September 5, 2011
TB Vaccine Shows Promising Results In Lab Tests
Scientists at the Albert Einstein College of Medicine reported on Sunday that a vaccine they developed for tuberculosis had shown promising results during early laboratory testing in mice.Professor William Jacobs and colleagues, who published their findings in the journal Nature Medicine on Sunday, worked with Mycobacterium smegmatis, a species similar to tuberculosis that is lethal in mice but harmless to humans.
"The researchers created a version of M. smegmatis lacking a set of genes, known as ESX-3, considered crucial for evading host immunity," the College of Medicine said in a press release.
"When high doses of the altered bacteria were infused into mice, it became clear that bacteria lacking the ESX-3 genes could no longer evade their hosts' immune system: the mice controlled and cleared the infection through a robust T-cell response--the same response a successful TB vaccine would elicit," they added.
They attempted to remove the same genes from M. tuberculosis, but discovered that doing so killed the bacterium. So they devised a work-around.
According to the press release: "They took the M. smegmatis bacteria lacking ESX-3 and inserted the analogous set of M. tuberculosis ESX-3 genes. These M. smegmatis bacteria were then infused into mice, which once again fought off the infection."
Two months later, they infected the mice with high doses of tuberculosis. They discovered that the mice who had been treated by the modified M. smegmatis survived the disease nearly three times longer than their unvaccinated counterparts (an average of 135 days compared to 54 days).
Even more amazing, Dr. Jacobs pointed out, is that vaccinated animals who survived for more than 200 days "had livers that were completely clear of TB bacteria“¦ nobody has ever seen that before." He cautioned, however, that only 20% of the mice exhibited such a strong response.
"We don't even know yet if it will work in humans, but it's certainly a significant step in efforts to create a better TB vaccine," he added.
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