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Leprosy turns immune system against itself – Wellcome Trust

August 25th, 2017 9:42 am

News / Published: 24 August 2017

Researchers have shown for the first time how leprosy bacteria damage nerves by infiltrating the immune cells that are meant to protect us.

Credit: Bruce Paton/Panos

The research found that leprosy hijacks the immune system, turning an important repair mechanism into one that causes potentially irreparable damage to nerve cells.

The researchers used zebrafish that had been genetically modified to make their myelin fluorescent green.

They injected Mycobacterium leprae bacteria close to the fishes' nerve cells. The bacteria settled on the nerve and developed doughnut-like bubbles of myelin that had separated from the myelin sheath.

When the researchers examined these bubbles more closely, they found that they were caused by M. leprae bacteria inside macrophages the immune cells that consume and destroy foreign bodies and unwanted material in our bodies.But, crucially, although the M. leprae was consumed by the macrophages it wasnt destroyed.

The team also demonstrated how the damage occurs a molecule known as PGL-1 that sits on the surface of M. leprae reprogrammes the macrophage, causing it to overproduce a potentially destructive form of nitric oxide that damages mitochondria.

The international team, in the UK and USA, was part-funded by Wellcome.

The research findings mean that leprosy may share common characteristics with conditions such as multiple sclerosis and Guillain-Barr syndrome.

The researchers say its too early to say whether their study will lead to new treatments. There are several drugs being tested that inhibit the production of nitric oxide, but lead author Professor Lalita Ramakrishnan, at the University of Cambridge, says the key may be to catch the disease at an early enough stage to prevent damage to the nerve cells.

Leprosy is a neglected tropical disease. Its difficult to work with in the lab because its highly adapted to humans. Previously, armadillos were the only animal modelthat could reproduce aspects of the disease. The zebrafish model means researchers can now study the pathogenesis of leprosy in much more detail.

Credit: Bruce Paton/Panos

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Leprosy turns immune system against itself - Wellcome Trust

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