E. De Clercq

Bio: E. De Clercq is an academic researcher from Rega Institute for Medical Research. The author has contributed to research in topics: Virus & Deoxyuridine. The author has an hindex of 90, co-authored 774 publications receiving 30296 citations. Previous affiliations of E. De Clercq include Cardiff University & National Institutes of Health.

AMD3100, a small molecule inhibitor of HIV-1 entry via the CXCR4 co-receptor

Abstract: The bicyclam AMD3100 (formula weight 830) blocks HIV-1 entry and membrane fusion via the CXCR4 co-receptor, but not via CCR5. AMD3100 prevents monoclonal antibody 12G5 from binding to CXCR4, but has no effect on binding of monoclonal antibody 2D7 to CCR5. It also inhibits binding of the CXC-chemokine, SDF-1alpha, to CXCR4 and subsequent signal transduction, but does not itself cause signaling and has no effect on RANTES signaling via CCR5. Thus, AMD3100 prevents CXCR4 functioning as both a HIV-1 co-receptor and a CXC-chemokine receptor. Development of small molecule inhibitors of HIV-1 entry is feasible.

Sulfated polysaccharides are potent and selective inhibitors of various enveloped viruses, including herpes simplex virus, cytomegalovirus, vesicular stomatitis virus, and human immunodeficiency virus.

Abstract: Several sulfated polysaccharides (dextran sulfate, pentosan polysulfate, fucoidan, and carrageenans) proved to be potent inhibitors for herpes simplex virus, human cytomegalovirus, vesicular stomatitis virus, Sindbis virus, and human immunodeficiency virus. They were moderately inhibitory to vaccinia virus but not inhibitory to adenovirus, coxsackievirus, poliovirus, parainfluenza virus, and reovirus. These results indicate that, with the exception of parainfluenza virus, enveloped viruses are specifically susceptible to the inhibitory activity of sulfated polysaccharides.

Sulfated Polysaccharides Extracted from Sea Algae as Potential Antiviral Drugs

Abstract: The inhibitory effects of polyanionic substances on the replication of herpes simplex virus (HSV) and other viruses were reported almost four decades ago. However, these observations did not generate much interest, because the antiviral action of the compounds was considered to be largely nonspecific. Shortly after the identification of human immunodeficiency virus (HIV) as the causative agent of the acquired immune deficiency syndrome (AIDS) in 1984, heparin and other sulfated polysaccharides were found to be potent and selective inhibitors of HIV 1 replication in cell culture. Since 1988, the activity spectrum of the sulfated polysaccharides has been shown to extend to various enveloped viruses, including viruses that emerge as opportunistic pathogens (e.g., herpes simplex virus [HSV] and cytomegalovirus [CMV]) in immunosuppressed (e.g., AIDS) patients. As potential anti-HIV drug candidates, sulfated polysaccharides offer a number of promising features. They are able to block HIV replication in cell culture at concentrations as low as 0.1 to 0.01 mu g ml(-1) without toxicity to the host cells at concentrations up to 2.5 mg ml(-1). We noted that some polysulfates show a differential inhibitory activity against different HIV strains, suggesting that marked differences exist in the tar get molecules with which polysulfates interact, They not only inhibit the cytopathic effect of HIV, but also prevent HIV induced syncytium (giant cell) formation. Furthermore, experiments carried out with dextran sulfate samples of increasing molecular weight and with sulfated cyclodextrins of different degrees of sulfation have shown that antiviral activity increases with increasing molecular weight and degree of sulfation. A sugar backbone is not strictly needed for the anti-HIV activity of polysulfates because sulfated polymers composed of a carbon-carbon backbone have also proved to be highly efficient anti-HIV agents in vitro. Other, yet to be defined, structural features may also play an important role. Sulfated polysaccharides may act synergistically with other anti-HIV drugs (e.g., azidothymidine [AZT]). They are known to lead very slowly to virus drug resistance development and they show activity against HIV mutants that have become resistant to reverse transcriptase inhibitors, such as AZT, tetrahydro-imidazo [4,5,1-jk] [1,4] benzodiazepin 2 (1H) thione (TIBO) and others. From studies on their mechanism of action we concluded that polysulfates exert their anti-HIV activity by shielding off the positively charged sites in the V3 loop of the viral envelope glycoprotein (gp120). The V3 loop is necessary for virus attachment to cell surface heparan sulfate, a primary binding site, before more specific binding occurs to the CD4 receptor of CD4(+) cells. This general mechanism also explains the broad antiviral activity of polysulfates against enveloped viruses. Variations in the viral envelope glycoprotein region may result in differences in the susceptibility of different enveloped viruses to compounds that interact with their envelope glycoproteins. The efficacy of polysulfates in the therapy and/or prophylaxis of retroviral infections and opportunistic infections remains to be demonstrated both in animal models and humans. It is important to consider not only treatment of patients who are already infected with HIV, but also prophylaxis and protection from HIV and/or other virus infections. Because (i) sexual transmission is responsible for the large majority of HIV infections worldwide; (ii) this transmission is mostly mediated via mononuclear cells that infect epithelial cells of the genital tract; and because (iii) polysulfates effectively inhibit cell-cell adhesion, polysulfates may be considered as potentially effective in a vaginal formulation to protect against HIV infection. (C) 1997 Elsevier Science Inc.

