Real-life evaluation of molecular multiplex IgE test methods in the diagnosis of pollen associated food allergy

Multiplex Assays in Allergy Diagnosis: Allergy Explorer 2 versus ImmunoCAP ISAC E112i

ImmunoCAP ISAC E112i (ISAC) and Allergy Explorer 2 (ALEX2) detect specific immunoglobulin E (IgE) reactivity. Both multiplex assays contain molecular allergens and ALEX2 additionally includes allergen extracts and inhibitors that block the binding of IgE to cross-reacting carbohydrate determinants (CCDs). This study aimed to compare the performance of ISAC and ALEX2 by determining the IgE reactivity against allergen extracts and/or allergen components and by using qualitative, semiquantitative, and quantitative analyses of all comparable allergen components in sera from 216 participants recruited in South Tyrol/Italy. For extract sensitization in ALEX2, the analysis revealed negative corresponding allergen components in 18.4% and at least one positive corresponding allergen component in 81.6% of all cases. For ISAC, the corresponding results were 23.5% and 76.5% of cases, respectively. The ALEX2 CCD inhibitor eliminated CCD-positive signals detected by ISAC in 88.5% of cases. Based on sensitization values of 0.3-14.9 ISU or kUA/L, there was good agreement between ALEX2 and ISAC, although ALEX2 showed higher values than ISAC. The addition of allergen-extract tests in ALEX2 resulted in the detection of more sensitizations than with corresponding allergen components alone. In the range of <15 ISU or kUA/L, ALEX2 may be more effective in detecting sensitizations.

Recombinant PreS-fusion protein vaccine for birch pollen and apple allergy

BACKGROUND

IgE cross-sensitization to major birch pollen allergen Bet v 1 and pathogenesis-related (PR10) plant food allergens is responsible for the pollen-food allergy syndrome.

METHODS

We designed a recombinant protein, AB-PreS, consisting of non-allergenic peptides derived from the IgE-binding sites of Bet v 1 and the cross-reactive apple allergen, Mal d 1, fused to the PreS domain of HBV surface protein as immunological carrier. AB-PreS was expressed in E. coli and purified by chromatography. The allergenic and inflammatory activity of AB-PreS was tested using basophils and PBMCs from birch pollen allergic patients. The ability of antibodies induced by immunization of rabbits with AB-PreS and birch pollen extract-based vaccines to inhibit allergic patients IgE binding to Bet v 1 and Mal d 1 was assessed by ELISA.

RESULTS

IgE-binding experiments and basophil activation test revealed the hypoallergenic nature of AB-PreS. AB-PreS induced lower T-cell activation and inflammatory cytokine production in cultured PBMCs from allergic patients. IgG antibodies induced by five injections with AB-PreS inhibited allergic patients' IgE binding to Bet v 1 and Mal d 1 better than did IgG induced by up to 30 injections of six licensed birch pollen allergen extract-based vaccines. Additionally, immunization with AB-PreS induced HBV-specific antibodies potentially protecting from infection with HBV.

CONCLUSION

The recombinant AB-PreS-based vaccine is hypoallergenic and superior over currently registered allergen extract-based vaccines regarding the induction of blocking antibodies to Bet v 1 and Mal d 1 in animals.

Allergen Stability in Food Allergy: A Clinician's Perspective

PURPOSE OF REVIEW

The globally rising food allergy prevalence is associated with the urgent need for new disease prevention methods, efficient treatment, and reliable risk assessment methods for characterization of food allergens. Due to inter-individual variations in the digestive system, food allergens are degraded to a different extent in each person. Food processing also influences allergen digestion.

RECENT FINDINGS

In this review, we provide an overview of the digestive system with focus on relevance for food allergy. Main food proteins causing allergic reactions are evaluated, and the combined role of food processing and digestion for allergen stability is highlighted. Finally, clinical implications of this knowledge are discussed. Recent literature shows that allergen digestibility is dependent on food processing, digestive conditions, and food matrix. Digestion affects proteins allergenicity. It is currently not possible to predict the immunogenicity of allergens solely based on protein stability.

