DEC 18, 2015 10:12 AM PST

Meta-Virus Signature Tells the Difference Between Viral and Bacterial Infections

WRITTEN BY: Kara Marker
The art of diagnosis will soon be fine-tuned; Stanford scientists identified a specific pattern of gene expression that differentiates between a viral infection and a bacterial infection.

When the body is invaded with a foreign pathogen, the immune system launches an attack based on what kind of pathogen is detected. In a groundbreaking study recently published in Immunity, scientists from the Stanford University Medical Center discovered the exact change in gene expression that occurs when a virus infects the body. Even more, they were also able to identify the gene expression change specifically associated with the influenza virus in comparison to other respiratory infections.

"It seems that when there is a viral infection, the immune system turns on a general response to all viruses, followed by a virus-specific response to the particular virus," said Purvesh Khatri, PhD, and senior author of the paper.

First, the team from Stanford studied blood samples from people who had either the flu, a cold, or respiratory syncytial virus (RSV). RSV is a common infection and causes cold-like symptoms (MedlinePlus). They identified 396 genes whose expression changed in a pattern unique across all of the blood samples regardless of virus type. 161 genes increased expression, and 235 decreased in expression.

Next, the took blood and tissue samples from a much larger group with a wider variety of conditions: healthy people, people with bacterial infections, and people with various viral infections. The same pattern of expression in the same 396 genes was seen only in people with viral infections, and they called this pattern the “meta-virus signature.”

The meta-virus signature specific to the flu contained a change in gene expression for just 11 genes, and the team was able to pinpoint a flu infection with this signature before symptoms occurred in an infected person.

"An individual's gene expression signature changed before they became sick, so we could predict up to 24 hours before who was going to show symptoms," said Khatri.

The study was motivated by the “long-term goal of finding broad-spectrum antiviral drugs, much like the broad-spectrum antibiotics that have saved so many people from deadly bacterial infections.” They also have funding to begin developing a clinical test for use in the doctor’s office to decide if antibiotics should be prescribed.

The team were also able to extrapolate their data to determine whether a person who had recently received a flu vaccine was responding appropriately and building immunity. Researchers can now use this meta-virus signature specific to the flu to see if vaccines are working like they should, revving up the immune system in preparation for a “real” infection.

"We have identified the common signature that links infection and vaccination," Khatri said.

Current studies using the influenza meta-virus signature have been successful, showing the same 11-gene expression change in people responding to a flu vaccine as people infected with the actual flu virus. The change does not occur in people who are not responding to the vaccine. 

Watch the following video to learn exactly what "genetic expression" means:

Source: Stanford University Medical Center 
About the Author
Master's (MA/MS/Other)
I am a scientific journalist and enthusiast, especially in the realm of biomedicine. I am passionate about conveying the truth in scientific phenomena and subsequently improving health and public awareness. Sometimes scientific research needs a translator to effectively communicate the scientific jargon present in significant findings. I plan to be that translating communicator, and I hope to decrease the spread of misrepresented scientific phenomena! Check out my science blog: ScienceKara.com.
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