Coeliac Disease: Prevention and Therapeutic Advances
Coeliac UK’s Research Conference 2015
Opening the day’s conference, Coeliac UK’s chief executive Sarah Sleet spoke about the charity’s ongoing dedication to research, and announced plans to ‘create the next generation of researchers into coeliac disease’.
“Our plan is to raise £5m in the run up to 2018 – our 50th anniversary – and to invest that in 50 research fellowships to create that next generation,” she said.
The meeting was chaired by Professor David Sanders or Royal Hallamshire Hospital, Sheffield, who introduced speakers.
• Rationales Behind Novel Therapies for Coeliac Disease – Professor Ludwig Sollid
Rationales Behind Novel Therapies for Coeliac Disease
Wheat is hard to digest. Gluten peptide fragments survive digestion and cross the epithelium, although we don’t know exactly how. They are modified by the enzyme transglutaminase 2, and become deamidated. Deamidated gluten peptides bind to HLA DQ2/8 molecules on the surface of antigen-presenting cells and are recognised by gluten-specific T cells (CD4+ cells) – and cytokines are produced.
CD4+ is the “director of the immunological orchestra” – instructing other cells to become aggressive. Among those cells are the intraepithelial lymphocytes, and these can kill off enterocytes – which probably leads to the villous atrophy typical of CD. It is the clonal expansion of these CD4+ cells and two types of B cells (in this case TG2-specific B cells and gluten-specific B cells, which are assisted by CD4 cells) which magnifies the immune response, and signifies the patient is ‘crossing the bridge’ into coeliac disease.
So what kind of non-dietary treatments are possible? They fall into two camps.
1. Those which prevent gluten from stimulating T cells:
2. Therapies which modify the immune response:
Therapy and Diagnosis Utilising Peptides Recognised by Gluten Reactive T cells
He pointed out that diagnostic tests for gluten-specific T cells – if they could be identified and measured in clinical practice – would overcome the need for and shortcomings of biopsy, as well as inaccurate or indeterminate histology. They may also avoid the need for an oral gluten challenge, in those already on a GFD. Further, if a therapy could be developed to ‘tolerize’ gluten reactive CD4+ T cells, it may be possible for coeliacs to resume an unrestricted gluten-containing diet.
A gluten challenge mobilises large numbers of T cells, and DQ2.2, DQ2.5 and DQ8 react to different peptides.
Anderson’s work with ImmusanT in developing the Nexvax2® vaccine to restore immune tolerance to gluten is targeted at DQ2.5 patients – and the dominant peptides driving the most T cells in these patients are the classic alpha gliadin 1 and 2 (33-mer) peptides in wheat, plus the omega gliadin 1 and 2 peptides in rye, and hordein 3 in barley. These three account for two-thirds of the T cell response, and form the basis of the vaccine, for which initial proof of concept, of induction of tolerance in DQ2.5 in mice, has been satisfied. Phase 2 studies begin this year in UK and internationally, with phase 3 expected in 2017 or 2018.
Gluten Degradation by ALV003, a Novel Drug Candidate in Phase 2B Clinical Development for Coeliac Disease
Up to 60% of adult coeliac patients are symptomatic despite being on the GFD for 8-12 years. In a sample of 200 patients following a GFD, over 90% experienced at least one symptom associated with CD in a seven-day period, while 44% had 5-10 symptoms. For over 40%, the symptoms were severe or very severe.
Patients regularly have persistant mucosal inflammation. Under 20% of GFD-compliant patients in clinical remission have histological normalisation. After two years, only a third have mucosal recovery; after five years, it is two thirds. Mucosal recovery is associated with a reduced rate of all-cause mortality, and reduced risk of malignancies.
In a sample of 117 occasionally symptomatic patients who had been on a GFD for at least a year, examined for villous height / crypt depth ratio, it was found that those with negative serology, following a GFD for an average of 6.3 years, the average ratio was 1.9 (within Marsh 3a classification) and for those with positive serology, following a GFD for an average 5.6 years, the average ratio was 1.3 (Marsh 3b).
