Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Fighting TB might be a matter of 'flipping a switch' in immune response

24.06.2009
Scientists are focusing on a new concept in fighting airborne pathogens by manipulating what is called the “switching time,” the point at which a highly regulated immune response gives way to powerful cells that specialize in fighting a specific invading bug.

In the case of tuberculosis, Ohio State University researchers are using mathematical modeling to determine whether a change to the natural switching time would result in a more effective immune response. They also are analyzing which parts of the immune response are most important to striking a balance between properly timing the switch and completing the task at hand – killing the microbe.

The complex modeling takes into account the huge assortment of cells and molecules at work in the human immune response to Mycobacterium tuberculosis, the microbe that causes TB. The response to all airborne pathogens is particularly complicated because it takes place in the highly protective environment of the lung. Human lungs are programmed to minimize immune responses as a way to avoid inflammation, which could interfere with breathing.

The modeling suggests that the average switching time occurs about 50 days after tuberculosis invades the lung, which roughly coincides with clinical expectations that a skin test will turn up positive for TB between four and eight weeks after infection.

By that time, bacteria have settled in and are harder to kill, even with the more robust immune response. Because TB is highly evolved and adapted to the human host, the launch of the stronger immune response goes unnoticed in about 90 percent of infections.

With less adapted but virulent pathogens, on the other hand, an individual becomes acutely ill, and sometimes dies, when the switching time occurs. As the immune response kicks into high gear, toxic infection-fighting warrior cells cause what could be considered collateral damage by harming lung tissue at the same time that they kill the invading bugs.

The researchers say mathematical models that predict relationships and interactions in the immune response could guide planning for therapies that would be designed to either accelerate or slow the switching time, depending on the pathogen.

“A great problem in developing drugs and vaccines against airborne pathogens is this apparent bottleneck in the immune response and the inability to quickly and effectively eradicate microbes in the lung environment,” said Larry Schlesinger, professor of internal medicine and director of the division of infectious diseases at Ohio State and a senior author of the study. “Understanding that bottleneck is an important part of this paper, and brings new insight into how to override the problem with tuberculosis and other pathogens.”

The research is scheduled to appear in the online early edition of the Proceedings of the National Academy of Sciences.

About 2 billion people worldwide are thought to be infected with TB. People who are infected can harbor the bacterium without symptoms for decades, but an estimated one in 10 will develop active disease characterized by a chronic cough and chest pain. Both active and latent infections are treated with a combination of antibiotics that patients take for at least six months.

In the event of infection, two immune responses occur: The innate immune response begins a fight against any pathogen. The acquired immune response follows, with components designed to attack the specific pathogen causing the infection. When that change occurs is referred to as the switching time.

At the point of infection in the lung, TB bacteria are absorbed by what are called alternatively activated macrophages. These macrophages activate specific molecules that make pieces of the bacteria visible to infection-fighting T cells, a process that triggers an eventual T-cell response and the recruitment of classically activated macrophages, those that are more effective at killing bacteria.

The mathematical modeling in this study simulates the entire cascade of events in the immune response to TB, setting the stage for testing what the outcome would be if changes were made along the way – for example, if a drug were developed to artificially inhibit or activate part of the process.

In this research, the scientists sought to determine what it would take to shorten the switching time and reduce the number of bacteria in the lung.

Two cytokines, interferon gamma and tumor necrosis factor alpha, are known participants in the conversion from one type of immune response to the other. Cytokines are proteins mobilized when the body is injured or has an infection, and often cause inflammation in their repair efforts.

Many previous studies testing interferon gamma’s potential as a TB therapy have suggested that the protein is effective in the fight, but isn’t effective enough on its own to treat the infection. The mathematical modeling simulating such a treatment reinforced these findings.

The model showed that early introduction of interferon gamma during the immune response would shorten the switching time and reduce the bacterial load, but would not completely clear bacteria from the lung after 100 days – a population referred to as the residual bacterial load. The researchers speculate that manually introducing one cytokine is not enough to optimize the signals needed to activate certain macrophages.

The findings suggest that interferon gamma might be one component of a cocktail approach to new TB therapies, the researchers said.

There would be a benefit to reducing that residual load of bacteria, Schlesinger noted. TB treatments take so long and currently require a cocktail of antibiotics specifically to address the long-term persistent bacteria in the lung and other parts of the body.

“If we could shorten the treatment for TB, that would be very powerful in breaking the transmission cycle,” said Schlesinger, also director of Ohio State’s Center for Microbial Interface Biology.

The precision of the modeling allows the researchers to simulate outcomes resulting from multiple tweaks to the values assigned to the various immune response activities.

