Human Immunodeficiency Virus Replication Cycle Research Articles

Recent Progress in Synthesis, POM Analyses and SAR of Coumarin-Hybrids as Potential Anti-HIV Agents-A Mini Review.

The human immunodeficiency virus (HIV) is the primary cause of acquired immune deficiency syndrome (AIDS), one of the deadliest pandemic diseases. Various mechanisms and procedures have been pursued to synthesise several anti-HIV agents, but due to the severe side effects and multidrug resistance spawning from the treatment of HIV/AIDS using highly active retroviral therapy (HAART), it has become imperative to design and synthesise novel anti-HIV agents. Literature has shown that natural sources, particularly the plant kingdom, can release important metabolites that have several biological, mechanistic and structural representations similar to chemically synthesised compounds. Certainly, compounds from natural and ethnomedicinal sources have proven to be effective in the management of HIV/AIDS with low toxicity, fewer side effects and affordability. From plants, fungi and bacteria, coumarin can be obtained, which is a secondary metabolite and is well known for its actions in different stages of the HIV replication cycle: protease, integrase and reverse transcriptase (RT) inhibition, cell membrane fusion and viral host attachment. These, among other reasons, are why coumarin moieties will be the basis of a good building block for the development of potent anti-HIV agents. This review aims to outline the synthetic pathways, structure-activity relationship (SAR) and POM analyses of coumarin hybrids with anti-HIV activity, detailing articles published between 2000 and 2023.

The Human Immunodeficiency Virus Capsid Is More Than Just a Genome Package.

Human immunodeficiency virus (HIV) is one of the most studied of all human pathogens. One strain-HIV-1 group M-is responsible for a global pandemic that has infected >60 million people and killed >20 million. Understanding the stages of HIV infection has led to highly effective therapeutics in the form of antiviral drugs that target the viral enzymes reverse transcriptase, integrase, and protease as well as biotechnological developments in the form of retroviral and lentiviral vectors for the transduction of cells in tissue culture and, potentially, gene therapy. However, despite considerable research focus in this area, there is much we still do not understand about the HIV replicative cycle, particularly the first steps that are crucial to establishing a productive infection. One especially enigmatic player has been the HIV capsid. In this review, we discuss three aspects of the HIV capsid: its function as a structural shell, its role in mediating host interactions, and its vulnerability to antiviral activity.

Human Immunodeficiency Virus and Simian Immunodeficiency Virus Maintain High Levels of Infectivity in the Complete Absence of Mucin-Type O-Glycosylation.

A highly conserved threonine near the C terminus of gp120 of human immunodeficiency virus (HIV) and simian immunodeficiency virus (SIV) was investigated for its contributions to envelope protein function and virion infectivity. When this highly conserved Thr residue was substituted with anything other than serine (the other amino acid that can accept O-glycosylation), the resulting virus was noninfectious. We found that this Thr was critical for the association of gp120 with the virion and that amino acid substitution increased the amount of dissociated gp120 in the cell culture supernatant. When HIV virions were generated in cells overexpressing polypeptide N-acetylgalactosaminyltransferase 1 (GalNAcT1), viral infectivity was increased 2.5-fold compared to that of virus produced in wild-type HEK293T cells; infectivity was increased 8-fold when the Thr499Ser mutant was used. These infectivity enhancements were not observed when GalNAcT3 was used. Using HEK293T knockout cell lines totally devoid of the ability to perform O-linked glycosylation, we demonstrated production of normal levels of virions and normal levels of infectivity in the complete absence of O-linked carbohydrate. Our data indicate that O-glycosylation is not necessary for the natural replication cycle of HIV and SIV. Nonetheless, it remains theoretically possible that the repertoire of GalNAc transferase isoforms in natural target cells for HIV and SIV in vivo could result in O-glycosylation of the threonine residue in question and that this could boost the infectivity of virions beyond the levels seen in the absence of such O-glycosylation.IMPORTANCE Approximately 50% of the mass of the gp120 envelope glycoprotein of both HIV and SIV is N-linked carbohydrate. One of the contributions of this N-linked carbohydrate is to shield conserved peptide sequences from recognition by humoral immunity. This N-linked glycosylation is one of the reasons that primary isolates of HIV and SIV are so heavily resistant to antibody-mediated neutralization. Much less studied is any potential contribution from O-linked glycosylation. The literature on this topic to date is somewhat confusing and ambiguous. Our studies described in this report demonstrate unambiguously that O-linked glycosylation is not necessary for the natural replication cycle of HIV and SIV. However, the door is not totally closed because of the diversity of numerous GalNAc transferase enzymes that initiate O-linked carbohydrate attachment and the theoretical possibility that natural target cells for HIV and SIV in vivo could potentially complete such O-linked carbohydrate attachment to further increase infectivity.

