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Infection and immunity2003; 71(11); 6329-6337; doi: 10.1128/IAI.71.11.6329-6337.2003

Rhodococcus equi secreted antigens are immunogenic and stimulate a type 1 recall response in the lungs of horses immune to R. equi infection.

Abstract: 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.
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Publication Date: 2003-10-24 PubMed ID: 14573652PubMed Central: PMC219552DOI: 10.1128/IAI.71.11.6329-6337.2003Google Scholar: Lookup
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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.

This study delves into the immune response of horses to Rhodococcus equi, an opportunistic pathogen that primarily affects immunocompromised humans and young horses. The researchers identified potential antigens for preventing equine rhodococcal pneumonia and found that the secreted antigens incite a type 1 memory response in the lungs of immune horses.

Background and Purpose

  • Opportunistic pathogens can cause diseases mainly in those individuals or organisms with weakened immune systems. Rhodococcus equi (R. equi) is one of these pathogens, prevalent in immunocompromised humans and young horses.
  • R. equi infection can lead to severe pneumonia, but most often, foals develop a life-long protective immune response against this pathogen.
  • The key protective antigens, substances that the immune system recognizes as foreign to the body and against which it reacts, remain unknown.
  • The researchers drew insight from the intricate biology of Mycobacterium tuberculosis (a similar pathogen) to develop a method for obtaining potentially protective R. equi antigens.

Methods and Main Findings

  • The researchers cultivated R. equi to produce and release potential antigens in a culture filtrate supernatant (CFS), a bacterial growth system.
  • Five virulence-associated protein bands between 12 and 24 kDa in weight were identified in the CFS that were recognized by sera from foals infected with R. equi and immune adult horses.
  • Among the identified proteins, VapC, VapD, and VapE were identified, all of which are produced by R. equi’s virulence genes.
  • The researchers tested the potential of R. equi CFS to prompt a type 1-like memory response in immune horses by challenging three horses with virulent R. equi and observing changes in their immune response.
  • Results showed a significant proliferation of pulmonary T-lymphocytes (white blood cells) and increased expression of gamma interferon mRNA, which assists in immune response one week after challenge, suggesting a memory effector response.

Implications and Conclusion

  • The findings suggest that R. equi CFS proteins are antigen targets that counterattack R. equi infection, thereby helping the immune system to recognize and rapidly response to the pathogen.
  • These results may pave the path towards the development of effective immunization techniques against Rhodococcus equi, thereby preventing severe pneumonia in horses and possibly offering insights into immune response mechanisms in other animals and humans.

Cite This Article

APA
Kohler AK, Stone DM, Hines MT, Byrne BA, Alperin DC, Norton LK, Hines SA. (2003). Rhodococcus equi secreted antigens are immunogenic and stimulate a type 1 recall response in the lungs of horses immune to R. equi infection. Infect Immun, 71(11), 6329-6337. https://doi.org/10.1128/IAI.71.11.6329-6337.2003

Publication

Infection and immunity
ISSN: 0019-9567
NlmUniqueID: 0246127
Country: United States
Language: English
Volume: 71
Issue: 11
Pages: 6329-6337

Researcher Affiliations

Kohler, Andrea K
  • Department of Veterinary Microbiology and Pathology,Washington State University, Pullman, Washington 99164-7040, USA.
Stone, Diana M
    Hines, Melissa T
      Byrne, Barbara A
        Alperin, Debra C
          Norton, Linda K
            Hines, Stephen A

              MeSH Terms

              • Actinomycetales Infections / immunology
              • Actinomycetales Infections / veterinary
              • Animals
              • Antigens, Bacterial / immunology
              • Horse Diseases / immunology
              • Horses
              • Immunologic Memory
              • Interferon-gamma / biosynthesis
              • Lung / immunology
              • Lymphocyte Activation
              • Plasmids
              • Rhodococcus equi / immunology

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              Citations

              This article has been cited 6 times.
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