Optimal suppression of HIV replication by low-dose hydroxyurea through the combination of antiviral and cytostatic ('virostatic') mechanisms

mTOR Overcomes Multiple Metabolic Restrictions to Enable HIV-1 Reverse Transcription and Intracellular Transport

Cellular metabolism governs the susceptibility of CD4 T cells to HIV-1 infection. Multiple early post-fusion steps of HIV-1 replication are restricted in resting peripheral blood CD4 T cells; however, molecular mechanisms that underlie metabolic control of these steps remain undefined. Here, we show that mTOR activity following T cell stimulatory signals overcomes metabolic restrictions in these cells by enabling the expansion of dNTPs to fuel HIV-1 reverse transcription (RT), as well as increasing acetyl-CoA to stabilize microtubules that transport RT products. We find that catalytic mTOR inhibition diminishes the expansion of pools of both of these metabolites by limiting glucose and glutamine utilization in several pathways, thereby suppressing HIV-1 infection. We demonstrate how mTOR-coordinated biosyntheses enable the early steps of HIV-1 replication, add metabolic mechanisms by which mTOR inhibitors block HIV-1, and identify some metabolic modules downstream of mTOR as druggable targets for HIV-1 inhibition.

Barriers to HIV Cure

Since the beginning of the epidemic, more than 70 million people have been infected with human immunodeficiency virus (HIV) and about 38 million have died from acquired immune deficiency syndrome (AIDS)-related illnesses. While the discovery of highly active antiretroviral therapy (HAART) in the mid 90's has saved millions of lives, a complete eradication of HIV is still not possible as HIV can persist for decades in a small reservoir of latently infected cells. Once reactivated, these latently infected cells can actively produce viral particles. Recent studies suggest that several sanctuaries exist within infected individuals where HIV can remain undetected by the immune system. These cellular, anatomical and microanatomical viral reservoirs represent a major obstacle for the eradication of HIV. Here we review recent findings on potential sanctuaries of HIV and address potential avenues to overcome these immunological barriers.

Immune Recovery following Antineoplastic Chemotherapy and Highly Active Antiretroviral Therapy (Haart) in a Child with HIV-1 Infection Previously Unresponsive to Haart

We report the case of a perinatally HIV-1-infected child, previously immunologically unresponsive to antiretroviral treatments (including the highly active antiretroviral therapy), who instead developed a vigorous and long-lasting immune response after the highly active antiretroviral therapy was associated with antineoplastic chemotherapy undertaken for a B-cell non-Hodgkin bone lymphoma.

Gold(I) complex of 1,1'-bis(diphenylphosphino) ferrocene-quinoline conjugate: a virostatic agent against HIV-1

HIV infection is known for replicating in proliferating CD(+) T-cells. Treatment of these cells with cytostatic (anti-proliferation) compounds such as hydroxyurea interferes with the cells's ability support HIV replication. Combinations of such cytostatic compounds with proven anti-retroviral drugs (like ddI) are known as virostatic, and have been shown to aid in the control of the infection. The use of two different drugs in virostatic combinations however, carries the risk of adverse effects including drug-drug interactions, which could lead to augmented toxicities and reduced efficacy. Here, a novel digold(I) complex of ferrocene-quinoline (3) was investigated for cytostatic behaviour as well as anti-viral activity which if demonstrated would eliminate concerns of drug-drug interactions. The complex was synthesized and characterized by NMR, FT-IR and mass spectroscopy and the molecular structure was confirmed by X-ray crystallography. Bio-screening involved viability dyes, real time electronic sensing and whole virus assays. The complex showed significant (p = 0.0092) inhibition of virus infectivity (83 %) at 10 ug/mL. This same concentration caused cytostatic behaviour in TZM-bl cells with significant (p < 0.01) S and G2/M phase cell cycle arrest. These data supports 3 as a virostatic agent, possessing both anti-viral and cytostatic characteristics. In the absence of 3, TZM-bl cells were infected by a pseudovirus and this was demonstrated through luminescence in a luciferase assay. Pre-incubation of the virus with 3 decreased luminescence, indicating the anti-viral activity of 3. Complex 3 also showed cytostatic behavior with increased S-phase and G2/M phase cell cycle arrest.

