Life-threatening pulmonary influenza can be caused by inborn errors of type I and III IFN immunity. We report a 5 year-old child with severe pulmonary influenza at 2 years. She is homozygous for a loss-of-function IRF9 allele. Her cells activate gamma-activated factor (GAF) STAT1 homodimers but not interferon-stimulated gene factor 3 (ISGF3) trimers (STAT1/STAT2/IRF9) in response to IFN-2b. The transcriptome induced by IFN-2b in the patients cells is much narrower than that of control cells; however, induction of a subset of interferon-stimulated gene transcripts remains detectable. In vitro, the patients cells do not control three respiratory viruses, influenza A virus (IAV), parainfluenza virus, and respiratory syncytial virus. These phenotypes are rescued by wild-type IRF9, whereas silencing IRF9 expression in control cells increases viral replication. However, the child has controlled various common viruses in vivo, including respiratory viruses other than IAV. Our findings show that human IRF9- and ISGF3-dependent type I and III IFN responsive pathways are essential for controlling IAV. SOURCE: Tanwir Habib Sidra Medicine

Pluto Bioinformatics

GSE117637: Life-threatening influenza pneumonitis in a child with inherited IRF9 deficiency