‘Ticked Off: The Science Behind Lyme Disease
Alleluia! Summer! It means the promise of more time in the fresh air—gardening, camping, or just enjoying the sunshine. Unfortunately, time outdoors increases the risk of contracting Lyme disease. As you may know, this illness comes courtesy of our favorite blood-sucking arthropods: ticks. Not just any tick, however. Only the diminutive deer tick (Ixodes scapularis) transmits this nasty disease. Lyme has been reported in every US state but most commonly occurs in the Northeast and the upper Midwest. The disease gets its name from the tiny Connecticut town of Lyme, where doctors identified a cluster of cases in the 1970s. This WEEKLY looks at the cause, treatment, and possible complications of this potentially debilitating disease. We’ll also preview a new Lyme vaccine that the FDA has awarded fast-track status.
The microbiological culprit behind Lyme is the bacterium Borrelia burgdorferi. These microorganisms inhabit deer of course, but smaller animals such as mice and birds too. A hungry deer tick chomps on, say, an infected white-footed mouse. When the tiny black-legged parasite eventually feeds again, it passes on the gift of Lyme to its next victim, whether gardener or groundhog. In a human host, proteins on the surface of B. burgdorferi wreak havoc within and outside our cells. The bacterium disrupts the function of infected tissues at the cellular level. Combined with the body’s inflammatory response, the symptoms of Lyme disease ensue.
The Infamous Bull’s-Eye
The most notorious sign of Lyme disease is the red bull’s-eye rash that often develops near the bite. According to the Center for Disease Control, other symptoms that may occur within the first 30 days of infection include fever, muscle and joint aches, and swollen lymph nodes. Unfortunately, not everyone develops the bull’s-eye, and it’s easy to confuse Lyme disease with other illnesses. Failing prompt diagnosis and antibiotic treatment, a plethora of more severe symptoms can develop days or even months after exposure. These can include heart palpitations, severe joint pain, facial palsy, and short-term memory issues.
Health care providers primarily diagnose Lyme disease based on symptoms, known or potential exposure to deer ticks, and an FDA-approved blood test for anti- B. burgdorferi antibodies. None of these approaches is ideal. Lyme disease’s rash fails to appear in about a quarter of infected people. Unfortunately, it usually takes a month or longer after infection for people to produce enough B. burgdorferi antibodies to show up in a blood test. This lag can delay treatment and creates a window for the most serious outcomes such as nerve damage and heart problems. Thus, epidemiologists and other scientists are in hot pursuit of tests capable of detecting the bacterium earlier. (Article continues below)
One innovative approach comes from Ceres Nanoscience (Manassas, VA) and their “nanotrap” technology. Rather than trying to detect a patient’s response to infection, the Ceres Nanotrap Lyme Antigen Test detects the presence of B. burgdorferi itself. It works by identifying the bacterial protein OspA in the urine of infected patients. Other researchers have tried this method but found themselves stymied due to the low concentration of the protein in the samples. Enter nanotrap technology. These nanoparticles (10-9 meter diameter) consist of an outer shell that surrounds a “bait” molecule. The shell filters out proteins larger than the target. Meanwhile, the molecular bait inside captures only OspA. The nanotraps are then processed to remove any captured proteins and identify them.
The new Ceres test is available as a CLIA (Clinical Laboratory Improvements Amendment) test. This means that the test itself cannot be sold to a physician’s office or pharmacy but must be performed at a laboratory facility approved by the Centers for Medicare and Medicaid services. In suspected Lyme disease cases, a urine sample is sent to the Ceres lab, analyzed using the Nanotrap test, and the results sent back to the physician’s office.
Another strategy for diagnosing infectious diseases sooner rather than later is PCR-based testing—detecting and amplifying specific pathogen-associated gene sequences. This approach works well with many viruses, including HIV and influenza. However, identifying a bacterial infection such as Lyme disease this way is tougher. Why? During an active viral infection, viruses reach high concentrations within the bloodstream. This makes it relatively easy to find them in a simple blood draw. In contrast, the Lyme bacterium tends to “hide out” in tissues, making it more difficult to obtain gene sequences from a blood sample. Nonetheless, there is a DNA-based test for the disease, developed by DNA Connexions (Colorado Springs, CO). Like the nanotrap test, it’s available as a CLIA lab test.
People whose Lyme disease gets diagnosed early are most likely to respond to the standard antibiotic treatment. Otherwise, debilitating symptoms are more likely to develop and linger. In a small percentage of patients, symptoms such as fatigue and pain linger for months or even years. This phenomenon is known as post-treatment Lyme disease syndrome.
Cover Up & Spray!
For now, the best way to avoid contracting Lyme disease is to protect yourself by wearing long sleeves, pants, and a hat or scarf in areas where deer ticks are common. In addition, it’s important to check yourself or your loved ones for ticks after you’ve spent time outdoors.
Vaccine on the Horizon
Fortunately, a French company, Valneva, is giving lovers of the great outdoors something more than a bottle of DEET to ward off Lyme disease. The Lyon, France-based biotech company is developing a Lyme vaccine. Known as VLA15-101, it consists of the B. burgdorferi surface protein OspA. Researchers hope to train our bodies via needle to recognize the bacterium as a threat and rev up our immune response in case of actual infection. The vaccine includes all six types of OspA proteins. VLA15-101 is currently in Phase I clinical studies and has been granted fast-track status by the FDA.
Cocktail Fodder: Formidable Foes
Ticks have a few tricks up their teeny-tiny segmented sleeve when it comes to obtaining their blood banquet. People don’t always notice a bite because the sneaky little arachnids inject a neurotoxin (basically a local anesthetic) when they latch on. By the time the host finds the freeloader, the little parasite can be very difficult to remove. That’s because the tick secretes another secret weapon—a sticky substance called “cementum” near the bite, allowing it to hang on tight for chow time.
Emily Burke, PhD has worked in biopharma for 20 years, gaining science writing experience at The Scripps Research Institute and Ionis Pharmaceuticals. As a Ph.D. molecular biologist, she is passionate about advancing the public’s understanding of science. In addition to being a self-proclaimed “science geek,” she is regularly asked to speak at international scientific meetings. When not teaching and writing the WEEKLY for Biotech Primer, Dr. Burke swims with her swim club and performs regularly on the improv circuit in San Diego.