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Biomedical subjects

B Oberg

Publications and source records attributed to B Oberg.

At least 145 records · Page 8Linked to original sources
PubMed1980

Inhibition of hepatitis B Dane particle DNA polymerase activity by pyrophosphate analogs.

A DNA polymerase is associated with the core of the so-called Dane particles. The probability that this is the hepatitis B viral DNA polymerase offers the possibility of preventing hepatitis B multiplication by selective inhibition of this enzyme. We have previously reported that trisodium phosphonoformate (PFA) inhibits Dane particle DNA polymerase. Fifteen compounds with structural similarity to PFA and pyrophosphate have now been tested for inhibition of hepatitis B virus DNA polymerase in an attempt to define the structural requirement for the inhibition. Active structures have two acid groups at close proximity of which at least one is a phosphono group. Phosphonoformate and hypophosphare were the two most active inhibitors. The Ki value for PFA was 7.2 microM when dTTP was used as variable substrate, and the mechanism of inhibition was non-competitive. Phosphonoformate caused rapid shut-off of the polymerase reaction, indicating that it might inhibit elongation. The efficient inhibition of hepatitis B virus DNA polymerase by PFA and its low toxicity suggest that it could be used to inhibit hepatitis B virus multiplication in vivo.

Diphosphates↗
PubMed1980

Effect of trisodium phosphonoformate and idoxuridine on experimental herpes simplex keratitis in immunized and non-immunized rabbits.

The effect of trisodium phosphonoformate (PFA) has been compared to that of idoxuridine (IDU) when applied topically in both liquid and ointment preparations on herpetic keratitis in rabbits. Trisodium phosphonoformate had a therapeutic effect but was not as effective as idoxuridine in the vehicles tested. This was seen with both herpes-immunized and non-immunized rabbits. A herpesvirus mutant inducing a PFA restant DNA polymerase was used to infect rabbit corneas. A comparison of the effect of PFA on the keratitis caused by this resistant mutant and the wild type herpesvirus indicates that the therapeutic effect of PFA on the herpes keratitis was due to an inhibition of herpesvirus DNA polymerase.

Animals↗
PubMed1980

Inhibition of cytomegalovirus late antigens by phosphonoformate.

Phosphonoformate (PFA) at a concentration of 500 muM and higher completely inhibited the replication of cytomegalovirus (CMV) in cell culture. 50% inhibition was obtained at a concentration of muM PFA. Early nuclear CMV antigens appeared uninhibited, but the formation of nuclear inclusion bodies, late cytoplasmic antigens, Fc-receptors and CPE were all inhibited by PFA. No visible cell toxicity was noted at the PFA concentrations and exposure times used.

Antigens, Viral↗
PubMed1980

Reversible inhibition of cytomegalovirus replication by phosphonoformate.

Cytomegalovirus (CMV Ad. 169)-induced late antigens are specifically inhibited by phosphonoformate (PFA). Four fresh isolates of CMV were also inhibited by PFA to varying degrees. The kinetics of CMV immediate early antigens (IEA) and early nuclear antigens (EA) produced in the presence of PFA were compared to the early phase of the replicative infection. After anticomplement immunofluorescence with anti-IEA and anti-EA, microimmunofluorometry of individual CMV-infected nuclei was performed. CMV-induced antigens had a two-wave appearance, with maxima at 6 and 24 h postinfection. The same was seen in the presence of PFA. CMV EA-containing cells persisted for more than 5 weeks in the presence of PFA, but decreased in frequency and antigen content. The inhibition of virus replication was reversible after all incubation periods assayed. After PFA release, IEA and EA appeared again in many cells, and the kinetics were similar to that of initial infection. The results suggest that the input CMV genome persists in most initially infected cells, survives PFA incubation, and is active again after PFA release. This differs from abortive CMV infections.

Animals↗
PubMed1980

Influence of cells and virus multiplicity on the inhibition of herpesviruses with acycloguanosine.

The inhibition of herpes simplex virus type 1 (HSV-1) plaque formation by acycloguanosine (ACG) was assayed in human fetal lung fibroblasts (HL), cell lines from human cervical carcinoma, rabbit cornea, and human rhabdomyosarcoma, and three green monkey kidney cell lines. The ACG concentration giving 50% plaque reduction (PR50) of HSV-1 was lowest in HL. In two green monkey kidney cell lines, HSV-1 plaque formation was relatively insensitive to ACG, with PR50 of 25 and 60 muM, respectively. In the other cells, HSV-1 showed an intermediate sensitivity to ACG. Also, HSV-2 was more sensitive to ACG in HL than in monkey kidney cells. HSV-1 plaque reduction on HL cells was studied as a function of increasing virus MOI with a constant concentration of ACG. An increased MOI decreased the sensitivity to ACG. The sensitivity of cytomegalovirus (CMV), strain Ad. 169, and four fresh CMV isolates to ACG was studied in HL cells. At low MOIs, three of the five CMV strains were somewhat sensitive to ACG, PR50 values ranging from 60 to 450 muM ACG. At high MOIs none of the virus strains were sensitive. ACG at concentrations of 200 muM or less did not significantly affect host cell DNA synthesis, as measured by 3H-thymidine incorporation. In cell culture, the inhibition of herpesviruses by ACG appears to be complex, depending on the type of virus, virus concentration, type of host cells, and condition of the cells.

