Immunoassays for indoor allergens

New dot-blot method for evaluating the effect of inactivators on mite and Japanese cedar pollen allergens

As a method of evaluating the effect of inactivators on allergens while suppressing the effect of inactivator on the assay, we developed new dot-blot method that combines immunostaining and protein detection methods. This method is useful for evaluating whether the inactivator can inactivate allergens rather than removing them from the assay.

Development of Mold Antigen-Specific Enzyme-Linked Immunosorbent Assays (ELISA) to Quantify Airborne Antigen Exposure

Common methods to quantify molds in the environment are based on the detection of viable and nonviable fungal components using cultivation technique or assessment by microscopy. These methods are time consuming and laborious and require a high expertise and especially in airborne exposure studies they showed poor reproducibility. Therefore alternative techniques based on molecular or immunological tools attract wide interest. The development of specific ELISAs based on polyclonal antibodies to detect mold antigens in airborne samples starting with the extraction of the antigen material up to evaluation of the sandwich ELISA is summarized in this chapter.

Levels of horse allergen Equ c 4 in dander and saliva from ten horse breeds

BACKGROUND

Horses are an important source of allergens, but the distribution of horse allergens is poorly understood. Five horse allergens have been identified, Equ c 1-4 and 6. Equ c 4 seems to be an important allergen, with an IgE-binding frequency of 77% in horse-sensitized individuals.

OBJECTIVES

The aim of this study was to investigate levels of horse allergen Equ c 4 in dander, saliva and urine from ten horse breeds.

METHOD

The study population included 170 horses (87 mares, 27 stallions, 56 geldings) from ten breeds. Horse dander, saliva and urine samples were collected. Levels of horse allergen Equ c 4 were quantified using a two-site sandwich ELISA (mAb 103 and 14G4) and were expressed as Equ c 4 U/μg protein.

RESULTS

The horse allergen Equ c 4 was present in all dander and saliva samples from ten horse breeds, with high within-breed and inter-breed variations; GM values were 639 Equ c 4 U/μg protein (range 5-15 264) for dander and 39.5 (4-263) for saliva. Equ c 4 was found in 19/21 urine samples. Adjusted for age, sex and changes over time, no differences between breeds could be seen in dander, while in saliva the North Swedish horse showed lower levels of Equ c 4 than any other breed. The levels of Equ c 4 protein in dander and saliva were significantly higher in samples from stallions compared to mares and geldings, independent of breed.

CONCLUSIONS AND CLINICAL RELEVANCE

The results show a high variability in allergen levels of Equ c 4 in dander and saliva both within and between breeds. Significantly higher levels were found in stallions compared to mares and geldings, independent of breed. Results suggest that none of the horse breeds studied can be recommended for individuals allergic to Equ c 4.

Animal allergens and their presence in the environment

Exposure to animal allergens is a major risk factor for sensitization and allergic diseases. Besides mites and cockroaches, the most important animal allergens are derived from mammals. Cat and dog allergies affect the general population; whereas, allergies to rodents or cattle is an occupational problem. Exposure to animal allergens is not limited to direct contact to animals. Based on their aerodynamic properties, mammalian allergens easily become airborne, attach to clothing and hair, and can be spread from one environment to another. For example, the major cat allergen Fel d 1 was frequently found in homes without pets and in public buildings, including schools, day-care centers, and hospitals. Allergen concentrations in a particular environment showed high variability depending on numerous factors. Assessment of allergen exposure levels is a stepwise process that involves dust collection, allergen quantification, and data analysis. Whereas a number of different dust sampling strategies are used, ELISA assays have prevailed in the last years as the standard technique for quantification of allergen concentrations. This review focuses on allergens arising from domestic, farm, and laboratory animals and describes the ubiquity of mammalian allergens in the human environment. It includes an overview of exposure assessment studies carried out in different indoor settings (homes, schools, workplaces) using numerous sampling and analytical methods and summarizes significant factors influencing exposure levels. However, methodological differences among studies have contributed to the variability of the findings and make comparisons between studies difficult. Therefore, a general standardization of methods is needed and recommended.

