Quantification of Peach Fruit Allergen Lipid Transfer Protein by a Double Monoclonal Antibody-based Sandwich ELISA

Disposable electrochemical microfluidic device for ultrasensitive detection of egg allergen in wine samples

Food allergies have been increasing all over the world. Egg is an important component in the food industries and the second most common cause of food allergy, shortly after milk. In the wine industry, egg white is applied as a fining agent for tannin removal. In this study, a sandwich-based immunoassay for ultrasensitive detection of ovalbumin (OVA) in wine samples was developed. The assay involves the use of magnetic beads (MBs) decorated with a polyclonal anti-OVA antibody (Ab₂) and horseradish peroxidase (HRP), used as label for the quantification in a disposable electrochemical microfluidic device (DEμD) here developed. The Ab₂-MB-HRP prepared was applied to capture, separate, and pre-concentrate OVA from wine samples. In the DEμD, OVA was immune-magnetically captured (OVA-Ab₂-MB-HRP), producing a sandwich structure (GO-Ab₁-OVA-Ab₂-MB-HRP) on the electrode's surface. This arrangement results in an ultrasensitive device, achieving the ultralow limit of detection of 0.2 fg mL^-1 OVA. Five samples of wines were analyzed by using the immuno-magneto-assay which presents excellent accuracy compared with enzyme-linked immunosorbent assay (ELISA).

Peach allergen Pru p 1 content is generally low in fruit but with large variation in different varieties

Background

Pru p 1 is a major allergen in peach and nectarine, and the different content in varieties may affect the degree of allergic reactions. This study aimed to quantify Pru p 1 levels in representative peach varieties and select hypoallergenic Pru p 1 varieties.

Methods

To obtain monoclonal and polyclonal antibodies, mice and rabbits, respectively, were immunized with recombinant Pru p 1.01 and Pru p 1.02. The Pru p 1 levels in fruits from 83 representative peach varieties was quantified by sandwich enzyme-linked immunosorbent assay (sELISA). nPru p 1 was obtained through specific monoclonal antibody affinity purification and confirmed by Western blot and mass spectrometry. The variable Pru p 1 content of selected varieties was evaluated by Western blot and the expression level of encoding Pru p 1 genes by quantitative polymerase chain reaction.

Results

A sELISA method with monoclonal and polyclonal antibodies was built for quantifying Pru p 1 levels in peach. Pru p 1 was mainly concentrated in the peel (0.20-73.44 μg/g, fresh weight), being very low in the pulp (0.05-9.62 μg/g) and not detected in wild peach. For the 78 peach and nectarine varieties, Pru p 1 content varied widely from 0.12 to 6.45 μg/g in whole fruit. We verified that natural Pru p 1 is composed of 1.01 and 1.02 isoallergens, and the Pru p 1 expression level and Pru p 1 band intensity in the immunoblots were in agreement with protein quantity determined by ELISA for some tested varieties. In some cases, the reduced levels of Pru p 1 did not coincide with low Pru p 3 in the same variety in whole fruit, while some ancient wild peach and nectarines contained low levels of both allergens, and late-ripening yellow flesh varieties were usually highly allergenic.

Conclusion

Pru p 1 content is generally low in peach compared to Pru p 3. Several hypoallergenic Pru p 1 and Pru p 3 varieties, "Zi Xue Tao," "Wu Yue Xian," and "May Fire," were identified, which could be useful in trials for peach allergy patients.

Quantitative pharmacokinetic evaluation of Subtilisin QK-2 after a bolus IV injection in a rat model using a novel sandwich enzyme-linked immunosorbent assay

Intravascular thrombosis is a main cause of multiple cardiovascular diseases. A high thrombolytic activity of the microbial fibrinolytic enzyme Subtilisin QK-2, which is highly homologous to Nattokinase, shows great exploitable potential in thrombolytic therapy. However, the lack of a sensitive detection method limits the further analysis of Subtilisin QK-2 in vivo. We prepared a polyclonal antibody and four monoclonal antibodies (IgG1, titers of 1:500,000) to establish a sensitive sandwich ELISA for Subtilisin QK-2 detection. The limit of detection (LOD) of this ELISA was 1.160 ng/mL. The linear range of the standard curve was 1.96-250 ng/mL (R² = 0.9912). The cut-off value was 0.236. Subsequently, a pharmacokinetic dose (IV bolus) was administered and analyzed with the established ELISA. The concentration-time profiles were best fitted to a two-compartment model. T1/2α values for doses of 2 mg/kg, 4 mg/kg, and 8 mg/kg were 29.90 ± 10.02 min, 27.17 ± 1.96 min, and 21.83 ± 9.95 min, and T1/2β values were 144.43 ± 49.73 min, 173.46 ± 52.58 min, and 159.49 ± 48.75 min, respectively. Subtilisin QK-2 was eliminated through a mechanism with first-order kinetics. In conclusion, this study provides useful data for further research and clinical applications of Subtilisin QK-2 in the treatment of cardiovascular diseases.

