Identification and characterisation of a novel Interleukin-4 receptor antagonist for allergy treatment

 The main focus of the PhD studies was the identification and characterization of a peptide antagonist which inhibited and/or down-regulated the binding of Interleukin-4 receptor to its cytokines IL-4 and IL-13 for allergy treatment. In addition, dietary components were tested for their ability to reduce inflammatory pathways of allergy, including fatty acids, resolvins and coenzyme Q10. Lastly, the Deakin AIRwatch project was undertaken which included the collection of ryegrass pollen data from 2012-2014 and its correlation with meteorological variables in regional Victoria.

Investigating interleukin-2 receptor family signaling in zebrafish

The zebrafish possesses all of the interleukin 2 receptor family except interleukin 2 receptor alpha and removal of the common signalling component interleukin 2 receptor gamma causes a human like severe combined immunodeficiency.

Identification and characterization of a novel IL-4 receptor α chain (IL-4Rα) antagonist to inhibit IL-4 signalling

BACKGROUND/AIMS: In recent times, allergy has become a financial, physical and psychological burden to the society as a whole. In allergic cascades, cytokine IL-4 binds to IL-4 receptor (IL-4R), consequently producing allergen-specific IgE antibodies by B cells. In addition, among other functions, IL-4 is also responsible for B and T cell proliferation and differentiation. Hence, characterization of novel antagonists that inhibit IL-4 signalling forms the overall aim of this study. METHODS: Phage display was used to screen a random 12-mer synthetic peptide library with a human IL-4Rα to identify peptide candidates. Once identified, the peptides were commercially synthesized and used for in vitro immunoassays. RESULTS: We have successfully used phage display to identify M13 phage clones that demonstrated specific binding to IL-4Rα. The peptide N1 was synthesized for use in ELISA, demonstrating significant binding to IL-4Rα and inhibiting interaction with cytokine IL-4. Furthermore, the peptide was tested in a transfected HEK-Blue IL-4 reporter cell line model, which produces alkaline phosphatase (AP). QUANTI-Blue, a substrate, breaks down in the presence of AP producing a blue coloration. Using this colorimetric analysis, >50% inhibition of IL-4 signalling was achieved. CONCLUSION: We have successfully identified and characterised a synthetic peptide antagonist against IL-4Rα, which effectively inhibits IL-4 interaction with the IL-4Rα in vitro. Since IL-4 interaction with IL-4Rα is a common pathway for many allergies, a prophylactic treatment can be devised by inhibiting this interaction for future treatment of allergies.

Mimtags: the use of phage display technology to produce novel protein-specific probes

In recent times the use of protein-specific probes in the field of proteomics has undergone evolutionary changes leading to the discovery of new probing techniques. Protein-specific probes serve two main purposes: epitope mapping and detection assays. One such technique is the use of phage display in the random selection of peptide mimotopes (mimtags) that can tag epitopes of proteins, replacing the use of monoclonal antibodies in detection systems. In this study, phage display technology was used to screen a random peptide library with a biologically active purified human interleukin-4 receptor (IL-4R) and interleukin-13 (IL-13) to identify mimtag candidates that interacted with these proteins. Once identified, the mimtags were commercially synthesised, biotinylated and used for in vitro immunoassays. We have used phage display to identify M13 phage clones that demonstrated specific binding to IL-4R and IL-13 cytokine. A consensus in binding sequences was observed and phage clones characterised had identical peptide sequence motifs. Only one was synthesised for use in further immunoassays, demonstrating significant binding to either IL-4R or IL-13. We have successfully shown the use of phage display to identify and characterise mimtags that specifically bind to their target epitope. Thus, this new method of probing proteins can be used in the future as a novel tool for immunoassay and detection technique, which is cheaper and more rapidly produced and therefore a better alternative to the use of monoclonal antibodies.

