Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Dark Ages scourge enlightens modern struggle between man and microbes

14.12.2012
Scientists discover how Yersinia pestis avoids setting off immune system's early infection-alarm

The plague-causing bacteria Yersinia pestis evades detection and establishes a stronghold without setting off the body's early alarms.


Yersinia (gray) infects two macrophages. In the upper right pyroptosis was subverted via YopM, in the bottom left, pyroptosis is induced and an inflammasome is formed (white).

Credit: Brad Cookson lab

New discoveries reported this week help explain how the stealthy agent of Black Death avoids tripping a self-destruct mechanism inside germ-destroying cells.

The authors of the study, appearing in the Dec. 13 issue of Cell Host & Microbe, are Dr. Christopher N. LaRock of the University of Washington Department of Microbiology and Dr. Brad Cookson, UW professor of microbiology and laboratory medicine.

Normally, certain defender cells are programmed to burst if they are either invaded by or detect the presence of pathogens, Cookson explained. This host defense mechanism called pyroptosis ("going up in flames") eliminates places for the germs to reproduce. As it splits open, the cell spills a cauldron of antimicrobial chemicals and emits signals to alert of an attack and its precise location. Tissues become inflamed as more cells arrive to fight the infection.

The bacteria are widely believed to be behind the great pestilences of the Middle Ages in the 1300s. The pathogen had evolved a tactic to delay provoking people's protective inflammatory response until it was too late. Plague claimed an estimated 30 percent to 50 percent of Europe's 14th century population.

"People and pathogens have been in an eternal struggle since the dawn of humanity," Cookson said. With a hand over hand gesture he explained, "Humans continuously ratchet up their defenses, and germs repeatedly find a way around them."

During several medieval epidemics, the plague started in rats. High-jumping fleas transmitted it to and between humans. It commonly caused lymph nodes to rupture. Respiratory forms were more deadly. They damaged the lungs and were spread by sneezing. Plague bacteria in the blood stream ended lives through sepsis, in which the burden of infection overwhelms the body.

Today, the plague-causing bacteria are still circulating in the world. It is held at bay by sanitation measures and drug treatment.

Plague is now rare, with fewer than 15 infections annually in the United States. The number of cases outside the United States is significantly larger, but not precisely known. Plague therefore remains of scientific interest for several reasons.

The Yersinia survival strategy against the programmed death that could kill it and its host cell may offer ideas for vaccine development, Cookson said. At present, no vaccine exists against the plague. Yesinia is of concern as a potential biological warfare pathogen because it can be aerosolized and unsuspectingly breathed into the lungs. Vaccines are being sought to offer widespread public safety, as are methods for enhancing people's overall infection-fighting capacity.

Yersinia's techniques for modulating an inflammatory response also offer scientists an overarching perspective on a fundamental aspect of a variety of important diseases.

"Many medical problems stem from too much or too little inflammatory reaction," Cookson said. People who launch an insufficient inflammatory response, or whose inflammatory response is suppressed by medications, are prone to viral, bacterial and fungal infections.

"On the other hand, excessive or improperly regulated inflammatory responses are responsible for a large number of chronic conditions," Cookson said. These include vascular flare-ups leading to stroke or heart attack, and autoimmune diseases, among them lupus, juvenile diabetes, ulcerative colitis and myasthenia gravis. Severe injury also can promote life-threatening lung inflammation.

Additionally, plague isn't the only pathogen to enhance its virulence by sidestepping the inflammatory cell death program. Several other dangerous germs do the same, but in different ways.

Usually immune system clean-up cells that have been breached by an infection assemble a molecular platform called an inflammasome. This assembly, the researchers explained, activates a powerful, protein-cleaving enzyme called caspase-1. The enzyme is made ready to go in the presence of noxious stimuli, including germs, inorganic irritants, and pore-forming toxins.

To survive, Yersinia pestis must disarm caspase-1. Until the present study, bacterial molecules that directly modulate the inflammasome had not yet been reported. LaRock and Cookson were able to identify a leucine-rich protein secreted by Yersinia pestis that binds and disables its arch-enemy, the caspase-1 enzyme.

The potent substance, called Yop M, preempts the activity of caspase-1 and sequesters the enzyme to arrest the development of the inflammasome. As a consequence, the cell fails to sacrifice itself to get rid of the Yersinia and to warn other disease-fighting cells of the infection.

According to the researchers, the Yop M-mediated inhibition of caspase-1 is required for Yersinia to subvert immune signaling, delay inflammation and provoke severe illness. Its dual mechanism for blocking inflammatory cell death, by blocking enzymatic activity and inflammasome maturation, is distinctive.

