Flu-induced stress response is critical for resistance to secondary infection

Feb 17, 2010

A new study reveals how infection with the influenza virus impacts the way that the immune system responds to subsequent infections. The research, published by Cell Press in the February 18th issue of the journal Cell Host and Microbe, provides a new understanding of the physiological and pathological consequences of the flu.

Much of what is known about how the immune system protects against infection comes from studies examining exposure to a single pathogen. However, in the natural environment, organisms are commonly exposed to multiple infectious agents at the same time, so it is important to determine how the host's response to one pathogen alters its response to another. This is particularly relevant for infection with influenza because it is often accompanied by secondary bacterial infections that are more lethal that the initial viral infection.

"Several studies have demonstrated that infection with influenza virus can result in a suppression of the immune system," explains senior study author, Dr. Ruslan Medzhitov from the Department of Immunology at the Yale University School of Medicine. "However, these studies focused primarily on the local effects of influenza at the site of infection. The effect of influenza virus infection on the systemic immune response is less well understood."

Dr. Medzhitov's group examined the effects of influenza virus on the subsequent systemic response to bacterial infection using a well characterized of bacterial infection. Infection with influenza resulted in a profound suppression of the systemic antibacterial immune response. Somewhat surprisingly, the researchers discovered that the influenza-associated immunosuppression was due to an increased production of glucocorticoids (GC). GCs are produced in response to stress and are known to play a key role in regulating inflammation.

The researchers went on to show that the virus-induced GC production was necessary to control inflammation. Importantly, although mice without GCs were better able to suppress the secondary bacterial infection and had a relatively normal response to infection with a single pathogen, the lack of GC production in the co-infected mice caused a lethal excessive inflammatory response.

The authors proposed that lung damage caused by infection with influenza triggered the stress response and GC production. "We have delineated a mechanism by which infection with virus, through the induction of GC, leads to suppression of the systemic immune response to a secondary ," says Dr. Medzhitov. "However, we also found that the induction of GC is critical for survival of co-infection."

Explore further: Report on viruses looks beyond disease

More information: Jamieson et al.: “Influenza Virus-Induced Glucocorticoids Compromise Innate Host Defense against a Secondary Bacterial Infection.” Publishing in Cell Host & Microbe 7, 103-114, February 18, 2010. DOI 10.1016/j.chom.2010.01.010

add to favorites email to friend print save as pdf

Related Stories

Double trouble: Bacterial super-infection after the flu

Jan 22, 2010

Current research suggests that the flu may predispose to secondary bacterial infections, which account for a significant proportion of mortality during flu pandemics. The related report by Lee et al, "A mouse model of lethal ...

Protein enhances lethality of influenza virus

Oct 10, 2007

Often called the most devastating epidemic in the recorded history of the world, the 1918 influenza virus pandemic was responsible for more than 40 million deaths across the globe. The incredible lethality of the 1918 flu ...

Scientists learn why the flu may turn deadly

May 04, 2009

As the swine flu continues its global spread, researchers from the Children's Hospital of Philadelphia, Pennsylvania, have discovered important clues about why influenza is more severe in some people than it is in others. ...

Bird flu leaves the nest -- adapting to a new host

Aug 26, 2009

Current research suggests that viral polymerase may provide a new therapeutic target for host-adapted avian influenza. The related report by Gabriel et al, "Spread of Infection and Lymphocyte Depletion in Mice Depends on ...

Your genes may hold key to how sick you get from the flu

Nov 03, 2006

With lessons from the 1918 flu pandemic in the rearview mirror and the avian flu a looming obstacle in the road ahead, researchers from Southern Illinois University School of Medicine are trying to understand why a flu virus ...

Recommended for you

Brand new technology detects probiotic organisms in food

42 minutes ago

In the food industr, ity is very important to ensure the quality and safety of products consumed by the population to improve their properties and reduce foodborne illness. Therefore, a team of Mexican researchers ...

Protein evolution follows a modular principle

1 hour ago

Proteins impart shape and stability to cells, drive metabolic processes and transmit signals. To perform these manifold tasks, they fold into complex three-dimensional shapes. Scientists at the Max Planck ...

Report on viruses looks beyond disease

19 hours ago

In contrast to their negative reputation as disease causing agents, some viruses can perform crucial biological and evolutionary functions that help to shape the world we live in today, according to a new report by the American ...

User comments : 0