title: Chicken single-chain antibody fused to alkaline phosphatase detects Aspergillus pathogens and their presence in natural samples by direct sandwich enzyme-linked immunosorbent assay.
abstract: A sensitive and specific analytical method to detect ubiquitous aflatoxigenic Aspergillus pathogens is essential for monitoring and controlling aflatoxins. Four highly reactive chicken single-chain variable fragments (scFvs) against soluble cell wall proteins (SCWPs) from Aspergillus flavus were isolated by phage display. The scFv antibody AfSA4 displayed the highest activity toward both A. flavus and A. parasiticus and specifically recognized a surface target of their cell walls as revealed by immunofluorescence localization. Molecular modeling revealed a unique compact motif on the antibody surface mainly involving L-CDR2 and H-CDR3. As measured by surface plasmon resonance, AfSA4 fused to alkaline phosphatase had a higher binding capability and 6-fold higher affinity compared with AfSA4 alone. Immunoblot analyses showed that the fusion had good binding capacity to SCWP components from the two fungal species. Direct sandwich enzyme-linked immunosorbent assays with mouse antiaspergillus monoclonal antibody mAb2A8 generated in parallel as a capture antibody revealed that the detection limit of the two fungi was as low as 10(-3) μg/mL, 1000-fold more sensitive than that reported previously (1 μg/mL). The fusion protein was able to detect fungal concentrations below 1 μg/g of maize and peanut grains in both artificially and naturally contaminated samples, with at least 10-fold more sensitivity than that reported (10 μg/g) thus far. Thus, the fusion can be applied in rapid, simple, and specific diagnosis of Aspergillus contamination in field and stored food/feed commodities.
authors.affiliation: Molecular Biotechnology Laboratory of Triticeae Crops, Huazhong Agricultural University , Wuhan 430070, China.
authors.forename: Sheng
authors.initials: S
authors.lastname: Xue
authors.forename: He-Ping
authors.initials: HP
authors.lastname: Li
authors.forename: Jing-Bo
authors.initials: JB
authors.lastname: Zhang
authors.forename: Jin-Long
authors.initials: JL
authors.lastname: Liu
authors.forename: Zu-Quan
authors.initials: ZQ
authors.lastname: Hu
authors.forename: An-Dong
authors.initials: AD
authors.lastname: Gong
authors.forename: Tao
authors.initials: T
authors.lastname: Huang
authors.forename: Yu-Cai
authors.initials: YC
authors.lastname: Liao
mesh_terms: D000469:Alkaline Phosphatase / Q000235:genetics / Q000276:immunology* / Q000378:metabolism; D000595:Amino Acid Sequence; D000818:Animals; D000911:Antibodies, Monoclonal / Q000235:genetics / Q000276:immunology* / Q000378:metabolism; D010367:Arachis / Q000737:chemistry / Q000382:microbiology; D001228:Aspergillosis / Q000175:diagnosis* / Q000276:immunology / Q000382:microbiology; D001230:Aspergillus / Q000472:pathogenicity*; D002645:Chickens; D004797:Enzyme-Linked Immunosorbent Assay; D005260:Female; D005455:Fluorescent Antibody Technique; D005506:Food Contamination / Q000032:analysis*; D051379:Mice; D008807:Mice, Inbred BALB C; D008969:Molecular Sequence Data; D019151:Peptide Library; D011487:Protein Conformation; D017386:Sequence Homology, Amino Acid; D057127:Single-Chain Antibodies / Q000235:genetics / Q000276:immunology* / Q000378:metabolism; D003313:Zea mays / Q000737:chemistry / Q000382:microbiology
chemical_list: D000911:Antibodies, Monoclonal; D019151:Peptide Library; D057127:Single-Chain Antibodies; D000469:Alkaline Phosphatase