The Evolving Understanding of the HIV Reservoir and the Quest for a Cure

For people living with human immunodeficiency virus (HIV), antiretroviral therapy (ART) is a cornerstone of treatment, effectively suppressing viral replication and preventing disease progression. Although, despite the remarkable success of ART, a complete cure remains elusive due to the persistence of the HIV reservoir. Recent research is challenging long-held assumptions about this reservoir, paving the way for innovative therapeutic strategies.

What is the HIV Reservoir?

The HIV reservoir refers to the population of cells that harbor the virus, even when ART reduces viral load in the blood to undetectable levels [2]. These reservoirs are established early in infection and primarily consist of resting CD4+ T cells, but can also include other immune cells [2]. Traditionally, these infected cells were considered “latent,” meaning the HIV within them was completely inactive.

Challenging the Notion of Latency

However, emerging research suggests that the HIV reservoir is more dynamic than previously thought. Scientists are discovering that some reservoir cells are not truly latent but continue to produce viral products, albeit at low levels [1]. This ongoing viral activity contributes to chronic inflammation, which can lead to organ damage and an increased risk of cardiovascular disease.

The Impact of Active Reservoir Cells

The number of these “active” reservoir cells is clinically significant. A higher proportion of active cells correlates with faster viral rebound if ART is interrupted [1]. This highlights the importance of understanding the factors that drive reservoir cell activity and developing strategies to target these cells specifically.

New Tools for Profiling HIV-Infected Cells

Researchers are developing innovative tools to better characterize the HIV reservoir. One such tool, named HIV-seq, allows for detailed profiling of rare HIV-infected cells from individuals with HIV [1]. Studies using HIV-seq have revealed key differences in HIV-infected cells before and after the initiation of ART [1], offering insights into how the reservoir develops and persists.

Immune Therapies and Reservoir Reduction

Recent studies are exploring the potential of immune therapies, such as anti-PD-1 therapy (pembrolizumab), to reduce the HIV reservoir. Research indicates that anti-PD-1 therapies can lead to an expansion of HIV-specific immune cells and a decline in plasma TGFβ, ultimately resulting in reservoir reduction in some individuals [3]. Sustained activation of interferon-stimulated genes (ISGs) appears to play a crucial role in this process [3].

The Future of HIV Cure Research

A deeper understanding of the activity of genes within reservoir cells is crucial for developing new treatment strategies. Potential approaches include eliminating these cells or preventing their ability to produce viral fragments. Ongoing research, utilizing tools like HIV-seq and exploring immune-based therapies, offers hope for ultimately curing HIV infection. While ART remains a highly effective treatment, the pursuit of a cure continues to drive innovation in the field.

Antiretroviral Therapy: A Three-Decade Overview

Antiretroviral therapy (ART) has dramatically altered the clinical course of HIV-1 infection [4]. However, ART does not eliminate the latent viral reservoir, which persists even with sustained viral suppression [4].