Polyanion inhibitors of human immunodeficiency virus and other viruses. Part 2. Polymerized anionic surfactants derived from amino acids and dipeptides

Surface Active Agents and Their Health-Promoting Properties: Molecules of Multifunctional Significance

Surface active agents (SAAs) are molecules with the capacity to adsorb to solid surfaces and/or fluid interfaces, a property that allows them to act as multifunctional ingredients (e.g., wetting and dispersion agents, emulsifiers, foaming and anti-foaming agents, lubricants, etc.) in a widerange of the consumer products of various industrial sectors (e.g., pharmaceuticals, cosmetics, personal care, detergents, food, etc.). Given their widespread utilization, there is a continuously growing interest to explore their role in consumer products (relevant to promoting human health) and how such information can be utilized in order to synthesize better chemical derivatives. In this review article, weaimed to provide updated information on synthetic and biological (biosurfactants) SAAs and their health-promoting properties (e.g., anti-microbial, anti-oxidant, anti-viral, anti-inflammatory, anti-cancer and anti-aging) in an attempt to better define some of the underlying mechanism(s) by which they exert such properties.

The Low-Cost Compound Lignosulfonic Acid (LA) Exhibits Broad-Spectrum Anti-HIV and Anti-HSV Activity and Has Potential for Microbicidal Applications

Objectives

Lignosulfonic acid (LA), a low-cost lignin-derived polyanionic macromolecule, was extensively studied for its anti-HIV and anti-HSV activity in various cellular assays, its mechanism of viral inhibition and safety profile as potential microbicide.

Results

LA demonstrated potent inhibitory activity of HIV replication against a wide range of R5 and X4 HIV strains and prevented the uptake of HIV by bystander CD4⁺ T cells from persistently infected T cells in vitro (IC₅₀: 0.07 – 0.34 μM).

LA also inhibited HSV-2 replication in vitro in different cell types (IC₅₀: 0.42 – 1.1 μM) and in rodents in vivo. Furthermore, LA neutralized the HIV-1 and HSV-2 DC-SIGN-mediated viral transfer to CD4⁺ T cells (IC₅₀: ∼1 μM). In addition, dual HIV-1/HSV-2 infection in T cells was potently blocked by LA (IC₅₀: 0.71 μM). No antiviral activity was observed against the non-enveloped viruses Coxsackie type B4 and Reovirus type 1.

LA is defined as a HIV entry inhibitor since it interfered with gp120 binding to the cell surface of T cells. Pretreatment of PBMCs with LA neither increased expression levels of cellular activation markers (CD69, CD25 and HLA-DR), nor enhanced HIV-1 replication. Furthermore, we found that LA had non-antagonistic effects with acyclovir, PRO2000 or LabyA1 (combination index (CI): 0.46 – 1.03) in its anti-HSV-2 activity and synergized with tenofovir (CI: 0.59) in its anti-HIV-1 activity. To identify mechanisms of LA resistance, we generated in vitro a mutant HIV-1 NL4.3^LAresistant virus, which acquired seven mutations in the HIV-1 envelope glycoproteins: S160N, V170N, Q280H and R389T in gp120 and K77Q, N113D and H132Y in gp41. Additionally, HIV-1 NL4.3^LAresistant virus showed cross-resistance with feglymycin, enfuvirtide, PRO2000 and mAb b12, four well-described HIV binding/fusion inhibitors. Importantly, LA did not affect the growth of vaginal Lactobacilli strains.

Conclusion

Overall, these data highlight LA as a potential and unique low-cost microbicide displaying broad anti-HIV and anti-HSV activity.

