Raymond Hewer

Natural Polymorphisms of integrase Among HIV Type 1-Infected South African Patients

An HIV-1 subtype C specific assay was established for integrase genotyping from 51 integrase inhibitor-naive patient plasma samples and 22 antiretroviral drug-naive primary viral isolates from South Africa. Seventy-one of the 73 samples were classified as HIV-1 subtype C and two samples were unique AC and CG recombinants in integrase. Amino acid sequence analysis revealed there were no primary mutations (Y143R/C/H, Q148H/R/K, and N155H/S) associated with reduced susceptibility to the integrase inhibitors raltegravir and elvitegravir. However, one sample had the T97A mutation, three samples had the E157Q and V165I mutations, and the majority of samples contained the polymorphic mutation V72I. The expected finding of no major integrase mutations conferring resistance to integrase inhibitors suggests that this new antiretroviral drug class will be effective in our region where HIV-1 subtype C predominates. However, the impact of E157Q and other naturally occurring polymorphisms warrants further phenotypic investigation.

Modification of HIV-1 reverse transcriptase and integrase activity by gold(III) complexes in direct biochemical assays.

Gold(I) and gold(III) complexes have been previously investigated for potential biomedical applications including as anti-HIV agents. The oxidising nature of some gold(III) complexes yields well-documented cellular toxicity in cell-based assays but the effect in direct biochemical assays has not been fully investigated. In this study, gold(III) complexes were evaluated in HIV-1 reverse transcriptase and HIV-1 integrase biochemical assays. The gold(III) tetrachlorides KAuCl(4) and HAuCl(4) yielded sub-micromolar IC(50)s of 0.947 and 0.983μM in the direct HIV-1 RT assay, respectively, while IC(50)s ranging from 0.461 to 8.796μM were obtained for seven selected gold(III) complexes. The gold(III) tetrachlorides were also effective inhibitors of integrase enzymatic activity with >80% inhibition obtained at a single dose evaluation of 10μM. RT inhibition was decreased in the presence of a reducing agent (10mM DTT) and against the M184V HIV-1 RT mutant, while none of the gold(III) complexes were effective inhibitors in cell-based antiviral assays (SI values <5.95). Taken together, the findings of this study demonstrate that gold(III) complexes modify HIV-1 enzyme activity in direct biochemical assays, most likely through protein oxidation.

Novel furocoumarins as potential HIV-1 integrase inhibitors.

A series of seven novel, rationally designed N-substituted 3-{3,5-dimethylfuro[3,2-g]coumarin-6-yl}propanamides have been prepared as potential HIV-1 integrase (IN) inhibitors via a five-step pathway commencing with resorcinol and diethyl 2-acetylglutarate, and the HIV-1 IN inhibition potential of these compounds has been examined relative to raltegravir, a known HIV-1 IN inhibitor.

Heteroditopic P,N ligands in gold(I) complexes: synthesis, structure and cytotoxicity.

New heteroditopic, bi- and multidentate imino- and aminophosphine ligands were synthesised and complexed to [AuCl(THT)] (THT=tetrahydrothiophene). X-ray crystallography confirmed Schiff base formation in three products, the successful reduction of the imino-group to the sp(3)-hybridised amine in several instances, and confirmed the formation of mono-gold(I) imino- and aminophosphine complexes for four Au-complexes. Cytotoxicity studies in cancerous and non-cancerous cell lines showed a marked increase in cytotoxicity upon ligand complexation to gold(I). These findings were supported by results from the 60-cell line fingerprint screen of the Developmental Therapeutics Programme of the National Institutes of Health for two promising compounds. The cytotoxicity of some of these ligands and gold(I)complexes is due to the induction of apoptosis. The ligands and gold(I)complexes demonstrated selective toxicity towards specific cell lines, with Jurkat T cells being more sensitive to the cytotoxic effects of these compounds, while the non-cancerous human cell line KMST6 proved more resistant when compared to the cancerous cell lines. Results from the NIH DTP 60 cell-line fingerprint screen support the observed enhancement of cytotoxicity upon gold(I) complexation. One gold(I)complex induced high levels of apoptosis at concentrations of 50 μM in all the cell lines screened in this study, while some of the other compounds selectively induced apoptosis in the cell lines. These results point towards the potential for selective toxicity to cancerous cells through the induction of apoptosis.

Design, Synthesis, and Biological Evaluation of 1,2-Dihydroisoquinolines as HIV-1 Integrase Inhibitors

6-Endo-dig-cyclization is an efficient method for the synthesis of 1,2-dihydroisoquinolines. We have synthesized few 1,2-dihydroisoquinolines having different functionality at the C-1, C-3, C-7, and N-2 positions for evaluation against HIV-1 integrase (HIV1-IN) inhibitory activity. A direct nitro-Mannich condensation of o-alkynylaldimines and dual activation of o-alkynyl aldehydes by inexpensive cobalt chloride yielded desired compounds. Out of 24 compounds, 4m and 6c came out as potent integrase inhibitors in in vitro strand transfer (ST) assay, with IC50 value of 0.7 and 0.8 μM, respectively. Molecular docking of these compounds in integrase revealed strong interaction between metal and ligands, which stabilizes the enzyme-inhibitor complex. The ten most active compounds were subjected to antiviral assay. Out of those, 6c reduced the level of p24 viral antigen by 91%, which is comparable to RAL in antiviral assay. Interestingly, these compounds showed similar ST inhibitory activity in G140S mutant, suggesting they can act against resistant strains.

