HIV-1 Tat is present in the serum of people living with HIV-1 despite viral suppression

OBJECTIVES

Despite successful human immunodeficiency virus (HIV) control with combination antiretroviral therapy (cART), individuals with HIV still face health risks, including cancers, cardiovascular and neurocognitive diseases. An HIV protein, Tat, is potentially involved in these HIV-related diseases. Previous studies demonstrated circulating Tat in the blood of untreated people with HIV. Here, we measured Tat levels in the serum of cART-treated people with HIV to examine the effect of cART on Tat production.

METHODS

Serum samples from 63 HIV-positive and 20 HIV-seronegative individuals were analyzed using an ELISA assay that detected Tat concentrations above 2.5 ng/mL.

RESULTS

Among HIV-positive individuals, the Tat level ranged from 0 to 14 ng/mL. 25.4% (16 out of 63) exceeded the 2.5 ng/mL cut-off, with a median HIV Tat level of 4.518 [3.329-8.120] ng/mL. No correlation was revealed between Tat levels and CD4+ T cell counts, serum HIV RNA, p24 antigen, or anti-Tat levels.

CONCLUSIONS

Despite cART, circulating HIV Tat persists and may contribute to HIV-related diseases. This emphasizes the need for further research on the mechanisms of Tat action in non-infected cells where it can penetrate upon circulation in the blood.

Chronic HIV-1 Tat action induces HLA-DR downregulation in B cells: A mechanism for lymphoma immune escape in people living with HIV

Despite the success of combination antiretroviral therapy, people living with human immunodeficiency virus (HIV) still have an increased risk of Epstein-Barr virus (EBV)-associated B cell malignancies. In the HIV setting, B cell physiology is altered by coexistence with HIV-infected cells and the chronic action of secreted viral proteins, for example, HIV-1 Tat that, once released, efficiently penetrates noninfected cells. We modeled the chronic action of HIV-1 Tat on B cells by ectopically expressing Tat or TatC22G mutant in two lymphoblastoid B cell lines. The RNA-sequencing analysis revealed that Tat deregulated the expression of hundreds of genes in B cells, including the downregulation of a subset of major histocompatibility complex (MHC) class II-related genes. Tat-induced downregulation of HLA-DRB1 and HLA-DRB5 genes led to a decrease in HLA-DR surface expression; this effect was reproduced by coculturing B cells with Tat-expressing T cells. Chronic Tat presence decreased the NF-ᴋB pathway activity in B cells; this downregulated NF-ᴋB-dependent transcriptional targets, including MHC class II genes. Notably, HLA-DRB1 and surface HLA-DR expression was also decreased in B cells from people with HIV. Tat-induced HLA-DR downregulation in B cells impaired EBV-specific CD4+ T cell response, which contributed to the escape from immune surveillance and could eventually promote B cell lymphomagenesis in people with HIV.

Specificity of cancer-related chromosomal translocations is linked to proximity after the DNA double-strand break and subsequent selection

Most cancer-related chromosomal translocations appear to be cell type specific. It is currently unknown why different chromosomal translocations occur in different cells. This can be due to either the occurrence of particular translocations in specific cell types or adaptive survival advantage conferred by translocations only in specific cells. We experimentally addressed this question by double-strand break (DSB) induction at MYC, IGH, AML and ETO loci in the same cell to generate chromosomal translocations in different cell lineages. Our results show that any translocation can potentially arise in any cell type. We have analyzed different factors that could affect the frequency of the translocations, and only the spatial proximity between gene loci after the DSB induction correlated with the resulting translocation frequency, supporting the 'breakage-first' model. Furthermore, upon long-term culture of cells with the generated chromosomal translocations, only oncogenic MYC-IGH and AML-ETO translocations persisted over a 60-day period. Overall, the results suggest that chromosomal translocation can be generated after DSB induction in any type of cell, but whether the cell with the translocation would persist in a cell population depends on the cell type-specific selective survival advantage that the chromosomal translocation confers to the cell.

