Study: TB Bacteria Blunt Immunity

Scientists in India say a protein secreted by the bacterium that causes tuberculosis also dampens early immune responses against the disease.

The bacterium mycobacterium tuberculosis infects at least one-third of the world’s population, with new infections occurring at a rate of about one per second.

But now Joyoti Basu and colleagues at the Bose Institute in Calcutta have evaluated the function of the secreted protein ESAT-6 — previously associated with inefficient immune responses to Mycobacterium tuberculosis — by showing purified ESAT-6 blocks signaling from specialized immune receptor proteins known as Toll-like receptors.

Key to that effect is the specific interaction of ESAT-6 with one of the Toll-like receptors, TLR2, on the surface of macrophages. The researchers found that by binding to TLR2, ESTA-6 induces a signal that shuts down all other Toll-like receptor function.

The scientists say blocking interactions between ESAT-6 and TLR2 might represent a therapeutic option for treating tuberculosis, while simulation of interactions between ESAT-6 and TLR2 could be useful in suppressing excessive inflammation.

The study is detailed in the June issue of Nature Immunology.