Animal allergens and their presence in the environment

Exposure to animal allergens is a major risk factor for sensitization and allergic diseases. Besides mites and cockroaches, the most important animal allergens are derived from mammals. Cat and dog allergies affect the general population; whereas, allergies to rodents or cattle is an occupational problem. Exposure to animal allergens is not limited to direct contact to animals. Based on their aerodynamic properties, mammalian allergens easily become airborne, attach to clothing and hair, and can be spread from one environment to another. For example, the major cat allergen Fel d 1 was frequently found in homes without pets and in public buildings, including schools, day-care centers, and hospitals. Allergen concentrations in a particular environment showed high variability depending on numerous factors. Assessment of allergen exposure levels is a stepwise process that involves dust collection, allergen quantification, and data analysis. Whereas a number of different dust sampling strategies are used, ELISA assays have prevailed in the last years as the standard technique for quantification of allergen concentrations. This review focuses on allergens arising from domestic, farm, and laboratory animals and describes the ubiquity of mammalian allergens in the human environment. It includes an overview of exposure assessment studies carried out in different indoor settings (homes, schools, workplaces) using numerous sampling and analytical methods and summarizes significant factors influencing exposure levels. However, methodological differences among studies have contributed to the variability of the findings and make comparisons between studies difficult. Therefore, a general standardization of methods is needed and recommended.

Inhibition of cell division in mouse B-cell hybridomas: an overlooked property of 2-mercaptoethanol and its impact on in vitro antibody production

Thiol 2-mercaptoethanol (2-ME) has been reported to enhance growth in lymphocytes by various investigators. Some have used 50 μM for growing hybridomas in vitro. Concentrations of 50 and 5 μM in 5% FBS supplemented D-MEM were tested to determine their effects on the growth of 5 monoclonal antibody secreting mouse B cell hybridomas and the myeloma Sp2/O-Ag14. Viability after 24 and 48 h exposure was determined by Trypan blue exclusion. Analysis by one-way ANOVA confirmed that 50 μM 2-ME has a significant negative impact (p<0.05) on hybridoma as well as on myeloma growth, whereas no significant difference (p>0.05) between the control and the 5 μM treatment group was observed after 48 h. Also, no significant difference (p>0.05) in the mortality rates between the control and the treatment groups was found. When combined with the observed protracted doubling time in the 50 μM treatment group, these results indicate that the impact of 2-ME is due to inhibition of cell division. The degree of inhibition was observed to vary between the different hybridomas as well as the myeloma. Although the impact of 2-ME on mitosis has been demonstrated in organisms such as the ciliated protozoan Tetrahymena pyriformis, the yeast Saccharomycess cerevisiae, and the egg of the echinoid the sand dollar Dendraster excentricus, this work demonstrates for the first time that 2-ME impedes the growth of mouse B cell hybridomas. We conclude that adding 2-ME to mouse B cell hybridoma growth media may not be beneficial.

The Breathe-Easy Home: the impact of asthma-friendly home construction on clinical outcomes and trigger exposure

OBJECTIVES

We examined the asthma-control benefit of moving into an asthma-friendly Breathe-Easy home (BEH).

METHODS

We used a quasi-experimental design to compare the asthma outcomes of 2 groups of low-income children and adolescents with asthma: 34 participants who moved into a BEH, and a local matched cohort of 68 participants who had received a previous asthma-control intervention. Both groups received in-home asthma education. BEHs were constructed with moisture-reduction features, enhanced ventilation systems, and materials that minimized dust and off-gassing.

RESULTS

BEH residents' asthma-symptom-free days increased from a mean of 8.6 per 2 weeks in their old home to 12.4 after 1 year in the BEH. The proportion of BEH residents with an urgent asthma-related clinical visit in the previous 3 months decreased from 62% to 21%. BEH caretakers' quality of life increased significantly. The BEH group improved more than did the comparison group, but most differences in improvements were not significant. Exposures to mold, rodents, and moisture were reduced significantly in BEHs.

CONCLUSIONS

Children and adolescents with asthma who moved into an asthma-friendly home experienced large decreases in asthma morbidity and trigger exposure.

Exposure to Alternaria alternata in US homes is associated with asthma symptoms

BACKGROUND

Exposure to the fungus Alternaria alternata is a risk factor for asthma. Few studies have examined Alternaria exposures in indoor environments.

OBJECTIVE

We examined whether exposure to A alternata in US homes was associated with asthma-related outcomes.

METHODS

The data for this study were collected as part of the National Survey of Lead and Allergens in Housing. This cross-sectional study surveyed a nationally representative sample of 831 housing units inhabited by 2456 individuals in 75 different locations throughout the United States. An interviewer-administered questionnaire obtained information on demographics, household characteristics, and occupants' health status. Exposure to A alternata was assessed by measuring concentrations of A alternata antigens in vacuumed dust samples using a polyclonal anti-A alternata antibody assay. Dust samples were collected from a bed, a sofa, or a chair, and from bedroom, living room, and kitchen floors.