Abstract 6129: The proapoptotic peptide PEP-010 is efficient on several models of different tumor origins and it can be monitored by pharmacodynamic biomarker candidates in clinical practice

In cancer cells, the proapoptotic proteins caspase-9 and PP2A interaction prevents them to play their role in apoptosis. PEP-010, a drug candidate developed by PEP-Therapy, a French Biotech company, is a proapoptotic peptide targeting and disrupting this interaction leading to restoration of the apoptotic cascade. PEP-010 is an innovative bifunctional peptide. It penetrates into cells thanks to its cell penetrating part and specifically disrupts the caspase-9/PP2A interaction thanks to its interfering part. PEP-010 is currently in Phase I a/b multicenter clinical trial for the treatment of advanced solid tumors.To the aim of screening different potential therapeutic targets, to investigate the molecular mechanism-of-action of PEP-010 and to identify potential pharmacodynamic biomarkers, we have tested PEP-010 efficacy on several cell models of different tumor origins. By the Annexin V/Propidium Iodide staining and flow cytometry analysis, we found that PEP-010 induces apoptosis in most of the tested models. One possible mechanism-of-action is an involvement of the PP2A which, once released by PEP-010, could regulate expression and/or activity of different intracellular factors leading to caspases activation and cell death.The identification of the major molecular features involved in PEP-010 mechanism-of-action, were instrumental to identify different pharmacodynamic biomarker candidates (e.g. active caspase-3). Hence, such biomarkers could be useful in clinical practice to monitor the effect of PEP-010 at molecular level. We have compared specific features related to the mechanism-of-action of PEP-010 in sensitive (MDA-MB-231, IGROV1) and not sensitive cell models of different tumor origins and in tissue sections derived from Patient-Derived Xenografts models of breast cancer treated or not with PEP-010. Widely used techniques as immunofluorescent staining and immunohistochemistry were employed, making these results easily transferable in clinical routine.Taken together, our pre-clinical data showed the potential of PEP-010 as an anti-cancer peptide on a wide variety of malignancies and enabled the identification of pharmacodynamic biomarker candidates, important to ease the clinical development.

Citation Format: Rayan Farhat, Laura Dadon, F Nemati, A Rebollo, D Decaudin, Joelle Wiels, Catherine Brenner, Diego Germini. The proapoptotic peptide PEP-010 is efficient on several models of different tumor origins and it can be monitored by pharmacodynamic biomarker candidates in clinical practice. [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 6129.

Epstein-Barr Virus reactivation induces MYC-IGH spatial proximity and t(8;14) in B cells

Burkitt lymphoma (BL) is a B cell malignancy associated with the Epstein-Barr virus (EBV). Most BL cases are characterized by a t(8;14) chromosomal translocation involving the MYC oncogene and the immunoglobulin heavy chain gene (IGH). The role of EBV in promoting this translocation remains largely unknown. Here we provide the experimental evidence that EBV reactivation from latency leads to an increase in the proximity between the MYC and IGH loci, otherwise located far away in the nuclear space both in B-lymphoblastoid cell lines and in patients' B-cells. Specific DNA damage within the MYC locus, followed by the MRE11-dependent DNA repair plays a role in this process. Using a CRISPR/Cas9-based B cell model to induce specific DNA double strand breaks in MYC and IGH loci, we have shown that the MYC-IGH proximity induced by EBV reactivation leads to an increased t(8;14) translocation frequency. This article is protected by copyright. All rights reserved.

Easy and robust electrotransfection protocol for efficient ectopic gene expression and genome editing in human B cells

B-cell lines and primary PBMCs are notoriously hard to transfect, thus making genome editing, ectopic gene expression, or gene silencing experiments particularly tedious. Here we propose a novel efficient and reproducible protocol for electrotransfection of lymphoblastoid, B-cell lymphoma, leukemia cell lines, and B cells from PBMCs. The proposed protocol requires neither costly equipment nor expensive reagents; it can be used with small or large plasmids. Transfection and viability rates of about 79% and 58%, respectively, have been routinely achieved by optimizing the salt concentration in the electrotransfection medium and the amount of plasmid used. A validation of the protocol was obtained via the generation of a TP53^-/- RPMI8866 lymphoblastoid cell line which should prove useful in future hematological and blood cancer studies.

