Production and characterization of monoclonal antibodies to cell wall antigens of Aspergillus fumigatus

Diagnostic laboratory immunology for talaromycosis (penicilliosis): review from the bench-top techniques to the point-of-care testing

The pathogenic fungus Talaromyces (formerly Penicillium) marneffei is a thermally dimorphic fungus that can cause disseminated infection in patients with secondary immunodeficiency syndrome, in particular in the setting of advanced HIV infection. The areas of highest incidence are in Southeast Asia, Southern China, and Indian subcontinents. Talaromycosis (formerly penicilliosis) is identified as an AIDS-defining illness, and it has recently been recognized in non-HIV-associated patients with impaired cellular-mediated immunity. Microbiological culture is the gold standard method for the diagnosis of T. marneffei infection and usually requires up to 2-4 weeks for detectable growth to occur, which may result in a delay of appropriate treatment. Immunodiagnosis has become an alternative method for confirming talaromycosis. This article reviews various immunological tests for the diagnosis of talaromycosis, including a proposed novel rapid point-of-care assay using a new T. marneffei yeast phase-specific monoclonal antibody.

Monoclonal Antibody AP3 Binds Galactomannan Antigens Displayed by the Pathogens Aspergillus flavus, A. fumigatus, and A. parasiticus

Aspergillus fumigatus and A. flavus are the fungal pathogens responsible for most cases of invasive aspergillosis (IA). Early detection of the circulating antigen galactomannan (GM) in serum allows the prompt application of effective antifungal therapy, thus improving the survival rate of IA patients. However, the use of monoclonal antibodies (mAbs) for the diagnosis of IA is often associated with false positives due to cross-reaction with bacterial polysaccharides. More specific antibodies are therefore needed. Here we describe the characterization of the Aspergillus-specific mAb AP3 (IgG1κ), including the precise identification of its corresponding antigen. The antibody was generated using A. parasiticus cell wall fragments and was shown to bind several Aspergillus species. Immunofluorescence microscopy revealed that AP3 binds a cell wall antigen, but immunoprecipitation and enzyme-linked immunosorbent assays showed that the antigen is also secreted into the culture medium. The inability of AP3 to bind the A. fumigatus galactofuranose (Galf )-deficient mutant ΔglfA confirmed that Galf residues are part of the epitope. Several lines of evidence strongly indicated that AP3 recognizes the Galf residues of O-linked glycans on Aspergillus proteins. Glycoarray analysis revealed that AP3 recognizes oligo-[β-D-Galf-1,5] sequences containing four or more residues with longer chains more efficiently. We also showed that AP3 captures GM in serum, suggesting it may be useful as a diagnostic tool for patients with IA.

Aspergillus-specific antibodies - Targets and applications

Aspergillus is a fungal genus comprising several hundred species, many of which can damage the health of plants, animals and humans by direct infection and/or due to the production of toxic secondary metabolites known as mycotoxins. Aspergillus-specific antibodies have been generated against polypeptides, polysaccharides and secondary metabolites found in the cell wall or secretions, and these can be used to detect and monitor infections or to quantify mycotoxin contamination in food and feed. However, most Aspergillus-specific antibodies are generated against heterogeneous antigen preparations and the specific target remains unknown. Target identification is important because this can help to characterize fungal morphology, confirm host penetration by opportunistic pathogens, detect specific disease-related biomarkers, identify new candidate targets for antifungal drug design, and qualify antibodies for diagnostic and therapeutic applications. In this review, we discuss how antibodies are raised against heterogeneous Aspergillus antigen preparations and how they can be characterized, focusing on strategies to identify their specific antigens and epitopes. We also discuss the therapeutic, diagnostic and biotechnological applications of Aspergillus-specific antibodies.

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.

