Washington, May 6 : As the HIV disease progresses in an individual infected with the HIV virus the CD8+ T lymphocytes, a group of cells in the immune system, become 'exhausted', resulting in the loss of their abilities to kill other cells infected by the virus.
For many years now, scientists have debated whether this exhaustion of CD8+ T cells is the cause, or the consequence, of persistence of the HIV virus.
In a study published this week in PLoS Medicine, Marcus Altfeld and colleagues studied the immune response over time amongst 18 individuals who had very recently become infected with HIV.
These researchers found that the presence of high amounts of HIV in the blood seemed to cause CD8+ T cell exhaustion; when antigen was reduced, either as a result of treatment with antiretroviral drugs, or evolution of viral epitopes to avoid recognition by CD8+ T cells, these epitope-specific CD8+ T cells recovered some of their original functions.
These findings suggest that CD8+ T cell exhaustion is the consequence, rather than the cause, of persistent replication of HIV.