Advances in Pediatric HIV-1 Cure Therapies and Reservoir Assays

Abstract

Significant advances in the field of HIV-1 therapeutics to achieve antiretroviral treatment (ART)-free remission and cure for persons living with HIV-1 are being made with the advent of broadly neutralizing antibodies and very early ART in perinatal infection. The need for HIV-1 remission and cure arises due to the inability of ART to eradicate the major reservoir for HIV-1 in resting memory CD4+ T cells (the latent reservoir), and the strict adherence to lifelong treatment. To measure the efficacy of these cure interventions on reservoir size and to dissect reservoir dynamics, assays that are sensitive and specific to intact proviruses are critical. In this review, we provided a broad overview of some of the key interventions underway to purge the reservoir in adults living with HIV-1 and ones under study in pediatric populations to reduce and control the latent reservoir, primarily focusing on very early treatment in combination with broadly neutralizing antibodies. We also summarized assays currently in use to measure HIV-1 reservoirs and their feasibility and considerations for studies in children.

Keywords: cure strategies; intact provirus; pediatric HIV-1 infection; reservoir assays.

Figure 1

Various cure strategies to eradicate HIV-1 infection. Upon infecting the cell, HIV moves to the nucleus where it inserts its cDNA genome into the host genome to form the proviral reservoir. The reservoir is persistent and quiescent and poses a barrier to cure. It needs to be eradicated or reduced substantially to achieve cure or ART free remission. There are several cure interventions currently under study namely “shock and kill”, “block and lock” and gene editing. “Shock and kill” involves the use of latency reversing agents that forces the provirus out of latency and allows it to become transcriptionally active, and with some agents produce virions that can then allow for clearance by the immune system. Broadly neutralizing antibodies (bNAbs), in combination with “shock and kill” strategies may facilitate such immune -mediated clearance. The “block and lock” approach is a more recent approach and involves using latency promoting agents that modify the epigenetic environment of the provirus to keep it in a state of deep latency such that it is not reactivated. Gene editing utilizes different strategies to modify the CCR5 receptor on CD4+ T cells making the cells resistant to infection by HIV-1 R5 tropic strains. Very early and early ART in perinatal infection reduce HIV-1 reservoirs over time and in combination with immune strategies may promote ART-free remission and cure. (Figure created with BioRender.com).

Figure 2

Assays used to measure the HIV-1 reservoir. HIV enters the cell nucleus and forms the proviral reservoir by inserting the cDNA of its genome into the host genome. The proviral reservoir is complex and made of several different species which can be measured using different assays that fall under two categories: Tissue culture-based assays and Molecular assays. Tissue culture-based assays (on the left) can measure the transcriptional competence of the provirus (TILDA) or the replication competence and infectivity of the provirus (QVOA). Molecular assays (on the right) can provide the total concentration of infected cells (single-plex ddPCR) or differentiate between intact and defective proviruses (multi-plex ddPCR). Molecular assays can also be used to study the dynamics of the proviral landscape using near full-length PCR and next generation sequencing technology. All of these assays provide key information about the reservoir dynamics and can be useful in developing and measuring the efficacy of cure interventions. (Figure created with BioRender.com).