Detección de alérgenos alimentarios
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RETOS Y SOLUCIONES PARA LA DETECCIÓN DE ALÉRGENOS OCULTOS EN LOS ALIMENTOS JORNADA TÉCNICA DNSA 9 DE OCTUBRE
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Detección de alérgenos alimentarios
- 1. Teresa García Lacarra Nutrición y Ciencia de los Alimentos Facultad de Veterinaria
- 3. Diferencias regionales, edad Teresa García Lacarra (UCM) Teresa García Lacarra
- 4. Teresa García Lacarra (UCM) Teresa García Lacarra
- 5. Teresa García Lacarra (UCM) Teresa García Lacarra
- 6. < 20 mg/kg Gluten 20-100 mg/kg Gluten Teresa García Lacarra (UCM) Teresa García Lacarra
- 7. Teresa García Lacarra (UCM) Teresa García Lacarra
- 8. Teresa García Lacarra (UCM) Teresa García Lacarra
- 9. Teresa García Lacarra (UCM) Teresa García Lacarra
- 10. Alérgenos ocultos Presente en materia prima Contaminación cruzada Sustitución fraudulenta Teresa García Lacarra (UCM) Teresa García Lacarra
- 11. Teresa García Lacarra (UCM) Teresa García Lacarra
- 12. Teresa García Lacarra (UCM) Teresa García Lacarra
- 13. Teresa García Lacarra (UCM) Teresa García Lacarra
- 14. Retos de la detección de alérgenos Ausencia de umbrales de toxicidad de referencia Efecto del procesado / matriz Materiales certificados de referencia Detección múltiple Teresa García Lacarra (UCM) Teresa García Lacarra
- 15. Nieto et al. 2014 Hauser et al. OI: 10.1186/1710-1492-6-1 Teresa García Lacarra (UCM) Teresa García Lacarra
- 16. Detección de alérgenos Proteína Inmunológicos ELISA DFL Inmunosensores Físico-químicos Electroforesis LC-MS ADN PCR MLPA Genosensores Teresa García Lacarra (UCM) Teresa García Lacarra
- 17. Directo Competitivo Sandwich Limitaciones: Efecto matriz y procesado Reacciones cruzadas Anticuerpos animales Teresa García Lacarra (UCM) Teresa García Lacarra
- 18. Teresa García Lacarra (UCM) Teresa García Lacarra
- 19. Teresa García Lacarra (UCM) Teresa García Lacarra
- 20. Teresa García Lacarra (UCM) Teresa García Lacarra
- 21. Phagemid (genotype) scFv (phenotype) ANTIBODY FRAGMENTS LIBRARIES ANTICUERPOS RECOMBINANTES Teresa García Lacarra (UCM) Teresa García Lacarra
- 22. Teresa García Lacarra (UCM) Teresa García Lacarra
- 23. Teresa García Lacarra (UCM) Teresa García Lacarra
- 24. Biopanning Teresa García Lacarra (UCM) Teresa García Lacarra
- 25. LOD 102-103 mg kg-1 Teresa García Lacarra (UCM) Teresa García Lacarra
- 26. • Confirmación • Sensibilidad • Cuantitativo • Poco afectado por procesado • Detección múltiples alérgenos • Caro (Equipo, especialista, bases de datos) Teresa García Lacarra (UCM) Teresa García Lacarra
- 27. Inverso FDirecto SONDA Método indirecto Posible efecto matriz Sensibilidad Especificidad Estabilidad procesado Teresa García Lacarra (UCM) Teresa García Lacarra
- 28. Ara h 2 ITS (rDNA) 10 ppm 0,1 ppm Teresa García Lacarra (UCM) Teresa García Lacarra
- 29. (100 %) (93,3 %) (36,98 %) Teresa García Lacarra (UCM) Teresa García Lacarra
- 30. ALÉRGENO MARCADOR LOD (PPM) % TRAZAS % OCULTOS cacahuete Ara h 2 , ITS 10, 0,1 93 37 nuez de Brasil Ber e 1 2,5 7 10 almendra ITS 0,1 41 41 avellana ITS 0,1 72 45 pistacho ITS 0,1 13 20 nuez ITS 0,1 38 39 pacana ITS 0,1 15 14 anacardo ITS 0,1 42 20 macadamia ITS 0,1 22 15 Sésamo-Lino ITS 1,3 - 1,4 48 - 83 5 – 2 Girasol.Amapola ITS 0,1 33 - 75 22 - 7 (De la Cruz et al., 2013) (López-Calleja et al., 2013a) (López-Calleja et al., 2013b) (López-Calleja et al., 2014) (López-Calleja et al., 2015a) (López-Calleja et al., 2015b) (López-Calleja et al., 2016) (López-Calleja et al., 2015c) PCR en tiempo real Teresa García Lacarra (UCM) Teresa García Lacarra
- 31. LOD 0,1-100 mg kg-1 Teresa García Lacarra (UCM) Teresa García Lacarra Múltiplex Sensibilidad Ajuste complejo Equipo caro
- 32. Teresa García Lacarra (UCM) Teresa García Lacarra
- 33. ELISA Anticuerpos que reconocen proteínas o péptidos PCR Detecta ADN del alimento alergénico MS Detecta péptidos específicos Métodos más usados en detección de alérgenos Medios • Laboratorio • Prueba de campo Objetivo • Control oficial • Autocontrol ¿Qué busco? • Alérgeno(s) • Alimento ¿Cuál elegir? Teresa García Lacarra (UCM) Aumenta complejidad instrumental y precio Aumenta nivel de utilización Teresa García Lacarra
