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Search Results: 1 - 10 of 1042 matches for " Katrin Ehrhardt "
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The HIV-1 Rev Protein Enhances Encapsidation of Unspliced and Spliced, RRE-Containing Lentiviral Vector RNA
Bastian Grewe, Katrin Ehrhardt, Bianca Hoffmann, Maik Blissenbach, Sabine Brandt, Klaus überla
PLOS ONE , 2012, DOI: 10.1371/journal.pone.0048688
Abstract: Background During the RNA encapsidation process of human immunodeficiency virus (HIV) viral genomic, unspliced RNA (gRNA) is preferentially incorporated into assembling virions. However, a certain amount of spliced viral transcripts can also be detected in viral particles. Recently, we observed that nuclear export of HIV and lentiviral vector gRNA by Rev is required for efficient encapsidation. Since singly-spliced HIV transcripts also contain the Rev-response element (RRE), we investigated if the encapsidation efficiency of RRE-containing spliced HIV-vector transcripts is also increased by the viral Rev protein. Findings Starting with a lentiviral vector imitating the splicing pattern of HIV, we constructed vectors that express an unspliced transcript either identical in sequence to the singly-spliced or the fully-spliced RNA of the parental construct. After transfection of the different lentiviral vectors cytoplasmic and virion-associated RNA levels and vector titers were determined in the presence and absence of Rev. Rev enhanced the infectious titer of vectors containing an RRE 6 to 37-fold. Furthermore, Rev strongly increased encapsidation efficiencies of all RRE-containing transcripts up to 200-fold. However, a good correlation between encapsidation efficiency and lentiviral vector titer could only be observed for the gRNA. The infectious titer of the vector encoding the fully-spliced RNA without RRE as well as the encapsidation efficiency of all transcripts lacking the RRE was not influenced by Rev. Interestingly, the splicing process itself did not seem to interfere with packaging, since the encapsidation efficiencies of the same RNA expressed either by splicing or as an unspliced transcript did not differ significantly. Conclusions Rev-mediated nuclear export enhances the encapsidation efficiency of RRE-containing lentiviral vector RNAs independently of whether they have been spliced or not.
Direct Infection of Dendritic Cells during Chronic Viral Infection Suppresses Antiviral T Cell Proliferation and Induces IL-10 Expression in CD4 T Cells
Carmen Baca Jones, Christophe Filippi, Sowbarnika Sachithanantham, Teresa Rodriguez-Calvo, Katrin Ehrhardt, Matthias von Herrath
PLOS ONE , 2014, DOI: 10.1371/journal.pone.0090855
Abstract: Elevated levels of systemic IL-10 have been associated with several chronic viral infections, including HCV, EBV, HCMV and LCMV. In the chronic LCMV infection model, both elevated IL-10 and enhanced infection of dendritic cells (DCs) are important for viral persistence. This report highlights the relationship between enhanced viral tropism for DCs and the induction of IL-10 in CD4 T cells, which we identify as the most frequent IL-10-expressing cell type in chronic LCMV infection. Here we report that infected CD8αneg DCs express elevated IL-10, induce IL-10 expression in LCMV specific CD4 T cells, and suppress LCMV-specific T cell proliferation. DCs exposed in vivo to persistent LCMV retain the capacity to stimulate CD4 T cell proliferation but induce IL-10 production by both polyclonal and LCMV-specific CD4 T cells. Our study delineates the unique effects of direct infection versus viral exposure on DCs. Collectively these data point to enhanced infection of DCs as a key trigger of the IL-10 induction cascade resulting in maintenance of elevated IL-10 expression in CD4 T cells and inhibition of LCMV-specific CD4 and CD8 T cell proliferation.
