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42 results on '"Kraus, Günter"'

3. Selective killing of human immunodeficiency virus infected cells by non-nucleoside reverse transcriptase inhibitor-induced activation of HIV protease

Author

Smeulders Liesbeth, Keuleers Inge, Anders Maria, Jochmans Dirk, Kräusslich Hans-Georg, Kraus Günter, and Müller Barbara

Subjects
Immunologic diseases. Allergy, RC581-607
Abstract

Abstract Background Current antiretroviral therapy against human immunodeficiency virus (HIV-1) reduces viral load and thereby prevents viral spread, but it cannot eradicate proviral genomes from infected cells. Cells in immunological sanctuaries as well as cells producing low levels of virus apparently contribute to a reservoir that maintains HIV persistence in the presence of highly active antiretroviral therapy. Thus, accelerated elimination of virus producing cells may represent a complementary strategy to control HIV infection. Here we sought to exploit HIV protease (PR) related cytotoxicity in order to develop a strategy for drug induced killing of HIV producing cells. PR processes the viral Gag and Gag-Pol polyproteins during virus maturation, but is also implicated in killing of virus producing cells through off-target cleavage of host proteins. It has been observed previously that micromolar concentrations of certain non-nucleoside reverse transcriptase inhibitors (NNRTIs) can stimulate intracellular PR activity, presumably by enhancing Gag-Pol dimerization. Results Using a newly developed cell-based assay we compared the degree of PR activation displayed by various NNRTIs. We identified inhibitors showing higher potency with respect to PR activation than previously described for NNRTIs, with the most potent compounds resulting in ~2-fold increase of the Gag processing signal at 250 nM. The degree of enhancement of intracellular Gag processing correlated with the compound's ability to enhance RT dimerization in a mammalian two-hybrid assay. Compounds were analyzed for their potential to mediate specific killing of chronically infected MT-4 cells. Levels of cytotoxicity on HIV infected cells determined for the different NNRTIs corresponded to the relative degree of drug induced intracellular PR activation, with CC50 values ranging from ~0.3 μM to above the tested concentration range (10 μM). Specific cytotoxicity was reverted by addition of PR inhibitors. Two of the most active compounds, VRX-480773 and GW-678248, were also tested in primary human cells and mediated cytotoxicity on HIV-1 infected peripheral blood mononuclear cells. Conclusion These data present proof of concept for targeted drug induced elimination of HIV producing cells. While NNRTIs themselves may not be sufficiently potent for therapeutic application, the results provide a basis for the development of drugs exploiting this mechanism of action.

Published
2010
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23. Hide-and-Seek: The Challenge of Viral Persistence in HIV-1 Infection.

Author

Geeraert, Luc, Kraus, Günter, and Pomerantz, Roger J.

Subjects
*HIGHLY active antiretroviral therapy, *HIV infections, *HIV, *ANTIRETROVIRAL agents, *IMMUNOLOGY
Abstract

The success of highly active antiretroviral therapy (HAART) for HIV-1 infection has sparked interest in mechanisms by which the virus can persist despite effectively suppressive therapy. Latent HIV-1 reservoirs established early during infection not only prevent sterilizing immunity but also represent a major obstacle to virus eradication. When HIV-1 gains a foothold in the immunologic memory or in certain inaccessible compartments of the human body, it can- not be easily purged by HAART and is able to replenish systemic infection on treatment interruption. Because latently infected cells are indistinguishable from uninfected cells, deliberate activation of latent infection combined with intensified HAART seems to be the best strategy to combat latent infection. Initial hypothesis-driven clinical trials did not achieve their ultimate goal, although they provided valuable insight for the design of future eradication protocols. A more detailed understanding of the basic mechanisms underlying the establishment and long-term maintenance of HIV-1 reservoirs will be critical in developing new eradication approaches. [ABSTRACT FROM AUTHOR]

Published
2008
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26. Rapid and specific detection of the Mycobacterium tuberculosiscomplex using fluorogenic probes andreal-time PCR

Author

Kraus, Günter, Cleary, Timothy, Miller, Nancimae, Seivright, Rachel, Young, Andrea K., Spruill, Gina, and Hnatyszyn, H.James

Abstract

A rapid and sensitive strategy for the specific identification of Mycobacterium tuberculosis(TB) was designed and evaluated using crude mycobacterial lysates. The speed of real-time polymerase chain reaction (PCR) was combined with the sensitivity of fluorogenic probes to confirm the presence of mycobacteria as well as specifically identify the presence of members of the mycobacteria tuberculosis complex (MTC) in a single-tube assay. Oligonucleotides were designed to amplify the internal transcribed spacer (ITS) from several mycobacterial species. Specific fluorogenic probes were included in the PCR reaction for the identification of TB as well as Mycobacterium boviaand Mycobacterium africanumin bacterial lysates. The combination of TB-specific fluorogenic probes with real-time PCR formed an approach determined to be fast (less than 40 min), sensitive (less than 800 copies of DNA) and reliable for the specific detection of the MTC. Our data demonstrate the use of real-time PCR and fluorogenic probes in a rapid and sensitive assay to distinguish members of the MTC from other mycobacterial species.

