Allergy information for: Snail (Helix aspersa )

  • Name: Snail
  • Scientific Name: Helix aspersa
  • Occurrence: Snail are eaten cooked with consumption being highest in France, Italy, Spain and Portugal.
  • Allergy Information:

    Allergy to molluscs such as snail is less common than allergy to shrimps. Snail allergy is associated with an unusual distribution of symptoms with asthma being very frequently reported. However, mild symptoms such as oral allergy syndrome, urticaria (hives) and severe symptoms such as anaphylactic shock can also occur after consumption.

    Allergy to snail is frequently associated with allergy to dust mites and this may account for the high frequency of asthma and rhinitis seen as symptoms. There are also concerns that desensitization therapy with dust mite extracts may cause a more severe reaction to snails. Some individuals with allergy to shrimp (crustacea) may also suffer associated allergy to snail. For others, their allergy to snail is associated with allergy to other shellfish (molluscs) such as abalone and limpet which can include serious or fatal reactions.
  • Other Information:

    Allergic reactions have been reported to several species of snails including the brown garden snail (Helix aspersa), the burgundy snail (Helix Pomatia), and the vinyard snail (Cernuella virgata). Helix terrestre may be a synonym for one of these. Euparipha pisana is probably Euparypha pisana also called Helix pisana and probably most correctly Theba pisana or the white garden snail. Allergic reactions to the sea snail Bolinus brandaris have also been reported.

    Image of Helix aspersa by Jeremy Lee reproduced with permission from http://www.uknature.co.uk/GSnail-info.html.
  • Taxonomic Information: NEWT http://www.ebi.ac.uk/newt/display?search=6535
  • Last modified: 18 October 2006

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      Clinical History

      • Number of Studies:11-20
      • Number of Patients:>50
      • Symptoms:

        Martins et al (2005) [1663] note that only 6 of 60 selected atopic patients showed symptoms after snail ingestion which were asthma in all cases. All had CAP class 2 or higher with Helix aspersa. The primary sensitization in most patients was to mites with IgE cross-reactivity to snails which frequently did not cause clinical symptoms.

        Wu & Williams (2004) [1709] report a case of a patient known to be allergic to abalone who suffered fatal anaphylaxis after eating 3 snails.

        Moneret-Vautrin et al (2004) [1016] and Morrisset et al. (2003) [1742] report that ingestion of snails resulted in 5 of 107 cases of severe food allergy in 2002. Severe asthma was again observed as a symptom and all 5 patients were sensitized to dust mites.

        Asturias et al (2002) [1662] describe the symptoms of patients following snail ingestion as including asthma, pruritus, facial oedema and gasteroinstinal symptoms. Sera from 22 patients with at least 2 symptoms, positive SPT and RAST were chosen for allergen characterization.

        Longo et al (2000) [1668] describe a case of specific-food-dependent exercise-induced anaphylaxis after eating snails in a child sensitive to house-dust mites. He developed chest pain, bronchial constriction that did not respond to salbutamol, dizziness, urticaria, vomiting, cyanosis, and finally collapse. Taken to an emergency department, he eventually developed respiratory failure, which required intubation, and a seizure. He was maintained in mechanical ventilation for 12 h.

        Vuitton et al. (1998) [1664] report the symptoms of 7 children as erythema and swelling at the injection site of immunotherapy; anaphylactic shock, cough and facial oedema; pruritis, asthma and wheals on the arms; pruritis, asthma, wheals, erythema, pain and swelling of the arms; asthma and anaphylactic shock; facial oedema, asthma, urticaria and anaphylactic shock; malaise, asthma, rhinitis, urticaria.

        Van Ree et al. (1996) [1609] report a group of 28 patients with combined snail and dust mite allergy who all reported asthma after snail ingestion and who had asthma and/or rhinitis associated with dust mites. Urticaria was a symptom of 13 patients and there were 2 cases of anaphylaxis after snail ingestion while symptoms with dust mites were restricted to asthma and/or rhinitis.

        Grembiale et al (1996) [1738] describe a case of asthma associated with eating snails.

