HIV-1 Inhibitory Activity Research Articles

Ribonuclease is partly responsible for the HIV-1 inhibitory effect activated by HLA alloantigen recognition

This study was performed to determine whether ribonucleases (RNases) contribute to the soluble HIV-1 inhibitory activity that results from the recognition of HLA alloantigens. Supernatants from mixed lymphocyte reactions of peripheral blood mononuclear cells from healthy HLA-discordant individuals exhibited HIV-1 inhibitory activity (alloantigen-stimulated factors; ASF). These supernatants were tested for their sensitivity to heating (90 degrees C for 3 min), and for the presence of three RNases belonging to the RNase A superfamily: eosinophil-derived neurotoxin (EDN); RNase A; and angiogenin. Polyclonal antibodies specific for these RNases were used for Western blot analysis of the ASF, as well as for blocking the HIV-1 inhibitory activity of ASF. In addition, an RNase inhibitor (RI) was used to determine whether the anti-viral activity of ASF was due to RNase activity. HIV-1 inhibitory activity of ASF was: (i). resistant to heat treatment; (ii). blocked by 58% with an antibody specific for EDN, but not with antibodies against RNase A or angiogenin; and (iii) blocked by 65-100% with an RI. Moreover, Western blot analysis with an anti-EDN antibody detected EDN in the ASF. These findings indicate that the majority of the soluble HIV-1 inhibitory activity contained in the supernatants of mixed lymphocyte reactions is due to EDN or a closely related RNase.

Integracides: tetracyclic triterpenoid inhibitors of HIV-1 integrase produced by Fusarium sp.

HIV-1 integrase is a critical enzyme in the replication of HIV-1. It is absent in the host cells and therefore is a good target for treatment of HIV-1 infections. Integracides are members of the tetracyclic triterpenoids family that were isolated from the fermentation broth of a Fusarium sp. Integracide A, a sulfated ester, exhibited significant inhibitory activity against strand transfer reaction of HIV-1 integrase. The discovery, structure elucidation including single crystal X-ray structure and HIV-1 inhibitory activity of these compounds are described.

Unusual sulfamate indoles and a novel indolo[3,2-a]carbazole from Ancorina sp.

Four new indoles, ancorinolates A-C and bis-ancorinolate B, which contain sulfamate and sulfate groups, were isolated from the aqueous extract of the sponge Ancorina sp. In addition, ancorinazole, an indolo[3,2-a]carbazole also possessing sulfamate and sulfate groups, was isolated from two separate New Zealand collections of Ancorina sp. Ancorinazole is the first indolo[3,2-a]carbazole described as a natural product. Ancorinolates A (1) and C (3) showed weak HIV-inhibitory activity in the XTT-based, anticytopathicity assay.

Optimal Inhibition of X4 HIV Isolates by the CXC Chemokine Stromal Cell-derived Factor 1α Requires Interaction with Cell Surface Heparan Sulfate Proteoglycans

The chemokine stromal cell-derived factor 1 (SDF-1) is the natural ligand for CXC chemokine receptor 4 (CXCR4). SDF-1 inhibits infection of CD4+ cells by X4 (CXCR4-dependent) human immunodeficiency virus (HIV) strains. We previously showed that SDF-1 alpha interacts specifically with heparin or heparan sulfates (HSs). Herein, we delimited the boundaries of the HS-binding domain located in the first beta-strand of SDF-1 alpha as the critical residues. We also provide evidence that binding to cell surface heparan sulfate proteoglycans (HSPGs) determines the capacity of SDF-1 alpha to prevent the fusogenic activity of HIV-1 X4 isolates in leukocytes. Indeed, SDF-1 alpha mutants lacking the capacity to interact with HSPGs showed a substantially reduced capacity to prevent cell-to-cell fusion mediated by X4 HIV envelope glycoproteins. Moreover, the enzymatic removal of cell surface HS diminishes the HIV-inhibitory capacity of the chemokine to the levels shown by the HS-binding-disabled mutant counterparts. The mechanisms underlying the optimal HIV-inhibitory activity of SDF-1 alpha when attached to HSPGs were investigated. Combining fluorescence resonance energy transfer and laser confocal microscopy, we demonstrate the concomitant binding of SDF-1 alpha to CXCR4 and HSPGs at the cell membrane. Using FRET between a Texas Red-labeled SDF-1 alpha and an enhanced green fluorescent protein-tagged CXCR4, we show that binding of SDF-1 alpha to cell surface HSPGs modifies neither the kinetics of occupancy nor activation in real time of CXCR4 by the chemokine. Moreover, attachment to HSPGs does not modify the potency of the chemokine to promote internalization of CXCR4. Attachment to cellular HSPGs may co-operate in the optimal anti-HIV activity of SDF-1 alpha by increasing the local concentration of the chemokine in the surrounding environment of CXCR4, thus facilitating sustained occupancy and down-regulation of the HIV coreceptor.

