Role of the Ubiquitin Proteasome System (UPS) in the HIV-1 Life Cycle

Serum and CSF biomarkers in asymptomatic patients during primary HIV infection: a randomized study

It is debated whether CNS involvement begins during acute human immunodeficiency virus (HIV) infection in persons without meningitis/encephalitis and whether specific antiretroviral drugs or combinations would be beneficial. Neurologically asymptomatic participants enrolled in a randomized and controlled study comparing three combination antiretroviral regimens (tenofovir alafenamide/emtricitabine plus dolutegravir; darunavir; or both) during primary HIV infection were enrolled. Serum and CSF were collected at baseline and at 12 and 48 (serum only) weeks after treatment initiation. Single molecule array was used to measure neurofilament light chain (NFL), total tau protein (Tau), brain-derived neurotrophic factor, glial fibrillary acidic protein (GFAP) and ubiquitin C-terminal hydrolase. We assessed the longitudinal change in biomarkers over time, in addition to the change in the prevalence of serum NFL concentrations above previously published age-adjusted cut-offs (7 pg/ml if 5-18 years, 10 pg/ml if 18-51 years, 15 pg/ml if 51-61 years, 20 pg/ml if 61-70 years and 35 pg/ml if >70 years). Serum was available from 47 participants at all time points, and CSF was available from 13 participants at baseline and 7 at Week 12. We observed a significant direct serum-to-CSF correlation for NFL (ρ = 0.692, P = 0.009), GFAP (ρ = 0.659, P = 0.014) and brain-derived neurotrophic factor (ρ = 0.587, P = 0.045). Serum (ρ = 0.560, P = 0.046) and CSF NFL (ρ = 0.582, P = 0.037) concentrations were directly associated with CSF HIV RNA levels. We observed a significant decrease over time in serum NFL (P = 0.006) and GFAP (P = 0.006) but not in the other biomarkers. No significant difference was observed among the treatment arms. At baseline, serum and CSF age-adjusted NFL levels were above age-adjusted cut-offs in 23 (48.9%) and four participants (30.8%), respectively; considering serum NFL, this proportion was lower at Weeks 12 (31.9%, P = 0.057) and 48 (27.7%, P = 0.13). A relevant proportion of neurologically asymptomatic participants had abnormal CSF and serum NFL levels during primary HIV infection. NFL and GFAP decreased in serum following combination antiretroviral therapy without significant differences among the treatment arms.

HIV vaccination: Navigating the path to a transformative breakthrough-A review of current evidence

Background and Aim

Human immunodeficiency virus (HIV) remains a significant global health challenge, with approximately 39 million people living with HIV worldwide as of 2022. Despite progress in antiretroviral therapy, achieving the UNAIDS "95-95-95" target to end the HIV epidemic by 2025 faces challenges, particularly in sub-Saharan Africa. The pursuit of an HIV vaccine is crucial, offering durable immunity and the potential to end the epidemic. Challenges in vaccine development include the lack of known immune correlates, suitable animal models, and HIV's high mutation rate. This study aims to explore the current state of HIV vaccine development, focusing on the challenges and innovative approaches being investigated.

Methods

In writing this review, we conducted a search of medical databases such as PubMed, ResearchGate, Web of Science, Google Scholar, and Scopus. The exploration of messenger ribonucleic acid vaccines, which have proven successful in the SARS-CoV-2 pandemic, presents a promising avenue for HIV vaccine development. Understanding HIV-1's ability to infiltrate various bodily compartments, establish reservoirs, and manipulate immune responses is critical. Robust cytotoxic T lymphocytes and broadly neutralizing antibodies are identified as key components, though their production faces challenges. Innovative approaches, including computational learning and advanced drug delivery systems, are being investigated to effectively activate the immune system.

Results and Conclusions

Discrepancies between animal models and human responses have hindered the progress of vaccine development. Despite these challenges, ongoing research is focused on overcoming these obstacles through advanced methodologies and technologies. Addressing the challenges in HIV vaccine development is paramount to realizing an effective HIV-1 vaccine and achieving the goal of ending the epidemic. The integration of innovative approaches and a deeper understanding of HIV-1's mechanisms are essential steps toward this transformative breakthrough.

CRISPR-Cas9 screen of E3 ubiquitin ligases identifies TRAF2 and UHRF1 as regulators of HIV latency in primary human T cells

During HIV infection of CD4+ T cells, ubiquitin pathways are essential to viral replication and host innate immune response; however, the role of specific E3 ubiquitin ligases is not well understood. Proteomics analyses identified 116 single-subunit E3 ubiquitin ligases expressed in activated primary human CD4+ T cells. Using a CRISPR-based arrayed spreading infectivity assay, we systematically knocked out 116 E3s from activated primary CD4+ T cells and infected them with NL4-3 GFP reporter HIV-1. We found 10 E3s significantly positively or negatively affected HIV infection in activated primary CD4+ T cells, including UHRF1 (pro-viral) and TRAF2 (anti-viral). Furthermore, deletion of either TRAF2 or UHRF1 in three JLat models of latency spontaneously increased HIV transcription. To verify this effect, we developed a CRISPR-compatible resting primary human CD4+ T cell model of latency. Using this system, we found that deletion of TRAF2 or UHRF1 initiated latency reactivation and increased virus production from primary human resting CD4+ T cells, suggesting these two E3s represent promising targets for future HIV latency reversal strategies.