- 34. CONCLUSIONES • Peligro real de alérgenos ocultos • Retos por resolver – Materiales de referencia – Umbrales de toxicidad – Armonización de métodos – Detección múltiple • Gestión integral de alérgenos Teresa García Lacarra
- 35. Teresa García Lacarra (UCM) AGL2010-15279 AGL2013-48018-R AGL2017-84316-R Teresa García Lacarra
Notas del editor
- Las alergias alimentarias son una respuesta anómala del organismo a alimentos que de otro modo serian inofensivos, implicando al sistema inmunitario. Normalmente, nuestro sistema inmunitario nos defiende de sustancias posiblemente dañinas como las bacterias, los virus y las toxinas. Sin embargo, el sistema inmunitario de los individuos alérgicos identifica de forma incorrecta ciertos componentes de los alimentos como nocivos. La gravedad de una reacción alérgica puede variar entre individuos. Mientras que una persona puede necesitar dirigirse apresuradamente al servicio de urgencias mas próximo en cuestión de minutos por síntomas potencialmente mortales tras comer un alérgeno alimentario, otra puede manifestar solamente picor en la boca. La reacción puede ocurrir en minutos o unas pocas horas. Food allergy is a pathological, potentially deadly, immune reaction triggered by normally innocuous food protein antigens. The prevalence of food allergies is rising and the standard of care is not optimal, consisting of food-allergen avoidance and treatment of allergen-induced systemic reactions with adrenaline. (Yu, Nature reviews immunology 2016) 1. Definición y límites de la alergia alimentaria Se conoce como alergia alimentaria al conjunto de reacciones adversas a alimentos, debidas a su ingestión, contacto o inhalación, de patogenia inmunitaria comprobada. Sólo se produce en algunos individuos, puede ocurrir después de la toma de muy pequeñas cantidades del alimento y no se relaciona con ningún efecto fisiológico o fisiopatológico propios del mismo. El término “alergia alimentaria” se ha utilizado abusivamente, aplicándola de forma incorrecta a cualquier reacción adversa a un alimento o aditivo alimentario. 2. Clasificación Dentro de la alergia alimentaria se incluyen tanto las reacciones de patogenia inmunitaria mediadas por IgE (hipersensibilidad o alergia de tipo inmediato), como las producidas por cualquier otro mecanismo inmunitario conocido (reacciones no mediadas por IgE). Es característica de las primeras la presencia de títulos altos de anticuerpos de la clase IgE frente al alimento. En las segundas puede encontrarse aumento de anticuerpos específicos pertenecientes a otras clases de inmunoglobulinas, complejos inmunes y, más probablemente, respuestas de inmunidad mediada por células. También es posible la existencia de una participación mixta, es decir, reacciones parcialmente mediadas por IgE y por células, en grado variable. En cualquier caso, además de la evidencia de relación de dependencia entre la ingestión de un alimento y la aparición de síntomas, es necesario que estos parámetros inmunitarios alterados estén directamente involucrados en la fisiopatología responsable de los síntomas. Algunas enteropatías, como la enfermedad celíaca y otras enteropatías y enterocolitis por proteínas alimentarias (leche de vaca, arroz, pollo, soja, etc.), pueden estar incluidas dentro del concepto de alergia alimentaria, ya que en ellas está demostrada o es muy probable la existencia de un mecanismo inmunitario subyacente. EFSA2014: Coeliac disease is an autoimmune systemic disorder triggered by gluten in genetically susceptible individuals. It is a life-long disease with permanent gluten intolerance and is characterised by the presence of a variable combination of gluten-dependent clinical manifestations, coeliac diseasespecific antibodies, HLA-DQ2 or HLA-DQ8 haplotype, and a small intestinal mucosal lesion (enteropathy) (Marsh, 1992; Collin et al., 1994; Fasano and Catassi, 2001; Tack et al., 2010; Husby et al., 2012; Ludvigsson et al., 2013). Coeliac disease is strongly associated with HLA-DQ2 and DQ8 (Marsh, 1992; Sollid, 2002; Schuppan et al., 2009). Gluten peptides are presented by DQ2- and DQ8-positive antigen-presenting cells to immunocompetent