RESULTS

Lifetime prevalence of doctor-diagnosed asthma was 11.2%, and 6.9% of the study subjects reported active asthma symptoms in the past 12 months. The prevalence of current symptomatic asthma increased with increasing Alternaria concentrations in US homes; higher levels of A alternata antigens increased the odds of having asthma symptoms in the past year (relative to the lowest tertile, adjusted odds ratio was 1.52, 95% CI, 0.90-2.55 for the 2nd tertile; and 1.84, 95% CI, 1.18-2.85 for the 3rd tertile).

CONCLUSION

Exposure to A alternata in US homes is associated with active asthma symptoms.

CLINICAL IMPLICATIONS

Measures that reduce indoor exposure to A alternata may help control asthma exacerbations.

The development of species-specific immunodiagnostics for Stachybotrys chartarum: the role of cross-reactivity

Mold contamination and exposure to fungi in indoor environments has been associated with various adverse health effects but little is known about the significance of individual fungal species in the initiation or exacerbation of such effects. Using Stachybotrys chartarum as a model fungus we sought to demonstrate that monoclonal antibodies (mAbs) can provide species-specific diagnostic reagents and also be used to investigate immunological cross-reactivity patterns among fungi. Mice were immunized with S. chartarum spore walls and monoclonal antibodies were screened against 60 fungal species and 24 different isolates of S. chartarum using an indirect ELISA. One species-specific mAb (IgG(1)) reacted only with spore preparations but not mycelium of S. chartarum or propagules of any other fungus. Five cross-reactive mAbs (IgM) documented extensive cross-reactivity among nine related Stachybotrys species and several non-related genera including several species of Cladosporium, Memnoniella, Myrothecium and Trichoderma. We also found that the ELISA reactivity for cross-reactive antigens and different isolates of S. chartarum differed considerably for normalized total amounts of mycelial antigen. We demonstrate that mAbs and immunoassays have the potential to detect S. chartarum species-specifically. The observed reactivity patterns with cross-reactive mAbs suggest that several fungi may share common antigens and that the majority of antigens are expressed by spores and mycelia. The observed cross-reactivity patterns need to be considered for accurate interpretations of environmental and serological analyses.

The production and characterization of monoclonal antibodies to the fungus Aspergillus versicolor

Fungal exposure measurements in indoor environments require accurate and precise monitoring methods. Such techniques may be based on monoclonal antibodies (Mabs) and enzyme-linked immunosorbent assays (ELISA) and here we report the cross-reactivity patterns of Mabs produced against Aspergillus versicolor. Balb/c mice were immunized with the particulate fraction of homogenized spores and 46 Mabs (35 IgM, nine IgG3, two IgG1) were produced and tested for cross-reactivity against 55 fungal species. None of the Mabs was found to be species-specific for A. versicolor. Several Mabs strongly cross-reacted with most Aspergillus, Penicillium and Eurotium species and some Mabs also cross-reacted with Paecilomyces variotii and several Cladosporium and Stachybotrys species. Our results show that antibody responses in mice against spores of A. versicolor are dominated by highly cross-reactive antibodies of the IgM isotype. The widespread cross-reactivity suggests that the specificity of antibodies to be used for the detection of fungi in environmental samples need to be thoroughly characterized in order to avoid ambiguities in the interpretation of monitoring results. Furthermore, accurate estimates of spore concentrations may require the application of species-specific Mabs in order to avoid bias in result interpretation because of the differential reactivity of cross-reactive Mabs with different fungi.

PRACTICAL IMPLICATIONS

Producers of monoclonal or polyclonal antibodies for the detection of fungi in environmental or clinical samples need to verify antibody reactivity patterns and accurately report that information to potential users. Furthermore, immunoassays based on mouse or human serum or purified immunoglobulin fractions need to consider antibody cross-reactivity as a potential confounding factor during interpretation of results.

DNA immunization for the production of monoclonal antibodies to Blo t 11, a paramyosin homolog from Blomia tropicalis

BACKGROUND

Blo t 11 is a high molecular weight allergen from Blomia tropicalis with significant immunoglobulin (Ig)E binding frequency. Native and recombinant Blo t 11 are susceptible to degradation and the isolation and expression of the allergen is problematic thus obtaining sufficient amounts of purified Blo t 11 for antibody production is limiting. DNA-based immunization is an attractive alternative strategy that bypasses antigen purification for antibody production.

OBJECTIVES

To use a DNA-based immunization protocol for the production and characterization of Blo t 11 monoclonal antibodies (mAbs).