IMPORTANCE

HIV, the virus that causes AIDS, heavily relies on the machinery of human cells to infect and replicate. Our study focuses on the host cell's ubiquitination system which is crucial for numerous cellular processes. Many pathogens, including HIV, exploit this system to enhance their own replication and survival. E3 proteins are part of the ubiquitination pathway that are useful drug targets for host-directed therapies. We interrogated the 116 E3s found in human immune cells known as CD4+ T cells, since these are the target cells infected by HIV. Using CRISPR, a gene-editing tool, we individually removed each of these enzymes and observed the impact on HIV infection in human CD4+ T cells isolated from healthy donors. We discovered that 10 of the E3 enzymes had a significant effect on HIV infection. Two of them, TRAF2 and UHRF1, modulated HIV activity within the cells and triggered an increased release of HIV from previously dormant or "latent" cells in a new primary T cell assay. This finding could guide strategies to perturb hidden HIV reservoirs, a major hurdle to curing HIV. Our study offers insights into HIV-host interactions, identifies new factors that influence HIV infection in immune cells, and introduces a novel methodology for studying HIV infection and latency in human immune cells.

Protein Quality Control Systems and ER Stress as Key Players in SARS-CoV-2-Induced Neurodegeneration

The COVID-19 pandemic has brought to the forefront the intricate relationship between SARS-CoV-2 and its impact on neurological complications, including potential links to neurodegenerative processes, characterized by a dysfunction of the protein quality control systems and ER stress. This review article explores the role of protein quality control systems, such as the Unfolded Protein Response (UPR), the Endoplasmic Reticulum-Associated Degradation (ERAD), the Ubiquitin-Proteasome System (UPS), autophagy and the molecular chaperones, in SARS-CoV-2 infection. Our hypothesis suggests that SARS-CoV-2 produces ER stress and exploits the protein quality control systems, leading to a disruption in proteostasis that cannot be solved by the host cell. This disruption culminates in cell death and may represent a link between SARS-CoV-2 and neurodegeneration.

Current drugs for HIV-1: from challenges to potential in HIV/AIDS

The human immunodeficiency virus (HIV) persists in latently infected CD4+T cells and integrates with the host genome until cell death. Acquired immunodeficiency syndrome (AIDS) is associated with HIV-1. Possibly, treating HIV/AIDS is an essential but challenging clinical goal. This review provides a detailed account of the types and mechanisms of monotherapy and combination therapy against HIV-1 and describes nanoparticle and hydrogel delivery systems. In particular, the recently developed capsid inhibitor (Lenacapavir) and the Ainuovirine/tenofovir disoproxil fumarate/lamivudine combination (ACC008) are described. It is interestingly to note that the lack of the multipass transmembrane proteins serine incorporator 3 (SERINC3) and the multipass transmembrane proteins serine incorporator 5 (SERINC5) may be one of the reasons for the enhanced infectivity of HIV-1. This discovery of SERINC3 and SERINC5 provides new ideas for HIV-1 medication development. Therefore, we believe that in treating AIDS, antiviral medications should be rationally selected for pre-exposure and post-exposure prophylaxis to avoid the emergence of drug resistance. Attention should be paid to the research and development of new drugs to predict HIV mutations as accurately as possible and to develop immune antibodies to provide multiple guarantees for the cure of AIDS.

E3 Ubiquitin Ligases in Gammaherpesviruses and HIV: A Review of Virus Adaptation and Exploitation

For productive infection and replication to occur, viruses must control cellular machinery and counteract restriction factors and antiviral proteins. Viruses can accomplish this, in part, via the regulation of cellular gene expression and post-transcriptional and post-translational control. Many viruses co-opt and counteract cellular processes via modulation of the host post-translational modification machinery and encoding or hijacking kinases, SUMO ligases, deubiquitinases, and ubiquitin ligases, in addition to other modifiers. In this review, we focus on three oncoviruses, Epstein-Barr virus (EBV), Kaposi's sarcoma herpesvirus (KSHV), and human immunodeficiency virus (HIV) and their interactions with the ubiquitin-proteasome system via viral-encoded or cellular E3 ubiquitin ligase activity.