Peptide nanofibrils as enhancers of retroviral gene transfer

Amyloid fibrils are polypeptide-based polymers that are typically associated with neurodegenerative disorders such as Alzheimer's disease. More recently, it has become clear that amyloid fibrils also fulfill functional roles in hormone storage and biosynthesis. Furthermore, it has been demonstrated that semen contains abundant levels of polycationic amyloid fibrils. The natural role of these seminal amyloids remains elusive. Strikingly, however, they drastically enhance HIV-1 infection and may be exploited by the virus to increase its sexual transmission rate. Their strong activity in enhancing HIV-1 infection suggests that seminal amyloid might also promote transduction by retroviral vectors. Indeed, SEVI (semen-derived enhancer of virus infection), the best characterized seminal amyloid, boosts retroviral gene transfer more efficiently than conventional additives. However, the use of SEVI as laboratory tool for efficient retroviral gene transfer is limited because the polypeptide monomers are relatively expensive to produce. Furthermore, standardized production of SEVI fibrils with similar high activities is difficult to achieve because of the stochastic nature of the amyloid assembly process. These obstacles can be overcome by recently identified smaller peptides that spontaneously self-assemble into nanofibrils. These nanofibrils increase retroviral gene transfer even more efficiently than SEVI, are easy to produce and to handle, and seem to be safe as assessed in an ex vivo gene transfer study. Furthermore, peptide-based nanofibrils allow to concentrate viral particles by low-speed centrifugation. Specific adaption and customization of self-assembling peptides might lead to novel nanofibrils with versatile biological functions, e.g., targeted retroviral gene transfer or drug delivery.

Comparing anti-HIV, antibacterial, antifungal, micellar, and cytotoxic properties of tricarboxylato dendritic amphiphiles

Three series of homologous dendritic amphiphiles--RCONHC(CH(2)CH(2)COOH)(3), 1(n); ROCONHC(CH(2)CH(2)COOH)(3), 2(n); RNHCONHC(CH(2)CH(2)COOH)(3), 3(n), where R = n-C(n)H(2n+1) and n = 13-22 carbon atoms--were assayed for their potential to serve as antimicrobial components in a topical vaginal formulation. Comparing epithelial cytotoxicities to the ability of these homologues to inhibit HIV, Neisseria gonorrhoeae, and Candida albicans provided a measure of their prophylactic/therapeutic potential. Measurements of the ability to inhibit Lactobacillus plantarum, a beneficial bacterium in the vagina, and critical micelle concentrations (CMCs), an indicator of the potential detergency of these amphiphiles, provided additional assessments of safety. Several amphiphiles from each homologous series had modest anti-HIV activity (EC(50) = 110-130 microM). Amphiphile 2(18) had the best anti-Neisseria activity (MIC =65 microM), while 1(19) and 1(21) had MICs against C. albicans of 16 and 7.7 microM, respectively. Two measures of safety showed promise as all compounds had relatively low cytotoxic activity (EC(50) = 210-940 microM) against epithelial cells and low activity against L. plantarum, 1(n), 2(n), and 3(n) had MICs490, 1300, and 940 microM, respectively. CMCs measured in aqueous triethanolamine and in aqueous potassium hydroxide showed linear dependences on chain length. As expected, the longest chain in each series had the lowest CMC-in triethanolamine: 1(21), 1500 microM; 2(22), 320 microM; 3(22), 340 microM, and in potassium hydroxide: 1(21), 130 microM; 3(22), 40 microM. The CMC in triethanolamine adjusted to pH 7.4 was 400 microM for 1(21) and 3900 microM for 3(16). The promising antifungal activity, low activity against L. plantarum, relatively high CMCs, and modest epithelial cytotoxicity in addition to their anti-Neisseria properties warrant further design studies with dendritic amphiphiles to improve their safety indices to produce suitable candidates for antimicrobial vaginal products.

GR 24 enantiomers: synthesis, NMR spectroscopy, X-ray crystallography, and separation by chiral electrokinetic capillary chromatography

Chiral discrimination of enantiomers of 2-methyl-4-(2-oxo-2,3,3a,8b-tetrahydro-4H-indeno[1,2b]furan-3-yl-iden emethoxy)but-2-en-4-olide (commonly referred to as GR 24) by three polymeric chiral surfactants (PCS) is studied by use of chiral polymeric surfactant capillary electrophoresis (CPSCE). The CPSCE results indicate that the optical configurations of valine residues on the PCS backbone affect chiral resolution and elution order of GR24 stereoisomers. The L- and D-forms of poly(sodium N-undecanoyl valinate) provide baseline separation of all four enantiomers while the DL-form separates diastereomers of GR 24 (1). A model is presented rationalizing the migration behavior and chiral resolution of 1 in CPSCE. The actual configuration of the stereogenic centers of GR 24 and 3-[(2,5-dihydro-3-methyl-2-oxo-5-furanyl)oxo]-methylene-3,3a,6,6a-tetrah ydro-2H-cyclopenta[b]furan-2-one (GR 7) is established by a concerted application of high-resolution nuclear magnetic resonance spectroscopy and X-ray crystallography.

