relA is Achilles' heel for mycobacterial pathogens as demonstrated with deletion mutants in Mycobacterium avium subsp. paratuberculosis and mycobacterium bovis bacillus Calmette-Guérin (BCG)

Tuberculosis (Edinb). 2020 Jan:120:101904. doi: 10.1016/j.tube.2020.101904. Epub 2020 Jan 15.

Abstract

Studies with Mycobacterium avium subsp. paratuberculosis (Map) in cattle revealed deletion of relA, a global regulator gene, abrogated ability of the mutant to establish a persistent infection, attributed to development of an immune response that cleared infection. Analysis of the recall response demonstrated presence of CD8 cytotoxic T cells that kill intracellular bacteria. Replication of the primary response demonstrated the CTL response could be elicited with the ΔMap/relA mutant or the target of the immune response, a 35 kD membrane protein. Follow up comparative studies with Mycobacterium bovis bacillus Calmette-Guérin (BCG) and a BCG relA (ΔBCG/relA) deletion mutant revealed deletion of relA enhanced the CTL response compared to BCG. Analysis of the cytokine profile of cells proliferating in response to stimulation with BCG or BCG/relA showed increased expression of IFN-γ, TNF-α, and IL-17 by cells stimulated with ΔBCG/relA in comparison with BCG. The proliferative and CTL responses were markedly reduced in response to stimulation with heat killed BCG or ΔBCG/relA. Intracellular bacterial killing was mediated through the perforin, granzyme B (GnzB), and the granulysin pathway. The data indicate relA is the Achilles' heel for pathogenic mycobacteria and deletion may be key to improving efficacy of attenuated vaccines for mycobacterial pathogens.

Keywords: Achilles's heel; Cytotoxic CD8 T cells; MHC restriction; Mycobacterium a. paratuberculosis; Mycobacterium bovis; Mycobacterium tuberculosis; relA.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Bacterial Proteins / genetics*
  • Bacterial Proteins / metabolism
  • Cattle
  • Cell Proliferation
  • Cells, Cultured
  • Coculture Techniques
  • Cytokines / metabolism
  • Granzymes / metabolism
  • Host-Pathogen Interactions
  • Ligases / genetics*
  • Ligases / metabolism
  • Lymphocyte Activation
  • Macrophages / immunology
  • Macrophages / metabolism
  • Macrophages / microbiology
  • Male
  • Microbial Viability
  • Mycobacterium avium subsp. paratuberculosis / genetics*
  • Mycobacterium avium subsp. paratuberculosis / immunology
  • Mycobacterium avium subsp. paratuberculosis / metabolism
  • Mycobacterium bovis / genetics*
  • Mycobacterium bovis / metabolism
  • Mycobacterium bovis / pathogenicity
  • Sequence Deletion*
  • T-Lymphocytes, Cytotoxic / immunology
  • T-Lymphocytes, Cytotoxic / metabolism
  • T-Lymphocytes, Cytotoxic / microbiology

Substances

  • Bacterial Proteins
  • Cytokines
  • Granzymes
  • Ligases
  • guanosine 3',5'-polyphosphate synthetases