cells of the small intestinal lamina propria. Tissue transglutaminase, which has also been identified as the important autoantigen in coeliac disease, is released and it may potentiate antigen presentation by deamidating or cross-linking gluten peptides (Schuppan et al., 2009). As a result, T-cell activation, cytokine production, mucosal inflammation and destruction evolve. As a secondary event, production of humoral antibodies to the autoantigen transglutaminase and to gluten/gliadin peptides occurs. Immune pathophysiology of coeliac disease involves innate and adaptive immunity. The mechanisms are different from IgE-mediated food allergy. As a consequence, the time course and clinical manifestations of the reactions are different.
- La alergia alimentaria es un problema de salud pública en auge que afecta a más de 17 millones de personas sólo en Europa. Tres millones y medio de los europeos que la padecen son menores de 25 años. El incremento más abrupto de las alergias alimentarias ocurre entre los niños y las personas jóvenes. Además, en Europa, la alergia alimentaria es la principal causa de anafilaxia en los niños de edades comprendidas entre 0 y 14 años.
- (EFSA2014) The prevalence of food allergies in developed countries is uncertain. The scarcity of studies available for some geographical areas and the use of different methodologies across studies to retrieve prevalence data are the main reasons for this uncertainty. The discrepancy between prevalence of perceived and confirmed food allergy among children and adults has been reported in several studies and two meta-analyses (Rona et al., 2007; Nwaru et al., 2014). In the second meta-analysis, the point prevalence was higher among children (6.9%; 95 % CI: 6.6–7.2 %)) than among adults (5.9 %; 95 % CI: 5.7–6.1 %)). However, when the diagnosis of food allergy was confirmed by a food challenge, the prevalence of food allergy in Europe was estimated to be only 0.9 % (95 % CI: 0.8–1.1 %), in both adults and children.
- Se conocen más de 160 alimentos que pueden producir alergias. Sin embargo, los alimentos que con mayor frecuencia producen alergias están relacionados con los hábitos alimentarios de las poblaciones. De este modo, en España los alimentos más comunes como causa de alergia en niños son el huevo, el pescado y la leche de vaca, mientras que las frutas, los crustáceos y los frutos secos tienen especial relevancia en adultos. EFSA2014: Several studies indicate that 75 % of allergic reactions among children are due to a limited number of foods, namely egg, peanut, cow’s milk, fish and various nuts. Among adults, fruits of the latex group (e.g. kiwi, banana), fruits of the Rosaceae family (e.g. apples, pears, prunes), vegetables of the Apiaceae family (e.g. carrot, celery), and various nuts and peanuts (Kanny et al., 2001; Sastre, 2010; Dupont, 2011; Gadermaier Gabriele et al., 2011) are responsible for 50 % of allergic reactions. The occurrence of food allergies requires susceptibility of the host and exposure to the allergen. Geographical variation in the prevalence of food allergy is due to differences in environmental (e.g. pollen exposure or differences in food habits) and individual factors. Sex, age, family history of atopy and the presence of other allergic diseases are among the individual factors considered important in the development of food allergy. Extrapolations of prevalence data on specific food allergies from a single European country to the entire European population are of limited accuracy owing to differences in genetic background, exposure to the offending foods and eating habits Actualmente, son 14 los grupos de ingredientes alergénicos, la mayoría de origen vegetal, que obligatoriamente deben declararse en el etiquetado de los productos alimenticios en la Unión Europea. No obstante, los continuos avances en la investigación sobre alergias alimentarias hacen que la importancia y prevalencia de estas patologías entre los consumidores tenga un carácter dinámico, es decir, que puedan emerger nuevos alérgenos, o que alérgenos reconocidos ganen o pierdan relevancia en función de los hábitos de consumo, la utilización de nuevos