Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Immune system's bare essentials used to speedily detect drug targets

01.11.2010
New approach could speed better tests for earliest appearance of cancer cells and help develop vaccines

Scientists at Johns Hopkins have taken a less-is-more approach to designing effective drug treatments that are precisely tailored to disease-causing pathogens, such as viruses and bacteria, and cancer cells, any of which can trigger the body's immune system defenses.

In a report to be published in the latest issue of Nature Medicine online Oct. 31, researchers describe a new "epitope-mapping" laboratory test that within three weeks can pinpoint the unique binding site – or epitope – from any antigen where immune system T cells can most securely attach and attack invading germs or errant cells.

Knowing exactly where the best antigen-T-cell fit occurs – at sites where short stretches of proteins, called peptides, bind and are displayed on the surface of antigen-processing immune system cells – is a prerequisite for designing effective and targeted drug therapies, researchers say.

Identifying the best binding site, they say, should speed up cancer vaccine development, lead to new diagnostic tests that detect the first appearance of cancer cells, well before tumors develop, and sort out disorders that are difficult to diagnose, such as Lyme disease.

"Our new, simplified system reproduces what happens in the cells of the immune system when antigens from a pathogen first enter the body and need to be broken down into peptides to become visible to T cells, one of the two immune defender cell types," says immunologist Scheherazade Sadegh-Nasseri, Ph.D., an associate professor of pathology, biophysics and biophysical chemistry at the Johns Hopkins University School of Medicine. "Once T cells recognize an antigen, they latch on, become activated, and call for other immune system cells to enter the fight," adds Sadegh-Nasseri, the senior study investigator for the team of scientists who developed the new epitope-mapping process.

Sadegh-Nasseri says the team's new lab test takes a fraction of the time involved in current methods, which rely on sequencing, or identifying every single peptide in the antigen's make-up, one after another. Such sequencing can take months, or even years, to identify possible T cell binding sites.

"The added beauty of our system is that the entire process can be done in the lab, so we do not have to perform tests in people," says Sadegh-Nasseri, who has a patent pending for the new test.

The Johns Hopkins team, including co-lead investigators AeRyon Kim, Ph.D., and Isamu Hartman, Ph.D., also immunologists, based their test on nearly 20 years of the team's previous research into how immune system cells selectively process antigens and the maze of possible protein combinations inside. That cumulative research led them to narrow their search to five essential and well-described proteins involved in antigen processing by immune system cells.

In their latest series of experiments, the team tested a mix of the selected immune system proteins to see if it could accurately detect two already known epitopes, those of the Texas strain of the influenza virus and type II collagen, both widely used experimental antigens. Then, they used the mix to find unknown epitopes for portions of the influenza virus that causes avian flu and for the parasite involved in malaria.

Chief among the epitope-mapping test's chemical components was a protein molecule common to all the body's immune system cells, called HLA-DR. This molecule is one of the most common binding molecules used in the natural immune system's peptide selection process. HLA stands for human leukocyte antigen, and HLA-DR is produced in a gene-dense region of the body's immune system, the major histocompatibility complex.

Other key chemicals in the make-up were HLA-DM, another protein compound that disrupts the binding of HLA-DR molecules to an antigen if the fit is not perfect, and three of the most common enzymes, so-called cathepsins, involved in breaking up the antigen into its visible, identifiable protein parts.

In the first set of experiments, the team mixed chemical solutions of each antigen with the five key proteins and used mass spectrometry – an electron-beaming device that can measure the exact make-up of molecules – to determine the best-fitting peptide based on precisely which segment of the antigen appeared as mass peaks. Peaks would indicate that HLA-DR had successfully bound to the antigen at a likely epitope.

Next, researchers confirmed their mass spectrometry findings by injecting mice bred to produce human HLA-DR with each antigen to trigger a standard immune response and collecting samples of the resulting T cells. The T cells were then grown in the lab and exposed to various peptides, including the suspect epitopes, to identify and confirm that only one triggered the greatest chemical response from the cultured T cells. The scientists knew that if they could match a peak highlighted by mass spectrometry to the peptide that produced the greatest T cell reaction, they had found the most heavily favored epitope.

When both tests were performed on any of the four disease antigens, researchers were able to narrow the suspect binding sites to one "immunodominant" epitope each for Texas strain of the flu, type II collagen, avian flu and malaria.

Kim, a postdoctoral research fellow at Johns Hopkins, says designing both experiments and completing the verification study took some seven years, noting that adding HLA-DM, which she calls a protein editor, was the pivotal factor in making the initial epitope-selection process work.