The interaction of RNA helicase DDX3 with HIV-1 Rev-CRM1-RanGTP complex during the HIV replication cycle.

Molecular traffic between the nucleus and the cytoplasm is regulated by the nuclear pore complex (NPC), which acts as a highly selective channel perforating the nuclear envelope in eukaryotic cells. The human immunodeficiency virus (HIV) exploits the nucleocytoplasmic pathway to export its RNA transcripts across the NPC to the cytoplasm. Despite extensive study on the HIV life cycle and the many drugs developed to target this cycle, no current drugs have been successful in targeting the critical process of viral nuclear export, even though HIV’s reliance on a single host protein, CRM1, to export its unspliced and partially spliced RNA transcripts makes it a tempting target. Due to recent findings implicating a DEAD-box helicase, DDX3, in HIV replication and a member of the export complex, it has become an appealing target for anti-HIV drug inhibition. In the present research, we have applied a hybrid computational protocol to analyze protein-protein interactions in the HIV mRNA export cycle. This method is based on molecular docking followed by molecular dynamics simulation and accompanied by approximate free energy calculation (MM/GBSA), computational alanine scanning, clustering, and evolutionary analysis. We highlight here some of the most likely binding modes and interfacial residues between DDX3 and CRM1 both in the absence and presence of RanGTP. This work shows that although DDX3 can bind to free CRM1, addition of RanGTP leads to more concentrated distribution of binding modes and stronger binding between CRM1 and RanGTP.

Identification of myxobacteria-derived HIV inhibitors by a high-throughput two-step infectivity assay

BackgroundDrug-resistance and therapy failure due to drug-drug interactions are the main challenges in current treatment against Human Immunodeficiency Virus (HIV) infection. As such, there is a continuous need for the development of new and more potent anti-HIV drugs. Here we established a high-throughput screen based on the highly permissive TZM-bl cell line to identify novel HIV inhibitors. The assay allows discriminating compounds acting on early and/or late steps of the HIV replication cycle.ResultsThe platform was used to screen a unique library of secondary metabolites derived from myxobacteria. Several hits with good anti-HIV profiles were identified. Five of the initial hits were tested for their antiviral potency. Four myxobacterial compounds, sulfangolid C, soraphen F, epothilon D and spirangien B, showed EC50 values in the nM range with SI > 15. Interestingly, we found a high amount of overlapping hits compared with a previous screen for Hepatitis C Virus (HCV) using the same library.ConclusionThe unique structures and mode-of-actions of these natural compounds make myxobacteria an attractive source of chemicals for the development of broad-spectrum antivirals. Further biological and structural studies of our initial hits might help recognize smaller drug-like derivatives that in turn could be synthesized and further optimized.

