Immunobiology of fungal allergens

Molecular approaches for new vaccines against allergy

Type I allergy represents an important health problem that is currently affecting approximately 25% of the population in Western countries. Immunotherapy, the only causative treatment of Type I allergy, is currently performed with crude allergen extracts, which contain unpredictable amounts of allergenic, as well as nonallergenic, components. The application of molecular biology for allergen characterization has revealed the molecular nature of the most common allergens and allowed the production of recombinant allergens that equal natural allergens. Based on this knowledge, several different strategies to improve immunotherapy have become available. Until now, T-cell peptides, selected wild-type-like recombinant allergens and genetically modified hypoallergenic allergen derivatives have been evaluated in clinical trials in patients. Immunotherapy based on T-cell peptides has focused on allergen-specific T-cell responses, whereas genetically modified recombinant allergen molecules offer the advantage of combining T-cell and B-cell epitopes. Genetically modified recombinant birch pollen derivatives (Bet v 1-fragments, Bet v 1-trimer) have been evaluated in a double-blind, placebo-controlled, multicenter study. Vaccination with the Bet v 1-derivatives improved symptoms of birch pollen allergy, induced a healthy allergen-specific immunoglobulin G response and led to a significant reduction of seasonally induced boosts of immunoglobulin E.

Halogen immunoassay, a new method for the detection of sensitization to fungal allergens; comparisons with conventional techniques

BACKGROUND

Accurate diagnosis of allergy to specific fungal species is confounded by the variability in allergens occurring with different diagnostic systems. We compared the halogen immunoassay (HIA), which uses allergens expressed by freshly germinated spores that are bound to protein binding membranes (PBM), with the commercial Pharmacia UniCap assay (CAP) and with skin prick tests (SPT).

METHODS

Serum from 60 subjects was used; 30 were SPT positive and sensitized to at least one of Alternaria alternata or Aspergillus fumigatus and the other 30 were SPT negative to these fungi but known to be sensitized to non-fungal allergens. All sera were analyzed by CAP against A. alternata, A. fumigatus, Cladosporium herbarum and Epicoccum purpurascens. For HIA, spores from reference cultures belonging to these four species were germinated on PBM, laminated and then probed with each serum. Two independent observers using an ordinal ranking system quantified the intensity and occurrence of the resultant immunoglobulin E (IgE) immunostained haloes around spores and this was statistically compared with the results of the two conventional immunodiagnostic techniques.

RESULTS

Germinated conidia of each species expressed detectable allergen in the HIA. The agreement between the ordinal rank scores assigned by the pair of observers was very good (k >or= 0.8) and only differed for A. fumigatus (k = 0.66) . Between 3% and 7% of SPT negative sera was identified by HIA to have specific IgE towards A. fumigatus and A. alternata. For all four species tested there were strong correlations between HIA and CAP (P < 0.0001). However the correlation of both HIA and CAP to SPT was weaker for A. alternata (r(s) = 0.44, P < 0.0153) and absent for A. fumigatus.

CONCLUSIONS

Overall, the HIA is a new immunodiagnostic technique for the detection of sensitization to fungal allergens that correlates significantly with CAP and to a lesser extent with SPT. This may be due to extract variability and system differences. The significance of this derives from the unique ability of the HIA to measure IgE antibodies to the undegraded allergens that are actively secreted by germinating conidia and hyphae. These are the natural agents of exposure to fungi, and as such, are most likely to be relevant to clinical disease.

The major allergen of Alternaria alternata (Alt a 1) is expressed in other members of the Pleosporaceae family

There is general consensus regarding the scarce cross-reactivity existing between Alternaria alternata and other allergenic moulds such as Aspergillus fumigatus, Penicillium notatum or Cladosporium herbarum. However, A. alternata has been shown to have a very significant level of allergenic cross-reactivity with other fungi belonging to the Pleosporaceae family. To date, no biological identity or homologies with other proteins have been described for Alt a 1, and it remains unclear whether the major allergen Alt a 1 contributes to the cross-reactivity shown for these moulds. Specific quantification of Alt a 1 in culture filtrates of Stemphylium botryosum, Ulocladium botrytis, Curvularia lunata, Alternaria tenuissima, C. herbarum, Penicillium chrysogenum and Asp. fumigatus, and immunoblotting using culture filtrate extracts from the above-mentioned moulds and rabbit serum anti-recombinant Alt a 1 have shown significant amounts of Alt a 1 in culture filtrates as well as antigenic components ranging from 14 to 20 kDa that strongly react with the specific serum for all taxonomically related species (Pleosporaceae family). No reactions were revealed in culture filtrates of Cladosporium, Penicillium and Aspergillus. These results restrict the cross-reactivity phenomenon due to Alt a 1 to the scope of the taxonomical term of family.

