Colds and flu

26 March 2012

Why some people battle with flu

A genetic discovery could help explain why flu makes some people seriously ill or kills them, while others seem able to have little more than a few aches, coughs and sneezes.

0

A genetic discovery could help explain why flu makes some people seriously ill or kills them, while others seem able to bat it away with little more than a few aches, coughs and sneezes.

In a study published in the journal Nature, British and American researchers said they had found for the first time a human gene that influences how people respond to flu infections, making some people more susceptible than others.

The finding helps explain why during the 2009/2010 pandemic of H1N1 or "swine flu", the vast majority of people infected had only mild symptoms, while others - many of them healthy young adults - got seriously ill and died.

In future, the genetic discovery could help doctors screen patients to identify those more likely to be brought down by flu, allowing them to be selected for priority vaccination or preventative treatment during outbreaks, the researchers said.

It could also help develop new vaccines or medicines against potentially more dangerous viruses such as bird flu.

What the research found

Paul Kellam of Britain's Sanger Institute, who co-led the study, said the gene, called ITFITM3, appeared to be a "crucial first line of defence" against flu.

When IFITM3 was present in large quantities, the spread of the virus in lungs was hindered, he explained. But when IFITM3 levels were lower, the virus could replicate and spread more easily, causing more severe symptoms.

People who carried a particular variant of IFTIM3 were far more likely to be taken into hospital when they got flu than people who carried other variants, he added.

"Our research is important for people who have this variant as we predict their immune defences could be weakened to some virus infections," Kellam said.

"Ultimately as we learn more about the genetics of susceptibility to viruses, then people can take informed precautions, such as vaccination to prevent infection."

Studies done in mice

The potential antiviral role of IFITM3 in humans was first suggested in studies conducted by Abraham Brass of the Ragon Institute and Gastrointestinal Unit of Massachusetts General Hospital in the United States. Using genetic screening, he found that it blocked the growth of flu and other viruses in cells.

Teams led by Brass and Kellam then took the work further by knocking out the IFITM3 gene in mice. They found that once these animals contracted flu they had far more severe symptoms than mice with the IFITM3 gene.

In effect, they said, the loss of this single gene in mice can turn a mild case of influenza into a fatal infection.

The researchers then sequenced the IFITM3 genes of 53 patients who had been hospitalised with seasonal or pandemic flu and found that a higher number of them had a particular variant of IFITM3 compared to the general patient population.

The researchers believe this variant results in a shorter version of the protein or one that is less abundant in cells, leaving patients more vulnerable to flu when they get it.

"Our efforts suggest that individuals and populations with less IFITM3 activity may be at increased risk during a pandemic, and that IFITM3 could be vital for defending human populations against other viruses such as avian influenza," said Brass. - (AP, March 2012)

Read more:
The age of killer germs
Cold or the flu?

 

Read Health24’s Comments Policy

Comment on this story
0 comments
Comments have been closed for this article.

Ask the Expert

Flu expert

Dr Heidi van Deventer completed her MBChB (Bachelor of Medicine and Bachelor of Surgery) degree in 2004 at the University of Stellenbosch.
She has additional training in ACLS (Advanced Cardiac Life Support) and PALS (Paediatric Advanced Life Support) as well as biostatistics and epidemiology.

Dr Van Deventer is currently working as a researcher at the Desmond Tutu Tuberculosis Centre at the University of Stellenbosch.

Still have a question?

Get free advice from our panel of experts

The information provided does not constitute a diagnosis of your condition. You should consult a medical practitioner or other appropriate health care professional for a physical exmanication, diagnosis and formal advice. Health24 and the expert accept no responsibility or liability for any damage or personal harm you may suffer resulting from making use of this content.

* You must accept our condition

Forum Rules