Molecular Modeling Studies and ADME Screening on HIV-1 Integrase Inhibitors as Anti-Viral Agents

Human immunodeficiency virus (HIV) is a lentivirus, a member of the retrovirus family, which leads to acquired immunodeficiency syndrome (AIDS). HIV is present as both free virus particles and virus within infected immune cells. Integration of viral DNA into the host chromosome is the key process in the HIV replication cycle and therefore Integrase has served as an attractive target for antivirals. HIV-1 Integrase (HIV-1 IN) is an essential enzyme in the life cycle of the virus, responsible for catalyzing the insertion of the viral genome into the host cell chromosome and it provides an attractive target for antiviral drug design. Antiretroviral treatment reduces both the mortality and the morbidity of HIV infection. Raltegravir, also known as Isentress and MK-0518, is a well known integrase inhibitor. This prevents the virus from making new copies of HIV. Structures similar to this compound were identified and molecular modeling studies has been performed with HIV-1 IN as target molecule using SchrA¶dinger Suite 2007. PASS (prediction of activity spectra for substances) prediction of the compounds was carried out and all compounds exhibited anti-viral activity. These compounds show favorable interactions with the amino acid residues and the metal ion (Mg2+) at the active site of HIV-1 IN thereby substantiating their proven efficacy as anti-viral compounds. Further, their ADME (Absorption, Digestion, Metabolism and Excretion) screening was also carried out in order to check their potency to be used for second-generation drug development. The work demonstrates that molecular modeling, activity prediction and screening of the compounds for their subsequent ADME properties is a promising approach to predict the binding activity of compounds to the receptor.

Neuropathogenesis of Central Nervous System HIV Infection

CME Educational Objectives 1. Understand basic HIV structure and replication cycle. 2. Describe basic neuropathogenesis of HIV. 3. Discuss the potential role of neuroimaging in the diagnosis and clinical monitoring of HIV-associated neurocognitive disorders (HAND). Human immunodeficiency virus (HIV)-associated neurocognitive disorders (HAND) are a common and devastating complication of HIV infection, affecting up to 47% of HIV-seropositive individuals in the combination antiretroviral (cART) era. 1 Because HAND independently predicts non-central nervous system (CNS) morbidity and overall HIV mortality, 2 there is an urgent need to better understand these disorders to develop therapeutic approaches. However, HIV neuropathogenesis, HAND, and its related neuropathology, HIV-encephalitis (HIVE), are complex and incompletely understood. This article describes the current understanding of the basic virology and neuropathogenesis of HIV that contribute to HAND and HIVE.

Backbone resonance assignments of the micro-RNA precursor binding region of human TRBP

TAR-RNA binding protein (TRBP) is a multidomain human protein involved in micro-RNA (miRNA) biogenesis. TRBP is a component of both the Dicer complex, which processes precursor miRNAs, and the RNA-induced silencing complex-loading complex. In addition, TRBP is implicated in the human immunodeficiency virus replication cycle and interferon-protein kinase R activity. TRBP contains 3 double-stranded RNA binding domains the first two of which have been shown to interact with miRNA precursors. Here we present the backbone resonance assignments and secondary structure of residues 19-228 of human TRBP2.

Coreceptor usage by HIV-1 and HIV-2 primary isolates: The relevance of CCR8 chemokine receptor as an alternative coreceptor

The human immunodeficiency virus replication cycle begins by sequential interactions between viral envelope glycoproteins with CD4 molecule and a member of the seven-transmembrane, G-protein-coupled, receptors' family (coreceptor). In this report we focused on the contribution of CCR8 as alternative coreceptor for HIV-1 and HIV-2 isolates. We found that this coreceptor was efficiently used not only by HIV-2 but particularly by HIV-1 isolates. We demonstrate that CXCR4 usage, either alone or together with CCR5 and/or CCR8, was more frequently observed in HIV-1 than in HIV-2 isolates. Directly related to this is the finding that the non-usage of CXCR4 is significantly more common in HIV-2 isolates; both features could be associated with the slower disease progression generally observed in HIV-2 infected patients. The ability of some viral isolates to use alternative coreceptors besides CCR5 and CXCR4 could further impact on the efficacy of entry inhibitor therapy and possibly also in HIV pathogenesis.

