Recently, scientists had to analyze the case of a young girl who caught colds really often. This helped them realize there was a rare genetic mutation that caused people to be more prone to cold viruses in general.
The Case in Point
The case we were talking about refers to a 5-year-old girl who had suffered lots of infections that threatened her life, from the human rhinoviruses (the cause of the common cold). When she was just a 1-month-old baby, she got an infection developed both by a rhinovirus and a flu virus. She had to be helped to breathe, and ever since then, she had caught more than 15 respiratory infections, from common colds and flu to pneumonia.
A Mutation in the Genes
Seeing that there is no apparent solution, scientists have sequenced her own genome in order to see whether there was a genetic cause for all this. As such, they discovered that there was a mutation in her genes, called IFIH1. This mutation has a role in producing the immune system proteins named MDA5. Usually, the MDA5 proteins detect the presence of viruses in the cells and try and fight the infection.
In other studies they made on mice, scientists saw that organisms who lacked MDA5 proteins could not detect all the viruses and thus fight the respective infection. Consequently, they became more vulnerable to colds and other types of infections. In the girl’s case, the MDA5 proteins did not detect rhinoviruses, so they could replicate at very high levels and thus cause severe illnesses.
Thankfully, as the girl’s immune system grew up, her health also improved. Now she is able to form antibodies for various viruses, which protect her against various types of infections. As such, the antibodies compensate for the MDA5 response.