Shot in the arm for TB

The prospect of more powerful vaccines for the killer disease tuberculosis being available in the near future looks more promising thanks to an important advance in genetic engineering by scientists at Surrey University.

Researchers in the school of biological sciences have triumphed over research teams worldwide in modifying a technique used to analyse and alter DNA extracted from harmful bacteria to produce a strain that no longer causes the disease and also provides protection against it.

TB has proved particularly stubborn to manipulation by the technique in its original form. The success of the modified version could help considerably in the development of new vaccines from strains of tuberculosis. These vaccines would offer much greater protection against TB than traditional treatments.

Project leader Jeremy Dale believes that the work will make a significant contribution to the development of vaccines for TB within the next five to ten years.

TB kills more than three million people a year worldwide and this figure is rising, partly with the spread of Aids. Dr Dale says in many developing countries the TB incidence rate has not declined and in industrialised nations the rate of decline over the last ten years has either slowed or stabilised - in some countries there has even been a reversal. These worrying signals for the advanced countries follow more than 100 years of a solid decline in the rate of incidence of the disease.

An analysis of TB incidence in the United States and United Kingdom shows strong similarities. Dr Dale says: "In both countries inner cities are pockets of high TB activity and this is associated with homelessness and generally poor living standards for a rising number of people."

While TB has shot up in inner cities, the rate in the general population continues to decline. But this is not an indication of containment. Dr Dale says: "It is actually a time bomb. If the TB activity in inner cities continues to rise a critical point will be reached when it breaks out into the general population. The homeless are not totally isolated - there is a degree of mixing." The danger of TB is heightened because the disease is an airborne pathogen which can be breathed in.

Scientists around the world are looking at the interplay between TB and Aids. Dr Dale explains that in most cases, a normal person infected with TB will show no immediate sign since the disease remains latent for a significant period. Subsequent infection with Aids, however, causes TB to blow up extremely quickly. This helps to explain why so many people infected with Aids die of TB. "Aids has helped to create a whole new path for TB infection," says Dr Dale.

Scientists also hypothesise that the reverse may be occurring - that catching TB triggers Aids in patients who are HIV positive. Dr Dale says: "There is no evidence of this yet but it is vital that we understand the pulling and pushing that is going on between the two diseases."