Science Underlying 2008 Nobel Prizes

JCE offers a wealth of materials for teaching and learning chemistry that you can explore online. In the list below, Bernadette Caldwell of the Editorial Staff suggests additional resources that are available through JCE for teaching the science behind some of the 2008 Nobel Prizes. Discovering and Applying the Chemistry of GFP The Royal Swedish Academy of Sciences awarded the 2008 Nobel Prize in Chemistry for the discovery and development of the green fluorescent protein, GFP to three scientists: Osamu Shimomura, Martin Chalfie, and Roger Y. Tsien. These scientists led the field in discovering and introducing a fluorescing protein from jellyfish into cells and genes under study, which allows researchers to witness biochemistry in action. Now tags are available that emit light in different colors, revealing myriad biological processes and their interactions simultaneously. Identifying HPV and HIV, HIV's Replication Cycle, and HIV VirusHost Interactions The Nobel Assembly at Karolinska Institutet awarded the 2008 Nobel Prize in Medicine or Physiology for their discovery of human immunodeficiency virus (HIV) to two scientists: Francoise Barre-Sinoussi and Luc Montagnier; and for his discovery of human papilloma viruses [HPV] causing cervical cancer to one scientist, Harald zur Hausen. Diseases caused by these infectious agents significantly affect global health. While isolating and studying the virus, researchers discovered HIV is an uncommon retrovirus that infects humans and relies on the host to make its viral DNA, infecting and killing the host's white blood cells, ultimately destroying the immune systems of infected humans. Related Resources at JCE Online The Journal has published articles relating to GFP specifically, and more generally to fluorescing compounds applied to biochemistry. The Journal has also published an article and a video on protease inhibitiona strategy to suppress HIV's biological processes. With the video clips, an accompanying guide for teachers includes instructions for three student activities that use enzymes. The resources below may help introduce students to the science behind some of these Nobel Prizes. Turning on the Light: Lessons from Luminescence. O'Hara, P. B.; Engelson, C.; St. Peter, W. J. Chem. Educ. 2005, 82, 49. (See especially the bioluminescence section on page 51 that concisely explains GFP.) JCE Classroom Activity #68: Turning on the Light. O'Hara, P. B.; Engelson, C.; St. Peter, W. J. Chem. Educ. 2005, 82, 48A. JCE Classroom Activity #81: pHantastic Fluorescence. Muyskens, M. J. Chem. Educ. 2006, 83, 768A. Recombinant Green Fluorescent Protein Isoforms: Exercises To Integrate Molecular Biology, Biochemistry, and Biophysical Chemistry. Hicks, B. W. J. Chem. Educ. 1999, 76, 409. C-SNARF-1 as a Fluorescent Probe for pH Measurements in Living Cells: Two-Wavelength-Ratio Method versus Whole-Spectral-Resolution Method. Ribou, A-C.; Vigo, J.; Salmon, J-M. J. Chem. Educ. 2002, 79, 1471. An Attack on the AIDS Virus: Inhibition of the HIV-1 Protease: New Drug Development Based on the Structure and Activity of the Protease and Its Role in the Replication and Maturation of the Virus. Volker, E. J. J. Chem. Educ. 1993, 70, 3. From Chemistry Comes Alive!, five video clips demonstrate properties and mechanisms involved in the chemistry of HIV. HIV-1 Protease: An Enzyme at Work. All articles from Volume 1 to the current issue are available in full-text PDF at JCE Online: Browse by year, month, and page, or choose title and author searching of all issues of JCE

Ubiquitin ligases as therapeutic targets in HIV-1 infection

Background: Introduction of highly active antiretroviral therapy has led to a profound reduction in human immunodeficiency virus (HIV) related mortality; although, the complete eradication of the virus from infected individuals has never been achieved. In addition, due to the high mutation and evolution rate, drug-resistant viruses are continuously emerging. Objective: Genetically more stable cellular pathways represent attractive targets for innovative antiviral strategies, especially the ubiquitin proteasome system, which regulates various steps in the HIV replication cycle. Methods: This review focuses on certain interactions of HIV and E3 ligases as a major player in the ubiquitin proteasome system. Results/conclusion: Due to the importance in HIV replication, and together with the high substrate specificity, E3 ligases can be considered as bona fide targets to interfere with HIV infection.