Single center, open label dose escalating trial evaluating once weekly oral ixazomib in ART-suppressed, HIV positive adults and effects on HIV reservoir size in vivo

BACKGROUND

Achieving a functional or sterilizing cure for HIV will require identification of therapeutic interventions that reduce HIV reservoir size in infected individuals. Proteasome inhibitors, such as ixazomib, impact multiple aspects of HIV biology including latency, transcription initiation, viral replication, and infected cell killing through the HIV protease - Casp8p41 pathway, resulting in latency reversal and reduced measures of HIV reservoir size ex vivo.

METHODS

We conducted a phase 1b/2a dose escalating, open label trial of weekly oral ixazomib for 24 weeks in antiretroviral (ART)-suppressed, HIV positive adults (NCT02946047). The study was conducted from March 2017 to August 2019 at two tertiary referral centers in the United States. The primary outcomes were safety and tolerability of oral ixazomib. Secondary outcomes included changes in immunologic markers and estimates of HIV reservoir size after ixazomib treatment.

FINDINGS

Sixteen participants completed the study. Ixazomib up to 4mg weekly was safe and well-tolerated, yielding no treatment-emergent events above grade 1. In exploratory analyses, ixazomib treatment was associated with detectable viremia that was below the lower limit of quantification (LLQ) in 9 participants, and viremia that was above LLQ in 4 of 16 participants. While treatment was associated with reduced CD4 counts [baseline 783 cells/ mm³ vs. week-24 724 cells/ mm³ p=0.003], there were no changes in markers of cellular activation, exhaustion or inflammation. Total HIV DNA and proviral sequencing were not altered by ixazomib treatment. Intact proviral DNA assay (IPDA) identified intact proviruses in 14 patients pre-treatment, and in 10/14 of those subjects post treatment values were reduced (P=0.068), allowing a calculated intact proviral half life of 0.6 years (95% CI 0.3, 2.5), compared to 7.1 years (95% CI 3.9, 18, p=0.004) in historical controls. Differentiation Quantitative Viral Outgrowth Assays (dQVOA) identified measurable proviruses in 15 subjects pre-treatment; post-treatment values were numerically reduced in 9, but overall differences were not significantly different.

INTERPRETATION

Our study successfully met its primary endpoint of demonstrating the safety of ixazomib for 24 weeks in HIV infected persons. Exploratory analyses suggest that the effects observed ex vivo of latency reversal and reductions in HIV reservoir size, also occur in vivo. Future controlled studies of ixazomib are warranted.

FUNDING

This study was funded by Millennium Pharmaceuticals Inc..; the Mayo Clinic Foundation; the National Institutes of Health, including the National Institute of Allergy and Infectious Diseases, Division of AIDS, the National Heart, Lung and Blood Institute, the National Institute of Diabetes and Digestive and Kidney Diseases, the National Institute of Neurological Disorders and Stroke, and the National Institute on Drug Abuse. Mayo Clinic also acknowledges generous funding support from Mr. Joseph T. and Mrs. Michele P. Betten.

Alcohol-Induced Lysosomal Damage and Suppression of Lysosome Biogenesis Contribute to Hepatotoxicity in HIV-Exposed Liver Cells

Although the causes of hepatotoxicity among alcohol-abusing HIV patients are multifactorial, alcohol remains the least explored "second hit" for HIV-related hepatotoxicity. Here, we investigated whether metabolically derived acetaldehyde impairs lysosomes to enhance HIV-induced hepatotoxicity. We exposed Cytochrome P450 2E1 (CYP2E1)-expressing Huh 7.5 (also known as RLW) cells to an acetaldehyde-generating system (AGS) for 24 h. We then infected (or not) the cells with HIV-1_ADA then exposed them again to AGS for another 48 h. Lysosome damage was assessed by galectin 3/LAMP1 co-localization and cathepsin leakage. Expression of lysosome biogenesis-transcription factor, TFEB, was measured by its protein levels and by in situ immunofluorescence. Exposure of cells to both AGS + HIV caused the greatest amount of lysosome leakage and its impaired lysosomal biogenesis, leading to intrinsic apoptosis. Furthermore, the movement of TFEB from cytosol to the nucleus via microtubules was impaired by AGS exposure. The latter impairment appeared to occur by acetylation of α-tubulin. Moreover, ZKSCAN3, a repressor of lysosome gene activation by TFEB, was amplified by AGS. Both these changes contributed to AGS-elicited disruption of lysosome biogenesis. Our findings indicate that metabolically generated acetaldehyde damages lysosomes and likely prevents their repair and restoration, thereby exacerbating HIV-induced hepatotoxicity.

