Semi-Precious Pathogens

Oct. 17, 2014

By Medical Discovery News

Bug in amber

Some diseases are older than others. AIDS, for instance, is a recent phenomenon, while malaria has plagued humans for millennia. Recently, scientists examining ticks fossilized in amber found they were infected with bacteria similar to those that cause Lyme disease, a spirochete named Borrelia burgdorferi. Lyme disease is a bacterial infection caused by the bite of an infected tick. The discovery of an ancient Borrelia-like bacterium, now named Palaeoborrelia dominicana, shows that tick-borne diseases have been around for millions of years.

Lyme disease was identified in the early 1970s when mysterious cases of rheumatoid arthritis struck children in Lyme, Conn., and two other nearby towns. The first symptom is a rash called erythema migrans, which begins with a small red spot where the tick bite occurred. Over the next few days or weeks, the rash gets larger, forming a circular or oval red rash much like a bull’s eye. This rash can stay small or can cover the entire back. But not everyone with Lyme disease gets this rash, and the other symptoms, including fever, headaches, stiff neck, body aches, and fatigue, are common to many other ailments. Some people develop symptoms of arthritis, nervous system problems, or even cardiac issues.

Lyme disease can be difficult to diagnose. Sometimes, people write off their initial symptoms as the flu or another common illness, and experience symptoms for months or even years before finding the true cause. To diagnose Lyme disease, doctors measure the levels of antibodies the body produces in response to Borrelia infection. Lyme patients are treated with antibiotics, but if the bacteria have been in the body for a long period of time, it can take a long time to cure. The sooner diagnosis and treatment begin, the more quickly and completely patients will recover. Even after treatment for Lyme disease, people can still experience muscle or joint aches and nervous system symptoms.

Scientists from Oregon State University have studied 15- to 20-million-year-old amber found in the Dominican Republic. Despite existing for millions of years, bacteria are rarely found in fossils. However, free-flowing tree resin traps and preserves material such as seeds, leaves, feathers, and insects in great detail. Amber is then formed from the fossilization of the resin over millions of years as it turns into a semi-precious stone. This is the oldest fossil evidence of ticks containing such bacteria.

Four ticks from the Dominican amber were examined and found to have large populations of spirochetes that resemble the Borrelia bacteria, such as those that cause Lyme disease today. The oldest reported case of Lyme disease was Oetzi, a well-preserved natural mummy who lived 5,000 years ago and was discovered by hikers in the Alps. In other studies, fossils have revealed bacteria such as Rickettsia, which cause modern diseases like Spotted Fevers and Typhus, found in ticks from about 100 million years ago. Evidence suggests that even dinosaurs may have been infected with Rickettsia, showing these microbes likely infected other creatures before humans were added to the mix. Millions of years of co-evolution resulted in highly adapted pathogens that scientists and physicians still struggle to understand and treat.

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Ticked Off Meateaters

August 2, 2013

By Medical Discovery News

Using bug spray is more important than ever – especially for those who particularly enjoy eating hamburgers. It might sound like those two things aren’t related, but a person bitten by a certain tick can develop a severe allergy to meat.

This type of food allergy only develops in people who have been bitten by the Lone Star Tick, which has previously been linked to a condition known as Southern Tick Associated Rash Illness (STARI). The tick bite that causes this illness results in a rash, fatigue, headache, fever, and muscle pains. It is often confused with Lyme disease, which is also spread by ticks.

After being bitten by the Lone Star Tick, a person develops antibodies, which are molecules of the immune system that normally target and destroy invaders like viruses and bacteria, against a complex sugar called galactose-alpha-1,3-galactose (alpha-gal). This sugar exists in all mammals except primates, including cows, pigs, and sheep. This specific allergy has a delayed response, so a person would experience symptoms like hives four to six hours after eating a meat such as bacon. Some people even suffer life-threatening anaphylactic shock.

It is unclear what in tick saliva triggers alpha-gal antibody production. When ticks latch on to people with their mouthparts they can remain attached for several days and introduce saliva into the skin at the bite site. Tick saliva contains molecules that keep the tick firmly attached to its host. It also keeps the blood at the site from clotting so the tick can continue its meal and can influence the immune response and angiogenesis, the development of new blood vessels. In addition, ticks can transmit a variety of viruses and bacteria through their saliva.

This allergy first came to light because some cancer patients were unusually sensitive to the cancer drug cetuximab, which includes the alpha-gal molecule. But only patients from the southeastern and eastern United States, where the Lone Star Tick lives, experienced this and they all had high levels of alpha-gal antibodies. Currently, more than 80 percent of the people with this meat allergy had tick bites before exhibiting symptoms.

But now that cases of this meat allergy have been reported outside the Lone Star Tick’s habitat, such as Hawaii, researchers are wondering whether this tick has spread further than they thought, or if other tick species can cause a similar reaction. The Lone Star Tick is very aggressive when it comes to biting people and animals, so to prevent tick bites use a bug spray with permethrin, avoid wooded areas, and frequently check for ticks when outside. Otherwise, a person may find themselves watching everyone else eat during a summer barbeque!

