The Digestive Fate and Intestinal Transport Pathway of Parvalbumin Underlying Its Strong Allergenicity.

Parvalbumin, the major fish allergen, exhibits allergenicity, yet its digestive and absorptive behavior in vivo remains poorly understood. This study evaluated digestion-dependent changes in IgE reactivity and the in vivo behavior of parvalbumin from salmon, flounder, and herring. In vitro, parvalbumin was rapidly cleaved by pepsin-trypsin, but the resulting low-molecular-weight fragments retained substantial IgE reactivity. In mice, orally administered parvalbumin was also digested in the gastrointestinal tract, although part of the protein persisted in the small intestine for extended periods. Notably, parvalbumin traversed the cytoplasm of intestinal epithelial cells and rapidly appeared in the venous bloodstream, indicating transcellular absorption. These findings were consistent across the three species, suggesting that the persistence of parvalbumin's IgE reactivity despite extensive digestive fragmentation, together with its sustained intestinal uptake, is associated with its strong allergenic potential. This study provides key insights into the mechanisms linking digestive and absorptive processes to parvalbumin allergenicity.