        Didier et al. (1996) [1741] report 4 patients who reacted to snails with asthma in 2 cases, Quincke's oedema (laryngeal oedema) in one case and anaphylactic shock in one case.

        De Maat-Bleeker et al. (1995) [1671] report a single case of anaphylaxis after snail ingestion in a dust mite sensitized patient.

        Pajno et al. (1994) [1740] reported cough and asthma in 11/15 children, with known asthma and mite allergy, after open oral challenges with 30 g of cooked snails. 3 children also showed cutaneous symtoms.

        Banzet et al. (1992) [1739] reported 12 patients, with known respiratory dust mite allergy, who reacted following eating snails. In 7 cases this involved a typical asthma attack (5 times) or asthmatiform dyspnea (3 times), in 2 cases severe anaphylaxis and in 5 cases an erythematous reaction of the skin with wheals and subcutaneous tissue of the region of the arm in which acaris (dust mite) desensitisation injections had been administered during previous years.

        Oehling et al. (1992) [1744] note that allergic reactions following eating snails tends to involve asthma and rhinitis.

        Ardito et al. (1990) [1754] report 14 patients with asthma on snail ingestion and sensitization to dust mites.

        de la Cuesta et al. (1989) [1700] report 10 patients of whom 8 showed primarily respiratory symptoms.

        Amoroso et al. (1988) [1743] report that the symptoms were asthma after snail ingestion in their snail allergic subjects.

        Palma Carlos et al. (1985) [1755] report asthma associated with snail ingestion.

      Skin Prick Test

      • Number of Studies:1-5
      • Food/Type of allergen:

        Vuitton et al. (1998) [1664] used commercial snail extracts (Allerbio, Varennes-en-Argonne, France and Romanzini, La Rivière-Drugeon, France), commercial Dermatophagoides extract (Stallergènes, Fresnes, France), extracts of whole body, the foot, the visceral mass and the haemolymph of Helix aspera aspera, H. aspera maxima, H. lucorum or H. pomatia and an extract of Buccinum undatum. Extracts of the snail mite Riccardoella limacum were made by collecting mites in absolute ethanol and drying. Extracts were made in phosphate buffered saline and centrifuged at 8000 g for 15 minutes. Heated extracts were heated for 15 minutes at 100°C.

        Didier et al. (1996) [1741] used commercial snail extract (Stallergènes, France)

        Pajno et al. (1994) [1740] used commercial snail extracts (Lofarma, Milan) for skin prick tests.

        Amoroso et al. (1988) [1743] boiled 500 g. of snail (Euparipha pisana) for 10 minutes, separated the body from the shell and homogenised the body in distilled water. The mixture was centrifuged at 10000 g for 10 minutes and the supernatant defatted with the same volume of ethyl ether at room temperature. The supernatant was then dialysed using an Amicon YM5 filter (5 kDa cut-off) and the protein concentration measured. 

      • Protocol: (controls, definition of positive etc)

        Vuitton et al. (1998) [1664] performed skin tests in duplicate on the forearms and a wheal diameter ≥3 mm larger than the negative control and at least half the diameter of the codeine positive control after 15-20 minutes was judged positive.

        Didier et al. (1996) [1741] used codeine phosphate as positive control. Wheal diameters ≥4 mm larger than the negative control were considered as positive.

        Pajno et al. (1994) [1740] considered as positive a wheal diameter ≥3 mm larger than the negative control.

      • Number of Patients:

        Vuitton et al. (1998) [1664] tested 169 children attending an allergy clinic who had not eaten snails and 7 snail allergic children.

        Didier et al. (1996) [1741] tested 312 patients with respiratory allergies.

        Pajno et al. (1994) [1740] tested 51 children with asthma and allergic to mite (out of 503 attending an allergy clinic).

        Amoroso et al. (1988) [1743] tested 70 individuals allergic to the more common allergens of the Mediterranean area and 30 subjects who were not allergic.

      • Summary of Results:

        Asturias et al (2002) [1662] reported positive SPT in 22 patients.

