The HIV-1 Vpr Protein: A Multifaceted Target for Therapeutic Intervention

HIV-1 Vpr Functions in Primary CD4+ T Cells

HIV-1 encodes four accesory proteins in addition to its structural and regulatory genes. Uniquely amongst them, Vpr is abundantly present within virions, meaning it is poised to exert various biological effects on the host cell upon delivery. In this way, Vpr contributes towards the establishment of a successful infection, as evidenced by the extent to which HIV-1 depends on this factor to achieve full pathogenicity in vivo. Although HIV infects various cell types in the host organism, CD4+ T cells are preferentially targeted since they are highly permissive towards productive infection, concomitantly bringing about the hallmark immune dysfunction that accompanies HIV-1 spread. The last several decades have seen unprecedented progress in unraveling the activities Vpr possesses in the host cell at the molecular scale, increasingly underscoring the importance of this viral component. Nevertheless, it remains controversial whether some of these advances bear in vivo relevance, since commonly employed cellular models significantly differ from primary T lymphocytes. One prominent example is the "established" ability of Vpr to induce G2 cell cycle arrest, with enigmatic physiological relevance in infected primary T lymphocytes. The objective of this review is to present these discoveries in their biological context to illustrate the mechanisms whereby Vpr supports HIV-1 infection in CD4+ T cells, whilst identifying findings that require validation in physiologically relevant models.

TERT single nucleotide polymorphism rs2736098 but not rs2736100 is associated with telomere length in HIV-infected patients on cART

BACKGROUND

Continuous application of "combination antiretroviral therapy" (cART) has transformed Human immunodeficiency virus (HIV) infection into a manageable chronic disease; however, due to lasting inflammation and cumulative toxicity, progressive pathophysiological changes do occur and potentially lead to accelerated aging, among others, contributing to telomere shortening. The single nucleotide polymorphisms (SNP) rs2736100 and rs2736098 are particularly important for human telomerase (TERT) gene expression. The objective of this study was to evaluate the effects of clinical parameters and single nucleotide polymorphisms in TERT (rs2736100 and rs2736098) on telomere length in HIV-infected patients.

METHODS AND RESULTS

This cross-sectional study included 176 patients diagnosed with HIV infection. Relative telomere length (RTL) was determined by real-time polymerase chain reaction (qPCR), whereas genotyping was performed by polymerase chain reaction, followed by restriction fragment length polymorphism analysis (PCR-RFLP). The mean age of the patients (p = .904), time since HIV diagnosis (p = .220), therapy-related variables such as the cART regimen (0.761), and total cART duration (p = .096) did not significantly affect RTL. TERT rs2736100 genotype showed no association with RTL. However, TERT rs2736098 heterozygotes (GA) had significantly longer telomeres (P = .049) than both homozygotes (GG and AA).

CONCLUSIONS

Our findings support the fact that cellular aging in HIV-infected patients is influenced by the TERT rs2736098 polymorphism.

In silico investigation of binding propensity of hematoxylin derivative and damnacanthal for their potential inhibitory effect on HIV-1 Vpr from different subtypes

HIV-1, the causative agent of AIDS leads to many deaths worldwide though few options are available as therapeutics. To deal with the continuous mutation in the virus genome, requirement of new drugs is always there. Subtype variation plays a crucial role in case of HIV-1 therapeutics development. In this study, we want to investigate some pre examined molecules that can be effective for HIV-1 VPR. Inhibition of several protein-protein interactions with the small molecules will lead to identify some molecules as therapeutics other than the conventional drugs. We retrieved the sequences of different subtypes from the database and representative sequences were identified. Representative structures were modelled and validated using MD simulations. Forty molecules, showing anti Vpr activity in vitro were identified from literature survey and those were docked with each subtype representative structures. Two molecules a stable Hematoxylin Derivative (SHD) and Damnacanthal (D3), these were shown to be bind more effectively for all the subtypes. The stability of the protein and those two small molecule complexes were identified again with MD simulation followed by the binding energy calculation. Thus, these molecules can be thought as any option other than the conventional drug targeting HIV-1 Vpr.Communicated by Ramaswamy H. Sarma.

The influence of viral protein R amino acid substitutions on clinical outcomes in people living with HIV: A systematic review

BACKGROUND

The HIV viral protein R (Vpr) is a multifunction protein involved in the pathophysiology of HIV-1. Recent evidence has suggested that Vpr amino acid substitutions influence the pathophysiology of HIV-1 and clinical outcomes in people living with HIV (PLWH). Several studies have linked Vpr amino acid substitutions to clinical outcomes in PLWH; however, there is no clear consensus as to which amino acids or amino acid substitutions are most important in the pathophysiology and clinical outcomes in PLWH. We, therefore, conducted a systematic review of studies investigating Vpr amino acid substitutions and clinical outcomes in PLWH.

METHODS

PubMed, Scopus and Web of Science databases were searched according to PRISMA guidelines using a search protocol designed specifically for this study.

RESULTS

A total of 22 studies were included for data extraction, comprising 14 cross-sectional and 8 longitudinal studies. Results indicated that Vpr amino acid substitutions were associated with specific clinical outcomes, including disease progressions, neurological outcomes and treatment status. Studies consistently showed that the Vpr substitution 63T was associated with slower disease progression, whereas 77H and 85P were associated with no significant contribution to disease progression.

CONCLUSIONS

Vpr-specific amino acid substitutions may be contributors to clinical outcomes in PLWH, and future studies should consider investigating the Vpr amino acid substitutions highlighted in this review.

An insight into the binding mechanism of Viprinin and its morpholine and piperidine derivatives with HIV-1 Vpr: molecular dynamics simulation, principal component analysis and binding free energy calculation study

HIV-1 Vpr is an accessory protein responsible for a plethora of functions inside the host cell to promote viral pathogenesis. One of the major functions of Vpr is the G₂ cell cycle arrest. Among several small molecule inhibitors, Viprinin, a coumarin derivative, has been shown to specifically inhibit the G₂ cell cycle arrest activity of Vpr thus making it an excellent choice for a lead molecule to design antiretroviral drug. But the exact mechanism of binding of the Viprinin and its two potent derivatives with Vpr is still not understood. In this study with combined molecular docking, molecular dynamics simulation, Molecular Mechanics Poisson-Boltzmann Surface Area (MM-PBSA) method, Principal component analysis and Umbrella sampling simulation, we have explored the binding mechanism of Viprinin and its two derivatives with Vpr. MM-PBSA and Umbrella sampling calculations suggest that Viprinin and ViprininD1 have higher binding energy than ViprininD2. Molecular dynamics simulation shows that the ligands are not very stable inside the initial binding pocket and various hydrophobic interactions are responsible to hold the ligands with Vpr. Vpr backbone Principle Component Analysis (PCA) shows various unique essential motions of Vpr bound with Viprinin and its two derivatives. This study may give detailed insight of the mode of binding of the specified compounds at atomic scale and provide valuable information about the possibility of using these compounds as a potent Vpr inhibitor. Communicated by Ramaswamy H. Sarma.

