Reverse Transcriptase Assay Research Articles

Product Enhanced Reverse Transcriptase for assessing replication competent virus in vectors retroviral vectors pseudotyped with GALV and VSV-G envelopes

We evaluated the use of the Product Enhanced Reverse Transcriptase (PERT) assay as a means of detecting virus in retroviral vectors products pseudotyped with Gibbon Ape Leukemia Virus (GALV) and Vesicular Stomatitis Virus G (VSVG) envelopes. PERT provides greater standardization than the S+/L- assay which has been used extensively in virus detection. A challenge is that PERT will also detect residual retroviral vectors as vector particles contain reverse transcriptase. Vector products were cultured for 3 weeks on HEK293 cells to amplify any potential virus. In addition, vector supernatant and end-of-production cells were spiked with GALV to evaluate for inhibition by the test article. Results of PERT and the S+/L- assay were compared. PERT and S+/L- assays were both effective in detecting virus. Vector supernatants were negative at the end of 3 weeks of culture by PERT for both GAVL and VSVG pseudotyped vector. In contrast, end-of-production cells were positive by PERT due to persistent vector producing cells. A one-week culture of cell-free media obtained at the 3 weeks timepoint allowed distinction of virus-free test articles from those with virus. The PERT assay is suitable for detecting replication competent retrovirus in vector products pseudotyped with GALV and VSVG envelopes.

Interplay between protease and reverse transcriptase dimerization in a model HIV-1 polyprotein.

The Gag-Pol polyprotein in human immunodeficiency virus type I (HIV-1) encodes enzymes that are essential for virus replication: protease (PR), reverse transcriptase (RT), and integrase (IN). The mature forms of PR, RT and IN are homodimer, heterodimer and tetramer, respectively. The precise mechanism underlying the formation of dimer or tetramer is not yet understood. Here, to gain insight into the dimerization of PR and RT in the precursor, we prepared a model precursor, PR-RT, incorporating an inactivating mutation at the PR active site, D25A, and including two residues in the p6* region, fused to a SUMO-tag, at the N-terminus of the PR region. We also prepared two mutants of PR-RT containing a dimer dissociation mutation either in the PR region, PR(T26A)-RT, or in the RT region, PR-RT(W401A). Size exclusion chromatography showed both monomer and dimer fractions in PR-RT and PR(T26A)-RT, but only monomer in PR-RT(W401A). SEC experiments of PR-RT in the presence of protease inhibitor, darunavir, significantly enhanced the dimerization. Additionally, SEC results suggest an estimated PR-RT dimer dissociation constant that is higher than that of the mature RT heterodimer, p66/p51, but slightly lower than the premature RT homodimer, p66/p66. Reverse transcriptase assays and RT maturation assays were performed as tools to assess the effects of the PR dimer-interface on these functions. Our results consistently indicate that the RT dimer-interface plays a crucial role in the dimerization in PR-RT, whereas the PR dimer-interface has a lesser role.

Identification of new triazolo annulated dipyridodiazepine derivatives as HIV-1 reverse transcriptase inhibitors: Design, synthesis, DFT, molecular modelling and in silico studies

With the tremendous increase in viral infection spread and drug resistance, it is imperative to explore new efficient antiviral agents. Two series of novel compounds, triazole-annulated dipyridodiazepines 9(a–e) and methyl-substituted triazole-annulated dipyridodiazepines 10(a–e), were successfully synthesised and characterised by IR, NMR spectroscopy and mass spectrometry. The in vitro reverse transcriptase inhibitory ability of synthesized derivatives was determined using an HIV-1 reverse transcriptase assay kit. Results revealed that 9a and 10a were most potent with an IC50 of 66 and 71 nM compared with reference drug nevirapine 88nM. A density functional theory (DFT) study of the synthesized compound showed that both triazole series possess noticeably distorted butterfly-like structures, triazole and pyridine rings tilted relative to the diazepine ring and the phenyl ring is perpendicular to the diazepine ring. Significant HOMO/LUMO gap values for both series, 3.71–4.59 eV for the compounds 9(a–e) and 3.69–4.68 eV for compounds 10(a–e), suggest their quite noticeable stability. Further, these analogues were in silico analysed for molecular docking, drug-likeness, physicochemical and ADMET studies. The good binding scores (high interaction energies) obtained in the molecular docking studies are in good agreement with the molecular electrostatic potential (MEP) analysis results showing accumulations of negative and positive electrostatic potential on different parts of the molecules of the compounds studied. In conclusion, all these results suggest that synthesized analogues could be a potential candidate to inhibit HIV-1 reverse transcriptase and may be considered as lead molecules in the development of new anti-reverse transcriptase agents.

