The reservoir of latent HIV

Antiretroviral therapy fails to cure HIV-1 infection because latent proviruses persist in resting CD4(+) T cells. T cell activation reverses latency, but <1% of proviruses are induced to release infectious virus after maximum in vitro activation. The noninduced proviruses are generally considered defective but have not been characterized. Analysis of 213 noninduced proviral clones from treated patients showed 88.3% with identifiable defects but 11.7% with intact genomes and normal long terminal repeat (LTR) function. Using direct sequencing and genome synthesis, we reconstructed full-length intact noninduced proviral clones and demonstrated growth kinetics comparable to reconstructed induced proviruses from the same patients. Noninduced proviruses have unmethylated promoters and are integrated into active transcription units. Thus, it cannot be excluded that they may become activated in vivo. The identification of replication-competent noninduced proviruses indicates that the size of the latent reservoir-and, hence, the barrier to cure-may be up to 60-fold greater than previously estimated. Copyright © 2013 Elsevier Inc. All rights reserved.

A stable latent reservoir for HIV-1 in resting CD4+ T-cells precludes cure 1–3 . Curative strategies targeting the reservoir are being tested 4,5 and require accurate, scalable reservoir assays. The reservoir was defined with quantitative viral outgrowth assays (QVOAs) for cells releasing infectious virus following one round of T-cell activation 1 . However, QVOAs and newer assays for cells producing viral RNA after activation 6 may underestimate reservoir size because one round of activation does not induce all proviruses 7 . Many studies rely on simple PCR-based assays to detect proviral DNA regardless of transcriptional status, but the clinical relevance of these assays is unclear, as the vast majority proviruses are defective 7–9 . We describe a novel approach that separately quantifies intact and defective proviruses and show that the dynamics of cells carrying intact and defective proviruses are different in vitro and in vivo, a finding with implications for targeting the intact proviruses that are a barrier to cure.

Dendritic cells (DCs) are potent and versatile antigen-presenting cells, and their ability to migrate is key for the initiation of protective pro-inflammatory as well as tolerogenic immune responses. Recent comprehensive studies have highlighted the importance of DC migration in the maintenance of immune surveillance and