        Vuitton et al. (1998) [1664] reported that 38/169 children who had not eaten snails had a positive SPT to snail extracts. 28 had a positive prick test to heated crude H. aspera and 19 to a commercial extract. 9 also had a positive SPT to whelk (Buccinum undatum). All 38 children had asthma. 6 had food allergies to mustard (3 children), salmon, chicken, egg, and shrimp. 30/38 SPT positive children were found to be sensitized to dust mites by SPT or RAST.

        Vuitton et al. (1998) [1664] also reported that all 7 snail allergic patients gave positive SPTs with some extract (foot, visceral mass or haemolymph) of one of the snail species (H. aspera aspera, H. aspera maxima, H. lucorum or H. pomatia). However, different extracts were positive with different individuals. Raw extracts of snail gave stronger reactions than heated extracts. All reacted to commercial complete H. pomatia extract and to dust mite. None of the individuals reacted to the snail mite Riccardoella limacum.

        Didier et al. (1996) [1741] reported that 239/312 individuals were sensitized to at least one aeroallergen tested and 163/312 were sensitized to dust mites. 14 individuals were sensitized to snails and all 14 were sensitized to at least one aeroallergen. 13/14 of this group were sensitized to dust mite. 2 reported eating snail without reactions, 4 had suffered reactions and the others had never eaten snails.

        Pajno et al. (1994) [1740] reported positive SPT in 34/51 children, while no snail-positive reactions were obtained by using the same extract on 20 children without mite and snail allergies.

        Amoroso et al. (1988) [1743] reported that 61% of the 70 allergic subjects gave a positive SPT to snail extract while no snail-positive reactions were obtained by using the same extract on 30 subjects who were not allergic.

      IgE assay (by RAST, CAP etc)

      • Number of Studies:0
      • Food/Type of allergen:

        Guilloux et al. (1998) [1665] used the same extracts as used by Vuitton et al. (1998) [1664] for SPT. For immunodots, snail (H. aspera aspera) was pulverized and stirred for 2 hours in ammoniun bicarbonate at pH 8.0 with 1 mM EDTA at 4°C. The extract was centrifuged at 10000 x g for 30 minutes at 4°C and the supernatant filtered. Ammonium sulfate was then added (29.5g/100 ml.) and the solution stored at 4°C overnight. It was centrifuged at 10000 x g for 30 minutes at 4°C and the precipitate resuspended in water and dialysed at 4°C overnight with a 3.5 kDa cut-off membrane. The pH was adjusted to 7.0 and the solution was centrifuged. The supernatant was lyophilized and stored at -20°C.  

        Amoroso et al. (1988) [1743] boiled 500 g of snail (Euparipha pisana) for 10 minutes, separated the body from the shell and homogenised the body in distilled water. The mixture was centrifuged at 10000 x g for 10 minutes and the supernatant defatted with the same volume of ethyl ether at room temperature. The supernatant was then dialysed using an Amicon YM5 filter (5 kDa cut-off) and the protein concentration measured. 

      • IgE protocol:

        Martins et al (2005) [1663] used CAP-FEIA and immunoblotting.

        Asturias et al (2002) [1662] used the Hy-Tec IgE EIA assay (Hycor Biomedical, Irvine, Calif., USA) and immunoblotting.

        Guilloux et al. (1998) [1665] used ELISA, ELISA inhibition, and immunoblotting. 

        Van Ree et al. (1996) [1609] used RAST, RAST inhibition and immunoblotting.

        Pajno et al. (1994) [1740] used RAST inhibition.

        Amoroso et al. (1988) [1743] used RAST, RAST inhibition and immunoblotting.

      • Number of Patients:

        Martins et al (2005) [1663] tested sera from 60 patients who reacted to dust mites. 18 suffered asthma, 36 asthma, rhinitis and conjunctivitis, 3 from rhinitis and conjunctivitis, 2 from atopic eczema and 1 from irritative cough.

        Asturias et al (2002) [1662] tested sera from 22 snail allergic patients.

        Guilloux et al. (1998) [1665] tested sera from 7 snail allergic patients.