HIV-1 Resistance to Islatravir/Tenofovir Combination Therapy in Wild-Type or NRTI-Resistant Strains of Diverse HIV-1 Subtypes.

Tenofovir disoproxil fumarate (TDF) and islatravir (ISL, 4'-ethynyl-2-fluoro-2'-deoxyadensine, or MK-8591) are highly potent nucleoside reverse transcriptase inhibitors. Resistance to TDF and ISL is conferred by K65R and M184V, respectively. Furthermore, K65R and M184V increase sensitivity to ISL and TDF, respectively. Therefore, these two nucleoside analogs have opposing resistance profiles and could present a high genetic barrier to resistance. To explore resistance to TDF and ISL in combination, we performed passaging experiments with HIV-1 WT, K65R, or M184V in the presence of ISL and TDF. We identified K65R, M184V, and S68G/N mutations. The mutant most resistant to ISL was S68N/M184V, yet it remained susceptible to TDF. To further confirm our cellular findings, we implemented an endogenous reverse transcriptase assay to verify in vitro potency. To better understand the impact of these resistance mutations in the context of global infection, we determined potency of ISL and TDF against HIV subtypes A, B, C, D, and circulating recombinant forms (CRF) 01_AE and 02_AG with and without resistance mutations. In all isolates studied, we found K65R imparted hypersensitivity to ISL whereas M184V conferred resistance. We demonstrated that the S68G polymorphism can enhance fitness of drug-resistant mutants in some genetic backgrounds. Collectively, the data suggest that the opposing resistance profiles of ISL and TDF suggest that a combination of the two drugs could be a promising drug regimen for the treatment of patients infected with any HIV-1 subtype, including those who have failed 3TC/FTC-based therapies.

Withania somnifera extracts induced attenuation of HIV-1: a mechanistic approach to restrict viral infection

BackgroundSeveral anti-retroviral drugs are available against Human immunodeficiency virus type-1, but have multiple adverse side effects. Hence, there is an incessant compulsion for effectual anti-retroviral agents with minimal or no intricacy. Traditionally, natural products have been the most successful source for the development of new medications. Withania somnifera, also known as Ashwagandha, is the utmost treasured medicinal plant used in Ayurveda, which holds the potential to give adaptogenic, immunomodulatory, and antiviral effects. However, its effect on HIV-1 replication at the cellular level has never been explored. Herein, we focused on the anti-HIV-1 activity and the probable mechanism of action of hydroalcoholic and aqueous extracts of Withania somnifera roots and its phytomolecules.MethodsThe cytotoxicity of the extracts was determined through MTT assay, while the in vitro anti-HIV-1 activity was assessed in TZM-bl cells against the HIV-1 strains of X4 and R5 subtypes. Results were confirmed in peripheral blood mononuclear cells, using the HIV-1 p24 antigen assay. Additionally, the mechanism of action was determined through the Time of Addition assay, which was further validated through the series of enzymatic assays, i.e. HIV-1 Integrase, Reverse transcriptase, and Protease assays. To explore the role of the identified active metabolites of Withania somnifera in antiretroviral activity, molecular docking analyses were performed against these key HIV-1 replication enzymes.ResultsThe hydroalcoholic and aqueous extracts of Withania somnifera roots were found to be safer at the sub-cytotoxic concentrations and exhibited their ability to inhibit replication of two primary isolates of HIV-1 through cell-associated and cell-free assays, in dose-dependent kinetics. Several active phytomolecules found in Withania somnifera successfully established hydrogens bonds in the active binding pocket site residues responsible for the catalytic activity of HIV replication and therefore, signifying their role in the attenuation of HIV-1 infection as implied through the in silico molecular docking studies.ConclusionsOur research identified both the hydroalcoholic and aqueous extracts of Withania somnifera roots as potent inhibitors of HIV-1 infection. The in silico analyses also indicated the key components of Withania somnifera with the highest binding affinity against the HIV-1 Integrase by 12-Deoxywithastramonolide and 27-Hydroxywithanone, HIV-1 Protease by Ashwagandhanolide and Withacoagin, and HIV-1 Reverse transcriptase by Ashwagandhanolide and Withanolide B, thereby showing possible mechanisms of HIV-1 extenuation. Overall, this study classified the role of Withania somnifera extracts and their active compounds as potential agents against HIV-1 infection.

