In perhaps the biggest tuberculosis breakthrough in two decades, Delhi’s National Institute of Immunology has identified five key genes that enable Mycobacterium tuberculosis to acquire the iron it needs to grow and promote the infection in humans. Experts say targeting genes within this cluster would help evolve better drugs to cure TB, which affects 15.4 million people worldwide.
“Some of these genes are conserved across a number of related bacterial families, so they are promising targets for drugs to treat TB and other bacterial diseases,” says NII’s lead researcher Rajesh S. Gokhale. When the TB bacterium infects humans, it moves to live in immune cells called macrophagus. The bacterium needs to feed on iron to survive and function, which cannot be found within the cell. So the bacterium secretes compounds called siderophores that scavenge iron from outside the cell. Though siderophores were discovered 50 years ago, how the bacterium worked so efficiently remained unexplained till now.
Observing that the expression of some genes increased significantly in response to low iron concentrations in the body, Gokhale and his team identified a new siderophore core and four new genes.
He called them mbtK, mbtL, mbtM and mbtN and named the new core mbt-2.
"Gokhale and his team’s work has identified that siderophores genes and defined their functions. This better understanding of the biosynthetic pathways will help develop more effective anti-TB drugs," says Ranjit Roy Chaudhury, NII emeritis scientist. TB causes 1.6 million annual deaths globally. In India, there are 3 million people currently living with TB, with 1.8 million new infections reported each year. India has a Rs 680-crore Revised National Tuberculosis Control Programme that uses the Directly Observed Treatment (DOTS) strategy to treat all patients free. Under the programme, DOTS centres are set up, where patients are made to eat medicines under supervision to increase compliance. It has a 90 per cent cure rate.
Not completing the full course of medication causes multi-drug resistant TB, which is 100 times more expensive to treat and uses drugs that cause side effects. The programme covers 740 million people, treating 10 million people in India each month.
Sanchita Sharma, New Delhi, February 4http://www.hindustantimes.com/news/5922_1617432,0015002500000000.htm