METHODS

The 2625 bp cDNA coding for Blo t 11 was cloned into a mammalian expression vector and immunized intramuscularly with electroporation into mice. Monoclonal antibodies to Blo t 11 were generated using a methylcellulose-based hybridoma cloning kit. These mAbs were utilized for native Blo t 11 isolation and the development of sandwich enzyme-linked immunosorbent assay (ELISA).

RESULTS

Six mAbs recognizing the native and recombinant Blo t 11 were generated and characterized. Native Blo t 11 was affinity purified from Bt extract and its identity was confirmed by matrix assisted laser desorption/ionization - time of flight mass spectrometry. The native Blo t 11 showed IgE reactivity with 67% of mite allergic sera. A two-site ELISA developed showed a detection limit of 100 pg/ml of Blo t 11.

CONCLUSION

A DNA-based immunization protocol was successfully used to generate Blo t 11 mAbs with a spectrum of distinct epitopes located throughout the whole molecule, and they are useful for immunoaffinity purification and immunoassays.

Production of monoclonal antibodies for immunoaffinity purification and quantitation of Blo t 1 allergen in mite and dust extracts

BACKGROUND

Blo t 1 is a cysteine protease-like allergen from Blomia tropicalis. Recombinant Blo t 1 binds up to 90% of IgE from allergic patients and shows limited cross-reactivity to Der p 1. The generation of monoclonal antibodies (mAbs) against Blo t 1 is important for the detection, isolation and characterization of the native form of the allergen.

METHODS

Mice were immunized intramuscularly with naked plasmid DNA encoding Blo t 1 gene with in vivo electroporation and boosted intraperitoneally with recombinant Blo t 1. mAbs against Blo t 1 were generated using a methylcellulose-based hybridoma cloning kit. The native Blo t 1 was isolated by mAb affinity purification and its allergenicity was determined by ELISA. A two-site ELISA for Blo t 1 was developed using the mAbs generated.

RESULTS

A DNA-based immunization protocol induced high titre Blo t 1-specific antibodies in mice. Six stable hybridoma clones secreting mAbs recognizing the native and recombinant Blo t 1 were generated. The native Blo t 1 was affinity-purified from a B. tropicalis extract and its allergenicity was determined at 63% using a panel of Singaporean and Malaysian mite allergic patients' sera. A two-site ELISA was developed, which showed a detection limit of 10 ng/mL of Blot t 1.

CONCLUSION

Six Blo t 1 mAbs were successfully generated by DNA immunization. These mAbs are useful for nBlo t 1 immunoaffinity isolation and quantitative immunoassays for Blo t 1 in mite and environmental dust extracts.

An ELISA for recombinant Lepidoglyphus destructor, Lep d 2, and the monitoring of exposure to dust mite allergens in farming households

BACKGROUND

Exposure to indoor allergens, such as dust mites, has been recognized as a risk factor for sensitization and symptoms.

OBJECTIVE

To develop a two-site ELISA for the determination of Lep d 2 in the reservoir, to measure dust mite allergen exposure (Lep d 2, Der p 1, Der f 1 and Der 2) in farm households, and to investigate whether exposure to these allergens is associated with sensitization, asthma and rhinoconjunctivitis.

METHODS

Monoclonal antibodies to recombinant (r)Lep d 2 were produced with standard hybridoma technique. Dust samples from 393 households were analysed for allergen content by two-site ELISA methods.

RESULTS

A two-site Lep d 2 ELISA was developed with a detection limit of 0.09 microg/g. The assay was highly reproducible and levels of Lep d 2 showed a strong correlation with the number of Lepidoglyphus mites (r(s): 0.7; P = 0.0002). Lep d 2 was detected in 20% of the homes; levels ranged from 0.09 to 1.7 microg/g of dust. Der p 1 was recorded in 59% of the samples, ranging from 0.055 to 139 microg/g, and Der f 1 and Der 2 in 40% and 50% of the samples, ranging from 0.055 to 24.5 microg/g and 24.3 microg/g, respectively. Dermatophagoides allergens were significantly higher in mattresses than in carpets (P < 0.0001), but this difference was not observed with Lep d 2. A strong relationship between immunoglobulin (Ig)E to rLep d 2 and asthma (OR = 10.4) and rhinoconjunctivitis (OR = 7.5) was seen. Furthermore, sensitization to D. pteronyssinus was significantly associated with asthma (OR: 13.7) and rhinoconjunctivitis (OR: 5.7).

CONCLUSION

When assessing mite allergen exposure in rural homes, not only the Der p 1, Der f 1 and Der 2 allergens, but also the Lep d 2 allergen should be taken into consideration.