Somatostatin modulates G-CSF-induced but not interleukin-3-induced proliferative responses in myeloid 32D cells via activation of somatostatin receptor subtype 2

Somatostatin, originally identified as a peptide involved in neurotransmission, functions as an inhibitor of multiple cellular responses, including hormonal secretion and proliferation. Somatostatin acts through activation of G-protein-coupled receptors of which five subtypes have been identified. We have recently established that human CD34/c-kit expressing hematopoietic progenitors and acute myeloid leukemia (AML) cells exclusively express SSTR2. A major mechanism implicated in the antiproliferative action of somatostatin involves activation of the SH2 domain-containing protein tyrosine phosphatase SHP-1. While 0.1-1 x 10(-9) M of somatostatin, or its synthetic stable analog octreotide, can inhibit G-CSF-induced proliferation of AML cells, little or no effects are seen on GM-CSF- or IL-3-induced responses.
MATERIALS AND METHODS: To study the mechanisms underlying the antiproliferative responses of myeloblasts to somatostatin, clones of the IL-3-dependent murine cell line 32D that stably express SSTR2 and G-CSF receptors were generated. RESULTS: Similar to AML cells, octreotide inhibited G-CSF-induced but not IL-3-induced proliferative responses of 32D[G-CSF-R/SSTR2] cells. Somatostatin induced SHP-1 activity and inhibited G-CSF-induced, but not IL-3-induced, activation of the signal transducer and activator of transcription proteins STAT3 and STAT5.
CONCLUSION: Based on these data and previous results, we propose a model in which recruitment and activation of the tyrosine phosphatase SHP-1 by SSTR2 is involved in the selective negative action of somatostatin on G-CSF-R signaling.

Systemic apomorphine alters HPA axis responses to interleukin-1β adminstration but not sound stress

Apomorphine is a dopamine receptor agonist that was recently licensed for the treatment of erectile dysfunction. However, although sexual activity can be stressful, there has been little investigation into whether treatments for erectile dysfunction affect stress responses. We have examined whether a single dose of apomorphine, sufficient to produce penile erections (50 μg/kg, i.a.), can alter basal or stress-induced plasma ACTH levels, or activity of central pathways thought to control the hypothalamic-pituitary-adrenal axis in rats. An immune challenge (interleukin-1β, 1 μg/kg, i.a.) was used as a physical stressor while sound stress (100 dB white noise, 30 min) was used as a psychological stressor. Intravascular administration of apomorphine had no effect on basal ACTH levels but did substantially increase the number of Fos-positive amygdala and nucleus tractus solitarius catecholamine cells. Administration of apomorphine prior to immune challenge augmented the normal ACTH response to this stressor at 90 min and there was a corresponding increase in the number of Fos-positive paraventricular nucleus corticotropin-releasing factor cells, paraventricular nucleus oxytocin cells and nucleus tractus solitarius catecholamine cells. However, apomorphine treatment did not alter ACTH or Fos responses to sound stress. These data suggest that erection-inducing levels of apomorphine interfere with hypothalamic-pituitary-adrenal axis inhibitory feedback mechanisms in response to a physical stressor, but have no effect on the response to a psychological stressor. Consequently, it is likely that apomorphine acts on a hypothalamic-pituitary-adrenal axis control pathway that is unique to physical stressors. A candidate for this site of action is the nucleus tractus solitarius catecholamine cell population and, in particular, A2 noradrenergic neurons.

Identification of a gene for an ancient cytokine, interleukin 15-like, in mammals; interleukins 2 and 15 co-evolved with this third family member, all sharing binding motifs for IL-15Rα

Interleukins 2 and 15 (IL-2 and IL-15) are highly differentiated but related cytokines with overlapping, yet also distinct functions, and established benefits for medical drug use. The present study identified a gene for an ancient third IL-2/15 family member in reptiles and mammals, interleukin 15-like (IL-15L), which hitherto was only reported in fish. IL-15L genes with intact open reading frames (ORFs) and evidence of transcription, and a recent past of purifying selection, were found for cattle, horse, sheep, pig and rabbit. In human and mouse the IL-15L ORF is incapacitated. Although deduced IL-15L proteins share only ~21 % overall amino acid identity with IL-15, they share many of the IL-15 residues important for binding to receptor chain IL-15Rα, and recombinant bovine IL-15L was shown to interact with IL-15Rα indeed. Comparison of sequence motifs indicates that capacity for binding IL-15Rα is an ancestral characteristic of the IL-2/15/15L family, in accordance with a recent study which showed that in fish both IL-2 and IL-15 can bind IL-15Rα. Evidence reveals that the species lineage leading to mammals started out with three similar cytokines IL-2, IL-15 and IL-15L, and that later in evolution (1) IL-2 and IL-2Rα receptor chain acquired a new and specific binding mode and (2) IL-15L was lost in several but not all groups of mammals. The present study forms an important step forward in understanding this potent family of cytokines, and may help to improve future strategies for their application in veterinarian and human medicine.