Researchers say their next steps are to broaden and refine their chemical mixture for selecting and identifying possible epitopes for other kinds of HLA because the current set of experiments analyzes only one of the most common HLA-type molecules in whites.

Study support was provided with funding from the National Institute of Allergy and Infectious Diseases, a member of the National Institutes of Health. Additional funding came from the Johns Hopkins Malaria Research Institute.

Besides Sadegh-Nasseri, Kim and Hartman, other Hopkins researchers involved in this study were Robert Cotter, Ph.D.; Kimberly Walters, Ph.D.; Sarat Dalai, Ph.D.; Tatiana Boronina, Ph.D.; Wendell Griffith, Ph.D.; and Robert Cole, Ph.D. Hartman is now at University of Texas Southwestern Medical Center. Other investigators were based at the U.S. Walter Reed Army Institute of Research, including Robert Schwenk, Ph.D.; David Lanar, Ph.D.; and Urszula Krzych, Ph.D.

For additional information, go to:
http://pathology2.jhu.edu/ssnweb/index.html
http://www.nature.com/nm/index.html

David March | EurekAlert!
Further information:
http://www.jhmi.edu

More articles from Health and Medicine:

nachricht Researchers release the brakes on the immune system
18.10.2017 | Rheinische Friedrich-Wilhelms-Universität Bonn

nachricht Norovirus evades immune system by hiding out in rare gut cells
12.10.2017 | University of Pennsylvania School of Medicine

All articles from Health and Medicine >>>

The most recent press releases about innovation >>>

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

Im Focus: Neutron star merger directly observed for the first time

University of Maryland researchers contribute to historic detection of gravitational waves and light created by event

On August 17, 2017, at 12:41:04 UTC, scientists made the first direct observation of a merger between two neutron stars--the dense, collapsed cores that remain...

Im Focus: Breaking: the first light from two neutron stars merging

Seven new papers describe the first-ever detection of light from a gravitational wave source. The event, caused by two neutron stars colliding and merging together, was dubbed GW170817 because it sent ripples through space-time that reached Earth on 2017 August 17. Around the world, hundreds of excited astronomers mobilized quickly and were able to observe the event using numerous telescopes, providing a wealth of new data.

Previous detections of gravitational waves have all involved the merger of two black holes, a feat that won the 2017 Nobel Prize in Physics earlier this month....

Im Focus: Smart sensors for efficient processes

Material defects in end products can quickly result in failures in many areas of industry, and have a massive impact on the safe use of their products. This is why, in the field of quality assurance, intelligent, nondestructive sensor systems play a key role. They allow testing components and parts in a rapid and cost-efficient manner without destroying the actual product or changing its surface. Experts from the Fraunhofer IZFP in Saarbrücken will be presenting two exhibits at the Blechexpo in Stuttgart from 7–10 November 2017 that allow fast, reliable, and automated characterization of materials and detection of defects (Hall 5, Booth 5306).

When quality testing uses time-consuming destructive test methods, it can result in enormous costs due to damaging or destroying the products. And given that...

Im Focus: Cold molecules on collision course

Using a new cooling technique MPQ scientists succeed at observing collisions in a dense beam of cold and slow dipolar molecules.

How do chemical reactions proceed at extremely low temperatures? The answer requires the investigation of molecular samples that are cold, dense, and slow at...

Im Focus: Shrinking the proton again!

Scientists from the Max Planck Institute of Quantum Optics, using high precision laser spectroscopy of atomic hydrogen, confirm the surprisingly small value of the proton radius determined from muonic hydrogen.

It was one of the breakthroughs of the year 2010: Laser spectroscopy of muonic hydrogen resulted in a value for the proton charge radius that was significantly...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

ASEAN Member States discuss the future role of renewable energy

17.10.2017 | Event News

World Health Summit 2017: International experts set the course for the future of Global Health

10.10.2017 | Event News

Climate Engineering Conference 2017 Opens in Berlin

10.10.2017 | Event News

 
Latest News

Osaka university researchers make the slipperiest surfaces adhesive

18.10.2017 | Materials Sciences

Space radiation won't stop NASA's human exploration

18.10.2017 | Physics and Astronomy

Los Alamos researchers and supercomputers help interpret the latest LIGO findings

18.10.2017 | Physics and Astronomy

VideoLinks
B2B-VideoLinks
More VideoLinks >>>