Protein turns off HIV-fighting T cells

Armen Hareyan's picture
Advertisement

In HIV-infected patients the body's immune system is unable to fight off the virus. A new study to be published online on November 10th in the Journal of Experimental Medicine shows that T cells in HIV-infected individuals express a protein called TIM-3, which inactivates their virus killing capacity.

Blocking this protein, the study suggests, might one day help patients to eliminate HIV as well as other chronic infections.

Advertisement

Large numbers of virus-fighting T cells can be found in the blood of most chronically infected HIV patients. However these cells eventually become exhausted and cannot function. To identify the cause of this exhaustion, a team of researchers at the University of Toronto, lead by Mario Ostrowski, compared blood from healthy individuals and HIV patients. In the patients, TIM-3 was found on a large number of HIV-specific T cells, and the number of TIM-3-positive cells increased with the severity of infection.

Under normal circumstances, exposing T cells to bits of virus causes the cells to replicate and produce virus-killing chemicals. Cells expressing TIM-3, however, were unreactive and TIM-3 was to blame; disrupting its signals restored the cells' virus-fighting functions. TIM-3 normally gets expressed on T cells after they carry out their normal function, perhaps as a way to turn the cells off and thus prevent excessive inflammation.

However, during HIV infection, persistent TIM-3 expression may help the virus avoid T cell attack.

Whether HIV infection itself induces or sustains TIM-3 is not known. Still, blocking the protein might be a useful way to control virus that persists despite antiretroviral therapy.

Advertisement