“It’s like turning the knobs up and down on an equalizer, only in this case to figure out when the immune response and different mediators of that response are at the right levels to do their jobs – without blowing the speakers, so to speak,” said Judy Day, a postdoctoral researcher in Ohio State’s Mathematical Biosciences Institute and lead author of the study.

The researchers conducted a number of sensitivity tests to check the validity of the models. The models use what are considered ordinary differential equations, but finding the values to plug into those equations required an exhaustive search of previous research on tuberculosis.

“To pin down quantitatively what the effect of A is on B and C, we had to search the literature to find evidence of these parameters. When we didn’t find them, we had to make educated guesses and then subject them to sensitivity analysis,” said Avner Friedman, a senior author of the paper and Distinguished University Professor of mathematical and physical sciences at Ohio State.

Friedman, who was the founding director of the Mathematical Biosciences Institute, predicts this line of mathematical modeling of the immune response has paved the way for new research into combination therapies against a variety of pathogens.

“Switching time is a new concept. We will be talking about switching time in a few years about this disease, or that disease,” he said.

This research was supported by grants from the National Science Foundation and the National Institutes of Health.

Larry Schlesinger | EurekAlert!
Further information:
http://www.osumc.edu

More articles from Life Sciences:

nachricht Link Discovered between Immune System, Brain Structure and Memory
26.04.2017 | Universität Basel

nachricht Researchers develop eco-friendly, 4-in-1 catalyst
25.04.2017 | Brown University

All articles from Life Sciences >>>

The most recent press releases about innovation >>>

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

Im Focus: Making lightweight construction suitable for series production

More and more automobile companies are focusing on body parts made of carbon fiber reinforced plastics (CFRP). However, manufacturing and repair costs must be further reduced in order to make CFRP more economical in use. Together with the Volkswagen AG and five other partners in the project HolQueSt 3D, the Laser Zentrum Hannover e.V. (LZH) has developed laser processes for the automatic trimming, drilling and repair of three-dimensional components.

Automated manufacturing processes are the basis for ultimately establishing the series production of CFRP components. In the project HolQueSt 3D, the LZH has...

Im Focus: Wonder material? Novel nanotube structure strengthens thin films for flexible electronics

Reflecting the structure of composites found in nature and the ancient world, researchers at the University of Illinois at Urbana-Champaign have synthesized thin carbon nanotube (CNT) textiles that exhibit both high electrical conductivity and a level of toughness that is about fifty times higher than copper films, currently used in electronics.

"The structural robustness of thin metal films has significant importance for the reliable operation of smart skin and flexible electronics including...

Im Focus: Deep inside Galaxy M87

The nearby, giant radio galaxy M87 hosts a supermassive black hole (BH) and is well-known for its bright jet dominating the spectrum over ten orders of magnitude in frequency. Due to its proximity, jet prominence, and the large black hole mass, M87 is the best laboratory for investigating the formation, acceleration, and collimation of relativistic jets. A research team led by Silke Britzen from the Max Planck Institute for Radio Astronomy in Bonn, Germany, has found strong indication for turbulent processes connecting the accretion disk and the jet of that galaxy providing insights into the longstanding problem of the origin of astrophysical jets.

Supermassive black holes form some of the most enigmatic phenomena in astrophysics. Their enormous energy output is supposed to be generated by the...

Im Focus: A Quantum Low Pass for Photons

Physicists in Garching observe novel quantum effect that limits the number of emitted photons.

The probability to find a certain number of photons inside a laser pulse usually corresponds to a classical distribution of independent events, the so-called...

Im Focus: Microprocessors based on a layer of just three atoms

Microprocessors based on atomically thin materials hold the promise of the evolution of traditional processors as well as new applications in the field of flexible electronics. Now, a TU Wien research team led by Thomas Müller has made a breakthrough in this field as part of an ongoing research project.

Two-dimensional materials, or 2D materials for short, are extremely versatile, although – or often more precisely because – they are made up of just one or a...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

Expert meeting “Health Business Connect” will connect international medical technology companies

20.04.2017 | Event News

Wenn der Computer das Gehirn austrickst

18.04.2017 | Event News

7th International Conference on Crystalline Silicon Photovoltaics in Freiburg on April 3-5, 2017

03.04.2017 | Event News

 
Latest News

Scientist invents way to trigger artificial photosynthesis to clean air

26.04.2017 | Materials Sciences

Ammonium nitrogen input increases the synthesis of anticarcinogenic compounds in broccoli

26.04.2017 | Agricultural and Forestry Science

SwRI-led team discovers lull in Mars' giant impact history

26.04.2017 | Physics and Astronomy

VideoLinks
B2B-VideoLinks
More VideoLinks >>>