Injecting modified bacteria related to those which cause tuberculosis could protect against the lung disease, US scientists say. Experiments on mice showed the injections could completely eliminate tuberculosis bacteria in some cases, Nature Medicine reports. The only TB vaccine-the BCG jab-is not very effective. The research is in its early stages and the potential for a human vaccine is unknown, campaign group TB Alert says. Tuberculosis is caused by Mycobacterium tuberculosis. It is one of the top ten leading causes of death, according to the World Health Organisation, killing 1.7 million people each year. The BCG vaccine has variable results. It has been shown to be between zero per cent and 80 per cent effective in different parts of the world. There are also potential problems giving the live vaccine to some of the most at risk patients-those with HIV.
In the family
Researchers at the Albert Einstein College of Medicine in New York were investigating a cluster of genes called esx-3, variants of which are in all types of Mycobacterium and help the organisms evade the immune system. Mycobacterium tuberculosis cannot survive without its esx-3 genes but its relative, Mycobacterium smegmatis, can. Scientists deleted the genes from M. smegmatis and injected an otherwise deadly dose into mice. Within three days the mice had cleared the bacteria from the lungs and kidneys. The research team then tried putting the esx-3 genes from M tuberculosis into M smegmatis, which they then called Ikeplus. Mice were still able to rapidly clear an Ikeplus infection but it seemed to leave a lasting immunity against M tuberculosis.
Survival
In mice infected with the TB bacteria, those which received no vaccine died after 54 days on average. Those vaccinated with BCG lasted 65 days, while mice immunised with Ikeplus survived for 135 days. In the mice which survived the longest, more than 200 days, researchers were no longer able to detect the deadly bacteria. Lead researcher Prof William Jacobs said: "We consistently protected mice better with Ikeplus than with BCG. "This is something we've dreamed about for years, to be able to get longer protection and bactericidal immunity." He warned that only 20 per cent of the mice were long-term survivors so the vaccine would need further development. He added: "Ikeplus is different from any other TB vaccine and it's a new tool for the TB arsenal." A TB Alert spokesperson said: "These are interesting experiments but it is too early to tell what impact they will have on the development of a safe and effective vaccine." (BBC)
Tuberculosis at a glance
• Tuberculosis is an infectious disease, which usually affects the lungs
• It is transmitted via droplets from the lungs of people with the active form of the disease
• In healthy people, infection often causes no symptoms
• Symptoms of active TB include coughing, chest pains, weakness, weight loss, fever and night sweats
• Tuberculosis is treatable with a course of antibiotics
• In the UK, around 9,000 cases of TB are reported each year, mainly in big cities such as London
According to the statistics of the World Health Organisation, TB kills more young people and adults than any other infectious disease in the world. It causes more deaths than Aids and Malaria combined. Although the use of penicillin and antibiotics have caused the decline of this disease in some countries, hot spots of this illness still exist in eastern Europe, south east Asia and sub-Saharan Africa.
Tuberculosis numbers that were seemingly beginning to decrease began to rise in the 1980's with the emergence of Aids. Scientists now say that the number of people with TB around the world has reached a ten year high. (worldhealthsciences.com)