HIV persistence: silence or resistance?

Alveolar macrophages from persons with HIV mount impaired TNF signaling networks to M. tuberculosis infection

People living with HIV (PLWH) have an increased risk for developing tuberculosis after M. tuberculosis infection, despite anti-retroviral therapy (ART). To delineate the underlying mechanisms, we conducted single cell transcriptomics on bronchoalveolar lavage cells from PLWH on ART and HIV uninfected healthy controls infected with M. tuberculosis ex vivo. We identify an M1-like proinflammatory alveolar macrophage subset that sequentially acquires TNF signaling capacity in controls but not in PLWH. Cell-cell communication analyses reveal interactions between M1-like macrophages and effector memory T cells within TNF superfamily, chemokine, and costimulatory networks in the airways of controls. These interaction networks were lacking in PLWH infected with M. tuberculosis, where anti-inflammatory M2-like alveolar macrophages and T regulatory cells dominated along with dysregulated T cell signatures. Our data support a model in which impaired TNF-TNFR signaling, M2-like alveolar macrophages and aberrant macrophage-T cell crosstalk, lead to ineffective immunity to M. tuberculosis in PLWH on ART.

Nuclear retention of unspliced HIV-1 RNA as a reversible post-transcriptional block in latency

HIV-1 latency is mainly characterized at transcriptional level, and little is known about post-transcriptional mechanisms and their contribution to reactivation. The viral protein Rev controls the nucleocytoplasmic export of unspliced and singly-spliced RNA that is central to proviral replication-competence and is therefore a prerequisite for efficient viral reactivation during the "shock-and-kill" cure therapy. Here we show that during infection and reactivation, unspliced HIV-1 RNA is a subject to complex and dynamic regulation by the Rev cofactor MATR3 and the MTR4 cofactor of the nuclear exosome. MATR3 and MTR4 coexist in the same ribonucleoprotein complex functioning to either maintain or degrade the RNA, respectively, with Rev orchestrating this regulatory switch. Moreover, we provide evidence of nuclear retention of unspliced HIV-1 RNA in ex vivo cultures from 22 ART-treated people with HIV, highlighting a reversible post-transcriptional block to viral RNA nucleocytoplasmic export that is relevant to the design of curative interventions.

Phenotyping Viral Reservoirs to Reveal HIV-1 Hiding Places

PURPOSE OF REVIEW

Despite suppressive antiretroviral therapy (ART), HIV-1 reservoirs persist in various cell types and tissues and reignite active replication if therapy is stopped. Persistence of the viral reservoirs in people with HIV-1 (PWH) is the main obstacle to achieving a cure. Identification and characterization of cellular and tissue HIV-1 reservoirs is thus central to the cure research. Here, we discuss emerging insights into the phenotype of HIV-1 reservoir cells.

RECENT FINDINGS

HIV-1 persists in multiple tissues, anatomic locations, and cell types. Although contributions of different CD4 + T-cell subsets to the HIV-1 reservoir are not equal, all subsets harbor a part of the viral reservoir. A number of putative cellular markers of the HIV-1 reservoir have been proposed, such as immune checkpoint molecules, integrins, and pro-survival factors. CD32a expression was shown to be associated with a very prominent enrichment in HIV-1 DNA, although this finding has been challenged. Recent technological advances allow unbiased single-cell phenotypic analyses of cells harbouring total or intact HIV-1 proviruses. A number of phenotypic markers have been reported by several independent studies to be enriched on HIV-1 reservoir cells. Expression of some of these markers could be mechanistically linked to the reservoir persistence, as they could for instance shield the reservoir cells from the immune recognition or promote their survival. However, so far no single phenotypic marker, or combination of markers, can effectively distinguish HIV-infected from uninfected cells or identify all reservoir cells.