Resveratrol oligomers from roots of Ampelocissus martini Planch.

Phytochemical investigation of roots of Ampelocissus martini Planch. (Vitaceae family) led to the isolation of five resveratrol oligomers comprising (−)-ampelopsin F (1), (+)-hopeaphenol (2), (−)-α-viniferin (3), (−)-wilsonol A (4) and (−)-stenophyllol B (5). The structure elucidation was performed using their spectroscopic data as well as comparison with those of literature data. All the isolated compounds were submitted to anti-HIV-1 activities employing the syncytium inhibition assay, using the ΔTat/RevMC99 virus and 1A2 cell line system, and the reverse transcriptase (RT) assay. The results revealed that the enzymatic inhibition of tested compounds except compound 1 exhibited the potential inhibition in anti-HIV 1-RT assay with IC50 in the range of 1.68–5.85 μM better than the positive control, navirapin (IC50 at 7.77 μM). Based on the results, their activities displayed the RT enzymatic inhibition better than the positive control. In addition, the chemical isolation of A. martini was studied for the first time herein. All known secondary metabolites except compound 2 were firstly reported from Ampelocissus genus. Furthermore, the chemotaxonomic significance of the isolates was discussed.

Pyridine/Pyrimidine Substituted Imidazol-5-one Analogs as HIV-1 RT Inhibitors: Design, Synthesis, Docking and Molecular Dynamic Simulation Studies.

This paper reports the synthesis, Non-nucleoside reverse transcriptase inhibitory (NNRTIs) activity and computational studies of 2-((4-chloro-2-subtitutedphenoxy) methyl)-4-(furan-2-ylmethylene)-1-substituted Pyridine/-pyrimidine-1H-imidazol-5(4H)-ones. The imidazol-5-one analogs were synthesized by conventional method and characterized by FT-IR, NMR and mass spectral data. All compounds were evaluated for in-vitro NNRTI activity by using reverse transcriptase (RT) assay kit (Roche). The in-silico docking studies were conducted on RT enzyme to investigate binding site interactions of synthesized compounds. The MMGBSA method was also used to calculate the binding free energy between the inhibitors and RT enzyme. The MD simulation was further performed for the apo form of the RT enzyme and docked complex of compound A6-RT enzyme to better understand the stability of the protein-ligand complex. The bioactivity analysis revealed that most of the synthesized compounds showed significant inhibitory activity against RT enzyme and the IC50 value was found to be in the range of 1.76-3.88 μM. The computational studies suggest that the docked compounds form the H-bonding with amino acid residue Lys101 and hydrophobic interactions with amino acid residues Tyr188, Tyr181, Trp229, and Tyr318, which act as the primary driving forces for protein-ligand interaction. The reported imidazol-5-one analogs can act as lead for further development of prospective RT inhibitors.