The use of MUC5B antibody in identifying the fungal type of fungal sinusitis

Fungal sinusitis is an opportunistic fungal infection. Candida albicans, Aspergillus spp, and Mucorales, the most common pathogenic fungi, differ in both prognosis and therapy. Early diagnosis and differentiation between the subtypes therefore are pivotal for adequate treatment. This report describes a diagnostic immunohistochemical method that is able to distinguish these types of fungi. Formalin-fixed paraffin-embedded blocks of 89 fungal sinusitis specimens (12 C albicans, 52 Aspergillus spp, and 25 Mucorales) and 21 cultures (5 C albicans, 11 Aspergillus spp, and 5 Mucorales) were stained with MUC2, MUC5AC, and MUC5B antibodies. The immunohistochemical staining results of paraffin-embedded samples for MUC5B were successful in 100% and 92.3% of the C albicans and Aspergillus spp samples, respectively. Only 4.0% of the Mucorales parafin sections were found positive, demonstrating a significant difference in detection from C albicans and Aspergillus spp (P < .001). MUC5B expressions for cultures showed that it stained 100% and 90.9% for C albicans and Aspergillus spp, respectively, but negative for Mucorales. The expressions of MUC2 and MUC5AC for both paraffin-embedded samples and cultures were negative. The present study demonstrates the ability of an MUC5B antibody to distinguish C albicans and Aspergillus spp from Mucorales and its use as a diagnostic tool in fungal sinusitis.

Monoclonal immunoglobulin G1 directed against Aspergillus fumigatus cell wall glycoprotein protects against experimental murine aspergillosis

Most of the biological functions related to pathogenicity and virulence reside in the fungal cell wall, which, being the outermost part of the cell, mediates the host-fungus interplay. For these reasons much effort has focused on the discovery of useful inhibitors of cell wall glucan, chitin, and mannoprotein biosynthesis. In the absence of a wide-spectrum, safe, and potent antifungal agent, a new strategy for antifungal therapy is directed towards the development of monoclonal antibodies (MAbs). In the present study the MAb A9 (immunoglobulin G1 [IgG1]) was identified from hybridomas raised in BALB/c mice immunized with cell wall antigen of Aspergillus fumigatus. The immunoreactive epitopes for this IgG1 MAb appeared to be associated with a peptide moiety, and indirect immunofluorescence microscopy revealed its binding to the cell wall surface of hyphae as well as with swollen conidia. MAb A9 inhibited hyphal development as observed by MTT [3-(4,5-dimethythiazol-2-yl)-2,5-diphenyltetrazolium bromide] assay (25.76%), reduced the duration of spore germination, and exerted an in vitro cidal effect against Aspergillus fumigatus. The in vivo protective efficacy of MAb A9 was also evaluated in a murine model of invasive aspergillosis, where a reduction in CFU (>4 log(10) units) was observed in kidney tissue of BALB/c mice challenged with A. fumigatus (2 x 10(5) CFU/ml) and where enhanced mean survival times (19.5 days) compared to the control (7.1 days) and an irrelevant MAb (6.1 days) were also observed.

Use of recombinant mitogillin for improved serodiagnosis of Aspergillus fumigatus-associated diseases

During human infection, Aspergillus fumigatus secretes a 18-kDa protein that can be detected as an immunodominant antigen in the urine of infected patients. Recently, this protein was shown to be mitogillin, a ribotoxin that cleaves a single phosphodiester bond of the 29S rRNA of eukaryotic ribosomes. We proved the immunogenic capacity of mitogillin in a rabbit animal model, indicating its usefulness as an antigen for serological diagnosis of invasive aspergillosis. The mitogillin gene from A. fumigatus was transferred from plasmid pMIT+ to expression vector pQE30 and expressed in Escherichia coli as a fusion protein. Purified recombinant mitogillin was recognized by serum immunoglobulin G (IgG) of polyclonal rabbit sera that were obtained by immunization with purified native mitogillin. Consequently, we developed an enzyme-linked immunosorbent assay for detection of IgG, IgM, and IgA antibodies to recombinant mitogillin. In serum samples of patients suffering from aspergilloma (AO; n = 32), invasive pulmonary aspergillosis (IPA; n = 42), or invasive disseminated aspergillosis (IDA; n = 40), a good correlation of production of IgG antibody against mitogillin and clinical disease was observed (for patients with AO, 100% [32 of 32] were positive; for patients with IPA, 64% [31 of 42] were positive; for patients with IDA, 60% [24 of 40] were positive). In contrast, positive titers for serum IgG and IgM antibodies against mitogillin were found in only 1.3% of the serum samples of healthy volunteers and positive titers for IgA antibody were found in only 1.0% of the serum samples of healthy volunteers (n = 307; specificity = 95.4%). These results indicate that recombinant mitogillin expressed in E. coli can be used for improvement of the serodiagnosis of A. fumigatus-associated diseases.

