New Genomic Marker for Tuberculosis


One third of the world's total popula-
tion is infected with the microbes that
cause TB;©
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Tuberculosis (TB) is caused by the bacterium Mycobacterium tuberculosis, which usually attacks the lungs and can be fatal if not treated properly. Although TB is no longer a leading cause of death, it remains an epidemic in much of the world. One third of the world's total population is infected with the microbes that cause TB; however, most people infected remain asymptomatic with latent TB. People with latent TB have a 10 percent lifetime risk of developing active TB, but current tests cannot identify which individuals will develop the disease.

"Tools to diagnose infections like TB, bronchiolitis and pneumonia have been developed and are actively used to classify patients as being infected with specific pathogens, but we are still unable to predict how each person is going to react to the infection," said one of the study's authors Doctor Octavio Ramilo. "It's difficult to predict patient outcomes, and this is a real problem."

To combat this problem the researchers are using microarray technology to develop blood profiles in patients specific to infectious diseases. "Each infectious agent, be it a virus or a bacterium, interacts with human immune cells in unique ways by triggering proteins on white blood cells," said Doctor Mejias. "We can identify patterns among the white blood cell's activated proteins and identify a unique 'signature' for each infectious agent."

Ramilo and research has shown that gene expression microarray technology can be used to help develop blood transcriptional signatures. "This technology allows us to see the whole picture of infection using a single blood sample, which is a really powerful tool for the clinic," said Mejias.

The study examined and compared blood drawn from patients in London, England and Cape Town, South Africa who had active TB, latent TB or who did not have TB. The team developed genome-wide transcriptional profiles for each of the patients and discovered a distinct characteristic, or "signature," of the blood from patients with active TB. X-rays of patients with this signature were consistent with signs of active TB.

"The study shows for the first time that the transcriptional signature in blood correlates with extent of disease in active TB patients," said Ramilo. "It validates the idea that this transcriptional signature is an accurate marker of TB infection."; Source: Nationwide Children's Hospital