Bioconjugates of Enantiomerically Pure Organopalladium Compounds by Metal‐Assisted Positional Selective Transesterifications at Palladium Enolates

The synthesis of enantiomerically pure palladatricyclo[4.1.0.0(2,4)]heptanes and their modification by an unprecedented and very efficient positional selective transesterification is described. The mild reaction conditions are most probably based on an acceleration of the transesterification due to assistance by the metal. This novel approach allows straightforward access to a large number of structurally diverse organometallic complexes. The functional groups on the newly installed ester moieties were modified by using standard peptide synthesis protocols, Sonogashira reactions, and nucleophilic substitution reactions. The cellular uptake of these organometallic species was traced by confocal microscopy and their biological activity was evaluated by using different cell lines. Inhibition of cell growth and induction of apoptotic cell death by these novel palladium heterocycles are equivalent to Cisplatin.

The evaluation of statins as potential inhibitors of the LEDGF/p75-HIV-1 integrase interaction.

Lovastatin was identified through virtual screening as a potential inhibitor of the LEDGF/p75–HIV‐1 integrase interaction. In an AlphaScreen assay, lovastatin inhibited the purified recombinant protein–protein interaction (IC50 = 1.97 ± 0.45 μm) more effectively than seven other tested statins. None of the eight statins, however, yielded antiviral activity in vitro, while only pravastatin lactone yielded detectable inhibition of HIV‐1 integrase strand transfer activity (31.65% at 100 μm). A correlation between lipophilicity and increased cellular toxicity of the statins was observed.

Functional roles of HIV-1 Vpu and CD74: Details and implications of the Vpu-CD74 interaction.

HIV-1 Vpu has a variety of functions, including CD4 degradation and the downregulation of MHCII. Downregulation of the MHCII occurs through Vpu binding to the cytoplasmic domain of CD74, the chaperone for antigen presentation. The CD74 cytoplasmic domain also plays a vital role in cell signaling through the activation of an NF-κB signal cascade for the maturation, proliferation and survival of B cells as well as by binding the macrophage inhibitory factor. In view of these functions, it follows that the Vpu-CD74 interaction has multiple downstream consequences for the immune system as it not only impairs foreign antigen presentation but may also have an effect on signal transduction cascades. It is thought that Vpu specifically targets intracellular CD74 while other HIV-1 proteins cannot. Therefore, this protein-protein interaction would be a potential drug target in order to reduce viral persistence. We review the functional importance and specific binding site of Vpu and CD74.

Random and Rational Approaches to HIV Drug Discovery in Africa

The development of therapeutic agents to inhibit human immunodeficiency virus (HIV) replication began soon after the isolation and identification of the virus as the causative agent of the acquired immune deficiency syndrome (AIDS). Within a short period of time thereafter, azidothymidine (AZT) was found to inhibit viral replication and became the first FDA-approved drug for the treatment of HIV/AIDS in 1987. Since then, continual and substantial progress has been made. To date, 35 drugs have been clinically approved, and with treatment, HIV infection has been transformed from a life-threatening disease with a short survival rate into a chronic manageable condition. Furthermore, several drugs are currently under investigation in various stages of clinical and preclinical development. Despite this remarkable success, there is continued global effort directed towards the design, discovery and development of novel inhibitors that may improve treatment strategies and overcome new challenges that have arisen. This chapter focuses on the discovery phase of the HIV drug discovery and development pipeline and describes the contribution and progress made by African scientists and research laboratories. Review of the period 1990 to present day reveals considerable African research describing anti-HIV inhibitors, derived from natural sources or through synthetic means, and identified through both rational and random drug discovery approaches. Several challenges facing HIV researchers on the continent disproportionately affected by HIV/AIDS are also described.

4-(3-Azaniumylpropyl)morpholin-4-ium chloride hydrogen oxalate: an unusual example of a dication with different counter-anions.

The mixed organic-inorganic title salt, C7H18N2O(2+)·C2HO4(-)·Cl(-), forms an assembly of ionic components which are stabilized through a series of hydrogen bonds and charge-assisted intermolecular interactions. The title assembly crystallizes in the monoclinic C2/c space group with Z = 8. The asymmetric unit consists of a 4-(3-azaniumylpropyl)morpholin-4-ium dication, a hydrogen oxalate counter-anion and an inorganic chloride counter-anion. The organic cations and anions are connected through a network of N-H···O, O-H···O and C-H···O hydrogen bonds, forming several intermolecular rings that can be described by the graph-set notations R3(3)(13), R2(1)(5), R1(2)(5), R2(1)(6), R2(3)(6), R2(2)(8) and R3(3)(9). The 4-(3-azaniumylpropyl)morpholin-4-ium dications are interconnected through N-H···O hydrogen bonds, forming C(9) chains that run diagonally along the ab face. Furthermore, the hydrogen oxalate anions are interconnected via O-H···O hydrogen bonds, forming head-to-tail C(5) chains along the crystallographic b axis. The two types of chains are linked through additional N-H···O and O-H···O hydrogen bonds, and the hydrogen oxalate chains are sandwiched by the 4-(3-azaniumylpropyl)morpholin-4-ium chains, forming organic layers that are separated by the chloride anions. Finally, the layered three-dimensional structure is stabilized via intermolecular N-H···Cl and C-H···Cl interactions.