Immunochemical detection of molds: a review

Molds are widely distributed in nature and cause deterioration of foods and feeds. Their mycotoxins can adversely affect human and animal health. Suitable assays for molds, therefore, are required to implement control and regulatory strategies and to develop appropriate feeding regimens for mold-infested feeds. Many different types of mold assays have been used, most of which are not reproducible or accurate. However, the immunoassays, particularly enzyme-linked immunosorbent assays (ELISAs), can be especially useful. Among these, assays that detect the water-soluble extracellular secretions of fungi, the exoantigens, are generally able to detect fungi at the genus or species level, whereas the heat-stable polysaccharides tend to be specific for one or more genus of fungi. Several species and genus (genera)-specific ELISAs have been developed using monoclonal or polyclonal antibodies against exoantigens and heat-stable polysaccharides from a wide range of fungi, including Aspergillus, Penicillium, and Fusarium species. Other assays have been developed that nonspecifically detect mold in food or feed, some using antibodies against a mixture of antigens from different fungi. These assays are highly sensitive, are easy to perform, and provide an index of the amount of mold present in the sample. Further refinement of these assays should facilitate their widespread use by food and feed processors, regulatory agencies, taxonomists, and research scientists.

Aspergillus fumigatus and aspergillosis

Aspergillus fumigatus is one of the most ubiquitous of the airborne saprophytic fungi. Humans and animals constantly inhale numerous conidia of this fungus. The conidia are normally eliminated in the immunocompetent host by innate immune mechanisms, and aspergilloma and allergic bronchopulmonary aspergillosis, uncommon clinical syndromes, are the only infections observed in such hosts. Thus, A. fumigatus was considered for years to be a weak pathogen. With increases in the number of immunosuppressed patients, however, there has been a dramatic increase in severe and usually fatal invasive aspergillosis, now the most common mold infection worldwide. In this review, the focus is on the biology of A. fumigatus and the diseases it causes. Included are discussions of (i) genomic and molecular characterization of the organism, (ii) clinical and laboratory methods available for the diagnosis of aspergillosis in immunocompetent and immunocompromised hosts, (iii) identification of host and fungal factors that play a role in the establishment of the fungus in vivo, and (iv) problems associated with antifungal therapy.

Production of specific monoclonal antibodies to Aspergillus species and their use in immunohistochemical identification of aspergillosis

Two anti-Aspergillus murine monoclonal antibodies (MAbs), designated 164G and 611F, have been produced; both specifically recognize cytoplasmic antigens of A. fumigatus, A. flavus, and A. niger by enzyme-linked immunosorbent assay. The MAbs can identify Aspergillus spp. both in frozen sections by immunofluorescence and in paraffin-embedded clinical specimens by immunofluorescence and immunoperoxidase staining.

Aspergillus nidulans swo mutants show defects in polarity establishment, polarity maintenance and hyphal morphogenesis

When the spores of filamentous fungi break dormancy, they grow isotropically, adding cell wall material uniformly in every direction. Later they switch to polarized growth, with new material added to the tip of an emerging germ tube. To identify genes involved in the synthesis and localization of cell wall material in filamentous fungi, we screened a collection of temperature-sensitive Aspergillus nidulans mutants for swollen cells. We have isolated mutants representing eight genes involved in polarity establishment, polarity maintenance, and hyphal morphogenesis. On the basis of the results of temperature-shift experiments, swo C, D, and F are required to establish polarity, while swoA is required to maintain polarity. swo B, E, G, and H are involved in later hyphal morphogenesis. Our results suggest that polarity establishment and polarity maintenance are genetically separate events and that a persistent signal is required for apical extension in A. nidulans.

