Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Study By UCSD Researchers Gives New Insight Into How Anthrax Bacteria Can Evade A Host’s Immune Response

07.01.2004


Biologists at the University of California, San Diego have determined how toxin produced by anthrax bacteria blocks a person’s normal immune response, a discovery that could lead to new treatments for anthrax infection.



In a paper to be published in the January 15th issue of The Journal of Immunology the UCSD scientists show why, in the presence of anthrax toxin, human immune cells fail to respond normally to lipopolysaccharide—a component of the cell walls of many bacteria including the bacteria that cause anthrax, Bacillus anthracis. Bacterial invasion, or the presence of lipopolysaccharide, usually causes immune cells known as macrophages to release cytokines—chemicals that signal other cells about the presence of an invader. Release of cytokines causes large numbers of immune cells to arrive at the site of infection and destroy the bacteria. By blocking this host immune response, anthrax bacteria are able to multiply unchecked. According to the Centers for Disease Control, approximately 75 percent of people infected with inhalation anthrax die, even with all possible supportive care including appropriate antibiotics.

“Although it was known for quite some time that anthrax toxins can suppress cytokine production, the mechanism by which Bacillus anthracis escapes the immune response isn’t really understood,” says Michael David, a biology professor at UCSD who headed the research team. “We have identified a protein molecule targeted by the anthrax toxin and determined where it acts in the sequence of steps involved in immune response.”


Macrophages have special receptors on their surfaces that bind to lipopolysaccharide. The binding of lipopolysaccharide to this receptor sets off a sequence of events inside the macrophage, in which a series of proteins activate one another in turn. This cascade of proteins activating one another ultimately turns on cytokine genes, causing the macrophage to churn out large quantities of cytokines.

It turns out that there are two separate, sometimes cooperating, routes in the cell by which series of proteins activate one another to switch on production of cytokines. One of the routes has been recognized for a long time, but researchers were sometimes puzzled when cytokine production was turned on or off without the proteins along this route being activated or deactivated. This puzzle was resolved when the David group and other groups simultaneously identified the second route, the IRF3 pathway. The anthrax toxin targets the IRF3 pathway by cleaving MKK6—one of the proteins in the series along the route. The cleavage of MKK6 prevents the cytokine genes from being switched on.

When the researchers made mutant macrophages with a variant of MKK6 that could not be cleaved by the anthrax toxin, these macrophages responded to lipopolysaccharide by producing cytokines even in the presence of the anthrax toxin. This suggests that developing a drug that could protect MKK6 and prevent anthrax toxin from cleaving it could help to prevent an anthrax infection from getting out of control. The anthrax bacteria would be unable to evade the normal immune response.

“While these results may not lead to a drug to cure anthrax in the next six months, the more you understand about bacteria and how they target the immune response the more options you have for developing drugs to treat the infections,” says David.

Previous work by other researchers has suggested that anthrax toxin evades the immune system by killing macrophages; however, according to David, cell death does not fully explain how anthrax bacteria evade the immune system.

“Only some types of macrophages are killed by anthrax toxins, but anthrax toxins diminish the production of cytokines in all of the macrophages we have tested,” David explains. “Also, less toxin is needed to shut off the immune response than to kill the macrophages.”

The other UCSD researchers involved with this project were Oanh Dang, a former graduate student in the David laboratory and the first author of the paper; Lorena Navarro, a former graduate student in the David laboratory and first author on two other papers that initially identified the IRF3 immune response pathway; and Keith Anderson, a technician in the David laboratory. This work was supported by a grant from the National Institutes of Health.


Media Contacts: Sherry Seethaler (858) 534-4656
Comment: Michael David (858) 822-1108

Sherry Seethaler | UC - San Diego
Further information:
http://ucsdnews.ucsd.edu/newsrel/science/santhrax.asp

More articles from Life Sciences:

nachricht New eDNA technology used to quickly assess coral reefs
18.04.2019 | University of Hawaii at Manoa

nachricht New automated biological-sample analysis systems to accelerate disease detection
18.04.2019 | Polytechnique Montréal

All articles from Life Sciences >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: Explosion on Jupiter-sized star 10 times more powerful than ever seen on our sun

A stellar flare 10 times more powerful than anything seen on our sun has burst from an ultracool star almost the same size as Jupiter

  • Coolest and smallest star to produce a superflare found
  • Star is a tenth of the radius of our Sun
  • Researchers led by University of Warwick could only see...

Im Focus: Quantum simulation more stable than expected

A localization phenomenon boosts the accuracy of solving quantum many-body problems with quantum computers which are otherwise challenging for conventional computers. This brings such digital quantum simulation within reach on quantum devices available today.

Quantum computers promise to solve certain computational problems exponentially faster than any classical machine. “A particularly promising application is the...

Im Focus: Largest, fastest array of microscopic 'traffic cops' for optical communications

The technology could revolutionize how information travels through data centers and artificial intelligence networks

Engineers at the University of California, Berkeley have built a new photonic switch that can control the direction of light passing through optical fibers...

Im Focus: A long-distance relationship in femtoseconds

Physicists observe how electron-hole pairs drift apart at ultrafast speed, but still remain strongly bound.

Modern electronics relies on ultrafast charge motion on ever shorter length scales. Physicists from Regensburg and Gothenburg have now succeeded in resolving a...

Im Focus: Researchers 3D print metamaterials with novel optical properties

Engineers create novel optical devices, including a moth eye-inspired omnidirectional microwave antenna

A team of engineers at Tufts University has developed a series of 3D printed metamaterials with unique microwave or optical properties that go beyond what is...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

VideoLinks
Industry & Economy
Event News

Revered mathematicians and computer scientists converge with 200 young researchers in Heidelberg!

17.04.2019 | Event News

First dust conference in the Central Asian part of the earth’s dust belt

15.04.2019 | Event News

Fraunhofer FHR at the IEEE Radar Conference 2019 in Boston, USA

09.04.2019 | Event News

 
Latest News

New automated biological-sample analysis systems to accelerate disease detection

18.04.2019 | Life Sciences

Explosion on Jupiter-sized star 10 times more powerful than ever seen on our sun

18.04.2019 | Physics and Astronomy

New eDNA technology used to quickly assess coral reefs

18.04.2019 | Life Sciences

VideoLinks
Science & Research
Overview of more VideoLinks >>>