Idiotypes and allotypes revisited - disentangling the B cell enigma in multiple sclerosis

B cells, an important player in our adaptive immune system, can recognize innumerable foreign structures (antigens). This capability occurs after a mix of random and purpose-drive changes in their unique B-cell receptors. In our research we are focusing on how these receptors potentially can induce and/or maintain inflammation in multiple sclerosis. We have focus on ways to identify such receptors. We assumed that 1) the B cell receptors had to be properly chopped up by enzymes within the B cells. 2) The properly chopped fragments had to be presented to the adaptive immune (T cells), and 3) the T cells had to recognize these fragments as "foreign", like any antigen from bacteria/virus, meaning they should not be tolerant. In collaboration with bioinformaticians from USA, we found that nearly half (42%) of the most frequently occurring B cell receptors in the spinal fluid of MS patients contained at least one idiotope meeting our three prerequisites using the models. The results and approach in full may be read in Frontiers in Immunology. To confirm these findings we have pursued two potential tracks. First, we have analyzed how B cell receptors may be degraded by cells. We utilized biotherapeutics that are very similar to B cell receptors and investigated how these are degraded by key enzymes, and identified important mechanisms of degradation for generation of antigens, as postulated in 1). These mechanisms can be somewhat predicted by the models described above, which may further be utilized to understand the degradation on a general level. The results of this study were recently published in International Journal of Molecular Sciences. Further on, with help from the models described above, we have designed experiments in order to verify the predicted stimulatory fragments really are triggering immune responses. We had such fragments synthesized artificially in order to test them on cells from the MS patients. In all nine tested MS patients, we identified T cell responses towards predicted immunogenic fragments, and the results were published in Frontiers in Immunology. The results were jointly presented in the PhD-thesis ?B cells in Multiple Sclerosis ? on idiotopes and antigen presentation? by Rune A. Høglund, published after a successful dissertation June 2020. In addition to our main hypothesis, we have also worked on related neuroimmunological subjects. In 2018 we published on how the MS therapeutic dimethyl fumarate (Tecfidera®) influences B cell composition in blood and spinal fluid of patients. And just recently we published a learning case on a disease resembling multiple sclerosis, name Anti-MOG encephalomyelitis in the Journal of the Norwegian Medical Association (Tidsskriftet).

Vår forventning ved prosjektstart var at prosjektet ville øke forsrtåelsen av sykdomsmekanismen ved MS. Konkret forventet vi at vi ved hjelp av bioinformatisk prediksjonsanalyse kombinert med in-vitro eksperimenter ville kunne kartlegge om MS-pasienter har et omfattende repertoir av T- og B-celler som er i stand til å stimulere hverandre gjensidig, og som har potensial til å drive inflammasjone ved MS. Vi har oppnådd dette målet, gjennom å kartlegge i hvilken grad immunglobuliner fra spinalvæsken til MS-pasienter fordøyes av enzymer som ghør at de kan presenteres på HLA-molekyler, og at disse HLA/peptidkompleksene kan gjenkjennes av pasientenes egen T-celler. Resultatene av prosjektet har også vist hvordan terapeutiske monoklonale antistoffer kan stimulere immunsystemet.

Multiple sclerosis (MS) is a leading cause of neurological disability among young adults, particuarly among women. Recent theraputic approaches are restricted by limited effect and/or severe adverse events related to immunosuppression (opportunistic infections) or secondary autoimmunity (thyroiditis, nephritis and thrombocytopenia) caused by paradoxic activation of autoreactive B cells. More selective immunotherapy is therefore needed. Clonal expansion of IgG-secreting B cells is characteristic for MS, but it has so far not been possible to pinpoint their target antigens. Recent observations in our lab suggest that B cells in the cerebrospinal fluid (CSF) of MS patients could be selected and activated by non-conventional mechanisms: First, the hypervariable regions(idiotypes) of their secreted IgG carry mutations that can be recognized as immunological non-self by CD4 T cells. Second, IgG-secreting B cells from the CSF of MS patients seem to be G1m allotype restricted. Whereas previous studies have been hampered by methodological constraints, high throughput sequencing of IGVH transcriptomes and T cell receptor repertoires now allows a detailed and unbiased analysis of the immune responses in MS at a molecular and clonal level. We will combine high throughput sequencing of the immune repertoires, bioinformatic analysis, ex vivo experiments and immunohistochemistry of brain tissue to study if the requirements for non-conventional B cell activation in the cerebrospinal fluid and brain of MS patients are present, and describe the phenotypes of T- and B cells participating in this process. This work will be conducted at Akershus University Hospital and Oslo University Hospital, With contributions from the Universities of Oslo, Jena, and Ferrara, and from Adaptive Biotechnologies in Seattle and Eigen Bio in M