Characterization of the antigenic determinant on Fusarium oxysporum recognized by a genus-specific monoclonal antibody

The antigenic determinant of a monoclonal antibody (MAb) (API9-2) having specific reactivity with the fungi grouped into the genus Fusarium was analyzed. The culture supernatant of the fungi showed antigenicity against MAb API9-2, proving that the antigen exists as an exoantigen. The heat-resistant, proteinase K-resistant and periodate oxidation-labile features of the antigenic determinant indicated its carbohydrate nature. Also, lectin affinity tests and thin-layer chromatography analysis suggested that the monosaccharide making up the antigenic determinant was mainly mannose. Considering previous reports that the antigen exists on the surface of mycelia (by immunofluorescence assay) and is a - 55 kDa molecule (by Western blotting analysis), it was concluded that the antigenic determinant of MAb API9-2 on F. oxysporum is a mannan component existing on the surface of mycelia.

The structures of polysaccharides and glycolipids of Aspergillus fumigatus grown in the presence of human serum

A study was made of polysaccharides and glycosphingolipids isolated from Aspergillus fumigatus grown in media supplemented with human serum from healthy donors. Fractionation of Cetavlon-precipitated polysaccharides on Sephacryl S-400 gave rise to an excluded fraction (Fraction I) with molecular weight of > 400 kDa and an included peak (Fraction II) with an average molecular weight of 30-80 kDa. Fraction I comprises about 5% of total polysaccharide and was identified as a glycogen-like molecule. Its structure was deduced from methylation data, treatment with amyloglucosidase, a red-brown coloration produced with an iodine solution and by 1H and 13C-NMR spectroscopy. It was previously suggested that higher amounts of glycogen-like polysaccharide (20%) were present in A. fumigatus grown in serum-free medium. Fraction II was identified as a galactomannan and was the main polysaccharide of A. fumigatus grown in serum-free medium. Fraction II was identified as a galactomannan and was the main 13C-NMR spectroscopy combined with partial acetolysis and methylation analysis. The 13C-NMR spectrum of the galactomannan showed a much greater complexity in the beta-D-gal f and alpha-D-man p C-1 regions, than was evident for galactomannan from serum-free cultures previously described, reflecting differences in the glycosylation pattern, stimulated in serum-supplemented medium. No differences in A. fumigatus glycosphingolipid could be detected between serum-containing and serum-free growth conditions. Our results demonstrate that the change in polysaccharide structure is a more specific response to the altered growth conditions and not merely a symptom of more general changes.

Monoclonal antibodies as probes for fungal wall structure during morphogenesis

Three monoclonal antibodies (mAbs), S4D1, S3B3 and S1E5, were produced from hybridoma cell lines raised from mice immunized with hyphal walls of Neurospora crassa and one (Pax-1) from mice immunized with hyphal walls of Paxillus involutus. In immunofluorescence studies, the three N. crassa mAbs recognized epitopes with different patterns of distribution at the hyphal surface of N. crassa. S4D1 recognized an epitope which was present on the surface of both conidia and hyphae; S3B3 recognized an epitope seen only at the ends of conidia or in the septal region of hyphae and conidial chains; and S1E5 recognized an epitope present on the surface of hyphae, but not on mature conidia. mAb Pax-1 reacted with hyphal wall fragments of Pax. involutus and with N. crassa conidia in a similar way to S3B3. S4D1 reacted with an epitope found in 1,3-alpha-glycan preparations from hyphal walls of different fungi. The surface distribution of this epitope varied: it was found on the surface of both conidia and hyphae of N. crassa and Aspergillus nidulans, on the basidiospore surface only of Amanita muscaria, and on the hyphae but not the conidia of Penicillium chrysogenum. Immunogold studies revealed that the epitope was present throughout the wall of conidia and hyphae of N. crassa. mAbs S3B3, S1E5 and Pax-1 also reacted with other fungi: for example Pax-1 cross-reacted with all fungi tested except for a member of the Zygomycota. Immunogold studies revealed that epitopes of these three mAbs were present within the inner layers of the walls of conidia and hyphae of N. crassa.