A Novel Class of HIV-1 Inhibitors Targeting the Vpr-Induced G2-Arrest in Macrophages by New Yeast- and Cell-Based High-Throughput Screening

The human immunodeficiency virus type 1 (HIV-1) accessory protein, Vpr, arrests the cell cycle of the G2 phase, and this Vpr-mediated G2 arrest is implicated in an efficient HIV-1 spread in monocyte-derived macrophages. Here, we screened new candidates for Vpr-targeting HIV-1 inhibitors by using fission yeast- and mammalian cell-based high-throughput screening. First, fission yeast strains expressing the HIV-1 Vpr protein were generated and then treated for 48 h with 20 μM of a synthetic library, including 140,000 chemical compounds. We identified 268 compounds that recovered the growth of Vpr-overexpressing yeast. The selected compounds were then tested in mammalian cells, and those displaying high cytotoxicity were excluded from further cell cycle analysis and imaging-based screening. A flow cytometry analysis confirmed that seven compounds recovered from the Vpr-induced G2 arrest. The cell toxicity and inhibitory effect of HIV-1 replication in human monocyte-derived macrophages (MDM) were examined, and three independent structural compounds, VTD227, VTD232, and VTD263, were able to inhibit HIV-1 replication in MDM. Furthermore, we showed that VTD227, but not VTD232 and VTD263, can directly bind to Vpr. Our results indicate that three new compounds and their derivatives represent new drugs targeting HIV-1 replication and can be potentially used in clinics to improve the current antiretroviral therapy.

The impact of the suppression of highly connected protein interactions on the corona virus infection

Several highly effective Covid-19 vaccines are in emergency use, although more-infectious coronavirus strains, could delay the end of the pandemic even further. Because of this, it is highly desirable to develop fast antiviral drug treatments to accelerate the lasting immunity against the virus. From a theoretical perspective, computational approaches are useful tools for antiviral drug development based on the data analysis of gene expression, chemical structure, molecular pathway, and protein interaction mapping. This work studies the structural stability of virus–host interactome networks based on the graphical representation of virus–host protein interactions as vertices or nodes connected by commonly shared proteins. These graphical network visualization methods are analogous to those use in the design of artificial neural networks in neuromorphic computing. In standard protein-node-based network representation, virus–host interaction merges with virus–protein and host–protein networks, introducing redundant links associated with the internal virus and host networks. On the contrary, our approach provides a direct geometrical representation of viral infection structure and allows the effective and fast detection of the structural robustness of the virus–host network through proteins removal. This method was validated by applying it to H1N1 and HIV viruses, in which we were able to pinpoint the changes in the Interactome Network produced by known vaccines. The application of this method to the SARS-CoV-2 virus–host protein interactome implies that nonstructural proteins nsp4, nsp12, nsp16, the nuclear pore membrane glycoprotein NUP210, and ubiquitin specific peptidase USP54 play a crucial role in the viral infection, and their removal may provide an efficient therapy. This method may be extended to any new mutations or other viruses for which the Interactome Network is experimentally determined. Since time is of the essence, because of the impact of more-infectious strains on controlling the spread of the virus, this method may be a useful tool for novel antiviral therapies.

Host Restriction Factors Modulating HIV Latency and Replication in Macrophages

In addition to CD4⁺ T lymphocytes, myeloid cells and, particularly, differentiated macrophages are targets of human immunodeficiency virus type-1 (HIV-1) infection via the interaction of gp120Env with CD4 and CCR5 or CXCR4. Both T cells and macrophages support virus replication, although with substantial differences. In contrast to activated CD4⁺ T lymphocytes, HIV-1 replication in macrophages occurs in nondividing cells and it is characterized by the virtual absence of cytopathicity both in vitro and in vivo. These general features should be considered in evaluating the role of cell-associated restriction factors aiming at preventing or curtailing virus replication in macrophages and T cells, particularly in the context of designing strategies to tackle the viral reservoir in infected individuals receiving combination antiretroviral therapy. In this regard, we will here also discuss a model of reversible HIV-1 latency in primary human macrophages and the role of host factors determining the restriction or reactivation of virus replication in these cells.

HIV-Associated Neurotoxicity: The Interplay of Host and Viral Proteins

HIV-1 can incite activation of chemokine receptors, inflammatory mediators, and glutamate receptor-mediated excitotoxicity. The mechanisms associated with such immune activation can disrupt neuronal and glial functions. HIV-associated neurocognitive disorder (HAND) is being observed since the beginning of the AIDS epidemic due to a change in the functional integrity of cells from the central nervous system (CNS). Even with the presence of antiretroviral therapy, there is a decline in the functioning of the brain especially movement skills, noticeable swings in mood, and routine performance activities. Under the umbrella of HAND, various symptomatic and asymptomatic conditions are categorized and are on a rise despite the use of newer antiretroviral agents. Due to the use of long-lasting antiretroviral agents, this deadly disease is becoming a manageable chronic condition with the occurrence of asymptomatic neurocognitive impairment (ANI), symptomatic mild neurocognitive disorder, or HIV-associated dementia. In-depth research in the pathogenesis of HIV has focused on various mechanisms involved in neuronal dysfunction and associated toxicities ultimately showcasing the involvement of various pathways. Increasing evidence-based studies have emphasized a need to focus and explore the specific pathways in inflammation-associated neurodegenerative disorders. In the current review, we have highlighted the association of various HIV proteins and neuronal cells with their involvement in various pathways responsible for the development of neurotoxicity.

