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The B cell response and the B cell receptor repertoire following vaccination


Trück, Johannes. The B cell response and the B cell receptor repertoire following vaccination. 2016, University of Zurich, Faculty of Medicine.

Abstract

B cells are a key component of the adaptive immune system and mediate host defence against invading pathogens through the production of pathogen-specific antibodies. Most current vaccines are designed to stimulate the immune system to produce specific antibodies prior to natural exposure so that the immune system has adequate time to build up memory in form of high concentrations of functional serum antibody and production of memory B cells (BMEM). The generation of BMEM during an immune response is particularly important in protecting the host when serum antibody concentrations have waned, which is a common phenomenon seen following childhood vaccination. Upon re-exposure to antigen pre-existing populations of BMEM can rapidly expand and differentiate into plasma cells, which are able to secret large amounts of high affinity antibody thereby protecting the host against invading pathogens. Despite the importance of B cells in the host immune response to vaccination, there is a paucity of data regarding the assessment of the B cell response following vaccination while most vaccine studies concentrate on exploring pathogen-specific antibody concentrations in serum. Antigen-specific BMEM frequencies in peripheral blood can be measured using a cultured enzyme-linked immunospot (ELISpot) method. In one study described in this thesis, the effect of cryopreservation of peripheral blood mononuclear cells on the variability of an antigen-specific BMEM ELISpot was tested. In that work we have demonstrated the reproducibility of the cultured ELISpot assay across operators and laboratories. These findings support the use of cryopreserved samples in future studies involving the investigation of BMEM thereby facilitating the processing of clinical study samples enormously. In a second BMEM study, this technique was used to explore the potential of a zwitterionic pneumococcal polysaccharide (which has alternating positive and negative charges in each repeating unit) to induce BMEM formation in humans. In contrast to previously published studies in mice, we found that this was not possible, highlighting important differences in B cell responses between mice and humans and excluding this plain polysaccharide as an unconjugated antigen for use in children. Investigating the B cell receptor (BCR) repertoire - representing the sum of all antibodies expressed on the surface of B cells - allows a more detailed view on the B cell system globally, and also on the B cell response to stimulation such as vaccination. The latter is posiii sible by applying statistical tools to the large number of sequences that are generated by next-generation sequencing following amplification and sequencing of BCR transcripts derived from peripheral blood B cells. We have previously applied an in-house bioinformatic analysis pipeline to a number of different BCR sequencing datasets. In these studies, we demonstrated that different individuals produce common sequences in response to immunisation with polysaccharide as well as protein based vaccines. These antigen-specific sequences were then further characterised and could be tracked over time. We have also analysed BCR sequencing data derived from healthy individuals in an ’unstimulated’ state for the exploration of intra- and inter-individual variation in the BCR repertoire over time. Findings from this study showed good assay reproducibility but great fluctuations in the repertoire over time, thereby developing a framework for understanding specific B cell responses to vaccination. Taken together, results from the BCR repertoire studies have shown that it is possible to identify antigen-specific sequences following vaccination, which form the basis to apply this method as a means to identify and track other immune activation states such as infectious disease or autoimmunity

Abstract

B cells are a key component of the adaptive immune system and mediate host defence against invading pathogens through the production of pathogen-specific antibodies. Most current vaccines are designed to stimulate the immune system to produce specific antibodies prior to natural exposure so that the immune system has adequate time to build up memory in form of high concentrations of functional serum antibody and production of memory B cells (BMEM). The generation of BMEM during an immune response is particularly important in protecting the host when serum antibody concentrations have waned, which is a common phenomenon seen following childhood vaccination. Upon re-exposure to antigen pre-existing populations of BMEM can rapidly expand and differentiate into plasma cells, which are able to secret large amounts of high affinity antibody thereby protecting the host against invading pathogens. Despite the importance of B cells in the host immune response to vaccination, there is a paucity of data regarding the assessment of the B cell response following vaccination while most vaccine studies concentrate on exploring pathogen-specific antibody concentrations in serum. Antigen-specific BMEM frequencies in peripheral blood can be measured using a cultured enzyme-linked immunospot (ELISpot) method. In one study described in this thesis, the effect of cryopreservation of peripheral blood mononuclear cells on the variability of an antigen-specific BMEM ELISpot was tested. In that work we have demonstrated the reproducibility of the cultured ELISpot assay across operators and laboratories. These findings support the use of cryopreserved samples in future studies involving the investigation of BMEM thereby facilitating the processing of clinical study samples enormously. In a second BMEM study, this technique was used to explore the potential of a zwitterionic pneumococcal polysaccharide (which has alternating positive and negative charges in each repeating unit) to induce BMEM formation in humans. In contrast to previously published studies in mice, we found that this was not possible, highlighting important differences in B cell responses between mice and humans and excluding this plain polysaccharide as an unconjugated antigen for use in children. Investigating the B cell receptor (BCR) repertoire - representing the sum of all antibodies expressed on the surface of B cells - allows a more detailed view on the B cell system globally, and also on the B cell response to stimulation such as vaccination. The latter is posiii sible by applying statistical tools to the large number of sequences that are generated by next-generation sequencing following amplification and sequencing of BCR transcripts derived from peripheral blood B cells. We have previously applied an in-house bioinformatic analysis pipeline to a number of different BCR sequencing datasets. In these studies, we demonstrated that different individuals produce common sequences in response to immunisation with polysaccharide as well as protein based vaccines. These antigen-specific sequences were then further characterised and could be tracked over time. We have also analysed BCR sequencing data derived from healthy individuals in an ’unstimulated’ state for the exploration of intra- and inter-individual variation in the BCR repertoire over time. Findings from this study showed good assay reproducibility but great fluctuations in the repertoire over time, thereby developing a framework for understanding specific B cell responses to vaccination. Taken together, results from the BCR repertoire studies have shown that it is possible to identify antigen-specific sequences following vaccination, which form the basis to apply this method as a means to identify and track other immune activation states such as infectious disease or autoimmunity

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Additional indexing

Item Type:Habilitation (cumulative)
Communities & Collections:04 Faculty of Medicine > University Children's Hospital Zurich > Medical Clinic
Dewey Decimal Classification:610 Medicine & health
Language:English
Date:2016
Deposited On:26 Dec 2018 17:46
Last Modified:28 Dec 2018 15:43
OA Status:Closed

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