        Van Ree et al. (1996) [1609] tested sera from 29 patients.

        Pajno et al. (1994) [1740] tested sera from 4 patients.

        Amoroso et al. (1988) [1743] tested 70 subjects allergic to the more common allergens of the Mediterranean area and 30 subjects who were not allergic.

      • Summary of Results:

        Guilloux et al. (1998) [1665] reported that immunoblots showed specific IgE to snail in all 7 sera. Binding was inhibited by dust mite extract in 2 sera. 

        Van Ree et al. (1996) [1609] report that all 29 sera bound both dust mite and snail extracts. RAST results were similar for Helix aperta and the sea snail Bolinus brandaris. RAST to limpet (Patella spp.) was also similar. Snail RASTs were inhibited by mite except for a single serum. Mite RASTS were not strongly inhibited by snail.

        Pajno et al. (1994) [1740] reported that there was marked cross-reaction between dust mites and snails with a dust mite extract giving 100%, 97.6%, 69.3% and 95.6% RAST inhibition of binding to snail.

        Amoroso et al. (1988) [1743] reported that 13 (19%) of the 70 allergic subjects were RAST-positive to snail extract while none of the sera from the 30 subjects who were not allergic was RAST-positive.

      Immunoblotting

      • Immunoblotting separation:

        Martins et al (2005) [1663] used 8-18% gradient acrylamide SDS gels for both 1D- and 2D-separations. IEF used pH 3-10 and pH 2.5-6.5 ampholines (Pharmacia) in 4% acrylamide gels for 2D-separations and pH 2.5-6.5 in 0.7% agarose/0.9% sorbitol.

        Asturias et al (2002) [1662] used 12.5% SDS-PAGE in reducing conditions by the method of Laemmli (1970) [948].

        Guilloux et al. (1998) [1665] used 12% SDS-PAGE with 1% beta-mercaptoethanol for immuno blotting and 8-25% gradients for protein stained gels.

        Amoroso et al. (1988) [1743] used 8% SDS-PAGE.

      • Immunoblotting detection method:

        Martins et al (2005) [1663] transfered proteins to nitrocellulose (0.2µm) or PVDF membranes (Bio-Rad) in a Nova semi-dry system (Pharmacia). Membranes were cut into strips and blocked for 60 min. at room temperature with 1% (w/v) BSA, 0.1% (v/v) Tween 20 in PBS. The strips were incubated overnight with sera diluted 1:10 with blocking buffer. After washing four times with 0.1% (v/v) Tween 20 in PBS, strips were developed with 125I-anti-human IgE (Pharmacia) or using alkaline phosphatase labelled anti-IgE and NBT/BCIP (Sigma).

        Asturias et al (2002) [1662] electrophoretically transfered proteins to a PVDF membrane (Immobilon-P, Millipore). Membranes were incubated overnight with sera at 4°C diluted 1:4 or 1:10 (v/v). IgE binding was detected with anti-human IgE (Dako, Glostrup, Denmark) antibodies linked to horseradish peroxidase.

        Guilloux et al. (1998) [1665] transfered proteins to a nitrocellulose membrane (Schleicher and Schuell, 0.22µm) electrophoretically. The membrane was blocked for 60 min. at 37°C with 3% (w/v) BSA in buffer. The strips were washed with 0.05% (v/v) Tween 20 in PBS and incubated overnight with sera diluted 1:1 with BSA/PBS. After washing with 0.05% (v/v) Tween 20 in PBS, the strips were developed in 125I-anti-human IgE (Pharmacia). 

        Van Ree et al. (1996) [1609] transfered proteins to nitrocellulose membranes in a Novablot semi-dry system (Pharmacia). Membranes were cut into strips and blocked with 1.8% (w/v) BSA, 0.1% (v/v) Tween 20 in PBS.