Structural insights into Cullin4-RING ubiquitin ligase remodelling by Vpr from simian immunodeficiency viruses

Viruses have evolved means to manipulate the host's ubiquitin-proteasome system, in order to down-regulate antiviral host factors. The Vpx/Vpr family of lentiviral accessory proteins usurp the substrate receptor DCAF1 of host Cullin4-RING ligases (CRL4), a family of modular ubiquitin ligases involved in DNA replication, DNA repair and cell cycle regulation. CRL4DCAF1 specificity modulation by Vpx and Vpr from certain simian immunodeficiency viruses (SIV) leads to recruitment, poly-ubiquitylation and subsequent proteasomal degradation of the host restriction factor SAMHD1, resulting in enhanced virus replication in differentiated cells. To unravel the mechanism of SIV Vpr-induced SAMHD1 ubiquitylation, we conducted integrative biochemical and structural analyses of the Vpr protein from SIVs infecting Cercopithecus cephus (SIVmus). X-ray crystallography reveals commonalities between SIVmus Vpr and other members of the Vpx/Vpr family with regard to DCAF1 interaction, while cryo-electron microscopy and cross-linking mass spectrometry highlight a divergent molecular mechanism of SAMHD1 recruitment. In addition, these studies demonstrate how SIVmus Vpr exploits the dynamic architecture of the multi-subunit CRL4DCAF1 assembly to optimise SAMHD1 ubiquitylation. Together, the present work provides detailed molecular insight into variability and species-specificity of the evolutionary arms race between host SAMHD1 restriction and lentiviral counteraction through Vpx/Vpr proteins.

Vpr counteracts the restriction of LAPTM5 to promote HIV-1 infection in macrophages

The HIV-1 accessory proteins Vif, Vpu, and Nef can promote infection by overcoming the inhibitory effects of the host cell restriction factors APOBEC3G, Tetherin, and SERINC5, respectively. However, how the HIV-1 accessory protein Vpr enhances infection in macrophages but not in CD4⁺ T cells remains elusive. Here, we report that Vpr counteracts lysosomal-associated transmembrane protein 5 (LAPTM5), a potent inhibitor of HIV-1 particle infectivity, to enhance HIV-1 infection in macrophages. LAPTM5 transports HIV-1 envelope glycoproteins to lysosomes for degradation, thereby inhibiting virion infectivity. Vpr counteracts the restrictive effects of LAPTM5 by triggering its degradation via DCAF1. In the absence of Vpr, the silencing of LAPTM5 precisely phenocopied the effect of Vpr on HIV-1 infection. In contrast, Vpr did not enhance HIV-1 infection in the absence of LAPTM5. Moreover, LAPTM5 was highly expressed in macrophages but not in CD4⁺ T lymphocytes. Re-expressing LAPTM5 reconstituted the Vpr-dependent promotion of HIV-1 infection in primary CD4⁺ T cells, as observed in macrophages. Herein, we demonstrate the molecular mechanism used by Vpr to overcome LAPTM5 restriction in macrophages, providing a potential strategy for anti-HIV/AIDS therapeutics.

Understanding individual SARS-CoV-2 proteins for targeted drug development against COVID-19

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is the cause of the COVID-19 pandemic, responsible for millions of deaths globally. Even with effective vaccines, SARS-CoV-2 will likely maintain a hold in the human population through gaps in efficacy, percent vaccinated, and arising new strains. Therefore, understanding how SARS-CoV-2 causes widespread tissue damage and the development of targeted pharmacological treatments will be critical in fighting this virus and preparing for future outbreaks. Herein, we summarize the progress made thus far by using in vitro or in vivo models to investigate individual SARS-CoV-2 proteins and their pathogenic mechanisms. We have grouped the SARS-CoV-2 proteins into three categories: host entry, self-acting, and host interacting. This review focuses on the self-acting and host-interacting SARS-CoV-2 proteins and summarizes current knowledge on how these proteins promote virus replication and disrupt host systems, as well as drugs that target the virus and virus interacting host proteins. Encouragingly, many of these drugs are currently in clinical trials for the treatment of COVID-19. Future coronavirus outbreaks will most likely be caused by new virus strains that evade vaccine protection through mutations in entry proteins. Therefore, study of individual self-acting and host-interacting SARS-CoV-2 proteins for targeted therapeutic interventions is not only essential for fighting COVID-19 but also valuable against future coronavirus outbreaks.

Chronic Pain in HIV

The evolution of therapeutics for and management of human immunodeficiency virus-1 (HIV-1) infection has shifted it from predominately manifesting as a severe, acute disease with high mortality to a chronic, controlled infection with a near typical life expectancy. However, despite extensive use of highly active antiretroviral therapy, the prevalence of chronic widespread pain in people with HIV remains high even in those with a low viral load and high CD4 count. Chronic widespread pain is a common comorbidity of HIV infection and is associated with decreased quality of life and a high rate of disability. Chronic pain in people with HIV is multifactorial and influenced by HIV-induced peripheral neuropathy, drug-induced peripheral neuropathy, and chronic inflammation. The specific mechanisms underlying these three broad categories that contribute to chronic widespread pain are not well understood, hindering the development and application of pharmacological and nonpharmacological approaches to mitigate chronic widespread pain. The consequent insufficiencies in clinical approaches to alleviation of chronic pain in people with HIV contribute to an overreliance on opioids and alarming rise in active addiction and overdose. This article reviews the current understanding of the pathogenesis of chronic widespread pain in people with HIV and identifies potential biomarkers and therapeutic targets to mitigate it.

HIV-1 Vpr protein impairs lysosome clearance causing SNCA/alpha-synuclein accumulation in neurons

Despite the promising therapeutic effects of combinatory antiretroviral therapy (cART), 20% to 30% of HIV/AIDS patients living with long term infection still exhibit related cognitive and motor disorders. Clinical studies in HIV-infected patients revealed evidence of basal ganglia dysfunction, tremors, fine motor movement deficits, gait, balance, and increased risk of falls. Among older HIV⁺ adults, the frequency of cases with SNCA/α-synuclein staining is higher than in older healthy persons and may predict an increased risk of developing a neurodegenerative disease. The accumulation of SNCA aggregates known as Lewy Bodies is widely described to be directly linked to motor dysfunction. These aggregates are naturally removed by Macroautophagy/autophagy, a cellular housekeeping mechanism, that can be disturbed by HIV-1. The molecular mechanisms involved in linking HIV-1 proteins and autophagy remain mostly unclear and necessitates further exploration. We showed that HIV-1 Vpr protein triggers the accumulation of SNCA in neurons after decreasing lysosomal acidification, deregulating lysosome positioning, and the expression levels of several proteins involved in lysosomal maturation. Viruses and retroviruses such as HIV-1 are known to manipulate autophagy in order to use it for their replication while blocking the degradative final step, which could destroy the virus itself. Our study highlights how the suppression of neuronal autophagy by HIV-1 Vpr is a mechanism leading to toxic protein aggregation and neurodegeneration.Abbreviations: BLOC1: Biogenesis of Lysosome-related Organelles Complex 1; CART: combinatory antiretroviral therapy; CVB: coxsackievirus; DAPI: 4',6-diamidino-2-phenylindole; DENV: dengue virus; GFP: green fluorescent protein; HCV: hepatitis C virus; HCMV: human cytomegalovirus; HIV: human immunodeficiency virus; Env: HIV-1 envelope glycoproteins; GAPDH: glyceraldehyde-3-phosphate dehydrogenase; VSV: Indiana vesiculovirus; LTR: Long Terminal Repeat; LAMP1: lysosomal associated membrane protein 1; MAP1LC3B/LC3B: microtubule associated protein 1 light chain 3 beta; MLBs: multilamellar bodies; RIPA: Radioimmunoprecipitation assay buffer; SDS-PAGE: sodium dodecyl sulfate-polyacrylamide gel electrophoresis; Tat: transactivator of TAR; TEM: transmission electron microscope; Vpr: Viral protein R.