In vitro reactivation of latent HIV-1 by cytostatic bis(thiosemicarbazonate) gold(III) complexes

Background

A number of cytostatic agents have been investigated for the ability to reactivate latent viral reservoirs, which is a major prerequisite for the eradication of HIV-1 infection. Two cytostatic bis(thiosemicarbazonate) gold(III) complexes (designated 1 and 2) were tested for this potential in the U1 latency model of HIV-1 infection.

Methods

Cell viability in the presence or absence of 1 and 2 was determined using a tetrazolium dye and evidence of reactivation was assessed by p24 antigen capture following exposure to a latency stimulant, phorbol myristate acetate (PMA) and or test compounds. The latency reactivation mechanism was explored by determining the effect of the complexes on protein kinase C (PKC), histone deacetylases (HDAC) and proinflammatory cytokine production.

Results

The CC₅₀ of the complexes in U1 cells were 0.53 ± 0.12 μM for 1 and 1.0 ± 0.4 μM for 2. In the absence of PMA and at non toxic concentrations of 0.2 and 0.5 μM, 1 and 2 significantly (p ≤ 0.02) reactivated virus in U1 cells by 2.7 and 2.3 fold respectively. In comparison, a 2.6 fold increase (p = 0.03) in viral reactivation was observed for hydroxyurea (HU), which was used as a cytostatic and latent HIV reactivation control. Viral reactivation was absent for the complexes during co-stimulation with PMA indicating the lack of an additive effect between the chemicals as well as an absence of inhibition of PMA induced HIV reactivation but for HU inhibition of the stimulant’s activity was observed (p = 0.01). Complex 1 and 2 activated PKC activity by up to 32% (p < 0.05) but no significant inhibition of HDAC was observed. Increases in TNF-α levels suggested that the reactivation of virus by the complexes may have been due to contributions from the latter and the activation of PKC.

Conclusion

The ethyl group structural difference between 1 and 2 seems to influence bioactivity with lower active concentrations of 1, suggesting that further structural modifications should improve specificity. The cytostatic effect of 1 and 2 and now HIV reactivation from a U1 latency model is consistent with that of the cytostatic agent, HU. These findings suggest that the complexes have a potential dual (cytostatic and reactivation) role in viral “activation/elimination”.

Electronic supplementary material

The online version of this article (doi:10.1186/s12879-014-0680-3) contains supplementary material, which is available to authorized users.

HIV cure research: advances and prospects

Thirty years after the identification of HIV, a cure for HIV infection is still to be achieved. Advances of combined antiretroviral therapy (cART) in recent years have transformed HIV infection into a chronic disease when treatment is available. However, in spite of the favorable outcomes provided by the newer therapies, cART is not curative and patients are at risk of developing HIV-associated disorders. Moreover, universal access to antiretroviral treatment is restricted by financial obstacles. This review discusses the most recent strategies that have been developed in the search for an HIV cure and to improve life quality of people living with HIV.

The effect of hydroxcarbamide therapy on survival of children with sickle cell disease

Although evidence is accumulating that hydroxycarbamide decreases mortality among adults with sickle cell disease (SCD), there are no published data regarding the effect of hydroxycarbamide on mortality among children. The Paediatric Hydroxycarbamide Program was established to treat children with SCD aged 3-18 years if they met disease severity criteria. Mortality data and clinical/laboratorial effects of hydroxycarbamide were retrospectively collected for the first 9 years of the Program. Mortality among those who received hydroxycarbamide was compared to that of untreated children. Among 1760 subjects, 267 received hydroxycarbamide at a median dose of 20·8 mg/kg/d (range 10-32) for a median of 2 years (range 0·1-6·5). Survival among hydroxycarbamide-treated children was significantly greater than that among untreated ones (99·5% vs. 94·5%, P = 0·01), due primarily to fewer deaths from acute chest syndrome and infection. Hydroxycarbamide therapy was significantly associated with increases in haemoglobin concentration, fetal haemoglobin, mean corpuscular volume, and reduction in platelet counts, reticulocytes and neutrophils. Toxicity was minimal and predominantly mild reversible neutropenia. Significantly fewer hospitalizations and emergency room visits, and shorter admissions were observed among hydroxycarbamide-treated subjects, when compared to the 12-month period prior to treatment initiation. Hydroxycarbamide therapy reduces disease severity and is probably associated with decreased mortality among children with SCD.

