Dokument: Analysis of activating Fc gamma receptors and IgG subclasses in the mouse model of cytomegalovirus infection
| Titel: | Analysis of activating Fc gamma receptors and IgG subclasses in the mouse model of cytomegalovirus infection | |||||||
| URL für Lesezeichen: | https://docserv.uni-duesseldorf.de/servlets/DocumentServlet?id=41132 | |||||||
| URN (NBN): | urn:nbn:de:hbz:061-20180411-101158-9 | |||||||
| Kollektion: | Dissertationen | |||||||
| Sprache: | Englisch | |||||||
| Dokumententyp: | Wissenschaftliche Abschlussarbeiten » Dissertation | |||||||
| Medientyp: | Text | |||||||
| Autor: | M.Sc. Ehrhardt, Katrin [Autor] | |||||||
| Dateien: |
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| Beitragende: | Prof. Dr. med. Hengel, Hartmut [Gutachter] Prof. Dr. Hegemann, Johannes H. [Gutachter] | |||||||
| Dewey Dezimal-Klassifikation: | 500 Naturwissenschaften und Mathematik » 570 Biowissenschaften; Biologie | |||||||
| Beschreibung: | Herpesviral infections are lifelong persistent with phases of latency and recurrence. Human cytomegalovirus (HCMV) causes morbidity and mortality in immuno-compromised patients and after congenital transmission. In the latter situation, no approved therapeutic options exist. The adminis-tration of intravenous IgG (IVIG) containing CMV specific antibodies showed varying results. However, the IVIG preparations and their mode of action are not well characterized. Besides neutralization, IgGs exert diverse effector functions by the activation of Fc gamma receptor (FcgRs) via their constant Fc part. Recent studies demonstrated the crucial impact of FcgRs for the antiviral immune response against virus infections including HIV and influenza. To define the role of FcgRs and IgG subclasses in CMV infection and to provide proof of concept, the mouse model of CMV (MCMV) was utilized. In mice, five IgG subclasses, three activating FcgRs, and one inhibitory FcgR exist. Mice deficient in the expression of all activating FcgRs (FcRg-KO) displayed a higher and prolonged MCMV replication in the salivary glands (SG), an organ important for horizontal transmission of the virus. Furthermore, FcRg-KO mice displayed reduced numbers of NK cells (14 dpi) and macrophage (28 dpi) in the SG during MCMV infection. This result suggests the involvement of FcgRs in the phase of primary MCMV infection. Mice lacking one of the activating FcgRs controlled the virus comparable to control mice suggesting redundant roles for the activating FcgRs. To dissect further the relative importance of FcgRs in MCMV infection, future investigation of FcgR double deficient mice and / or a recurrent infection model is required. In addition, the optimization of therapeutic IgG was systematically approached focusing on FcgR dependent effector functions of non-neutralizing IgG antibodies. To this end, a set of recombinant subclasses switched IgGs and a recombinant MCMV efficiently expressing the ectopic cognate antigen (human CD8) were constructed. A reporter cell based assay was established to analyse and compare FcgR activation capabilities of mouse IgG in vitro. The predictive value of this in vitro FcgR activation assay was demonstrated when analysing influenza A virus (IVA) non-neutralizing IgG monoclonal antibodies specific for the M2e antigen. Their FcgR-mediated protection against lethal IAV disease in vivo correlated very well with the reporter cell data (cooperation with X. Saelens, Ghent). The in vitro FcgR activation capabilities of the IgG subclass switch variants were assessed using hCD8 expressing target cells revealing a unique IgG subclass dependent activation pattern for each of the FcgRs. IgG2a was the most potent subclass clearly differing from IgG2c which had been suggested to be broadly similar to IgG2a. IgG2c was surprisingly weak in FcgRIII activation, while only slightly less potent or comparable in activating the other FcgRs. Because most laboratory mouse strains only possess IgG2a or IgG2c, this finding is of general interest when evaluating FcgR dependent IgG effector functions in different transgenic mouse models. Next, the IgG switch variants were produced in different cell lines (mouse myeloma P3X63Ag8.653, human HEK293T, hamster CHO) associated with a differential composition of their Fc glycan at position Asn297. The pattern of FcgR activation by the distinct subclasses changed modestly for HEK293T but drastically for CHO compared to the myeloma derived recombinant antibodies. Some subclasses, e.g. IgG1, were more affected than others, e.g. IgG2a. Therefore, the subclass and Fc glycan composition affect the FcgR activation capabilities of IgG antibodies. When comparing hCD8 transduced with MCMV infected cells, the IgG subclass hierarchy for the activation of respective FcgRs was not altered but the overall magnitude of activation was greatly diminished. This inhibition is likely caused by MCMV-encoded FcgRs like m138, which antagonize host FcgRs. In the next step, the relative protective effect of the IgG switch variants and their glycan make-up will be assessed during MCMV hCD8 infection of mice. | |||||||
| Lizenz: |  Urheberrechtsschutz | |||||||
| Fachbereich / Einrichtung: | Medizinische Fakultät » Institute » Institut für Virologie | |||||||
| Dokument erstellt am: | 11.04.2018 | |||||||
| Dateien geändert am: | 11.04.2018 | |||||||
| Promotionsantrag am: | 21.11.2016 | |||||||
| Datum der Promotion: | 25.01.2017 |
