Extraction, Characterization, and Immunological Adjuvant Effect Evaluation of Δlpxl E. coli Outer Membrane Vesicles

The preparation of specific antibodies is of critical importance in the immunoassay of small-molecule contaminants in food. However, due to the lack of immunogenicity, these small molecules must be conjugated to a carrier to form complete antigen in order to induce the generation of antibodies, and adjuvants are typically required during the immunization when traditional proteins were used as carriers. Therefore, identifying a substance that possesses both the characteristics of carrier and adjuvant is of significant research importance for antibody preparation. Outer membrane vesicles (OMVs) are nanoscale particles with a bilayer membrane and spherical structure produced by Gram-negative bacteria through natural budding. They contain various pathogen-associated molecular patterns (PAMPs), which could be recognized by pattern recognition receptors (PRRs) on the surface of immune cells, thereby triggering a robust immune response. In this study, OMVs derived from Δ lpxl E. coli and chloramphenicol sodium succinate (CSS) were used as the carrier and hapten to synthesize the complete chloramphenicol (CAP) antigen (CSS-Δ lpxl -OMV). BALB/c mice were subsequently immunized with this antigen to generate antibodies, with the aim of evaluating the adjuvant effects of Δ lpxl -OMV and its potential as a hapten carrier. The results indicated that Δ lpxl -OMV not only served as a carrier for binding the hapten to prepare the complete antigen but also exhibited significant adjuvant properties. The synthesized complete antigen possessed significant immunogenicity and could induce the mice to produce antibodies against the target without additional adjuvants.