Giving immune cells a pep talk

A pep talk for immune cells

Chronic infections like HIV and hepatitis C take hold because they exhaust the immune system.

Exhausted immune cells can be revived though when mixed with fresh cells, researchers at the Emory Vaccine Center have found.

Researchers led by Rafi Ahmed, director of the center, infused CD4 cells (“helper” T cells) in mice infected with lymphocytic choriomeningitis virus (LCMV). As a result, CD8 cells (“killer” T cells), which had mounted an immune response prior to the chronic infection taking hold, were revived, and virus levels decreased by a factor of four after a month.

The cell infusion was especially effective when combined with an antibody that blocks the molecule PD-1, or programmed death 1, which appears on exhausted T cells and inhibits their functioning. The PD-1 antibody helped the T cells revive and enhanced the effectiveness of CD4 cells. In all, the combination of CD4 cells and the PD-1 antibody reduced viral levels by almost ten-fold. The virus was undetectable in some mice.

The helper cells were genetically engineered to recognize LCMV, a difference between mouse experiments and a potential clinical application.

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