Scientists have identified a rare genetic mutation that results in a markedly increased susceptibility to infection by human rhinoviruses (HRVs)--the main causes of the common cold. Colds contribute to more than 18,000,000,000 upper respiratory infections worldwide each year, according to the Global Burden of Disease Study.
Researchers at the National Institute of Allergy and Infectious Diseases identified the mutation in a young child with a history of severe HRV infections. A genetic analysis revealed that she had a mutation in the IFIH1 gene that caused her body to make dysfunctional MDA5 proteins in cells in her respiratory tract.
The researchers found that mutant MDA5 in the girl's respiratory tissues could not recognize HRVs, preventing her immune system from producing protective signaling proteins called interferons.
HRV thus replicated unchecked in the girl's respiratory tract, causing severe illness. These observations led the researchers to conclude that functional MDA5 is critical to protecting people against HRV. With intensive care, the child survived numerous bouts of severe illness, and her health improved as her immune system matured and formed protective antibodies against various infectious agents.
'The human immune response to common cold viruses is poorly understood," notes NIAID Director Anthony S. Fauci. "By investigating this unique case, our researchers not only helped this child but helped answer some important scientific questions about these ubiquitous infections that affect nearly everyone."
To explore whether other people experience poor health...