        Amoroso et al. (1988) [1743] transfered proteins to a nitrocellulose membrane (Transblot 0.45µm) electrophoretically. The membrane was blocked by equilibration for 60 min. at 37°C in Phadebas RAST buffer with 0.5% (v/v) Tween 20. The membrane was cut into strips and equilibrated overnight with 500 µl of patient's serum diluted to 3 mls in RAST buffer with 0.5% (v/v) Tween 20. After washing, the strips were incubated in 125I-anti-human IgE (Phadebas RAST) 200,000 cpm/strip in 3 mls RAST buffer overnight at room temperature, dried and autoradiographed for 1,3 or 10 days.

      • Immunoblotting results:

        Martins et al (2005) [1663] report 1D-SDS-immunoblots with the 6 sera from snail allergic individuals with Theba pisana, Helix aspersa and Otala lactea extracts, 21 sera against Dermaphagoides pteronyssinus (dust mite) and Helix aspersa, and 2D-immunoblots with a pool of 15 sera and Helix aspersa extract. Similar IgE binding patterns were identified in different snail species. However, the IgE binding patterns were different for sera from different snail allergic individuals. Thus one serum from a snail allergic individual, which showed no RAST inhibition by mite, recognised a single major band >208 kDa. Sera from 2 snail allergic individuals showed related complex patterns with limited RAST inhibition by mite. The sera from the 3 remaining snail allergic individuals showed simpler immunoblots with bands >208 kDa and 151.5 kDa and significant (93.4%, 55.4% and 77.3%) RAST inhibition by mite. IgE from the 21 sera from mostly dust mite allergic individuals recognised 20 proteins from H. aspersa. Two H. aspersa bands >208 kDa were recognised by IgE from respectively 13 and 18 sera. A snail protein at 85 kDa was recognised by IgE from 8 sera and one from mite and snail at 58-60 kDa by IgE from 6 sera. IgE from only a single sera recognised a snail band at 37 kDa. The 2D-blots showed IgE binding to proteins at pI=3 and >208 kDa, at pI =3.5-4.0 and 150 kDa and pI=3.5-4.6 and 60 kDa. IEF immunoblots also showed that IgE from most sera bound to allergens at pI =3.4, 3.6, 3.8 and 6.3 although 27 IgE reactive bands were noted. The authors conclude that two myosin heavy chains were likely to be the major snail allergens. 

        Asturias et al (2002) [1662] report that 4/22 sera recognised natural and recombinant snail tropomyosin at 36 kDa. Other allergens were observed at 74, 67, 65, 45, 40, 34 and 29 kDa. A pool of the 4 tropomyosin binding sera also recognised 36 kDa proteins from clam, sea snail, octopus and shrimp and a 41 kDa protein from cuttlefish.

        Guilloux et al. (1998) [1665] found specific IgE against mite extracts in all sera. A strong IgE response was directed against a snail 49-53 kDa protein in sera from 6/7 individuals. This is similar to the mass of haemocyanin which had been suggested as a possible allergen by Morikawa et al. (1990) [1694] but Guilloux et al. (1998) note that unlike haemocyanin the 49-53 kDa allergen is apparently thermostable. The sera showed very variable responses with one sera binding to many bands with mite extract (12 listed) and also many bands with the snail extracts. Some IgE binding proteins were in the 33-36 kDa range associated with tropomyosin but these were mostly with the mite extracts. However, 2 patients with this binding pattern also showed symptoms with crustacea. >200 kDa IgE binding proteins were found to bind IgE more strongly in the snail extracts.

        Van Ree et al. (1996) [1609] observed IgE binding to multiple bands with a snail extract, mainly at 20-30 kDa and above 50 kDa. IgE from 2 sera bound an allergen at 35 kDa (and a third sera bound weakly) which also bound an anti-tropomyosin monoclonal. Serum IgE from 5 individuals recognised shrimp, including a strong and a weak reactor to tropomyosin. The weakly reacting serum and serum from a different individual recognised blue mussel by RAST.

        Amoroso et al. (1988) [1743] estimated the masses of allergens as >>66 kDa in 8 sera, >66 kDa in 2 sera, 66 kDa in the same 2 sera, 24 kDa in 9 sera, 15 kDa in 3 sera and 12 kDa in 6 sera.