alimentos e ingredientes y el desarrollo de nuevas tecnologías de procesado y conservación. Para adaptarse a estos nuevos retos, las herramientas de gestión y detección de alérgenos alimentarios deben experimentar una continua evolución, y centrarse tanto en los ingredientes de declaración obligatoria, como en los alérgenos emergentes potencialmente peligrosos para la salud. The term food allergy is used to describe an adverse immune response to foods. Food allergic disorders include acute, potentially life-threatening allergic reactions, as well as chronic debilitating diseases such as atopic dermatitis or eosinophilic gastroenteropathies (Sicherer and Sampson, 2009). Although an allergy could be triggered by virtually any food, the “major allergens” responsible for most significant reactions include milk, egg, peanut, tree nuts, shellfish, fish, wheat, and soy. Most of these major food allergens share a number of common features such as being water-soluble glycoproteins of 10–70 kDa in size, and relatively stable to heat, acid, and proteases. Food allergy rates vary by age, local diet, and geographical area among other factors. Studies in the US have indicated an 18% increase in childhood food allergy from 1997 to 2007. Some childhood allergies are expected to be outgrown by age 5; however, there is an estimated 3.9% of children that are currently being affected (Branum and Lukacs, 2009). Food allergy is the most common cause of anaphylaxis as reported by the emergency departments of the United States and United Kingdom, which have registered an increase of more than threefold in the number of hospitalizations for food induced anaphylaxis (Sicherer et al., 2010). The current management of food allergy is limited to strict avoidance, nutritional counseling, and emergency treatment of adverse reactions. Although attempts to desensitize patients date back more than 100 years, there are not accepted therapies proved to accelerate the development of oral tolerance or to provide effective protection from unintentional exposures.
- Los alimentos alérgenos son inofensivos para la mayoría de los consumidores. Los consumidores con intolerancia o alergia a diversos alimentos pueden reaccionar ante cantidades distintas de sustancias alérgenas. Estas cantidades pueden variar considerablemente (de microgramos a gramos) dependiendo del nivel de tolerancia del individuo, de su estado de salud y su medicación. Algunos consumidores muy sensibles pueden reaccionar de forma adversa ante cantidades muy pequeñas (pocos microgramos). Aunque se ha trabajado mucho para determinar los umbrales sin efectos adversos con el fin de utilizarlos en la gestión del riesgo de la inocuidad de los alimentos, aún no se ha llegado a un acuerdo sobre los mismos, ya que las diferentes partes interesadas aún no han establecido como interpretar esta información en términos de salud pública. In 2011, an expert panel was assembled to establish appropriate Reference Doses for allergenic food residues as a part of the VITAL (Voluntary Incidental Trace Allergen Labeling) program of The Allergen Bureau of Australia & New Zealand (ABA). These Reference Doses would guide advisory labeling decisions for use on food labels. Individual NOAELs and LOAELs were obtained from clinical challenges of foodallergic subjects. Statistical dose-distribution models (log-normal, log–logistic, Weibull) were applied to the individual NOAELs and LOAELs for each allergenic food. The Reference Doses, in terms of mg of total protein from the allergenic food, were based upon either the ED01 (for peanut, cow’s milk), the 95% lower confidence interval of the ED05 (for wheat, soybean, cashew, shrimp, sesame seed, mustard, and lupine), or both (egg, hazelnut) using all appropriate statistical dose-distribution models. Reference Doses were established for 11 allergenic foods ranging from 0.03 mg for egg protein to 10 mg for shrimp protein. Reference Doses were not established for fish or celery due to poor model fits with existing data. Reference Doses were not established for other tree nuts beyond hazelnut and cashew because of the absence of data on NOAELs and LOAELs from individual subjects.
