Temming, A. R. | bioRxiv Science

bioRxiv2026

Monoclonal antibody-based serotyping of Listeria monocytogenes provides new insights in epidemiology and virulence

ObjectivesListeria monocytogenes is an opportunistic pathogen, associated with foodborne infections that disproportionately affect newborns, elderly and immunocompromised patients. L. monocytogenes can be classified on the antigenic and related structural variation of cell-associated wall teichoic acid (WTA) molecules through conventional serotyping techniques. The WTA structure of serovars (SV) 1/2, 1/2*, 3 and 7 consists of a linear poly-ribitolphosphate (RboP) polymer either with or without decoration with rhamnose (Rha) and/or N-acetylglucosamine (GlcNAc). Of these four SVs, SV1/2 (WTA with GlcNAc and Rha) causes [~] 99% of all listeriosis cases. However, conventional serotyping cannot accurately discriminate between these four SVs, particularly SVs1/2* (WTA with Rha). MethodsHere we applied two identified monoclonal antibodies (mAb), with specificity for the RboP backbone or GlcNAc modification to develop a discriminatory serotyping scheme for SV1/2, 1/2*, 3 and 7. Isogenic mutants for the different SVs were created in L. monocytogenes SV1/2 strain EGD-e. The typing scheme was then adapted to an immnoblot assay and applied to a collection of 317 previously classified listeriosis isolates from the Netherlands Reference Laboratory for Bacterial Meningitis. ResultsBinding of the RboP-specific mAb was limited to EGD-e wild type (SV1/2), but increased significantly for isogenic EGD-e mutants representing SV1/2*, 3 and 7. In contrast, the GlcNAc-specific mAb only recognized EGD-e mutants representing SVs 1/2 and 3. The combined staining profiles of the two mAbs allowed accurate discrimination of the four SVs as verified on clinical isolates. Applying this typing scheme to 317 listeriosis isolates previously typed as SV1/2, we confirmed SV designation in >90% of isolates, but also identified SV1/2* (5.4%), SV3 (0.6%) and SV7 (0.3%) isolates. SV1/2* isolates were also identified among meningitis patients. ConclusionThe increased discriminatory capacity of L. monocytogenes serotyping provides a more detailed insight of the epidemiological landscape and the critical factors for L. monocytogenes infections.

microbiology↗

bioRxiv2025

Platform for Identifying Human Glycan-Specific Antibodies Against Bacterial Pathogens using Synthetic Glycan Fragments

Bacterial infections represent a substantial global health challenge, impacting both human and veterinary health. The ongoing evolution of antibiotic-resistant pathogens, coupled with limited new antibiotic discoveries, urges the need for alternative strategies to treat and prevent these infections. Passive immunization with monoclonal antibodies (mAbs) is gaining interest as a promising alternative. Here, we report an experimental pipeline for generating human mAbs from healthy donor B cells using synthetic mimics of complex bacterial glycans. We identified functional mAbs recognizing discrete and unique epitopes on the surface glycans of two bacterial priority pathogens; Staphylococcus aureus and Streptococcus pyogenes. The use of chemically-defined synthetic glycans was critical for the discovery and systematic characterization of mAbs. From a heterogeneous mix of B cell specificities, mAbs were isolated with reactivities against immunodominant but also to less common or even masked epitopes. The pipeline can be adapted to different glycan targets, donor material or specific antibody isotypes. This work thereby paves the way for the discovery of glycan-specific mAbs with clinical relevance to treat, prevent or diagnose infections with S. aureus, S. pyogenes or other bacterial pathogens.

microbiology↗