      Oral provocation

      • Number of Studies:1-5
      • Food used and oral provocation vehicle:

        Pajno et al (2002) [1747] used capsules of opaque gelatin (Lofarma S.p.A., Milan, Italy) containing 40 mg of dried snail or dextrose. The starting dose of 40 mg was increased every 30 minutes until objective symptoms appeared or until a cumulative dose of 8 g had been administered.

        Vuitton et al. (1998) [1664] used a native snail extract prepared as described for skin tests.

        Pajno et al. (1994) [1740] used an open challenge with 30 g of cooked snails.

      • Blind:

        Pajno et al (2002) [1747] used double blind challenge.

        Vuitton et al. (1998) [1664] used labial challenge.

        Pajno et al. (1994) [1740] used open challenge.

      • Number of Patients:

        Pajno et al (2002) [1747] challenged 4 patients aged 9-13 years.

        Vuitton et al. (1998) [1664] challenged 13 children.

        Pajno et al. (1994) [1740] challenged 21 children of whom 15 had positive SPT with snail.

      • Dose response:Pajno et al (2002) [1747] reported reaction to snail at cumulative doses of 120 mg. and 400 mg.
      • Symptoms:

        Pajno et al (2002) [1747] challenged 4 patients before immunotherapy to cure dust mite allergy. 2 reacted to snail with respectively asthma, rhinitis and a 20% decrease of pulmonary function, and asthma with a 20% decrease of pulmonary function. The other 2 subjects did not react. Because of evidence for increased sensitization from SPT and recall urticaria, no challenges after immunotherapy were performed.

        Vuitton et al. (1998) [1664] report that 6/13 children reacted to a labial challenge with snails.

        Pajno et al. (1994) [1740] reported that 11 out of 15 children who were SPT positive with snail reacted to the challenge with at least 18% reduced FEV-1 by spirometry and cough and/or asthma (8 showed marked asthma). These 11 children showed additional symtoms including rhino-conjunctivitis in 4 children, urticaria in 2 children and erythema in 1 child. The 4 other SPT positive patients showed 2-10% reduced FEV-1 and the 6 SPT negative patients 1-5% reduced FEV-1.

      IgE cross-reactivity and Polysensitisation

      Allergy to snail is associated with 3 different types of cross-reactivity. The first is the well established cross-reactivity between crustacea, insects and molluscs due to tropomyosin. This is far the most important crustacean allergen and sera from shrimp allergic patients will generally bind to molluscan tropomyosins. However, only 10-20% of snail allergic patients react to tropomyosin (Martins et al, 2005 [1663]; Asturias et al, 2002 [1662]; Guilloux et al. 1998 [1665]; Van Ree et al. 1996 [1609]).

      Allergy to snail seems to be most frequently the result of cross-reactivity to dust mites which may be the primary sensitising agent (Sidenius et al. 2001 [1749]). The proportion of dust mite allergic patients reported to react to snail varies from study to study. Pajno et al. (1994) [1740] reported that nearly half of their dust mite allergic patients were allergic to snails by open challenge. A recent abstract reported that 18% of patients allergic to house dust mites (HDM) were sensitized to snails and 10% were sensitized to shrimps. HDM/snail cross-sensitization was more frequent in multi-sensitized atopic patients: 34/41 patients sensitized to snails had positive prick-tests to 2 or more than 2 allergens including HDM. It was not significantly correlated with either past immunotherapy to HDM or previous consumption of snails (Rame et al. 2002 [1762]). The much earlier article of Amoroso et al. (1988) [1743] reported that 60% of aeroallergen allergic patients were SPT positive to snail (only 19% showed positive RAST) and that 15% had suffered asthma after ingesting snail (the suggestion of a pollen-snail link might arise as many dust mite allergic individuals are also allergic to pollen). However, the study of Meglio et al. (2002) [1669] reported a dramatically lower level of skin reactivity to snail, prompting the suggestion that the extract used differed from other studies.