VS411 reduced immune activation and HIV-1 RNA levels in 28 days: randomized proof-of-concept study for antiviral-hyperactivation limiting therapeutics

Background

A new class of antiretrovirals, AntiViral-HyperActivation Limiting Therapeutics (AV-HALTs), has been proposed as a disease-modifying therapy to both reduce Human Immunodeficiency Virus Type 1 (HIV-1) RNA levels and the excessive immune activation now recognized as the major driver of not only the continual loss of CD4⁺ T cells and progression to Acquired Immunodeficiency Syndrome (AIDS), but also of the emergence of both AIDS-defining and non-AIDS events that negatively impact upon morbidity and mortality despite successful (ie, fully suppressive) therapy. VS411, the first-in-class AV-HALT, combined low-dose, slow-release didanosine with low-dose hydroxycarbamide to accomplish both objectives with a favorable toxicity profile during short-term administration. Five dose combinations were administered as VS411 to test the AV-HALT Proof-of-Concept in HIV-1-infected subjects.

Methods

Multinational, double-blind, 28-day Phase 2a dose-ranging Proof-of-Concept study of antiviral activity, immunological parameters, safety, and genotypic resistance in 58 evaluable antiretroviral-naïve HIV-1-infected adults. Randomization and allocation to study arms were carried out by a central computer system. Results were analyzed by ANOVA, Kruskal-Wallis, ANCOVA, and two-tailed paired t tests.

Results

VS411 was well-tolerated, produced significant reductions of HIV-1 RNA levels, increased CD4⁺ T cell counts, and led to significant, rapid, unprecedented reductions of immune activation markers after 28 days despite incomplete viral suppression and without inhibiting HIV-1-specific immune responses. The didanosine 200 mg/HC 900 mg once-daily formulation demonstrated the greatest antiviral efficacy (HIV-1 RNA: −1.47 log₁₀ copies/mL; CD4⁺ T cell count: +135 cells/mm³) and fewest adverse events.

Conclusions

VS411 successfully established the Proof-of-Concept that AV-HALTs can combine antiviral efficacy with rapid, potentially beneficial reductions in the excessive immune system activation associated with HIV-1 disease. Rapid reductions in markers of immune system hyperactivation and cellular proliferation were obtained despite the fact that VS411 did not attain maximal suppression of HIV RNA, suggesting this effect was due to the HALT component.

Trial Registration

ITEudraCT 2007-002460-98

Immunotherapeutic restoration in HIV-infected individuals

While the development of combined active antiretroviral therapy (cART) has dramatically improved life expectancies and quality of life in HIV-infected individuals, long-term clinical problems, such as metabolic complications, remain important constraints of life-long cART. Complete immune restoration using only cART is normally unattainable even in cases of sufficient plasma viral suppression. The need for immunologic adjuncts that complement cART remains, because while cART alone may result in the complete recovery of peripheral net CD4+ T lymphocytes, it may not affect the reservoir of HIV-infected cells. Here, we review current immunotherapies for HIV infection, with a particular emphasis on recent advances in cytokine therapies, therapeutic immunization, monoclonal antibodies, immune-modulating drugs, nanotechnology-based approaches and radioimmunotherapy.

New bis(thiosemicarbazonate) gold(III) complexes inhibit HIV replication at cytostatic concentrations: potential for incorporation into virostatic cocktails

Four bis(thiosemicarbazonate)gold(III) complexes (1-4) with a general formula [Au(L)]Cl {L=L1, glyoxal-bis(N(4)-methylthiosemicarbazone); L2, glyoxal-bis(N(4)-ethylthiosemicarbazone); L3, diacetyl-bis(N(4)-methylthiosemicarbazone); L4, diacetyl-bis(N(4)-ethylthiosemicarbazone)} were synthesised and screened for activity against the human immunodeficiency virus (HIV). Complexes 1-4 were characterised using (1)H-NMR and IR spectroscopy; and their purity established by micronanalysis. Complex 3 inhibited viral infection of TZM-bl cells by 98% (IC(50)=6.8±0.6μM) at a non toxic concentration of 12.5μM while complex 4 inhibited infection of these cells by 72 and 98% (IC(50)=5.3±0.4μM) at concentrations of 6.25 and 12.5μM respectively. The mechanism of inhibition of infection in TZM-bl cells is presumably as a result of the cytostatic or anti-proliferative activity that was observed for complex 4 in real time cell electronic sensing (RT-CES) and carboxyflourescein succinimidyl ester (CFSE) analysis. Treatment of T lymphocytes from HIV infected individuals with 4 decreased CD4+ T cell expression (p=0.0049) as demonstrated by multi-parametric flow cytometry without suppressing cytokine production. None of the ligands (L1-L4) demonstrated anti-viral activity, supporting the importance of metal (gold) complexation in these potential drugs. Complexes 3 and 4 were shown to have ideal lipophilicity values that were similar when shake flask (0.97±0.5 and 2.42±0.6) and in silico prediction (0.8 and 1.5) methods were compared. The activity and drug-like properties of complexes 3 and 4 suggests that these novel metal-based compounds could be combined with virus inhibitory drugs to work as cytostatic agents in the emerging class of anti-HIV drugs known as virostatics.

