Michaela Schmidtke

Friedrich-Schiller-University Jena, Jena, Thuringia, Germany

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Publications (84)205.36 Total impact

  • [Show abstract] [Hide abstract]
    ABSTRACT: With the emergence of oseltamivir-resistant influenza viruses and in view of a highly pathogenic flu pandemic, it is important to develop new anti-influenza agents. Here, the development of neuraminidase (NA) inhibitors that were designed to overcome resistance mechanisms along with unfavorable PK properties is described. Several 5-guanidino- and 5-amidino-based oseltamivir derivatives were synthesized and profiled for their anti-influenza activity and in vitro and in vivo PK properties. Amidine 6 and guanidine 7 were comparably effective against a panel of different A/H1N1 and A/H3N2 strains and also inhibited mutant A/H1N1 neuraminidase. Among different prodrug strategies pursued, a simple amidoxime ethyl ester (9) exhibited a superior PK profile with an oral bioavailability of 31% (rats), which is comparable to oseltamivir (36%). Thus, bioisosteric replacement of the 5-guanidine with an acetamidine - in the form of its N-hydroxy prodrug - successfully tackled the two key limitations of currently used NA inhibitors, as exemplified with oseltamivir.
    Journal of Medicinal Chemistry 01/2014; · 5.61 Impact Factor
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    ABSTRACT: Human cytomegalovirus (HCMV) can cause life-threatening diseases in neonates and immunocompromised patients. Due to multiple problems caused by the current available drugs development of new antiviral compounds is urgently needed. In this study we characterize the anti-HCMV spectrum and mechanism of action of the N-N '-(bis-5 nitropyrimidyl)dispirotripiperazine derivate 27 (DSTP-27).DSTP-27 exhibited strong antiviral activity against two laboratory HCMV strains with different cell tropism as well as a GCV-sensitive and GCV-resistant clinical isolate in plaque reduction assays and viral growth kinetics. Interestingly, neither infectious nor non-infectious viral particles were observed by electron microscopy. Pre-treatment of cell-free virus with DSTP-27 prevented virus infection. The results from time of addition assays where DTSP-27 was added (i) to cells before infection, (ii) during virus adsorption, or (iii) after adsorption demonstrated an inhibitory effect on early steps of the HCMV replication cycle. This observation was confirmed by immunofluorescence as well as Western blot analysis where reduced levels of the immediate early protein IE1, the processivity factor pUL44, and the tegument protein pp28 were detected. Results from attachment and penetration analyses of prechilled human embryonic lung fibroblasts revealed that virus attachment is not blocked. In addition, DSTP-27 inactivated HCMV by stable binding. Taken together, these results demonstrate that DSTP-27 blocks (i)viral penetration by interacting with the host cell and (ii) inactivates HCMV by interacting with the virus.
    Antimicrobial Agents and Chemotherapy 01/2014; · 4.57 Impact Factor
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    ABSTRACT: The emergence of new influenza viruses like the pandemic H1N1 influenza A virus in 2009 (A(H1N1)pdm09) with unpredictable difficulties in vaccine coverage and established antiviral treatment protocols emphasizes the need of new murine models to prove the activity of novel antiviral compounds in vivo. The aim of the present study was to develop a small-scale mathematical model based on easily attainable experimental data to explain differences in influenza kinetics induced by different virus strains in mice. To develop a three-dimensional ordinary differential equation model of influenza dynamics, the following variables were included: (i) viral pathogenicity (P), (ii) antiviral immune defense (D), and (iii) inflammation due to pro-inflammatory response (I). Influenza virus-induced symptoms (clinical score S) in mice provided the basis for calculations of P and I. Both, mono- and biphasic course of mild to severe influenza induced by three clinical A(H1N1)pdm09 strains and one European swine H1N2 virus were comparatively and quantitatively studied by fitting the mathematical model to the experimental data. The model hypothesizes reasons for mild and severe influenza with mono- as well as biphasic course of disease. According to modeling results, the second peak of the biphasic course of infection is caused by inflammation. The parameters (i) maximum primary pathogenicity, (ii) viral infection rate, and (iii) rate of activation of the immune system represent most important parameters that quantitatively characterize the different pattern of virus-specific influenza kinetics.
