Mechanism that prevents lethal bacteria from causing invasive disease revealed

July 7, 2014

An important development in understanding how the bacterium that causes pneumonia, meningitis and septicaemia remains harmlessly in the nose and throat has been discovered at the University of Liverpool's Institute of Infection and Global Health.

Streptococcus pneumoniae is a 'commensal', which can live harmlessly in the nasopharynx as part of the body's natural bacterial flora. However, in the very young and old it can invade the rest of the body, leading to serious diseases such as pneumonia, sepsis and meningitis, which claim up to a million lives every year worldwide.

However, the conditions that drive this bacterium from harmless commensal to major pathogen are not understood.

Scientists at the University have now uncovered the mechanisms by which this occurs and how it is regulated by the host immune system.

They found that a specialised group of white blood cells called T are activated by the pneumococcus and move to dampen down a damaging pro-inflammatory response from the host immune system.

When attack bacteria they cause inflammation and, if this inflammation is uncontrolled it can become excessive and damage host tissues, allowing the bacteria to spread into the rest of the respiratory system and other organs in the body.

The first author of the study, immunologist Dr Daniel Neill said: "These bacteria are quite happy to live in your nose and it's not in their interests to spread and kill their host. This is why they activate T regulatory cells: to keep the immune system in check and ensure their own survival.

"Our findings suggest induction of T regulatory cell responses in the upper airways reduces the risk of inflammatory damage that could lead to bacterial invasion and the development of disease.

"Understanding this process can now lead us to investigate how the bacteria go from this state to causing lethal infections."

The senior author of the study, Professor Aras Kadioglu said: "Vaccines are an essential part of our fight against this disease and have been highly successful.

"However, they do not protect us against all strains of pneumococci. Therefore, understanding the key immunological interactions with the pneumococcus, in the very first site they enter and colonise the human body is crucial to future development of better vaccines.

"In this study we have revealed how there is a delicate balance between the ability of the to colonise the host nasopharynx and the critical need of the immune system to prevent damaging inflammation in this key site.

"We hope that this will lead to developing novel therapies based on modulating the host to prevent subsequent invasive disease."

The paper 'Density and Duration of Pneumococcal Carriage Is Maintained by Transforming Growth Factor b1 and T Regulatory Cells', was published in the American Journal of Respiratory and Critical Care Medicine.

Explore further: How localized bacterial infections can turn into dangerous sepsis

Related Stories

How localized bacterial infections can turn into dangerous sepsis

March 20, 2014
We carry numerous bacteria on our skin, in our mouth, gut, and other tissues, and localized bacterial infections are common and mostly not harmful. Occasionally, however, a localized infection turns into dangerous systemic ...

Researchers identify unforeseen regulation of the anti-bacterial immune response

August 28, 2012
New research from the laboratory of Dr. Andrea Cooper at the Trudeau Institute, just published in the European Journal of Immunology, holds promise for the improved prevention and treatment of bacterial infections and the ...

Scientists uncover two micro mechanisms that regulate immune system

February 26, 2014
A Keck Medicine of USC-led team of microbiologists has identified previously unknown interactions between critical proteins in the human immune response system, uncovering two independent regulatory mechanisms that keep the ...

Scientists pinpoint key ingredient in fighting pneumonia

July 19, 2012
(Medical Xpress) -- A mysterious protein produced by a wide spectrum of living things is crucial in regulating the immune response to the most common form of pneumonia, a new Yale School of Medicine study shows. The study ...

Recommended for you

Molecular hitchhiker on human protein signals tumors to self-destruct

July 24, 2017
Powerful molecules can hitch rides on a plentiful human protein and signal tumors to self-destruct, a team of Vanderbilt University engineers found.

Researchers develop new method to generate human antibodies

July 24, 2017
An international team of scientists has developed a method to rapidly produce specific human antibodies in the laboratory. The technique, which will be described in a paper to be published July 24 in The Journal of Experimental ...

New vaccine production could improve flu shot accuracy

July 24, 2017
A new way of producing the seasonal flu vaccine could speed up the process and provide better protection against infection.

A sodium surprise: Engineers find unexpected result during cardiac research

July 20, 2017
Irregular heartbeat—or arrhythmia—can have sudden and often fatal consequences. A biomedical engineering team at Washington University in St. Louis examining molecular behavior in cardiac tissue recently made a surprising ...

Want to win at sports? Take a cue from these mighty mice

July 20, 2017
As student athletes hit training fields this summer to gain the competitive edge, a new study shows how the experiences of a tiny mouse can put them on the path to winning.

'Smart' robot technology could give stroke rehab a boost

July 19, 2017
Scientists say they have developed a "smart" robotic harness that might make it easier for people to learn to walk again after a stroke or spinal cord injury.

0 comments

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.