[Antifungal prophylaxis in neutropenic cancer patients and in allogeneic bone marrow transplantation]

Severe and prolonged neutropenia and fungal colonization during the long term administration of broad-spectrum antibiotics are well known factors increasing the risk of invasive fungal infections. This is in particular true in patients undergoing allgeneic bone marrow transplantation due to the intensity of the conditioning regimen, the immuno-suppressive effect of allografting and the administration of immunosuppressive agents to prevent graft-versus-host-disease. Therefore, strategies in the prevention of fungal infections decreasing the morbidity and mortality in patients with hematological malignancies need to be developed. In this review, we discussed fungal infections an important cause of morbidity and mortality in patients with hematological disorders and attempted to provide some insights in the current status of antifungal prophylaxis.

Immunohistochemical diagnosis of systemic bovine zygomycosis by murine monoclonal antibodies

Murine monoclonal antibodies (Mabs) against water-soluble somatic antigens (WSSA) and the wall fraction (WF) from Rhizopus arrhizus (Rhizopus oryzae) were produced in vitro by fusion of splenocytes from immunized BALB/c mice with mouse myeloma X63-Ag 8.653 cells. Supernatants reacting only with homologous antigens in an enzyme-linked immunosorbent assay were subsequently screened for reactivity with homologous fungi in immunohistochemical techniques. All four Mabs raised against the WF of A. arrhizus failed to react on tissues. However, four of the Mabs raised against the WSSA of R. arrhizus (Mab-WSSA-RA-1 through Mab-WSSA-RA-4) revealed a high homologous reactivity on tissues and the cross-reactivity of these were subsequently evaluated on tissues containing other members of the family Mucoraceae and other unrelated fungi. On tissues and on immunoblots all four Mabs reacted identically and specifically with members of the family Mucoraceae, i.e., Absidia corymbifera, R. arrhizus, and Rhizomucor pusillus. The Mabs were all isotyped as IgM antibodies, were nonprecipitating, and reacted with homologous antigens with molecular masses from I4 to 110 kDa. With WSSA from A. corymbifera and R. pusillus the four Mabs were bound to antigens from 14 to 52 kDa and from 20 to 28 kDa, respectively. The diagnosis of 145 bovine lesions obtained by one of the specific Mabs (Mab-WSSA-RA-1) were compared to results obtained by heterologously absorbed polyclonal antibodies. In most lesions (n = 140 [approximately 97%]) the Mab and the polyclonal antibodies reacted in a similar pattern, i.e., positively for zygomycosis in 89 lesions, negatively in 41 aspergillosis lesions, and negatively in 10 undiagnosed lesions. Hyphae within two of four lesions in lymph nodes, which were not stained by the polyclonal antibodies, reacted with the specific Mab. However, in another three lesions of lymph nodes stained by the polyclonal antibodies no reactivity was seen with the Mab-WSSA-RA-1. The immunoreactivity of the Mabs (Mab-WSSA-RA-1 through Mab-WSSA-RA-4) raised against WSSA of R. arrhizus justify their application for the in situ diagnosis of systemic bovine zygomycosis.