    Bio Systems 01/2014; · 1.27 Impact Factor
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    ABSTRACT: The amino acid substitution of aspartic acid to glycine in hemagglutinin (HA) in position 222 (HA-D222G) as well as HA-222D/G polymorphism of pandemic (H1N1) 2009 influenza viruses (A(H1N1)pdm09) were frequently reported in severe influenza in humans and mice. Their impact on viral pathogenicity and the course of influenza has been discussed controversially and the underlying mechanism remained unclarified. In the present study, BALB/c mice, infected with the once mouse lung- and cell-passaged A(H1N1)pdm09 isolate A/Jena/5258/09 (mpJena/5258), developed severe pneumonia. From day 2 to 3 or 4 post infection (p.i.) symptoms (body weight loss and clinical score) continuously worsened. After a short disease stagnation or even recovery phase in most mice, severity of disease further increased on days 6 and 7 p.i. Thereafter, surviving mice recovered. A 45 times higher virus titer maximum in the lung than in the trachea on day 2 p.i. and significantly higher tracheal virus titers compared to lung on day 6 p.i. indicated changes in the organ tropism during infection. Sequence analysis revealed an HA-222D/G polymorphism. HA-D222 and HA-G222 variants co-circulated in lung and trachea. Whereas, HA-D222 variant predominated in the lung, HA-G222 became the major variant in the trachea after day 4 p.i. This was accompanied by lower neutralizing antibody titers and broader receptor recognition including terminal sialic acid α-2,3-linked galactose, which is abundant on mouse trachea epithelial cells. Plaque-purified HA-G222-mpJena/5258 virus induced severe influenza with maximum symptom on day 6 p.i. These results demonstrated for the first time that HA-222D/G quasispecies of A(H1N1)pdm09 caused severe biphasic influenza because of fast viral intra-host evolution, which enabled partial antibody escape and minor changes in receptor binding.
    PLoS ONE 01/2014; 9(8):e104233. · 3.53 Impact Factor
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    ABSTRACT: Neuraminidase (NA), a key enzyme in viral replication, is the first-line drug target to combat influenza. On the basis of a shape-focused virtual screening, the roots of Glycyrrhiza glabra (licorice) were identified as plant species with an accumulation of constituents that show 3D similarities to known influenza NA inhibitors (NAIs). Phytochemical investigation revealed 12 constituents identified as (E)-1-[2,4-dihydroxy-3-(3-methyl-2-butenyl)phenyl]-3-(8-hydroxy-2,2-dimethyl-2H-1-benzopyran-6-yl)-2-propen-1-one (1), 3,4-dihydro-8,8-dimethyl-2H,8H-benzo[1,2-b:3,4-b']dipyran-3-ol (2), biochanin B (3), glabrol (4), glabrone (5), hispaglabridin B (6), licoflavone B (7), licorice glycoside B (8), licorice glycoside E (9), liquiritigenin (10), liquiritin (11), and prunin (12). Eleven of these constituents showed significant influenza virus NA inhibition in a chemiluminescence (CL)-based assay. Additional tests, including (i) a cell-based cytopathic effect inhibition assay (general antiviral activity), (ii) the evaluation of cytotoxicity, (iii) the inhibition of the NA of Clostridium perfringens (CL- and fluorescence (FL)-based assay), and (iv) the determination of self-fluorescence and quenching, provided further perspective on their anti-influenza virus potential, revealing possible assay interference problems and false-positive results. Compounds 1, 3, 5, and 6 showed antiviral activity, most likely caused by the inhibition of NA. Of these, compounds 1, 3, and 6 were highly ranked in shape-focused virtual screening.
    Journal of Natural Products 12/2013; · 3.29 Impact Factor
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    ABSTRACT: Influenza virus neuraminidase (iNA) is a homotetrameric surface protein of the influenza virus and an established target for antiviral drugs. In contrast to neuraminidases (NAs) of other biological systems (non-iNAs), enzymatic activity of iNA is only observed in a quaternary assembly and iNA needs the tetramerization to mediate enzymatic activity. Obviously, differences on a molecular level between iNA and non-iNAs are responsible for this intriguing observation. Comparison between protein structures and multiple sequence alignment allow the identification of differences in amino acid composition in crucial regions of the enzyme, such as next to the conserved D151 and the 150-loop. These differences in amino acid sequence and protein tetramerization are likely to alter the dynamics of the system. Therefore, we performed molecular dynamics simulations to investigate differences in the molecular flexibility of monomers, dimers, and tetramers of iNAs of subtype N1 (avian 2004, pandemic 1918 and pandemic 2009 iNA) and as comparison the non-iNA monomer from Clostridium perfringens. We show that conformational transitions of iNA are crucially influenced by its assembly state. The protein-protein interface induces a complex hydrogen-bonding network between the 110-helix and the 150-loop, which consequently stabilizes the structural arrangement of the binding site. Therefore, we claim that these altered dynamics are responsible for the dependence of iNA's catalytic activity on the tetrameric assembly. Only the tetramerization-induced balance between stabilization and altered local flexibility in the binding site provides the appropriate arrangement of key residues for iNA's catalytic activity.
