Sprue is a somewhat antiquated term referring generally to intestinal malabsorption

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Sprue is a somewhat antiquated term referring
generally to intestinal malabsorption
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Celiac Disease

• One of the most common immune-mediated disorders
• Prevalence in U.S./Europe ? 1
• Implies that approx. 3M afflicted in U.S. alone
• Causes destruction of villous structure in the
  intestine
• Symptoms diarrhea, fatigue, abdominal pain,
  malabsorption, neurological abnormalities

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Celiac Disease
Celiac Sprue is a lifelong disease, and if
untreated it is associated with increased
mortality
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Celiac Disease

• Triggered by ingestion of wheat gluten.

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Gluten

• Gluten is a general term for a composite of the
  storage proteins gliadin and glutenin.
• These proteins (conjoined with starch) comprise
  80 of the total protein in wheat/rye/barley
  seed.

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How does gluten cause negative effects?

• Certain Pro- and Gln-rich gliadin peptide
  fragments survive the digestion process make it
  to the gut
• These peptides are deamidated by tissue
  transglutaminase (tTGase)
• APCs in HLA-DQ2 or DQ8 positive individuals
  express these deamidated peptide fragments on
  class II MHC molecules
• The resulting CD4 T-cell mediated immune
  response can eventually result in the development
  of celiac disease

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• Therefore, the only currently recognized
  treatment for celiac disease is complete
  abstinence from food grains containing gluten
  proteins
• Bread, beer, cereals, many sauces

I tried a gluten-free diet for a month this year
Lets just say that I wasnt the nicest guy to be
around during that month. Its difficult!
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Aims of this study

• Determine the physiologically stable regions of
  gliadin
• Investigate the biochemical basis of this
  stability
• Shed light on possible future treatments for
  celiac disease

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Fig 1. gliadin digested with gastric
pancreatic proteases (pepsin, trypsin,
chymotrypsin, elastase, caboxypeptidase) followed
by LC-ESIMS
33-mer LQLQPFPQPQLPYPQPQLPYPQPQLPYPQPQPF
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Significance of 33-mer

• Even after prolonged exposure to proteases, the
  33-mer reamains intact
• Three previously identified epitopes (PFPQPQLPY,
  PQPQLPYPQ, and PYPQPQLPY) are found within this
  33-mer

33-mer LQLQPFPQPQLPYPQPQLPYPQPQLPYPQPQPF
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WQIPEQSR fragment used as a control
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Fig. 2. BBM digestions (A) 33-mer (B) Epitope
within 33-mer
BBM brush border intestinal membrane enzymes ?
essential for breaking down any remaining
peptides after gastric and pancreatic digestion
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Fig. 2.
33-mer LQLQPFPQPQLPYPQPQLPYPQPQLPYPQPQPF
Epitope within 33-mer QLQPFPQPQLPY
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Implication ? theres something about the 33-mer
which makes it highly resistant to physiological
enzymatic degradation
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Fig 3. Stimulation of 3 HLA DQ2-restricted T
cell clones, derived from patients with celiac
disease. Each of these T cell clones recognizes
a class II MHC molecule presenting a distinct
deamidated gluten epitope.
Implication ? the 33-mer is a very potent
stimulator of these HLA DQ2 restricted T cell
clones, even more so than the epitopes by
themselves Why??
EC50 80 nM (EC50 ? median effective
concentration)
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Table 2. Respose of polyclonal T cell lines
derived from patients with celiac disease to
gluten epitopes (peptide X) and the 33-mer
(bottom row)
we interpret the combination of metabolic
stability and multivalency of the 33-mer to
endow it with exceptional toxic potency
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Why is the 33-mer so resistant to
gastrointestinal breakdown?

• This is likely due to the abundance and location
  of proline residues
• This gave the authors the bright idea to
  investigate the activity of a prolyl
  endopeptidase (PEP) on breakdown of the 33-mer
• (prolyl endopeptidases cleave peptides after
  proline residues)

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• Fig 4.
• 33-mer incubated in vitro with PEP
• 33-mer digested in vivo in rat intestine with and
  without PEP
• Stimulation of HLA DQ2 restricted T cell clone by
  33-mer after PEP and BBM treatment, followed by
  tTGase treatment

PEP seems to effectively catalyze breakdown of
the 33-mer
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Overall implications of this study

• The 33-mer peptide, derived from gliadin, shows
  several characteristics suggesting that it is the
  primary initiator of the autoimmune response to
  gluten in patients with celiac disease.
• Potential for much further study vaccine??
• Prolyl endopeptidase therapy may have the
  potential to detoxify gluten in celiac disease
  patients.

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X-ray crystal structure of 33-mer bound to HLA-DQ2
Kim, et al. PNAS (2005)
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These are test results from a close family
member, showing indications of celiac disease
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Questions?