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Biomedical subjects

R Snoeck

Publications and source records attributed to R Snoeck.

At least 145 records · Page 8Linked to original sources
PubMed1991

9-[(2RS)-3-fluoro-2-phosphonylmethoxypropyl] derivatives of purines: a class of highly selective antiretroviral agents in vitro and in vivo.

A new class of compounds, 9-[(2RS)-3-fluoro-2-phosphonylmethoxypropyl] [(RS)-FPMP] derivatives of purines, is described that has selective activity against a broad spectrum of retroviruses [including human immunodeficiency virus type 1 (HIV-1) and type 2 (HIV-2)] but not other RNA or DNA viruses. This activity spectrum is completely different from that of the parental compounds, 9-[(2S)-3-hydroxy-2-phosphonylmethoxypropyl] [(S)-HPMP] derivatives of purines, which are active against a broad range of DNA viruses. The racemic (RS)-FPMP derivatives of adenine and 2,6-diaminopurine, termed (RS)-FPMPA and (RS)-FPMPDAP, respectively, are markedly more selective as in vitro antiretroviral agents than their 9-(2-phosphonylmethoxyethyl) (PME) counterparts, PMEA and PMEDAP. Also, (RS)-FPMPA and (RS)-FPMPDAP have a substantially higher therapeutic index in mice in inhibiting Moloney murine sarcoma virus-induced tumor formation and associated death and are markedly less inhibitory to human bone marrow cells than PMEA and PMEDAP. The diphosphate derivative of (RS)-FPMPA [(RS)-FPMPApp] is a potent and selective inhibitor of HIV-1 reverse transcriptase but not of HSV-1 DNA polymerase or DNA polymerase alpha. (RS)-FPMPApp, akin to PMEA diphosphate (PMEApp), acts as a DNA chain terminator. The DNA chain-terminating properties of PMEApp and (RS)-FPMPApp seem to be a prerequisite for acyclic nucleoside phosphonates to exhibit antiretrovirus (i.e., anti-HIV) activity.

Adenine↗
PubMed1991

Comparative activity of selected antiviral compounds against clinical isolates of human cytomegalovirus.

Seventeen fresh clinical isolates of human cytomegalovirus (HCMV) were examined for their in vitro susceptibility to different potential anti-HCMV drugs, including a series of acyclic nucleoside phosphonate analogues as well as the reference compounds ganciclovir, foscarnet and acyclovir. Three sulfated polysaccharides (heparin, dextran sulfate and pentosan polysulfate) known for their ability to inhibit adsorption of enveloped viruses to the cells were also included in these comparative tests. Of the reference compounds, ganciclovir was the most potent. However, it was about five-fold less potent than the phosphonate derivative (s)-1-(3-hydroxy-2-phosphonylmethoxypropyl)cytosine (HPMPC) and its cyclic form (cHPMPC). All test compounds, including the sulfated polysaccharides, were as active against the clinical isolates as they were against the laboratory strains of HCMV. Furthermore, the choice of the cell line (HEL or MRC-5) did not influence the anti-HCMV activity of the compounds.

Antiviral Agents↗
PubMed1991

Sensitive, reproducible and convenient fluorometric assay for the in vitro evaluation of anti-cytomegalovirus agents.

Fluorescein diacetate (FDA), a non-fluorescent diacetyl fluorescein ester that becomes fluorescent upon hydrolysis by cytoplasmic esterases, permitted the easy distinction by fluorometry between non-infected and human cytomegalovirus (CMV)-infected HEL cell cultures. As a result of enhanced cytoplasmic esterase activity after CMV infection, FDA-derived fluorescence intensity was brighter for infected than non-infected HEL cells. A similar increase in fluorescence intensity was observed after loading the cells with Indo-1/AM, a non-fluorescent ester of Indo-1 that becomes fluorescent upon cleavage by cytoplasmic esterases. The 50% effective concentrations of a number of anti-CMV agents as determined by the fluorometric assay were very similar to those obtained by the conventional and more time-consuming microscopic evaluation. The fluorometric assay appears very suitable for an automated evaluation of anti-CMV compounds, and also allows rapid determination of the cytotoxicity of potential antiviral compounds.