Regulation of granulocyte colony-stimulating factor and its receptor in skeletal muscle is dependent upon the type of inflammatory stimulus

The cytokine granulocyte colony-stimulating factor (G-CSF) binds to its receptor (G-CSFR) to stimulate hematopoietic stem cell mobilization, myelopoiesis, and the production and activation of neutrophils. In response to exercise-induced muscle damage, G-CSF is increased in circulation and G-CSFR has recently been identified in skeletal muscle cells. While G-CSF/G-CSFR activation mediates pro- and anti-inflammatory responses, our understanding of the role and regulation in the muscle is limited. The aim of this study was to investigate, in vitro and in vivo, the role and regulation of G-CSF and G-CSFR in skeletal muscle under conditions of muscle inflammation and damage. First, C2C12 myotubes were treated with lipopolysaccharide (LPS) with and without G-CSF to determine if G-CSF modulates the inflammatory response. Second, the regulation of G-CSF and its receptor was measured following eccentric exercise-induced muscle damage and the expression levels we investigated for redox sensitivity by administering the antioxidant N-acetylcysteine (NAC). LPS stimulation of C2C12 myotubes resulted in increases in G-CSF, interleukin (IL)-6, monocyte chemoattractant protein-1 (MCP-1), and tumor necrosis factor-α (TNFα) messenger RNA (mRNA) and an increase in G-CSF, IL-6, and MCP-1 release from C2C12 myotubes. The addition of G-CSF following LPS stimulation of C2C12 myotubes increased IL-6 mRNA and cytokine release into the media, however it did not affect MCP-1 or TNFα. Following eccentric exercise-induced muscle damage in humans, G-CSF levels were either marginally increased in circulation or remain unaltered in skeletal muscle. Similarly, G-CSFR levels remained unchanged in response to damaging exercise and G-CSF/G-CSFR did not change in response to NAC. Collectively, these findings suggest that G-CSF may cooperate with IL-6 and potentially promote muscle regeneration in vitro, whereas in vivo aseptic inflammation induced by exercise did not change G-CSF and G-CSFR responses. These observations suggest that different models of inflammation produce a different G-CSF response.

Osteoclast formation elicited by interleukin-33 stimulation is dependent upon the type of osteoclast progenitor

Osteoclasts are bone resorbing multinucleated cells (MNCs) derived from macrophage progenitors. IL-33 has been reported to drive osteoclastogenesis independently of receptor activator of NFκB ligand (RANKL) but this remains controversial as later studies did not confirm this. We found IL-33 clearly elicited functional dentine-resorbing osteoclast formation from human adult monocytes. However, monocytes from only 3 of 12 donors responded this way, while all responded to RANKL. Human cord blood-derived progenitors and murine bone marrow macrophages lacked an osteoclastogenic response to IL-33. In RAW264.7 cells, IL-33 elicited NFκB and p38 responses but not NFATc1 signals (suggesting poor osteoclastogenic responses) and formed only mononuclear tartrate-resistant acid phosphatase positive (TRAP(+)) cells. Since TGFβ boosts osteoclastogenesis in RAW264.7 cells we employed an IL-33/TGFβ co-treatment, which resulted in small numbers of MNCs expressing key osteoclast markers TRAP and calcitonin receptors. Thus, IL-33 possesses weak osteoclastogenic activity suggesting pathological significance and, perhaps, explaining previous conflicting reports.