Synthesis and Formulation of Powerful ZnO Q-Dots/CNTs@Fe3O4 Nanopackage as a Predominant Anti-HIV-1 Infection

Usage of fine and uniform Fe3O4 nanoparticles (NPs) including super-paramagnetic unique properties developed state of the nanobio-formulations in recent years. We have shown a new formulated nanocomposition of super-paramagnetic iron oxide (Fe3O4) NPs (as substrate) with carbon nanotubes (CNTs) (as activator). Besides, ZnO@CNTs was synthesized as a magic assistant/hybrid for ZnO quantum dots nanoparticles (Q-Dots NPs) in this nanopackage. This novel formulated water-based nanofluid product consists of strong stabilizer, suitable dispersant-wetting agent complex and desirable water in oil emulsifier (w/o) package to damage HIV infection (AIDS) type 1. The achieved results demonstrated that smart nanofluid formulation had excellent functions as inhibitor, controller and treatment (Antiretroviral therapy (ART)) for HIV-1 integrase and could act as strong oxidizing agent. The nanofluid product was completely characterized with SEM morphology, TEM images, FTIR spectroscopy, XRD pattern, UV–Vis absorption spectroscopy, EDS and mapping of internal layers for one of the SEM surface morphology. Moreover, HIV-1 replication Assay, RT (reverse transcriptase) Assay, integrase assay, and cytotoxicity tests were performed and compared with Zidovudine (ZDV) and Raltegravir (RAL) as control antiretroviral medications. The specific interaction of this nanopackage with the target RNA and DNA proteins has been very interesting through main redox reactions.

A Small Molecule, ACAi-028, with Anti-HIV-1 Activity Targets a Novel Hydrophobic Pocket on HIV-1 Capsid.

The human immunodeficiency virus type 1 (HIV-1) capsid (CA) is an essential viral component of HIV-1 infection and an attractive therapeutic target for antivirals. Here, we report that a small molecule, ACAi-028, inhibits HIV-1 replication by targeting a hydrophobic pocket in the N-terminal domain of CA (CA-NTD). ACAi-028 is 1 of more than 40 candidate anti-HIV-1 compounds identified by in silico screening and 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assays. Our binding model showed that ACAi-028 interacts with the Q13, S16, and T19 amino acid residues, via hydrogen bonds, in the targeting pocket of CA-NTD. Using recombinant fusion methods, TZM-bl, time-of-addition, and colorimetric reverse transcriptase (RT) assays, the compound was found to exert anti-HIV-1 activity in the early stage between reverse transcription and proviral DNA integration, without any effect on RT activity in vitro, suggesting that this compound may affect HIV-1 core disassembly (uncoating) as well as a CA inhibitor, PF74. Moreover, electrospray ionization mass spectrometry (ESI-MS) also showed that the compound binds directly and noncovalently to the CA monomer. CA multimerization and thermal stability assays showed that ACAi-028 decreased CA multimerization and thermal stability via S16 or T19 residues. These results indicate that ACAi-028 is a new CA inhibitor by binding to the novel hydrophobic pocket in CA-NTD. This study demonstrates that a compound, ACAi-028, targeting the hydrophobic pocket should be a promising anti-HIV-1 inhibitor.

Exploring the anti-HIV-1 reverse transcriptase, anti-inflammatory, anti-cancer activities and cytotoxicity of two fermented commercial herbal concoctions sold in Limpopo Province of South Africa

