Characterization of monoclonal antibodies to an antigenic protein from Stachybotrys chartarum and its measurement in house dust

Fungal bioaerosols as an occupational hazard

PURPOSE OF REVIEW

Over the past 40 years, the circumstances where fungal bioaerosols are major issues have shifted because of changes in the industrial sector from mainly agriculture to operations, including composting, cannabis production and forestry in hot humid conditions. Changes in the design and operation of nonindustrial workplaces meant that mould and dampness became major issues that are just being reduced. This review attempts to frame that history offers a perspective on the current thinking on mechanisms and provide potentially useful sources of information for physicians and their patients.

RECENT FINDINGS

The major impact of fungal exposures is not only from their allergens but also from an array of Danger-Associated Molecular Pattern molecules, possibly the most important of which is the type of glucan found in moulds that grow in damp buildings, wood chips and crops, that is beta 1, 3 D glucan in triple helical form. Located in lung epithelia, the dectin receptor is exquisitely sensitive to this compound. Except in some agricultural workplaces, low molecular weight secondary metabolites often mischaracterized as mycotoxins play little, if any, role on population health.

SUMMARY

There has been a convergence in thinking between the allergy and industrial hygiene communities as well as government agencies on mould and occupational health. This has led to some useful strategies for better managing these issues as well as increasing consumer awareness.

Immunodetection of fungal and oomycete pathogens: established and emerging threats to human health, animal welfare and global food security

Filamentous fungi (moulds), yeast-like fungi, and oomycetes cause life-threatening infections of humans and animals and are a major constraint to global food security, constituting a significant economic burden to both agriculture and medicine. As well as causing localized or systemic infections, certain species are potent producers of allergens and toxins that exacerbate respiratory diseases or cause cancer and organ damage. We review the pathogenic and toxigenic organisms that are etiologic agents of both animal and plant diseases or that have recently emerged as serious pathogens of immunocompromised individuals. The use of hybridoma and phage display technologies and their success in generating monoclonal antibodies for the detection and control of fungal and oomycete pathogens are explored. Monoclonal antibodies hold enormous potential for the development of rapid and specific tests for the diagnosis of human mycoses, however, unlike plant pathology, their use in medical mycology remains to be fully exploited.

Development of a monoclonal antibody-based sandwich-type enzyme-linked immunosorbent assay (ELISA) for detection of abrin in food samples

Abrin is a plant toxin, which can be easily isolated from the seeds of Abrus precatorius. It may be used as a biological warfare agent. In order to detect abrin in food samples, a two-layer sandwich format enzyme-linked immunosorbent assay based on the monoclonal antibody (mAb) (as capture antibody) and rabbit polyclonal serum (as detecting antibody) was developed and applied for the determination of abrin in some food matrices. The linear range of the mAb was 1-100 μg L(-1) with a detection limit of 0.5 μg L(-1) for abrin in phosphate buffered saline (PBS). The recoveries of abrin from sausage, beer and milk samples ranged 97.5-98.6%, 95.8-98.4% and 94.8-9.6%, respectively, with a coefficient of variation (CV) of 3.7% or less. The newly developed sandwich ELISA using the mAb appears to be a reliable and useful method for detection of abrin in sausage, beer and milk.

Sta c 3 epitopes and their application as biomarkers to detect specific IgE

Sta c 3 was determined to be one of the major allergens from Stachybotrys chartarum sensu lato. This is among the most common fungi on wet building materials. Various cognizant authorities have found that mold and dampness are associated with exacerbation of asthma and increased upper respiratory disease. The primary amino-acid sequence of this allergen was reported, however the IgE-binding epitopes were unknown. Using SPOT-synthesis techniques (SPOTs), one main linear epitope located between V91 and G105 was discovered by Western blot with atopic human sera. This was confirmed by inhibition ELISA assays with both synthesized epitopes and natural Sta c 3. Alanine scanning also revealed R100 and K101 are the critical amino acids for IgE binding. Using the binding-enhanced and alanine substituted epitopes as potential biomarkers, a reverse ELISA method was developed to detect the Sta c 3 sIgE in atopic human sera. This method employed streptavidin-biotinylated mutated epitopes as the capture matrix, probing the possibility of using small peptides for allergen/species specific IgE assays.

The development and validation of an assay for the quantification of the P. chrysogenum allergen Pch52

Penicillium chrysogenum clade 4, is a common mold on damp building materials. A capture ELISA assay for the major allergen from P. chrysogenum Pch52 has been developed and tested in house dust samples and potential cross-reactivity examined. Minimal cross-reactivity with other relevant indoor fungi was observed for the assay following thorough purification of the monoclonal and polyclonal antibodies. The limit of quantification for ELISA analysis of Pch52 in sieved house dust is comparable to other assays of other fungi. The LOQ for Pch52 was 0.31 ng/mL in solution or 110 ng/g dust. The LOQ for Asp f1 and Alt a1 were 2.2 ng/g and 17 ng/g, respectively. These results indicate this assay is suitable for the quantification of Pch52 in sieved house dust.

Production and characterization of IgM monoclonal antibodies against hyphal antigens of Stachybotrys species

Stachybotrys is a hydrophilic fungal genus that is well known for its ability to colonize water-damaged building materials in indoor environments. Personal exposure to Stachybotrys chartarum allergens, mycotoxins, cytolytic peptides, and other immunostimulatory macromolecules has been proposed to exacerbate respiratory morbidity. To date, advances in Stachybotrys detection have focused on the identification of unique biomarkers that can be detected in human serum; however, the availability of immunodiagnostic reagents to Stachybotrys species have been limited. In this study, we report the initial characterization of monoclonal antibodies (MAbs) against a semi-purified cytolytic S. chlorohalonata preparation (cScp) derived from hyphae. BALB/c mice were immunized with cScp and hybridomas were screened against the cScp using an antigen-mediated indirect ELISA. Eight immunoglobulin M MAbs were produced and four were specifically identified in the capture ELISA to react with the cScp. Cross-reactivity of the MAbs was tested against crude hyphal extracts derived from 15 Stachybotrys isolates representing nine Stachybotrys species as well as 39 other environmentally abundant fungi using a capture ELISA. MAb reactivity to spore and hyphal antigens was also tested by a capture ELISA and by fluorescent halogen immunoassay (fHIA). ELISA analysis demonstrated that all MAbs strongly reacted with extracts of S. chartarum but not with extracts of 39 other fungi. However, four MAbs showed cross-reactivity to the phylogenetically related genus Memnoniella. fHIA analysis confirmed that greatest MAb reactivity was ultrastructurally localized in hyphae and phialides. The results of this study further demonstrate the feasibility of specific MAb-based immunoassays for the detection of S. chartarum.

Quantification of the Aspergillus versicolor allergen in house dust

Aspergillus versicolor, a fungus commonly found on damp building materials, produces the allergen, Asp v 13. Here we report a sensitive Asp v 13 capture ELISA for A. versicolor spores and spore- and mycelial fragments in house dust samples. The method is based on a double polyclonal capture ELSIA. The detection limits for Asp v 13 antigen and A. versicolor spores without dust were 2.44 pg and 12 ng (ca. 110 spores). Detection limits for Asp v 13 and A. versicolor spores in sieved house dust samples were 1.0 ng and 7.8 μg per gram dry weight house dust, respectively. This detection limit is lower than for other house dust allergen immunoassays including for Stachybotrys chartarum, Aspergillus fumigatus, but much lower than that from Alternaria alternata.