Primary immunodeficiencies are often monogenic disorders characterized by vulnerability to specific infectious pathogens. Here, we performed whole-exome sequencing of a patient with disseminated Mycobacterium abscessus, Streptococcus viridians bacteremia, and cytomegalovirus (CMV) viremia and identified mutations in 2 genes that regulate distinct IFN pathways. The patient had a homozygous frameshift deletion in IFNGR2, which encodes the signal transducing chain of the IFN-γ receptor, that resulted in minimal protein expression and abolished downstream signaling. The patient also harbored a homozygous deletion in IFNAR1 (IFNAR1*557Gluext*46), which encodes the IFN-α receptor signaling subunit. The IFNAR1*557Gluext*46 resulted in replacement of the stop codon with 46 additional codons at the C-terminus. The level of IFNAR1*557Gluext*46 mutant protein expressed in patient fibroblasts was comparable to levels of WT IFNAR1 in control fibroblasts. IFN-α–induced signaling was impaired in the patient fibroblasts, as evidenced by decreased STAT1/STAT2 phosphorylation, nuclear translocation of STAT1, and expression of IFN-α–stimulated genes critical for CMV immunity. Pretreatment with IFN-α failed to suppress CMV protein expression in patient fibroblasts, whereas expression of WT IFNAR1 restored IFN-α–mediated suppression of CMV. This study identifies a human IFNAR1 mutation and describes a digenic immunodeficiency specific to type I and type II IFNs.
Rodrigo Hoyos-Bachiloglu, Janet Chou, Catherine N. Sodroski, Abdallah Beano, Wayne Bainter, Magdalena Angelova, Eman Al Idrissi, Murad K. Habazi, Hamza Ali Alghamdi, Fahd Almanjomi, Mohamed Al Shehri, Nagi Elsidig, Morsi Alaa Eldin, David M. Knipe, Mofareh AlZahrani, Raif S. Geha
IFNGR2C266fs has minimal protein expression and abrogates downstream signaling.