Pen ch 13 allergen induces secretion of mediators and degradation of occludin protein of human lung epithelial cells

BACKGROUND

Alkaline serine proteases from six prevalent airborne Penicillium and Aspergillus species have been identified as a group of major allergens (group 13). After entering human airways, the allergens are in initial contacts with respiratory epithelial cells. The purpose of this study is to investigate interactions between the Pen ch 13 allergen from P. chrysogenum and human lung epithelial cells.

METHODS

A549 cells, 16HBE14o- cells and primary cultures of human bronchial epithelial cells (HBEpC) were exposed to purified Pen ch 13 and mediators released into culture supernatants were assayed with enzyme-linked immunosorbent assay (ELISA) kits. Cleavage of occludin in 16HBE14o- cells was analysed by immunofluorescent staining of whole cells and immunoblot analysis of whole cell extracts. Fragments generated by incubating Pen ch 13 and a synthetic peptide carrying the occludin sequence were analysed by mass spectrometry.

RESULTS

Pen ch 13 induced productions of prostaglandin-E2 (PGE2), interleukin (IL)-8 and transforming growth factor (TGF)-beta1 by A549 cells, 16HBE14o- cells and primary cultures of HBEpC. The protease activity of Pen ch 13 is needed for the induction of PGE2 IL-8, TGF-beta1 and cyclo-oxygenase (COX)-2 expression. A tight junction protein occludin of 16HBE14o- cells can be cleaved by Pen ch 13 at Gln202 and Gln211 which are within the second extracellular domain of the protein.

CONCLUSION

Pen ch 13 may contribute to asthma by damaging the barrier formed by the airway epithelium and stimulating the release of mediators that orchestrate local immune responses and inflammatory process from HBEpC.

Use of green fluorescent protein-expressing Aspergillus fumigatus conidia to validate quantitative PCR analysis of air samples collected on filters

This study used green fluorescent protein (GFP)-expressing Aspergillus fumigatus conidia to compare quantitative PCR (qPCR) enumeration with direct epifluorescent microscopic filter counts of conidia collected on filters in a test chamber. In separate experiments this study initially compared white versus fluorescent light microscopy for counting A. fumigatus conidia, then compared fluorescent microscopy counting of corresponding filter halves, and finally compared qPCR enumeration to counting by fluorescent light microscopy. The use of GFP-expressing conidia with epifluorescent microscopy yielded significantly higher conidia counts (p = 0.026, n = 41, mean of 4.1 conidia per counting field) and 40% faster counting times when compared to conventional counting using white light microscopy. GFP-expressing conidia were aerosolized in a test chamber and collected onto filters. Filters were divided in half and GFP-expressing conidia enumerated. There was no significant difference in the average conidia count per field between corresponding filter halves (p = 0.3, n = 9 filters, mean of 7.8 conidia per counting field). Thus, one filter half could be counted optically and would provide a reliable estimate of filter loading of the corresponding half, which could then be analyzed by qPCR. Filters (n = 38) loaded with GFP conidia in the aerosol chamber were divided in half and analyzed by either fluorescent microscopy or qPCR. The estimated filter loadings ranged from 15-30,000 conidia per filter. There was a linear relationship with a nearly 1:1 ratio between qPCR and direct microscopic estimates of filter loading (y = 1.06x + 404; R(2) = 0.91) showing that the outlined qPCR analysis method is in agreement with an external reference method and is reliable for enumerating A. fumigatus conidia collected on filters. The comparative data derived using GFP-expressing conidia confirmed that qPCR provides sensitive and accurate quantification of DNA from airborne conidia collected on filters.