Polyanions--a lost chance in the fight against HIV and other virus diseases?

Polyanions are known to exhibit potent antiviral activity in vitro, and may represent future therapeutic agents. This review summarizes literature reports, pertinent to anionic polymers as antiviral agents. The in vitro antiviral effects of numerous polyanionic compounds (sulphated polysaccharides, negatively charged serum albumin and milk proteins, synthetic sulphated polymers, polymerized anionic surfactants and polyphosphates) are described. This class of antiviral agent exhibits several unique properties that are not shared by other presently known antiviral agents: (i) a remarkable broad-spectrum antiviral activity against HIV-1, HIV-2 and a series of other enveloped viruses; (ii) the ability to inhibit syncytium formation between HIV-infected and normal CD4 T lymphocytes, a mechanism that drastically enhances HIV infectivity; and (iii) a low induction of viral drug-resistance. There is increasing evidence that polyanions interfere with the fusion process, a vital step in the viral replication cycle. The inhibition of virus-cell fusion appears to be the source of the antiviral activity of polyanions. In vivo, the pharmacological properties of polyanions result in a low bioavailability of the drugs to their viral targets, and hence a poor antiviral activity in vivo. It is suggested that polyanions must be used in combination with drug delivery systems in order to become therapeutically useful antiviral agents. Some drug delivery systems are briefly discussed.

Enantiomeric separations by use of polymeric surfactant electrokinetic chromatography

This review surveys the enantiomeric separation of drugs by electrokinetic chromatography using polymeric chiral surfactant pseudostationary phases. These phases have recently been shown to provide better mass transfer and increased rigidity and stability than regular micelles in micellar capillary electrophoresis. Characterization of the polymeric chiral surfactants is presented. Solution interactions of the pseudostationary phases via thermodynamics and fluorescence probe studies are evaluated. Also, case studies of enantiomeric separation of drugs using a single amino acid surfactant and the synergistic effect of the addition of gamma-cyclodextrin to the buffer is discussed. The use of dipeptide surfactants for chiral drug separations is described as well.

The HB-19 pseudopeptide 5[Kpsi(CH2N)PR]-TASP inhibits attachment of T lymophocyte- and macrophage-tropic HIV to permissive cells

The HB-19 pseudopeptide 5[Kpsi(CH2N)PR]-TASP[psi(CH2N) indicating a reduced peptide bond], which binds the cell surface-expressed nucleolin, is a potent inhibitor of HIV infection. Here, by using primary T lymphocyte cultures and an experimental cell model to monitor HIV entry, we show that HB-19 inhibits in a dose-dependent manner both T lymphocyte- and macrophage-tropic HIV isolates. Similar positively charged control pseudopeptides have no effect on HIV infection even at high concentrations. These observations, and the fact that HB-19 has no effect on SIV-mac and HIV-1 pseudotyped with VSV envelope glycoproteins, confirm the specific nature of this inhibitor against the entry process mediated by the HIV envelope glycoproteins. Finally, association of low doses of HB-19 with beta-chemokines or AZT results in an increased inhibitory effect on HIV infection. HB-19 has no inhibitory effect when added to cells a few hours after HIV entry. On the other hand, in HB-19-pretreated cells, the inhibitory effect persists for several hours, even after washing cells to remove away the unbound pseudopeptide. Under such conditions, the attachment of HIV particles to cells is inhibited as efficiently as by neutralizing monoclonal antibodies directed against the V3 loop. In view of its specific mode of action on various HIV isolates, HB-19 represents a potential anti-HIV drug.

Chiral electrokinetic chromatography using dipeptide polymeric surfactants: present state of the art

Polymeric amino acid based surfactants have been recently employed as pseudostationary phases in capillary electrophoresis. These phases are effective for chiral separation of analytes in different charge states and hydrophobicities. This review paper focuses on polymeric dipeptide surfactants. The benefits of dipeptide over single amino acid micelle polymers are shown. Some aspects of dipeptide surfactants that are presented here includes the amino acid order, effect of number and position of chiral centers, and steric factors on enantiomeric separation of chiral compounds in different charge states. In addition, the preferential site of interaction of the chiral analyte using diastereomers of polymeric dipeptide surfactants is discussed.

