Researchers Uncover Tuberculosis' Genomic Signature

Discovery could help determine who will develop the disease and who won't

Dallas scientists recently discovered a molecular signature in the blood of patients with tuberculosis (TB) that may explain why some people develop an active TB infection, while others exposed to the bacteria which causes the dangerous respiratory virus do not.

Researchers at Baylor Institute for Immunology Research (BIIR) in Dallas, a component of Baylor Research Institute (BRI), and MRC National Institute for Medical Research (NIMR) in England made the discovery and presented their study in the Aug. 2010 issue of the journal Nature. The researchers say their findings could lead to new diagnostic tests and more effective vaccines and treatments.

"Millions of people are exposed to the bacteria that causes TB, yet only a small percentage go on to actually get sick," says Damien Chaussabel, PhD, associate investigator, Baylor Institute for Immunology Research. "Testing for this genetic signature could essentially predict which people with the latent form of the disease will later get an active infection, allowing for earlier and more effective intervention."

Tuberculosis is one of the deadliest diseases in the world with more than one-third of the world's population infected, according to the Centers for Disease Control and Prevention (CDC). The CDC estimates that more than 9 million people are stricken ill with the disease each year. If not diagnosed and treated promptly, TB can cause permanent damage to the lungs and in some cases death.

Currently, there are blood and skin tests designed to detect Mycobacterium tuberculosis(MTb),the bacteria that causes TB, but neither test can determine who will develop active TB and who will remain symptom free.

The elderly, infants and those with compromised immune systems are most at-risk for the disease making the findings more significant for these groups since they also have the most difficulty fighting the infection.

"Through our research, we found certain genes in the blood of patients with active pulmonary TB that weren't present in subjects who had tested positive for MTb, but never had an active infection. This signature reflects the extent of the disease in the lungs and how it disappears after being treated successfully," explains Dr. Chaussabel.

The study analyzed the blood of 400 participants; a mix of people with active and latent TB infections and those with no infection at all. The initial research was conducted in London with a comparative analysis later carried out in Cape Town, South Africa where the disease is more prevalent. Their results showed that a specific genetic signature appeared in the blood of those with an active TB infection as well as in 10 percent of those with a latent form of TB.

"As of now, we have no way of knowing if that 10 percent of people will ever develop TB, but we are planning additional studies to try and determine that," says Dr. Chaussabel. "These findings are only the beginning, but so far they are very promising. This discovery could potentially change how tuberculosis is managed and treated around the world."

Besides revealing TB's genetic signature, the study also measured how the body reacts to the infection, particularly the response of a certain type of white blood cell. According to Dr. Chaussabel, additional follow-up studies are needed to investigate how this information can be used to develop new potential treatments.

About Tuberculosis:
Tuberculosis (TB) is a bacterial infection often found in the lungs, but is capable of spreading to other organs in the body. Many people who are exposed to the bacteria that causes TB never develop symptoms; however, those with compromised immune systems such as the elderly or people infected with HIV/AIDS, are at a much higher risk of the disease becoming active. If left untreated, the disease can be fatal.

Symptoms of TB include:

  • Shortness of breath
  • Loss of appetite
  • Fatigue
  • Fever, night sweats, chills
  • Coughing

Tuberculosis Statistics*:

  • One-third of the world's population is infected with TB
  • Each year, over nine million people around the world become sick with TB
  • Each year, there are almost two million TB-related deaths worldwide
  • TB is a leading killer of people who are HIV infected
  • In total, 12,904 TB cases (a rate of 4.2 cases per 100,000 persons) were reported in the United States in 2008

CONTACT: Ashley Howland

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