      Finally, some snail and other gastropod allergic individuals appear to be sensitized independently of dust mites or crustacea (Martins et al, 2005 [1663]). Amongst these individuals, cross-reactions can occur between abalone, limpet and snail which can be very serious or fatal (Wu & Williams, 2004) [1709].

      Other Clinical information

      There is a controversy associated with the effects of immunotherapy aimed at desensitising patients to house dust mites on their reactions to snails and other molluscs and crustacea.

      Van Ree et al. (1996) [1713] first reported that house-dust mite immunotherapy is accompanied by the induction of IgE against snail and shrimp. Out of 17 sera over a 14-20 month study, the average IgE response to snail showed a significant increase and this included two conversions from negative to strongly positive. The IgE response to snail (> 10% binding in a snail RAST) was confirmed by a positive skin prick test (SPT) for 6/10 patients. 2 patients also showed oral allergy syndrome on eating shrimp (Crangon crangon).

      Peroni et al. (2000) [1667] report the case of a 12-year-old girl who was sensitized to house dust mites and started immunotherapy. After several months the patient was taken to the hospital emergency room owing to severe anaphylactic reaction after ingestion of sea snails. She developed a generalized urticarial rash, difficulty in breathing, itching and swelling of the lips immediately after eating the snails; urticaria in the sites of previous IT injections was observed at the same time. The patient had eaten snails on previous occasions without showing any symptoms.

      Pajno et al (2002) [1747] reported that before immunotherapy was begun, the ingestion of snail repeatedly provoked immediate (within 30 minutes) symptoms in 4 children. The episodes were mild or moderate; they were always treated at home, and no hospitalization or emergency care was ever required. After immunotherapy was begun, the first inadvertent ingestion of snail caused all 4 patients to develop severe, life-threatening systemic reactions requiring emergency care assistance and even mechanical ventilation. In addition, the SPT reactions to snail showed increased wheal size.

      Meglio et al. (2002) [1669] reported, by contrast, that immunotherapy appeared to protect against food allergy to snails. They studied two groups of children. 101 who had never undergone immunotherapy with Der p and 82 who had undergone immunotherapy with Der p for at least 12 months (range 12–57 months, mean 29 months). 8/82 children had stopped immunotherapy and 74/82 were having immunotherapy at the moment of enrolment. Of the untreated group, 3/101 (3%) were positive to H. pomatia, and 5/101 (5%) to H. aperta. No group 2 child was positive either to H. pomatia, or to H. aperta. Overall, 35/183 children (19%) had previously eaten snails (19 children of group 1 and 16 of group 2), but only 2/183 (1.1%) developed clinical symptoms (vomiting and asthma with urticaria). Neither had received immunotherapy.  Antonicelli & Mariano (2003) [1670] commented that the SPT results were unreliable as the two children with symptoms had given negative SPTs and suggested that the test with commercial extract had poor sensitivity. Further that the data was inconsistent with other published data. Meglio (2003) [1748] replied that their results suggested that new sensitisation did not occur and was consistent with data suggesting worsening of pre-existing allergies to snail on immunotherapy.

      Asero (2005) [1746] studied 70 house dust mite allergic patients of whom 31 underwent a 3-year course of injection mite-specific immunotherapy. Both patients and controls reported the regular intake of crustaceans and/or molluscs. The author concluded that injection with house dust mite extracts does not seem to induce de novo tropomyosin sensitization. However, this study was aimed at testing if allergy to shrimp rather than snails developed.

      The different results above may be due to differences in the extracts used for the immunotherapy. van Hage-Hamsten & Valenta (2002) [1752] reviewed this and other data and argued that therapy based on natural extracts should be replaced by therapy using recombinant allergens modified to have low allergenicity. This approach appears to reduce oral allergy syndrome with foods using recombinant Bet v 1 derivatives (Niederberger et al. 2004 [1753]).

      The articles of Martins et al (2005) [1663], Asturias et al (2002) [1662], Guilloux et al. (1998) [1665] and Van Ree et al. (1996) [1609] clearly show that tropomyosin is a minor snail allergen and that allergens of >208 kDa mass are recognised by most sera from snail allergic patients. These are identified as the myosin heavy chains by Martins et al (2005) [1663] but no biochemical entry has been written as there is no sequence or molecular data from these allergens.

