Utility of Aspergillus antigen detection in specimens other than serum specimens

Department of Medical Microbiology, University Medical Center St. Radboud, Nijmegen, The Netherlands.
Clinical Infectious Diseases (Impact Factor: 9.42). 12/2004; 39(10):1467-74. DOI: 10.1086/425317
Source: PubMed

ABSTRACT The detection of circulating galactomannan in serum is an important tool for the early diagnosis of invasive aspergillosis. A commercial enzyme-linked immunosorbent assay (Platelia Aspergillus; BioRad) was shown to be both highly sensitive and specific for detection of galactomannan in serum samples. Despite the fact that this assay is validated for serum samples, specimens of other body fluids are increasingly used for detection of galactomannan, including urine, bronchoalveolar lavage fluid, and cerebrospinal fluid. Review of the literature shows that galactomannan can be detected in each of these samples from patients with invasive aspergillosis with higher sensitivity than is the case with culture, as well as early in the course of infection. However, the evidence thus far is based on case reports--predominantly retrospective studies--that often include heterogeneous patient populations and limited numbers of cases of proven infection. Clearly, well-designed prospective studies with systematic sampling and use of consensus case definitions are needed to compare the performance of antigen detection in samples other than serum specimens with that in serum specimens.

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    ABSTRACT: The cells walls of filamentous fungi in the genus Aspergillus have galactofuranose-containing polysaccharides and glycoconjugates, including O-glycans, N-glycans, fungal-type galactomannan, and glycosylinositolphosphoceramide, which are important for cell wall integrity. Here, we attempted to identify galactofuranosyltransferases that couple galactofuranose monomers onto other wall components in Aspergillus nidulans. Using reverse-genetic and biochemical approaches, we identified that the AN8677 gene encoded a galactofuranosyltransferase, which we called GfsA, involved in galactofuranose (Galf) antigen biosynthesis. Disruption of gfsA reduced binding of β-Galf-specific antibody EB-A2 to O-glycosylated WscA protein and galactomannoproteins. The results of an in-vitro galactofuranose antigen synthase assay revealed that GfsA has β1,5- or β1,6- galactofuranosyltransferase activity for O-glycans in glycoproteins, uses UDP-D-galactofuranose as a sugar donor, and requires a divalent manganese cation for activity. GfsA was found to be localized at the Golgi apparatus based on cellular fractionation experiments. ΔgfsA cells exhibited an abnormal morphology characterized by poor hyphal extension, hyphal curvature, and limited formation of conidia. Several gfsA orthologs were identified in members of the Pezizomycotina subphylum of Ascomycota, including the human pathogen Aspergillus fumigatus. To our knowledge, this is the first characterization of a fungal β-galactofuranosyltransferase, which was shown to be involved in galactofuranose antigen biosynthesis of O-glycans in the Golgi.
    Molecular Microbiology 10/2013; 90(5). DOI:10.1111/mmi.12416 · 5.03 Impact Factor
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    ABSTRACT: We conducted a single-center retrospective cohort study to determine the performance characteristics of the galactomannan (GM) assay in bronchoalveolar lavage (BAL) in patients with hematologic malignancies. Patients were classified as proven, probable, possible, or no invasive pulmonary aspergillosis (IPA), according to international guidelines. A total of 173 BAL samples from 145 patients were included. There were 5 proven, 7 probable, and 35 possible cases of IPA. Using a GM index cutoff of ≥ 0.5, the sensitivity, specificity, and positive and negative predictive values (PPV and NPV, respectively) of the BAL GM assay were 100%, 78%, 26%, and 100%, respectively. Using a GM index cutoff of ≥ 2.0, the sensitivity and NPV remained 100%, but specificity and PPV increased to 93% and 50%, respectively. The BAL GM assay is a highly sensitive screening test for IPA in patients with hematologic malignancies. Increasing the cutoff value to 2.0 would improve the performance of this assay.
    Diagnostic microbiology and infectious disease 10/2010; 68(2):132-9. DOI:10.1016/j.diagmicrobio.2010.03.017 · 2.57 Impact Factor
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    ABSTRACT: Invasive aspergillosis (IA) caused by the fungus Aspergillus fumigatus is a frequent and life-threatening complication of chemotherapy and bone marrow transplantation with high rates of mortality and morbidity. Diagnosis of IA is complex and can only be confirmed by identification of the fungus in biopsy samples. Capturing tissue for diagnosis is in itself hazardous, and because of this many patients receive empirical antifungal treatment rather than undergo biopsy. However, the treatment carries with it significant side effects and is prohibitively expensive. Because of this, attempts have been made to develop specific and sensitive diagnostic tests that can be used to track the early onset of infection and permit rational administration of antifungal drugs. Early attempts at nonculture-based diagnosis using human immune serum to detect circulating Aspergillus antigens proved unreliable, and so focus turned to hybridoma technology and the use of monoclonal antibodies (MAbs) to detect signature molecules of infection. Detection of one such signature molecule, galactomannan (and associated galactomannoprotein molecules), forms the basis of the commercial Platelia enzyme immunoassay (EIA), an assay that has found widespread use in IA diagnosis. Nevertheless, concerns surrounding its accuracy mean that alternative strategies to diagnosis have been sought including detection of the fungal cell wall component (1-->3)-beta-d-glucan and polymerase chain reaction (PCR). The poor specificity of "panfungal" (1-->3)-beta-d-glucan tests and current lack of standardization of PCR assays have led to the recent development of next-generation MAb-based assays that detect surrogate markers of infection and that have been incorporated into "point-of-care" diagnostic devices. This chapter examines the development of antibody-antigen, (1-->3)-beta-d-glucan, and nucleic acid-based approaches to IA detection, current concerns surrounding accurate disease diagnosis, and how animal models of infection can be used to inform assay development and validation.
    Advances in applied microbiology 01/2010; 70:187-216. DOI:10.1016/S0065-2164(10)70006-X · 2.24 Impact Factor


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