Background and objectivesThe use of herbal concoctions is very popular in South Africa, including Limpopo Province. The herbal concoctions are claimed to be capable of treating numerous illnesses such as ulcers, cancer, HIV/AIDS, diabetes, certain STDs, blood cleansing to mention but a few. The focus of this study was to evaluate the anti-HIV 1 reverse transcriptase, anti-inflammatory and anti-cancerous activities as well as cytotoxic effects of 2 fermented herbal concoctions used for the treatment of the related ailments in Limpopo province of South Africa.MethodTwo fermented herbal concoctions obtained from a herbalist in Polokwane were extracted with 80% acetone. The anti-HIV activity of the herbal concoctions was determined using the anti-HIV reverse transcriptase assay. The anti-cancer and cytotoxic effects of the herbal concoctions were evaluated using cancerous Human Colon (HT-29) cells and the normal human Hepatoma cells (C3A) respectively.ResultsNotable anti-HIV reverse transcriptase activity was observed from the 80% acetone fraction of herbal concoction 1 (IC50 38.031 μg/mL) which exhibited better activity than the positive control Lamivudine (IC50 40.90 μg/mL). There was variation in the anti-inflammation activity as determined by the sPL2, 15-LOX and COX enzyme assays. The only concerning matter was the high COX-1 activity in some of the extracts, which is not desirable due to the mucosal protection action of COX-1 enzyme. The herbal concoctions did not exhibit cytotoxic effects on normal human cells, however, toxicity against cancerous cells was observed.ConclusionThe herbal concoctions displayed some considerable pharmacological effects against various ailments as claimed by the herbalist. More work to ascertain the toxicity of both concoctions against cancerous cells need to be followed as this could lead to the discovery of anticancer drugs.

In vitro Characterization of Efficacy and Toxicity of Nevirapine Analogs as Substitutes in HIV Treatment

Nevirapine (NVP), a non-nucleoside HIV reverse transcriptase (RT) inhibitor, is generally a well-tolerated drug. However, certain toxicological issues have been reported, including idiosyncratic drug reactions (IDRs) such as skin rash and hepatotoxicity. Additionally, NVP is a known mechanism-based inactivator (MBI) and inducer of CYP3A cytochrome P450 enzymes (CYPs), with the potential to cause drug-drug interactions. It has been demonstrated previously that the 12-hydroxynevirapine metabolite and a reactive quinone methide species, produced by CYP3A4 and CYP2B6, are responsible for the observed IDRs. The reactive quinone methide species also leads to mechanism-based inactivation of CYP3A4, while NVP itself is an inducer of both CYP3A4 and CYP2B6. The goal of our study was to characterize a series of NVP analogs with respect to their safety and efficacy to treat HIV by examining target engagement efficiency and metabolic liability through in vitro characterization. Our hypothesis was that a NVP analog will be able to inhibit RT with similar efficacy, but with limited production of the toxic metabolites. Initial studies were conducted to determine the IC50 values of NVP and each analog in the RT inhibition assay, followed by determining the CYP induction/inhibition potential of NVP and its associated analogs in cryopreserved primary human hepatocytes. mRNA fold induction, CYP3A4 activity fold change, and % lactate dehydrogenase (LDH) release were all studied via qPCR, LC-MS/MS, and LDH assays respectively. In total, NVP and eight analogs were tested. The RT assay IC50 of NVP was 0.5 uM and the three analogs with the lowest IC50 values were: nevirapine-d3 (NVP-d3, 0.8 uM), 2-nitro nevirapine (2-N-NVP, 1.1 uM), and 3-bromo nevirapine (3-B-NVP, 3.0 uM). The induction experiments demonstrated that CYP3A4 was induced ~2 fold at 25 uM NVP, and ~6 fold at 100 uM NVP. CYP2B6 showed higher induction, with ~5 fold at 25 uM NVP and ~13 fold at 100 uM NVP. For CYP3A4 activity, 25 uM NVP showed ~1.4 fold increase in activity, while 100 uM NVP resulted in no fold change. This is likely due to the combined induction/inhibition effect of NVP; i.e., at higher concentrations more NVP is present to inactivate CYP3A4 and thus inhibition wins out over induction, while at lower concentrations of NVP induction dominates. %LDH release along with observation of the monolayer revealed low levels of hepatocyte mortality. Overall, three analogs were identified as potential candidates to replace NVP, due to their low IC50 values in the RT inhibition assay and reduced potential for CYP induction. Further characterization of these analogs is ongoing with the goal to identify an efficacious and safer NVP analog that can be used to treat HIV in pregnant women and children in developing countries, where NVP is still often used.