Human TRIM5α: Autophagy Connects Cell-Intrinsic HIV-1 Restriction and Innate Immune Sensor Functioning

Human immunodeficiency virus-1 (HIV-1) persists as a global health concern, with an incidence rate of approximately 2 million, and estimated global prevalence of over 35 million. Combination antiretroviral treatment is highly effective, but HIV-1 patients that have been treated still suffer from chronic inflammation and residual viral replication. It is therefore paramount to identify therapeutically efficacious strategies to eradicate viral reservoirs and ultimately develop a cure for HIV-1. It has been long accepted that the restriction factor tripartite motif protein 5 isoform alpha (TRIM5α) restricts HIV-1 infection in a species-specific manner, with rhesus macaque TRIM5α strongly restricting HIV-1, and human TRIM5α having a minimal restriction capacity. However, several recent studies underscore human TRIM5α as a cell-dependent HIV-1 restriction factor. Here, we present an overview of the latest research on human TRIM5α and propose a novel conceptualization of TRIM5α as a restriction factor with a varied portfolio of antiviral functions, including mediating HIV-1 degradation through autophagy- and proteasome-mediated mechanisms, and acting as a viral sensor and effector of antiviral signaling. We have also expanded on the protective antiviral roles of autophagy and outline the therapeutic potential of autophagy modulation to intervene in chronic HIV-1 infection.

Ubiquitin E3 Ligase c-Cbl Is a Host Negative Regulator of Nef Protein of HIV-1

Nef is an accessory protein encoded by human immunodeficiency virus type-1 (HIV-1) and plays important roles in regulating HIV-1 infection and viral replication. Interestingly, HIV-1 Nef can promote degradation of numerous host proteins to disrupt cellular antiviral immune response. However, how HIV-1 Nef is degraded by host factors remains largely unexplored. Here, we identified c-Cbl as a host ubiquitin E3 ligase of HIV-1 Nef. We found that c-Cbl interacts with Nef and reduces protein levels of HIV-1 Nef. Further studies demonstrated that c-Cbl promoted Lys48-linked polyubiquitination of HIV-1 Nef, thus attenuating protein stability of HIV-1 Nef. Importantly, cellular c-Cbl ubiquitinated and degraded Nef proteins produced by HIV-1 NL4-3 virions, and ultimately attenuated HIV-1 virulence for infection of THP1 cells. This study reveals a ubiquitination and proteasome-dependent degradation mechanism of HIV-1 Nef protein, and could provide potential strategies for fighting against HIV-1.

Proteasomal Inhibition Potentiates Latent HIV Reactivation

Despite the success of antiretroviral therapy (ART), ART fails to eradicate the virus and HIV cure has remained beyond the reach of current treatments. ART targets replicating virally infected but not latently infected cells, which have limited expression of factors important for proliferation and cellular activity, including positive transcription elongation factor b (P-TEFb) and nuclear factor κB (NF-κB). Levels of the cyclin T1 (CycT1) subunit of P-TEFb are low to absent in resting T cells, and treatment with proteasome inhibitors (PIs) increases CycT1 protein levels to those of proliferating T cells. In this study, the clinically approved PI bortezomib reactivated latent HIV in latently infected primary CD4+ T cells. Bortezomib not only increased levels of CycT1 but also activated NF-κB. Strikingly, as opposed to most currently researched latency reversing agents (LRAs), bortezomib did not require a second LRA to potently reactivate latent HIV. Effects of bortezomib on resting T cells and reactivation of HIV suggest a possible direction for future attempts to diminish the viral reservoir in HIV+ individuals.

A Bunyavirus-Inducible Ubiquitin Ligase Targets RNA Polymerase IV for Degradation during Viral Pathogenesis in Rice

The ubiquitin-proteasome system (UPS) is an important post-translational regulatory mechanism that controls many cellular functions in eukaryotes. Here, we show that stable expression of P3 protein encoded by Rice grassy stunt virus (RGSV), a negative-strand RNA virus in the Bunyavirales, causes developmental abnormities similar to the disease symptoms caused by RGSV, such as dwarfing and excess tillering, in transgenic rice plants. We found that both transgenic expression of P3 and RGSV infection induce ubiquitination and UPS-dependent degradation of rice NUCLEAR RNA POLYMERASE D1a (OsNRPD1a), one of two orthologs of the largest subunit of plant-specific RNA polymerase IV (Pol IV), which is required for RNA-directed DNA methylation (RdDM). Furthermore, we identified a P3-inducible U-box type E3 ubiquitin ligase, designated as P3-inducible protein 1 (P3IP1), which interacts with OsNRPD1a and mediates its ubiquitination and UPS-dependent degradation in vitro and in vivo. Notably, both knockdown of OsNRPD1 and overexpression of P3IP1 in rice plants induced developmental phenotypes similar to RGSV disease symptomss. Taken together, our findings reveal a novel virulence mechanism whereby plant pathogens target host RNA Pol IV for UPS-dependent degradation to induce disease symptoms. Our study also identified an E3 ubiquitin ligase, which targets the RdDM compotent NRPD1 for UPS-mediated degradation in rice.