Issue Date: June 24, 2013
Accelerating Lyme Disease Diagnostics
When Tracy Lambeth woke up one day with extreme back pain, she brushed it off as a pulled muscle. But after several weeks, the pain did not go away. She was tested for Lyme disease, even though she did not have a bull’s-eye rash—a common sign of the illness—or any recollection of a tick biting her. The results were negative. Tracy, then 26 and living in Pennsylvania, was told she had fibromyalgia and was sent home without any treatment.
One-and-a-half years later, Tracy was bitten by a tick and developed a bull’s-eye rash on the back of her knee. She was hospitalized for four days. “We think I had the bacteria in my system, and this next tick bite just made everything worse,” she says.
Tracy soon discovered that she was infected with the bacterium that causes Lyme disease—Borrelia burgdorferi—as well as a tick-borne parasite called Babesia microti. She was prescribed a cocktail of antibiotics, which she took for five years. Today, 17 years later, she still suffers from extreme pain and has about 60% of the energy of an average 43-year-old.
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Tracy’s doctors believe that if she had been diagnosed with Lyme disease and treated with antibiotics when she suspects she first got the disease, she probably would not have any symptoms today. Her story is not uncommon. The standard test for Lyme disease recommended by the Centers for Disease Control & Prevention (CDC)—an immunoassay followed by a Western blot—does not work well during the first few weeks of the disease when antibiotics are most effective.
Researchers have been working to develop a more effective diagnostic test for Lyme disease for more than a decade. Although no approach has been shown to be more sensitive and more specific than the standard two-tiered test, advances in measurement technology may soon change that.
The current test has many shortfalls. It doesn’t detect bacteria because bacterial levels in Lyme disease are low. Instead, it detects antibodies in a patient’s blood produced in response to B. burgdorferi. The approach is prone to false-negative results because it can take several weeks before a person produces such antibodies.
The rate of false positives is also a problem for the test. Other diseases can produce a similar immune response, so it is common for people to be misdiagnosed with Lyme disease when they actually have some other ailment.
Nor do available tests give doctors the ability to know whether a patient has been cured of Lyme disease. When patients finish their prescription of antibiotics, there is no test to determine whether the bacteria remain in their body.
Another problem is that ticks often carry more than one pathogen that cause Lyme-like symptoms. So even if B. burgdorferi is the most commonly known tick-borne pathogen, patients may need several different kinds of antibiotics to treat their infection. The current test does not differentiate between the organisms.
The National Institutes of Health spends about $26 million annually on research to improve the understanding and detection of Lyme disease. The agency is currently funding about 60 Lyme disease research grants, of which about a dozen are focused on developing diagnostics.
In some cases, people are trying to identify better targets, such as bacterial peptides, that could be used to detect a host’s response to B. burgdorferi under the same conditions as the CDC-recommended test, says Joseph J. Breen, a program officer who oversees Lyme disease grants at NIH’s National Institute of Allergy & Infectious Diseases. The challenge is to find enough of the peptides to get a strong response.
Some surface antigens on B. burgdorferi are produced only at low levels during infection, so they can’t be measured, Breen notes. The key is to find peptides that are expressed at that right time during infection, he says.
A peptide-based test that relies on multiple peptides would be easier to automate and interpret than the currently used test for Lyme disease, Breen explains. It would also be more specific for B. burgdorferi and thus reduce the number of false positives. However, because it is an antibody-based test, false negatives would still be a problem during the first few weeks of the disease.
To get around the false-negative problem, researchers have been trying to develop a Lyme disease test that detects a host’s T-cell response, which produces immunomodulating proteins called cytokines. Such a response occurs much earlier than the B-cell response that makes antibodies. Until recently, however, the tools for measuring T-cell response were not specific enough to Lyme infection, Breen says. “You couldn’t tell if the body was developing a T-cell response to something that was Lyme or something else.”
With the help of advanced microarrays and DNA-sequencing technologies, there is now “some hope that we could have a way to measure a T-cell-based response,” Breen points out. Such methods could be combined with new ways to look at the pathogen itself to get enough specificity to understand an early response, he says. The key is to identify which cytokines are specific to Lyme disease and produced early.
One of the groups working with microarrays for Lyme disease detection is being led by Charles Chiu, director of the Viral Diagnostics & Discovery Center at the University of California, San Francisco. Chiu and colleagues have expanded a microarray for detecting novel viruses to tick-borne pathogens. The so-called TickChip is a 60,000-probe array that can detect diverse strains of bacteria, parasites, and viruses from a blood sample.
Another approach to detecting Lyme disease that looks promising is the detection of small-molecule biomarkers—such as fatty acids, amino acids, nucleotides, and lipids—in serum or urine samples by liquid chromatography/mass spectrometry. Such biomarkers reflect the rapid change in metabolites associated with disease state, says John Belisle, a professor of bacterial genetics and physiology at Colorado State University. Belisle began applying metabolomics to Lyme disease detection about two years ago.
Emerging technologies such as nanotechnology are also providing potentially novel ways to detect Lyme disease. A research team led by A. T. Charlie Johnson, a professor of physics at the University of Pennsylvania, is developing a system that uses monoclonal antibodies bound to carbon nanotubes to detect proteins from B. burgdorferi. The proteins bind to the antibodies, changing the electrical conduction of the nanotube. Preliminary results from a protein-spiked buffer solution are promising, Johnson says.
“We could distinguish down to about 1 ng/mL, which we thought was pretty good compared to what we knew about commercially,” Johnson notes. He is confident that his group can boost the sensitivity of the approach by engineering the antibody.
Huge strides are also being made in using imaging to diagnose Lyme disease, says James W. Serum, a retired chemist and measurement expert who spent much of his career working for instrumentation company Hewlett-Packard (now Agilent). Serum, along with several members of his family—Tracy Lambeth is his daughter—has been affected by the disease. He organized a National Institute of Standards & Technology workshop on Lyme disease detection earlier this month to help accelerate the development of more effective diagnostics.
Advances in imaging are being driven by more effective contrast agents, Serum notes. One promising agent, he points out, is being developed by Niren Murthy, a professor of bioengineering at the University of California, Berkeley.
Murthy is testing the feasibility of attaching a maltodextrin molecule, which is a food source for bacteria, to a typical imaging agent used in positron emission tomography. When bacteria eat the sugar, they would also ingest the agent and thus could be imaged. Murphy plans to work with researchers he met at the NIST workshop to obtain samples to test his method.
Getting biological samples from Lyme disease patients to validate tests like this can be difficult. One effort to address this challenge is being led by David Roth, a Lyme disease patient and managing director in the Blackstone real estate group, a private equity firm in New York City.
Roth realized the need for such a repository when he started talking to the X Prize Foundation about managing a competition for novel Lyme disease diagnostics. The X Prize Foundation is a nonprofit organization that manages public competitions to spur technological development.
An X Prize competition seemed like a terrific way to leverage the private market and focus the research, biotech, and venture capital community on the problem of inherently flawed Lyme disease diagnostics, Roth explains. The challenge to setting up the competition is that to test the tests, researchers need lots of samples, he notes.
Roth is also the cochairman of the Tick-Borne Disease Alliance, a nonprofit dedicated to increasing funding for research on tick-borne diseases. He is working with the Bay Area Lyme Foundation, in California, to explore options for creating a repository of samples from Lyme disease patients.
“Finding more sensitive and specific diagnostics is the linchpin to breaking the gridlock on Lyme disease and other tick-borne diseases,” Roth says. Like many other people with Lyme disease, Roth was diagnosed four months after he got the disease, when antibiotics are less effective. As a result, his symptoms persist today.
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