Bryostatin-1 Synergizes with Histone Deacetylase Inhibitors to Reactivate HIV-1 from Latency

Abstract

The persistence of latent HIV-infected cellular reservoirs represents the major hurdle to virus eradication on patients treated with HAART. It has been suggested that successful depletion of such latent reservoirs will require a combination of therapeutic agents that can specifically and efficiently act on cells harboring latent HIV-1 provirus. Using Jurkat-LAT-GFP cells, a tractable model of HIV-1 latency, we have found that bryostatin -1 reactivates HIV-1 through a classical PKC-dependent pathway. Bryostatin-1 also activates MAPKs and NF-κB pathways and synergizes with HDAC inhibitors to reactivate HIV-1 from latency. Bryostatin-1 downregulates the expression of the HIV-1 co-receptors CD4 and CXCR4 and prevented de novo HIV-1 infection in susceptible cells. We applied proteomic methods to investigate major changes in protein expression in Jurkat-LAT-GFP under latency and reactivation conditions. We identified up-regulation of proteins that may be involved in the innate anti-HIV-1 response (NKEF-A and MHD2) and in different cell functions (i.e. cofilin-1 and transgelin-2) of the host cells. PKC agonists may represent a valuable pharmacological approach to purge latent HIV from cellular reservoirs and at the moment, the only clinically available PKC agonist is bryostatin-1. This drug has been tested in numerous clinical trials and its pharmacokinetics and toxicity in humans is well known. Moreover, bryostatin-1 potently synergizes with other HDAC inhibitors commonly used in the medical practice such as valproic acid. Therefore, bryostatin-1, alone or in combination with HDAC inhibitors, could be used in HAART treated patients to validate the hypothesis that reactivating HIV-1 from latency could purge HIV-1 reservoirs.

Combination of Biological Screening in a Cellular Model of Viral Latency and Virtual Screening Identifies Novel Compounds That Reactivate HIV-1

“…The J-Lat model for HIV-1 latency, containing either a minimal HIV-1 minigenome or a recombinant full-length virus (38), is useful for the study of the determinants of postintegration latency associated with distinct integration events (4, 5, 22-24, 41, 48, 49, 59, 80) or to investigate the reactivating potential of several agents (21,52,57,62,66,68,79,81,83). Latency is established due to transcriptional silencing (i.e., the repression of the integrated HIV-1 promoter).…”

An HIV-1 Replication Pathway Utilizing Reverse Transcription Products That Fail To Integrate

“…Understanding the various forms of HIV-1 latency as well as the mechanisms for the establishment, maintenance, and subsequent activation of latent viruses is necessary for the development of shock-and-kill therapies intended to clear latently infected cells (119)(120)(121). HIV-1 gene expression from latently integrated genomes is inducible by T cell activation (8,(122)(123)(124) and by the synergistic activities (125,126) of protein kinase C (PKC) activators (127) and agents that promote chromatin remodeling, including histone deacetylase inhibitors (HDACi), such as trichostatin A (TSA) (128,129). HDACi have recently been shown to increase expression from integrase mutant lentiviral vectors in both dividing and nondividing cells (130).…”

Molecular mechanisms of HIV latency

“…Because amounts of transcriptional CDKs are low in resting cells, they must be increased for HIV gene expression (58). PKC agonists, including phorbol esters, prostratin, bryostatin, and ingenol, can accomplish this task (74,(83)(84)(85)(86)(87)(88). These compounds have appreciable toxicity, and most of them cannot be administered orally.…”