Rescue of T cell exhaustion by ingenol mebutate

Inhibitory receptors (IR) and inhibitory ligands function as critical regulators of immune responses by tempering T cell activity to microbial infections and cancers. In humans, several types of persisting viruses such as HIV, HBV and HCV, as well as cancers exploit IR signaling by upregulating IR ligands, resulting in suppression of T cell function (i.e., exhaustion). This allows escape from immune surveillance and continuation of disease. By screening a collection of bioactive small molecules, we identified and validated compounds that restore cytokine production and enhance proliferation of exhausted T cells. Analysis of our top hit ingenol mebutate, a protein kinase C inducing diterpene ester, revealed a role for this molecule in overriding the suppressive signaling cascade mediated by IR signaling on T cells. exhausted virus-specific CD8+ T cells cultured with ingenol mebutate or vehicle