- Reference Dose –the protein level (total protein in milligrams from an allergenic food) below which only the most sensitive individuals (between 1% and 5% depending on the quality of the data set available) in the allergic population are likely to experience an adverse reaction Los alimentos alérgenos son inofensivos para la mayoría de los consumidores. Los consumidores con intolerancia o alergia a diversos alimentos pueden reaccionar ante cantidades distintas de sustancias alérgenas. Estas cantidades pueden variar considerablemente (de microgramos a gramos) dependiendo del nivel de tolerancia del individuo, de su estado de salud y su medicación. Algunos consumidores muy sensibles pueden reaccionar de forma adversa ante cantidades muy pequeñas (pocos microgramos). Aunque se ha trabajado mucho para determinar los umbrales sin efectos adversos con el fin de utilizarlos en la gestión del riesgo de la inocuidad de los alimentos, aún no se ha llegado a un acuerdo sobre los mismos, ya que las diferentes partes interesadas aún no han establecido como interpretar esta información en términos de salud pública. In 2011, an expert panel was assembled to establish appropriate Reference Doses for allergenic food residues as a part of the VITAL (Voluntary Incidental Trace Allergen Labeling) program of The Allergen Bureau of Australia & New Zealand (ABA). These Reference Doses would guide advisory labeling decisions for use on food labels. Individual NOAELs and LOAELs were obtained from clinical challenges of foodallergic subjects. Statistical dose-distribution models (log-normal, log–logistic, Weibull) were applied to the individual NOAELs and LOAELs for each allergenic food. The Reference Doses, in terms of mg of total protein from the allergenic food, were based upon either the ED01 (for peanut, cow’s milk), the 95% lower confidence interval of the ED05 (for wheat, soybean, cashew, shrimp, sesame seed, mustard, and lupine), or both (egg, hazelnut) using all appropriate statistical dose-distribution models. Reference Doses were established for 11 allergenic foods ranging from 0.03 mg for egg protein to 10 mg for shrimp protein. Reference Doses were not established for fish or celery due to poor model fits with existing data. Reference Doses were not established for other tree nuts beyond hazelnut and cashew because of the absence of data on NOAELs and LOAELs from individual subjects.
- Para proteger la salud de los consumidores alérgicos, la Unión Europea ha promulgado el Reglamento 1169/2011, sobre la información alimentaria facilitada al consumidor, que en su Anexo II, recoge 14 grupos de alimentos alergénicos que han de ser declarados de forma obligatoria en el etiquetado de los alimentos. También hay que señalar, que conforme a lo estipulado en el Real Decreto 126/2015, la presencia de ingredientes alergénicos es también de declaración obligatoria en alimentos que se presenten sin envasar al consumidor final y a las colectividades, en los envasados en los lugares de venta a petición del comprador, en los envasados por los titulares del comercio al por menor.
- Seguimiento de 157 pacientes alérgicos a alimentos durante un año en Holanda. 73 tuvieron 151 episodios por alimentos que no declaraban el alérgeno como ingrediente. Undeclared allergens at 'concerning' concentrations in packaged food are causing accidental allergic reactions, according to a study. "There is a perception that food allergens are no longer an issue," says one expert. "This is not the case.” Testing foods for which consumers reported experiencing an allergic reaction, the scientists found 37% of the 51 products analysed had between one and four 'culprit allergens' that, according to the ingredient declaration, were not present. All of the allergens detected are regulated in the EU and should have been declared. They also found anomalies in how manufacturers are using the precautionary allergen label (PAL). For instance, none of the six products that contained peanut allergens or the two products with egg had a PAL statement but the products that did warn consumers about the possible presence of peanut, egg and soy contained no allergens. Key messages: -A wide range of food products and different noningredient allergens were involved in accidental allergic reactions. -In particular, the unintentional presence of milk in food products would warrant more attention both in allergen and allergy management. -For the allergens detected, the estimated intake by patients was in almost all cases at doses of greater than the proposed reference dose for allergens.
- This chart plots the number of notifications reported on allergens since 2004. After a long period of stabilising numbers, the figures for 2015 show a substantial increase. Although a particular issue regarding almond allergen caused quite some concern in 2015 (see next paragraph), the sharp increase in notifications can be observed for quite a number of allergens In January, the United Kingdom contact point sent a RASFF news reporting that there had been a number of food recalls in the US and Canada of ground cumin and products containing ground cumin, due to contamination with peanut protein and almond protein. The ground cumin, exported to the US, was believed to have come from Turkey. In order to find out more about origin and distribution of potentially affected products, the UK contact point requested the ECCP to inform Infosan. It was considered a possibility that these nut proteins had been added to some batches as a form of adulteration of the spice. As a consequence, it was suggested that countries increase their sampling of such commodities. The ground cumin of Turkish origin was analysed both by ELISA and PCR analysis and returned an ELISA positive and a PCR negative result. The supplier had done a risk assessment and could not find any risk of cross-contamination of cumin with almond. During the audit of the company no evidence of almond presence was detected. The conclusion was that there had likely been a false positive reaction of the ELISA test, a conclusion which was later subscribed by the United Kingdom, which withdrew the notification. End of June, Spain notified the presence of almond in ground nutmeg and ground cinnamon from a Spanish producer and in August again in ‘cinnamon substitutes’. The activities for which the supplier was authorised included the preparation and packing of spice substitutes. The official control visit ascertained that the almond shell was used in preparing a product called ‘anti-caking agent for nutmeg substitute’, the labelling of which stated that vegetable flour was used without specifying that it was 100 % almond shell flour. The unlabelled almond shell notifications indicate the importance of careful and conscientious sourcing of raw materials in the food industry. This can not only avoid very costly recalls but is crucial to protect vulnerable consumers. What was also apparent from this episode is that risk assessment for allergens is not quite straightforward as there may be consumers that react to very low quantities, as was illustrated by some of the food poisoning cases.
- Más allá de la cantidad del alérgeno ingerido, la potencial intensidad de las reacciones clínicas depende, en gran medida, de la estabilidad de la proteína sensibilizante (Figura 2). Ello explicaría la existencia de diferentes perfiles de alergia a frutas rosáceas: por una parte, pacientes habitualmente del centro y norte de Europa en los que, en razón de la abundancia del abedul, la alergia a las frutas rosáceas se asocia con sensibilización a PR-10 o profilinas comunes en el polen de ese árbol y en las rosáceas. Como consecuencia de la labilidad de estas proteínas, estos pacientes sólo suelen manifestar reacciones locales, como síndrome de alergia oral. Por el contrario, la ausencia de abedules en el sur de Europa motiva que la proteína sensibilizante más común entre pacientes alérgicos a rosáceas de estas zonas suela ser la proteína de transferencia de lípidos, lo que explica la mayor severidad de las reacciones en estos casos,35 particularmente cuando comen frutas sin pelar. EFSA2014 Cross-reactivities Cross-reactions occur among proteins with high-sequence homology and/or with similar 3D structure or common epitopes. Both linear and conformational epitopes may induce cross-reactivity. In order to assess the potential IgE cross-reactivity of a protein with a known allergen, an identity > 35 % over an 80-amino acid window is currently recommended for further testing. Examples of highly cross-reacting allergen groups are the profilins and the LTPs, both generally regarded as panallergens (Bonds et al., 2008). Panallergens are defined as homologous molecules that originate from a multitude of organisms and cause IgE cross-reactivity between evolutionarily unrelated species (Hauser et al., 2010). Food allergy may occur following sensitisation to inhaled allergens, such as pollen. An example is the so called “pollen–food allergy syndrome”, which usually manifests as OAS, although systemic symptoms may occur. Many patients allergic to birch pollen become allergic to apples, hazelnuts, celery and carrots. These patients have specific IgE antibodies to Bet v 1 or Bet v 2 (profilin), the major birch pollen allergens. Non-specific LTP (nsLTPs) have been identified in most plant-derived foods and in pollen from several plants. Sensitisation to nsLTPs is characterised by geographic differences. While in the Mediterranean countries allergy to Rosaceae fruits is mostly associated with sensitisation to nsLTPs, in Northern Europe it is more often associated with sensitisation to birch pollen (Bet v 1). However, the co-presence of specific cross-reacting antibodies in patients’ serum does not indicate which came first: the pollen allergy or the food allergy (Hauser et al., 2010). Cross-reactions are also observed between pollen of Compositae (mugwort) and celery. Other examples of cross-reactivity include those between latex and fruits, dust mite and shrimp tropomyosin, and mould and spinach. All foods belonging to the latex group (e.g. chestnut, walnut, kiwi, banana, avocado) have defence proteins (chitinases) with a common “hevein” domain that is present in the latex prohevein and accounts for most cross-reactivities. IgE antibodies interact in vitro with N-glycans, i.e. carbohydrate moieties linked to proteins (asparagine). α(1–3)-fucose and β(1–2)-xylose are considered the major cross-reactive carbohydrate determinants (CCDs) in plants (Andersson and Lidholm, 2003). N-glycans may be shared by pollen, plants and insects, but these are different from N-glycans present in mammalian proteins. There is evidence that N-glycans may contribute to the allergenic potential of some foods (e.g. celery) (Bublin et al., 2003). However, the biological role of CCDs in triggering clinical symptoms is a matter for debate (Jin et al., 2008). In vitro techniques do not allow us to distinguish between dual sensitisation (i.e. synthesis of IgE against proteins in two different foods) and cross-reactivity (i.e. synthesis of IgE against proteins in one food, which also bind proteins in a second food). In cross-reactions to several foods, different allergens may be causing cross-reactivity between different pairs of foods, as observed with snail, mite and shrimp (van Ree et al., 1996b). Moreover, profilins from certain species have been shown to induce cross-reactive IgE antibodies (birch, celery and latex), whereas others induce species-specific IgE (Radauer and Breiteneder, 2006).