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Sand in Your Eyes

June 28, 2013

By Medical Discovery News

First the eyes feel dry, so dry the sensation is like having sand in them. Then the mouth dries out so that it’s hard to swallow. While the symptoms come on slowly, the disease is usually diagnosed after it’s too late. By then, the patients’ salivary glands and tear glands are already destroyed and there is little that can be done. But researchers are trying to change that by developing a test that could diagnose Sjogren’s Syndrome (SS) earlier.

As the third most common autoimmune disorder in the U.S., SS affects about 4 million Americans, most of them women and over 40. Autoimmune disorders result from a person’s own immune system attacking the body. The worst part is that there is no cure for SS.

The disease first attacks the mucous membranes and moisture secreting glands, causing dry eyes and mouth which are treated with over-the-counter and prescription medications. However, this disease is systemic, affecting many parts of the body including the brain, kidneys, liver, lungs, skin, and nerves among others. A person with SS can end up seeing a host of specialists including rheumatologists and dentists to come up with an individualized treatment plan using immunosuppressive therapies to treat this complex disease. They also face a 5-15 percent chance of developing lymphomas as the disease progresses.

Diagnosis of SS includes blood tests to measure antibodies frequently associated with autoimmune disorders, ophthalmological tests for tear production and dryness of the surface of the eye, additional tests to measure salivary gland function, and a biopsy to check for signs of inflammation may also be done. Diagnosis is based on having a combination of symptoms and results of the various lab tests. Currently, there is no known test to definitively diagnose it.

But now researchers have developed a test that could diagnose SS much sooner, before the damage sets in. Since it is very rare to diagnose humans in the early stages of SS, researchers had to first develop an animal model of SS in mice that closely resembles the disease in humans. This allowed researchers to look for markers of the disease as it progressed. They discovered elevated levels of messenger RNAs that code for three salivary gland proteins in SS mice. They also found that the SS mice were making antibodies against these three proteins, in effect attacking themselves, the hallmark of an autoimmune disorder.

They then detected the same autoantibodies in human SS patients. So, the new test works by measuring the levels of these three types of unique antibodies in the blood.  Antibodies, Y-shaped proteins produced by the immune system, recognize and bind to antigens, substances that the body flags as foreign and/or harmful, like bacteria and viruses.

These newly identified autoantibodies appear much earlier, providing an opportunity for earlier and more definitive diagnosis. Earlier diagnosis may allow doctors to start therapies that may save SS patients’ salivary and tear glands, alleviating their symptoms and slowing the progression of SS.

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Aging But Still Protected

June 14, 2013

By Medical Discovery News

The people who are at the highest risk of dying from common infections like pneumonia, influenza, and colds are 50 and older. Traditionally, scientists believed that as we age, our immune systems weaken, leaving us more vulnerable than ever to infections. But new research suggests that this isn’t completely true – certain parts of the immune system remain fully functional and robust longer.

It is true that older people make fewer antibodies, proteins that attach to viruses and cells infected with viruses to mark them for elimination by the immune system. This explains why some vaccines aren’t as effective in the elderly. The flu vaccine, for example, contains a “dead” virus that stimulates the body to make more protective antibodies against the flu.

However, other vaccines are well-received in older people, like the varicella zoster virus vaccine that prevents shingles. This vaccine does not involve antibodies, but T-cells, which kill infected cells, and memory T-cells, which recognize and respond to a reinfection.

White blood cells, formally called leukocytes, represent an army ready to defend the body from bacterial or viral attacks. T-cells are one type of soldier in this army, responsible for cellular immunity – killing infected cells to protect the body. The thymus, located between the breast bone and heart, produces T-cells. But as people age, the thymus does too.

The thymus shrinks by about 3 percent a year during middle age, and there is a corresponding fall in the production of T-cells. As humans age, their T-cells increasingly become memory cells. Therefore, it’s been assumed that the T-cell response to kill cells infected with a virus is impaired in older adults, making them more susceptible to viral infections.

To test that assumption, researchers at the McMaster Immunology Research Centre in Ontario isolated blood from people with one of three types of viral infections: West Nile Virus, Epstein-Barr Virus, and Cytomegalovirus. They divided the patients into three groups: those under 40, those middle-aged (41 – 59), and those over 60. They then measured the amount, type, and activity of the T-cells in each group. The older group did indeed have a shift toward the production of memory T-cells. But surprisingly, the amount of virus-specific T-cells did not decrease with age – the older group had roughly the same amount as the middle and younger groups.

These results suggest that the thymus continues to play an important role in producing T-cells that target viral infections as we age. It also indicates that vaccines designed to stimulate cellular immunity, instead of antibodies, would be more effective in older people. So the flu vaccine might prevent more flu cases in older people if the dead virus was replaced with a live but weakened virus, but currently that’s not approved in the U.S. for people over 50.

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