A Vacuolar Serine Protease (Rho m 2) Is a Major Allergen of Rhodotorula mucilaginosa and Belongs to a Class of Highly Conserved Pan-Fungal Allergens

BACKGROUND

Rhodotorula mucilaginosa is one of the most frequently encountered species of yeasts in our environment. We reported here a major allergen of R. mucilaginosa.

METHODS

A major R. mucilaginosa allergen (Rho m 2) was characterized by two-dimensional (2D) immunoblotting, protein sequencing, cDNA cloning and IgE cross-reactivity with fungal serine proteases.

RESULTS

Fourty-four sera (28%) from 157 bronchial asthmatic patients showed IgE-immunoblot reactivity against R. mucilaginosa extract. Among these 44 sera, 25 (57%) demonstrated IgE binding against a 31-kDa protein of R. mucilaginosa. Protein sequencing results suggest that it is a vacuolar serine protease. The corresponding cDNA clone encoding a mature protein of 312 residues was isolated. It shares 67-68% sequence identity with vacuolar serine protease allergens from three different Penicillium species (Pen ch 18, Pen o 18 and Pen c 18) and designated as Rho m 2 by the Allergen Nomenclature Committee. The native and recombinant Rho m 2 react with IgE antibodies and monoclonal antibody (MoAb) FUM20 against fungal serine proteases. IgE cross-reactivity between nRho m 2 and nPen ch 18 was observed. It was also detectable between rRho m 2 and rPen o 18.

CONCLUSION

Our results suggest that R. mucilaginosa may also be a significant causative agent of human respiratory allergic disorders. We identified a vacuolar serine protease as a major allergen of R. mucilaginosa (Rho m 2) and a pan allergen of prevalent airborne fungal species. We detected IgE cross-reactivity among these highly conserved serine protease pan-fungal allergens.

Isolation and characterization of a cDNA clone encoding one IgE-binding fragment of Penicillium brevicompactum

BACKGROUND

The abundance of allergenic Penicillium species has been associated with an increased incidence of childhood asthma and pulmonary bleeding. Penicillium brevicompactum has been identified as the most prevalent indoor species of this genus. However, detailed studies on the allergens of the ubiquitous Penicillium species are still lacking. For the characterization of allergens of prevalent Penicillium species, molecular cloning of the allergen genes of P. brevicompactum was performed in the present study.

METHODS

A phage cDNA library of P. brevicompactum was constructed in Uni-ZAP XR vector using mRNA isolated from the organism. The cDNA library of P. brevicompactum was screened using pooled atopic sera.

RESULTS

Screening of P. brevicompactum cDNA library resulted in one positive clone encoding an estimated molecular weight of 11 kDa polypeptide, rich in acidic residues (>20%), with a pI of 3.87. This clone was designated as Pen b 26 and found to be reactive only against the atopic sera obtained from individuals sensitive to P. brevicompactum. The amino acid sequence analysis of Pen b 26 revealed that it had strong homology to the 60S acidic ribosomal protein P1 family from different eukaryotic sources, predominantly fungal aero-allergens. Other features of Pen b 26 including having high alpha-helical content (>50%), alanine-rich residues (>20%), and a well-conserved C-terminal epitope region fits well into the common properties of 60S acidic ribosomal proteins.

CONCLUSIONS

The results obtained suggest that the allergenic clone, Pen b 26 is a 60S acidic ribosomal protein P1 of P. brevicompactum and shows strong similarity to other P1 family proteins.

Production and characterization of a noncytotoxic deletion variant of the Aspergillus fumigatus allergen Aspf1 displaying reduced IgE binding

Aspergillus fumigatus is responsible for many allergic respiratory diseases, the most notable of which - due to its severity - is allergic bronchopulmonary aspergillosis. Aspf1 is a major allergen of this fungus: this 149-amino acid protein belongs to the ribotoxin family, whose best characterized member is alpha-sarcin (EC 3.1.27.10). The proteins of this group are cytotoxic ribonucleases that degrade a unique bond in ribosomal RNA impairing protein biosynthesis. Aspf1 and its deletion mutant Aspf1Delta(7-22) have been produced as recombinant proteins; the deleted region corresponds to an exposed beta-hairpin. The conformation of these two proteins has been studied by CD and fluorescence spectroscopy. Their enzymatic activity and cytotoxicity against human rhabdomyosarcoma cells was also measured and their allergenic properties have been studied by using 58 individual sera of patients sensitized to Aspergillus. Aspf1Delta(7-22) lacks cytotoxicity and shows a remarkably reduced IgE reactivity. From these studies it can be concluded that the deleted beta-hairpin is involved in ribosome recognition and is a significant allergenic region.