Anti-HIV prenylated flavonoids from Monotes africanus.

Six flavonoids, among them a new dihydroflavonol, 6,8-diprenylaromadendrin (1), and the flavonol 6,8-diprenylkaempferol (3), have been isolated from the organic extract of Monotes africanus. The isolated compounds containing a 5,7-dihydroxy-6,8-diprenyl system in the A ring of the flavonoid (1, 3, and 6) exhibited HIV-inhibitory activity in the XTT-based, whole-cell screen. In addition, several (13)C NMR assignments of lonchocarpol A (6) were corrected.

Enhancement of the HIV-1 inhibitory activity of RANTES by modification of the N-terminal region: dissociation from CCR5 activation.

Although selected chemokines act as natural inhibitors of human immunodeficiency virus (HIV) infection, their inherent proinflammatory activity may limit a therapeutic use. To elucidate whether the antiviral and signaling functions of RANTES can be dissociated, several recombinant analogues mutated at the N terminus were generated and functionally compared with the wild-type (WT) molecule, as well as with three previously described mutants. Substitution of selected residues within the N-terminal region caused a marked loss of antiviral potency. By contrast, two unique analogues (C1.C5-RANTES and L-RANTES) exhibited an increased antiviral activity against different CXCR4-negative HIV-1 isolates grown in primary mononuclear cells or in macrophages. This enhanced HIV-blocking activity was associated with an increased binding affinity for CCR5. Both C1.C5-RANTES and L-RANTES showed a dramatically reduced ability to trigger intracellular calcium mobilization via CCR3 or CCR5, while potently antagonizing the action of the WT chemokine. By contrast, two previously described analogues (RANTES(3-68) and AOP-RANTES) maintained a WT ability to trigger CCR5-mediated signaling, while a third one (RANTES(9-68)) showed a dramatic loss of antiviral activity. These data demonstrate that the antiviral and signaling functions of RANTES can be uncoupled, opening new perspectives for the development of chemokine-based therapeutic approaches for HIV infection.

A Salt Bridge between an N-terminal Coiled Coil of gp41 and an Antiviral Agent Targeted to the gp41 Core Is Important for Anti-HIV-1 Activity

HIV-1 envelope glycoprotein transmembrane subunit gp41 play a critical role in the fusion of viral and target cell membranes. The gp41 C-terminal heptad repeat region interacts with the N-terminal coiled-coil region to form a six-stranded core structure. Peptides derived from gp41 C-terminal heptad repeat region (C-peptides) are potent HIV-1 entry inhibitors by binding to gp41 N-terminal coiled-coil region. Most recently, we have identified two small organic compounds that inhibit HIV-1-mediated membrane fusion by blocking the formation of gp41 core. These two active compounds contain both hydrophobic and acidic groups while the inactive compounds only have hydrophobic groups. Analysis by computer modeling indicate that the acidic groups in the active compounds can form salt bridge with Lys 574 in the N-terminal coiled-coil region of gp41. Asp 632 in a C-peptide can also form a salt bridge with Lys 574. Replacement of Asp 632 with positively charged residues or hydrophobic residues resulted in significant decrease of HIV-1 inhibitory activity. These results suggest that a salt bridge between an N-terminal coiled coil of the gp41 and an antiviral agent targeted to the gp41 core is important for anti-HIV-1 activity.

HIV-inhibitory cembrane derivatives from a Philippines collection of the soft coral Lobophytum species.