Plasmacytoid dendritic cells have divergent effects on HIV infection of initial target cells and induce a pro-retention phenotype.

Although HIV infection inhibits interferon responses in its target cells in vitro, interferon signatures can be detected in vivo soon after sexual transmission, mainly attributed to plasmacytoid dendritic cells (pDCs). In this study, we examined the physiological contributions of pDCs to early HIV acquisition using coculture models of pDCs with myeloid DCs, macrophages and the resting central, transitional and effector memory CD4 T cell subsets. pDCs impacted infection in a cell-specific manner. In myeloid cells, HIV infection was decreased via antiviral effects, cell maturation and downregulation of CCR5 expression. In contrast, in resting memory CD4 T cells, pDCs induced a subset-specific increase in intracellular HIV p24 protein expression without any activation or increase in CCR5 expression, as measured by flow cytometry. This increase was due to reactivation rather than enhanced viral spread, as blocking HIV entry via CCR5 did not alter the increased intracellular p24 expression. Furthermore, the load and proportion of cells expressing HIV DNA were restricted in the presence of pDCs while reverse transcriptase and p24 ELISA assays showed no increase in particle associated reverse transcriptase or extracellular p24 production. In addition, pDCs also markedly induced the expression of CD69 on infected CD4 T cells and other markers of CD4 T cell tissue retention. These phenotypic changes showed marked parallels with resident memory CD4 T cells isolated from anogenital tissue using enzymatic digestion. Production of IFNα by pDCs was the main driving factor for all these results. Thus, pDCs may reduce HIV spread during initial mucosal acquisition by inhibiting replication in myeloid cells while reactivating latent virus in resting memory CD4 T cells and retaining them for immune clearance.

Bioactive tetrahydrofuran lignans from roots, stems, leaves and twigs of Anogeissus rivularis

Four previously undescribed tetrahydrofuran lignans, named anorisols A−D (1–4) and fourteen known compounds (5–18) were isolated from the roots, stems, leaves and twigs of Anogeissus rivularis. The chemical structures were elucidated on the basis of their spectroscopic data and by comparison with the literature data. The absolute configurations of 1–4 were established by comparison of the experimental ECD spectra with the calculated ECD spectra. Some isolated compounds were evaluated for their cytotoxic activity as well as anti-HIV-1 activity employing reverse transcriptase (RT) and syncytium reduction assays using the ΔTat/RevMC99 virus in 1A2 cell line systems. Compound 6 displayed the most potent activity in syncytium inhibition assay with effective concentration at 50% (EC50) value of 13.3 μM (SI >3.0). In the reverse transcriptase assay, compound 1 exhibited moderate activity with IC50 value of 213.9 μM.

Neuroinvasive chikungunya in a liver transplant recipient

The influence of chronic immunosuppression on the course of chikungunya virus (CHIKV) infection in recipients of solid organ transplantation (SOT) is still unsettled. Scarce data suggest that the course of CHIKV infection is generally benign in this population. In addition, the occurrence of severe atypical manifestations associated with CHIKV has not been well documented among SOT recipients. In this report, we describe a 64-year-old male liver transplant recipient who was admitted with fever, headache, arthralgia, left palpebral ptosis, mydriasis, and right hemiparesis. Cranial magnetic resonance imaging did not reveal any alteration suggestive of acute infection. Nevertheless, CHIKV was detected in the cerebrospinal fluid (CSF) with a real-time reverse transcriptase assay. Other PCR assays carried out in CSF were negative for HSV-1 and 2, cytomegalovirus, dengue virus (DENV), and Zika virus (ZIKV). CHIKV viremia was also detected while PCR assays for ZIKV and DENV in the blood were negative. ZIKV viruria was simultaneously present in this case. All neurologic manifestations waned within 2weeks after the onset. This report shows that chikungunya must be considered in the differential diagnosis of acute neurologic disease in SOT recipients who live in or have recently traveled to endemic areas.

