.S. Gov't

Summary

This research summary has been generated with artificial intelligence and may contain errors and omissions. Refer to the original study to confirm details provided. Submit correction.

The research presents a study about the effect of the virulent and avirulent strains of Rhodococcus equi, a bacteria causing pneumonia, on the immune response in adult horses. The study found that the clearance of the virulent strain is associated with an increase in certain immune cells producing gamma interferon.

Study Overview

The researchers’ primary aim was to understand how the virulent form of Rhodococcus equi, a bacterium causing rhodococcal pneumonia in horses and humans, evades the host’s immune responses and how the bacteria eventually gets cleared from the host’s system.

  • The researchers embarked on this study with the bigger goal of aiding the development of an effective vaccine.
  • Six adult horses were deliberately infected with either the virulent strain of R. equi or an avirulent form of the same bacterium, that had been cured of its virulence-conferring plasmid.

Methodology and Findings

Using a flow cytometric method, the researchers measured the intracytoplasmic production of a specific immune marker, gamma interferon (IFN-gamma), in the broncho-alveolar lavage fluid (BALF) cells of the horses.

  • They observed that the clearance of the virulent strain of R. equi was associated with an increase in the number of two types of immune cell, CD4(+) and CD8(+) T lymphocytes, producing IFN-gamma.
  • This significant increase was only seen in the lungs and not in the peripheral blood, suggesting that a targeted immune response was activated at the site of infection.
  • On the other hand, the avirulent strain of R. equi was cleared from the horses without a significant increase in T lymphocytes producing IFN-gamma in BALF.

Comparison to Previous Research

The researchers compared their findings to a previous study on foals, which suggested that the virulence factors encoded on R. equi’s plasmid could interfere with IFN-gamma expression in CD4(+) T lymphocytes, thus altering the immune response. The results of this current study suggest this phenomenon may be specifically applicable to neonates and could potentially explain their increased susceptibility to rhodococcal pneumonia.

Conclusion

The research concludes by endorsing further use of intracytoplasmic detection of IFN-gamma as a valuable method to better understand the effect of virulent strains of R. equi on the immune system’s response.

Cite This Article

APA
Hines SA, Stone DM, Hines MT, Alperin DC, Knowles DP, Norton LK, Hamilton MJ, Davis WC, McGuire TC. (2003). Clearance of virulent but not avirulent Rhodococcus equi from the lungs of adult horses is associated with intracytoplasmic gamma interferon production by CD4+ and CD8+ T lymphocytes. Clin Diagn Lab Immunol, 10(2), 208-215. https://doi.org/10.1128/cdli.10.2.208-215.2003

Publication

Clinical and diagnostic laboratory immunology
ISSN: 1071-412X
NlmUniqueID: 9421292
Country: United States
Language: English
Volume: 10
Issue: 2
Pages: 208-215

Researcher Affiliations

Hines, Stephen A
  • Department of Veterinary Microbiology and Pathology, Washington State University, Pullman, Washington 99164-7040, USA. shines@vetmed.wsu.edu
Stone, Diana M
    Hines, Melissa T
      Alperin, Debby C
        Knowles, Donald P
          Norton, Linda K
            Hamilton, Mary J
              Davis, William C
                McGuire, Travis C

                  MeSH Terms

                  • Actinomycetales Infections / immunology
                  • Actinomycetales Infections / veterinary
                  • Age Factors
                  • Animals
                  • Bronchoalveolar Lavage Fluid / cytology
                  • Bronchoalveolar Lavage Fluid / immunology
                  • CD2 Antigens / metabolism
                  • CD4-Positive T-Lymphocytes / immunology
                  • CD4-Positive T-Lymphocytes / metabolism
                  • CD4-Positive T-Lymphocytes / microbiology
                  • CD8-Positive T-Lymphocytes / immunology
                  • CD8-Positive T-Lymphocytes / metabolism
                  • CD8-Positive T-Lymphocytes / microbiology
                  • Cytoplasm / immunology
                  • Cytoplasm / microbiology
                  • Flow Cytometry / methods
                  • Horse Diseases / microbiology
                  • Horses
                  • Interferon-gamma / biosynthesis
                  • Plasmids
                  • Pneumonia / immunology
                  • Pneumonia / microbiology
                  • Pneumonia / veterinary
                  • Rhodococcus equi / genetics
                  • Rhodococcus equi / pathogenicity
                  • Virulence

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