Development of murine monoclonal antibodies for the immunohistochemical diagnosis of systemic bovine aspergillosis

Murine monoclonal antibodies (MAbs) against water-soluble somatic antigens (WSSA) and the wall fraction (WF) from Aspergillus fumigatus were produced by fusion of splenocytes from immunized BALB/c mice with mouse myeloma X63-Ag 8.653 cells. The supernatants of in vitro cultured hybridomas were initially screened for reactivity with the WSSA and the WF from A. fumigatus and WSSA of other fungi in an enzyme-linked immunosorbent assay (ELISA). Supernatants reacting only with A. fumigatus antigens were subsequently screened for homologous and heterologous reactivity with immunohistochemical techniques using formalin-fixed, paraffin-embedded tissues from experimentally infected mice. Because of a high immunohistochemical reactivity with homologous fungi, 4 MAbs raised against A. fumigatus WSSA and WF were selected for a further evaluation of cross-reactivity (diagnostic specificity) in immunohistochemical and immunoblotting assays. In immunohistochemical assays, all MAbs raised against WSSA cross-reacted heavily with a number of other fungal species. All 4 MAbs (MAb-WF-AF-1-4) raised against the WF reacted strongly with hyphae of Aspergillus spp.; hyphae of Scedosporium apiospermum were also strongly labeled by MAb-WF-AF-3 and -4. The 2 specifically reacting MAbs (MAb-WF-AF-1 and -2) were of the IgM biotype and were precipitating, and in immunoblotting experiments both bound to a 106-kD antigen of the WF, whereas they did not bind to WSSA of A. fumigatus. One of the 2 aspergillosis-specific MAbs (MAb-WF-AF-1) was used to screen 145 mycotic lesions of cattle. The diagnoses on bovine lesions obtained by MAb-WF-AF-1 were compared with results based on reactivity with heterologously absorbed polyclonal antibodies and, for some lesions, to culture results. In the vast majority of lesions (n = 133), the MAb-WF-AF-1 and the polyclonal anti-Aspergillus antibodies reacted in a similar pattern, i.e., positively in 41 aspergillosis lesions and negatively in 92 zygomycotic lesions. Hyphae in 3 of 12 lesions that were not stained by the polyclonal antibodies reacted with the specific MAb-WF-AF-1; i.e., aspergillosis was diagnosed. The characteristics of the 2 MAbs (MAb-WF-AF-1 and -2) raised against the WF of A. fumigatus in ELISA and immunoblotting and immunohistochemical assays justify their application for the in situ diagnosis of systemic aspergillosis of cattle.

Monoclonal antibodies against a 97-kilodalton antigen from Aspergillus flavus

We prepared a panel of five monoclonal antibodies (MAbs) directed against Aspergillus flavus that all reacted against one 97-kDa antigen by western blot (immunoblot). Flow cytometry demonstrated that these antibodies bound (in increasing degrees) to all morphologic stages of A. flavus growth: conidia, swollen conidia, and hyphae. Cross-reactivity among species was examined by enzyme-linked immunosorbent assay of fungal culture filtrates. Four MAbs reacted with 10 of 11 A. flavus isolates, and the fifth one reacted with 9 of them. One MAb also reacted with A. fumigatus, two reacted with A. niger, A. wentii, and A. nidulans, and all five reacted with A. ochraceus. None reacted with A. terreus, A. glaucus, A. versicolor, or a Penicillium species. Each MAb bound to A. flavus hyphae in formalin-fixed paraffin sections of a muscle biopsy from a confirmed human case of invasive aspergillosis. In summary, these MAbs identified a 97-kDa antigen found on A. flavus that is both surface bound and an exoantigen. Either the same or a cross-reacting antigen is present in A. fumigatus and other Aspergillus species.

Fungal polysaccharides

Fungal polysaccharides are cell wall components which may act as antigens or as structural substrates. As antigens, the role of mannans in Saccharomyces cerevisiae and Candida albicans, and of glycoproteins in Aspergillus fumigatus are discussed. Analyses on beta-glucan synthetase in Paracoccidioides brasiliensis and the inhibitory effect of Hansenula mrakii killer toxin on beta-glucan biosynthesis are also considered.