Factors That Affect the Formation of Chromosomal Translocations in Cells

Simple Summary

Chromosomal translocations are products of the erroneous repair of DNA double-strand breaks that result in the illegitimate joining of the two broken chromosomal ends from non-homologous chromosomes. Chromosomal translocations have been linked to aneuploidy, infertility, mental retardation, cancer and other diseases. Here we discuss how chromosomal translocations are formed and explore how different cellular factors contribute to their formation.

Abstract

Chromosomal translocations are products of the illegitimate repair of DNA double-strand breaks (DSBs). Their formation can bring about significant structural and molecular changes in the cell that can be physiologically and pathologically relevant. The induced changes may lead to serious and life-threatening diseases such as cancer. As a growing body of evidence suggests, the formation of chromosomal translocation is not only affected by the mere close spatial proximity of gene loci as potential translocation partners. Several factors may affect formation of chromosomal translocations, including chromatin motion to the potential sources of DSBs in the cell. While these can be apparently random events, certain chromosomal translocations appear to be cell-type-specific. In this review, we discuss how chromosomal translocations are formed and explore how different cellular factors contribute to their formation.

Ectopic expression of HIV-1 Tat modifies gene expression in cultured B cells: implications for the development of B-cell lymphomas in HIV-1-infected patients

An increased frequency of B-cell lymphomas is observed in human immunodeficiency virus-1 (HIV-1)-infected patients, although HIV-1 does not infect B cells. Development of B-cell lymphomas may be potentially due to the action of the HIV-1 Tat protein, which is actively released from HIV-1-infected cells, on uninfected B cells. The exact mechanism of Tat-induced B-cell lymphomagenesis has not yet been precisely identified. Here, we ectopically expressed either Tat or its TatC22G mutant devoid of transactivation activity in the RPMI 8866 lymphoblastoid B cell line and performed a genome-wide analysis of host gene expression. Stable expression of both Tat and TatC22G led to substantial modifications of the host transcriptome, including pronounced changes in antiviral response and cell cycle pathways. We did not find any strong action of Tat on cell proliferation, but during prolonged culturing, Tat-expressing cells were displaced by non-expressing cells, indicating that Tat expression slightly inhibited cell growth. We also found an increased frequency of chromosome aberrations in cells expressing Tat. Thus, Tat can modify gene expression in cultured B cells, leading to subtle modifications in cellular growth and chromosome instability, which could promote lymphomagenesis over time.

HIV-1 Tat Activates Akt/mTORC1 Pathway and AICDA Expression by Downregulating Its Transcriptional Inhibitors in B Cells

HIV-1 infects T cells, but the most frequent AIDS-related lymphomas are of B-cell origin. Molecular mechanisms of HIV-1-induced oncogenic transformation of B cells remain largely unknown. HIV-1 Tat protein may participate in this process by penetrating and regulating gene expression in B cells. Both immune and cancer cells can reprogram communications between extracellular signals and intracellular signaling pathways via the Akt/mTORC1 pathway, which plays a key role in the cellular response to various stimuli including viral infection. Here, we investigated the role of HIV-1 Tat on the modulation of the Akt/mTORC1 pathway in B cells. We found that HIV-1 Tat activated the Akt/mTORC1 signaling pathway; this leads to aberrant activation of activation-induced cytidine deaminase (AICDA) due to inhibition of the AICDA transcriptional repressors c-Myb and E2F8. These perturbations may ultimately lead to an increased genomic instability and proliferation that might cause B cell malignancies.

