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  • Review Article
  • Published:

Experimental approaches to the study of HIV-1 latency

Nature Reviews Microbiology volume 5, pages 95–106 (2007)Cite this article

Key Points

  • HIV-1 can establish a state of latent infection in resting memory CD4+ T cells. These cells carry a stably integrated copy of the viral genome and persist even in patients who have had prolonged suppression of viraemia to undetectable levels on highly active antiretroviral therapy (HAART).

  • Latently infected cells are rare in vivo and are therefore difficult to detect. Approaches to detection rely on three main types of assay: the isolation of pure populations of resting CD4+ T cells; the detection of integrated HIV-1 DNA in these cells; and the recovery of replication-competent virus from these cells by cellular activation.

  • There are many difficulties associated with these assays. Most of the HIV-1 DNA in the resting CD4+ T cells of viraemic patients is unintegrated and labile, so the assays used must be able to distinguish between integrated and unintegrated HIV-1 DNA. Most of the HIV-1 DNA in resting CD4+ T cells is not replication-competent, therefore special assays are also needed to detect the cells that harbour replication-competent viral genomes. Finally, no single assay can simultaneously demonstrate both integration status and replication-competence. Culture assays on purified resting CD4+ T cells from patients on HAART provide the best indication of the true frequency of latently infected cells.

  • Drug-resistant viruses can enter the latent reservoir and persist there. Developing assays to detect archived resistance is an important research goal.

  • Cell-line models for HIV-1 latency have provided much useful information but suffer from the caveat that continuously proliferating, transformed cells might not accurately mimic the profoundly quiescent G0 state of the cells that harbour latent HIV-1 in vivo.

  • Latently infected resting CD4+ T cells have been demonstrated in a SCID/hu mouse model and in the simian immunodeficiency virus (SIV) model. These systems could prove useful in the development of approaches to target the latent reservoir.

Abstract

Viral latency is a reversibly non-productive state of infection that allows some viruses to evade host immune responses. As a consequence of its tropism for activated CD4+ T cells, HIV-1 can establish latent infection in resting memory CD4+ T cells, which are generated when activated CD4+ T cells return to a quiescent state. Latent HIV-1 persists as a stably integrated but transcriptionally silent provirus. In this state, the virus is unaffected by immune responses or antiretroviral drugs, and this latent reservoir in resting CD4+ T cells is a major barrier to curing the infection. Unfortunately, there is no simple assay to measure the number of latently infected cells in a patient, nor is there an entirely representative in vitro model in which to explore the molecular mechanisms of latency. This Review will consider current approaches to the analysis of HIV-1 latency both in vivo and in vitro.

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Figure 1: A model for the generation of the latent reservoir of HIV-1 in resting CD4+ T cells.
Figure 2: A schematic representation of the HIV lifecycle.
Figure 3: Different assays for latently infected cells detect different cell populations.
Figure 4: Dynamics of the latent reservoir.
Figure 5: An in vitro model for HIV-1 latency.

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Acknowledgements

This work was supported by grants from the National Institutes of Health, by a grant from the Doris Duke Charitable Foundation and by the Howard Hughes Medical Institute.

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  1. Department of Medicine, Johns Hopkins University School of Medicine, 879 BRB 733 N. Broadway, Baltimore, 21205, Maryland, USA

    Yefei Han, Megan Wind-Rotolo, Hung-Chih Yang, Janet D. Siliciano & Robert F. Siliciano

  2. Howard Hughes Medical Institute, 879 BRB 733 N. Broadway, Baltimore, 21205, Maryland, USA

    Robert F. Siliciano

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Supplementary information

41579_2007_BFnrmicro1580_MOESM1_ESM.pdf

Supplementary information S1 (figure) The latent reservoir as an archive of the major viral variants generated during the course of HIV-1 infection. (PDF 198 kb)

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Glossary

Lymphoblast

A T-cell lymphoblast is a T cell that has been activated and entered the cell cycle. It can develop into an effector T cell or a memory T cell.

HIV-1 LTR

(HIV-1 long terminal repeat). DNA sequences of approximately 630 base pairs that are present at the 5′ and 3′ ends of the HIV-1 genome.

Preintegration complex

A high-molecular-weight complex including the viral genome, the transcriptase and integrase enzymes and other viral proteins.

Inverse PCR

This technique allows the DNA that flanks a region of known sequence to be amplified.

Alu PCR

PCR that amplifies DNA that is located between a sequence of interest and an Alu element.

Poisson statistics

A statistical distribution in which the probability of an individual event is small, but the number of opportunities is large enough that several such events can occur.

RT-PCR

Reverse-transcription PCR. A type of PCR in which RNA is converted into double-stranded DNA, which is then amplified.

Viral quasispecies

A closely related viral variant coevolving in a host.

SWI/SNF chromatin-remodelling complex

An enzymatic complex that achieves the remodelling of DNA–nucleosomal architecture and determines transcriptional activity.

Heterochromatic

A high-density region in the nucleus that is thought to contain compacted chromatin structures associated with silent genes.

Alphoid repeat elements

Tandem arrays of 171-bp repeats that are associated with centromeric heterochromatin.

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Han, Y., Wind-Rotolo, M., Yang, HC. et al. Experimental approaches to the study of HIV-1 latency. Nat Rev Microbiol 5, 95–106 (2007). https://doi.org/10.1038/nrmicro1580

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