Specific Nongluten Proteins of Wheat Are Novel Target Antigens in Celiac Disease Humoral Response

While
the antigenic specificity and pathogenic relevance of immunologic
reactivity to gluten in celiac disease have been extensively researched,
the immune response to nongluten proteins of wheat has not been characterized.
We aimed to investigate the level and molecular specificity of antibody
response to wheat nongluten proteins in celiac disease. Serum samples
from patients and controls were screened for IgG and IgA antibody
reactivity to a nongluten protein extract from the wheat cultivar Triticum aestivum Butte 86. Antibodies were
further analyzed for reactivity to specific nongluten proteins by
two-dimensional gel electrophoresis and immunoblotting. Immunoreactive
molecules were identified by tandem mass spectrometry. Compared with
healthy controls, patients exhibited significantly higher levels of
antibody reactivity to nongluten proteins. The main immunoreactive
nongluten antibody target proteins were identified as serpins, purinins,
α-amylase/protease inhibitors, globulins, and farinins. Assessment
of reactivity toward purified recombinant proteins further confirmed
the presence of antibody response to specific antigens. The results
demonstrate that, in addition to the well-recognized immune reaction
to gluten, celiac disease is associated with a robust humoral response
directed at a specific subset of the nongluten proteins of wheat.