Title Recurrent rhinovirus infections in a child with inherited MDA5 deficiency.
Author Lamborn, Ian T; Jing, Huie; Zhang, Yu; Drutman, Scott B; Abbott, Jordan K; Munir, Shirin; Bade, Sangeeta; Murdock, Heardley M; Santos, Celia P; Brock, Linda G; Masutani, Evan; Fordjour, Emmanuel Y; McElwee, Joshua J; Hughes, Jason D; Nichols, Dave P; Belkadi, Aziz; Oler, Andrew J; Happel, Corinne S; Matthews, Helen F; Abel, Laurent; Collins, Peter L; Subbarao, Kanta; Gelfand, Erwin W; Ciancanelli, Michael J; Casanova, Jean-Laurent; Su, Helen C
Journal J Exp Med Publication Year/Month 2017-Jul
PMID 28606988 PMCID PMC5502429
Affiliation + expend 1.Laboratory of Host Defenses, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, MD.

MDA5 is a cytosolic sensor of double-stranded RNA (ds)RNA including viral byproducts and intermediates. We studied a child with life-threatening, recurrent respiratory tract infections, caused by viruses including human rhinovirus (HRV), influenza virus, and respiratory syncytial virus (RSV). We identified in her a homozygous missense mutation in IFIH1 that encodes MDA5. Mutant MDA5 was expressed but did not recognize the synthetic MDA5 agonist/(ds)RNA mimic polyinosinic-polycytidylic acid. When overexpressed, mutant MDA5 failed to drive luciferase activity from the IFNB1 promoter or promoters containing ISRE or NF-kappaB sequence motifs. In respiratory epithelial cells or fibroblasts, wild-type but not knockdown of MDA5 restricted HRV infection while increasing IFN-stimulated gene expression and IFN-beta/lambda. However, wild-type MDA5 did not restrict influenza virus or RSV replication. Moreover, nasal epithelial cells from the patient, or fibroblasts gene-edited to express mutant MDA5, showed increased replication of HRV but not influenza or RSV. Thus, human MDA5 deficiency is a novel inborn error of innate and/or intrinsic immunity that causes impaired (ds)RNA sensing, reduced IFN induction, and susceptibility to the common cold virus.

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