Multidrug-resistance protein 5 is a multispecific organic anion transporter able to transport nucleotide analogs

Abstract: Two prominent members of the ATP-binding cassette superfamily of transmembrane proteins, multidrug resistance 1 (MDR1) P-glycoprotein and multidrug resistance protein 1 (MRP1), can mediate the cellular extrusion of xenobiotics and (anticancer) drugs from normal and tumor cells. The MRP subfamily consists of at least six members, and here we report the functional characterization of human MRP5. We found resistance against the thiopurine anticancer drugs, 6-mercaptopurine (6-MP) and thioguanine, and the anti-HIV drug 9-(2-phosphonylmethoxyethyl)adenine (PMEA) in MRP5-transfected cells. This resistance is due to an increased extrusion of PMEA and 6-thioinosine monophosphate from the cells that overproduce MRP5. In polarized Madin–Darby canine kidney II (MDCKII) cells transfected with an MRP5 cDNA construct, MRP5 is routed to the basolateral membrane and these cells transport S-(2,4-dinitrophenyl)glutathione and glutathione preferentially toward the basal compartment. Inhibitors of organic anion transport inhibit transport mediated by MRP5. We speculate that MRP5 might play a role in some cases of unexplained resistance to thiopurines in acute lymphoblastic leukemia and/or to antiretroviral nucleoside analogs in HIV-infected patients.

Mechanism of inhibitory effect of dextran sulfate and heparin on replication of human immunodeficiency virus in vitro.

Abstract: The sulfated polysaccharides dextran sulfate and heparin have proved to be potent and selective inhibitors of human immunodeficiency virus type 1 (HIV-1) in vitro. Dextran sulfate (Mr 5000) and heparin (Mr 15,000) completely protected MT-4 cells against HIV-1-induced cytopathogenicity at a concentration of 25 micrograms/ml. Their 50% inhibitory concentrations were 9.1 micrograms/ml (dextran sulfate) and 7.0 micrograms/ml (heparin), respectively. No toxicity for the host cells was observed with these compounds at a concentration of 625 micrograms/ml. The anti-HIV-1 activity of heparins of various molecular weights correlated well with their anticoagulant activity. On the other hand, with dextran sulfates of low molecular weight (5000, 8000) a significant inhibitory effect on HIV-1 was achieved at a concentration that was not markedly inhibitory to the blood coagulation process. Dextran sulfate and heparin were not inhibitory to HIV-1 reverse transcriptase unless they were used at concentrations in excess of those that inhibited HIV-1 replication. They were highly effective against HIV-1 replication even when present only during the 2-hr virus adsorption period. Studies using radiolabeled HIV-1 virions indicated that dextran sulfate and heparin inhibit virus adsorption to the host cells.

