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New vaccine for TB

6th September 2011

Using genetically modified bacteria, scientists in the US have come up with a powerful vaccine for tuberculosis.

tbpatient

Injecting the bacteria into people would theoretically give them very strong protection against contracting TB, which is one of the top 10 causes of disease worldwide.

In some test mice, the vaccine, known as Ikeplus, acted as a complete cure.

For mice infected with TB and not given Ikeplus, the average lifespan was about 2 months.

Mice given BCG only lived a few days longer, but mice given Ikeplus lasted over twice as long as the other mice, on average.

The vaccine currently used by doctors does not work well, and resistant strains continue to emerge in the developing world.

At present, there is no way to tell whether or not the genetically engineered bacteria will have the same effects in humans that they have in mice.

Lead researcher William Jacobs, a professor at the Albert Einstein College of Medicine in the Bronx, said that he and his researchers were able to consistently protect mice better with their new vaccine than with BCG.

BCG, the current vaccine, can be at most as 80% effective in best case scenarios, but is often totally ineffective against tuberculosis.

Jacobs said that, for years, researchers had dreamed about being able to protect people from TB, and that the experiments in mice delivered just that, although only 20% of the mice eventually survived their tuberculosis infections.

For the study, the researchers focused on a cluster of genes called ESX-3.

ESX-3 is a blueprint for proteins that help the genus Mycobacteria, of which TB is a member, to evade being caught by the immune system.

TB is totally reliant on ESX-3 for its livelihood, and cannot actually live without the gene.

However, Mycobacterium smegmatis, a closely-related specimen, can live without the gene cluster.

So the scientists made a genetically-engineered version of M. smegmatis totally lacking ESX-3, and injected lethal doses of that modified bacterium (named Ike) into mice.

The mice were completely fine, so the researchers extracted the ESX-3 gene from TB itself, introduced those ESX-3 genes into M. smegmatis, and called the resulting specimen Ikeplus.

A TB Alert spokesperson said that, while the experiments were interesting, it was too early to tell what impact Ikeplus would have on the development of a safe and effective vaccine.

Tuberculosis kills 1.7 million people every year.

In the UK, there are about 9,000 cases of TB every year, and occurrences of the disease tend to centre around big cities like London.

 

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