The Proviral Reservoirs of Human Immunodeficiency Virus (HIV) Infection

Human Immunodeficiency Virus (HIV) proviral reservoirs are cells that harbor integrated HIV proviral DNA within their nuclear genomes. These cells form a heterogeneous group, represented by peripheral blood mononuclear cells (PBMCs), tissue-resident lymphoid and monocytic cells, and glial cells of the central nervous system. The importance of studying the properties of proviral reservoirs is connected with the inaccessibility of integrated HIV proviral DNA for modern anti-retroviral therapies (ARTs) that block virus reproduction. If treatment is not effective enough or is interrupted, the proviral reservoir can reactivate. Early initiation of ART improves the prognosis of the course of HIV infection, which is explained by the reduction in the proviral reservoir pool observed in the early stages of the disease. Different HIV subtypes present differences in the number of latent reservoirs, as determined by structural and functional differences. Unique signatures of patients with HIV, such as elite controllers, have control over viral replication and can be said to have achieved a functional cure for HIV infection. Uncovering the causes of this phenomenon will bring humanity closer to curing HIV infection, potential approaches to which include stem cell transplantation, clustered regularly interspaced short palindromic repeats (CRISPR)/cas9, "Shock and kill", "Block and lock", and the application of broad-spectrum neutralizing antibodies (bNAbs).

Archived HIV-1 Drug Resistance Mutations: Role of Proviral HIV-1 DNA Genotype for the Management of Virological Responder People Living with HIV

Despite its effectiveness in controlling plasma viremia, antiretroviral therapy (ART) cannot target proviral DNA, which remains an obstacle to HIV-1 eradication. When treatment is interrupted, the reservoirs can act as a source of viral rebound, highlighting the value of proviral DNA as an additional source of information on an individual's overall resistance burden. In cases where the viral load is too low for successful HIV-1 RNA genotyping, HIV-1 DNA can help identify resistance mutations in treated individuals. The absence of treatment history, the need to adjust ART despite undetectable viremia, or the presence of LLV further support the use of genotypic resistance tests (GRTs) on HIV-1 DNA. Conventionally, GRTs have been achieved through Sanger sequencing, but the advances in NGS are leading to an increase in its use, allowing the detection of minority variants present in less than 20% of the viral population. The clinical significance of these mutations remains under debate, with interpretations varying based on context. Additionally, proviral DNA is subject to APOBEC3-induced hypermutation, which can lead to defective, nonviable viral genomes, a factor that must be considered when performing GRTs on HIV-1 DNA.

Mechanisms and efficacy of small molecule latency-promoting agents to inhibit HIV reactivation ex vivo

Drugs that inhibit HIV transcription and/or reactivation of latent HIV have been proposed as a strategy to reduce HIV-associated immune activation or to achieve a functional cure, yet comparative studies are lacking. We evaluated 26 drugs, including drugs previously reported to inhibit HIV transcription (inhibitors of Tat-dependent HIV transcription, Rev, HSF-1/PTEF-b, HSP90, Jak/Stat, or SIRT1/Tat deacetylation) and other agents that were not tested before (inhibitors of PKC, NF-κB, SP-1, or histone acetyltransferase; NR2F1 agonists), elongation (inhibitors of CDK9/ PTEF-b), completion (inhibitors of PolyA-polymerase), or splicing (inhibitors of human splice factors). To investigate if those drugs would vary in their ability to affect different blocks to HIV transcription, we measured levels of initiated, elongated, midtranscribed, completed, and multiply spliced HIV RNA in PBMCs from antiretroviral therapy-suppressed individuals following ex vivo treatment with each drug and subsequent T cell activation. We identified new drugs that prevent HIV reactivation, including CDK and splicing inhibitors. While some drugs inhibited 1 or 2 steps, other drugs (CDK inhibitors, splicing inhibitors, tanespimycin, and triptolide) inhibited multiple stages of HIV transcription and blocked the production of supernatant viral RNA. These drugs and targets deserve further study in strategies aimed at reducing HIV-associated immune activation or achieving a functional cure.

Persistent HIV-1 transcription during ART: time to reassess its significance?

