Indian scientists have developed a new tuberculosis vaccine and found it to be safe and effective for low immunity cases too in the animal-trial stage.

The candidate vaccine, a possible weapon against tuberculosis which has resurfaced as a killer especially in combination with AIDS, has been developed by the scientists at the Central Drug Research Institute (CDRI), Lucknow.

The vaccine is a live form of a different strain of Mycobacterium, the bacteria that cause tuberculosis, a Council of Scientific and Industrial Research report said.

"The candidate vaccine should be evaluated in clinical trials," it said.

While Mycobacterium tuberculosis causes tuberculosis in human beings, a different strain, Mycobacterium habana, is reported in mice, guinea pig and monkey without causing the disease, the report said.

The studies found that live M habana generates an immune response against tuberculosis in mice. "It is possibly due to certain similarities between M habana and M tuberculosis," it said.

Mice vaccinated with live M habana remained healthy, gained weight and survived with organ functioning also remaining normal.

This implied that live M habana was safe, the report said.

The vaccine was cleared from the body in about three months.

The vaccine was found to be effective in protecting against TB infection -- 70 per cent of vaccinated mice when infected with tuberculosis survived while unvaccinated mice died within 25 days of infection, the report said.

The load of disease causing bacteria was markedly less, at least 100-fold, in the lungs of vaccinated mice
compared to the unvaccinated infected mice, it said. The damage to lungs was limited with lesions being very small.

Thus vaccination prevented death of mice from TB, protected lung damage and restricted multiplication of TB bacteria, the report said.

The vaccine was also evaluated in mice that were made to be immuno-compromised as happens in AIDS. Growth of infection was restricted in vaccinated mice, it said.

The report said that BCG is currently the only anti-TB vaccine. Though it has provided protection against TB, the variation in its efficacy warrants development of an improved vaccine.

TB causes about three million deaths every year and one-third of the world's population is currently infected with Mycobacterium.

Thirty million deaths due to TB are feared in this decade due to its combination with HIV pandemic and growing emergence of multi-drug resistance TB.