    Journal of biomolecular structure & dynamics 11/2013; · 4.99 Impact Factor
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    ABSTRACT: Simvastatin, a cholesterol-lowering drug, is reported to have immunomodulatory properties that attenuated acute lung injury independent of their major lipid lowering effects. Based on these reports, simvastatin is expected to be used for influenza prophylaxis and treatment. The present study evaluated the efficacy of simvastatin against influenza A/PR/8/34 virus infection in a murine model. In a first study, simvastatin was administered orally. To achieve high plasma levels, intraperitoneal application was used in a second study. Survival, body weight loss, viral titers in lung and trachea, and histologic lung injury were measured. Surprisingly, treatment with simvastatin resulted in lower survival rates and in more distinct body mass loss in comparison to virus-infected control mice. Furthermore, the viral load in lungs and tracheas as well as histopathological lesions were not reduced by simvastatin. Overall, these results showed that simvastatin failed to protect mice against influenza virus infection. J. Med. Virol. © 2013 Wiley Periodicals, Inc.
    Journal of Medical Virology 08/2013; · 2.37 Impact Factor
  • Oral presentation at the Joint Symposium "Trends in natural products research" of the Phytochemical Society of Europe (PSE) and the Austrian Pharmaceutical Society (ÖPhG) at the University Centre Obergurgl/Tyrol, Austria, Book of Abstracts. Leicester: Phytochemical Society of Europe, ISBN 978-0-9565472-3-1, p. 38; 07/2013
  • Oral presentation at the Joint Symposium "Trends in natural products research" of the Phytochemical Society of Europe (PSE) and the Austrian Pharmaceutical Society (ÖPhG) at the University Centre Obergurgl/Tyrol, Austria; 07/2013
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    ABSTRACT: Recent epidemiological developments demonstrated that gene segments of swine influenza A viruses can account for antigenic changes as well as reduced drug susceptibility of pandemic influenza A viruses. This raises questions about the efficacy of preventive measures against swine influenza A viruses. Here, the protective effect of vaccination was compared with that of prophylactic Tamiflu® treatment against two Eurasian swine influenza A viruses. 11-week-old pigs were infected by aerosol nebulisation with high doses of influenza virus A/swine/Potsdam/15/1981 (H1N1/1981, heterologous challenge to H1N1 vaccine strain) and A/swine/Bakum/1832/2000 (H1N2/2000, homologous challenge to H1N2 vaccine strain) in two independent trials. In each trial (i) 10 pigs were vaccinated twice with a trivalent vaccine (RESPIPORC® FLU3; 28 and 7 days before infection), (ii) another 10 pigs received 150 mg/day of Tamiflu® for 5 days starting 12 h before infection, and (iii) 12 virus-infected pigs were left unvaccinated and untreated and served as controls. Both viruses replicated efficiently in porcine respiratory organs causing influenza with fever, dyspnoea, and pneumonia. Tamiflu® treatment as well as vaccination prevented clinical signs and significantly reduced virus shedding. Whereas after homologous challenge with H1N2/2000 no infectious virus in lung and hardly any lung inflammation were detected, the virus titre was not and the lung pathology was only partially reduced in H1N1/1981, heterologous challenged pigs. Tamiflu® application did not affect these study parameters. In conclusion, all tested preventive measures provided protection against disease. Vaccination additionally prevented virus replication and histopathological changes in the lung of homologous challenged pigs.
    PLoS ONE 01/2013; 8(4):e61597. · 3.53 Impact Factor
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    ABSTRACT: Native high molecular weight hyaluronan (HMW-HA, MW=1×10(6)g/mol) and a thermally degraded low molecular weight hyaluronan (LMW-HA, MW=1.3-1.4×10(5)g/mol) were carboxymethylated providing products with degrees of carboxymethylation (DSCM) of up to 0.8. Sulfation of resulting carboxymethyl hyaluronan (CM-HA) and hyaluronan (HA) was performed by different sulfation procedures enabling the control of the degree of sulfation (DSS) in the obtained new carboxymethyl hyaluronan sulfates (CM-HA-S) and hyaluronan sulfates (HA-S), respectively, in a range between 0.9 and 3.3. Both carboxymethylation and sulfation were found to take place preferentially at the primary hydroxyl groups of HA. The antiviral activity of these synthesized HA derivatives was tested against Herpes simplex virus type 1. Both HA-S and CM-HA-S derivatives with high DSS values of about 3.0 exhibit a strong antiherpetic activity. The CM-HA derivatives were found to be not active and an additional effect of introduced carboxymethyl groups on the antiherpetic activity of CM-HA-S derivatives was not observed. In the case of HA-S, the antiviral efficacy can be correlated with the DSS and becomes stronger with increasing DSS values.
