Latency: the hidden HIV-1 challenge

Abstract

Eradication of HIV-1 from an infected individual cannot be achieved by current regimens. Viral reservoirs established early during the infection remain unaffected by anti-retroviral therapy for a long time and are able to replenish systemic infection upon interruption of the treatment. Therapeutic targeting of viral latency will require a better understanding of the basic mechanisms underlying the establishment and long-term maintenance of HIV-1 in resting memory CD4 T cells, the most prominent reservoir of transcriptionally silent provirus. Since the molecular mechanisms that permit long term transcriptional control of proviral gene expression in these cells are still obscure, this review aims at summarizing the various aspects of the problem that need to be considered. In particular, this review will focus the attention on the control of transcription imposed by chromatin through various epigenetic mechanisms. Exploring the molecular details of viral latency will provide new insights for eventual future therapeutics that aim at viral eradication.

Figure 1

Schematic description of the HIV-1 life cycle highlighting the various blocks that can delay viral replication leading to prolonged hiding of the virus in the host cell during HAART. These include: (i) pre-integration blocks like the deoxycytidine deaminase APOBEC3G, the cytoplasmic body component TRIM5α (in Old World monkeys), incomplete reverse-transcription and defects in nuclear import; (ii) post-integration blocks such as integration into heterochromatin where transcription is repressed, ineffective RNAPII elongation in the absence of Tat or of key host factors, regulation of NF-kB by Murr-1; (iii) translational blocks induced by RNAi.