Identification and quantitation of human B regulatory cells via Flow Cytometry and their potential role as a treatment efficacy biomarker in allergen-specific immunotherapy

Not yet collecting data or writing up the project therefore no abstract. Supplied background information to justify research and research hypothesis.

Allergen immunotherapy (AIT) is a disease-modifying treatment for IgE-mediated allergic disease which promotes the conversion of a pro-allergic Th2 phenotype to a Th1-type immune response.1 Through several complex and interdependent mechanisms, AIT induces immune tolerance against a specific allergen, thus de-sensitising the recipient to the causative allergen.

These mechanisms include:

1. Induction of T regulatory (TREG) cells which downregulate the allergic inflammatory response through inhibitory cell-cell interactions via cell-surface molecules such as CTLA4 and PD1. TREG cells also release the cytokines IL-10, IL-35 and TGF-β which downregulate the pro-allergic environment, and induce a Th1-type response via production of blocking antibodies such as allergen-specific IgG4.
2. Production of allergen-specific IgA and IgG4 antibodies which block interactions between cell surface-bound allergen-specific IgE. This prevents IgE cross-linking, thus inhibiting mast cell and basophil effector cell function.

A more recently described, but not well-understood, mechanism of AIT-induced immune tolerance centres on the role of B regulatory (BREG) cells. Current evidence suggests AIT promotes an increase in production of BREG cells which possibly contributes to tolerance induction via the release of the immune-modulatory cytokines IL-10, IL-35 and TGF-β, that leads to induction of TREG cell population expansion and production of ‘IgE-blocking’ allergen-specific IgA and IgG4 antibodies.

Current literature has started to focus on the identification of biomarkers for determination of AIT treatment efficacy as these may offer:

1. more efficient and effective patient care pathways and financial cost savings by early indication of responder/non-responder status, allowing discussion of earlier AIT product or administration method changes in those showing sub-optimal response
2. personalised marker of treatment optimisation , potentially allowing identification of who and when patients can move on to maintenance dosing or when IT can be stopped (especially with venom immunotherapy)
3. sufficient evidence of patient de-sensitisation
4. potential evidence of longevity of response

Several studies have identified changes in cellular and humoral immune responses in patients receiving AIT, some of which have demonstrated a correlation between extent of change in responder and non-responder cohorts. Although measurement of a number of parameters such as total IgE, allergen-specific IgE, blocking antibodies and TREGS have all been explored, currently there is no standardised AIT efficacy biomarker or panel of biomarkers adopted in clinical practice. It is hypothesised that gaining a greater understanding of the role of BREG cells in immune tolerance induction during AIT could offer a potential pathway for targeted therapeutics, as well as acting as a potential biomarker of AIT efficacy.

Overall hypothesis

We hypothesise that a flow cytometry method for the detection and quantitation of BREG cells in whole blood can be successfully developed locally, with acceptable performance characteristics. Secondly, we hypothesise that patient whole blood BREG cell concentration will increase over the first year receiving AIT treatment and will correlate with improved clinical symptoms upon subsequent exposure to the sensitising allergen, and therefore their measurement may be useful as a biomarker for AIT treatment efficacy.