Defining and solving the essential protein–protein interactions in HIV infection

The structure determination of macromolecular complexes is entering a new era. The methods of optical microscopy, electron microscopy, X-ray crystallography, and nuclear magnetic resonance increasingly are being combined in hybrid method approaches to achieve an integrated view of macromolecular complexes that span from cellular context to atomic detail. A particularly important application of these hybrid method approaches is the structural analysis of the Human Immunodeficiency Virus (HIV) proteins with their cellular binding partners. High resolution structure determination of essential HIV – host cell protein complexes and correlative analysis of these complexes in the live cell can serve as critical guides in the design of a broad, new class of therapeutics that function by disrupting such complexes. Here, with the hope of stimulating some discussion, we will briefly review some of the literature in the context of what could be done to further apply structural methods to HIV research. We have chosen to focus our attention on certain aspects of the HIV replication cycle where we think that structural information would contribute substantially to the development of new therapeutic and vaccine targets for HIV.

The regulation of HIV-1 transcription: molecular targets for chemotherapeutic intervention.

The regulation of transcription of the human immunodeficiency virus (HIV) is a complex event that requires the cooperative action of both viral and cellular components. In latently infected resting CD4+ T cells HIV‐1 transcription seems to be repressed by deacetylation events mediated by histone deacetylases (HDACs). Upon reactivation of HIV‐1 from latency, HDACs are displaced in response to the recruitment of histone acetyltransferases (HATs) by NF‐κB or the viral transcriptional activator Tat and result in multiple acetylation events. Following chromatin remodeling of the viral promoter region, transcription is initiated and leads to the formation of the TAR element. The complex of Tat with p‐TEFb then binds the loop structures of TAR RNA thereby positioning CDK9 to phosphorylate the cellular RNA polymerase II. The Tat‐TAR‐dependent phosphorylation of RNA polymerase II plays an important role in transcriptional elongation as well as in other post‐transcriptional events. As such, targeting of Tat protein (and/or cellular cofactors) provide an interesting perspective for therapeutic intervention in the HIV replicative cycle and may afford lifetime control of the HIV infection. © 2006 Wiley Periodicals, Inc. Med Res Rev, 26, No. 5, 595–625, 2006

Recent Advances in the Discovery and Development of Plant-Derived Natural Coumarins and their Analogues as Anti Human Immunodeficiency Virus—Type 1 (HIV-1) Agents

ABSTRACTThe acquired immunodeficiency syndrome (AIDS) is a result of human immunodeficiency virus (HIV) infection which leads to severe suppression of immune functions. AIDS is a real threat to the health of mankind, and the search for effective therapies is still of great importance. However, besides the high cost, there are adverse effects and limitations associated with chemotherapy applied. Thus, herbal medicines are frequently used as an alternative therapy by individuals living with HIV. Numerous plant-derived compounds have been evaluated for inhibitory effects on HIV replication, and many coumarins have been found to inhibit different steps in HIV replication cycle. The aim of this review is to summarize research findings for herbal medicines, especially coumarins, which are endowed with the ability to inhibit HIV.

CpG Oligodeoxynucleotides Block Human Immunodeficiency Virus Type 1 Replication in Human Lymphoid Tissue Infected Ex Vivo

