Glycans as Master Switches of B Cell Activity in Autoimmunity

Project Information

GlycanSwitch

Grant agreement ID: 101071386

DOI

10.3030/101071386

EC signature date 14 December 2022

Start date 1 January 2023

End date 31 December 2028

Funded under

• European Research Council (ERC)

Total cost

€ 9 997 500,00

EU contribution

€ 9 997 500,00

Coordinated by

ACADEMISCH ZIEKENHUIS LEIDEN
Netherlands

Periodic Reporting for period 2 - GlycanSwitch (Glycans as Master Switches of B Cell Activity in Autoimmunity)

Reporting period: 2024-07-01 to 2025-12-31

Summary of the context and overall objectives of the project

Autoimmune diseases including rheumatoid arthritis (RA) are often disabling disorders a life-long negative impact on patients’ quality of life. Mechanisms underlying the induction of the harmful autoimmune responses responsible for disease are still largely unknown. Protein glycosylation is an essential regulatory mechanism in the immune system. We recently demonstrated that N-glycosylation of the variable region (Fab) of the autoantibodies specific for RA, is a hallmark of disease development and progression. We have demonstrated that autoantibodies acquire these Fab glycosylation signatures already many years before disease onset and that the presence of these glycans is a risk factor for development of RA. In this project, we address the exciting hypothesis that Fab glycosylation at the level of the B cell receptor is a key molecular switch promoting the selection, activation and proliferation of autoreactive B cells leading to the concomitant breach of immunotolerance and subsequent disease onset. Within GlycanSwitch, we will map the Fab glycome of various types of RA autoantibodies and autoreactive B cells. We will study the factors and underlying cellular mechanisms that govern Fab glycosylation of B cell receptors and autoantibodies. We will investigate the immunological effects and consequences of Fab glycosylation and their impact on B cells signaling and activation. In these analyses, we will also study the molecular and cellular interacting partners in the immune microenvironment in which the autoreactive B cells and antibodies act. Finally, we will test in relevant mouse models how Fab glycosylation of autoantibodies and autoreactive B cells contributes to the breach of tolerance. We expect that the insights obtained will provide new understanding into the role of glycans as key checkpoint for the selection of autoreactive B cells and the induction of autoimmunity. Likewise, we anticipate that our studies will provide leads for targeted therapeutic interventions as well as rationales for the early detection of RA and autoimmune diseases in general. We foresee that the knowledge generated will set the stage for a targeted prevention clinical study in patients at risk for RA to turn off the GlycanSwitch leading to chronic RA.

Work performed from the beginning of the project to the end of the period covered by the report and main results achieved so far

The GlycanSwitch project strives to uncover the mysteries of autoimmune diseases, in specific Rheumatoid Arthritis (RA). This disease is hallmarked by an immune response directed against targets normally expressed in the body. This autoimmune responses causes, amongst others, inflammation of the joints.
The stage for GlycanSwitch was set by the discovery that the RA-specific autoimmune response expresses a special feature; the presence of sugars (glycans) on the autoantibodies found in patients. As the presence of these sugars likely represent a “switch” that dictates disease onset, we are focusing on the chemistry and biology of these glycans.

In the last year, we have introduced a user-friendly and accessible method for antigen-specific glycosylation profiling, simplifying a complex process and making it more approachable for researchers across disciplines. Importantly, the methodology has been make open access and is available for all researchers in the world.
Likewise, several technologies to measure glycans on a large sample-set have been optimized and implemented in the analysis of glycan-traits present on antibodies. Furthermore, a novel technology has been developed to determine the diversity of the autoantibodies in RA. These studies revealed that the repertoire is diverse and unique to each patient, but also dominated by a limited number of antibody clones. These clones were shown to express several different glycovariants, demonstrating the complexity and patient-specific nature of the autoantibody response in RA. This research not only deepens our understanding of autoantibodies in RA, but also highlights their potential as critical biomarkers and therapeutic targets in RA.

Next to the studies focusing on technology development to further the analyses of glycans and their chemistry, we also analyzed the impact of glycans present in the B cell receptor. The B cell receptor is the molecule recognizing antigens in an highly specific manner and is expressed by B cells, the immune cells responsible for antibody production. When the B cell receptor is triggered, a B cell gets activated to make antibodies. In many autoimmune diseases, B cells are therefore intimately involved in disease pathogenesis as they produce the autoantibodies that hallmark autoimmune diseases. By analysing the impact of sugars expressed by the B cell receptor, important information has been obtained on the function of glycans expressed by the B cell receptor for activation of the (autoreactive) B cells.

Progress beyond the state of the art and expected potential impact (including the socio-economic impact and the wider societal implications of the project so far)

The results obtained now allow for an extensive, high throughput analyses of glycans expressed by antibodies using only limited amounts of blood from patients and other donors. This will further allow the in depth analyses of antibody glycosylation in the cohorts available to our consortium as well as other scientists and companies interested in this field. A next challenging aspect we hope to address is the development of an technique that enables the determination and glycan-composition of the auto-antibodies that are specific for RA. At the moment, such analyses are feasible in an high throughput manner, but also requires “high-end technologies” such as sophisticated mass-spectrometry machines. Likewise, still a relatively high volume of blood is required to obtain these antibodies in sufficient amounts as they are represent 0.1 - 1% of the total antibody level present in serum. In the coming year, we hope to develop these technologies as these will likely allow the measurement of glycans on autoantibodies at a larger scale in a more accessible format. Such developments are important as they are required for the development of diagnostic tools that can be used by diagnostic laboratories and hospitals. With such tools present, the “GlycanSwitch” can be measured and implemented across the world when of value for diagnostic/prognostic purposes.