Many patients have significant disease-associated symptoms and intestinal mucosal injury despite following a GFD. “We as physicians often tell those patients who are following a GFD well enough to go from sero-positive to sero-negative that their coeliac disease is well controlled,” said Adelman. “This is a major problem that is only now beginning to be understood – how poor the GFD really is for managing this disease.”
Alvine’s ALV003, which Adelman’s team is developing, is a gluten-specific protease (gluten enzyme), intended as an adjunct to the GFD in coeliac disease. In fact, it is a mixture of two proteases – EP-B2 (ALV001), which curiously is derived from barley, and SC-PEP (ALV002).
In a phase 2A proof of principle study, 41 patients were recruited, and given 2g gluten daily for 6 weeks. After six weeks, there was virtually no decrease in the villous height / crypt depth ratio in patients receiving ALV003, but a substantial decrease was noted in patients on placebo.
Looking at patients individually, a remarkable finding was that 40% of treated patients actually had improvement of their villous height / crypt depth ratio, despite having 2g of gluten added to their otherwise GFD. When researchers looked at intraepithelial lymphocytes, a striking difference was found between treated and placebo. There was significant increase of T cell densities in placebo patients, but none at all in treated.
Phase 2B – the Celiaction Study – is now underway, with a sample size of around 500.
What is Elafin and does it play a role in gluten-related disorders?
Elafin is a human molecule that acts as an anti-protease – or protease inhibitor. It is quite specific to pro-inflammatory proteases produced by neutrophils, such as elastase. It is expressed in the epithelia, and has protective effects in the lung, cardiovascular system and the female reproductive system. It is abnormally expressed in the colon of IBD patients, where it is downregulated. Supplementation of elafin is thought to reduce pro-inflammatory elastases in IBD – but could this work in CD?
Verdu’s team found that patients with CD have decreased elafin expression, and that patients on a GFD and in remission fall between this group and non-coeliac controls in terms of elafin expression. Could there be, therefore, a therapeutic potential for elafin in CD?
Looking into the effects of elafin on the key 33-mer immunogenic gluten peptide, it was found that elafin decreased deamidation – a known key step in the pathogenesis of CD. Furthermore, in a mouse model, elafin was seen to reduce gliadin-induced intestinal barrier dysfunction, inflammation, and intraepithelial lymphocyte infiltration.
Verdu speculated that elafin could represent a marker in villous health, that its loss could contribute to CD pathogenesis, and supplementation may have potential as an adjuvant therapy to a GFD in CD.
Targeting the gluten specific T cell response: a novel therapeutic approach in coeliac disease
That said, there are enzymes (not yet commercially available) which can degrade gluten. Studies show that they can work better in an acidic gastric milieu – a US-style Big Mac Meal (with acidic soda) is ‘deglutenised’ in a mechanical digestion model whereas a Dutch-style Big Mac Meal (often consumed with neutral milk) is not. The point here is that enzymes can work, but the mode of action depends on what you eat with the gluten-containing food.
But what we would like is to cure or predict disease, said Koning. There has been focus on HLA and on gluten peptides, but what about T cells? Can the disease-causative T cells be eliminated or neutralised?
Research has shown T cell responses to immunodominant gluten peptides is remarkably similar between all coeliac patients. Koning believes this may allow the possibility to interefere in the disease process by potentially allowing the design of compounds that target the T cell receptors. By coupling such compounds with toxins it may become possible to eradicate the disease-causing T cells without interfering with the normal function of the immune system.
The plant-related strategies Dr Gilissen outlined were:
* Selection of low-CD-immunogenic wheat lines
As far as food related strategies went, he suggested:
* Reduction of the use of vital gluten in the food industry – used to ‘boost’ loaves – and which may be implicated in part for the increase in CD;
He closed by considering alternative and ‘ancient’ grains. Einkorn and emmer wheats may be safe for some coeliacs, but spelt is toxic. Oats are safe for the vast majority, but cross-contamination remains a key issue.
Coeliac Disease: What you need to know by Alex Gazzola, is out now.