Rheumatoid Arthritis (RA) is the commonest, most destructive, autoimmune inflammatory arthritis, causing chronic pain, fatigue, depression and disability. Over 20,000 new cases are diagnosed each year in the UK . The majority of patients are treated with synthetic disease modifying anti-rheumatic drugs (DMARDs), that are both poorly tolerated and rarely induce disease remission . Hence an unmet need for thousands of RA patients is a clearer understanding of disease pathogenesis, that would lead to optimized therapeutic protocols and eventually a cure.
RA is strongly associated with a white blood cell, called a B lymphocyte that secretes autoantibodies and inflammatory proteins (cytokines). Whilst B cell depletion therapy (BCDT) is effective at treating RA, the high cost and indiscriminate loss of all CD20+ve B cells increases the risk of infection and limits its use. Knowing which B cell subset to target for BCDT would lead to improved treatment stratification and potentially a cure if only pathogenic B cells could be permanently ablated.
Over the last 4 years our research groups at Edinburgh and Glasgow Universities have collaborated on a detailed study of RA patients, collecting and curating RA patient samples and data from across Scotland (Glasgow, SERA study) and analyzing their B cells, utilising next generation sequencing (NGS), to identify the full length of the peripheral blood B cell receptor (BCR) sequence, assessing between 25,000 to 200,000 BCR sequences per patient. From a total of 143 RA patients, we discovered that RA patients expressed a significantly higher percentage of poorly mutated polyclonal IgG+ve variable heavy (IgG-Vh) BCR sequences (B-RA) in the peripheral blood, both at the time of diagnosis and following treatment. These B-RA sequences resided within TNF-alpha secreting IgG+veCD27-ve B cells, that were expanded in RA peripheral blood and enriched in the rheumatoid synovium. This conclusively established that a substantial component of the peripheral B cell repertoire in RA consists of polyclonal hypomutated IgG+ve BCRs. IgG isolated from rheumatoid joints binds to a diverse range of proteins and peptides found within the synovium and cartilage .
We hypothesise that pathogenic polyclonal IgG originates from the B-RA cells. If so, it links a subset of B cells to disease pathogenesis.
1) Fully characterise the IgG+veCD27-ve B-RA cells in RA. 1A. Phenotype (by flow cytometry) and RNA Seq B-RA cells, isolated from the peripheral blood and synovium of 15 DMARD naïve RA patients, to determine the relationship between surface markers, the transcriptome of each leukocyte subset and the B-RA frequency. 1B. Follow with Single cell RNA Seq of 300 IgG+veCD27-ve B cells taken from each of 8 RA blood and synovial samples. cDNA libraries will be spilt to enable full sequencing of the BCR heavy and light chains from each sample. This will enable future cloning of the B cell receptors to discover their specificity.
This aim will provide a complete picture of the relationship between IgG+veCD27-ve B cells in the blood and synovium, correlating their inflammatory transcriptome to the frequency of hypomutated BCRs.
2) Do IgG+veCD27-ve B cells expressing hypomutated BCRs predict the response to BCDT? NGS of existing samples (from the ORBIT study/Glasgow) taken prior to and 6 months following BCDT will identify if B-RA sequences correlate with the clinical response to BCDT. If so we will have discovered a biomarker of response to BCDT.
3) Does the frequency of hypomutated IgG+veCD27-ve (B-RA) correlate with disease relapse following BCDT?
Prospectively test for B-RA to assess their frequency prior to and at 3 month intervals following BCDT (in a dedicated clinic run by MG) to determine if B-RA return predicts disease relapse. If so we will have discovered a way to monitor patients to determine the optimal time for therapeutic intervention with repeat BCDT.
This MRC programme is joint between the Universities of Edinburgh and Glasgow. You will be registered at the host institution of the primary supervisor detailed in your project selection.
All applications should be made via the University of Edinburgh, irrespective of project location. For those applying to a University of Glasgow project, your application along with any supporting documents will be shared with University of Glasgow. http://www.ed.ac.uk/studying/postgraduate/degrees/index.php?r=site/view&id=919
Please note, you must apply to one of the projects and you must contact the primary supervisor prior to making your application. Additional information on the application process is available from the link above.
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McInnes, I.B. and G. Schett, The pathogenesis of rheumatoid arthritis. N Engl J Med, 2011. 365(23): p. 2205-19.
Markusse, I.M., et al., Long-Term Outcomes of Patients With Recent-Onset Rheumatoid Arthritis After 10 Years of Tight Controlled Treatment: A Randomized Trial. Ann Intern Med, 2016. 164(8): p. 523-31.
Monach, P.A., et al., A broad screen for targets of immune complexes decorating arthritic joints highlights deposition of nucleosomes in rheumatoid arthritis. Proc Natl Acad Sci U S A, 2009. 106(37): p. 15867-72.