Soluble glycosaminoglycans Do not potentiate RANTES antiviral activity on the infection of primary macrophages by human immunodeficiency virus type 1

Myocardial extracellular matrix: an ever-changing and diverse entity

The cardiac extracellular matrix (ECM) is a complex architectural network consisting of structural and nonstructural proteins, creating strength and plasticity. The nonstructural compartment of the ECM houses a variety of proteins, which are vital for ECM plasticity, and can be divided into 3 major groups: glycoproteins, proteoglycans, and glycosaminoglycans. The common denominator for these groups is glycosylation, which refers to the decoration of proteins or lipids with sugars. This review will discuss the fundamental role of the matrix in cardiac development, homeostasis, and remodeling, from a glycobiology point of view. Glycoproteins (eg, thrombospondins, secreted protein acidic and rich in cysteine, tenascins), proteoglycans (eg, versican, syndecans, biglycan), and glycosaminoglycans (eg, hyaluronan, heparan sulfate) are upregulated on cardiac injury and regulate key processes in the remodeling myocardium such as inflammation, fibrosis, and angiogenesis. Albeit some parallels can be made regarding the processes these proteins are involved in, their specific functions are extremely diverse. In fact, under varying conditions, individual proteins can even have opposing functions, making spatiotemporal contribution of these proteins in the rearrangement of multifaceted ECM very hard to grasp. Alterations of protein characteristics by the addition of sugars may explain the immense, yet tightly regulated, variability of the remodeling cardiac matrix. Understanding the role of glycosylation in altering the ultimate function of glycoproteins, proteoglycans, and glycosaminoglycans in the myocardium may lead to the development of new biochemical structures or compounds with great therapeutic potential for patients with heart disease.

Highly potent anti-HIV-1 activity isolated from fermented Polygonum tinctorium Aiton

A water-soluble extract of fermented Polygonum tinctorium Aiton (Polygonaceae) called Sukumo, exhibited a potent inhibitory activity against HIV type 1 in vitro. The extract potently suppressed acute HIV-1 (III_B) infection in MT-4 cells with EC₅₀ values of 0.5 μg/ml but exhibited low cytotoxicity to MT-4 cells even at a high concentration (CC₅₀ > 1000 μg/ml). It also inhibited giant cell formation in co-cultures of HIV-infected cells and uninfected Molt-4 cells. Sukumo extract was found to interact with both the viral envelope glycoprotein and cellular receptors, thus blocking virus-cell binding and virus-induced syncytium formation. There was a good correlation between the extract's anti-HIV-1 activity and its inhibitory effects on HIV-1 binding. It also suppressed replication of herpes simplex virus type 1 in Vero cells with an EC₅₀ of 11.56 μg/ml. On the other hand, there was no appreciable activity against influenza A virus, poliovirus or SARS corona virus when tested at concentrations ranging from 3.2–400 μg/ml as shown by microscopic image analysis for cytopathic effect (CPE). Physico-chemical studies revealed that the anti-HIV activity in the extract was essentially maintained after boiling at 100 °C in 1N HCl or 1N NaOH, and after treatment with 100 mM NaIO₄. The inhibitory activity of the extract was also not reduced after pronase digestion. The active factor in the extract is likely to be a novel compound(s) having a polyanionic substructure and a molecular weight of 10,000–50,000.

Anti-human immunodeficiency virus activity of tau interferon in human macrophages: involvement of cellular factors and beta-chemokines

Tau interferon (IFN-tau) is a noncytotoxic type I IFN responsible for maternal recognition of the fetus in ruminants. IFN-tau inhibits human immunodeficiency virus (HIV) replication more strongly than human IFN-alpha, particularly in human monocyte-derived macrophages. In this study performed in human macrophages, IFN-tau efficiently inhibited the early steps of the biological cycle of HIV, decreasing intracellular HIV RNA and inhibiting the initiation of the reverse transcription of viral RNA into proviral DNA. Two mechanisms induced by IFN-tau treatment in macrophages may account for this inhibition: (i) the synthesis of the cellular antiviral factors such as 2',5'-oligoadenylate synthetase/RNase L and MxA protein and (ii) an increased production of MIP-1alpha, MIP-1beta, and RANTES, which are natural ligands of CCR5, the principal coreceptor of HIV on macrophages. Our results suggest that IFN-tau induces the same antiviral pathways in macrophages as other type I IFNs but without associated toxicity.

