Antibodies directed against AMPAR and GABA<sub>B</sub>R subunits have been implicated in forms of limbic encephalitis (LE), a disease characterised by memory loss and seizures. Patients with LE show clinical improvement with immunomodulatory treatment, suggesting that the associated antibodies are pathogenic. To explore further the AMPAR and GABA<sub>B</sub>R antibodies, an in house cell based assay (CBA) was established for screening and potential pathogenicity was explored using a series of in vitro experiments. Human embryonic kidney (HEK) cells transfected with AMPAR and GABA<sub>B</sub>R subunits and primary neuronal cultures were used to detect antibodies in patient sera and CSF. In total, 15/1361 (1.1%) AMPAR antibody positive samples and 24/1438 (1.7%) GABABR antibody positive samples were identified. The predominant antibody subclass for AMPAR and GABA<sub>B</sub>R antibodies was shown to be IgG1. Interestingly, on transfected cells, only AMPAR antibodies showed complement deposition, and therefore had the potential to activate the classical pathway of the complement cascade. Application of IgG purified from AMPAR antibody positive patients, but not GABA<sub>B</sub>R antibody positive patients caused a down regulation of the receptor from the cell surface of transfected HEK cells and primary hippocampal cultures. Electrophysiological analysis showed changes in Up state duration and spike rate in the entorhinal cortex following application of purified GABA<sub>B</sub>R antibody IgG on brain slices. These findings suggest that GABABR antibodies are having a direct short term effect on GABA<sub>B</sub>Rs, and by extension cortical networks. Finally, we attempted to study whether or not viral infection could be a trigger for antibody production to known and novel antigen targets in a cohort of Japanese encephalitis viral (JEV) samples. A JEV cohort of 44 children was screened for antibodies to neuronal surface proteins by CBA. Twenty-seven percent of patients had antibodies to known neuronal surface antigens, with NMDAR and CASPR2 as the most common antigen targets. Interestingly, screening the cohort on primary neuronal cultures revealed that 65.9% of children with JEV have neuronal surface antibodies. The identification of the novel antigen target was attempted using immunoprecipitation and mass spectrometry techniques. In total, 4 neuronal surface proteins were identified that could be potential targets in JEV patients. In summary, antibodies directed against previously described antigenic targets were explored further for pathogenic potential, and a cohort of patients with a viral infection with potential novel antigen targets was investigated.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:640008 |
| Date | January 2014 |
| Creators | Nibber, Anjan |
| Contributors | Lang, Bethan |
| Publisher | University of Oxford |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
| Source | http://ora.ox.ac.uk/objects/uuid:5d3eb5fa-9f51-4415-92bd-2d7c795aa51c |
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