DISEASES WE INVESTIGATE

Lyme Disease

Overview

Lyme disease, or Lyme borreliosis, is a debilitating disease caused by a corkscrew-shaped bacterium, a spirochete, named Borrelia burgdorferi.

It occurs in North America, Europe, and parts of Asia, including northern China. In the United States it is considered an emerging disease because the number of cases that are registered every year is steadily increasing, e.g. 8,000 cases in 1993 to about 45,000 in 2003.

• Lyme disease causes very diverse symptoms. In the disease’s earlier phases, it may induce skin rashes, arthritis, flu-like symptoms, facial paralysis, pain in nerves of the arms and legs, headaches, and meningitis. Later in the disease process it can cause chronic arthritis, forgetfulness and inability to concentrate or function productively.  The mechanisms by which Lyme disease spirochetes cause these symptoms are entirely unknown.

• Most cases of early Lyme disease are successfully treated with antibiotics. However, if the disease remains undetected or is misdiagnosed and antibiotic therapy is delayed, the chances of successful treatment diminish considerably.  Accurate diagnosis of Lyme disease is, therefore, very important.

Spirochete That Causes Lyme disease

• Lyme disease is caused not just by one species of spirochete but by a group of spirochete species broadly named Borrelia burgdorferi. In the U.S., only one species of spirochete causes Lyme disease. This species is called B. burgdorferi sensu stricto (in a strict sense). In Europe, other species that cause Lyme disease are named Borrelia afzelii and Borrelia garinii, in addition to B. burgdorferi sensu stricto.

• As they infect humans and other animals, spirochetes live either in the blood or in tissues but do not invade blood or tissue cells like many parasites do for self protection. Spirochetes remain exposed to attack by antibodies and cells of the immune system and yet, they survive. How spirochetes manage to survive in such a hostile environment is not understood.

Transmission

• Lyme disease spirochetes are transmitted to humans and to other animals by ticks. The most common species of tick able to transmit B. burgdorferi spirochetes is  Ixodes scapularis, also known as the deer tick. These ticks feed mainly on mice, which act as a reservoir host for spirochetes. The adult tick, however, prefers deer for its blood meal, hence the name “deer tick.”

• Ticks transmit the spirochete to humans and other animals when they take a blood meal. Spirochetes are delivered in the skin, together with tick saliva. Tick saliva contains multiple substances, many of which are believed to attenuate the immune response to the spirochete, thereby facilitating transmission. This mechanism of mitigation of the immune response is not understood.

• Deer ticks able to transmit Lyme disease are common in Louisiana. Why there is virtually no Lyme disease in Louisiana is not known.

Our Research

We are interested in answering key questions that relate to Lyme disease, as it continues to be an emerging  infectious disease.  These are:

• What are the mechanisms that enable Lyme disease spirochetes to cause forgetfulness and inability to concentrate or function productively?

• How can we make the diagnosis of Lyme disease more accurate?

• How do Lyme disease spirochetes avoid the immune response of the host?

• How do ticks attenuate the immune response against spirochetes?

• To address these questions we use both monkey and mouse models of Lyme disease as well as ticks.

• Co-infection of HTLV and HIV in AIDS patients is widespread and is thought to increase the    incidence and progression to HTLV disease. 

Treatment

• No vaccine is available for treatment.

• Standard chemotherapy for non-Hodgkin lymphoma is ineffective for ATLL.  A combination of interferon-alpha and the AIDS drug AZT has been found minimally effective. 

• Early symptoms of TSP/HAM may be treated with corticosteroids, cyclophosphamide or interferon; however, those have had limited success.  No treatments for chronic symptoms have been found.

Our Research

• We have developed a monkey model of HTLV-I infection using the closely related monkey virus, simian T cell lymphotropic virus, (STLV-I).  We can grow and study these viruses in the laboratory.

• Monkeys infected with HTLV-I have produced some disease signs including early ATLL, arthritis, uveitis and polymyositis. Co-infection experiments with HTLV-I and SIV were performed and also produced disease related signs.

• Experiments in monkeys are able to answer questions related to infection, disease, and potential vaccine and treatment methods. 

• We have developed a molecular diagnostic real-time polymerase chain reaction (PCR) assay that can quantitate the virus load in the circulation or in tissues.