Amide-containing neoepitopes: the key factor in the preparation of hapten-specific antibodies and a strategy to overcome

A new strategy to generate nanobodies for the coumaphos based on the synthesized nanobody libraries

To break through the bottleneck in preparation of nanobody (Nb) for chemical contaminants induced by the difficulties in the synthesis of immunogen, complexity and unexpectable efficiency of immunization, a novel strategy to generate Nbs based on the designed synthetic Nb libraries with final size up to 109 cfu/mL was adopted and succeeded in selection of anti-coumaphos Nb A4. Furthermore, an affinity-matured mutant Nb 3G was obtained from the secondary library. Finally, an ic-ELISA was established with the limit of detection for coumaphos low to 1.90 ng/mL, 6.4-fold improved than the parent Nb A4, and the detection range from 3.06 to 15.77 ng/mL. Meanwhile, the recovery rate of vegetable samples was from 89.9% to 98.5%. Finally, the accuracy was testified by the standard UPLC-MS/MS method with R2 up to 0.99. Overall, fully synthetic Nb libraries constructed in this work provided an alternative possibility to generate the specific Nbs for chemical contaminants.

Development of an immunoassay based on a specific antibody for the detection of diphenyl ether herbicide fomesafen

Fomesafen belongs to the diphenyl ether herbicide, and is widely used in the control of broadleaf weeds in crop fields due to its high efficiency and good selectivity. The residual of fomesafen in soil has a toxic effect on subsequent sensitive crops and the microbial community structure because of its long residual period. Therefore, an efficient method for detecting fomesafen is critical to guide the correct and reasonable use of this herbicide. Rapid and sensitive immunoassay methods for fomesafen is unavailable due to the lack of specific antibody. In this study, a specific antibody for fomesafen was generated based on rational design of haptens and a sensitive immunoassay method was established. The half maximal inhibitory concentration (IC50) of the immunoassay was 39 ng/mL with a linear range (IC10-90) of 1.92-779.8 ng/mL. In addition, the developed assay had a good correlation with the standard UPLC-MS/MS both in the spike-recovery studies and in the detection of real soil samples. Overall, the developed indirect competitive enzyme immunoassay reported here is important for detecting and quantifying fomesafen contamination in soil and other environmental samples with good sensitivity and high reproducibility.

Cross-reaction mediated by distinct key amino acid combinations in the complementary-determining region (CDR) of a monoclonal antibody

In immunology, cross-reaction between antigens and antibodies are commonly observed. Prior research has shown that various monoclonal antibodies (mAbs) can recognize a broad spectrum of epitopes related to influenza viruses. However, existing theories on cross-reactions fall short in explaining the phenomena observed. This study explored the interaction characteristics of H1-74 mAb with three peptides: two natural peptides, LVLWGIHHP and LPFQNI, derived from the hemagglutinin (HA) antigen of the H1N1 influenza virus, and one synthetic peptide, WPFQNY. Our findings indicate that the complementarity-determining region (CDR) of H1-74 mAb comprised five antigen-binding sites, containing eight key amino acid residues from the light chain variable region and 16 from the heavy chain variable region. These critical residues formed distinct hydrophobic or hydrophilic clusters and functional groups within the binding sites, facilitating interaction with antigen epitopes through hydrogen bonding, salt bridge formation, and π-π stacking. The study revealed that the formation of the antibody molecule led to the creation of binding groups and small units in the CDR, allowing the antibody to attach to a variety of antigen epitopes through diverse combinations of these small units and functional groups. This unique ability of the antibody to bind with antigen epitopes provides a new molecular basis for explaining the phenomenon of antibody cross-reaction.