Bioassay-guided fractionation of an aqueous extract of a Philippine Islands collection of the soft coralLobophytum sp. concentrated its HIV-inhibitory activity into fractions rich in cembranoid diterpenes. Lobohedleolide (1), (7Z)-lobohedleolide (2), and a new compound, 17-dimethylaminolobohedleolide (3), were purified from these fractions by HPLC. The structures of compounds 1-3 were elucidated by spectroscopic analyses and by comparison of their spectral data with previously reported values. The relative stereochemistry of the gamma-lactone ring substituents of 3 was determined by 1D NOESY experiments. While several other cembranoids that contain a dimethylamino functional group have been reported from the soft coral Sinularia sp., compound 3 represents the first cembrane diterpene with this functional group isolated from a Lobophytum species. Diterpenoids 1-3 exhibited moderate HIV-inhibitory activity (EC(50) approximately 3-5 microg/mL) in a cell-based in vitro anti-HIV assay.

Siamenol, a new carbazole alkaloid from Murraya siamensis.

A new carbazole alkaloid, siamenol (1), and two known alkaloids, mahanimbine (2) and mahanimbilol (3), have been isolated from the organic extract of Murraya siamensis. The novel compound exhibited HIV-inhibitory activity.

Chemical and enzymatic modifications of integric acid and HIV-1 integrase inhibitory activity

Integric acid (1), an acyl eremophilane sesquiterpenoid, was identified as an inhibitor of HIV-1 integrase, the enzyme responsible for provirus entry into the host cell nucleus and integration in to the host genome. Chemical and enzymatic modification of integric acid led to the preparation of several selective chemical derivatives of integric acid. Preparation, HIV-1 inhibitory activity, and the structure–activity relationship against coupled and strand transfer assays are described. It appears that most of the groups present in the natural product are required for inhibition of HIV-1 integrase strand transfer activity. In contrast, inhibition of 3′ processing activity is less stringent suggesting distinct SAR for the two integrase reactions.

Synthesis and HIV-1 inhibitory properties of new tetrahydrobenzoquinazolinedione and tetrahydrobenzocycloheptenuracil derivatives and of their thioxo analogues

Some new tetrahydrobenzoquinazolinediones 2a– 4a, tetrahydrobenzocycloheptenuracils 5a, 6a and their thioxo analogues 2b– 6b were synthesized within a project aimed at obtaining new HIV-1 tricyclic inhibitors whose scaffold includes a pyrimidine and a phenyl ring, which are present in various HIV-1 non-nucleoside inhibitors. Among the tetrahydrobenzoquinazolinediones 2a– 4a, compounds 3a and 4a, in which the tricyclic system is respectively in an angular or linear arrangement, proved to possess a HIV-1 inhibitory activity which was in the micromolar range, while compound 2a, in which the tricyclic system is in the angular arrangement opposite to that of 3a, was found to be completely inactive. As regards the tetrahydrobenzocycloheptenuracil derivatives ( 5a and 6a), only 5a showed an inhibitory activity similar to that of 3a and 4a. Furthermore, all thioxo analogues 2b– 6b were found to be devoid of any activity.

Vismiaphenones D-G, new prenylated benzophenones from Vismia cayennensis.

Following anti-HIV bioassay-guided fractionation, four new prenylated benzophenones, vismiaphenones D-G (7-10), were isolated from extracts of leaves of Vismia cayennensis. The structures were elucidated by spectral analyses. Only vismiaphenone D (7) exhibited HIV-inhibitory activity in the NCI primary screen.

Guttiferone F, the first prenylated benzophenone from Allanblackia stuhlmannii.

The HIV-inhibitory activity in extracts of Allanblackia stuhlmannii was tracked, via bioassay-guided fractionation, to a new member of the camboginol/guttiferone class of prenylated benzophenones, guttiferone F (1). The structure was solved by extensive NMR analyses and by acid-catalyzed conversion to 30-epi-cambogin (4). This is the first report of this compound type in the genus Allanblackia.

HIV-inhibitory and cytotoxic oligostilbenes from the leaves of Hopea malibato.

Three new oligostilbenes, malibatols A (1) and B (2) and dibalanocarpol (3), together with one known oligostilbene balanocarpol (4), were isolated from the organic extract of the leaves of Hopea malibato. The structure elucidation of these compounds was based on the interpretation of their chemical and spectral data. Compounds 3 and 4 exhibited very modest HIV-inhibitory activity, while compounds 1 and 2 were cytotoxic to the host cells (CEM SS) in the antiviral assay.

