Changes in passively‐sensitized basophil activation to αS1‐casein after oral immunotherapy

Abstract

Introduction: Immune response to cow's milk allergen (CMA) has been analyzed mostly using crude milk antigen or a mixture of various caseins. This study aimed to assess the changes in the immunological response against αS1-casein during oral immunotherapy (OIT) and to investigate the mechanism of tolerance. Methods: We have performed rush OIT to 39 patients with CMA and obtained the serum samples up to 3 years after OIT. Immunoglobulin E (IgE) and IgG4 antibodies specific to highly purified αS1-casein as well as passively-sensitized basophil activation were evaluated using the serial samples. Furthermore, we examined whether basophil activation led by the pre-OIT serum was suppressed by the post-OIT serum, or by the tolerant serum obtained from naturally outgrown patients. Results: Specific IgE to αS1-casein was significantly reduced after OIT. Specific IgG4 (sIgG4) to αS1-casein was also detected in most of the pre-OIT sera, which was not significantly increased after OIT. Activation of passivelysensitized basophils to αS1-casein was significantly reduced after 2 years (14% ± 19%) and 3 years (19% ± 18%) post-OIT compared with pre-OIT (%CD63 high basophils; 51% ± 27%). Furthermore, the addition of post-OIT or tolerant serum to pre-OIT serum significantly suppressed the basophil activation. This suppression was abrogated by washing the supernatant after passive sensitization, but not by depleting IgG antibodies from post-OIT or tolerant sera, nor by blocking FcγRIIb using an anti-FcγR antibody. Conclusions: αS1-casein-sIgG4 plays a minor role in tolerance mechanisms in cases of CMA; humoral factors other than antigen-sIgG4 may be involved.

Evaluation of cross‐reactivity between casein components using inhibition assay and in silico analysis

“…This study used serum from 39 patients [median age 8 years (IQR 6-10 years)], from a previous study, with persistent CM allergy before oral immunotherapy. 4,8 These patients were required to have retained their milk allergy over age 5 with the threshold dose less than 5 mL of CM confirmed by an oral food challenge test, and detectable specific IgE (>0.34 UA/mL) to CM and whole CN by ImmunoCAP ® .…”

Principles, potential, and limitations of ex vivo basophil activation by flow cytometry in allergology: A narrative review

“…4,5 With respect to BATs using components, it is noteworthy that a single component rarely covers the entire sensitization profile, 79,80 and that outcomes have been reported to be age and/or population dependent. 74 BATs have also been used to monitor AIT and allergen-specific oral immunotherapy for peanut, 57,[81][82][83] sesame, 84 cow's milk, [85][86][87] and egg. 88 In line with the findings for aeroallergens, reduced basophil allergen sensitivity during AIT and oral immunotherapy with food is likely due to interference of blocking sIgG antibodies.…”

“…88 In line with the findings for aeroallergens, reduced basophil allergen sensitivity during AIT and oral immunotherapy with food is likely due to interference of blocking sIgG antibodies. [81][82][83][84]87,88 Acosta et al 89 recently provided an immunologic explanation as to why birch-associated apple allergy cannot be effectively treated by administration of the sensitizing pollen allergen (sublingual immunotherapy with recombinant Betula verrucosa 1, the major allergen from birch Betula verrucosa]). They found that treatment with recombinant Betula verrucosa 1 promotes specific IgG antibodies that cross-react with recombinant Malus domesticus 1 from apple but lack sufficient affinity to inhibit BATs with apple allergens and induce cross-protection.…”

Evaluation of cross-reactivity between casein components using inhibition assay and in silico analysis

“…This study used serum from 39 patients [median age 8 years (IQR 6-10 years)], from a previous study, with persistent CM allergy before oral immunotherapy. 4,7 These patients were required to have retained their milk allergy over age 5 with the threshold dose less than 5 mL of CM confirmed by an oral food challenge test, and detectable specific IgE to CM and whole CN by ImmunoCAP ® .…”