Comparative Detection of Fumonisin by HPLC, ELISA, and Immunocytochemical Localization in Fusarium Cultures

Fumonisins are a group of mycotoxins that are elaborated by Fusarium moniliforme and Fusarium proliferatum and that have recently been associated with animal and human disease. In this study, the time course of fumonisin B₁ (FB₁) production in corn was monitored in five Fusarium cultures using high-performance liquid chromatography (HPLC), enzyme-linked immunosorbent assay (ELISA), and in situ localization by an enzyme-linked immunocytochemical technique (ELICT). Using HPLC on culture extracts prepared with 50% (vol/vol) acetonitrile in water, FB₁ was detectable at 3 days with maximal FB₁ (ranging from 230 to 3,000 ppm) occurring between 14 and 28 days. Although there was a positive correlation between FB₁ detected by HPLC and ELISA, the latter consistently yielded higher results than HPLC. Maximal FB₁ "equivalents" detected by ELISA ranged from 12,000 to 35,000 ppm. Following fixation of Fusarium from cultures, ELICT revealed the presence of large deposits indicative of fumonisin or fumonisin-like cross-reacting compounds in mycelia, microconidia, and microconidia. Prior to fixation, these compounds were extractable in 50% (vol/vol) acetonitrile in water. ELICT results qualitatively correlated with HPLC and ELISA over the time course of the cultures. Taken together, the results suggest that (a) ELISA or ELICT could be used for qualitative screening of FB₁-producing cultures, and (b) in addition to FB₁, the monoclonal antibody-based ELISA detected one or more compounds that structurally resemble FB₁ and occur concurrently with FB₁.