Recombinant Mycobacterium bovis bacillus Calmette-Guérin (BCG) expressing mouse IL-18 augments Th1 immunity and macrophage cytotoxicity

Clin Exp Immunol. 2004 Jul;137(1):24-34. doi: 10.1111/j.1365-2249.2004.02522.x.

Abstract

Interleukin-18 (IL-18) has been demonstrated to synergize with BCG for induction of a T-helper-type 1 (Th1) immune response. Since successful treatment of superficial bladder cancer with BCG requires proper induction of Th1 immunity, we have developed a recombinant (r) BCG strain that functionally secretes mouse (m) IL-18. This rBCG-mIL-18 strain significantly increased production of the major Th1 cytokine IFN-gamma in splenocyte cultures, at levels comparable to that elicited by control BCG plus exogenous rIL-18. IFN-gamma production by splenocytes was eliminated by addition of neutralizing anti-IL-18 antibody. Endogenous IL-12 played a favourable role whereas IL-10 played an adverse role in rBCG-mIL-18-induced IFN-gamma production. Enhanced host antimycobacterial immunity was observed in mice infected with rBCG-mIL-18 which showed less splenic enlargement and reduced bacterial load compared to control mice infected with BCG. Further, splenocytes from rBCG-mIL-18-infected mice, in response to BCG antigen, displayed increased production of IFN-gamma and GMCSF, decreased production of IL-10, elevated cellular proliferation and higher differentiation of IFN-gamma-secreting cells. rBCG-mIL-18 also enhanced BCG-induced macrophage cytotoxicity against bladder cancer MBT-2 cells in a dose-dependent manner. Neutralizing all endogenous macrophage-derived cytokines tested (IL-12, IL-18 and TNF-alpha) as well as IFN-gamma severely diminished the rBCG-mIL-18-induced macrophage cytolytic activity, indicating a critical role for these cytokines in this process. Cytokine analysis for supernatants of macrophage-BCG mixture cultures manifested higher levels of IFN-gamma and TNF-alpha in rBCG-mIL-18 cultures than in control BCG cultures. Taken together, this rBCG-mIL-18 strain augments BCG's immunostimulatory property and may serve as a better agent for bladder cancer immunotherapy and antimycobacterial immunization.

MeSH terms

  • Animals
  • BCG Vaccine / immunology*
  • Cell Line, Tumor
  • Cells, Cultured
  • Dose-Response Relationship, Immunologic
  • Epitopes / immunology
  • Granulocyte-Macrophage Colony-Stimulating Factor / immunology
  • Immunity, Cellular / immunology
  • Interferon-gamma / biosynthesis
  • Interferon-gamma / immunology
  • Interleukin-10 / immunology
  • Interleukin-12 / immunology
  • Interleukin-18 / analysis
  • Interleukin-18 / immunology*
  • Macrophage Activation / immunology
  • Macrophages / immunology*
  • Mice
  • Mice, Inbred C3H
  • Mice, Inbred C57BL
  • Mycobacterium bovis / immunology*
  • Spleen / immunology
  • Th1 Cells / immunology*
  • Tumor Necrosis Factor-alpha / biosynthesis
  • Tumor Necrosis Factor-alpha / immunology
  • Urinary Bladder Neoplasms / immunology
  • Vaccines, Synthetic / immunology

Substances

  • BCG Vaccine
  • Epitopes
  • Interleukin-18
  • Tumor Necrosis Factor-alpha
  • Vaccines, Synthetic
  • Interleukin-10
  • Interleukin-12
  • Interferon-gamma
  • Granulocyte-Macrophage Colony-Stimulating Factor