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Eating a probiotic of harmless bacteria modified to make an immune-suppressing drug may relieve symptoms of rheumatoid arthritis, according to work in rats, and it seems to be more effective than injections.

In rheumatoid arthritis, the immune system mistakenly attacks the tissue that lines the joints, leading to joint pain, swelling and stiffness. As a result, people with severe forms of the condition are often treated using anti-inflammatory drugs that suppress the immune response. Some are delivered by tablet and others 鈥� newer biological ones, sometimes known as biologics 鈥� are given by injection.

Previously, a peptide called ShK-186, which is derived from the venom of a sea anemone, has shown promise in treating autoimmune conditions like arthritis in animal models and early clinical trials in humans. This drug targets a type of cell in the immune system that plays a key role in disease progression.

However, like many other protein-based drugs used to treat arthritis, it must be delivered by repeated injections, which can reduce quality of life, increase the risk of infections and decrease the chance that people adhere to the therapy.

Now, at the Baylor College of Medicine in Texas and her colleagues have genetically engineered a bacterium (Lactobacillus reuteri) that is found in the gut 鈥� and is often used to make yogurt 鈥� so that it produces a modified version of ShK-186, which they called ShK-235. The idea was to create a probiotic where, after it has been consumed, the bacteria manufacture the protein inside the body.

鈥淲e thought, let鈥檚 use one of those probiotics that鈥檚 very well characterised and not dangerous to humans, and then modify it to produce our drug as a way for it to be ingested, bypassing the need for injections,鈥� says Beeton.

To test how it worked, the team either injected rats that had a version of rheumatoid arthritis with ShK-235 every other day for three weeks or fed them the ShK-235-producing probiotic daily for that time instead.

Injected rats had a 60 per cent reduction in swelling of their toes, wrists and ankles compared with another group of rats injected with a control solution. Beeton鈥檚 team gave the injections every other day rather than daily because they found that the maximum therapeutic effect was already reached with this dosage. Rats treated with the ShK-235-producing probiotic daily showed an even greater reduction, of 84 per cent.

鈥淭he first time we tried it, we didn鈥檛 quite believe it. We thought maybe we made a mistake, so we repeated the experiment. And it was actually working,鈥� says Beeton.

Although the team didn鈥檛 see any harmful side effects of the treatment, further work is needed to understand how it may influence the microbiome 鈥� the mix of microorganisms living in our bodies 鈥� before it enters clinical trials.

鈥淲e also hope that probiotics could deliver existing injectable drugs too, but that needs to be tested,鈥� says Beeton.

鈥淚t seems almost too good to be true. You get better available levels of the drug in circulation than you do by injecting the drug, which is remarkable,鈥� says at the University of Leeds, UK. 鈥淚f the treatment works in humans as it has in rats, they have a winning delivery system 鈥� but rats are different to humans, so it needs testing in clinical trials as soon as possible.鈥�

Emery thinks it should work in humans because of what the drug targets in the body. 鈥淓ven if this isn鈥檛 a perfect therapy for rheumatoid arthritis, it could work in combination with the existing biologics, because it would be unlikely to interact with them.鈥�

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