An In-Depth Comparison of Latent HIV-1 Reactivation in Multiple Cell Model Systems and Resting CD4+ T Cells from Aviremic Patients

Abstract

The possibility of HIV-1 eradication has been limited by the existence of latently infected cellular reservoirs. Studies to examine control of HIV latency and potential reactivation have been hindered by the small numbers of latently infected cells found in vivo. Major conceptual leaps have been facilitated by the use of latently infected T cell lines and primary cells. However, notable differences exist among cell model systems. Furthermore, screening efforts in specific cell models have identified drug candidates for “anti-latency” therapy, which often fail to reactivate HIV uniformly across different models. Therefore, the activity of a given drug candidate, demonstrated in a particular cellular model, cannot reliably predict its activity in other cell model systems or in infected patient cells, tested ex vivo. This situation represents a critical knowledge gap that adversely affects our ability to identify promising treatment compounds and hinders the advancement of drug testing into relevant animal models and clinical trials. To begin to understand the biological characteristics that are inherent to each HIV-1 latency model, we compared the response properties of five primary T cell models, four J-Lat cell models and those obtained with a viral outgrowth assay using patient-derived infected cells. A panel of thirteen stimuli that are known to reactivate HIV by defined mechanisms of action was selected and tested in parallel in all models. Our results indicate that no single in vitro cell model alone is able to capture accurately the ex vivo response characteristics of latently infected T cells from patients. Most cell models demonstrated that sensitivity to HIV reactivation was skewed toward or against specific drug classes. Protein kinase C agonists and PHA reactivated latent HIV uniformly across models, although drugs in most other classes did not.

Ex vivo analysis identifies effective HIV-1 latency–reversing drug combinations

“…Our group and others are exploring single-cell methods to resolve the frequency and amplitude of latency reversal, but with in vivo frequencies on the order of 1 per million, the quantitation of infected cells by such methods is extremely challenging. Flow cytometrybased methods are readily applied to primary cell models of HIV-1 latency in which the frequency of latently infected cells is several orders of magnitude higher, and in those models, latency-reversing agents clearly increase the number of cells expressing HIV-1 genes (13,19,57). Further studies of the fraction of cells induced ex vivo as well as the life span of newly induced cells may address these questions.…”

“…The final DMSO percentage was 0.2% (v/v) for all single and combination treatments. Concentrations were chosen based on previous ex vivo studies with rCD4s from infected individuals as well as studies using in vitro latency models (13,28,29,(32)(33)(34) with the aim of selecting clinically relevant concentrations.…”

“…13). Many LRAs have been identified using these models (13)(14)(15)(16)(17)(18)(19)(20)(21)(22)(23)(24)(25)(26)(27). Histone deacetylase (HDAC) inhibitors in particular have shown high latency-reversing potential in in vitro models.…”

Targeting NF-κB Signaling with Protein Kinase C Agonists As an Emerging Strategy for Combating HIV Latency

“…First, it seems that PKC agonists uniquely showed a broad capacity to reactivate HIV from latency in multiple HIV latency models. 20 Second, anti-CD3/CD38-mediated T cell activation has so far been the most effective approach for reactivating HIV-1 proviruses ex vivo (an efficacy of 7.5% producing unspliced HIV RNA by anti-CD3/CD38 compared to 0.12% using SAHA) and this occurs through PKC signaling. 62 Lastly, only the protein kinase C agonist bryostatin-1 induced significant HIV reactivation from resting CD4 + T cell reservoirs without significant T cell activation.…”

Multifarious immunotherapeutic approaches to cure HIV-1 infection

“…Studies evaluating the extent of latency and potential for its reversal have been varied. 57 The vast majority of viruses in the latent reservoir of patients treated during chronic HIV-1 infection comprise CTL escape mutations, which are rare in the reservoirs of subjects treated during acute infection. 13 Recent work shows that only 12% of proviruses are non-mutated and replication competent.…”