Peanut applied to the skin of nonhuman primates induces antigen-specific IgG but not IgE.

INTRODUCTION

Previous studies in humans support the dual-allergen exposure hypothesis, and several studies in mouse models have demonstrated that cutaneous exposure to disrupted or intact skin can lead to sensitization to peanut. However, the field lacks definitive evidence that cutaneous exposure leads to peanut allergy in humans or other primates.

METHODS

Peanut extract was applied to the shaved back of the neck of four male and four female African green monkeys three times per week for 4 weeks. An oral food challenge (OFC) was performed the following week by gavage of 200 mg of peanut protein, and vital signs were monitored for 30 minutes post-OFC. Blood was collected at baseline, day 11, day 32, and 30 minutes post-OFC. Total IgE, and peanut-specific immunoglobulin E (IgE) and immunoglobulin G (IgG) were quantified in serum collected throughout the 4 weeks. Histamine was measured in serum collected 30 minutes post-OFC.

RESULTS

Peanut-specific IgE was undetectable at any time points in any of the monkeys, and there was no consistent increase in total IgE. During the oral challenge, none of the monkeys experienced allergic symptoms and histamine levels did not change. However, seven of the eight monkeys produced increasing peanut-specific IgG by day 32, indicating that repeated skin exposure to peanut is immunogenic.

CONCLUSIONS

Skin exposure to peanut did not lead to sensitization in this study, and monkeys did not experience anaphylaxis upon peanut challenge. However, monkeys produced increased peanut-specific IgG throughout peanut exposure, indicating that repeated skin exposure to peanut is immunogenic.