Acquired immunity in experimental murine aspergillosis is mediated by macrophages

A number of studies have substantiated the pivotal role of innate defense mechanisms in protection against invasive aspergillosis. However, experiments demonstrating increased resistance to lethal intravenous (i.v.) infection with Aspergillus fumigatus conidia in cortisone-treated or untreated mice preinfected with a sublethal dose of conidia and protection of turkeys inoculated subcutaneously with a killed A. fumigatus germling vaccine against subsequent aerosol challenge led us to speculate that acquired immunity may also contribute to host defense against Aspergillus infection. Five-week-old male BALB/c mice were inoculated i.v. with 1.0 x 10(4) viable conidia or saline and challenged i.v. with 1.0 x 10(6) conidia after 7, 15, or 21 days. No protection against challenge was found after 7 days. However, significant and reproducible protection was observed after 15 and 21 days. Mortality was reduced from 90% in control mice to 53% in preinfected mice 40 days after challenge (P = 0.0002). Increased survival was correlated with decreased content of chitin in lungs, liver, and kidneys 4 and 7 days after challenge (P < 0.05). Mice were again inoculated with 1.0 x 10(4) conidia or saline, and after 21 days, 1.0 x 10(8) or 2.0 x 10(8) splenocytes were transferred to naive syngeneic recipients; 2.0 x 10(8) immune splenocytes conferred significant protection (P = 0.0001) against i.v. challenge with 1.0 x 10(6) conidia, and mortality decreased from 83 to 48% 40 days after challenge. Transfer of immune serum offered no protection despite the presence of antibody against a hyphal homogenate of A. fumigatus, which was absent in the sera of control mice. Protection by immune splenocytes was maintained after selective depletion of T cells but was abolished after removal of plastic-adherent splenocytes. Adherent cells were characterized as macrophages by using morphological criteria, nonspecific esterase, and MAC-1 monoclonal antibody. Production of hydrogen peroxide by peritoneal and splenic macrophages from preinfected mice was the same as and lower than, respectively, that from uninfected controls. However, phagocytosis of conidia by peritoneal or splenic macrophages from mice preinfected i.v. or intratracheally was significantly increased after 2 and 3 h of coculture compared with that from uninfected animals, whereas in vitro killing of conidia by splenic macrophages was unaltered. Peritoneal or splenic macrophages from control or preinfected mice failed to kill hyphae in vitro. Killing of hyphae by polymorphonuclear leukocytes was not significantly different between mice preinfected i.v. and uninfected controls. Taken together, the results indicate that acquired immunity mediated by activated macrophages can be demonstrated in experimental murine aspergillosis.(ABSTRACT TRUNCATED AT 400 WORDS)

Heterogeneity of the purified extracellular aspartyl proteinase from Candida albicans: characterization with monoclonal antibodies and N-terminal amino acid sequence analysis

Three dominant proteins (41, 48, and 49 kDa) were detected by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) in purified preparations of the extracellular aspartyl proteinase (AP) of Candida albicans. All three proteins bound to the specific carboxyl proteinase ligand, pepstatin A, and were associated with maximum AP activity. The N-terminal amino acid sequence for the 48- and 49-kDa proteins matched that reported by others for AP, whereas the sequence for the 41-kDa protein was unique and was not homologous to any known protein. Time course studies demonstrated the simultaneous presence of all three proteins, supporting evidence that the 41- and 48-kDa proteins were not breakdown products of AP. Previous studies did not detect carbohydrate in SDS-polyacrylamide gels of purified AP preparations stained with periodic acid and silver, making glycosylation an unlikely explanation for the observed differences in the molecular masses of the proteins. Some monoclonal antibodies directed against the 49-kDa protein reacted with the 41- and 48-kDa proteins, indicating cross-reactive epitopes. Other monoclonal antibodies, however, reacted only with the 49-kDa protein. We conclude that three pepstatin A-binding proteins occur in purified AP preparations: two have the same amino acid N terminus as that reported for AP, whereas the third has a unique sequence. All three proteins should be considered when undertaking studies to determine the role of AP in candidal pathogenesis or when preparing specific antibodies for antigen capture assays.

