Allergy to peanut lipid transfer protein (LTP): frequency and cross-reactivity between peanut and peach LTP

SUMMARY

Background: Lipid transfer protein (LTP) is a widely cross-reacting plant pan-allergen, and sensitized patients may react to many foods. Although peanut allergy is frequently reported by LTP-allergic patients, the evidence of the presence of an allergen homologous to LTP in peanuts is limited. Objective: To assess the prevalence of peanut allergy in patients sensitized to LTP, detect any allergen homologous to LTP in peanuts, and assess its cross-reactivity with peach LTP. Methods: Spanish and Italian adults monosensitized to LTP were interviewed for possible peanut allergy and underwent skin prick tests (SPTs) with peanut extract. Sera from 32 peanut-allergic patients were assayed for peanut-specific IgE by direct ELISA and the Real Test; the serum showing the strongest reactivity was used in immunoblot analysis. Results: 74/114 (65%) patients were sensitized to peanuts, and 37 (32% of the whole population; 50% of those sensitized) were clinically allergic. Positive histories were validated by open oral food challenges in 13/13 cases. No SPT-negative patients reported clinical allergy to peanuts. Thus, in this selected population, sensitivity and negative predictive value of peanut SPTs were 100%, whereas specificity and positive predictive value were poor (52% and 32%, respectively). Only 2/32 sera scored positive in both in vitro assays and 4 reacted in the Real Test alone. In immunoblot, the serum studied reacted at about 10 kDa against the peanut extract; pre-adsorption with purified peach LTP totally inhibited such reactivity. Conclusions: Peanut sensitization is frequent among LTP-allergic patients and is clinically significant in about 50% of cases. Peanut tolerance should be assessed in LTP-allergic patients positive on peanut SPTs. Peanut LTP seemingly shares all allergenic determinants with peach LTP.