Commentary on "Expansions for Eigenfunctions and Eigenvalues of large-n Toeplitz Matrices"
Torsten Ehrhardt
Papers in Physics , 2010, DOI: 10.4279/pip.020004
Abstract: A Commentary on the paper by L. P. Kadanoff [Pap. Phys. 2, 020003 (2010)]. Received: 29 September 2010, Accepted: 4 October 2010; Edited by: A. G. Green; DOI: 10.4279/PIP.020004
Dyson's constant in the asymptotics of the Fredholm determinant of the sine kernel
Torsten Ehrhardt
Mathematics , 2004,
Abstract: We prove that the asymptotics of the Fredholm determinant of $I-K_\alpha$, where $K_\alpha$ is the integral operator with the sine kernel $\sin(x-y)/(x-y)/\pi$ on the interval $[0,\alpha]$ is given by a formula which was conjectured by F.J. Dyson. The first and second order asymptotics as well as the higher order asymptotics except for the constant term have already been proved. In this paper we thus determine the constant term.
Dyson's constants in the asymptotics of the determinants of Wiener-Hopf-Hankel operators with the sine kernel
Torsten Ehrhardt
Mathematics , 2006, DOI: 10.1007/s00220-007-0239-x
Abstract: In this paper we are going to prove two asymptotic formulas for determinants det(I-K_s), as s goes to infinity, where K_s are the Wiener-Hopf-Hankel operators acting on L^2[0,s] with the kernels K(x-y)+K(x+y) and K(x-y)-K(x+y), respectively, and K(t):=sin(t)/(\pi*t). These formulas were conjectured by Dyson. The identification of the constant term in the asymptotics was an open problem for a long time.
Invertibility of Toeplitz + Hankel Operators and Singular Integral Operators with Flip - The case of smooth generating functions
Torsten Ehrhardt
Mathematics , 2000,
Abstract: It is well known that a Toeplitz operator is invertible if and only if its symbols admits a canonical Wiener-Hopf factorization, where the factors satisfy certain conditions. A similar result holds also for singular integral operators. More general, the dimension of the kernel and cokernel of Toeplitz or singular integral operators which are Fredholm can be expressed in terms of the partial indices of an associated Wiener-Hopf factorization problem. In this paper we establish corresponding results for Toeplitz + Hankel operators and singular integral operators with flip under the assumption that the generating functions are sufficiently smooth. We are led to a slightly different factorization problem, in which so-called characteristic pairs instead of the partial indices appear. These pairs provide the relevant information about the dimension of the kernel and cokernel and thus answer the invertibility problem.
The asymptotics a Bessel-kernel determinant which arises in Random Matrix Theory
Torsten Ehrhardt
Mathematics , 2010,
Abstract: In Random Matrix Theory the local correlations of the Laguerre and Jacobi Unitary Ensemble in the hard edge scaling limit can be described in terms of the Bessel kernel (containing a parameter $\alpha$). In particular, the so-called hard edge gap probabilities can be expressed as the Fredholm determinants of the corresponding integral operator restricted to the finite interval [0, R]. Using operator theoretic methods we are going to compute their asymptotics as R goes to infinity under certain assumption on the parameter $\alpha$.