While caspase-1 is helpful in combating a number of other microbial infections, several researchers have reported it to be harmful when its activation is aberrant or poorly controlled. Faulty caspase-1 regulation is implicated in several inflammatory disorders. Learning how pathogens manage caspase-1 to their advantage may suggest treatments to limiting its excess activity.

The research was funding by National Institutes of Health research grants HG02360 and AI057141 and National Institute of Health training grant AI055396. The study also received assistance from the Northwest Regional Center of Excellence for Biodefense and Emerging Infectious Diseases, which seeks countermeasures against pathogens of national importance.

The Dec. 13 Cell Host & Microbe paper is "The Yersinia Virulence Effector YopM Binds Caspase-1 to Arrest Inflammasome Assembly and Processing."

Leila Gray | EurekAlert!
Further information:
http://www.uw.edu

More articles from Life Sciences:

nachricht Modern genetic sequencing tools give clearer picture of how corals are related
17.08.2017 | University of Washington

nachricht The irresistible fragrance of dying vinegar flies
16.08.2017 | Max-Planck-Institut für chemische Ökologie

All articles from Life Sciences >>>

The most recent press releases about innovation >>>

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

Im Focus: Fizzy soda water could be key to clean manufacture of flat wonder material: Graphene

Whether you call it effervescent, fizzy, or sparkling, carbonated water is making a comeback as a beverage. Aside from quenching thirst, researchers at the University of Illinois at Urbana-Champaign have discovered a new use for these "bubbly" concoctions that will have major impact on the manufacturer of the world's thinnest, flattest, and one most useful materials -- graphene.

As graphene's popularity grows as an advanced "wonder" material, the speed and quality at which it can be manufactured will be paramount. With that in mind,...

Im Focus: Exotic quantum states made from light: Physicists create optical “wells” for a super-photon

Physicists at the University of Bonn have managed to create optical hollows and more complex patterns into which the light of a Bose-Einstein condensate flows. The creation of such highly low-loss structures for light is a prerequisite for complex light circuits, such as for quantum information processing for a new generation of computers. The researchers are now presenting their results in the journal Nature Photonics.

Light particles (photons) occur as tiny, indivisible portions. Many thousands of these light portions can be merged to form a single super-photon if they are...

Im Focus: Circular RNA linked to brain function

For the first time, scientists have shown that circular RNA is linked to brain function. When a RNA molecule called Cdr1as was deleted from the genome of mice, the animals had problems filtering out unnecessary information – like patients suffering from neuropsychiatric disorders.

While hundreds of circular RNAs (circRNAs) are abundant in mammalian brains, one big question has remained unanswered: What are they actually good for? In the...

Im Focus: RAVAN CubeSat measures Earth's outgoing energy

An experimental small satellite has successfully collected and delivered data on a key measurement for predicting changes in Earth's climate.

The Radiometer Assessment using Vertically Aligned Nanotubes (RAVAN) CubeSat was launched into low-Earth orbit on Nov. 11, 2016, in order to test new...

Im Focus: Scientists shine new light on the “other high temperature superconductor”

A study led by scientists of the Max Planck Institute for the Structure and Dynamics of Matter (MPSD) at the Center for Free-Electron Laser Science in Hamburg presents evidence of the coexistence of superconductivity and “charge-density-waves” in compounds of the poorly-studied family of bismuthates. This observation opens up new perspectives for a deeper understanding of the phenomenon of high-temperature superconductivity, a topic which is at the core of condensed matter research since more than 30 years. The paper by Nicoletti et al has been published in the PNAS.

Since the beginning of the 20th century, superconductivity had been observed in some metals at temperatures only a few degrees above the absolute zero (minus...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

Call for Papers – ICNFT 2018, 5th International Conference on New Forming Technology

16.08.2017 | Event News

Sustainability is the business model of tomorrow

04.08.2017 | Event News

Clash of Realities 2017: Registration now open. International Conference at TH Köln

26.07.2017 | Event News

 
Latest News

Gold shines through properties of nano biosensors

17.08.2017 | Physics and Astronomy

Greenland ice flow likely to speed up: New data assert glaciers move over sediment, which gets more slippery as it gets wetter

17.08.2017 | Earth Sciences

Mars 2020 mission to use smart methods to seek signs of past life

17.08.2017 | Physics and Astronomy

VideoLinks
B2B-VideoLinks
More VideoLinks >>>