Mitochondrial changes associated with viral infectious diseases in the paediatric population

Infectious diseases occur worldwide with great frequency in both adults and children, causing 350,000 deaths in 2017, according to the latest World Health Organization reports. Both infections and their treatments trigger mitochondrial interactions at multiple levels: (i) incorporation of damaged or mutated proteins into the complexes of the electron transport chain; (ii) impact on mitochondrial genome (depletion, deletions and point mutations) and mitochondrial dynamics (fusion and fission); (iii) membrane potential impairment; (iv) apoptotic regulation; and (v) generation of reactive oxygen species, among others. Such alterations may result in serious adverse clinical events with considerable impact on the quality of life of the children and could even cause death. Herein, we use a systematic review to explore the association between mitochondrial alterations in paediatric infections including human immunodeficiency virus, cytomegalovirus, herpes viruses, various forms of hepatitis, adenovirus, T-cell lymphotropic virus and influenza. We analyse how these paediatric viral infectious processes may cause mitochondrial deterioration in this especially vulnerable population, with consideration for the principal aspects of research and diagnosis leading to improved disease understanding, management and surveillance.

Characterization of SARS-CoV-2 proteins reveals Orf6 pathogenicity, subcellular localization, host interactions and attenuation by Selinexor

BACKGROUND

SARS-CoV-2 causes COVID-19 which has a widely diverse disease profile. The mechanisms underlying its pathogenicity remain unclear. We set out to identify the SARS-CoV-2 pathogenic proteins that through host interactions cause the cellular damages underlying COVID-19 symptomatology.

METHODS

We examined each of the individual SARS-CoV-2 proteins for their cytotoxicity in HEK 293 T cells and their subcellular localization in COS-7 cells. We also used Mass-Spec Affinity purification to identify the host proteins interacting with SARS-CoV-2 Orf6 protein and tested a drug that could inhibit a specific Orf6 and host protein interaction.

RESULTS

We found that Orf6, Nsp6 and Orf7a induced the highest toxicity when over-expressed in human 293 T cells. All three proteins showed membrane localization in COS-7 cells. We focused on Orf6, which was most cytotoxic and localized to the endoplasmic reticulum, autophagosome and lysosomal membranes. Proteomics revealed Orf6 interacts with nucleopore proteins (RAE1, XPO1, RANBP2 and nucleoporins). Treatment with Selinexor, an FDA-approved inhibitor for XPO1, attenuated Orf6-induced cellular toxicity in human 293 T cells.

CONCLUSIONS

Our study revealed Orf6 as a highly pathogenic protein from the SARS-CoV-2 genome, identified its key host interacting proteins, and Selinexor as a drug candidate for directly targeting Orf6 host protein interaction that leads to cytotoxicity.

In vitro Anti-HIV-1 Activity of the Recombinant HIV-1 TAT Protein Along With Tenofovir Drug

BACKGROUND

HIV-1 TAT protein is essential for the regulation of viral genome transcription. The first exon of TAT protein has a fundamental role in the stimulation of the extrinsic and intrinsic apoptosis pathways, but its anti-HIV activity is not clear yet.

METHODS

In the current study, we firstly cloned the first exon of the TAT coding sequence in the pET-24a expression vector and then protein expression was done in the Rosetta expression host. Next, the expressed TAT protein was purified by Ni-NTA column under native conditions. After that, the protein yield was determined by Bradford kit and NanoDrop spectrophotometry. Finally, the cytotoxicity effect and anti-Scr-HIV-1 activity of the recombinant TAT protein alone and along with Tenofovir drug were assessed by MTT and ELISA, respectively.

RESULTS

The recombinant TAT protein was successfully generated in E. coli, as confirmed by 13.5% SDS-PAGE and western blotting. The protein yield was ~150-200 μg/ml. In addition, the recombinant TAT protein at a certain dose with low toxicity could suppress Scr-HIV replication in the infected HeLa cells (~30%) that was comparable with a low toxic dose of Tenofovir drug (~40%). It was interesting that the recombinant TAT protein could enhance anti-HIV potency of Tenofovir drug up to 66%.

CONCLUSION

Generally, a combination of TAT protein and Tenofovir drug could significantly inhibit HIV-1 replication. It will be required to determine their mechanism of action in the next studies.

ZBTB2 represses HIV-1 transcription and is regulated by HIV-1 Vpr and cellular DNA damage responses

Previously, we reported that cellular transcription factor ZASC1 facilitates DNA-dependent/RNA-independent recruitment of HIV-1 TAT and the cellular elongation factor P-TEFb to the HIV-1 promoter and is a critical factor in regulating HIV-1 transcriptional elongation (PLoS Path e1003712). Here we report that cellular transcription factor ZBTB2 is a novel repressor of HIV-1 gene expression. ZBTB2 strongly co-immunoprecipitated with ZASC1 and was dramatically relocalized by ZASC1 from the cytoplasm to the nucleus. Mutations abolishing ZASC1/ZBTB2 interaction prevented ZBTB2 nuclear relocalization. We show that ZBTB2-induced repression depends on interaction of cellular histone deacetylases (HDACs) with the ZBTB2 POZ domain. Further, ZASC1 interaction specifically recruited ZBTB2 to the HIV-1 promoter, resulting in histone deacetylation and transcription repression. Depleting ZBTB2 by siRNA knockdown or CRISPR/CAS9 knockout in T cell lines enhanced transcription from HIV-1 vectors lacking Vpr, but not from these vectors expressing Vpr. Since HIV-1 Vpr activates the viral LTR by inducing the ATR kinase/DNA damage response pathway, we investigated ZBTB2 response to Vpr and DNA damaging agents. Expressing Vpr or stimulating the ATR pathway with DNA damaging agents impaired ZASC1’s ability to localize ZBTB2 to the nucleus. Moreover, the effects of DNA damaging agents and Vpr on ZBTB2 localization could be blocked by ATR kinase inhibitors. Critically, Vpr and DNA damaging agents decreased ZBTB2 binding to the HIV-1 promoter and increased promoter histone acetylation. Thus, ZBTB2 is recruited to the HIV-1 promoter by ZASC1 and represses transcription, but ATR pathway activation leads to ZBTB2 removal from the promoter, cytoplasmic sequestration and activation of viral transcription. Together, our data show that ZASC1/ZBTB2 integrate the functions of TAT and Vpr to maximize HIV-1 gene expression.