Evolution Toward Chip-Based Arrays in the Laboratory Diagnosis of Human Allergic Disease

Multiplex-based specific IgE antibody assays have emerged into the clinical immunology laboratory through the combined use of pure, recombinant allergenic molecules and new methods to simultaneously and accurately analyze specific IgE antibodies to hundreds of allergens. This review traces the historical development and examines outstanding questions related to the strengths and limitations of these new molecular allergen multipex technologies for the assessment of human allergic sensitization. Multiplexed technologies are poised to provide the most cost-effective and comprehensive evaluation of patients with suspected allergy as compared with the commonly used singleplex autoanalyzers. How analytically sensitive and quantitative are the multiplex technologies, down to 0.1 kUA/L? Because each allergen is viewed as a unique assay, how will analytical and clinical performance be documented at the manufacturing and clinical laboratory levels to guarantee reproducibility and obtain government regulatory clearance? Will interference by naturally occurring allergen-specific IgG compromise analytical performance? Successful resolution of these and other questions covered in this review will position multiplex technologies to become the single most-effective means of screening patients for allergic sensitization, assessing IgE antibody cross-reactivity, and planning therapy directed at the patient with allergy.

Promises and Remaining Challenges for Further Integration of Basophil Activation Test in Allergy-Related Research and Clinical Practice

More than 20 years after having been initially proposed, the relevance and usefulness of basophil activation test (BAT) for the field of allergy research and testing were demonstrated on many occasions. Leveraging the fully open format of a flexible, whole blood-based functional assay, BAT has been shown to be equally important for fundamental research, clinical research, and diagnosis. Regardless of whether the focus of a study is on the characterization of the allergenic moiety, on the patient side, or on the study of the fundamental processes involved in the allergic disease or its treatment, BAT enables the gathering of very important insights. In spite of this, its full capabilities have yet to be leveraged. Various bottlenecks, including but not limited to assay logistics, robustness, flow cytometry access, and/or expertise, have indeed been limiting its development beyond experts and long-term users. Now, various initiatives, aiming at resolving these bottlenecks, have been launched. If successful, a broader use of BAT could then be contemplated. In such a situation, its more thorough integration in clinical practice has the potential to significantly change the allergic patient's journey.

Would the choice of multiplex platform impact the management of the allergic patient? A first approach focusing on LTPs

BACKGROUND

In the Mediterranean area, patients with LTP syndrome who are sensitized to multiple allergens are often tested for sIgE using multiplex platforms. The results obtained from different commercial platforms are not interchangeable, so it is important to compare and validate the platform selected for use. The objective of this study is to compare and validate the performance of the ImmunoCAP ISAC E112i and the macroarray ALEX2 in our daily practice.

METHODS

From August 2021 to March 2022, we tested 20 random serum samples from polysensitized patients using the ALEX2 test (MADx) and ImmunoCAP tIgE and ISAC E112i (Thermo Fisher Scientific). We compared the total IgE (tIgE) and sIgE levels for shared allergens.

RESULTS

The heatmap generally showed more intense results for ISAC. The overall correlation was good, but some exceptions were noted. The main discrepancies were found for Ole e 7, which was positive for 11 patients in ISAC but negative for all patients in ALEX2, and for nut LTPs, for which ISAC showed a threefold higher detection rate for Ara h 9 and a fivefold higher detection rate for Cor a 8 and Jug r 3 compared to ALEX2. The regression model showed no interchangeability of tIgE results.

CONCLUSIONS

Despite our small sample size and the complexity of comparing a quantitative and a semi-quantitative platform, our results suggest that patient diagnosis and management can be influenced by the platform used. Therefore, our findings must be taken into consideration when choosing a platform to use for some profiles of LTP-polysensitized patients, even though more data is needed.

Selected Technical Aspects of Molecular Allergy Diagnostics

Diagnosis of allergic diseases is a complex, multi-stage process. It often requires the use of various diagnostic tools. The in vitro diagnostics (IVD), which includes various laboratory tests, is one of the stages of this process. Standard laboratory tests include the measurement of the serum concentration of specific immunoglobulin E (sIgE) for selected allergens, full allergen extracts and/or single allergen components (molecules). The measurement of IgE sIgE to the allergen components is called molecular allergy diagnosis. During the standard laboratory diagnostic process, various models of immunochemical tests are used, which enable the measurement of sIgE for single allergens (one-parameter tests, singleplex) or IgE specific for many different allergens (multi-parameter tests, multiplex) in one test. Currently, there are many different test kits available, validated for IVD, which differ in the method type and allergen profile. The aim of the manuscript is to present various technical aspects related to modern allergy diagnostics, especially in the area of molecular allergy diagnostics.