Human Cytomegalovirus Fcγ Binding Proteins gp34 and gp68 Antagonize Fcγ Receptors I, II and III
Eugenia Corrales-Aguilar,Mirko Trilling,Katja Hunold,Manuela Fiedler,Vu Thuy Khanh Le,Henrike Reinhard,Katrin Ehrhardt,Eva Mercé-Maldonado,Enver Aliyev,Albert Zimmermann,David C. Johnson,Hartmut Hengel
PLOS Pathogens , 2014, DOI: doi/10.1371/journal.ppat.1004131
Abstract: Human cytomegalovirus (HCMV) establishes lifelong infection with recurrent episodes of virus production and shedding despite the presence of adaptive immunological memory responses including HCMV immune immunoglobulin G (IgG). Very little is known how HCMV evades from humoral and cellular IgG-dependent immune responses, the latter being executed by cells expressing surface receptors for the Fc domain of IgG (FcγRs). Remarkably, HCMV expresses the RL11-encoded gp34 and UL119-118-encoded gp68 type I transmembrane glycoproteins which bind Fcγ with nanomolar affinity. Using a newly developed FcγR activation assay, we tested if the HCMV-encoded Fcγ binding proteins (HCMV FcγRs) interfere with individual host FcγRs. In absence of gp34 or/and gp68, HCMV elicited a much stronger activation of FcγRIIIA/CD16, FcγRIIA/CD32A and FcγRI/CD64 by polyclonal HCMV-immune IgG as compared to wildtype HCMV. gp34 and gp68 co-expression culminates in the late phase of HCMV replication coinciding with the emergence of surface HCMV antigens triggering FcγRIII/CD16 responses by polyclonal HCMV-immune IgG. The gp34- and gp68-dependent inhibition of HCMV immune IgG was fully reproduced when testing the activation of primary human NK cells. Their broad antagonistic function towards FcγRIIIA, FcγRIIA and FcγRI activation was also recapitulated in a gain-of-function approach based on humanized monoclonal antibodies (trastuzumab, rituximab) and isotypes of different IgG subclasses. Surface immune-precipitation showed that both HCMV-encoded Fcγ binding proteins have the capacity to bind trastuzumab antibody-HER2 antigen complexes demonstrating simultaneous linkage of immune IgG with antigen and the HCMV inhibitors on the plasma membrane. Our studies reveal a novel strategy by which viral FcγRs can compete for immune complexes against various Fc receptors on immune cells, dampening their activation and antiviral immunity.
RNA Interference Is Responsible for Reduction of Transgene Expression after Sleeping Beauty Transposase Mediated Somatic Integration
Christina Rauschhuber, Anja Ehrhardt
PLOS ONE , 2012, DOI: 10.1371/journal.pone.0035389
Abstract: Background Integrating non-viral vectors based on transposable elements are widely used for genetically engineering mammalian cells in functional genomics and therapeutic gene transfer. For the Sleeping Beauty (SB) transposase system it was demonstrated that convergent transcription driven by the SB transposase inverted repeats (IRs) in eukaryotic cells occurs after somatic integration. This could lead to formation of double-stranded RNAs potentially presenting targets for the RNA interference (RNAi) machinery and subsequently resulting into silencing of the transgene. Therefore, we aimed at investigating transgene expression upon transposition under RNA interference knockdown conditions. Principal Findings To establish RNAi knockdown cell lines we took advantage of the P19 protein, which is derived from the tomato bushy stunt virus. P19 binds and inhibits 21 nucleotides long, small-interfering RNAs and was shown to sufficiently suppress RNAi. We found that transgene expression upon SB mediated transposition was enhanced, resulting into a 3.2-fold increased amount of colony forming units (CFU) after transposition. In contrast, if the transgene cassette is insulated from the influence of chromosomal position effects by the chicken-derived cHS4 insulating sequences or when applying the Forg Prince transposon system, that displays only negligible transcriptional activity, similar numbers of CFUs were obtained. Conclusion In summary, we provide evidence for the first time that after somatic integration transposon derived transgene expression is regulated by the endogenous RNAi machinery. In the future this finding will help to further improve the molecular design of the SB transposase vector system.
Strontium disodium hexathiodiphosphate(IV) octahydrate
Claus Ehrhardt,Mimoza Gjikaj
Acta Crystallographica Section E , 2010, DOI: 10.1107/s1600536810025316
Abstract: The crystal structure of SrNa2(P2S6)·8H2O is isotypic with that of its calcium analogue. The asymmetric unit consists of one Sr2+ cation (2 symmetry), two Na+ cations (2 and overline{1} symmetry, respectively), one-half of a centrosymmetric (P2S6)4 anion with a staggered confirmation and four water molecules. The crystal structure is built up from layers of cations and anions extending parallel to (101). Each SrO8 polyhedron is connected via edge-sharing to two NaO4S2 octahedra and to one NaO2S4 octahedron. The NaO4S2 octaedra are, in turn, connected with two (P2S6)4 anions through common corners. Adjacent layers are held together by several O—H...S hydrogen-bonding interactions.
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