      Reviews (0)

        References (34)

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        Biochemical Information for Tropomyosin

        • Allergen Name:Tropomyosin
        • Alternatve Allergen Names:Hel as 1
        • Allergen Designation:Minor
        • Protein Family:Pfam PF00261; Tropomyosin family
        • Sequence Known?:Yes
        • Allergen accession No.s:http://www.expasy.org/uniprot/O97192
        • 3D Structure Accession No.:N/A
        • Calculated Masses:32637 Da
        • Experimental Masses:36 kDa
        • Oligomeric Masses:Tropomyosins form dimers.
        • Allergen epitopes:Not known
        • Allergen stability:
          Process, chemical, enzymatic:

          The allergenicity of tropomyosins can survive cooking, possibly because tropomyosin have a very simple helical structure which can rapidly refold after denaturation.

        • Nature of main cross-reacting proteins:

          Asturias et al (2002) [1662] report that a serum pool from the 4 individuals with IgE binding tropomyosin also recognised 36 kDa proteins from clam, sea snail, octopus and shrimp and a 41 kDa protein from cuttlefish.

          Van Ree et al. (1996) [1609] reported that sera from 5 of 28 snail allergic indivuduals recognised shrimp, including one of the 2 strongly tropomyosin binding sera and the sera which bound tropomyosin weakly. The weak binder and another sera also recognised blue mussel by RAST.

          The immunoblotting results of Lopata et al (1997) [1188] suggest that there is IgE cross-reactivity for tropomyosins between abalone and snail, white mussel, black mussel, oyster, and squid.
        • Allergen properties & biological function:Tropomyosins bind to actin in muscle increasing thin filament stability and rigidity. Depolymerization from the pointed end is inhibited, without affecting elongation (Broschat, 1990 [1589]). As tropomyosin prevents the binding of myosin, it may play an important role with troponin in controlling muscle contraction. The sequence exhibits a prominent seven-residue periodicity which is reflected in the interactions of the 2 polypeptide chains which form a coiled coil structure of two alpha-helices as originally proposed by Crick in 1952 (see the porcine structure 1C1G). Some tropomyosins are N-acetylated modifying the structure of the N terminal region and increasing the affinity for the thin filaments (Greenfield & Fowler, 2002 [1590]).
        • Allergen purification:

          Asturias et al (2002) [1662] purified natural tropomyosin from snail, H. aspersa, foot. Foot muscles were frozen in liquid nitrogen and ground in a mortar. An acetone powder was made and tropomyosin purified by isoelectric precipitation following the method of Smillie (1982). This was further purified on a Sepharose Q column equilibrated with 20 mM phosphate pH 7.0 and gave 33 mg from 44g of snail with a single band on Coomassie blue stained SDS-PAGE.

          Recombinant snail tropomyosin was expressed in E. coli using the pKN172 vector giving 5 mg/l of culture and was also purified to give a doublet at 36 kDa by SDS-PAGE.

        • Other biochemical information:Asturias et al (2002) [1662] report that 4/22 sera from snail allergic patients contain anti-tropomyosin IgE. Similarly, Van Ree et al. (1996) [1609] reported that 2/29 sera bound an allergen at 35 kDa (and a third sera weakly bound this allergen) which also bound an anti-tropomyosin monoclonal.

          Asturias et al (2002) [1662] report that the sequence of Helix aspersa tropomyosin, Hel as 1, is 84% identical to the tropomyosin sequence of abalone, 72% identical to scallop, 70% to mussel and 66%-63% to nematodes, mites, crustacea and insects.

        References (5)

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          Tropomyosin prevents depolymerization of actin filaments from the pointed end.
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          Tropomyosin requires an intact N-terminal coiled coil to interact with tropomodulin.
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        • Lopata AL, Zinn C, Potter PC.
          Characteristics of hypersensitivity reactions and identification of a unique 49 kd IgE-binding protein (Hal-m-1) in abalone (Haliotis midae).
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