HIV-1, HAART and cancer: A complex relationship

HIV infected people are at higher risk of developing cancer, although it is globally diminished in the era of highly active antiretroviral treatment (HAART). Recently, antioncogenic properties of some HAART drugs were discovered. We discuss the role of HAART in the prevention and improvement of treatment outcomes of cancers in HIV-infected people. We describe different trends in HAART-cancer relationships: cancer-predisposing as well as cancer-preventing. We cover the roles of particular drug regimens in cancer prevention. We also describe the causes of cancer treatment with HAART drugs in HIV-negative people, including ongoing clinical studies that may directly point to a possible independent anti-oncogenic activity of HAART drugs. We conclude that despite potent antioncogenic activities of every class of HAART drugs reported in preclinical models, the evidence to date indicates that their independent clinical impact in HIV-infected people is limited. Improved cancer prevention strategies besides HAART are needed to reduce HIV-cancer-related mortality.

HIV-1 Tat protein induces aberrant activation of AICDA in human B-lymphocytes from peripheral blood

Individuals infected with human immunodeficiency virus (HIV) are at increased risk for Burkitt lymphoma, a B-cell malignancy which occurs after a chromosomal translocation rearranging the MYC oncogene with an immunoglobulin gene locus, usually the IGH heavy chain gene locus. We have previously reported that the HIV protein Tat which circulates in all HIV-positive individuals whatever their immune status caused an increased rate of colocalization between IGH and MYC in B-cells nuclei. We here present in vitro evidence that Tat activates the expression of the AICDA gene that encodes the activation-induced cytidine deaminase whose physiological function is to create double-strand breaks for immunoglobulin gene maturation. In the presence of Tat, DNA damage was observed concomitantly in both MYC and IGH, followed by DNA repair by nonhomologous end joining. AICDA was further found overexpressed in vivo in peripheral blood B-cells from HIV-infected individuals. Thus, the capacity of Tat to spontaneously penetrate B-cells could be sufficient to favor the occurrence of MYC-IGH oncogenic rearrangements during erroneous repair, a plausible cause for the increased incidence of Burkitt lymphoma in the HIV-infected population.

Metal ions modify DNA-protecting and mutagen-scavenging capacities of the AV-153 1,4-dihydropyridine

1,4-Dihydropyridines (1,4-DHP) possess important biochemical and pharmacological properties, including antioxidant and antimutagenic activities. AV-153-Na, an antimutagenic and DNA-repair enhancing compound was shown to interact with DNA by intercalation. Here we studied DNA binding of several AV-153 salts to evaluate the impact of AV-153 modifications on its DNA binding capacity, the ability to scavenge the peroxynitrite, to protect HeLa and B-cells cells against DNA damage. Affinity of the AV-153 salts to DNA measured by a fluorescence assay was dependent on the metal ion forming a salt in position 4 of the 1,4-DHP, and it decreased as follows: Mg > Na > Ca > Li > Rb > K. AV-153-K and AV-153-Rb could not react chemically with peroxynitrite as opposed to AV-153-Mg and AV-153-Ca, the latter increased the decomposition rate of peroxynitrite. AV-153-Na and AV-153-Ca effectively reduced DNA damage induced by peroxynitrite in HeLa cells, while AV-153-K and AV-153-Rb were less effective, AV-153-Li did not protect the DNA, and AV-153-Mg even caused DNA damage itself. The Na, K, Ca and Mg AV-153 salts were also shown to reduce the level of DNA damage in human B-cells from healthy donors. Thus, metal ions modify both DNA-binding and DNA-protecting effects of the AV-153 salts.

A Comparison of Techniques to Evaluate the Effectiveness of Genome Editing

Genome editing using engineered nucleases (meganucleases, zinc finger nucleases, transcription activator-like effector nucleases) has created many recent breakthroughs. Prescreening for efficiency and specificity is a critical step prior to using any newly designed genome editing tool for experimental purposes. The current standard screening methods of evaluation are based on DNA sequencing or use mismatch-sensitive endonucleases. They can be time-consuming and costly or lack reproducibility. Here, we review and critically compare standard techniques with those more recently developed in terms of reliability, time, cost, and ease of use.