Acyclovir↗
PubMed1979

The effect of pyrophosphate analogues on influenza virus RNA polymerase and influenza virus multiplication.

Analogues of pyrophosphate have been tested as inhibitors of influenza virus-RNA polymerase activity in cell-free assays. The most active compound, phosphonoformic acid (PFA), reduced the polymerase activity to 50 per cent at a concentration of 20 muM. The inhibition was dependent on the type of divalent cation present in the assay. PFA at a concentration of 400 muM also inhibited the influenza virus plaque formation by 90 per cent.

DNA-Directed RNA Polymerases↗
PubMed1979

Phosphonoformate inhibits reverse transcriptase.

The new antiviral substance phosphonoformate (PFA) has been tested in a cell-free system for its effect on reverse transcriptases from an avian retrovirus (avian myeloblastosis virus, AMV) and from mammalian retroviruses (Rauscher leukaemia virus, RMuLV; bovine leukaemia virus; baboon endogenous virus; simian sarcoma virus; visna virus). The observed inhibitory effect of PFA has been compared with that of a structurally related substance, phosphonoacetate (PAA). Phosphonoformate, at a concentration of 100 microM, reduced the activities of all the above mentioned polymerases by 90% when (rA)n.(dT)10 was used as a template/primer. The dose-response curves for AMV and RMuLV polymerases primed with (rA)n.(dT)10 showed PFA to be a 1000-fold more active than PAA; the RMuLV polymerase activity was reduced to 50% after incubation with 0.7 microM-PFA and 0.7 mM-PAA, respectively. There was no difference in PFA inhibition of virus-associated and purified reverse transcriptase activity. Results with various synthetic templates showed that both the RNA- and the DNA-dependent polymerase activities of reverse transcriptase were inhibited by PFA. The endogenous polymerase activity of AMV was inhibited to 50% at 100 microM-PFA, while PAA had no effect. The PFA inhibition was dependent on whether Mg2+ or Mn2+ was used as divalent cation in the assay. Phosphonoformate arrested DNA synthesis immediately after being added to the assay system. The mechanism of inhibition of the AMV polymerase was non-competitive with respect to substrate and template and the apparent inhibition constants were 16 microM and 9 microM, respectively.

Animals↗
PubMed1979

Trisodium phosphonoformate inhibits hepatitis B Dane particle DNA polymerase.

Evidence available indicates that the so-called Dane particles are the hepatitis virus. A DNA polymerase is associated with the core of these particles. The probability that this is the viral DNA polymerase offers the possibility of preventing hepatitis B multiplication by selective inhibition of this enzyme. This investigation reports that trisodium phosphonoformate (PFA) at low concentrations but not phosphonoacetate acid (PAA) inhitits Dane particle associated DNA polymerase.

Formates↗
PubMed1979

Characteristics of herpesvirus mutants resistant to phosphonoformate and phosphonoacetate.

Mutants of herpes simplex virus type 1, resistant to phosphonoformate (PFA) and phosphonoacetate (PAA), have been selected in cell culture. The PFA-resistant mutant (HSV-PFA(r)) and the PAA-resistant mutant (HSV-PAA(r)) were also resistant to PAA and PFA, respectively. This cross-resistance indicates that PFA and PAA interact at the same site. The HSV-PFA(r) had a decreased susceptibility to vidarabine, but no difference in sensitivity to idoxuridine (5-iodo-2'-deoxyuridine) was observed when compared to the wild type. The induced deoxyribonucleic acid polymerases isolated from cells infected with HSV-PFA(r) and HSV-PAA(r) were both cross-resistant to inhibition by PFA and PAA. No increased resistance to vidarabine triphosphate could be observed, but the susceptibility to inhibition by pyrophosphate was about two times lower. None of the mutants showed any increased temperature sensitivity

Antiviral Agents↗
PubMed1978

Trisodium phosphonoformate, a new antiviral compound.

Trisodium phosphonoformate selectively inhibits cell-free DNA polymerase activity induced by herpesvirus. The new inhibitor has an antiviral effect on herpes simplex virus types 1 and 2, pseudorables virus, and infectious bovine rhinotracheitis virus in cell culture. It has a good therapeutic activity against cutaneous herpes simplex virus infection in guinea pigs.

Animals↗
PubMed1978

Comparison of the therapeutic effects of five antiviral agents on cutaneous herpesvirus infection in guinea pigs.