RANTES (CCL5) uses the proteoglycan CD44 as an auxiliary receptor to mediate cellular activation signals and HIV-1 enhancement

The CC-chemokine RANTES (regulated on activation normal T-cell expressed and secreted; CCL5) transduces multiple intracellular signals. Like all chemokines, it stimulates G protein-coupled receptor (GPCR) activity through interaction with its cognate chemokine receptor(s), but in addition also activates a GPCR-independent signaling pathway. Here, we show that the latter pathway is mediated by an interaction between RANTES and glycosaminoglycan chains of CD44. We provide evidence that this association, at both low, physiologically relevant, and higher, probably supraphysiologic concentrations of RANTES, induces the formation of a signaling complex composed of CD44, src kinases, and adapter molecules. This triggers the activation of the p44/42 mitogen-activated protein kinase (MAPK) pathway. By specifically reducing CD44 expression using RNA interference we were able to demonstrate that the p44/p42 MAPK activation by RANTES requires a high level of CD44 expression. As well as potently inhibiting the entry of CCR5 using HIV-1 strains, RANTES can enhance HIV-1 infectivity under certain experimental conditions. This enhancement process depends in part on the activation of p44/p42 MAPK. Here we show that silencing of CD44 in HeLa-CD4 cells prevents the activation of p44/p42 MAPK and leads to a substantial reduction in HIV-1 infectivity enhancement by RANTES.

Broad spectrum inhibition of HIV-1 infection by sulfated K5 Escherichia coli polysaccharide derivatives

OBJECTIVE

HIV-1 entry into CD4 cells represents a main target for developing novel antiretroviral agents and microbicides.

DESIGN

Sulfated derivatives of the K5 polysaccharide have a backbone structure resembling the heparin precursor, but are devoid of the anticoagulant activity. The derivatives were chemically sulfated in the N position after N-deacetylation, in the O position, or in both sites.

METHODS

HIV replication in human T cell blasts, monocyte-derived macrophages and cell lines was studied in the presence of sulfated K5 derivatives.

RESULTS

O-sulfated [K5-OS(H)] and N,O-sulfated [K5-N,OS(H)] K5 derivatives with high degree of sulfation inhibited the replication of an HIV strain using CXCR4 as entry co-receptor (X4 virus) in both cell lines and T-cell blasts. K5 derivatives also strongly inhibited the multiplication of CCR5-dependent HIV (R5 virus) in cell lines, T-cell blasts and primary monocyte-derived macrophages. Their 50% inhibitory concentration was between 0.07 and 0.46 microM, without evidence of cytotoxicity even at the maximal concentration tested (9 microM). In addition, both K5-N,OS(H) and K5-OS(H) potently inhibited the replication of several primary HIV-1 isolates in T-cell blasts, with K5-N,OS(H) being more active than K5-OS(H) on dual tropic R5X4 strains. K5 derivatives inhibited the early steps of virion attachment and/or entry.

CONCLUSIONS

Because K5 derivatives are unlikely to penetrate into cells they may represent potential topical microbicides for the prevention of sexual HIV-1 transmission.

The binding surface and affinity of monomeric and dimeric chemokine macrophage inflammatory protein 1 beta for various glycosaminoglycan disaccharides

Chemokines comprise a family of proteins that function in the immune response to recruit leukocytes to sites of infection. This recruitment is believed to be carried out by the establishment of a chemokine gradient by the binding of chemokines to sulfated polysaccharides known as glycosaminoglycans (GAGs) located on the extracellular surface of endothelial cells. In the present studies, multidimensional NMR spectroscopy was used to study the interaction of monomeric and dimeric chemokine macrophage inflammatory protein (MIP)-1 beta variants with a series of differentially sulfated disaccharides. The data define a GAG binding surface, including both basic and uncharged residues such as Arg(18), Asn(23), Val(25), Thr(44), Lys(45), Arg(46), and Ser(47). Dissociation constants determined from these NMR studies consistently show for each disaccharide that dimeric wild type MIP-1 beta binds more tightly than monomeric MIP(9). Furthermore, analysis of the binding surface suggests that participation in the dimer of residues Met(3), Gly(4), and Ser(5) may be responsible for this higher affinity. These studies also indicate that the specificity of MIP-1 beta for particular GAG disaccharides is directly related not only to the degree of disaccharide sulfation but also to the position of the sulfate moiety, with O-sulfation at position 2 of the hexuronic acid unit and position 6 of the D-glucosamine being major determinants for binding.

