Sixteen people in Belarus have been cured of tuberculosis after having their own immune cells multiplied outside their bodies, and given back to them. Before treatment, their infections resisted many TB drugs, so the approach offers hope that such immune tricks might replace the antibiotics that are losing their power against bacteria. But harnessing the immune system will not be easy.
About a third of the world鈥檚 population is infected with the TB-causing bacteria (Mycobacterium tuberculosis). Most infections are kept in check by the immune system, but every year active disease develops in 8.6 million people, and 1.3 million people die 鈥� a toll for one infection that is .
Since 1990, the spread of TB has slowed, and death rates halved because of antibiotics that, if taken for long enough, kill off the bacteria. But the bacteria are evolving resistance. At any given time, around half a million infections worldwide resist two important TB drugs, and some resist almost every drug we have. , head of the Wellcome Trust, a UK health research foundation, singled out drug-resistant TB when he repeated alarms this week about the 鈥渁pocalyptic鈥� threat of antibiotic resistance.
Advertisement
Calming effect
In theory, heightening the body鈥檚 own immune defences could be used alongside or even instead of using antibiotics to kill off TB bacteria. The problem is knowing which immune reaction to tweak: some of the body鈥檚 immune reactions to TB damage and inflame lung tissue more than they fight infection, says of the Karolinska Institute in Stockholm, Sweden.
However, there are cells in the body that can . These mesenchymal stromal cells (MSCs) are stem cells found in bone marrow, and they are already used to treat some autoimmune diseases, so Maeurer wondered whether boosting their production would be beneficial for people with TB.
To find out, his team took MSCs from 30 people with drug-resistant TB in Belarus, one of the countries hardest-hit by resistant TB. They multiplied the MSCs outside the body, then injected them back into their owners鈥� blood.
The procedure caused no ill effects. The participants kept taking their TB medication during and after the trial. Within 18 months, there was no evidence of TB infection in 16 of the 30 people, compared with only five in a similar group of 30 participants that received no MSCs. 鈥淲e also saw improvements of the lung lesions on X-ray鈥� and in some immune reactions after MSCs treatment, says Maeurer.
Tipping the balance
The trial was designed to assess the safety of boosting people鈥檚 MSCs rather than the technique鈥檚 effect on the patients鈥� disease. A larger double-blind, placebo-controlled study is still needed to do that, but Maeurer says the preliminary results are encouraging 鈥� especially because those who received MSCs were originally sicker than the group that didn鈥檛.
The people鈥檚 own MSCs damped the inflammation that was paralysing the immune system and damaging the lung, and turned suppressed immune reactions back on, Maeurer says. He is now planning a larger trial.
鈥淚 am somewhat sceptical,鈥� says Robert Wilkinson of the University of Cape Town in South Africa, who wrote a comment that accompanied the report of Maeurer鈥檚 work this week. 鈥淭he changes in immune response are very modest indeed.鈥� Moreover, even if it works, he says MSC therapy is beyond the capabilities of clinics in countries, such as South Africa, where resistant TB is a problem.
Maeurer counters that multiplying MSCs is a simple procedure 鈥� and with full treatment for drug-resistant TB costing $180,000 per patient, the extra cost of using MSCs in combination with existing TB drugs could quickly pay for itself by reducing the time the drugs are needed for. Drugs that mimic MSCs might also be possible, as could testing to see if individual infections will respond to this approach.
Journal reference: The Lancet, DOI: and DOI:
