Enhanced quantitation of egg allergen in foods using incurred standards and antibodies against processed egg in a model ELISA.

Underestimation of egg allergen from processed foods prompted the evaluation of critical Enzyme-Linked Immunosorbent Assay (ELISA) parameters: (1) extraction of egg proteins from a processed matrix; (2) use of anti-heat processed egg antibodies (Abs) on detectability of modified proteins, and (3) utilization of incurred material as standards. The relative affinity of two combinations of raw (R), boiled (B) and fried (F) Abs to unprocessed/processed egg proteins with or without matrix was determined from antibody (Ab) binding curves. In ELISAs using RBF-Abs and BF-Abs, denaturing buffer, and incurred standards, the Limit of Detection (LOD) and Limit of Quantitation (LOQ) were 0.47 and 0.25; and 1.58 and 0.85, respectively, and the linear range was 0-24 µg g-1 egg protein. The recoveries of egg protein from cookies, cereal bar, and muffin (incurred levels 4.8-48 µg g-1) with the developed ELISAs were in an acceptable range (50-130%). These ELISAs consistently detected more declared/undeclared egg proteins in market samples compared to assays using PBS for extraction. Overall, better assay performance was observed using BF-Abs. An ELISA combining anti-processed egg Abs, denaturing buffer, and incurred standards promises improved quantitation of egg proteins in processed foods.

Diet-induced obesity precipitates kidney dysfunction and alters inflammatory mediators in mice treated with Shiga Toxin 2.

Shiga Toxin (Stx)-producing E. coli (STEC) continue to be a prominent cause of foodborne outbreaks of hemorrhagic colitis worldwide, and can result in life-threatening diseases, including hemolytic uremic syndrome (HUS), in susceptible individuals. Obesity-associated immune dysfunction has been shown to be a risk factor for infectious diseases, although few studies have addressed the role of obesity in foodborne diseases. We hypothesized that obesity may affect the development of HUS through an alteration of immune responses and kidney function. We combined diet-induced obese (DIO) and HUS mouse models to look for differences in disease outcome between DIO and wild-type (WT) male and female C57 B l/6 mice. Following multiple intraperitoneal injections with endotoxin-free saline or sublethal doses of purified Stx2, we examined DIO and WT mice for signs of HUS development. DIO mice receiving Stx2 injections lost more body weight, and had significantly higher (p < 0.001) BUN, serum creatinine, and neutrophil counts compared to WT mice or DIO mice receiving saline injections. Lymphocyte counts were significantly (p < 0.05) lower in Stx2-treated obese mice compared to WT mice or saline-treated DIO mice. In addition to increased Stx2-induced kidney dysfunction, DIO mouse kidneys also had significantly increased expression of IL-1α, IL-1ß, IL-6, TNF-α, MCP-1, and KC RNA compared to saline controls (p < 0.05). Serum cytokine levels of IL-6 and KC were also significantly higher in Stx2-treated mice compared to saline controls, but there were no significant differences between the WT and DIO mice. WT and DIO mice treated with Stx2 exhibited significantly higher degrees of kidney tubular dilation and necrosis as well as some signs of tissue repair/regeneration, but did not appear to progress to the full pathology typically associated with human HUS. Although the combined obesity/HUS mouse model did not manifest into HUS symptoms and pathogenesis, these data demonstrate that obesity alters kidney function, inflammatory cells and cytokine production in response to Stx2, and may play a role in HUS severity in a susceptible model of infection.

Undeclared Food Allergens and Gluten in Commercial Food Products Analyzed by ELISA.

Undeclared allergen(s) in commercial food products are responsible for many food recalls, as reported by regulatory agencies in various countries, including the United States. Correct allergen labeling practices are essential for the safety of food-allergic consumers. However, this practice may be hindered by the introduction of allergens all along the food supply chain, including unintentionally through cross-contact. To understand the pervasiveness of undeclared allergen(s) in commercial food products, the objective of this review is to summarize the prevalence of undeclared milk, egg, hazelnut, peanut, soy, and gluten as detected by ELISA from previously published surveys. The prevalence of undeclared allergen(s) in products with or without an advisory statement was also summarized and compared. As compiled by this review, there are some food categories that may be at higher risk for containing undeclared allergen(s). However, the data on prevalence and amount of allergen present may vary widely within any particular allergen or food category. Factors, such as food survey product selection, geography, awareness of allergen/gluten issues, and/or the choice of ELISA method, may be responsible for such differences.

Survey of undeclared soy allergen levels in the most frequently recalled food categories with or without precautionary labelling.

A comprehensive study was designed to determine the frequency and levels of soy allergen in packaged bakery and snack food products. A representative sample of products with no soy allergen disclosed on the label was analysed using two widely used enzyme-linked immunosorbent assay (ELISA) methods. Samples were chosen that either had no soy identified on the product label or which had a soy precautionary statement. Among 558 bakery and snack products, soy protein was detected in 17% of the products using the Neogen (NE) kit and 11% of the products using the Elisa Systems (ES) kit. The disagreement rates between kits were 8.8% for bakery products and 3.3% for snack products. Overall soy protein was detected at higher frequency in bakery products than in snack foods. Among 284 bakery samples, soy protein was detected in 25% of the samples with no precautionary statement and 19% of the samples which had a precautionary statement. Among 274 snack samples, soy protein was detected in 11% of the samples with no precautionary statement and 9% of the samples which had a precautionary statement. The sample repeatability was at an acceptable level (< 9%) for each method and food commodity. The reproducibility between kits was 23% for bakery foods and 36% for snack foods. None of the bakery (21) and snack (6) products without precautionary labelling (measured level > 5 ppm) had a higher level of soy protein per serving compared with the eliciting dose10 (ED10) of 10.6 mg for soy allergic patients. But the level of soy protein per serving may be clinically relevant to a subpopulation of soy allergic patients if a more stringent eliciting dose is applied. These findings emphasise that suitable detection methodologies and references doses are crucial for labelling accuracy and the safety of soy allergic consumers.

Survey of undeclared egg allergen levels in the most frequently recalled food types (including products bearing precautionary labelling).

Since the number of recalls involving undeclared allergens is commonly associated with bakery and snack foods, we aimed to determine the frequency of egg allergens in a large number of these products using two commercial enzyme-linked immunosorbent assay (ELISA) methods. Samples were chosen that either had no egg identified on the product label or which had an egg precautionary statement. Among all samples, egg protein was detected in 5% of products using a Morinaga (MO) kit and 1% of products using a R-Biopharm (RB) kit. For bakery samples, egg protein was detected in 6% of 363 samples with no precautionary labelling (6% by MO and 1% by RB kit) and 12% of 80 samples which had precautionary labelling. For snack samples, egg protein was detected in 2% of 371 samples with no precautionary labelling (2% by MO and < 1% by RB kit) and 5% of 21 samples which had precautionary labelling. The disagreement rates between two methods were 5.2% for bakery products and 2.6% for snack products. The sample repeatability was at an acceptable level for bakery (< 12.5%) and snack foods (< 7.5%) for each method. The relative standard deviation between test kits was high (103.1%) for bakery foods. Four bakery products without precautionary labelling had a higher level of egg protein per serving compared with the eliciting dose (ED10 of 3.7 mg protein) for egg allergic patients. These results highlight the fact that detection methodology plays a vital role for accurate labelling control and mitigation of risk for egg allergic consumers.

In vitro digestibility and immunoreactivity of bovine milk proteins.

Current models of digestibility solely utilize pepsin stability to assess the safety of allergenic food proteins. However, in vivo complete protein digestion requires acid denaturation and pepsin, trypsin, and/or chymotrypsin cleavage. This study aimed to identify the immunoreactivity and allergenicity of stable bovine milk proteins, using an improved digestibility model to simulate physiological gastric and intestinal conditions in vitro. Gel electrophoresis and immunoblot analysis were used to determine protein stability and immunoreactivity, respectively. Immunoreactivity of bovine milk proteins, ß-lactoglobulin (ß-LG) and casein (CN) was greatly diminished with gastric simulation (0-60 min), but some proteins were stable and immunoreactive with simulated intestinal digestive conditions (0-60 min). This study demonstrates the need for improved digestibility models for more accurate assessment of the behavior of food allergens in vivo.

Digestibility and Immunoreactivity of Shrimp Extracts Using an In Vitro Digestibility Model with Pepsin and Pancreatin.

UNLABELLED: Shellfish allergy affects 2% of the adult population in the United States. Identification of allergenic shrimp proteins is needed for improved management and assessment of shrimp allergy. We determined the temporal pepsin and pancreatin stability of total shrimp proteins using simulated physiological digestive conditions in vitro. Gel electrophoresis was used to determine protein stability, whereas immunoreactivity of protease stable proteins was determined using rabbit antigen-specific antibodies. Potential allergenicity of protease stable proteins was determined utilizing human sera from shrimp allergic patients. Total shrimp myofibrillar proteins were pepsin- and pancreatin-stable for up to 1 h after initiating digestion, whereas only pancreatin-stable total shrimp proteins were Immunoglobulin G (IgG) immunoreactive. However, shrimp proteins of 32 and 25 kDa were pepsin and/or pancreatin stable and Immunoglobulin E (IgE) reactive, denoting the stability and potential allergenicity. These findings suggest that this in vitro digestibility model may be useful for the identification of shrimp allergenic proteins that are more resistant to physiologic digestive conditions and may elicit an immunologic response in vivo. PRACTICAL APPLICATION: Unlike other food allergies, shellfish allergy is typically life-long and predominantly affects the adult population. A major difficulty in managing shellfish allergy is the lack of reliable diagnostic assays due to limited knowledge of clinically relevant shellfish allergens. Therefore, the identification and characterization of digestive-stable and immunoreactive food proteins is fundamental to the development of new polyclonal antibodies for improved food allergen detection methods within the food industry.