The anti-HIV pseudopeptide HB-19 forms a complex with the cell-surface-expressed nucleolin independent of heparan sulfate proteoglycans

The HB-19 pseudopeptide 5[Kpsi(CH(2)N)PR]-TASP, psi(CH(2)N) for reduced peptide bond, is a specific inhibitor of human immunodeficiency virus (HIV) infection in different CD4(+) cell lines and in primary T-lymphocytes and macrophages. Here, by using an experimental CD4(+) cell model to monitor HIV entry and infection, we demonstrate that HB-19 binds the cell surface and inhibits attachment of HIV particles to permissive cells. At concentrations that inhibit HIV attachment, HB-19 binds cells irreversibly, becomes complexed with the cell-surface-expressed nucleolin, and eventually results in its degradation. Accordingly, by confocal immunofluorescence microscopy, we demonstrate the drastic reduction of the cell-surface-expressed nucleolin following treatment of cells with HB-19. HIV particles can prevent the binding of HB-19 to cells and inhibit complex formation with nucleolin. Such a competition between viral particles and HB-19 is consistent with the implication of nucleolin in the process of HIV attachment to target cells. We show that another inhibitor of HIV infection, the fibroblast growth factor-2 (FGF-2) that uses cell-surface-expressed heparan sulfate proteoglycans as low affinity receptors, binds cells and blocks attachment of HIV to permissive cells. FGF-2 does not prevent the binding of HB-19 to cells and to nucleolin, and similarly HB-19 has no apparent effect on the binding of FGF-2 to the cell surface. The lack of competition between these two anti-HIV agents rules out the potential involvement of heparan sulfate proteoglycans in the mechanism of anti-HIV effect of HB-19, thus pointing out that nucleolin is its main target.

Characterization and thermodynamic studies of the interactions of two chiral polymeric surfactants with model substances: phenylthiohydantoin amino acids

Analytical ultracentrifugation is used for determination of the molecular weights and the sedimentation coefficients of poly(sodium undecanoyl-L-valinate) (PSUV) and poly(sodium undecanoyl-L-threoninate) (PSUT) at different temperatures. Plots of absorbance as a function of radius indicates that both PSUV and PSUT are highly monodispersed. A method for evaluating the partial specific volumes using density measurements is presented. The partial specific volumes of PSUV are slightly higher than those of PSUT. In addition, the temperature dependence of the retention factor in electrokinetic chromatography was used to estimate the enthalpy, the entropy, and the Gibbs free energy of the surfactant/analyte complexes. Five phenylthiohydantoin-DL-amino acids were separated and each enantiomeric pair was completely resolved. Comparison of the thermodynamic values obtained with PSUV vs PSUT using a van't Hoff relationship suggests that PSUT, with a less favorable free energy change (i.e., less negative delta (delta G)), generates a more positive entropy change, hence slightly less chiral resolution.

The V3 loop-mimicking pseudopeptide 5[Kpsi(CH2N)PR]-TASP inhibits HIV infection in primary macrophage cultures

The V3 loop-mimicking pseudopeptide 5[Kpsi(CH2N)PR]-TASP [psi(CH2N) representing a reduced peptide bond], which presents pentavalently the tripeptide Kpsi(CH2N)PR, is a potent inhibitor of HIV entry. By its capacity to bind specifically protein components on the cell surface, 5[Kpsi(CH2N)PR]-TASP blocks the attachment of virus particles to permissive CD4+ cells. Here, the inhibitory effect of 5[Kpsi(CH2N)PR]-TASP was investigated in monocyte-derived macrophages (MDMs) infected by the monocytotropic HIV-1(Ba-L) isolate. We show that 5[Kpsi(CH2N)PR]-TASP inhibits HIV-1(Ba-L) infection in a dose-dependent manner, with more than 90% inhibition at 2 microM concentration. On the other hand, the control 5[QPQ]-TASP construct and the monovalent Kpsi(CH2N)PR tripeptide have no effect even at high concentrations. Under such experimental conditions, the biotin-labeled 5[Kpsi(CH2N)PR]-TASP, but not the Kpsi(CH2N)PR construct, binds specifically to the surface of MDMs and forms a stable complex with the cell surface-expressed nucleolin, as has been demonstrated to be the case in peripheral blood mononuclear cells. Infection of MDMs by HIV-1(Ba-L) could also be inhibited by beta-chemokines RANTES and MIP-1beta. Interestingly, association of low concentrations of 5[Kpsi(CH2N)PR]-TASP and beta-chemokines results in a synergistic inhibitory effect on HIV infection compared with the effect observed with each reagent alone. The inhibitory effect of 5[Kpsi(CH2N)PR]-TASP in primary macrophage cultures point out its potential as an anti-HIV drug in cells, which are the natural viral targets.