Acyclovir↗
PubMed1991

Antiviral activity of anti-cytomegalovirus agents (HPMPC, HPMPA) assessed by a flow cytometric method and DNA hybridization technique.

Phosphonylmethoxyalkylpurines and -pyrimidines, particularly (S)-1-(3-hydroxy-2-phosphonylmethoxypropyl)cytosine (HPMPC) and (S)-9-(3-hydroxy-2-phosphonylmethoxypropyl)adenine (HPMPA) and their cyclic forms (cHPMPC, cHPMPA) and the 3-deaza analogue of HPMPA (HPMPc3A) are selective and potent inhibitors of human cytomegalovirus (CMV) replication in vitro. Their anti-CMV activity has been monitored by flow cytometry and DNA hybridization. The anti-CMV agent ganciclovir [9-(1,3-dihydroxy-2-propoxymethyl)guanine (DHPG)] was included as a reference compound. From the flow cytometric assays, HPMPC and HPMPA were the most active compounds, with an EC50 (50% effective concentration) of approximately 0.6 microM. The EC50 values obtained by DNA hybridization ranged from 0.05 microM (HPMPC) to 0.74 microM (DHPG). Selectivity indexes, calculated as the ratio of the 50% inhibitory concentration (CC50) for cell growth or [methyl-3H]-thymidine incorporation to the EC50 for virus replication were highest for HPMPC and its cyclic derivative (cHPMPC). The flow cytometry and DNA hybridization assays thus confirm the results obtained by the classic plaque assay. They allow a quantitative estimation of the anti-CMV potency of the test compounds.

Adenine↗
PubMed1991

Particular characteristics of the anti-human cytomegalovirus activity of (S)-1-(3-hydroxy-2-phosphonylmethoxypropyl)cytosine (HPMPC) in vitro.

The acyclic nucleoside phosphonate analogue (S)-1-[3-hydroxy-2-phosphonylmethoxypropyl]cytosine (HPMPC) is a potent and selective inhibitor of human cytomegalovirus (HCMV) replication and DNA synthesis. Unlike 9-(1,3-dihydroxy-2-propoxymethyl)guanine (DHPG), HPMPC inhibits HCMV replication in cell cultures which have been treated with the compound before infection. Upon short-pulse treatment of HCMV-infected cells with HPMPC, a long-lasting antiviral response is obtained. The antiviral activity of HPMPC, unlike the antiviral activity of other cytosine derivatives (i.e. Ara-C, FIAC), is not readily reversed by 2'-deoxycytidine or cytidine. Neutral and alkaline sucrose gradient analysis of HCMV DNA isolated from HPMPC-treated HCMV-infected cell cultures revealed that HPMPC does not cause (detectable) single- or double-strand breakage of HCMV DNA.

Animals↗
PubMed1991

Synthesis and antiviral activity of 5-heteroaryl-substituted 2'-deoxyuridines.

The synthesis of 5-heteroaryl-substituted 2'-deoxyuridines is described. The heteroaromatics were obtained from three different 5-substituted 2'-deoxyuridines. Cycloaddition reaction of nitrile oxides on the 5-ethynyl derivative 1 gave the isoxazoles 4a-e. The thiazole derivatives 14a-c were obtained from the 5-thiocarboxamide 11, while 5-pyrrol-1-yl-2'-deoxyuridine (17) could be synthesized directly from 5-amino-2'-deoxyuridine. The compounds were evaluated for antiviral activity. Selective activity against herpes simplex virus type 1 (HSV-1) and varicella zoster virus (VZV) was noted for 5-(3-bromoisoxazol-5-yl)-2'-deoxyuridine (4c). The compound was inactive against herpes simplex virus type 2, cytomegalovirus, and thymidine kinase (TK)-deficient mutants of HSV-1 and VZV, which indicates that, most likely, its antiviral activity depends on phosphorylation by the virus-specified TK.

Animals↗
PubMed1991

5-(5-Bromothien-2-yl)-2'-deoxyuridine and 5-(5-chlorothien-2-yl)-2'-deoxyuridine are equipotent to (E)-5-(2-bromovinyl)-2'-deoxyuridine in the inhibition of herpes simplex virus type I replication.

