Matthew Cook

Effectiveness and response predictors of omalizumab in a severe allergic asthma population with a high prevalence of comorbidities: the Australian Xolair Registry

Severe asthma is a high impact disease. Omalizumab targets the allergic inflammatory pathway; however, effectiveness data in a population with significant comorbidities are limited.

Analysis of B cell memory formation using DNA microarrays.

Abstract: DNA microarray analysis of B cell subsets has identified comprehensive programs of gene expression that distinguish B cells at discrete stages of differentiation. The next task is to identify key genetic signals within these complex programs that regulate the dynamic cellular events during B cell activation in vivo. After stimulation with antigen, naïve B cells proliferate and differentiate, and then produce antibodies. Crucial qualitative differences in antibody responses are observed depending on whether or not B cells receive T cell help during activation. Proteins, lipopolysaccharides, and polysaccharides stimulate T‐dependent (TD), T‐independent type 1 (TI‐1), and type 2 (TI‐2) antibody responses, respectively. Only TD responses generate somatically mutated antibody‐forming (plasma) cells and memory B cells, which produce high affinity anamnestic responses to subsequent antigen challenge. Somatic mutation of immunoglobulin genes occurs during B cell proliferation in germinal centres (GC), which are typical in TD responses but rare in TI responses. However, we have described a model, which is exceptional because numerous large GC form in response to a model TI‐2 antigen, (4‐hydoxy‐3‐nitrophenyl) acetyl (NP)‐Ficoll. Significantly, these GC undergo involution before memory B cells are generated. This model provides an opportunity to investigate the genetic signals that drive memory cell formation, and we have compared global gene expression in TI and TD GC to identify a relatively small number of genes that are differentially expressed between the two prototypic B cell responses. This model demonstrates how genome‐scale technology can be adapted to investigate specific aspects of B cell biology.

Real‐life effectiveness of omalizumab in severe allergic asthma above the recommended dosing range criteria

Omalizumab (Xolair) dosing in severe allergic asthma is based on serum IgE and bodyweight. In Australia, patients eligible for omalizumab but exceeding recommended ranges for IgE (30–1500 IU/mL) and bodyweight (30–150 kg) may still receive a ceiling dose of 750 mg/4 weeks. About 62% of patients receiving government‐subsidized omalizumab are enrolled in the Australian Xolair Registry (AXR).

IL-10+CTLA-4+ Th2 Inhibitory Cells Form in a Foxp3-Independent, IL-2–Dependent Manner from Th2 Effectors during Chronic Inflammation

Activated Th cells influence other T cells via positive feedback circuits that expand and polarize particular types of response, but little is known about how they may also initiate negative feedback against immunopathological reactions. In this study, we demonstrate the emergence, during chronic inflammation, of GATA-3+ Th2 inhibitory (Th2i) cells that express high levels of inhibitory proteins including IL-10, CTLA-4, and granzyme B, but do so independently of Foxp3. Whereas other Th2 effectors promote proliferation and IL-4 production by naive T cells, Th2i cells suppress proliferation and IL-4 production. We show that Th2i cells develop directly from Th2 effectors, in a manner that can be promoted by effector cytokines including IL-2, IL-10, and IL-21 ex vivo and that requires T cell activation through CD28, Card11, and IL-2 in vivo. Formation of Th2i cells may act as an inbuilt activation-induced feedback inhibition mechanism against excessive or chronic Th2 responses.

Memory B-cell phenotyping in cvid – a journey through buddha’s nostril?

Common variable immunodeficiency (CVID) is a heterogeneous B-cell immunodeficiency disorder often characterised by failure of memory B-cell development and antibody secretion. Attempts have been made to stratify patients into clinical subsets based on aberrations in B-cell development very frequently found in this condition, the most characteristic subset being the ‘inflammatory’ group (‘Freiburg Ia’) characterised by a relative lack of memory B cells, and an expansion of CD21 negative B cells. Cohorts of CVID patients have been studied, largely in Europe, and cut-offs for the critical parameters established, along with their clinical implications. However, such cut-offs are only generalisable if similar values can be obtained across various laboratories. To assess this, we undertook a quality assurance program (QAP) in up to six laboratories in Australia, involving 16 specimens. We found marked variability in critical B-cell parameters, and an evident lack of consensus in classification allocation. Some of this variability could be explained by variations in cell preparation method, gating strategy, and cytometer platform, whilst some were difficult to explain. Thus, progress in B-cell phenotyping in CVID is likely to require strict standardisation of methodology, reagent, cytometer, and gating, and (since such parameters were unlikely to reflect the original European studies) a revision of normal ranges based on such standardised methodology.