Distinct roles for IL-4 and IL-10 in regulating T2 immunity during allergic bronchopulmonary mycosis

Pulmonary Cryptococcus neoformans infection of C57BL/6 mice is an established model of an allergic bronchopulmonary mycosis that has also been used to test a number of immunomodulatory agents. Our objective was to determine the role of IL-4 and IL-10 in the development/manifestation of the T2 response to C. neoformans in the lungs and lung-associated lymph nodes. In contrast to wild-type (WT) mice, which develop a chronic infection, pulmonary clearance was significantly greater in IL-4 knockout (KO) and IL-10 KO mice but was not due to an up-regulation of a non-T cell effector mechanism. Pulmonary eosinophilia was absent in both IL-4 KO and IL-10 KO mice compared with WT mice. The production of IL-4, IL-5, and IL-13 by lung leukocytes from IL-4 KO and IL-10 KO mice was lower but IFN-gamma levels remained the same. TNF-alpha and IL-12 production by lung leukocytes was up-regulated in IL-10 KO but not IL-4 KO mice. Overall, IL-4 KO mice did not develop the systemic (lung-associated lymph nodes and serum) or local (lungs) T2 responses characteristic of the allergic bronchopulmonary C. neoformans infection. In contrast, the systemic T2 elements of the response remained unaltered in IL-10 KO mice whereas the T2 response in the lungs failed to develop indicating that the action of IL-10 in T cell regulation was distinct from that of IL-4. Thus, although IL-10 has been reported to down-regulate pulmonary T2 responses to isolated fungal Ags, IL-10 can augment pulmonary T2 responses if they occur in the context of fungal infection.

cDNA cloning and immunologic characterization of a novel EF-1beta allergen from Penicillium citrinum

BACKGROUND

We have identified previously that Penicillium citrinum is the most prevalent Penicillium species in the Taipei area. It is important to delineate the whole spectrum of allergenic components of this prevalent airborne fungus. The purpose of this study was to identify novel P. citrinum allergens through molecular cloning of allergen genes using a cDNA library of P. citrinum and sera from patients with bronchial asthma.

METHODS

A lambda-Uni-ZAP XR-based cDNA library of P. citrinum was screened with sera from asthmatic patients. An IgE-binding cDNA clone was isolated and heterologously expressed in Escherichia coli. The frequency of IgE-binding to the expressed protein and the IgE reactivity to allergen subunits were analyzed by immunoblotting.

RESULTS

An IgE-reactive cDNA clone (clone B) was isolated by plaque immunoassay. The cDNA insert is 876-bp long and encodes a 228-amino acid polypeptide with a calculated molecular mass of 25 035 Da. Protein database search with the deduced clone B sequence revealed that 121 (53%) and 82 (36%) of the 228 amino acids were identical to those of the elongation factor 1-beta (EF-1beta) proteins from the yeast Saccharomyces cerevisiae and the parasite Echinococcus granulosus, respectively. His-tagged recombinant clone B proteins were constructed and expressed in E. coli. Seven (8%) of the 92 serum samples from patients with bronchial asthma showed IgE-binding to the recombinant clone B protein. Among these seven positive sera, five demonstrated IgE-binding to the C-terminal fragment (aa 119-228) while the other two sera showed IgE reactivity to the N-terminal fragment (aa 1-118) of this newly identified EF-1betaPenicillium allergen.

CONCLUSIONS

A novel P. citrinum allergen (Pen c 24) was identified and characterized in the present study. Results obtained provide more information about allergens of prevalent airborne fungi and a basis to understand more about the IgE responses in human atopic disorders and in parasitic infections.