Oligodeoxynucleotides (ODNs) with immunomodulatory motifs control a number of microbial infections in animal models, presumably by acting through toll-like receptor 9 (TLR9) to induce a number of cytokines (e.g., alpha interferon and tumor necrosis factor alpha). The immunomodulatory motif consists of unmethylated sequences of cytosine and guanosine (CpG motif). ODNs without CpG motifs do not trigger TLR9. We hypothesized that triggering of TLR9 generates a cellular environment unfavorable for human immunodeficiency virus (HIV) replication. We tested this hypothesis in human lymphocyte cultures and found that phosphorothioate-modified ODN CpG2006 (type B ODNs) inhibited HIV replication nearly completely and prevented the loss of CD4(+) T cells. ODNs CpG2216 and CpG10 (type A ODNs) were less effective. CpG2006 blocked HIV replication in purified CD4(+) T cells and T-cell lines; CpG10 was ineffective in this setting, indicating that type A ODNs may inhibit HIV replication in CD4(+) T-cell lines indirectly through a separate cell subset. However, control ODNs without CpG motifs also showed anti-HIV effects, indicating that these effects are nonspecific and not due to TLR9 triggering. The mechanism of action is not clear. CpG2006 and its control ODN blocked syncytium formation in a cell fusion-based assay, but CpG10, CpG2216, and their control ODNs did not. The latter types interfered with the HIV replication cycle during disassembly or reverse transcription. In contrast, CpG2006 and CpG2216 specifically induced cytokines critical to initiation of the innate immune response. In summary, the nonspecific anti-HIV activity of CpG ODNs, their ability to stimulate HIV replication in latently infected cells, potentially resulting in their elimination, and their documented ability to link the innate and adaptive immune responses make them attractive candidates for further study as anti-HIV drugs.

Host cell gene expression during human immunodeficiency virus type 1 latency and reactivation and effects of targeting genes that are differentially expressed in viral latency.

The existence of reservoirs of cells latently infected with human immunodeficiency virus (HIV) is a major obstacle to the elimination of HIV infection. We studied the changes in cellular gene expression that accompany the reactivation and completion of the lytic viral cycle in cell lines chronically infected with HIV-1. We found that several genes exhibited altered expression in the chronically infected cells compared to the uninfected parental cells prior to induction into lytic replication. A number of gene classes showed increased expression in the chronically infected cells, notably including genes encoding proteasomes, histone deacetylases, and many transcription factors. Following induction of the lytic replication cycle, we observed ordered, time-dependent changes in the cellular gene expression pattern. Approximately 1,740 genes, many of which fall into 385 known pathways, were differentially expressed (P < 0.001), indicating that completion of the HIV replication cycle is associated with distinct, temporally ordered changes in host cell gene expression. Maximum changes were observed in the early and intermediate phases of the lytic replication cycle. Since the changes in gene expression in chronically infected cells suggested that cells latently infected with HIV have a different gene expression profile than corresponding uninfected cells, we studied the expression profiles of three different chronically infected cell lines to determine whether they showed similar changes in common cellular genes and pathways. Thirty-two genes showed significant differential expression in all cell lines studied compared to their uninfected parental cell lines. Notable among them were cdc42 and lyn, which were downregulated and are required for HIV Nef binding and viral replication. Other genes previously unrelated to HIV latency or pathogenesis were also differentially expressed. To determine the effects of targeting products of the genes that were differentially expressed in latently infected cells, we treated the latently infected cells with a proteasome inhibitor, clastolactacystin-beta-lactone (CLBL), and an Egr1 activator, resveratrol. We found that treatment with CLBL and resveratrol stimulated lytic viral replication, suggesting that treatment of cells with agents that target cellular genes differentially expressed in latently infected cells can stimulate lytic replication. These findings may offer new insights into the interaction of the latently infected host cell and HIV and suggest therapeutic approaches for inhibiting HIV infection and for manipulating cells latently infected with HIV so as to trigger lytic replication.

Novel human immunodeficiency virus (HIV) inhibitors that have a dual mode of anti-HIV action.