Localization of Four Allergens in Artemisia Pollen by Immunofluorescent Antibodies

BACKGROUND

Artemisia pollens have a high potential to induce allergic symptoms. Seven allergen components have been identified, but only Art v 7 has been localized in the pollen grain. This study aimed to localize the allergens in the pollen grains of 4 Artemisia spp.

METHODS

Pollen extracts from 2 Chinese Artemisia spp., A. argyi and A. annua, were used to immunize BALB/c mice. Recombinant Art v 1 and Art v 3 allergens were used to select specific monoclonal antibodies (mAbs). Three mAbs were used to purify the natural allergens and were then analyzed by mass spectrometry. As reported previously, polyclonal antibodies were obtained from rabbits immunized with 3 synthesized peptides of Art an 7. Using conventional histology procedures with pollens from 4 Artemisia spp. (A. argyi, A. annua, A. capilaris, and A. sieversiana), allergen images were observed and recorded by fluorescence and confocal laser microscopy.

RESULTS

We obtained 2 specific mAbs against Art v 1, 1 against Art v 2, and 4 against Art v 3 homologs. The Art v 1 and Art v 3 homologs were mainly located on the pollen walls, and the Art v 7 homologous protein was localized intracellularly around nuclei. The location of the Art v 2 homologous protein varied across species, being intracellular around nuclei for A. annua and A. argyi, and in both the pollen wall and around nuclei for A. capilaris and A. sieversiana.

CONCLUSIONS

Four mugwort allergens were localized in the pollen, and the major Art v 1 and Art v 3 allergens were located mainly in the pollen wall.

Prunus genetics and applications after de novo genome sequencing: achievements and prospects

Prior to the availability of whole-genome sequences, our understanding of the structural and functional aspects of Prunus tree genomes was limited mostly to molecular genetic mapping of important traits and development of EST resources. With public release of the peach genome and others that followed, significant advances in our knowledge of Prunus genomes and the genetic underpinnings of important traits ensued. In this review, we highlight key achievements in Prunus genetics and breeding driven by the availability of these whole-genome sequences. Within the structural and evolutionary contexts, we summarize: (1) the current status of Prunus whole-genome sequences; (2) preliminary and ongoing work on the sequence structure and diversity of the genomes; (3) the analyses of Prunus genome evolution driven by natural and man-made selection; and (4) provide insight into haploblocking genomes as a means to define genome-scale patterns of evolution that can be leveraged for trait selection in pedigree-based Prunus tree breeding programs worldwide. Functionally, we summarize recent and ongoing work that leverages whole-genome sequences to identify and characterize genes controlling 22 agronomically important Prunus traits. These include phenology, fruit quality, allergens, disease resistance, tree architecture, and self-incompatibility. Translationally, we explore the application of sequence-based marker-assisted breeding technologies and other sequence-guided biotechnological approaches for Prunus crop improvement. Finally, we present the current status of publically available Prunus genomics and genetics data housed mainly in the Genome Database for Rosaceae (GDR) and its updated functionalities for future bioinformatics-based Prunus genetics and genomics inquiry.

A critical review of the specifications and performance of antibody and DNA-based methods for detection and quantification of allergens in foods

Despite the availability of a large number of antibody and DNA based methods for detection and quantification of allergens in food there remain significant difficulties in selecting the optimum technique to employ. Published methods from research groups mostly contain sufficient detail concerning target antigen, calibration procedures and method performance to allow replication by others. However, routine allergen testing by the food industry relies upon commercialised test kits and frequently the suppliers provide disappointingly little specification detail on the grounds that this is proprietary information. In this review we have made a critical assessment of the published literature describing the performance of both commercial and non-commercial test kits for food allergens over the period 2008-2018. Mass spectrometric methods, which have the potential to become reference methods for allergens, are not covered in this review. Available information on the specifications of commercial ELISA and LFD test kits are tabulated for milk, egg and peanut allergens, where possible linking to publications concerning collaborative studies and proficiency testing. For a number of commercial PCR test kits, specifications provided by manufacturers for detection of a small selection of allergen are tabulated. In conclusion we support the views of others of the critical need for allergen reference materials as the way forward to improve the comparability of different testing strategies in foods.

Type IV chitinase quantification in four different grape cultivars (Vitis vinifera) in northeast of Iran by an indirect sandwich enzyme-linked immunosorbent assay

The incidence of grape (Vitis vinifera) allergy in the northeast of Iran is second to melon allergy. Type IV chitinase is one of the major grape allergens. The current study investigates the level of type IV chitinase in four grape variants for the first time in Khorasan Razavi Province using a highly sensitive sandwich enzyme-linked immunosorbent assay (ELISA). This assay was developed using a polyclonal antibody as a capture antibody and monoclonal antibody as a secondary one. Finally, the amount of type IV chitinase was measured by the validated ELISA test. The sensitivity of the developed sandwich ELISA is 16 ± 0.05 ng/ml, and its mean coefficients of intraday and interday variations are <5% and <15%, respectively. The recovery of the designed ELISA is 64 ± 0.9 %. The assessments showed that the highest level of type IV chitinase was 39.7 ± 2.3 μg/g in Peykani grape, whereas in the Sultana cultivar, it was 1.76 ± 0.1 μg/g. According to the data, the level of type IV chitinase is variable in different cultivars, and hence, it will be helpful for clinicians to recommend a less allergenic variety to the patient.

