OpenAccess

Untersuchungen zur Blockade zellulärer antiviraler Mechanismen durch das Hepatitis A-Virus unter besonderer Berücksichtigung der Proteinkinase R und des Transkriptionsfaktors NF-kappaB
File | Size | Format | |
---|---|---|---|
E-Diss838_Berk2.pdf | 2.67 MB | Adobe PDF | View/Open |
Other Titles: | Examinations of the inhibition of cellular antiviral mechanisms by hepatitis A virus in consideration of protein kinase R and the transcription factor NF-kappaB | Authors: | Berk, Iris | Supervisor: | Vallbracht, Angelika | 1. Expert: | Vallbracht, Angelika | 2. Expert: | Schmitz, Herbert | Abstract: | Virus infection normally induces expression and secretion of type I interferon (IFN), leading to the establishment of an antiviral state in adjacent cells. In rhesus monkey kidney cells, hepatitis A virus (HAV) suppresses induction of IFN-b on the level of transcription, even after transfection with poly(IC), a dsRNA analogon. Furthermore, HAV is able to establish a persistent infection in cell culture and to suppress apoptosis. The objectives of this work were 1) to transfer the above results into a human cell culture system and 2) to examine possible cellular targets of HAV. Human MRC-5 fibroblasts were infected with HAV, and results show that IFN-b is not induced by infection and that after poly(IC) transfection HAV actively suppresses IFN-b production (determined by plaque reduction assay). Suppression of IFN-b expression occurs on the level of mRNA, as detected by RT-PCR suggesting one or more proteins of dsRNA-dependent signalling pathways to be affected by HAV. Protein kinase R (PKR) is involved in dsRNA-induced apoptosis and furthermore, PKR has been described to be involved in the activation of NF-kB, a transcription factor participating in induction of IFN-b. Autophosphorylation is a hallmark of PKR-activation and therefore, phosphorylation of PKR on Thr-451 was analysed by immunoblotting. In HAV-infected cells, PKR-phosphorylation appeared to be generally reduced, whereas a degradation of PKR could not be detected. When cellular localization of NF-kB was examined by immunofluorescence, poly(IC)-induced nuclear translocation of NF-kB was found to be unaffected and even enhanced by HAV, excluding a role for NF-kB in HAV-mediated suppression of IFN-b. However, HAV-induced activation of anti-apoptotic NF-kB may contribute to survival of HAV-infected cells. The suppression of IFN-b and the influence on PKR, NF-kB and cell vitality may allow HAV to establish a persistent infection in cell culture and might be a prerequisite for successful replication in vivo. |
Keywords: | Hepatitis A-Virus, Interferon, PKR, NF-kappaB | Issue Date: | 17-Dec-2003 | Type: | Dissertation | URN: | urn:nbn:de:gbv:46-diss000008387 | Institution: | Universität Bremen | Faculty: | FB2 Biologie/Chemie |
Appears in Collections: | Dissertationen |
Page view(s)
20
checked on Jan 19, 2021
Download(s)
3
checked on Jan 19, 2021
Google ScholarTM
Check
Items in Media are protected by copyright, with all rights reserved, unless otherwise indicated.