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STAT1 signaling within macrophages is required for antifungal activity against Cryptococcus neoformans

Chrissy M Leopold Wager1, Camaron R Hole1, Karen L Wozniak1

  • 1Department of Biology, The University of Texas at San Antonio, San Antonio, Texas, USA The South Texas Center for Emerging Infectious Diseases, The University of Texas at San Antonio, San Antonio, Texas, USA.

Infection and Immunity
|September 10, 2015
PubMed

Insights

Signal transducer and activator of transcription 1 (STAT1) activation in macrophages is crucial for controlling Cryptococcus neoformans infection. STAT1 promotes nitric oxide (NO) production, essential for macrophage anti-fungal activity.

Area of Science:

  • Immunology
  • Mycology
  • Infectious Diseases

Background:

  • Cryptococcus neoformans causes life-threatening meningoencephalitis in immunocompromised individuals.
  • Protection against pulmonary C. neoformans infection involves T helper 1 (Th1) responses and STAT1-mediated M1 macrophage activation.
  • The precise mechanism of M1 macrophage anti-fungal activity against C. neoformans is not fully understood.

Purpose of the Study:

  • To elucidate the role of STAT1 in macrophage-mediated anti-cryptococcal activity.
  • To determine the mechanism by which M1 macrophages control C. neoformans infection.

Main Methods:

  • Mice with macrophage-specific STAT1 ablation were infected with C. neoformans strain H99γ.
  • Analysis of pulmonary inflammation, immune response (Th1/Th2), fungal burden, and M1 macrophage activation.
  • Assessment of nitric oxide (NO) and reactive oxygen species (ROS) production in STAT1-deficient and inducible nitric oxide synthase (iNOS) knockout macrophages.

Main Results:

  • Macrophage-specific STAT1 ablation led to increased pulmonary inflammation, dysregulated immune responses, higher fungal burden, and impaired M1 activation.
  • STAT1-deficient macrophages produced less NO and failed to control intracellular C. neoformans proliferation, despite intact ROS production.
  • Macrophages from iNOS knockout mice also showed deficient anti-cryptococcal activity, even with normal ROS production.

Conclusions:

  • STAT1 activation in macrophages is essential for M1 macrophage activation and anti-C. neoformans activity.
  • Nitric oxide (NO) production, driven by STAT1, is the critical mechanism for controlling intracellular C. neoformans proliferation.
  • STAT1-dependent NO generation by M1 macrophages is vital for host defense against pulmonary cryptococcosis.

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