The Human immunodeficiency virus 1 (HIV-1) TAT and VPR proteins, in combination with cellular transcription factors, regulate the switch between transcriptionally active productive infection and the transcriptionally inactive latent state. Previously we reported that ZASC1, a cellular transcription factor linked to multiple squamous cell carcinomas and inherited ataxias, contributes to an RNA-independent, DNA-dependent step in recruiting the TAT/P-TEFb complex that is critical for HIV-1 transcription elongation to the HIV-1 promoter. Here we show ZASC1 interacts with ZBTB2, another cellular transcription factor with strong links to cancer. ZASC1 interaction relocalizes ZBTB2 from the cytoplasm to the HIV-1 promoter in the nucleus where ZBTB2 interacts with cellular HDACs, increases HIV-1 promoter histone deacetylation and represses viral transcription. We show that Vpr-mediated activation of the ATR/DNA damage pathway regulates ZBTB2 relocalization by ZASC1. Thus, the cellular transcription factors ZASC1 and ZBTB2 regulate the transcription elongation activities of HIV-1 TAT and the Vpr activation of the cellular DNA damage response pathway to determine the transcriptional fate of the HIV-1 provirus. These results also have strong implications for the role of ZASC1/ZBTB2 and the DNA damage response in cancer and inherited ataxias.

Virus-Like Particle Mediated CRISPR/Cas9 Delivery for Efficient and Safe Genome Editing

The discovery of designer nucleases has made genome editing much more efficient than before. The designer nucleases have been widely used for mechanistic studies, animal model generation and gene therapy development. However, potential off-targets and host immune responses are issues still need to be addressed for in vivo uses, especially clinical applications. Short term expression of the designer nucleases is necessary to reduce both risks. Currently, various delivery methods are being developed for transient expression of designer nucleases including Zinc Finger Nuclease (ZNF), Transcription Activator-Like Effector Nuclease (TALEN) and Clustered Regularly Interspaced Short Palindromic Repeats/CRISPR-associated (CRISPR/Cas). Recently, virus-like particles are being used for gene editing. In this review, we will talk through commonly used genome editing nucleases, discuss gene editing delivery tools and review the latest literature using virus-like particles to deliver gene editing effectors.

Cross-Species Transmission and Evolution of SIV Chimpanzee Progenitor Viruses Toward HIV-1 in Humanized Mice

The genetic evolution of HIV-1 from its progenitor virus SIV following cross-species transmission is not well understood. Here we simulated the SIVcpz initial transmission to humans using humanized mice and followed the viral evolution during serial passages lasting more than a year. All three SIVcpz progenitor viruses used, namely LB715 and MB897 (group M) as well as EK505 (group N) readily infected hu-mice resulting in chronic viremia. Viral loads increased progressively to higher set-points and the CD4⁺ T cell decline became more pronounced by the end of the second serial passage indicating viral adaptation and increased pathogenicity. Viral genomes sequenced at different time points revealed many non-synonymous variants not previously reported that occurred throughout the viral genome, including the gag, pol, env, and nef genes. These results shed light on the potential changes that the SIVcpz genome had undergone during the initial stages of human infection and subsequent spread.

Impact of HIV-1 Vpr manipulation of the DNA repair enzyme UNG2 on B lymphocyte class switch recombination

Background

HIV-1 Vpr encodes a 14 kDa protein that has been implicated in viral pathogenesis through modulation of several host cell functions. In addition to pro-apoptotic and cytostatic properties, Vpr can redirect cellular E3 ubiquitin ligases (such as DCAF1-Cul4A E3 ligase complex) to target many host proteins and interfere with their functions. Among them, Vpr binds the uracil DNA glycosylase UNG2, which controls genome uracilation, and induces its specific degradation leading to loss of uracil removal activity in infected cells. Considering the essential role of UNG2 in antibody diversification in B-cells, we evaluated the impact of Vpr on UNG2 fate in B lymphocytes and examined the functional consequences of UNG2 modulations on class switch recombination (CSR).

Methods

The impact of Vpr-induced UNG2 deregulation on CSR proficiency was evaluated by using virus-like particles able to deliver Vpr protein to target cells including the murine model CSR B cell line CH12F3 and mouse primary B-cells. Co-culture experiments were used to re-examine the ability of Vpr to be released by HIV-1 infected cells and to effectively accumulate in bystander B-cells. Vpr-mediated UNG2 modulations were monitored by following UNG2 protein abundance and uracil removal enzymatic activity.

Results

In this study we report the ability of Vpr to reduce immunoglobulin class switch recombination (CSR) in immortalized and primary mouse B-cells through the degradation of UNG2. We also emphasize that Vpr is released by producing cells and penetrates bystander B lymphocytes.

Conclusions

This work therefore opens up new perspectives to study alterations of the B-cell response by using Vpr as a specific CSR blocking tool. Moreover, our results raise the question of whether extracellular HIV-1 Vpr detected in some patients may manipulate the antibody diversification process that engineers an adapted response against pathogenic intruders and thereby contribute to the intrinsic B-cell humoral defect reported in infected patients.

Evolution of a concept: From accessory protein to key virulence factor, the case of HIV-1 Vpr

Back in 1989 some studies have shown that the viral protein Vpr was dispensable for HIV-1 replication in vitro. From then the concept of accessory or auxiliary protein for Vpr has emerged and it is still used to date. However, Vpr soon appeared to be very important for in vivo virus spread and pathogenesis. Vpr has been involved in many biological functions including regulation of reverse transcriptase activity, the nuclear import of the pre-integration complex (PIC), HIV-1 transcription, gene splicing, apoptosis and in cell cycle arrest. Thus, we might rather consider Vpr as a true virulence factor instead of just an accessory factor. At present, Vpr can be regarded as a potential and promising target in different strategies aiming to fight infected cells including latently infected cells.