    Carbohydrate polymers. 09/2012; 90(1):608-15.
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    ABSTRACT: Native high molecular weight hyaluronan (HMW-HA, MW = 1×106 g/mol) and a thermally degraded low molecular weight hyaluronan (LMW-HA, MW = 1.3–1.4 ×105 g/mol) were carboxymethylated providing products with degrees of carboxymethylation (DSCM) of up to 0.8. Sulfation of resulting carboxymethyl hyaluronan (CM-HA) and hyaluronan (HA) was performed by different sulfation procedures enabling the control of the degree of sulfation (DSS) in the obtained new carboxymethyl hyaluronan sulfates (CM-HAS) and hyaluronan sulfates (HA-S), respectively, in a range between 0.9 and 3.3. Both carboxymethylation and sulfation were found to take place preferentially at the primary hydroxyl groups of HA. The antiviral activity of these synthesized HA derivatives was tested against Herpes simplex virus type 1. Both HA-S and CM-HA-S derivatives with high DSS values of about 3.0 exhibit a strong antiherpetic activity. The CM-HA derivatives were found to be not active and an additional effect of introduced carboxymethyl groups on the antiherpetic activity of CM-HA-S derivatives was not observed. In the case of HA-S, the antiviral efficacy can be correlated with the DSS and becomes stronger with increasing DSS values.
    Carbohydrate Polymers 01/2012; 90:608-615. · 3.48 Impact Factor
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    ABSTRACT: The imminent threat of influenza pandemics and repeatedly reported emergence of new drug-resistant influenza virus strains demonstrate the urgent need for developing innovative and effective antiviral agents for prevention and treatment. At present, influenza neuraminidase (NA), a key enzyme in viral replication, spread, and pathogenesis, is considered to be one of the most promising targets for combating influenza. Despite the substantial medical potential of NA inhibitors (NAIs), only three of these drugs are currently on the market (zanamivir, oseltamivir, and peramivir). Moreover, sudden changes in NAI susceptibility revealed the urgent need in the discovery/identification of novel inhibitors. Nature offers an abundance of biosynthesized compounds comprising chemical scaffolds of high diversity, which present an infinite pool of chemical entities for target-oriented drug discovery in the battle against this highly contagious pathogen. This review illuminates the increasing research efforts of the past decade (2000-2011), focusing on the structure, function and druggability of influenza NA, as well as its inhibition by natural products. Following a critical discussion of publications describing some 150 secondary plant metabolites tested for their inhibitory potential against influenza NA, the impact of three different strategies to identify and develop novel NAIs is presented: (i) bioactivity screening of herbal extracts, (ii) exploitation of empirical knowledge, and (iii) computational approaches. This work addresses the latest developments in theoretical and experimental research on properties of NA that are and will be driving anti-influenza drug development now and in the near future.
    Natural Product Reports 01/2012; 29(1):11-36. · 10.18 Impact Factor
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    ABSTRACT: European swine influenza A viruses donated the matrix protein 2 as well as the neuraminidase (NA) gene to pandemic influenza A (H1N1) viruses that emerged in 2009. As a result, the latter became amantadine resistant and neuraminidase inhibitor (NAI) susceptible. These recent developments reflecting the close connection between influenza A virus infection chains in humans and pigs urge an antiviral surveillance within swine influenza A viruses. Here, NAI susceptibility of 204 serologically typed swine influenza A viruses of subtypes H1N1, H1N2, and H3N2 circulating in Germany between 1981 and 2008 was analyzed in chemiluminescence-based NA inhibition assays. Mean 50% inhibitory concentrations of oseltamivir and zanamivir indicate a good drug susceptibility of tested viruses. As found for human isolates, the oseltamivir and zanamivir susceptibility was subtype-specific. So, swine influenza A (H1N1) viruses were just as susceptible to oseltamivir as to zanamivir. In contrast, swine H1N2 and H3N2 influenza A viruses were more sensitive to oseltamivir than to zanamivir. Furthermore, reduction in plaque size and virus spread by both drugs was tested with selected H1N1 and H1N2 isolates in MDCK cells expressing similar amounts of α2.3- and α2.6-linked sialic acid receptors. Data obtained in cell culture-based assays for H1N1 isolates correlated with that from enzyme inhibition assays. But, H1N2 isolates that are additionally glycosylated at Asn158 and Asn163 near the receptor-binding site of hemagglutinin (HA) were resistant to both NAI in MDCK cells. Possibly, these additional HA glycosylations cause a misbalance between HA and NA function that hampers or abolishes NAI activity in cells.