HIV-1 Tat protein induces DNA damage in human peripheral blood B-lymphocytes via mitochondrial ROS production

Human immunodeficiency virus (HIV) infection is associated with B-cell malignancies in patients though HIV-1 is not able to infect B-cells. The rate of B-cell lymphomas in HIV-infected individuals remains high even under the combined antiretroviral therapy (cART) that reconstitutes the immune function. Thus, the contribution of HIV-1 to B-cell oncogenesis remains enigmatic. HIV-1 induces oxidative stress and DNA damage in infected cells via multiple mechanisms, including viral Tat protein. We have detected elevated levels of reactive oxygen species (ROS) and DNA damage in B-cells of HIV-infected individuals. As Tat is present in blood of infected individuals and is able to transduce cells, we hypothesized that it could induce oxidative DNA damage in B-cells promoting genetic instability and malignant transformation. Indeed, incubation of B-cells isolated from healthy donors with purified Tat protein led to oxidative stress, a decrease in the glutathione (GSH) levels, DNA damage and appearance of chromosomal aberrations. The effects of Tat relied on its transcriptional activity and were mediated by NF-κB activation. Tat stimulated oxidative stress in B-cells mostly via mitochondrial ROS production which depended on the reverse electron flow in Complex I of respiratory chain. We propose that Tat-induced oxidative stress, DNA damage and chromosomal aberrations are novel oncogenic factors favoring B-cell lymphomas in HIV-1 infected individuals.

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B-cells of HIV-infected individuals exhibit elevated levels of oxidative stress, DNA damage and chromosomal aberrations.

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Purified HIV-1 Tat protein reproduces this effect and induces oxidative stress and DNA damage in B-cells.

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HIV-1 Tat induces mitochondrial oxidative stress and activates NF-kB in B-cells.

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This condition increases the risk of developing chromosomal abnormalities and translocations.

A One-Step PCR-Based Assay to Evaluate the Efficiency and Precision of Genomic DNA-Editing Tools

Despite rapid progress, many problems and limitations persist and limit the applicability of gene-editing techniques. Making use of meganucleases, TALENs, or CRISPR/Cas9-based tools requires an initial step of pre-screening to determine the efficiency and specificity of the designed tools. This step remains time consuming and material consuming. Here we propose a simple, cheap, reliable, time-saving, and highly sensitive method to evaluate a given gene-editing tool based on its capacity to induce chromosomal translocations when combined with a reference engineered nuclease. In the proposed technique, designated engineered nuclease-induced translocations (ENIT), a plasmid coding for the DNA-editing tool to be tested is co-transfected into carefully chosen target cells along with that for an engineered nuclease of known specificity and efficiency. If the new enzyme efficiently cuts within the desired region, then specific chromosomal translocations will be generated between the two targeted genomic regions and be readily detectable by a one-step PCR or qPCR assay. The PCR product thus obtained can be directly sequenced, thereby determining the exact position of the double-strand breaks induced by the gene-editing tools. As a proof of concept, ENIT was successfully tested in different cell types and with different meganucleases, TALENs, and CRISPR/Cas9-based editing tools.

Functional roles of HIV-1 Tat protein in the nucleus

Human immunodeficiency virus-1 (HIV-1) Tat protein is one of the most important regulatory proteins for viral gene expression in the host cell and can modulate different cellular processes. In addition, Tat is secreted by the infected cell and can be internalized by neighboring cells; therefore, it affects both infected and uninfected cells. Tat can modulate cellular processes by interacting with different cellular structures and signaling pathways. In the nucleus, Tat might be localized either in the nucleoplasm or the nucleolus depending on its concentration. Here we review the distinct functions of Tat in the nucleoplasm and the nucleolus in connection with viral infection and HIV-induced oncogenesis.

