Scientists Discover Rare Genetic Susceptibility to Common Cold

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 billion upper respiratory infections worldwide each year, according to the Global Burden of Disease Study.

Researchers at NIAID identified the mutation in a young child with a history of severe HRV infections. The case, published online June 12 in the Journal of Experimental Medicine, reveals an important mechanism by which the immune system responds to these viruses, say the study authors.

Several weeks after birth, the child began experiencing life-threatening respiratory infections, including colds, influenza and bacterial pneumonia. Because her physicians suspected she might have a primary immune deficiency—a genetic abnormality affecting her immune system—they performed a genetic analysis.

The 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.

Previously, scientists had found that laboratory mice lacking functional MDA5 could not detect genetic material from several viruses, making them unable to launch appropriate immune responses against them.

Similarly, the NIH 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,” said NIAID director Dr. Anthony Fauci. “By investigating this unique case, our researchers not only helped this child but also helped answer some important scientific questions about these ubiquitous infections that affect nearly everyone.”