2'-Deoxyuridines with a five-membered heterocyclic substituent in the 5-position were synthesized by palladium-catalyzed coupling reactions of 5-iodo-2'-deoxyuridine with the activated heteroaromatics. Further modification of the compound with the 5-thien-2-yl substituent gave 5-(5-bromothien-2-yl)-2'-deoxyuridine and 5-(5-chlorothienyl-2-yl)-2'-deoxyuridine. Both compounds show potent and selective activity against herpes simplex virus type 1 and varicella-zoster virus.

Antiviral Agents↗
PubMed1991

Antiviral activities of 5-ethynyl-1-beta-D-ribofuranosylimidazole-4- carboxamide and related compounds.

A series of novel compounds, 5-alkynyl-1-beta-D-ribofuranosylimidazole-4- carboxamides, have been identified as broad-spectrum antiviral agents. 5-Ethynyl-1-beta-D-ribofuranosylimidazole-4- carboxamide (EICAR), the most potent congener of the group, showed antiviral potency about 10- to 100-fold greater than that of ribavirin. Similar in spectrum to ribavirin, EICAR was particularly active (50% inhibitory concentration, 0.2 to 4 micrograms/ml) against poxviruses (vaccinia virus), togaviruses (Sindbis and Semliki forest viruses), arenaviruses (Junin and Tacaribe viruses), reoviruses (reovirus type 1), orthomyxoviruses (influenza A and B viruses), and paramyxoviruses (parainfluenza virus type 3, measles virus, subacute sclerosing panencephalitis virus, and respiratory syncytial virus). EICAR was also cytostatic for rapidly growing cells (50% inhibitory concentration, 0.2 to 0.9 microgram/ml). EICAR inhibited vaccinia virus tail lesion formation at doses that were not toxic to the host. EICAR is a candidate antiviral drug for the treatment of pox-, toga-, arena-, reo-, orthomyxo, and paramyxovirus infections.

Adenosylhomocysteinase↗
PubMed1991

Prevention of CMV-induced myelosuppression by anti-CMV antibodies: an in vitro model.

Pathogenesis of cytomegalovirus (CMV)-induced myelosuppression is not clearly understood and could be related to a direct toxic effect on the marrow progenitors and/or an alteration of the marrow environment. Myeloid progenitors (granulocyte-macrophage colony-forming units, CFU-GM) were not affected by incubation with increasing titers of CMV (10-10(5) plaque-forming units [pfu]/ml) during 2-6 h. By contrast, using the blast colony-forming cell (Bl-CFC) assay, we confirmed that CMV induced myelosuppression through an alteration of the marrow-derived stromal layer. Using this experimental model, we compared the capacity of nonspecific human immunoglobulins (IgG), specific polyclonal anti-CMV IgG, and a human monoclonal anti-CMV IgG to prevent the myelosuppressive effect of 10(4) pfu/ml of CMV. Specific anti-CMV IgG (polyclonal or monoclonal) at the concentration of 10 micrograms/ml were able to prevent the CMV-induced myelosuppressive effect, whereas nonspecific human IgG was not effective in this model. Our results suggest that 1) CMV-induced myelosuppression is related to an alteration of the marrow microenvironment, 2) specific monoclonal and polyclonal anti-CMV IgG prevent this myelosuppressive effect in vitro, and 3) human monoclonal anti-CMV IgG could be useful in vivo in the immunoprophylaxis of CMV infections.

Antibodies, Monoclonal↗
PubMed1990

Production of human monoclonal IgG antibodies reacting with cytomegalovirus (CMV).

A human monoclonal antibody (MoAb) reacting with cytomegalovirus (CMV) has been produced using somatic cell hybridization between Epstein-Barr virus (EBV) infected B lymphocytes and a human-mouse heteromyeloma cell line (SHM-D33). The hybrids were selected in HAT medium containing 5 x 10(-7) ouabain. The median level of Ig production was 5 (0.1-20) micrograms/10(6) cells/day. One selected hybridoma (IB-8E9H5) has been maintained in continuous culture for more than 30 months with a stable IgG2, lambda production. Molecular hybridization using EBV-specific probes demonstrate that our hybrids have lost the IR-1 EBV sequence during fusion. Unexpectedly, these blotting experiments revealed the presence of multiple EBNA-1 sequences dispersed among the genomic DNA of the SHM-D33 cell line. Screening for anti-CMV specificity was performed by ELISA and confirmed by immunofluorescence staining. Thus far, three CMV reference strains and 14 local strains are stained by the MoAb as early as 3 h after CMV infection of human fibroblasts, apparently through the recognition of a nuclear viral antigen of 67 kDa. In conclusion, this technique permits (a) the removal of the EBV genome contained in the lymphoblastoid parental cell line and (b) the production of human anti-CMV MoAb with potential applications in the prevention of life threatening CMV infections.

