Cross-reactive IgE antibody responses to tropomyosins from Ascaris lumbricoides and cockroach

Background Evidence indicates that infection with Ascaris lumbricoides may promote development of allergy and asthma. Objective To study the role of tropomyosin, a pan-allergen in invertebrates, in IgE responses to A lumbricoides. Methods Recombinant A lumbricoides and Periplaneta americana tropomyosins were expressed in Pichia pastoris . Levels of IgE to tropomyosins from A lumbricoides and P americana were determined by chimeric ELISA in sera from 119 children living in a parasite-endemic area and 112 patients with cockroach allergy from the allergy clinics. Presence of tropomyosin in A lumbricoides larvae at L3 stage was evaluated by immunofluorescence using mAb 1A6, directed against mite tropomyosin. Molecular modeling of P americana and A lumbricoides tropomyosins was performed by using the MODELLER program. Results A lumbricoides tropomyosin showed 69% to 98% sequence identity to tropomyosins from other invertebrates. The predicted structure of A lumbricoides tropomyosin was similar to that of P americana tropomyosin and showed the characteristic coiled-coil structure. Strong correlation was found for IgE antibodies to tropomyosins from A lumbricoides and P americana in sera from children living in a parasite-endemic area and from patients with cockroach allergy. Larvae of A lumbricoides reacted strongly with mAb 1A6. Conclusion Tropomyosin induces IgE responses in A lumbricoides –infected children and in patients allergic to cockroach.