Establishment of fast-growing serum-free immortalised cells from Chinese hamster lung tissues for biopharmaceutical production

Chinese hamster (Cricetulus griseus) ovary-derived Chinese hamster ovary (CHO) cells are the most commonly used mammalian hosts for the industrial production of recombinant therapeutics because of their ability to fold, assemble, and perform post-translational modifications, such as glycosylation, on proteins. They are also valuable for their ability to grow in serum-free suspension cultures. In this study, we established a cell line derived from lung tissue of Chinese hamsters, named Chinese hamster lung (CHL)-YN cells. The biosafety of CHL-YN cells was confirmed by in vitro sterility testing, mycoplasma detection, and reverse transcriptase assays. One of the key characteristics of CHL-YN cells was their doubling time of 8.1 h in chemically defined culture medium; thus, they proliferate much faster than conventional CHO cells and general mammalian cells. Transgenes could be introduced into CHL-YN cells with high efficiency. Finally, between 50% to > 100% of the amount of glycosylated immunoglobulin G (IgG)1 produced by CHO-K1 cells was produced by CHL-YN cells over a shorter period of time. In summary, fast-growing CHL-YN cells are a unique cell line for producing recombinant proteins.

Super-rapid quantitation of the production of HIV-1 harboring a luminescent peptide tag

In studies of HIV-1, virus production is normally monitored by either a reverse transcriptase assay or a p24 antigen capture ELISA. However, these assays are costly and time-consuming for routine handling of a large number of HIV-1 samples. For example, sample dilution is always required in the ELISA procedure to determine p24 protein levels because of the very narrow range of detectable concentrations in this assay. Here, we establish a novel HIV-1 production assay system to solve the aforementioned problems by using a recently developed small peptide tag called HiBiT. This peptide is a fragment of NanoLuc luciferase and generates a strong luminescent signal when complemented with the remaining subunit. To employ this technology, we constructed a novel full-length proviral HIV-1 DNA clone and a lentiviral packaging vector in which the HiBiT tag was added to the C terminus of the integrase. Tagging the integrase with the HiBiT sequence did not impede the resultant virus production, infectivity, or susceptibility to an integrase inhibitor. EM revealed normal morphology of the virus particles. Most importantly, by comparing between ELISA and the HiBiT luciferase assay, we successfully obtained an excellent linear correlation between p24 concentrations and HiBiT-based luciferase activity. Overall, we conclude that HiBiT-tagged viruses can replace the parental HIV-1 and lentiviral vectors, which enables us to perform a super-rapid, inexpensive, convenient, simple, and highly accurate quantitative assay for HIV-1/lentivirus production. This system can be widely applied to a variety of virological studies, along with screening for candidates of future antiviral drugs.

Magnesium Functions as Superior Co-factor for Measuring Reverse Transcriptase Activity of HIV-1, HIV-2, and SIV

This study compared different detection methods of human/simian immunodeficiency virus (HIV/SIV) infections in the cell line systems; notably, i) Indirect immunofluorescence assay (IFA), ii) integrated proviral DNA detection, iii) detection of syncytia, iv) measurement of reverse transcriptase (RT) activity. RTs of various retroviruses require cations, including Mg2+, Mn2+, Ni2+, and Cu2+, for their enzyme-activities. The study further compared the roles of Mg2+ and Mn2+ as cofactors for RT activities of freshly harvested HIV-1, HIV-2, and SIV. The NP-2/CD4/coreceptor cells were seeded for overnight and infected with viral inoculums at a multiplicity of infection (MOI) 1.0. The cells were passaged regularly in a 2-3 days interval and maintained up to 2 weeks. Infected cells were detected by indirect immunofluorescence assay (IFA). Multinucleated giant cells (MGC) in syncytia were quantified by Giemsa-staining. Proviral DNA was detected by PCR, and reverse transcriptase (RT) activity was measured. Two different cations, Mg2+ and Mn2+ were used as cofactors for RT assay. We found all the strains of HIV-1, HV-2 and SIV to infection in the cell line conveniently. IFA had identified all the viral infections in the infected cells. Proviral DNA detection, syncytia formation was observed in the infected cells. We found a better performance of Mg2+ as cofactor over Mn2+ in RT assay for HIV-1, HIV-2, SIV. Different four detection techniques of HIV/SIV infections show high level of agreement in the NP-2-based cell line system. Mg2+ remains a better cofactor for RT.

