Development of Immunoassays for the Detection and Quantification of Fungi

Abstract

The development of immunoassays for the detection and quantification of fungi has been slow; this has been mainly because of the difficulties encountered in raising antisera to fungi that are species-specific. Antisera raised to mycelial fragments, extracts from lyophilized mycelia, surface washings of solid cultures or culture filtrates generally cross-react with both related and unrelated fungi and host tissues or their extracts when tested by enzyme linked imunosorbent assays (ELISA) or by immunofluorescence (IMF)(Dewey, 1989a, Mohan, 1988; Xia et al., 1992). Fungi share many common molecules and binding sites (epitopes) with each other and with their hosts i.e. common antigens (Devay & Adler, 1976; Chakraborty & Sinha, 1994). Attempts to improve specificities, by using, as immunogens, purified fractions from fungi such as hyphal walls, have been only partially successful. However, Notermans et al.(1987), working with fungi causing spoilage of foods, have raised genus-specific antisera by using the soluble carbohydrates extracted from supernatants of fungi grown in liquid culture as the immunogen. Removal of cross-reactive antibodies by cross-absorption with antigens from related species is not satisfactory because the titre is usually severely lowered (Gerik et al., 1987).