Antibodies, Monoclonal↗
PubMed1990

Inhibitory effects of potent inhibitors of human immunodeficiency virus and cytomegalovirus on the growth of human granulocyte-macrophage progenitor cells in vitro.

Phosphonoformate, ganciclovir, zidovudine and the novel acyclic nucleotide analogues (S)-9-(3-hydroxy-2-phosphonylmethoxypropyl)adenine [(S)-HPMPA] and (S)-1-(3-hydroxy-2-phosphonylmethoxypropyl)cytosine [(S)-HPMPC] were evaluated for their inhibitory effect on colony forming unit formation by human granulocyte-macrophage progenitor cells (obtained from 11 healthy volunteers) in vitro. The 50% inhibitory dose of zidovudine, (S)-HPMPA, (S)-HPMPC, ganciclovir and phosphonoformate were 10.61, 16.55, 80.88, 41.02 and 668.64 microM, respectively, when the median-effect principle was applied. The bone marrow toxicity of zidovudine used at a low concentration (3.74 microM) was significantly decreased if the drug was combined with (S)-HPMPA, (S)-HPMPC or ganciclovir. If used at higher concentrations (74.90 microM), zidovudine showed increased myelotoxicity in the presence of (S)-HPMPA and ganciclovir, but not (S)-HPMPC.

Adenine↗
PubMed1990

Selective inhibition of human cytomegalovirus DNA synthesis by (S)-1-(3-hydroxy-2-phosphonylmethoxypropyl)cytosine [(S)-HPMPC] and 9-(1,3-dihydroxy-2-propoxymethyl)guanine (DHPG).

The novel acyclic nucleoside phosphonate, (S)-1-(3-hydroxy-2-phosphonylmethoxypropyl)cytosine [(S)-HPMPC], is a potent and selective inhibitor of human cytomegalovirus (CMV) replication in cell culture. (S)-HPMPC inhibits CMV DNA synthesis in a concentration-dependent manner within the concentration range of 0.04-4 micrograms/ml. At 4 micrograms/ml, viral DNA synthesis is completely suppressed. (S)-HPMPC proved more inhibitory to CMV replication and CMV DNA synthesis than 9-(1,3-dihydroxy-2-propoxymethyl)guanine (DHPG, ganciclovir), the current drug of choice for the treatment of CMV infections. Both compounds affected cell proliferation and cellular DNA synthesis only at a concentration that was 100- to 500-fold higher than the antivirally effective concentrations. In accord with the postulated target (viral DNA synthesis) for its antiviral action, (S)-HPMPC did not prevent immediate early antigen expression in CMV-infected cells. A limited exposure time (as short as 6 hr postinfection) of the CMV-infected cells to (S)-HPMPC sufficed to afford a pronounced and prolonged inhibition of viral DNA synthesis and virus replication. This gives (S)-HPMPC a definite advantage over DHPG, which only afforded a weak and transient inhibition of CMV DNA synthesis and virus replication after it had been exposed to the cells for a short exposure time. The long-lasting antiviral action of (S)-HPMPC is a unique property that opens new therapeutic modalities for the treatment of virus infections.

Antiviral Agents↗
PubMed1990

Novel sulfated polysaccharides: dissociation of anti-human immunodeficiency virus activity from antithrombin activity.