Cutaneous herpesvirus infection of guinea pigs has been evaluated as a model for testing antiviral compounds. Six infected sites on each animal can be used independently for local treatment. The severity of the infection has been graded in a score system. The cumulative scores during infection and the time to healing can be used to determine antiviral effects. The effects of adenine arabinoside, cytosine arabinoside, iododeoxyuridine, ribavirin and phosphonoacetic acid on the cutaneous infection was compared. Phosphonoacetic acid was the only compound with a good therapeutic activity against herpesvirus infection, causing a reduction of both the cumulative score and the time to healing. Phosphonoacetic acid was skin irritating at 2 per cent, but at 1 per cent, which still had a good therapeutic activity, skin irritation was seen only occasionally.

Animals↗
PubMed1978

Reversible inhibition of cellular metabolism by ribavirin.

The broad spectrum antiviral drug ribavirin (Virazole, 1-beta-d-ribofuranosyl-1,2,4-triazole-3-carboxamide) inhibits cellular macromolecular synthesis as well as cell division in eucaryotic cells. The concentration and time dependence have been studied. One-hour treatment with 25 muM ribavirin or 18 h with 2 muM inhibited the deoxyribonucleic acid synthesis to 50%. Higher concentrations of ribavirin were required to obtain a similar inhibition of ribonucleic acid and protein synthesis. This effect on cell metabolism and cell division can be reversed by removing the drug from the cells.

Cell Division↗
PubMed1978

Therapeutic effect of trisodium phosphonoformate on cutaneous herpesvirus infection in guinea pigs.

When applied topically, trisodium phosphonoformate (PFA) displayed activity against established cutaneous herpesvirus infections in guinea pigs similar to that exhibited by the closely related phosphonoacetic acid (PAA); however, unlike PAA, PFA was not locally skin irritating. The therapeutic benefits of topical application of PFA were clearly evident when application was delayed for 48 h after virus inoculation, at which time lesions were well developed. The therapeutic effect was dependent on the concentration of PFA and the duration of treatment. PFA exhibited significant activity against established infections when administered intraperitoneally, although it was less effective via this systemic route than when applied topically.

Animals↗
PubMed1978

Purification and characterization of an early protein (E14K) from adenovirus type 2-infected cells.

One adenovirus type 2 (Ad2) early protein, with an apparent molecular weight of 14,000 in sodium dodecyl sulfate-polyacrylamide gels (E14K), was purified to homogeneity. Purification involved fractionation of cytoplasmic extracts, precipitation at low pH, and DEAE-cellulose, phosphocellulose, and hydroxylapatite chromatography. The yield was around 12 microgram of purified protein per 10(9) HeLa cells. The two Ad2 DNA binding proteins with molecular weights of 75,000 and 45,000 (E75K and E45K) were purified by the same procedure. Tryptic peptide analyses indicated that the E14K protein is unrelated to the DNA binding proteins. The purified E14K protein has a high content of basic amino acids and a sedimentation coefficient of 5.5S in the native state, corresponding to a molecular weight of around 95,000. Pulse-chase experiments suggest that the E14K polypeptide is a primary translation product. Immunoprecipitation with a monospecific antiserum against the E14K protein revealed that it is exclusively localized in the cytoplasm of infected cells. E14K started to be synthesized at 2 hpostinfection, with a maximal rate of synthesis at 4 to 6 h postinfection. Immunoprecipitation of cell extracts from four different Ad2-transformed hamster embryo cell lines revealed that only one (Ad2HE4) of them expresses this protein. The adenovirus-simian virus 40 hybrid virus (Ad2ND1) does not express this protein, suggesting that the gene for the E14K protein is located in the part of the Ad2 genome which is deleted in this hybrid virus.

Adenoviruses, Human↗
PubMed1977

Inhibition of influenza virus ribonucleic acid polymerase by ribavirin triphosphate.

Ribavirin 5'-triphosphate (RTP), derived from the broad-spectrum antiviral compound ribavirin (Virazole), can selectively inhibit influenza virus ribonucleic acid polymerase in a cell-free assay. Ribavirin and its 5'-monophosphate have no effect on the polymerase. The inhibition is competitive with respect to adenosine 5'-triphosphate and guanosine 5'-triphosphate. RTP also inhibits ApG- and GpC-stimulated influenza virus ribonucleic acid polymerase. Since ribavirin is phosphorylated in the cell, the inhibition of influenza multiplication in the cell may also be caused by RTP.

DNA-Directed RNA Polymerases↗
PubMed1977

In vitro translation with adenovirus polyribosomes.

Polyribosomes isolated from adenovirus type 2 (Ad2)-infected HeLa cells late in productive infection can be used for translation in cell-free systems. At least eight viral polypeptides are synthesized, including the precursors to virion polypeptides VI and VII. Separation of polyribosomes by zonal rate centrifugation followed by translation in a cell-free system reveals a correlation between the sizes of the polyribosomes and the polypeptides synthesized. The cell-free extracts incorporate amino acid linearly for only 10 min and show little or no capacity to reinitiate protein synthesis. The elongation efficiency measured as the number of amino acids incorporated per ribosome in 20 min is low, ranging from 10 to 100. The maximum chain elongation rate is estimated to be 10 to 20 amino acids per min. The limited elongation has been used to assess the relative concentration of mRNA's engaged in translation.

Adenoviruses, Human↗