Fractions of chemically oversulphated galactosaminoglycan sulphates inhibit three enveloped viruses: human immunodeficiency virus type 1, herpes simplex virus type 1 and human cytomegalovirus

A series of chemically oversulphated galactosaminoglycans (SO3H:COOH ratio > or = 2) were tested in vitro as antiviral agents against human immunodeficiency virus type 1 (HIV-1), the aetiological agent of AIDS, and against herpes simplex virus type 1 and human cytomegalovirus, two agents responsible for opportunistic infections in HIV-infected people. The oversulphated derivatives displayed an increase in activity ranging from one to four orders of magnitude against the three viruses, as compared to the natural parent compounds (SO3H:COOH, ratio approx. 1). The antiviral activity of these polyanions appears to be favoured by a high degree of sulphation and a high molecular mass. An oversulphated dermatan, with a SO3H:COOH ratio of 2.86 and molecular mass of 23.2 kDa, was the most potent anti-HIV-1 compound (EC50 0.04 microgram/ml). A second oversulphated dermatan, with a SO3H:COOH ratio of 2.40 and molecular mass of 25 kDa, displayed the highest activity against HSV-1 (EC50 0.01 microgram/ml). An oversulphated chondroitin, with a SO3H:COOH ratio of 2.80 and molecular mass of 17.3 kDa, was the strongest anti-HCMV agent (EC50 0.4 microgram/ml). In view of the absence of the side-effects typical of heparin-like compounds, a combination of these derivatives could have therapeutic potential.

Identification of V3 loop-binding proteins as potential receptors implicated in the binding of HIV particles to CD4(+) cells

The binding of human immunodeficiency virus (HIV) type 1 particles to CD4(+) cells could be blocked either by antibodies against the V3 loop domain of the viral external envelope glycoprotein gp120, or by the V3 loop mimicking pseudopeptide 5[Kpsi(CH2N)PR]-TASP, which forms a stable complex with a cell-surface-expressed 95-kDa protein. Here, by using an affinity matrix containing 5[Kpsi(CH2N)PR]-TASP and cytoplasmic extracts from human CEM cells, we purified three V3 loop-binding proteins of 95, 40, and 30 kDa, which after microsequencing were revealed to be as nucleolin, putative HLA class II-associated protein (PHAP) II, and PHAP I, respectively. The 95-kDa cell-surface protein was also isolated and found to be nucleolin. We show that recombinant preparations of gp120 bind the purified preparations containing the V3 loop-binding proteins with a high affinity, comparable to the binding of gp120 to soluble CD4. Such binding is inhibited either by 5[Kpsi(CH2N)PR]-TASP or antibodies against the V3 loop. Moreover, these purified preparations inhibit HIV entry into CD4(+) cells as efficiently as soluble CD4. Taken together, our results suggest that nucleolin, PHAP II, and PHAP I appear to be functional as potential receptors in the HIV binding process by virtue of their capacity to interact with the V3 loop of gp120.

Polyanion inhibitors of human immunodeficiency virus and other viruses. 6. Micelle-like anti-HIV polyanionic compounds based on a carbohydrate core

A new class of polyanionic compounds, inhibitors of human immunodeficiency virus, was obtained from radical addition of mercapto acid or mercapto ester on a perallylated carbohydrate under UV irradiation with a catalytic amount of AIBN. Unlike the polyanions that we have previously prepared by polymerization reactions, the compounds are structurally well defined. Polyanions bearing 16 carboxylate groups showed a 50% inhibitory concentration (IC50) of 0.1-4.1 micrograms/mL against HIV-1 in MT-4 cells while not being toxic to the host cells at concentrations up to 125 micrograms/mL. The most potent polyanions also proved active against human cytomegalovirus at concentrations of 1-14 micrograms/mL. No activity was observed against any of the other viruses tested (i.e., herpes simplex virus, vesicular stomatitis virus, Sindbis, Semliki forest, parainfluenza-3, Junin, Tacaribe, Coxsackie B4, polio-1, reo-1, or vaccinia virus).