High frequency of cultivable human subgroup F adenoviruses in stool samples from a paediatric population admitted to hospital with acute gastroenteritis

The family Adenoviridae consists of five genera of which the genus Mastadenovirus includes human viruses classified into 57 serotypes clustered into seven subgroups (A–G). Serotypes 40 and 41 (subgroup F) are specifically associated with childhood gastroenteritis and are the most common cause of acute gastroenteritis in young children after rotaviruses and noroviruses. Standard methods for laboratory diagnosis of adenovirus infection include electron microscopy (EM) and conventional cell culture (CCC), although it is widely considered that adenoviruses 40 and 41 are difficult to cultivate, such that their circulation is most likely underestimated. One hundred and ten faecal specimens from paediatric patients with gastroenteritis were confirmed positive for adenovirus by EM and/or CCC at the Virology Unit of the University Hospital of Parma, Italy, during the period January 2010–December 2012. They were analysed to determine the actual prevalence of adenovirus 40 and 41 in these patients using PCR and restriction endonuclease analysis, and to evaluate their ability to be cultivated in standard cell lines. The results showed a high prevalence of subgroup F (62.7 %), with serotype 41 (89.8 %) predominating over serotype 40 (10.2 %). Surprisingly, among the 75 adenoviruses isolated by CCC, 37 (49 %) belonged to subgroup F, suggesting a higher capacity of adenovirus 40 and 41 to replicate in cell culture than previously thought. PCR and restriction enzyme techniques provide an efficient means of diagnosing enteric adenoviruses correctly, including subgroup F adenovirus strains in young children with gastroenteritis.

Toll-like receptor 4 is involved in the cell cycle modulation and required for effective human cytomegalovirus infection in THP-1 macrophages

Suitable host cell metabolic conditions are fundamental for the effective development of the human cytomegalovirus (HCMV) lytic cycle. Indeed, several studies have demonstrated the ability of this virus to interfere with cell cycle regulation, mainly by blocking proliferating cells in G1 or G1/S. In the present study, we demonstrate that HCMV deregulates the cell cycle of THP-1 macrophages (a cell line irreversibly arrested in G0) by pushing them into S and G2 phases. Moreover, we show that HCMV infection of THP-1 macrophages leads to Toll-like receptor 4 (TLR4) activation. Since various studies have indicated TLR4 to be involved in promoting cell proliferation, here we investigate the possible role of TLR4 in the observed HCMV-induced cell cycle perturbation. Our data strongly support TLR4 as a mediator of HCMV-triggered cell cycle activation in THP-1 macrophages favouring, in turn, the development of an efficient viral lytic cycle.

Cell-cycle-dependent localization of human cytomegalovirus UL83 phosphoprotein in the nucleolus and modulation of viral gene expression in human embryo fibroblasts in vitro

The nucleolus is a multifunctional nuclear compartment widely known to be involved in several cellular processes, including mRNA maturation and shuttling to cytoplasmic sites, control of the cell cycle, cell proliferation, and apoptosis; thus, it is logical that many viruses, including herpesvirus, target the nucleolus in order to exploit at least one of the above-mentioned functions. Recent studies from our group demonstrated the early accumulation of the incoming ppUL83 (pp65), the major tegument protein of human cytomegalovirus (HCMV), in the nucleolus. The obtained results also suggested that a functional relationship might exist between the nucleolar localization of pp65, rRNA synthesis, and the development of the lytic program of viral gene expression. Here we present new data which support the hypothesis of a potentially relevant role of HCMV pp65 and its nucleolar localization for the control of the cell cycle by HCMV (arrest of cell proliferation in G1-G1/S), and for the promotion of viral infection. We demonstrated that, although the incoming pp65 amount in the infected cells appears to be constant irrespective of the cell-cycle phase, its nucleolar accumulation is prominent in G1 and G1/S, but very poor in S or G2/M. This correlates with the observation that only cells in G1 and G1/S support an efficient development of the HCMV lytic cycle. We propose that HCMV pp65 might be involved in regulatory/signaling pathways related to nucleolar functions, such as the cell-cycle control. Co-immunoprecipitation experiments have permitted to identify nucleolin as one of the nucleolar partners of pp65.