Ingenol 3,20 dibenzoate efficiently reactivates latent HIV

The HIV-1 latent reservoir represents a major barrier to viral eradication in aviremic HIV-1⁺ patients taking antiretroviral therapy (ART). Small compounds and drugs capable of latency reversal that are active in vivo are scarce. Here, we describe a careful characterization of the promising reactivation properties of an emerging candidate, ingenol 3,20 dibenzoate (IDB), in cells from aviremic patients, including the effects on cellular activation. Ingenol, is a protein kinase C (PKC) agonist found in Euphorbiacea, a family of succulent plants from semi-desertic areas of Brazil.

To be able to test candidate drugs in cells from HIV infected, aviremic patients, we formulated a rapid ex vivo assay as follows. After phlebotomy, resting CD4⁺ T cells are isolated via negative magnetic bead purification and cultured in aliquots of 5 × 10⁶ cells/mL RPMI-based culture medium. Cell aliquots are exposed to medium alone (negative control), candidate drug, or antibodies against CD3/CD28 to induce T cell receptor stimulation (positive control). After 48 hours in culture, quantitative rtPCR is performed using culture supernatant HIV-1 viral RNA.

IDB, demonstrated viral reactivation comparable to CD3/28 antibody stimulation (median reactivation = 49% of positive control). CD69, an early marker of T cell activation known to be up-regulated by ingenol, increased in all cell aliquots exposed to ingenol (median florescence intensity = 81% of positive control).

Ingenol represents an exciting latency-reversing agent because it combines a potent reactivation ability with a very low toxicity profile, which sets it apart from other PKC agonists.