A rare genetic mutation may explain why a small number of otherwise healthy children require hospitalization for severe influenza disease, reports a new case study appearing in the journal Science.

Jean-Laurent Casanova, MD, PhD, of Rockefeller University, and colleagues describe a female patient who developed acute respiratory distress syndrome (ARDS) after infection with confirmed pandemic H1N1 (pH1N1) 2009 influenza A virus (IAV) in January 2011. The patient did not suffer from severe infections caused by other viruses, comorbidities, or immunological abnormalities suggestive of any T- or B-cell deficit and was not vaccinated against influenza strains.

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Whole exome sequencing (WES) was performed on the patient at age 7, wherein the scientists discovered two differently mutated copies of the gene IRF7 that encodes a protein which increases interferon production. After infecting a sample of her plasmacytoid dendritic cells, no interferon was detected. When cells samples from her parents were infected, healthy amounts of interferon were produced when exposed to influenza. Because each of the parents carried only one mutated version of the gene, the researchers concluded that a single non-mutated copy of the gene is sufficient for immune response to the virus.

Annual immunization against influenza has so far prevented the occurrence of severe symptoms in the patient and she had not experienced the same severe illness from other viral infections, which suggests that the lack of IRF7-dependent interferon may not significantly increase her vulnerability to all viruses. Treatment of severe influenza disease in patients with this genetic mutation could include interferon, suggests Dr. Casanova.

For more information visit Rockefeller.edu.