    Medical Microbiology and Immunology 06/2011; 201(1):61-72. · 3.55 Impact Factor
  • Antiviral Research. 05/2011; 90(2):A29.
  • Antiviral Research 05/2011; 90(2). · 3.93 Impact Factor
  • Oral presentation at the 241st American Chemical Society (ACS) National Meeting & Exposition in Anaheim, California, USA; 03/2011
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    ABSTRACT: The pathogenicity of influenza A and B viruses depends on the function of influenza neuraminidase (NA). Emerging resistant influenza A viruses of subtype H1N1 increasingly challenge the effectiveness of established NA inhibitors. Recent computational studies have indicated several weak points of NA that can be exploited for rational inhibitor design to conquer this imminent threat, such as the opening of the binding pocket due to the flexibility of the 150-, 245- and 430-loops. We employed shape-focused virtual screening based on a recently discovered lead compound, katsumadain A, to identify novel promising compounds with significant inhibitory efficacy on NA and resistance-breaking capacity on oseltamivir-resistant strains. A potential binding mode of these compounds was derived employing ligand-based techniques and protein-ligand docking using representative protein conformations selected from molecular dynamics simulations. Five novel compounds were identified by virtual screening. Their IC(50) values, determined in chemiluminescence-based NA inhibition assays, are in the range of 0.18-17 µM. In particular, artocarpin exhibits high affinity toward three H1N1 oseltamivir-sensitive influenza A viruses. It also inhibits the NA of an oseltamivir-resistant H1N1 isolate.
    Future medicinal chemistry 03/2011; 3(4):437-50. · 3.31 Impact Factor
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    ABSTRACT: The cyanobacteria are known to be a rich source of metabolites with a variety of biological activities in different biological systems. In the present work, the bioactivity of aqueous and organic (methanolic and hexane) crude extracts of cyanobacteria isolated from estuarine ecosystems was studied using different bioassays. The assessment of DNA damage on the SOS gene repair region of mutant PQ37 strain of Escherichia coli was performed. Antiviral activity was evaluated against influenza virus, HRV-2, CVB3 and HSV-1 viruses using crystal violet dye uptake on HeLa, MDCK and GMK cell lines. Cytotoxicity evaluation was performed with L929 fibroblasts by MTT assay. Of a total of 18 cyanobacterial isolates studied, only the crude methanolic extract of LEGE 06078 proved to be genotoxic (IF > 1.5) in a dose-dependent manner and other four were putative candidates to induce DNA damage. Furthermore, the crude aqueous extract of LEGE 07085 showed anti- herpes type 1 activity (IC50 = 174.10 μg dry extract mL(-1)) while not presenting any cytotoxic activity against GMK cell lines. Of the 54 cyanobacterial extracts tested, only the crude methanolic and hexane ones showed impair on metabolic activity of L929 fibroblasts after long exposure (48-72 h). The inhibition of HSV-1 and the strong cytotoxicity against L929 cells observed emphasizes the importance of evaluating the impact of those estuarine cyanobacteria on aquatic ecosystem and on human health. The data also point out their potential application in HSV-1 treatment and pharmacological interest.
    Toxicology in Vitro 03/2011; 25(4):944-50. · 2.65 Impact Factor
  • Antiviral Research - ANTIVIR RES. 01/2011; 90(2).

Publication Stats

736 Citations
205.36 Total Impact Points

Institutions

  • 1995–2014
    • Friedrich-Schiller-University Jena
      • • Institute of Virology and Antiviral Therapy
      • • Institut für Ökologie
      Jena, Thuringia, Germany
  • 2013
    • IDT Biologika
      Dessau, Saxony-Anhalt, Germany
  • 2008–2012
    • University of Innsbruck
      • Institut für Pharmazie
      Innsbruck, Tyrol, Austria
  • 2011
    • National Academy of Sciences of Ukraine
      Kievo, Kyiv City, Ukraine
  • 2010
    • South-West University "Neofit Rilski"
      • Department of Chemistry
      Blagoevgrad, Oblast Blagoevgrad, Bulgaria
  • 2009
    • Technische Universität München
      München, Bavaria, Germany
  • 2006
    • Addis Ababa University
      • School of Pharmacy
      Addis Ababa, Adis Abeba Astedader, Ethiopia
  • 2001
    • Philipps-Universität Marburg
      • Institut für Immunologie
      Marburg an der Lahn, Hesse, Germany
  • 1996
    • Leibniz Institute for Natural Product Research and Infection Biology - Hans Knöll Institute
      Jena, Thuringia, Germany