Involvement of integrin alphavbeta3 in the pathogenesis of human immunodeficiency virus type 1 infection in monocytes

Attachment of HIV to macrophages is a critical early event in the establishment of infection. In the present study, we demonstrate the involvement of integrin alphavbeta3 (vitronectin receptor) in HIV infection of peripheral blood monocyte-derived macrophages. Culturing monocytes in the presence of M-CSF for 3 days upregulated expression of the alphav-containing integrins, alphavbeta3 and alphavbeta5. The increase in alphavbeta3 expression was accompanied by increased HIV-1 replication by monocytes. Immunoblot analysis showed that purified HIV-gp120 protein interacted with CD4 and alphavbeta3 in immunoprecipitation experiments. Neutralizing antibodies against the alphavbeta3 integrin interfered with the coprecipitation of alphavbeta3 with an anti-gp120 antibody and substantially inhibited HIV infection of monocytes. Neutralizing antibodies against alphavbeta5 or beta1 integrins did not significantly affect HIV infection. These results indicate that HIV infection of primary monocytes requires differentiation of these cells and may involve alphavbeta3 interaction with the HIV-1 envelope protein gp120 for productive infection.

Association of chemokine-mediated block to HIV entry with coreceptor internalization

Chemokines inhibit entry of HIV into CD4(+) T cells more effectively than into macrophages or transfected adherent cells. Here, we tested whether chemokine receptor internalization could account for cell type differences in the effectiveness of chemokines. Infection of CEM T cells expressing stably transduced wild-type CCR5 was much more readily inhibited by chemokine than were transduced HOS cells. This response correlated with the efficiency of CCR5 internalization. A mutated CCR5, termed M7-CCR5, in which the Ser/Thr phosphorylation sites in the cytoplasmic tail were changed to Ala, did not internalize in response to MIP-1alpha. M7-CCR5 was expressed at slightly higher levels than wild-type on stably transduced cell lines and was somewhat more potent as an HIV-1 coreceptor. The mutated receptor mobilized intracellular Ca(2+) in response to chemokine to a level 4-fold higher than did the wild type CCR5. Unexpectedly, the receptor was desensitized as efficiently as wild type, suggesting that desensitization does not require cytoplasmic tail phosphorylation. Entry of R5 HIV-1 reporter virus into cells stably expressing M7-CCR5 was largely resistant to blocking by MIP-1alpha. As much as 80% of entry inhibition was attributed to receptor internalization. Aminooxypentane (AOP)-MIP-1alpha was able to induce a low level of M7-CCR5 internalization in HOS and to weakly inhibit HIV-1 entry. Introduction of dominant negative dynamin into HOS cells reduced the ability of chemokine to inhibit infection. The inefficiency of internalization of chemokine receptors in some cell types could allow virus to replicate in vivo in the presence of endogenous chemokine. Last, M7-CCR5 is a useful tool for discriminating coreceptor internalization from binding site masking in the evaluation of small molecule inhibitors of HIV-1 entry.

Human immunodeficiency virus type 1 entry into macrophages mediated by macropinocytosis

Whereas human immunodeficiency virus (HIV) infects various cell types by fusion at the plasma membrane, we observed a different entry route in human primary macrophages, in which macropinocytosis is active. Shortly after exposure of macrophages to HIV-1 and irrespective of viral envelope-receptor interactions, particles were visible in intracellular vesicles, which were identified as macropinosomes. Most virions appeared subsequently degraded. However, fusion leading to capsid release in the cytosol and productive infection could take place inside vesicles when particles were properly enveloped. These observations provide new insights into HIV-1 interactions with a cell target relevant to pathogenesis. They may have implications for the design of soluble inhibitors aimed at interfering with the fusion or entry processes.