Michellamines D-F, new HIV-inhibitory dimeric naphthylisoquinoline alkaloids, and korupensamine E, a new antimalarial monomer, from Ancistrocladus korupensis.

New monomeric (korupensamine E, 6) and dimeric (michellamines D-F, 7-9) naphthylisoquinoline alkaloids have been isolated from exracts of the tropical liana Ancistrocladus korupensis. Structures were determined by spectroanalytical methods, and stereochemistry was defined through NOE correlations, chemical degradation, and CD spectroscopy. Michellamines D-F exhibited in vitro HIV-inhibitory activity comparable to michellamine B, and korupensamine E exhibited in vitro antimalarial activity comparable to korupensamines A-D.

Zerumbone, an HIV-Inhibitory and Cytotoxic Sesquiterpene of Zingiber Aromaticum and Z. Zerumbet

Zerumbone and 3“,4”-O-diacetylafzelin were isolated from organic extracts of rhizomes of Zingiber aromaticum (Zingiberaceae), and zerumbone and 4-O-acetylafzelin were obtained from organic extracts of entire plants of Z. zerumbet. Zerumbone exhibited HIV-inhibitory and cytotoxic activities, while the afzelins were inactive in both assays.

Human submandibular saliva specifically inhibits HIV type 1.

Studies from a number of laboratories have shown the presence of factor(s) in whole, parotid, and submandibular human saliva capable of inhibiting HIV-1 infectivity in vitro. Data from our laboratory suggested that the level of anti-HIV-1 activity is higher in submandibular than parotid or whole saliva. Previous results obtained with pooled submandibular saliva from seronegative individuals included a filtration step following saliva-virus interaction. In this article, we present data on the HIV-1 inhibitory activity of individual submandibular saliva samples collected from 15 donors. We show that although anti-HIV activity is quantitatively similar in most individuals (9 of 15), some (4 of 15) are much less active than others and some (2 of 15) lack inhibitory activity. We also show that for most individuals the level of anti-HIV inhibitor is similar with or without a filtration step. However, 2 of the 15 samples demonstrated activity only after filtration. The quantitative and qualitative anti-HIV activity of individual saliva samples appeared to reflect differences in the individual donors. We further show that the anti-HIV activity of submandibular saliva is demonstrated not only against laboratory strains of HIV-1 but is similarly active against three clinical HIV-1 isolates. In contrast, submandibular saliva had little effect on the infectivity of HIV-2 or SIV.

A benzoic acid glycoside from Geniostoma antherotrichum

Fractionation of an HIV-inhibitory organic extract of Geniostoma antherotrichum afforded a glycoside derivative, which has been characterized as 2- hydroxy-3-O-β- d-glucopyranosyl-benzoic acid ( 1) on the basis of spectral analyses. The HIV-inhibitory activity of the extract was traced to polymeric tannins, while 1 was found to be inactive in the National Cancer Institute's primary anti-HIV screen.

Structure-activity modifications of the HIV-1 inhibitors (+)-calanolide A and (-)-calanolide B.

The delta 7,8 olefinic linkages within (+)-calanolide A(1) and (-)-calanolide B(2) were catalytically reduced to determine impact on the anti-HIV activity of the parent compounds. In addition, a series of structure modifications of the C-12 hydroxyl group in (-)-calanolide B was made to investigate the importance of that substituent to the HIV-1 inhibitory activity of these coumarins. A total of 14 analogs were isolated or prepared and compared to (+)-calanolide A and (-)-calanolide B in the NCI primary anti-HIV assay. While none of the compounds showed activity superior to the two unmodified leads, some structure-activity requirements were apparent from the relative anti-HIV potencies of the various analogs.

Synthesis of imidazobenzazepinthiones: A new series of HIV-1 reverse transcriptase inhibitors

A general route to a series of novel imidazobenzazepines that are “carba” analogs of the TIBO class of non-nucleoside HIV-1 reverse transcriptase inhibitors has been developed. A pair of allyl side-chain containing compounds were found to have significant HIV-1 inhibitory activity.