Specificity analysis of antibodies formed in rabbits to a mannosyl trisaccharide: similarity with lectin binding activity. Para-aminophenyl O-alpha-D-mannopyranosyl-(1-->2)-alpha-D-mannopyranosyl- (1-->6)-alpha-D-mannopyranoside linked to bovine serum albumin as an antigen

The para-aminophenyl derivative of Man alpha 1-->2Man alpha 1-->6Man alpha 1-->was coupled via a diazotization reaction to bovine serum albumin, and the resulting glycoconjugate was used to immunize two rabbits. The resultant antisera were tested for reactivity with a number of related mono, di- and trisaccharides to determine the immunodominant portion of this trisaccharide. Two populations of antibody resulted, one of which required the reducing end mannose, and could react with either an N-acetylglucosamine or a mannose as the penultimate sugar. The other population reacted with the Man alpha 1-->2Man alpha 1-->6Man alpha 1-->. The aglycone moiety and its configurations play an important role in determining the specificity of antibodies to this synthetic antigen. The similarity of this reactivity to the reactivity of mannose binding lectins is discussed.

Rat monoclonal antibodies against Aspergillus galactomannan

Monoclonal antibodies (MAbs) against Aspergillus fumigatus galactomannan were produced in rats. Seven of them, EB-A1 through EB-A7, were characterized in more detail. They were all immunoglobulin M antibodies, reacting in an indirect enzyme-linked immunosorbent assay with purified A. fumigatus galactomannan, with avidity constants of between 2 x 10(9) and 5 x 10(9)/M. Enzyme-linked immunosorbent assay inhibition experiments with modified galactomannan and synthetic oligomers of beta (1----5)galactofuranose demonstrated that the MAbs bound to an epitope located on the beta(1----5)galactofuranose-containing side chains of the galactomannan molecule. An identical or similar epitope also seemed to be present in other fungi. Immunofluorescence and immunoelectron microscopy experiments with EB-A2 revealed the presence of the antigen in the fungal wall and inside the cell. Immunoblotting experiments demonstrated that the epitope recognized by the MAbs was a common oligosaccharide moiety of a wide range of intracellular and extracellular glycoproteins in A. fumigatus. The characteristics of the MAbs justify their use in the diagnosis of invasive aspergillosis by antigen detection.

Immunodiagnosis of aspergillosis

Aspergillus species are ubiquitous fungi and have been implicated as the causative agents of a variety of lung disorders in humans. These disorders include allergic, saprophytic, and systemic manifestations. The allergic disorders mainly affect atopic persons, and invasive or systemic diseases affect immunosuppressed individuals. Immunodiagnosis can help the practitioner diagnose these diseases. Demonstration of circulating antibodies is a useful criterion, but the lack of dependable and standardized antigens is a limiting factor in the diagnosis of most Aspergillus-induced diseases. Despite this limitation, however, immunodiffusion and enzyme-linked immunosorbent assays have been widely used for the detection of antibodies in the sera of patients with aspergillosis. Similarly, crude and semipurified antigens are being used to demonstrate skin hypersensitivity in patients, and several methods have been useful in the detection of antigenemia in patients with invasive aspergillosis. With a growing number of reports on the incidence of aspergillosis and an increase in the number of immunosuppressed individuals in the population, more rapid methods and more reliable reagents for immunodiagnosis are needed. With recent attempts at obtaining reliable reagents for through hybridoma technology and molecular biological techniques, substantial progress toward efficient immunodiagnosis may be achieved.

The 18-kilodalton antigen secreted by Aspergillus fumigatus

One of the major antigens secreted in vitro by Aspergillus fumigatus is an 18-kDa basic protein which has been purified by cation-exchange chromatography. It is recognized by sera from aspergilloma patients. It is also the major circulating antigen found in urine of patients with invasive aspergillosis. Our results indicated that this antigen has potential for the diagnosis of both aspergilloma and invasive aspergillosis.