Human serum substitution by artificial sera of scalable allergen reactivity based on polyclonal antibodies and chimeras of human FcγRI and IgE domains

Extract-Shaped Immune Repertoires as Source for Nanobody-Based Human IgE in Grass Pollen Allergy

The presence of allergen-specific IgE in serum is a biomarker for allergic disease. Specific IgE antibodies for research and diagnostics, however, remain scarce. In contrast to prototypic antibodies, camelid species have evolved single domains as moiety for antigen recognition. These so-called nanobodies represent a versatile platform for the development of diagnostic and therapeutic approaches. In this study, we aimed for generating nanobodies and derived IgE formats from an extract-shaped immune repertoire. Timothy grass pollen represents a complex, but well-defined mixture of individual allergens. Therefore, a repertoire library from a timothy grass pollen extract immunised llama was established. The selection by phage display yielded 3 nanobodies with immunoreactivity to the extract. IgE-like nanobody-based human IgE (nb-hIgE) antibodies were produced in mammalian cells and assessed in different immunoassays and commercial platforms. Immunoblotting and diagnostic ImmunoCap analysis of single timothy grass pollen allergens identified the major allergens Phl p 6 and Phl p 4 as targets. Assessment of immunoreactivity further documented significant molecular cross-reactivity with pollen extract of different grass species and variant presence of allergens within extracts of Pooideae grasses. In summary, our study shows that extract-based immunisation enables the generation of allergen-specific nanobodies and derived nb-hIgE formats linking nanobody technologies with allergological applications.

Standardizing In Vitro β-Lactam Antibiotic Allergy Testing with Synthetic IgE

The global prevalence of β-lactam allergy poses a major challenge in administering first-line antibiotics, such as penicillins, to a significant portion of the population. The lack of β-lactam IgE antibody pools with defined selectivity hampers the standardization and validation of in vitro assays for β-lactam allergy testing. To address this limitation, this study introduces a synthetic IgE specific to β-lactam antibiotics as a valuable tool for drug allergy research and diagnostic tests. Using phage display technology, we constructed a library of human single-chain antibody fragments (scFv) to target the primary determinant of amoxicillin, a widely used β-lactam antibiotic. Subsequently, we produced a complete human synthetic IgE molecule using the highly efficient baculovirus expression vector system. This synthetic IgE molecule served as a standard in an in vitro chemiluminescence immunoassay for β-lactam antibiotic allergy testing. Our results demonstrated a detection limit of 0.05 IU/mL (0.63 pM), excellent specificity (100%), and a four-fold higher clinical sensitivity (73%) compared to the in vitro reference assay when testing a cohort of 150 serum samples. These findings have significant implications for reliable interlaboratory comparison studies, accurate labeling of allergic patients, and combating the global public health threat of antimicrobial resistance. Furthermore, by serving as a valuable trueness control material, the synthetic IgE facilitates the standardization of diagnostic tests for β-lactam allergy and demonstrates the potential of utilizing this synthetic strategy as a promising approach for generating reference materials in drug allergy research and diagnostics.

Bispecific Single-Domain Antibodies as Highly Standardized Synthetic Calibrators for Immunodiagnosis

Commonly, serological immunoassays and diagnostic kits include reference standard reagents (calibrators) that contain specific antibodies to be measured, which are used for the quantification of unknown antibodies present in the sample. However, in some cases, such as the diagnosis of allergies or autoimmune diseases, it is often difficult to have sufficient quantities of these reference standards, and there are limitations to their lot-to-lot reproducibility and standardization over time. To overcome this difficulty, this study introduces the use of surrogate recombinant calibrators formulated on the basis of two single-domain antibodies (nanobodies) combined through a short peptide linker to produce a recombinant bispecific construct. One of the nanobodies binds to the cognate analyte of the target antibody and the second is specific for the paratope of the secondary detecting antibody. The bispecific nanobody inherits the outstanding properties of stability and low-cost production by bacterial fermentation of the parent nanobodies, and once calibrated against the biological reference standard, it can be reproduced indefinitely from its sequence in a highly standardized manner. As a proof of concept, we present the generation and characterization of two bispecific calibrators with potential application for the diagnosis of allergy against the antibiotics aztreonam and amoxicillin in humans.

Multiplexed analytical approaches to beta-lactam allergy in vitro testing standardization

The suspicion of beta-lactam allergy directly contributes to the prescription of antibiotics that diverge from the guidelines, increasing antimicrobial resistance, one of the biggest threats to global health. In vitro quantification of specific IgE is very useful for monitoring allergy, as it confirms or rules out immediate beta-lactam drug allergy and helps find safe alternative antibiotic stewardship. However, reliable in vitro quantification of specific IgE to beta-lactam antibiotics by immunoassay is challenging because of the difficulty of having selective immunoreagents, mainly beta-lactam antigens, and its low concentration levels in serum. Thus, reliable and sensitive in vitro tests for multiplex detection of allergy to different beta-lactam antibiotics is currently essential for clinical diagnosis. Nevertheless, the lack of standardization of quantitative in vitro methods makes the comparison and interpretation of the results difficult. Here, as proof of concept, we report an improved multiplex microimmunoassay for beta-lactam allergy in vitro testing standardization. The results revealed that homologous calibration allows reliable quantification of specific IgE in human serum at very low concentrations (144 ng L^-1). Moreover, the reproducibility of the results increases 2-fold using an internal standard, achieving accurate quantitative information: 93% and 106% recovery for penicillin and amoxicillin, respectively. We simultaneously evaluated the reliability of the improved multiplexed in vitro method in a cohort of 40 human serum samples and achieved excellent agreement (0.99) with a currently used in vitro test.

Evaluation of the manufacturer-dependent differences in specific immunoglobulin E results for indoor allergens

BACKGROUND

Even though allergies are an important health issue, the detected amount of allergen-specific IgE (sIgE) has differed widely between manufacturers in the past, and even as recently as this year. These discrepancies hinder diagnostics and can even impact allergen immunotherapy.

OBJECTIVE

The aim of this study was to evaluate the development and status quo of the quality of in vitro diagnostic testing for house dust mites (HDM) and cat epithelium, 2 important indoor allergen sources.

METHODS

We analyzed data on the allergen sources European HDM, American HDM, and cat epithelium, which were collected by the Society for Promoting Quality Assurance in Medical Laboratories (INSTAND e.V.) during 7 years as part of External Quality Assessment schemes (EQAs). A pseudoanonymized comparison was made of the semiquantitative data and allergen-class results of the 4 main suppliers of in vitro diagnostic sIgE tests. Coefficients of variation (CV) were determined in order to evaluate interlaboratory comparability.

RESULTS

In vitro allergy diagnostic testing for the major allergen sources HDM and cat epithelium still reveals manufacturer-dependent differences. Despite this, a cautious trend was found towards an alignment of the results and interlaboratory comparability, with the exception of 1 supplier.

CONCLUSION

Even though these results are promising, future EQAs have to be closely monitored to ensure this positive trend is not just a snapshot.