Published
2001
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27. Intracellular Immunization of Rhesus CD34+Hematopoietic Progenitor Cells With a Hairpin Ribozyme Protects T Cells and Macrophages From Simian Immunodeficiency Virus Infection

Author

Rosenzweig, Michael, Marks, Douglas F., Hempel, Donna, Heusch, Marina, Kraus, Günter, Wong-Staal, Flossie, and Johnson, R. Paul

Abstract

Evaluation of candidate genes for stem cell gene therapy for acquired immunodeficiency syndrome (AIDS) has been limited by the difficulty of supporting in vitro T-cell differentiation of genetically modified hematopoietic progenitor cells. Using a novel thymic stromal culture technique, we evaluated the ability of a hairpin ribozyme specific for simian immunodeficiency virus (SIV) and human immunodeficiency virus type 2 (HIV-2) to inhibit viral replication in T lymphocytes derived from transduced CD34+progenitor cells. Retroviral transduction of rhesus macaque CD34+progenitor cells with a retroviral vector (p9456t) encoding the SIV-specific ribozyme and the selectable marker neomycin phosphotransferase in the presence of bone marrow stroma and in the absence of exogenous cytokines resulted in efficient transduction of both colony-forming units and long-term culture-initiating cells, with transduction efficiencies ranging between 21% and 56%. After transduction, CD34+cells were cultured on rhesus thymic stromal culture (to support in vitro differentiation of T cells) or in the presence of cytokines (to support differentiation of macrophage-like cells). After expansion and selection with the neomycin analog G418, cells derived from transduced progenitor cells were challenged with SIV. CD4+T cells derived from CD34+hematopoietic cells transduced with the ribozyme vector p9456t were highly resistant to challenge with SIV, exhibiting up to a 500-fold decrease in SIV replication, even after high multiplicities of infection. Macrophages derived from CD34+cells transduced with the 9456 ribozyme exhibited a comparable level of inhibition of SIV replication. These results show that a hairpin ribozyme introduced into CD34+hematopoietic progenitor cells can retain the ability to inhibit AIDS virus replication after T-cell differentiation and support the feasibility of intracellular immunization of hematopoietic stem cells against infection with HIV and SIV. Protection of multiple hematopoietic lineages with the SIV-specific ribozyme should permit analysis of stem cell gene therapy for AIDS in the SIV/macaque model.

Published
1997
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28. AIDS.

Author

Kurth, Reinhard, Kraus, Günter, Werner, Albrecht, Hartung, Susanne, Centner, Peter, Baier, Michael, Norley, Stephen, and Löwer, Johannes

Published
1988

42. New non-viral method for gene transfer into primary cells

Author

Gresch, Oliver, Engel, Felix B., Nesic, Dobrila, Tran, Thi Thai, England, Hazel M., Hickman, Emma S., Körner, Ida, Gan, Li, Chen, Sylvia, Castro-Obregon, Susana, Hammermann, Rainer, Wolf, Jürgen, Müller-Hartmann, Herbert, Nix, Michael, Siebenkotten, Gregor, Kraus, Günter, and Lun, Klaus

Subjects
*GENETIC transformation, *THERAPEUTICS, *GENETIC research, *CELL lines
Abstract

The availability of genetically altered cells is an essential prerequisite for many scientific and therapeutic applications including functional genomics, drug development, and gene therapy. Unfortunately, the efficient gene transfer into primary cells is still problematic. In contrast to transfections of most cell lines, which can be successfully performed using a variety of methods, the introduction of foreign DNA into primary cells requires a careful selection of gene transfer techniques. Whereas viral strategies are time consuming and involve safety risks, non-viral methods proved to be inefficient for most primary cell types. The Nucleofector technology is a novel gene transfer technique designed for primary cells and hard-to-transfect cell lines. This non-viral gene transfer method is based on a cell type specific combination of electrical parameters and solutions. In this report, we show efficient transfer of DNA expression vectors and siRNA oligonucleotides into a variety of primary cell types from different species utilizing the Nucleofector technology, including human B-CLL cells, human CD34+ cells, human lymphocytes, rat cardiomyocytes, human, porcine, and bovine chondrocytes, and rat neurons. [Copyright &y& Elsevier]

Published
2004
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