- The process requires a small amount of the suspected food to be liquefied in a suspension so that it can be injected using a filter syringe into a silicon-based plate, or chip, of microcapillaries. As the sample passes through tiny tubes of the microfluidic chip using capillary action, it travels through a beam of light from a LED source that is monitored by a specialized camera, which is also a product of the scientists’ work. The image captures Ara h 1 protein particles that fluoresce when they come in contact with the chemical properties of the suspension. Currently, the camera records the data and sends it to a computer to be analyzed and deciphered with a result being provided within 20 minutes, compared to a conventional lab test that takes up to four hours after a sample has been received. In a modification to provide an extremely portable system, research is underway to develop an app to enable results via a smartphone. Testing foods in the near future will be as convenient and prompt as holding the detector in one hand and a smartphone in the other so that a restaurant owner, for example, will be assured that dishes are allergen-free before being served to customers. Imitating the Human System for Detection To enable the allergen to fluoresce, the compound graphene oxide (GO) was utilized in combination with a bio-sensing component, known as an aptamer. The aptamer acts similarly to antibodies that identify and attach themselves to foreign and hostile elements that enter our blood system. Once a GO-aptamer mixture is attached to the allergen, the light source allows the protein particle to be detected and its image captured electronically. By altering an aptamer’s composition to identify other allergens, such as gluten, the detector is a versatile piece of scientific equipment for identifying potentially hazardous food ingredients. The developers of the technology are confident that their discovery will change the future of identifying potentially hazardous food components. The final step in the allergen detector’s development seems to be fine tuning the detection process for certain processed foods, such as roasted peanuts, that can alter the composition of Ara H 1 making it less obvious to be identified.
- The process requires a small amount of the suspected food to be liquefied in a suspension so that it can be injected using a filter syringe into a silicon-based plate, or chip, of microcapillaries. As the sample passes through tiny tubes of the microfluidic chip using capillary action, it travels through a beam of light from a LED source that is monitored by a specialized camera, which is also a product of the scientists’ work. The image captures Ara h 1 protein particles that fluoresce when they come in contact with the chemical properties of the suspension. Currently, the camera records the data and sends it to a computer to be analyzed and deciphered with a result being provided within 20 minutes, compared to a conventional lab test that takes up to four hours after a sample has been received. In a modification to provide an extremely portable system, research is underway to develop an app to enable results via a smartphone. Testing foods in the near future will be as convenient and prompt as holding the detector in one hand and a smartphone in the other so that a restaurant owner, for example, will be assured that dishes are allergen-free before being served to customers. Imitating the Human System for Detection To enable the allergen to fluoresce, the compound graphene oxide (GO) was utilized in combination with a bio-sensing component, known as an aptamer. The aptamer acts similarly to antibodies that identify and attach themselves to foreign and hostile elements that enter our blood system. Once a GO-aptamer mixture is attached to the allergen, the light source allows the protein particle to be detected and its image captured electronically. By altering an aptamer’s composition to identify other allergens, such as gluten, the detector is a versatile piece of scientific equipment for identifying potentially hazardous food ingredients. The developers of the technology are confident that their discovery will change the future of identifying potentially hazardous food components. The final step in the allergen detector’s development seems to be fine tuning the detection process for certain processed foods, such as roasted peanuts, that can alter the composition of Ara H 1 making it less obvious to be identified.