Strategies to improve efficacy and safety of a novel class of antiviral hyper-activation-limiting therapeutic agents: the VS411 model in [corrected] HIV/AIDS

BACKGROUND AND PURPOSE

Antiviral hyper-activation-limiting therapeutic agents (AV-HALTs) are a novel experimental drug class designed to both decrease viral replication and down-regulate excessive immune system activation for the treatment of chronic infections, including human immunodeficiency virus (HIV)/acquired immunodeficiency syndrome. VS411, a first-in-class AV-HALT, is a single-dosage form combining didanosine (ddI, 400 mg), an antiviral (AV), and hydroxyurea (HU, 600 mg), a cytostatic agent, designed to provide a slow release of ddI to reduce its maximal plasma concentration (C(max)) to potentially reduce toxicity while maintaining total daily exposure (AUC) and the AV activity.

EXPERIMENTAL APPROACH

This was a pilot phase I, open-label, randomized, single-dose, four-way crossover trial to investigate the fasted and non-fasted residual variance of AUC, C(max) and the oral bioavailability of ddI and HU, co-formulated as VS411, and administered as two different fixed-dose combination formulations compared to commercially available ddI (Videx EC) and HU (Hydrea) when given simultaneously.

KEY RESULTS

Formulation VS411-2 had a favourable safety profile, displayed a clear trend for lower ddI C(max) (P= 0.0603) compared to Videx EC, and the 90% confidence intervals around the least square means ratio of C(max) did not include 100%. ddI AUC(∞) was not significantly decreased compared to Videx EC. HU pharmacokinetic parameters were essentially identical to Hydrea, although there was a decrease in HU exposure under fed versus fasted conditions.

CONCLUSIONS AND IMPLICATIONS

A phase IIa trial utilizing VS411-2 formulation has been fielded to identify the optimal doses of HU plus ddI as an AV-HALT for the treatment of HIV disease.

Inhibition of allogeneic inflammatory responses by the Ribonucleotide Reductase Inhibitors, Didox and Trimidox

Background

Graft-versus-host disease is the single most important obstacle facing successful allogeneic stem cell transplantation (SCT). Even with current immunosuppressive therapies, morbidity and mortality rates are high. Current therapies including cyclosporine A (CyA) and related compounds target IL-2 signaling. However, although these compounds offer great benefit, they are also associated with multiple toxicities. Therefore, new compounds with a greater efficacy and reduced toxicity are needed to enable us to overcome this hurdle.

Methods

The allogeneic mixed lymphocyte reaction (MLR) is a unique ex vivo method to study a drug's action on the initial events resulting in T-cell activation and proliferation, synonymous to the initial stages of tissue and organ destruction by T-cell responses in organ rejection and Graft-versus-host disease. Using this approach, we examined the effectiveness of two ribonucleotide reductase inhibitors (RRI), Didox and Trimidox, to inhibit T-cell activation and proliferation.

Results

The compounds caused a marked reduction in the proliferative responses of T-cells, which is also accompanied by decreased secretion of cytokines IL-6, IFN-γ, TNF-α, IL-2, IL-13, IL-10 and IL-4.

Conclusions

In conclusion, these data provide critical information to justify further investigation into the potential use of these compounds post allogeneic bone marrow transplantation to alleviate graft-versus-host disease thereby achieving better outcomes.

Hydroxyurea for children with sickle cell disease

Hydroxyurea therapy offers promise for ameliorating the clinical course of children with sickle cell disease (SCD). Hydroxyurea is a prototypic therapeutic option; it can be administered with minimal side effects, has a relatively wide therapeutic window, and has mechanisms of action that address pathophysiologic pathways of sickling, vaso-occlusion, hemolysis, and organ damage. There are limited data regarding hydroxyurea's ability to prevent or diminish organ dysfunction, and the long-term risks of hydroxyurea therapy remain incompletely defined. Although clinical trials are underway to address long-term issues, hydroxyurea remains an effective but underutilized therapy for SCD.

