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 Neutrons produce first direct 3D maps of water during cell membrane fusion
21.09.2018 | DOE/Oak Ridge National Laboratory

nachricht Narcolepsy, scientists unmask the culprit of an enigmatic disease
20.09.2018 | Universitätsspital Bern

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: Scientists present new observations to understand the phase transition in quantum chromodynamics

The building blocks of matter in our universe were formed in the first 10 microseconds of its existence, according to the currently accepted scientific picture. After the Big Bang about 13.7 billion years ago, matter consisted mainly of quarks and gluons, two types of elementary particles whose interactions are governed by quantum chromodynamics (QCD), the theory of strong interaction. In the early universe, these particles moved (nearly) freely in a quark-gluon plasma.

This is a joint press release of University Muenster and Heidelberg as well as the GSI Helmholtzzentrum für Schwerionenforschung in Darmstadt.

Then, in a phase transition, they combined and formed hadrons, among them the building blocks of atomic nuclei, protons and neutrons. In the current issue of...

Im Focus: Patented nanostructure for solar cells: Rough optics, smooth surface

Thin-film solar cells made of crystalline silicon are inexpensive and achieve efficiencies of a good 14 percent. However, they could do even better if their shiny surfaces reflected less light. A team led by Prof. Christiane Becker from the Helmholtz-Zentrum Berlin (HZB) has now patented a sophisticated new solution to this problem.

"It is not enough simply to bring more light into the cell," says Christiane Becker. Such surface structures can even ultimately reduce the efficiency by...

Im Focus: New soft coral species discovered in Panama

A study in the journal Bulletin of Marine Science describes a new, blood-red species of octocoral found in Panama. The species in the genus Thesea was discovered in the threatened low-light reef environment on Hannibal Bank, 60 kilometers off mainland Pacific Panama, by researchers at the Smithsonian Tropical Research Institute in Panama (STRI) and the Centro de Investigación en Ciencias del Mar y Limnología (CIMAR) at the University of Costa Rica.

Scientists established the new species, Thesea dalioi, by comparing its physical traits, such as branch thickness and the bright red colony color, with the...

Im Focus: New devices based on rust could reduce excess heat in computers

Physicists explore long-distance information transmission in antiferromagnetic iron oxide

Scientists have succeeded in observing the first long-distance transfer of information in a magnetic group of materials known as antiferromagnets.

Im Focus: Finding Nemo's genes

An international team of researchers has mapped Nemo's genome

An international team of researchers has mapped Nemo's genome, providing the research community with an invaluable resource to decode the response of fish to...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

VideoLinks
Industry & Economy
Event News

"Boston calling": TU Berlin and the Weizenbaum Institute organize a conference in USA

21.09.2018 | Event News

One of the world’s most prominent strategic forums for global health held in Berlin in October 2018

03.09.2018 | Event News

4th Intelligent Materials - European Symposium on Intelligent Materials

27.08.2018 | Event News

 
Latest News

Three NASA missions return first-light data

24.09.2018 | Physics and Astronomy

Brown researchers teach computers to see optical illusions

24.09.2018 | Information Technology

Astrophysicists measure precise rotation pattern of sun-like stars for the first time

21.09.2018 | Physics and Astronomy

VideoLinks
Science & Research
Overview of more VideoLinks >>>