Generation of Aspergillus- and CMV- specific T-cell responses using autologous fast DC

BACKGROUND

Recent reports have described a new strategy for differentiation and maturation of monocyte (Mo)-derived DCs within only 48 h of in vitro culture (fast-DC). Here we assess the efficacy of the fast-DC to process and present different Aspergillus fumigatus and CMV Ag preparations to autologous T cells, compared with DCs generated in standard 7-day cultures (standard-DC).

METHODS

Adherent blood Mo were treated with GM-CSF and IL-4 (1 day for fast-DC, 5 days in the standard-DC) to generate immature DCs, and then were matured for either 1-2 days (fast-DC) or 2 days (standard-DC) with inflammatory cytokines. DCs were pulsed with A. fumigatus or CMV Ag preparation immediately prior to maturation, or infected after maturation with adeno-pp65. Mature DCs were then used to prime Ag-specific proliferative and cytotoxic T lymphocytes (CTL) responses.

RESULTS

Fast-DC were CD14- and expressed mature DC surface markers to the same degree as standard-DC, and maintained this phenotype after withdrawing cytokine from the cultures. Fast-DC and standard-DC were equally capable of inducing A. fumigatus and CMV-specific T-cell proliferation, as well as priming Ag-specific CTL activity. The Aspergillus- and CMV-specific CTL were of mixed CD3+/CD4+ and CD3+/CD8+ phenotype, and specifically killed autologous DC pulsed with A. fumigatus Ag and autologous CMV infected fibroblasts, respectively.

DISCUSSION

Fast-DC are as effective as standard-DC in the generation of Ag-specific T-cell responses. Moreover, use of fast-DC not only reduces labor and supply cost, as well as workload and time, but also increases the number of DCs derived from adherent Mo, which may facilitate the use of DCs in clinical trials of cellular immunotherapy.

Allergens of the entomopathogenic fungus Beauveria bassiana

Background

Beauveria bassiana is an important entomopathogenic fungus currently under development as a bio-control agent for a variety of insect pests. Although reported to be non-toxic to vertebrates, the potential allergenicity of Beauveria species has not been widely studied.

Methods

IgE-reactivity studies were performed using sera from patients displaying mould hypersensitivity by immunoblot and immunoblot inhibition. Skin reactivity to B. bassiana extracts was measured using intradermal skin testing.

Results

Immunoblots of fungal extracts with pooled as well as individual sera showed a distribution of IgE reactive proteins present in B. bassiana crude extracts. Proteinase K digestion of extracts resulted in loss of IgE reactive epitopes, whereas EndoH and PNGaseF (glycosidase) treatments resulted in minor changes in IgE reactive banding patterns as determined by Western blots. Immunoblot inhibitions experiments showed complete loss of IgE-binding using self protein, and partial inhibition using extracts from common allergenic fungi including; Alternaria alternata, Aspergillus fumigatus, Cladosporium herbarum, Candida albicans, Epicoccum purpurascens, and Penicillium notatum. Several proteins including a strongly reactive band with an approximate molecular mass of 35 kDa was uninhibited by any of the tested extracts, and may represent B. bassiana specific allergens. Intradermal skin testing confirmed the in vitro results, demonstrating allergenic reactions in a number of individuals, including those who have had occupational exposure to B. bassiana.

Conclusions

Beauveria bassiana possesses numerous IgE reactive proteins, some of which are cross-reactive among allergens from other fungi. A strongly reactive potential B. bassiana specific allergen (35 kDa) was identified. Intradermal skin testing confirmed the allergenic potential of B. bassiana.

Molecular and structural analysis of immunoglobulin E-binding epitopes of Pen ch 13, an alkaline serine protease major allergen from Penicillium chrysogenum

BACKGROUND

Through proteomic and genomic approaches we have previously identified and characterized an alkaline serine protease that is a major allergen (88% frequency of IgE binding) of Penicillium chrysogenum (Pen ch 13).

OBJECTIVE

The aim of the present study is to identify the linear IgE-binding epitopes of Pen ch 13.

METHODS

IgE-binding regions were identified by dot-blot immunoassay using 11 phage-displayed peptide fragments spanning the whole molecule of Pen ch 13. The minimal epitope requirements for IgE binding were further defined with overlapping peptides synthesized on derivatized cellulose membranes using SPOTs technology. The critical residues on the immunodominant epitopes were mapped through site-directed mutagenesis. The locations of the IgE epitopes identified were correlated with a three-dimensional structure of Pen ch 13.