Concise review on optimized methods in production and transduction of lentiviral vectors in order to facilitate immunotherapy and gene therapy

Lentiviral vectors (LVs) have provided an efficient way to integrate our gene of interest into eukaryote cells. Human immunodeficiency virus (HIV)-derived LVs have been vastly studied to become an invaluable asset in gene delivery. This abled LVs to be used in both research laboratories and gene therapy. Pseudotyping HIV-1 based LVs, abled it to transduce different types of cells, especially hematopoietic stem cells. A wide range of tropism, plus to the ability to integrate genes into target cells, made LVs an armamentarium in gene therapy. The third and fourth generations of self-inactivating LVs are being used to achieve safe gene therapy. Not only advanced methods enabled the clinical-grade LV production on a large scale, but also considerably heightened transduction efficiency. One of which is microfluidic systems that revolutionized gene delivery approaches. Since gene therapy using LVs attracted lots of attention to itself, we provided a brief review of LV structure and life-cycle along with methods for improving both LV production and transduction. Also, we mentioned some of their utilization in immunotherapy and gene therapy.

An Overview of Antiretroviral Agents for Treating HIV Infection in Paediatric Population

Paediatric Acquired ImmunoDeficiency Syndrome (AIDS) is a life-threatening and infectious disease in which the Human Immunodeficiency Virus (HIV) is mainly transmitted through Mother-To- Child Transmission (MTCT) during pregnancy, labour and delivery, or breastfeeding. This review provides an overview of the distinct therapeutic alternatives to abolish the systemic viral replication in paediatric HIV-1 infection. Numerous classes of antiretroviral agents have emerged as therapeutic tools for downregulation of different steps in the HIV replication process. These classes encompass Non- Nucleoside Analogue Reverse Transcriptase Inhibitors (NNRTIs), Nucleoside/Nucleotide Analogue Reverse Transcriptase Inhibitors (NRTIs/NtRTIs), INtegrase Inhibitors (INIs), Protease Inhibitors (PIs), and Entry Inhibitors (EIs). Co-administration of certain antiretroviral drugs with Pharmacokinetic Enhancers (PEs) may boost the effectiveness of the primary therapeutic agent. The combination of multiple antiretroviral drug regimens (Highly Active AntiRetroviral Therapy - HAART) is currently the standard therapeutic approach for HIV infection. So far, the use of HAART offers the best opportunity for prolonged and maximal viral suppression, and preservation of the immune system upon HIV infection. Still, the frequent administration of high doses of multiple drugs, their inefficient ability to reach the viral reservoirs in adequate doses, the development of drug resistance, and the lack of patient compliance compromise the complete HIV elimination. The development of nanotechnology-based drug delivery systems may enable targeted delivery of antiretroviral agents to inaccessible viral reservoir sites at therapeutic concentrations. In addition, the application of Computer-Aided Drug Design (CADD) approaches has provided valuable tools for the development of anti-HIV drug candidates with favourable pharmacodynamics and pharmacokinetic properties.

Characterizing the antiviral effect of an ATR inhibitor on human immunodeficiency virus type 1 replication

In the search for new antiviral therapies against human immunodeficiency virus type 1 (HIV-1), several cellular targets are being investigated. Ataxia telangiectasia and Rad3-related protein (ATR) has been implicated in HIV-1 replication, namely during retroviral DNA integration. We studied the effect of the ATR inhibitor ETP-46464 on HIV-1 replication in peripheral blood mononuclear cells (PBMCs) and in the persistently HIV-1-infected cell line H61-D. After treatment with ETP-46464, a significant decrease in virus production was observed in both cell systems. Quantification of viral DNA forms in the acutely infected PBMCs suggests that inhibition could take place in the early phase of the viral life cycle before viral DNA integration. Moreover, after treatment of H61-D cells with 3'-azido-3'-deoxythymidine (AZT), which blocks new reverse transcription events, ETP-46464 decreased viral production, suggesting that inhibition of viral replication occurred in the late phase of the life cycle after viral DNA integration. A decrease in virus production after transfection of 293T cells with an HIV-1 infectious molecular clone also suggested that the effect of ETP-46464 is exerted at a post-integration step. We propose that ETP-46464 produces its inhibitory effect on HIV-1 replication by acting in both the early and late phases of the retroviral replication cycle. Thus, ATR could represent a new target for inhibition of HIV-1 replication.

Peptides derived from the C-terminal domain of HIV-1 Viral Protein R in lipid bilayers: Structure, membrane positioning and gene delivery

Viral protein R (Vpr) is a small accessory protein of 96 amino acids that is present in Human and simian immunodeficiency viruses. Among the very different properties that Vpr possesses we can find cell penetrating capabilities. Based on this and on its capacity to interact with nucleic acids we previously investigated the DNA transfection properties of Vpr and subfragments thereof. We found that fragments of the C-terminal helical domain of Vpr are able to deliver efficiently plasmid DNA into different cell lines. As the amphipathic helix may play a role in the interactions with membranes, we investigated whether insertion of a proline residue in the α-helix modifies the transfection properties of Vpr. Unexpectedly, we found that the resulting Vpr55-82 Pro70 peptide was even more efficient than wild type Vpr55-82 in the gene delivery assays. Using circular dichroism, light scattering and solid-state NMR techniques, we characterized the secondary structure and interactions of Vpr and several mutants with model membranes. A model is proposed where the proline shifts the dissociation equilibrium of the peptide-cargo complex and thereby its endosomal release.

Expression Level of HIV-1 Vif Can Be Fluctuated by Natural Nucleotide Variations in the vif-Coding and Regulatory SA1D2prox Sequences of the Proviral Genome

Vif is required for HIV-1 replication in natural target cells by counteracting host restriction factors, APOBEC3 (A3) proteins. We recently demonstrated that Vif expression level can be changed by naturally occurring single-nucleotide variations within SA1D2prox of the HIV-1 genome. We also found that levels for vif/vpr mRNAs are inversely correlated. While amino acid sequence per se is critical for functionality, Vif expression level modulated by signal sequences in its coding region is likely to be important as well. There are two splicing sites in the region involved in vpr expression. To reveal possible fluctuations of Vif-expression level, we examined SA1D2prox and vif gene by chimeric approaches using HIV-1 subtypes B and C with distinct anti-A3 activity. In this report, recombinant clones in subtype B backbone carrying chimeric sequences with respect to SA1D2prox/vif and those within the vif-coding region were generated. Of these, clones containing vif-coding sequence of subtype C, especially its 3′ region, expressed vif/Vif at a decreased level but did at an increased level for vpr/Vpr. Clones with reduced vif/Vif level grew similarly or slightly better than a parental clone in weakly A3G-positive cells but more poorly in highly A3G-expressing cells. Three clones with this property were also tested for their A3-degrading activity. One of the clones appeared to have some defect in addition to the poor ability to express vif/Vif. Taken all together, our results show that natural variations in the SA1D2prox and vif-coding region can change the Vif-expression level and affect the HIV-1 replication potential.

