Cytokine networking in lungs of immunocompetent mice in response to inhaled Aspergillus fumigatus

Cytokine networking in the lung in response to inhaled Aspergillus fumigatu s was assessed using a murine model of primary pulmonary aspergillosis in i mmunocompetent Crl:CF-1 mice. Inhalation of virulent A. fumigatus (6 x 10(6 ) CFU) resulted in the induction of interleukin 18 (IL-18), tumor necrosis factor alpha (TNF-alpha), IL-12, and gamma interferon (IFN-gamma) protein i n bronchoalveolar lavage fluid and/or lung tissue. Induction of immunoreact ive IL-18 preceded induction of TNF-alpha protein, which preceded induction of immunoreactive IL-12 and IFN-gamma. Real-time reverse transcriptase (RT ) PCR analysis of infected lung tissue demonstrated that induction of IL-18 protein also preceded induction of pulmonary TNF-alpha, IL-12, and IFN-gam ma mRNAs. Mice were subsequently treated with cytokine-specific neutralizin g monoclonal antibodies (MAbs) to the IL-18 receptor (anti-IL-18R MAb), TNF -alpha (anti-TNF-alpha MAb), IL-12 (anti-IL-12 MAb), and/or IFN-gamma (anti -IFN-gamma MAb), and effects on intrapulmonary cytokine activity and growth of A. fumigatus were assessed in infected lung homogenates. Simultaneous n eutralization of IL-12 and IL-18 resulted in decreased levels of immunoreac tive TNF-alpha, while neutralization of IL-18, TNF-alpha, or IL-12 alone or of IL-18 and IL-12 together resulted in decreased levels of immunoreactive IFN-gamma. Simultaneous neutralization of IL-12 and IL-18 or neutralizatio n of TNF-a alone or in combination with IL-12, IL-18, or IFN-gamma also res ulted in a significant increase in A. fumigatus CFU in lung tissue. Taken t ogether, these results demonstrate that endogenous IL-18, IL-12, and TNF-al pha, through their modulatory effects on both intrapulmonary cytokine activ ity and growth of A. fumigatus, play key roles in host defense against prim ary pulmonary aspergillosis.