RESULTS

IgE antibodies in 35 serum samples reacted with at least one of the 11 peptide fragments of Pen ch 13. Peptide f-2n (residues 31-61) showed a high-intensity and the highest frequency (77%) of IgE binding. The frequencies of IgE binding to peptide f-4 (residues 93-133), f-1 (residues 1-37) and f-7 (residues 168-206) were 51%, 34% and 31%, respectively. SPOTs assay narrowed down the region of IgE binding of f-2n to residues 48-55 (GHADFGGR). Three, two and one epitope(s) that are four to nine amino acids in length, within f-4, f-1 and f-7, respectively, were found. Site-directed mutagenesis of Pen ch 13 revealed that substitution of His49 and/or Phe52 on Pen ch 13 with methionine resulted in proteins with drastic loss of IgE binding in seven sera tested. Proteins with amino acid replacements at residues 15-18 (RISS), or at residues 112 (I) and 116 (D) have lower IgE-binding reactivity in one of the two patient's sera tested. Substituting residues 117 (W), 119 (V) and 120 (K) also block most of the IgE binding in one of the two patient's sera tested. In addition, replacing residues 203 (V) and 204 (D) along with a deletion at residue 206 (Y) diminished the IgE binding in two serum samples tested. A model was constructed based on the structure of P. cyclopium subtilisin protease that has >90% (256 out of 283 amino acids) sequence identity with Pen ch 13. The major epitope (GHADFGGR) on Pen ch 13 formed a loop-like structure and was located at the surface of the allergen.

CONCLUSIONS

Several linear IgE-reactive epitopes and their critical core amino acid residues were identified for the Pen ch 13 allergen. The major linear IgE-binding epitope, 48GHADFGGR55, formed a loop-like structure at the surface of the allergen. Substitution of His49 and/or Phe52 with methionine significantly reduced IgE-binding to Pen ch 13. Mapping of these results on a 3D model of the allergen provides valuable information about the molecular basis of allergenicity for Pen ch 13 and for designing specific immunotherapeutics.

Genetically modified allergens

For more than 90 years, allergen-specific immunotherapy, the only causative allergy treatment, has remained basically unchanged. The development of molecular biology techniques has led to the preparation of individual recombinant allergens from the most important allergen sources. Recombinant allergens can be used to determine the individual sensitization profile of allergic patients and have allowed the development of novel therapeutic tools. This article summarizes data on genetically modified recombinant allergen derivatives with reduced allergenic activity, which may be used to improve the safety and efficacy of specific immunotherapy.

Partial Amino Acid Sequence of a Cellulase-Like Component with IgE-Binding Properties from Stachybotrys chartarum

BACKGROUND

The aim of this study was to characterize the amino acid sequence of a selected Stachybotrys chartarum component and to investigate human IgE reactivity against components of S. chartarum and nine other fungal species.

METHODS

Human IgE reactivity against S. chartarum and nine other fungal extracts was investigated by the immunoblotting method. For automated amino acid sequencing analyses, the S. chartarum extract was purified by ion exchange chromatography prior to in-gel alkylation and digestion with modified trypsin.

RESULTS

Human IgE reactivity was detected against eight components in the S. chartarum extract. Over 80% of the sera from the exposed subjects and less than 50% of the control sera recognized the 33-, 48- and 50-kD S. chartarum components. The human sera detected a 48- to 50-kD component from the extracts of eight fungal species. Nineteen peptide sequences were identified from the 48-kD component of S. chartarum. An analysis of the peptide sequences revealed homology with known fungal glycoside hydrolase enzymes (cellulases).

CONCLUSIONS

The data showed human IgE reactivity against several S. chartarum components, including one at 48 kD. On the other hand, the human sera recognized 48- to 50-kD components from seven other fungal species, suggesting shared antigenic components (e.g. enolase) between the fungi. Thus, to our knowledge, this is the first antigen identified from S. chartarum.

