Interferon Alpha Treatment of Patients with Impaired Interferon Gamma Signaling

Patients with deficiency in the interferon gamma receptor (IFN-gamma R) are unable to respond properly to IFN-gamma and develop severe infections with nontuberculous mycobacteria (NTM). IFN-gamma and IFN-alpha are known to signal through STAT1 and activate many downstream effector genes in common. Therefore, we added IFN-alpha for treatment of patients with disseminated mycobacterial disease in an effort to complement their IFN-gamma signaling defect. We treated four patients with IFN-gamma R deficiency with adjunctive IFN-alpha therapy in addition to best available antimicrobial therapy, with or without IFN-gamma, depending on the defect. During IFN-alpha treatment, ex vivo induction of IFN target genes was detected. In addition, IFN-alpha driven gene expression in patients' cells and mycobacteria induced cytokine response were observed in vitro. Clinical responses varied in these patients. IFN-alpha therapy was associated with either improvement or stabilization of disease. In no case was disease exacerbated. In patients with profoundly impaired IFN-gamma signaling who have refractory infections, IFN-alpha may have adjunctive anti-mycobacterial effects

A 38-year-old woman with necrotising cervical lymphadenitis due to Histoplasma capsulatum

Immunogenetics and cellular immunology of bacterial infectious disease

Signal transducer and activator of transcription 1 (STAT1) gain-of-function mutations and disseminated coccidioidomycosis and histoplasmosis

Background: Impaired signaling in the IFN-gamma/IL-12 pathway causes susceptibility to severe disseminated infections with mycobacteria and dimorphic yeasts. Dominant gain-of-function mutations in signal transducer and activator of transcription 1 (STAT1) have been associated with chronic mucocutaneous candidiasis. Objective: We sought to identify the molecular defect in patients with disseminated dimorphic yeast infections. Methods: PBMCs, EBV-transformed B cells, and transfected U3A cell lines were studied for IFN-gamma/IL-12 pathway function. STAT1 was sequenced in probands and available relatives. Interferon-induced STAT1 phosphorylation, transcriptional responses, protein-protein interactions, target gene activation, and function were investigated. Results: We identified 5 patients with disseminated Coccidioides immitis or Histoplasma capsulatum with heterozygous missense mutations in the STAT1 coiled-coil or DNA-binding domains. These are dominant gain-of-function mutations causing enhanced STAT1 phosphorylation, delayed dephosphorylation, enhanced DNA binding and transactivation, and enhanced interaction with protein inhibitor of activated STAT1. The mutations caused enhanced IFN-gamma-induced gene expression, but we found impaired respo Conclusion: Gain-of-function mutations in STAT1 predispose to invasive, severe, disseminated dimorphic yeast infections, likely through aberrant regulation of IFN-gamma-mediated inflammation