Detection of allergen coding sequences of kiwi, peach, and apple in processed food by qPCR

BACKGROUND

Food traceability becomes lifesaving for persons suffering severe allergy or intolerance, and therefore need a complete avoidance of the immune-trigger food. This paper describes how to fingerprint the presence of some allergenic species (kiwi, peach, and apple) in foods by quantitative real-time PCR (qPCR).

RESULTS

Five DNA extraction procedures were tested on fruits and foods. The results were statistically evaluated, and discussed. Analysis by qPCR with SYBR Green was developed to detect traces of these allergenic species in foods. Plasmids containing the target sequences of kiwi, peach and apple were employed as internal reference standard. Analysis of spiked food samples showed a limit of detection of 25 mg kg^-1 for kiwi, 20 mg kg^-1 for peach and 50 mg kg^-1 for apple.

CONCLUSION

The qPCR method here developed, combined with the use of internal plasmid reference standard, represents a specific system for the quick detection of allergenic species in complex food matrices, with a limit of detection comparable with those reported using more time-consuming methods. © 2017 Society of Chemical Industry.

Significant Reduction of the Expression of Peach ( Prunus persica L. Batsch) Allergen-Encoding Genes by Fruit Bagging with Opaque Paper

Freshly consumed peaches ( Prunus persica L. Batsch) can cause allergic reactions in the worldwide population because of the presence of four classes of allergens (Pru p 1, Pru p 2, Pru p 3, and Pru p 4). Fruit bagging has been widely practiced in peach cultivation to improve fruit quality; however, its effect on the expression of peach allergen-encoding genes remains unknown. In this study, the influence of fruit bagging with opaque paper bags on the major peach allergen-encoding genes, including Pru p 1.01, Pru p 1.06B, Pru p 2.01B, Pru p 2.02, Pru p 3.01, Pru p 4.01, and Pru p 4.02, were measured by means of real-time PCR. A significant reduction in transcript accumulation was observed for all of the selected genes in the epicarps of the bagged peach fruits, whereas slight increases were observed in the mesocarps for these genes, with the two exceptions of Pru p 2.02 and Pru p 3.01. For most of these genes, much higher transcripts were determined in the epicarps than in the mesocarps. Taken together, a significant reduction in the transcription rate of the allergen-encoding genes in the whole peach fruit was achieved by shading with opaque paper bags. According to these data, modifications in growing practices of peach may help to obtain fruits with lower levels of allergens and thus contribute to reducing potential allergenic risks in consumers.

Acyl-CoA oxidase 1 is involved in γ-decalactone release from peach (Prunus persica) fruit

γ-Decalactone accumulation in peach mesocarp was highly correlated with ACX enzyme activity and natural PpACX1 content. Adding the purified recombinant PpACX1 induced γ-decalactone biosynthesis in cultured mesocarp discs in vitro. Previous gene expression studies have implied that acyl coenzyme A oxidase (ACX) is related to lactones synthesis, the characteristic aroma compounds of peach. Here, we analysed the correlation between γ-decalactone content and ACX enzyme activity in mesocarp of five different types of fully ripe peach varieties. Furthermore, 'Hu Jing Mi Lu' ('HJ') and 'Feng Hua Yu Lu' ('YL'), which have strong aroma among them, at four ripening stages were selected to study the role of ACX in lactone biosynthesis. The result showed that γ-decalactone was the most abundant lactone compound. γ-Decalactone accumulation was highly correlated with ACX enzyme activity. Mass spectrometry (MS) showed that PpACX1 was the most abundant PpACX protein in fully ripe mesocarp of cv. 'HJ'. To further elucidate the function of the PpACX1 protein, the PpACX1 gene was heterologously expressed in a bacterial system and characterized in vitro. MS identification gave the molecular weight of the recombinant PpACX1 as 94.44 kDa and the coverage rate of the peptide segments was 47.3%. In cultured mesocarp discs in vitro, adding the purified recombinant PpACX1 and C₁₆-CoA substrate induced the expected γ-decalactone biosynthesis. Using a sandwich ELISA based on mixed mono- and polyclonal antibodies against recombinant PpACX1, PpACX1 content in mesocarp was found to be highly correlated with γ-decalactone accumulation in mesocarp of five fully ripe varieties and four ripening stages of 'HJ' and 'YL'. This study revealed the vital function of PpACX1 in γ-decalactone biosynthesis in peach fruit.