Differential Contribution of HIV-1 Subtypes B and C to Neurological Disorders: Mechanisms and Possible Treatments

With the introduction of combinatory antiretroviral therapy, patients infected with human immunodeficiency virus type 1 (HIV-1) can live much longer than before. However, the identification of HIV-associated neurocognitive disorder (HAND), especially HIV-associated dementia in 15-20% of patients infected with HIV-1, indicates additional complexity. These disorders turn out to be subtype dependent. Recently, many studies are ongoing trying to understand how the virus induces neuronal injury which could lead to neurological dysfunction. Most of these studies are focusing on the HIV-1 release of proteins such as Tat. However, the exact role of these proteins and their involvement in neuronal degeneration remains unidentified; this is especially true since viral proteins from different HIV-1 subtypes differ in their ability to cause neuronal damage. This review describes the role of different HIV-1 subtypes, identifies probable pathways involved in neuronal damage, the contribution of different HIV-1 subtypes to the progression of HAND, and potential treatments for HAND.

Host-HIV-1 Interactome: A Quest for Novel Therapeutic Intervention

The complex nature and structure of the human immunodeficiency virus has rendered the cure for HIV infections elusive. The advances in antiretroviral treatment regimes and the development of highly advanced anti-retroviral therapy, which primarily targets the HIV enzymes, have dramatically changed the face of the HIV epidemic worldwide. Despite this remarkable progress, patients treated with these drugs often witness inadequate efficacy, compound toxicity and non-HIV complications. Considering the limited inventory of druggable HIV proteins and their susceptibility to develop drug resistance, recent attempts are focussed on targeting HIV-host interactomes that are essential for viral reproduction. Noticeably, unlike other viruses, HIV subverts the host nuclear pore complex to enter into and exit through the nucleus. Emerging evidence suggests a crucial role of interactions between HIV-1 proteins and host nucleoporins that underlie the import of the pre-integration complex into the nucleus and export of viral RNAs into the cytoplasm during viral replication. Nevertheless, the interaction of HIV-1 with nucleoporins has been poorly described and the role of nucleoporins during nucleocytoplasmic transport of HIV-1 still remains unclear. In this review, we highlight the advances and challenges in developing a more effective antiviral arsenal by exploring critical host-HIV interactions with a special focus on nuclear pore complex (NPC) and nucleoporins.

Resistance to the Tat Inhibitor Didehydro-Cortistatin A Is Mediated by Heightened Basal HIV-1 Transcription

Human immunodeficiency virus type 1 (HIV-1) Tat binds the viral RNA structure transactivation-responsive element (TAR) and recruits transcriptional cofactors, amplifying viral mRNA expression. The Tat inhibitor didehydro-cortistatin A (dCA) promotes a state of persistent latency, refractory to viral reactivation. Here we investigated mechanisms of HIV-1 resistance to dCA in vitro Mutations in Tat and TAR were not identified, consistent with the high level of conservation of these elements. Instead, viruses resistant to dCA developed higher Tat-independent basal transcription. We identified a combination of mutations in the HIV-1 promoter that increased basal transcriptional activity and modifications in viral Nef and Vpr proteins that increased NF-κB activity. Importantly, these variants are unlikely to enter latency due to accrued transcriptional fitness and loss of sensitivity to Tat feedback loop regulation. Furthermore, cells infected with these variants become more susceptible to cytopathic effects and immune-mediated clearance. This is the first report of viral escape to a Tat inhibitor resulting in heightened Tat-independent activity, all while maintaining wild-type Tat and TAR.IMPORTANCE HIV-1 Tat enhances viral RNA transcription by binding to TAR and recruiting activating factors. Tat enhances its own transcription via a positive-feedback loop. Didehydro-cortistatin A (dCA) is a potent Tat inhibitor, reducing HIV-1 transcription and preventing viral rebound. dCA activity demonstrates the potential of the "block-and-lock" functional cure approaches. We investigated the viral genetic barrier to dCA resistance in vitro While mutations in Tat and TAR were not identified, mutations in the promoter and in the Nef and Vpr proteins promoted high Tat-independent activity. Promoter mutations increased the basal transcription, while Nef and Vpr mutations increased NF-κB nuclear translocation. This heightened transcriptional activity renders CD4⁺ T cells infected with these viruses more susceptible to cytotoxic T cell-mediated killing and to cell death by cytopathic effects. Results provide insights on drug resistance to a novel class of antiretrovirals and reveal novel aspects of viral transcriptional regulation.

Targeting uracil-DNA glycosylases for therapeutic outcomes using insights from virus evolution

Ung-type uracil-DNA glycosylases are frontline defenders of DNA sequence fidelity in bacteria, plants and animals; Ungs also directly assist both innate and humoral immunity. Critically important in viral pathogenesis, whether acting for or against viral DNA persistence, Ungs also have therapeutic relevance to cancer, microbial and parasitic diseases. Ung catalytic specificity is uniquely conserved, yet selective antiviral drugging of the Ung catalytic pocket is tractable. However, more promising precision therapy approaches present themselves via insights from viral strategies, including sequestration or adaptation of Ung for noncanonical roles. A universal Ung inhibition mechanism, converged upon by unrelated viruses, could also inform design of compounds to inhibit specific distinct Ungs. Extrapolating current developments, the character of such novel chemical entities is proposed.

Potential roles of Nef and Vpu in HIV-1 latency

Latent viral reservoirs in long-living cell populations are the main obstacle to a cure of HIV/AIDS. HIV-1 latency is controlled by the activation status of infected cells and their ability to return to a resting phenotype associated with silencing of viral gene expression. These cellular features are not just determined by the host since HIV-1 has evolved sophisticated mechanisms to alter cellular activation and survival to its advantage. Especially the HIV-1 accessory proteins Nef and Vpu exert numerous activities to promote viral replication and immune evasion affecting the size and preservation of the viral reservoir. Here, we review how antagonistic and synergistic functions of Nef and Vpu might affect HIV-1 latency. We also discuss whether these two accessory factors represent suitable targets to improve the ‘shock and kill’ cure strategy.

