Characterization of the allergenic potential of proteins: an assessment of the kiwifruit allergen actinidin

Abstract

Assessment of the potential allergenicity (IgE-inducing properties) of novel proteins is an important challenge in the overall safety assessment of foods. Resistance to digestion with pepsin is commonly measured to characterize allergenicity, although the association is not absolute. We have previously shown that specific IgE antibody production induced by systemic [intraperitoneal (i.p.)] exposure of BALB/c strain mice to a range of proteins correlates with allergenic potential for known allergens. The purpose of the present study was to explore further the utility of these approaches using the food allergen, actinidin. Recently, kiwifruit has become an important allergenic foodstuff, coincident with its increased consumption, particularly as a weaning food. The ability of the kiwifruit allergen actinidin to stimulate antibody responses has been compared with the reference allergen ovalbumin, and with the non-allergen bovine haemoglobin. Haemoglobin was rapidly digested by pepsin whereas actinidin was resistant unless subjected to prior chemical reduction (reflecting intracellular digestion conditions). Haemoglobin stimulated detectable IgG antibody production at relatively high doses (10%), but failed to provoke detectable IgE. In contrast, actinidin was both immunogenic and allergenic at relatively low doses (0.25% to 1%). Vigorous IgG and IgG1 antibody and high titre IgE antibody responses were recorded, similar to those provoked by ovalbumin. Thus, actinidin displays a marked ability to provoke IgE, consistent with allergenic potential. These data provide further encouragement that in tandem with analysis of pepsin stability, the induction of IgE after systemic exposure of BALB/c strain mice provides a useful approach for the prospective identification of protein allergens.

Active actinidin retains function upon gastro‐intestinal digestion and is more thermostable than the E‐64‐inhibited counterpart

“…We have not been able elucidate why Bublin et al observed aggregation of actinidin and the reasons for these different in vitro digestion results are poorly resolved. However, our results are in good correlation with in vivo and in vitro digestion experiments from other studies . Further experiments directly comparing the different methodologies employed are required to resolve the issue.…”

Assessment of the Sensitizing Potential of Proteins in BALB/c Mice: Comparison of Three Protocols of Intraperitoneal Sensitization

“…Notably, the BALB/c mouse strain is considered to favor type 2 immune responses with atopic-like phenotype) [ 8 , 9 , 25 , 26 ]. Thus, this mouse strain has been widely used in the search for a validated murine model to evaluate the sensitizing or allergenic potential of proteins [ 4 , 5 , 8 , 9 , 11 ].…”

“…Certainly, most cases of food allergy are associated with a limited number of allergens, such as peanut, tree nuts, hen’s egg, cow’s milk, fish and shellfish, although the number of food allergens is large [ 2 , 3 ]. This could be attributed to an increased ability of these foods to sensitize and trigger allergic reactions and suggests that “a spectrum of allergenic or sensitizing potentials exists amongst food proteins” [ 4 ]. If such a spectrum does exist, the sensitizing potential of proteins, defined as the inherent capacity of proteins to trigger an IgE-mediated immune response, could be assessed not only in naturally occurring protein allergens, but also in food proteins derived from transgene products or proteins modified upon food processing.…”

Antibody Production, Anaphylactic Signs, and T-Cell Responses Induced by Oral Sensitization With Ovalbumin in BALB/c and C3H/HeOuJ Mice

“… 10 The importance of OVA stems not only from the high prevalence of egg allergy, the second more frequent food allergy in children below the age of 3, which affects up to 1.7% of children and adults, 11 but also because OVA is normally used as a model protein to investigate the molecular and cellular mechanisms of allergic sensitization and tolerance. 12 13 14 15 …”