Limitations of monoclonal antibodies for monitoring of fungal aerosols using Penicillium brevicompactum as a model fungus

Molds are ubiquitous in every environment and many species have been recently associated with an increase in opportunistic infections in immunocompromised patients or the exacerbation of asthmatic episodes in allergic patients. The degree of environmental contamination with fungi thus needs to be monitored and in this study we report the development of a monoclonal antibody (mAb)-mediated enzyme-linked immunosorbent assay (ELISA) for the detection of spores of Penicillium brevicompactum in experimental model aerosols. In addition, we have investigated the influence of different parameters of air sampling and sample recovery on ELISA performance. MAbs were produced with standard hybridoma techniques and cross-reactivities were determined against spores of 53 fungal species by indirect ELISA. Standardized experimental fungal aerosols were collected with the Button Personal Inhalable Aerosol Sampler onto polycarbonate or polytetrafluoroethylene filters (PTFE) and the effects of different extraction buffers and filter agitation methods during sample processing on spore recovery and ELISA detection were investigated. Five mAbs were produced and all of them cross-reacted with several of 31 related Aspergillus, Penicillium and Eurotium species. However, cross-reactivities with 21 non-related fungi were rare. Spores were recovered in much higher numbers from polycarbonate filters (PFs) than from polytetrafluoroethylene filters. Optical densities (ODs) in ELISA were higher for spores collected into carbonate coating buffer (CCB) than phosphate-buffered saline (PBS). Filter bath sonication following filter vortexing had no positive effects on ELISA sensitivity. The cross-reactivity patterns of mAbs suggest that Aspergillus and Penicillium species share multiple antigens. Quantitative ELISA results for fungal aerosols were found to be influenced by differential sample processing and thus method standardization will be essential to maintain the comparability of immunometric monitoring results.

Can we genetically engineer safer and more effective immunotherapy reagents?

PURPOSE OF REVIEW

Progress in allergen-specific immunotherapy, the only causative form of allergy treatment, was limited by the lack of defined allergen molecules for vaccine formulation. Today the genetic informations for the most common allergens have been obtained. Here we review recombinant allergen-based technologies for the improvement of diagnosis and therapy of allergy.

RECENT FINDINGS

Numerous strategies, including the genetic engineering of allergens for reduction of allergenic activity, have been developed to improve allergen-specific immunotherapy. Genetically modified allergen derivatives with reduced allergenic activity, preserved T cell epitope repertoire and retained immunogenicity have been characterized in vitro and in vivo.

SUMMARY

Based on the review of the recently published data we argue that it is possible to genetically engineer safer and more effective immunotherapy reagents.

Immunotherapy in fungal allergy

For decades airborne fungal spores have been implicated as causative factors in respiratory allergy. Exposure to high atmospheric spore counts and sensitization to specific fungal allergens have been associated with severe asthma, mainly in young adults. Although the prevalence of sensitization to commercial fungal extracts is approximately 3% in epidemiologic studies, in selected patients, particularly with asthma, the sensitization rate might increase to 30%. Of the estimated number of more than 1 million of different fungal species, approximately 80 fungi have been connected with respiratory allergy. Currently, diagnosis and specific therapy of fungal allergy is hampered by the poor quality of most of the commercially available extracts. Clinical efficacy of specific immunotherapy with fungal extracts has been shown in 79 actively treated patients in four controlled trials, with only two fungal species, namely Alternaria alternata and Cladosporium herbarum. The use of recombinant fungal allergens might create new prospects in diagnosis and specific immunotherapy for fungal allergy.

Fungal allergens

Many fungi are capable of causing IgE-mediated hypersensitivity in humans. However, the most predominant fungi implicated in allergy belong to the genera Aspergillus, Alternaria, Cladosporium, and Penicillium. Pure and relevant allergens are essential for diagnosis as well as for understanding the immunopathogenesis of the disease. Until recently, pure and standardizable antigens from fungi were not available. In recent years, many recombinant allergens have been produced by molecular cloning. Using these allergens, novel methods are being developed to improve diagnosis of mold-induced allergy. By understanding the immunopathogenesis of allergens, new avenues might open up leading to improved patient care, including immunotherapy and vaccination. This review covers the current status of fungal allergens, their role in reliable immunodiagnosis, and their probable use in immunotherapy and vaccination.