PURPOSE OF REVIEW

Despite suppressive antiretroviral therapy (ART), HIV-1 reservoirs persist and reignite viral replication if therapy is interrupted. Persistence of the viral reservoir in people with HIV-1 (PWH) is the main obstacle to an HIV-1 cure. The reservoirs are not transcriptionally silent, and viral transcripts can be detected in most ART-treated individuals. Here, we review the recent progress in the characterization of persistent HIV-1 transcription during ART.

RECENT FINDINGS

Evidence from several studies indicates that, although cell-associated unspliced (US) HIV-1 RNA is abundantly expressed in ART-treated PWH, intact full-length US transcripts are rare and most US RNA is derived from defective proviruses. The transcription- and translation-competent defective proviruses, previously considered irrelevant, are increasingly being linked to residual HIV-1 pathogenesis under suppressive ART. Recent data suggest a continuous crosstalk between the residual HIV-1 activity under ART and the immune system. Persistent HIV-1 transcription on ART, despite being mostly derived from defective proviruses, predicts viral rebound upon therapy interruption, suggesting its role as an indicator of the strength of the host antiviral immune response that is shaping the viral rebound.

SUMMARY

In light of the recent findings, the significance of persistent HIV-1 transcription during ART for the long-term health of PWH and the cure research should be reassessed.

Gesicles packaging dCas9-VPR ribonucleoprotein complexes can combine with vorinostat and promote HIV proviral transcription

Despite the success of combination antiretroviral therapy (cART) in HIV treatment, a cure for HIV remains elusive. Scientists postulate that HIV latent reservoirs may be a vital target in curative strategies. Vorinostat is a latency-reversing agent that has demonstrated some effectiveness in reactivating latent HIV, but complementary therapies may be essential to enhance its efficacy. One such approach may utilize the CRISPR-Cas9 system, which has evolved to include transcriptional activators such as dCas9-VPR. In this study, we explored the effects of combining vorinostat coupled with gesicle-mediated delivery of dCas9-VPR in promoting the transcription of integrated HIV proviruses in HIV-NanoLuc CHME-5 microglia and J-Lat 10.6 lymphocytes. We confirmed that dCas9-VPR ribonucleoprotein complexes can be packaged into gesicles and application to cells successfully induced HIV transcription through interactions with the HIV LTR. Vorinostat also induced significant increases in proviral transcription but generated inhibition of cellular proliferation (microglia) or cell viability (lymphocytes) starting at 1,000 nM and higher concentrations. Experiments combining dCas9-VPR gesicles and vorinostat confirmed the enhanced transcriptional activation of the HIV provirus in microglia but not lymphocytes. Thus, a combination of dCas9-VPR gesicles with other latency-reversing agents may provide a complementary method to activate latent HIV in future studies utilizing patient-derived cells or small animal models.

Changing epidemiology of COVID-19: potential future impact on vaccines and vaccination strategies

INTRODUCTION

COVID-19 was an unprecedented challenge worldwide; however, disease epidemiology has evolved, and COVID-19 no longer constitutes a public health emergency of international concern. Nonetheless, COVID-19 remains a global threat and uncertainties remain, including definition of the end of the pandemic and transition to endemicity, and understanding true rates of SARS-CoV-2 infection/transmission.

AREAS COVERED

Six international experts convened (April 2023) to interpret changing COVID-19 epidemiology and public health challenges. We report the panel's recommendations and knowledge gaps in COVID-19 epidemiology, SARS-CoV-2 evolution, and future vaccination strategies, informed by peer-reviewed publications, surveillance data, health authority assessments, and clinical experience.

EXPERT OPINION

High population SARS-CoV-2 immunity indicates the likely end to the pandemic's acute phase. Continued emergence of variants/sublineages that can evade the vaccine-induced antibody response are likely, but widespread immunity reduces the risk of disease severity. Continued surveillance is required to capture transition to endemicity, seasonality, and emergence of novel variants/sublineages, to inform future vaccination strategies. COVID-19 vaccination should be integrated into routine vaccination programs throughout life. Co-circulation with other respiratory viruses should be monitored to avoid a combined peak, which could overrun healthcare systems. Effective, combined vaccines and improved education may help overcome vaccine hesitancy/booster fatigue and increase vaccination uptake.