Singularities of nevirapine metabolism: from sex-dependent differences to idiosyncratic toxicity

Nevirapine (NVP) is a first-generation non-nucleoside reverse transcriptase inhibitor widely used for the treatment and prophylaxis of human immunodeficiency virus infection. The drug is taken throughout the patient's life and, due to the availability of an extended-release formulation, it is administered once daily. This antiretroviral is one of the scarce examples of drugs with prescription criteria based on sex, in order to prevent adverse reactions. The therapy with NVP has been associated with potentially life-threatening liver and idiosyncratic skin toxicity. Multiple evidence has emerged regarding the formation of electrophilic NVP metabolites as crucial for adverse idiosyncratic reactions. The formation of reactive metabolites that yield covalent adducts with proteins has been demonstrated in patients under NVP-based treatment. Interestingly, several pharmacogenetic- and sex-related factors associated with NVP toxicity can be mechanistically explained by an imbalance toward increased formation of NVP-derived reactive metabolites and/or impaired detoxification capability. Moreover, the haptenation of self-proteins by these reactive species provides a plausible link between NVP bioactivation and immunotoxicity, further supporting the relevance of this toxicokinetics hypothesis. In the current paper, we review the existing knowledge and recent developments on NVP metabolism and their relation to NVP toxicity.

Bis-iridoid and iridoid glycosides: Viral protein R inhibitors from Picrorhiza kurroa collected in Myanmar

Four new bis-iridoid glycosides, saungmaygaosides A-D (1-4), and six known iridoid glycosides (5-10) were isolated from the n-butanol extract of the stems of Picrorhiza kurroa collected in Myanmar. Their structures were elucidated by extensive spectroscopic techniques. All of the isolates were assayed for anti-Vpr activity, using TREx-HeLa-Vpr cells. Among the isolates, saungmaygaoside D (4), sylvestroside IV dimethyl acetal (7), and sweroside (8) were the most potent inhibitors with effective doses of 5 and 10 μM, respectively, without showing any notable cytotoxicities.

HIV-1 Integrase-Targeted Short Peptides Derived from a Viral Protein R Sequence

HIV-1 integrase (IN) inhibitors represent a new class of highly effective anti-AIDS therapeutics. Current FDA-approved IN strand transfer inhibitors (INSTIs) share a common mechanism of action that involves chelation of catalytic divalent metal ions. However, the emergence of IN mutants having reduced sensitivity to these inhibitors underlies efforts to derive agents that antagonize IN function by alternate mechanisms. Integrase along with the 96-residue multifunctional accessory protein, viral protein R (Vpr), are both components of the HIV-1 pre-integration complex (PIC). Coordinated interactions within the PIC are important for viral replication. Herein, we report a 7-mer peptide based on the shortened Vpr (69–75) sequence containing a biotin group and a photo-reactive benzoylphenylalanyl residue, and which exhibits low micromolar IN inhibitory potency. Photo-crosslinking experiments have indicated that the peptide directly binds IN. The peptide does not interfere with IN-DNA interactions or induce higher-order, aberrant IN multimerization, suggesting a mode of action for the peptide that is distinct from clinically used INSTIs and developmental allosteric IN inhibitors. This compact Vpr-derived peptide may serve as a valuable pharmacological tool to identify a potential new pharmacologic site.

Dual role of the chromatin-binding factor PHF13 in the pre- and post-integration phases of HIV-1 replication

Viruses interact with multiple host cell factors. Some of these are required to promote viral propagation, others have roles in inhibiting infection. Here, we delineate the function of the cellular factor PHF13 (or SPOC1), a putative HIV-1 restriction factor. Early in the HIV-1 replication cycle PHF13 increased the number of integrated proviral copies and the number of infected cells. However, after HIV-1 integration, high levels of PHF13 suppressed viral gene expression. The antiviral activity of PHF13 is counteracted by the viral accessory protein Vpr, which mediates PHF13 degradation. Altogether, the transcriptional master regulator and chromatin binding protein PHF13 does not have purely repressive effects on HIV-1 replication, but also promotes viral integration. By the functional characterization of the dual role of PHF13 during the HIV-1 replication cycle, we reveal a surprising and intricate mechanism through which HIV-1 might regulate the switch from integration to viral gene expression. Furthermore, we identify PHF13 as a cellular target specifically degraded by HIV-1 Vpr.

Multilayered and versatile inhibition of cellular antiviral factors by HIV and SIV accessory proteins

HIV-1, the main causative agent of AIDS, and related primate lentiviruses show a striking ability to efficiently replicate throughout the lifetime of an infected host. In addition to their high variability, the acquisition of several accessory genes has enabled these viruses to efficiently evade or counteract seemingly strong antiviral immune responses. The respective viral proteins, i.e. Vif, Vpr, Vpu, Vpx and Nef, show a stunning functional diversity, acting by various mechanisms and targeting a large variety of cellular factors involved in innate and adaptive immunity. A focus of the present review is the accumulating evidence that Vpr, Vpu and Nef not only directly target cellular antiviral factors at the protein level, but also suppress their expression by modulating the activity of immune-regulatory transcription factors such as NF-κB. Furthermore, we will discuss the ability of accessory proteins to act as versatile adaptors, removing antiviral proteins from their sites of action and/or targeting them for proteasomal or endolysosomal degradation. Here, the main emphasis will be on emerging examples for functional interactions, synergisms and switches between accessory primate lentiviral proteins. A better understanding of this complex interplay between cellular immune defense mechanisms and viral countermeasures might facilitate the development of effective vaccines, help to prevent harmful chronic inflammation, and provide insights into the establishment and maintenance of latent viral reservoirs.

Review of Current Cell-Penetrating Antibody Developments for HIV-1 Therapy

The discovery of highly active antiretroviral therapy (HAART) in 1996 has significantly reduced the global mortality and morbidity caused by the acquired immunodeficiency syndrome (AIDS). However, the therapeutic strategy of HAART that targets multiple viral proteins may render off-target toxicity and more importantly results in drug-resistant escape mutants. These have been the main challenges for HAART and refinement of this therapeutic strategy is urgently needed. Antibody-mediated treatments are emerging therapeutic modalities for various diseases. Most therapeutic antibodies have been approved by Food and Drug Administration (FDA) mainly for targeting cancers. Previous studies have also demonstrated the promising effect of therapeutic antibodies against HIV-1, but there are several limitations in this therapy, particularly when the viral targets are intracellular proteins. The conventional antibodies do not cross the cell membrane, hence, the pathogenic intracellular proteins cannot be targeted with this classical therapeutic approach. Over the years, the advancement of antibody engineering has permitted the therapeutic antibodies to comprehensively target both extra- and intra-cellular proteins in various infections and diseases. This review aims to update on the current progress in the development of antibody-based treatment against intracellular targets in HIV-1 infection. We also attempt to highlight the challenges and limitations in the development of antibody-based therapeutic modalities against HIV-1.