Plant Products as Antimicrobial Agents

Abstract: The use of and search for drugs and dietary supplements derived from plants have accelerated in recent years. Ethnopharmacologists, botanists, microbiologists, and natural-products chemists are combing the Earth for phytochemicals and “leads” which could be developed for treatment of infectious diseases. While 25 to 50% of current pharmaceuticals are derived from plants, none are used as antimicrobials. Traditional healers have long used plants to prevent or cure infectious conditions; Western medicine is trying to duplicate their successes. Plants are rich in a wide variety of secondary metabolites, such as tannins, terpenoids, alkaloids, and flavonoids, which have been found in vitro to have antimicrobial properties. This review attempts to summarize the current status of botanical screening efforts, as well as in vivo studies of their effectiveness and toxicity. The structure and antimicrobial properties of phytochemicals are also addressed. Since many of these compounds are currently available as unregulated botanical preparations and their use by the public is increasing rapidly, clinicians need to consider the consequences of patients self-medicating with these preparations.

Interleukin-10 and the interleukin-10 receptor.

Abstract: Interleukin-10 (IL-10), first recognized for its ability to inhibit activation and effector function of T cells, monocytes, and macrophages, is a multifunctional cytokine with diverse effects on most hemopoietic cell types. The principal routine function of IL-10 appears to be to limit and ultimately terminate inflammatory responses. In addition to these activities, IL-10 regulates growth and/or differentiation of B cells, NK cells, cytotoxic and helper T cells, mast cells, granulocytes, dendritic cells, keratinocytes, and endothelial cells. IL-10 plays a key role in differentiation and function of a newly appreciated type of T cell, the T regulatory cell, which may figure prominently in control of immune responses and tolerance in vivo. Uniquely among hemopoietic cytokines, IL-10 has closely related homologs in several virus genomes, which testify to its crucial role in regulating immune and inflammatory responses. This review highlights findings that have advanced our understanding of IL-10 and its receptor, as well as its in vivo function in health and disease.

Multidrug resistance in cancer: role of ATP–dependent transporters

Abstract: Chemotherapeutics are the most effective treatment for metastatic tumours. However, the ability of cancer cells to become simultaneously resistant to different drugs--a trait known as multidrug resistance--remains a significant impediment to successful chemotherapy. Three decades of multidrug-resistance research have identified a myriad of ways in which cancer cells can elude chemotherapy, and it has become apparent that resistance exists against every effective drug, even our newest agents. Therefore, the ability to predict and circumvent drug resistance is likely to improve chemotherapy.

Viral dynamics in human immunodeficiency virus type 1 infection

Abstract: The dynamics of HIV-1 replication in vivo are largely unknown yet they are critical to our understanding of disease pathogenesis. Experimental drugs that are potent inhibitors of viral replication can be used to show that the composite lifespan of plasma virus and virus-producing cells is remarkably short (half-life approximately 2 days). Almost complete replacement of wild-type virus in plasma by drug-resistant variants occurs after fourteen days, indicating that HIV-1 viraemia is sustained primarily by a dynamic process involving continuous rounds of de novo virus infection and replication and rapid cell turnover.

Interleukin-6 and the acute phase response

Abstract: systemic reaction characterized by fever, leukocytosis, increase in erythrocyte sedimentation rate, increases in Leucocytosis secretion of ACTH and glucocorticoids, activation of Complement activat complement and clotting cascades, decreases in serum levels of iron and zinc, a negative nitrogen balance, and by dramatic changes in the concentration of some plasma ,l' proteins. These proteins are named acute phase proteins. i