Cyanide, peroxide and nitric oxide formation in solutions of hydroxyurea causes cellular toxicity and may contribute to its therapeutic potency

Hydroxyurea (HU) is a potent remedy against a variety of ailments and an efficient inhibitor of DNA synthesis, yet its pharmacology is unclear. HU acts in Escherichia coli by the same mechanism as it does in eukaryotes, via inhibition of ribonucleotide reductase. When examining a controversy about concentrations of HU that prevent thymineless death in E. coli, we found instability in HU solutions that avoided prior detection due to its peculiar nature. In contrast to freshly dissolved HU, which did not affect respiration and was bacteriostatic, 1-day-old HU solutions inhibited respiration and were immediately bactericidal. Respiration was inhibited by two gases, hydrogen cyanide (HCN) and nitric oxide (NO), whose appearance we detected in "aged" HU stocks by gas chromatography-mass spectrometry; however, neither gas was bactericidal. While determining the cause of toxicity, we found that HU damages DNA directly. We also demonstrated accumulation of peroxides in HU solutions by enzymatic assays, which explains the toxicity, as both NO and HCN are known to kill bacteria when combined with hydrogen peroxide. Remarkably, we found that bactericidal effects of NO+H(2)O(2) and HCN+H(2)O(2) mixtures were further synergistic. Accumulation of decomposition products in solutions of HU may explain the broad therapeutic effects of this drug.

Hydroxyurea for children with sickle cell disease

Hydroxyurea therapy offers promise for ameliorating the clinical course of children with sickle cell disease (SCD). Hydroxyurea is a prototypic therapeutic option; it can be administered with minimal side effects, has a relatively wide therapeutic window, and has mechanisms of action that address pathophysiologic pathways of sickling, vaso-occlusion, hemolysis, and organ damage. There are limited data regarding hydroxyurea's ability to prevent or diminish organ dysfunction, and the long-term risks of hydroxyurea therapy remain incompletely defined. Although clinical trials are underway to address long-term issues, hydroxyurea remains an effective but underutilized therapy for SCD.

Effects of immunosuppressive drugs on HIV infection: implications for solid-organ transplantation

With the advent of highly active antiretroviral therapy (HAART), HIV infection has become a chronic disease. Various end-stage organ failures have now become common co-morbidities and are primary causes of mortality in HIV-infected patients. Solid-organ transplantation therefore has been proposed to these patients, as HIV infection is not anymore considered an absolute contraindication. The initial results of organ transplantation in HIV-infected patients are encouraging with no differences in patient and graft survival compared with non-HIV-infected patients. The use of immunosuppressive drug therapy in HIV-infected patients has so far not shown major detrimental effects, and some drugs in combination with HAART have even demonstrated possible beneficial effects for specific HIV settings. Nevertheless, organ transplantation in HIV-infected patients remains a complex intervention, and more studies will be required to clarify open questions such as long-term effects of drug interactions between antiretroviral and immunosuppressive drugs, outcome of recurrent HCV infection in HIV-infected patients, incidence of graft rejection, or long-term graft and patient survival. In this article, we first review the immunological pathogenesis of HIV infection and the rationale for using immunosuppression combined with HAART. We then discuss the most recent results of solid-organ transplantation in HIV-infected patients.

Hydroxyurea exerts an anti-proliferative effect on T cells but has no direct impact on cellular activation

Hydroxyurea (HU) is a cytostatic drug which has been used as an anti-HIV agent due mainly to its synergistic activity when combined with certain anti-retrovirals. In addition, HU might have a beneficial effect on parameters involved in the pathogenesis of HIV infection, such as immune activation. To test this hypothesis, the effect of HU on T cell proliferation and T cell activation, as well as the potential association between these two phenomena, were examined in an in vitro model. HU exerted a dose-dependent anti-proliferative effect on T cells, and modulated the expression of different activation markers. In cells exposed to HU, expression of CD25 and CD38 diminished in a dose-dependent manner, whereas expression of CD69 increased. However, when the expression of these markers was examined separately on proliferating and non-proliferating lymphocytes, HU did not exert any significant effect. Thus, the effect of HU on T cell activation is not direct and seems to be mediated through its effect on T cell proliferation.