We have found that novel pyridine oxide derivatives are inhibitors of a wide range of human immunodeficiency virus (HIV) type 1 (HIV-1) and HIV-2 strains in CEM cell cultures. Some of the compounds showed inhibitory activities against recombinant HIV-1 reverse transcriptase (RT), whereas others were totally inactive against this viral protein in vitro. Partial retention of anti-HIV-1 activity against virus strains that contain a variety of mutations characteristic of those for resistance to nonnucleoside RT inhibitors and a lack of inhibitory activity against recombinant HIV-2 RT suggested that these pyridine oxide derivatives possess a mode of antiviral action independent from HIV RT inhibition. Time-of-addition experiments revealed that these pyridine oxide derivatives interact at a postintegration step in the replication cycle of HIV. Furthermore, it was shown that these compounds are active not only in acutely HIV-1-infected cells but also in chronically HIV-infected cells. A dose-dependent inhibition of virus particle release and viral protein expression was observed upon exposure to the pyridine oxide derivatives. Finally, inhibition of HIV-1 long terminal repeat-mediated green fluorescence protein expression in quantitative transactivation bioassays indicated that the additional target of action of the pyridine oxide derivatives may be located at the level of HIV gene expression.

Crystal structures of the catalytic domain of HIV-1 integrase free and complexed with its metal cofactor: high level of similarity of the active site with other viral integrases

Human immunodeficiency virus (HIV) integrase is the enzyme responsible for insertion of a DNA copy of the viral genome into host DNA, an essential step in the replication cycle of HIV. HIV-1 integrase comprises three functional and structural domains: an N-terminal zinc-binding domain, a catalytic core domain and a C-terminal DNA-binding domain. The catalytic core domain with the F185H mutation has been crystallized without sodium cacodylate in a new crystal form, free and complexed with the catalytic metal Mg2+. The structures have been determined and refined to about 2.2 Å. Unlike the previously reported structures, the three active-site carboxylate residues (D,D-35-E motif) are well ordered and both aspartate residues delineate a proper metal-binding site. Comparison of the active binding site of this domain with that of other members from the polynucleotidyl transferases superfamily shows a high level of similarity, providing a confident template for the design of antiviral agents.

A Randomized Controlled Study for the Evaluation of the Activity of a Triple Combination of Zidovudine, Thymosin-α1 and Interferon-α in HIV-Infected Individuals with CD4 Counts between 200 and 500 cells/mm3

Our objective was to determine the safety and the activity of thymosin-α1 (Tα1) plus interferon-α (IFN-α) and zidovudine in human immunodeficiency virus (HIV)-infected patients with CD4 counts between 200 and 500 cells/mm3. The study was multicentre, Phase II, randomized and open label. Patients were randomized to receive triple therapy, or zidovudine plus IFN-α, or zidovudine alone. Ninety-two patients were enrolled. After 12 months, in the triple combination group there was a median increase from baseline of 69 CD4 cells/mm3; a decrease of 52 cells/mm3 and of 65.5 cells/mm3 was seen in the zidovudine plus IFN-α and in the zidovudine monotherapy groups, respectively. In the triple combination arm the increase in mean CD4 counts was significantly greater than that observed in the other arms, particularly in patients with baseline CD4 counts less than 350 cells/mm3. The plasma HIV RNA load in triple therapy group showed a mean peak decrease from baseline of 16 000 copies/ml after 5 months (versus a decrease of 5000 copies/ml in the zidovudine monotherapy group) that was sustained at 12 months (versus a mean increase of 7000 copies/ml in the zidovudine monotherapy group at 12 months). The triple combination was superior to both the other arms in terms of virological and immunological response. Our study, although based on regimens of clearly sub-optimal antiretroviral potency, addressed the issue of combined therapy directed at two different targets: the HIV replicative cycle and the immune system. The use of immunomodulating agents deserves further investigation in the context of more potent antiretroviral combinations.

Antiviral Metal Complexes

The initial events (virus adsorption and fusion with the cells) in the replicative cycle of human immunodeficiency virus (HIV) can serve as targets for the antiviral action of metal-binding compounds such as polyanionic compounds (polysulfates, polysulfonates, polycarboxylates, polyoxometalates, and sulfonated or carboxylated metalloporphyrins), bicyclams and G-octet-forming oligonucleotides. The adsorption and fusion of HIV with its target cells depends on the interaction of the viral envelope glycoproteins (gp 120) with the receptors (CD4, CXCR4) at the outer cell membrane. We are currently investigating how the aforementioned compounds interfere with these viral glycoproteins and/or cell receptor.