Rapid Lentiviral Vector Producer Cell Line Generation Using a Single DNA Construct

Stable suspension producer cell lines for the production of vesicular stomatitis virus envelope glycoprotein (VSVg)-pseudotyped lentiviral vectors represent an attractive alternative to current widely used production methods based on transient transfection of adherent 293T cells with multiple plasmids. We report here a method to rapidly generate such producer cell lines from 293T cells by stable transfection of a single DNA construct encoding all lentiviral vector components. The resulting suspension cell lines yield titers as high as can be achieved with transient transfection, can be readily scaled up in single-use stirred-tank bioreactors, and are genetically and functionally stable in extended cell culture. By removing the requirement for efficient transient transfection during upstream processing of lentiviral vectors and switching to an inherently scalable suspension cell culture format, we believe that this approach will result in significantly higher batch yields than are possible with current manufacturing processes and enable better patient access to medicines based on lentiviral vectors.

Anti-HIV/SIV activity of icariin and its metabolite anhydroicaritin mainly involve reverse transcriptase

AIDS, a serious fatal disease caused by the human immunodeficiency virus (HIV), is an epidemic disease for which no effective vaccine has been established. The current therapeutic interventions for AIDS have limited efficacy because they are unable to clear HIV infections and the continuous occurrence of resistant HIV strains. Therefore, the exploitation of new drugs to prevent the spread of AIDS remains a high priority. In this study, the effects of icariin and its metabolite anhydroicaritin on SIV/HIV replication were investigated. In CEM × 174 cells and PBMC cells, both icariin and anhydroicaritin can significantly inhibit HIV-1 or SIVmac251 replication. Furthermore, molecular docking studies revealed that icariin and anhydroicaritin can act on both HIV reverse transcriptase and protease but could not bind to integrase. Reverse transcriptase and protease inhibition biological assays showed that both icariin and anhydroicaritin could significantly inhibit only HIV reverse transcriptase. In summary, the two compounds can significantly inhibit HIV/SIV in vitro and their targets may be mainly involved with HIV reverse transcriptase.

Non-nuke HIV-1 inhibitor shuttled by mesoporous silica nanoparticles effectively slows down HIV-1 replication in infected human cells

The objectives of this study were to reduce the cytotoxic effect of nevirapine (NVP) and to enhance its anti-HIV efficacy through mesoporous silica nanoparticles (MSNPs) mediated delivery. MSNPs were synthesized and characterized by various techniques. Confocal microscopy and flow cytometry results exhibited efficient uptake of FITC-conjugated MSNPs in TZM-bl cells. The NVP was loaded within MSNPs, and its anti-HIV1 efficacy was assessed on HIV1 (R5 and X4 variants) infected TZM-bl cells and further confirmed on peripheral blood mononuclear cells (PBMCs). The in vitro assessment of the anti-HIV1 potential of NVP and NVP-MSNPs in HIV1 infected TZM-bl cells and PBMCs showed increased efficacy of NVP upon loading within MSNPs with significant increase in therapeutic index. The increased efficacy against HIV1 was accompanied by reduced cytotoxicity to TZM-bl cells and PBMCs. Further, reverse transcriptase (RT) assay confirmed the inhibitory effect on RTase, which is a key enzyme in HIV-1 replication. The present study showed that entrapment of NVP within MSNPs led to an increased efficacy with reduced cytotoxic effect resulting in the enhanced therapeutic index (TI).