Novel sulfated polysaccharides, sulfated bacterial glycosaminoglycan (Org 31581) and chemically degraded heparin (Org 31733), have proved to be potent and selective inhibitors of human immunodeficiency virus (HIV) in vitro. Their 50% inhibitory concentrations for HIV type 1 (HIV-1) in MT-4 cells were 0.67 and 0.52 micrograms/ml, respectively. These values are comparable to those obtained for dextran sulfate and standard heparin (0.39 and 0.89 micrograms/ml, respectively). Org 31581 and Org 31733 showed much less antithrombin activity than did dextran sulfate and standard heparin. These results indicate that the anti-HIV activity of sulfated polysaccharides can be dissociated from their antithrombin activity. Org 31581 and Org 31733 were equally inhibitory to HIV-2 and HIV-1 and were also inhibitory to the replication of human cytomegalovirus. Syncytium formation, induced by cocultivation of MOLT-4 (clone 8) cells with chronically HIV-1-infected HuT 78 cells, was also inhibited by Org 31581. As previously demonstrated with dextran sulfate and heparin, both Org 31581 and Org 31733 blocked virus adsorption to the host cells. These compounds offer great promise as candidate drugs for the chemotherapy of HIV infections.

Blood Coagulation↗
PubMed1989

Detection of immediate early, early and late antigens of human cytomegalovirus by flow cytometry.

The development of selective inhibitors of human cytomegalovirus (CMV) should lead to a better understanding of the mode of replication of CMV. A flow cytometric method was developed to monitor the expression of CMV antigens in CMV-infected human embryonic lung fibroblasts. The procedure is based on an indirect immunofluorescence assay using monoclonal antibodies directed against CMV-specific (immediate early, early, late) antigens and goat anti-murine IgG labeled with fluorescein isothiocyanate. Flow cytometric analysis clearly distinguished between the uninfected and infected cell population. There was a time-dependent appearance of CMV-specific antigens and a close correlation between the multiplicity of infection and the ratio of infected to uninfected cells. The method allows an accurate determination of the percentage of CMV-infected cells in the whole cell population and of the time of appearance of the viral antigens.

Antibodies, Monoclonal↗
PubMed1989

[Prevention of bacterial infections using ciprofloxacin in granulocytopenic patients with cancer].

The optimal approach to reduce bacterial infections in granulocytopenic patients is still controversial. Recently, fluoroquinolones have been developed and real progress has been achieved in the prevention of Gram negative bacilli septicemia. This study reports our experience with ciprofloxacin and shows the excellent tolerance of ciprofloxacin by our patients as well as promising data for the reduction of Gram negative bacilli infection. However, practical modalities to prevent infection caused by Gram positive cocci remain to be defined.

Adolescent↗
PubMed1988

Nosocomial bacteremia caused by Bacillus species.

During a six year period, 11 cases of bacteremia caused by Bacillus spp. were observed corresponding to 1% of all bacteremic episodes in our hospital. Most patients had cancer as underlying disease. All cases of positive blood cultures were associated with a clinical syndrome compatible with sepsis including high fever. None of the subsequent deaths could be related to the bacteremia caused by Bacillus spp. Four of eight cases of Bacillus subtilis bacteremia were associated with the absorption of an oral preparation containing Bacillus subtilis spores, which was administered empirically in some units of the hospital to reduce what was considered to be tube-feeding related diarrhea.

Adult↗
PubMed1988

Rapid and automated tetrazolium-based colorimetric assay for the detection of anti-HIV compounds.

A rapid, sensitive and automated assay procedure was developed for the in vitro evaluation of anti-HIV agents. An HTLV-I transformed T4-cell line, MT-4, which was previously shown by Koyanagi et al. (1985) to be highly susceptible to, and permissive for, HIV infection, served as the target cell line. Inhibition of the HIV-induced cytopathic effect was used as the end point. The viability of both HIV- and mock-infected cells was assessed spectrophotometrically via the in situ reduction of 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT). The procedure was optimized as to make optimal use of multichannel pipettes, microprocessor-controlled dispensing and optical density reading. The absorbance ratio of the mock-infected control to the HIV-infected samples was about 20. This allowed an accurate determination of the 50% effective doses, as demonstrated for 3'-azido-2',3'-dideoxythymidine (AZT), 2',3'-dideoxycytidine (ddCyd), dextran sulfate and heparin. The technique significantly reduced labor time as compared to the trypan blue exclusion method, and permits the evaluation of large numbers of compounds for their anti-HIV activity.

Acquired Immunodeficiency Syndrome↗