HIV Infection: Shaping the Complex, Dynamic, and Interconnected Network of the Cytoskeleton

HIV-1 has evolved a plethora of strategies to overcome the cytoskeletal barrier (i.e., actin and intermediate filaments (AFs and IFs) and microtubules (MTs)) to achieve the viral cycle. HIV-1 modifies cytoskeletal organization and dynamics by acting on associated adaptors and molecular motors to productively fuse, enter, and infect cells and then traffic to the cell surface, where virions assemble and are released to spread infection. The HIV-1 envelope (Env) initiates the cycle by binding to and signaling through its main cell surface receptors (CD4/CCR5/CXCR4) to shape the cytoskeleton for fusion pore formation, which permits viral core entry. Then, the HIV-1 capsid is transported to the nucleus associated with cytoskeleton tracks under the control of specific adaptors/molecular motors, as well as HIV-1 accessory proteins. Furthermore, HIV-1 drives the late stages of the viral cycle by regulating cytoskeleton dynamics to assure viral Pr55Gag expression and transport to the cell surface, where it assembles and buds to mature infectious virions. In this review, we therefore analyze how HIV-1 generates a cell-permissive state to infection by regulating the cytoskeleton and associated factors. Likewise, we discuss the relevance of this knowledge to understand HIV-1 infection and pathogenesis in patients and to develop therapeutic strategies to battle HIV-1.

Small non-coding RNAs encoded by RNA viruses: old controversies and new lessons from the COVID-19 pandemic

The recurring outbreaks caused by emerging RNA viruses have fostered an increased interest in the research of the mechanisms that regulate viral life cycles and the pathological outcomes associated with infections. Although interactions at the protein level are well-studied, interactions mediated by RNA molecules are less explored. RNA viruses can encode small non-coding RNAs molecules (sncRNAs), including viral miRNAs (v-miRNAs), that play important roles in modulating host immune responses and viral replication by targeting viral or host transcripts. Starting from the analysis of public databases compiling the known repertoire of viral ncRNA molecules and the evolution of publications and research interests on this topic in the wake of the COVID-19 pandemic, we provide an updated view on the current knowledge on viral sncRNAs, with a focus on v-miRNAs encoded by RNA viruses, and their mechanisms of action. We also discuss the potential of these molecules as diagnostic and prognostic biomarkers for viral infections and the development of antiviral therapies targeting v-miRNAs. This review emphasizes the importance of continued research efforts to characterize sncRNAs encoded by RNA viruses, identifies the most relevant pitfalls in the study of these molecules, and highlights the paradigm changes that have occurred in the last few years regarding their biogenesis, prevalence and functional relevance in the context of host-pathogen interactions.

Hematopoietic stem cells and betaherpesvirus latency

The human betaherpesviruses including human cytomegalovirus (HCMV), human herpesvirus (HHV)-6a and HHV-6b, and HHV-7 infect and establish latency in CD34+ hematopoietic stem and progenitor cells (HPCs). The diverse repertoire of HPCs in humans and the complex interactions between these viruses and host HPCs regulate the viral lifecycle, including latency. Precise manipulation of host and viral factors contribute to preferential maintenance of the viral genome, increased host cell survival, and specific manipulation of the cellular environment including suppression of neighboring cells and immune control. The dynamic control of these processes by the virus regulate inter- and intra-host signals critical to the establishment of chronic infection. Regulation occurs through direct viral protein interactions and cellular signaling, miRNA regulation, and viral mimics of cellular receptors and ligands, all leading to control of cell proliferation, survival, and differentiation. Hematopoietic stem cells have unique biological properties and the tandem control of virus and host make this a unique environment for chronic herpesvirus infection in the bone marrow. This review highlights the elegant complexities of the betaherpesvirus latency and HPC virus-host interactions.