The Helix aspersa (brown garden snail) allergen repertoire.
BACKGROUND
Ingestion of snails can induce strong asthmatic or anaphylactic responses, mainly in house-dust-mite-sensitized patients. The aim of this study was to identify the Helix aspersa (Hel a), Theba pisana (The p) and Otala lactea (Ota l) allergens and the extent of their cross-reactivity with the Dermatophagoides pteronyssinus (Der p) mite.


METHODS
In 60 atopic patients, skin prick tests (SPT) to snail and D. pteronyssinus, total and specific IgE, specific IgE immunoblots, RAST and immunoblot inhibition assays were performed.


RESULTS
Mean total IgE was >1,000 kU/l. Mean specific IgE (class 6 for Der p and class 2 for Hel a) SPT were positive in 44 patients for snail and in 56 for mite. Isoelectric focusing (IEF) and SDS-PAGE followed by immunoblotting of H. aspersa extract enabled the identification of 27 and 20 allergens, respectively. Myosin heavy chains from snails (molecular weight >208 kDa) disclosed two major allergens. Hel a and Der p RAST were strongly inhibited by their homologous extracts, with Hel a RAST being inhibited by the Der p extract to a much greater extent (72.6%) than the inverse (5.6%). A complete inhibition of the immunoblots by their homologous extract was obtained. However, Hel a extract did not inhibit Der p IEF separated recognition. On the other hand, mite extract extensively inhibited snail immunoblots from both IEF and SDS-PAGE separations. Immune detection on chicken, pig, rabbit, cow and horse myosins did not reveal any IgE cross recognition with snail.


CONCLUSIONS
In most cases of snail allergy, mite appeared to be the sensitizing agent. Nevertheless, snails may also be able to induce sensitization by themselves. This hypothesis is supported by the finding of specific IgE to Hel a in 2 patients who did not show specific IgE to Der p, and one of them was suffering from asthma after snail ingestion.
Martins
Luís Miguel Lourenço
LM
University of Evora, Evora, and S. Bernardo Hospital, Setúbal, Portugal. lmlm@uevora.pt
Peltre
Gabriel
G
da Costa Faro
Carlos José Fialho
CJ
Pires
Euclides Manuel Vieira
EM
da Cruz Inácio
Filipe Fernando
FF
D000293:Adolescent; D000485:Allergens / Q000009:adverse effects / Q000276:immunology*; D000818:Animals; D001249:Asthma / Q000209:etiology / Q000276:immunology; D003231:Conjunctivitis / Q000209:etiology / Q000276:immunology; D003429:Cross Reactions / Q000276:immunology*; D005260:Female; D005602:France; D006372:Helix, Snails / Q000276:immunology*; D006801:Humans; D007114:Immunization; D015151:Immunoblotting; D007073:Immunoglobulin E / Q000097:blood / Q000276:immunology; D008297:Male; D039981:Pyroglyphidae / Q000276:immunology*; D011852:Radioallergosorbent Test; D012221:Rhinitis, Allergic, Perennial / Q000209:etiology / Q000276:immunology; D012882:Skin Tests
D000485:Allergens; D007073:Immunoglobulin E