Biology subjects

van Dalen, R.

Publications and source records attributed to van Dalen, R..

8 recordsLinked to original sources

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

CLR-Seq: a pipeline to identify bacterial microbiota species with immunomodulatory potential through human C-type lectin receptor interaction

Bacterial glycans are key components in immune interactions. We lack insight into the diverse glycan landscape present in complex microbial communities since currentomics techniques do not capture this post-translational information. Here we employed C-type lectin receptors (CLRs), which are dedicated innate glycan-sensing receptors, as probes for bacterial cell sorting in combination with 16S rRNA gene sequencing to identify microbiota species with a specific CLR-reactive glycan profile. We established our experimental CLR-sequencing (CLR-seq) pipeline using soluble fluorescently-labeled human macrophage galactose C-type lectin (MGL, CD301) and langerin (CD207). Both receptors identified known langerin- or MGL-interacting Staphylococcus aureus strains in a synthetic microbial community even when present at low abundance. Subsequent application of CLR-seq on fecal microbiota samples from healthy donors identified specific langerin- and MGL-interacting bacterial species that were subsequently validated as monocultures. In summary, CLR-seq is a modular platform that allows identification of human microbiota species based on CLR-interacting glycans with easy expansion to other CLRs or microbiota samples from patients. Given that CLRs are densely expressed on dendrites of antigen-presenting cells, this pathway may play a role in cross-barrier recognition and sampling of the environment during homeostasis.

microbiology↗

bioRxiv2024

The two-component system ArlRS is essential for wall teichoic acid glycoswitching in Staphylococcus aureus

Staphylococcus aureus is among the leading causes of hospital-acquired infections. Critical to S. aureus biology and pathogenesis are the cell wall-anchored glycopolymers wall teichoic acids (WTA). Approximately one-third of S. aureus isolates decorates WTA with a mixture of 1,4- and {beta}1,4-N-acetylglucosamine (GlcNAc), which requires the dedicated glycosyltransferases TarM and TarS, respectively. Environmental conditions, such as high salt concentrations, affect the abundance and ratio of 1,4- and {beta}1,4-GlcNAc WTA decorations, thereby impacting biological properties such as antibody binding and phage infection. To identify regulatory mechanisms underlying WTA glycoswitching, we screened 1,920 S. aureus mutants (Nebraska Transposon Mutant Library) by immunoblotting for differential expression of WTA-linked 1,4- or {beta}1,4-GlcNAc using specific monoclonal antibody Fab fragments. Three two-component systems (TCS), GraRS, ArlRS, and AgrCA, were among the 230 potential hits. Using isogenic TCS mutants, we demonstrated that ArlRS is essential for WTA {beta}1,4-GlcNAc decoration through regulation of tarM but not tarS. ArlRS regulated tarM expression through the transcriptional regulator MgrA, which was responsive to Mg2+, but not Na+. Importantly, ArlRS-mediated regulation of WTA glycosylation affected S. aureus interaction with the innate receptor langerin and lysis by {beta}1,4-GlcNAc-dependent phages. Since WTA represents a promising target for future immune-based treatments and vaccines, our findings provide important insight to align targeting strategies with the S. aureus WTA glycosylation patterns during infection. ImportanceStaphylococcus aureus is a common colonizer of mucosal surfaces, but is also a frequent cause of severe infections in humans. Development of antibiotic resistance complicates treatment of S. aureus infections, increasing the need for antibiotic alternatives such as vaccines and therapies with bacterial viruses also known as phages. Wall teichoic acids (WTA) are abundantly-expressed glycosylated structures of the S. aureus cell wall that have gained attention as a promising target for new treatments. Importantly, WTA glycosylation patterns show variation depending on environmental conditions, thereby impacting phage binding and interaction with host factors, such as antibodies and innate pattern-recognition receptors. Here, we show that the two-component system ArlRS through its effector MgrA is involved in regulation of WTA glycosylation by responding to environmental changes in Mg2+ concentration. These findings may support the design of new treatment strategies that target WTA glycosylation patterns of S. aureus during infection.

microbiology↗

bioRxiv2023

The capsular polysaccharide obstructs wall teichoic acid functions in Staphylococcus aureus

BackgroundThe cell envelope of Staphylococcus aureus contains two major secondary cell wall glycopolymers: capsular polysaccharide (CP) and wall teichoic acid (WTA). Both the CP and the WTA are attached to the cell wall and play distinct roles in S. aureus colonization, pathogenesis, and bacterial evasion of host immune defenses. ObjectiveWe aimed to investigate whether CP interferes with WTA-mediated properties. MethodsStrains with natural heterogeneous expression of CP, strains with homogeneous high CP expression and CP-deficient strains were compared to WTA deficient controls regarding WTA dependent phage binding, cell adhesion, IgG deposition, and virulence in vivo. ResultsWTA-mediated phage adsorption, specific antibody deposition and cell adhesion were negatively correlated with CP expression. WTA, but not CP, enhanced the bacterial burden in a mouse abscess model, while CP overexpression resulted in intermediate virulence in vivo. ConclusionsCP protects the bacteria from WTA-dependent opsonization and phage binding. This protection comes at the cost of diminished adhesion to host cells. The highly complex regulation and mostly heterogeneous expression of CP has probably evolved to ensure the survival and optimal physiological adaptation of the bacterial population as a whole.

microbiology↗

bioRxiv2022

Targeting of the human nasal microbiota by secretory IgA antibodies

The human nasal microbiome is critical for health and disease, since it is associated with the occurrence of respiratory disorders and hosting of opportunistic pathogens. The host therefore protects this vulnerable mucosal barrier from infection and maintains homeostasis of the microbiota through various mechanisms, including the production of secretory IgA (sIgA) antibodies. However, we currently lack a comprehensive understanding of how sIgA affects the nasal microbiota. Through IgA-seq analysis of nasal microbiome samples and sIgA deposition experiments using nasal sIgA from healthy volunteers, we identified which bacterial genera and species are targeted by sIgA on the level of the individual host. We observed that the amount of sIgA secreted into the nasal mucosa by the host varied substantially and was negatively correlated with the bacterial density. The interaction between mucosal sIgA antibodies and the nasal microbiome was highly individual, and was not dependent on the microbiome composition, or the age or gender of the host. Importantly, we showed that for the clinically relevant opportunistic pathogen S. aureus, sIgA reactivity was in part the result of epitope-independent interaction of sIgA with the antibody binding protein SpA through binding of sIgA Fab regions. This study thereby offers a first comprehensive insight of targeting of nasal microbiota by sIgA antibodies, which may help to better understand the shaping and homeostasis of the nasal microbiome by the host and offer new targets for intervention in disease-associated microbiota.

microbiology↗

bioRxiv2020

The impact of Staphylococcus aureus cell wall glycosylation on langerin recognition and Langerhans cell activation

Staphylococcus aureus is the leading cause of skin and soft tissue infections. It remains incompletely understood how skin-resident immune cells respond to S. aureus invasion and contribute to an effective immune response. Langerhans cells (LCs), the only professional antigen-presenting cell type in the epidermis, sense S. aureus through their pattern-recognition receptor langerin, triggering a pro-inflammatory response. Langerin specifically recognizes the {beta}-1,4-linked N-acetylglucosamine ({beta}-GlcNAc) modification, which requires the glycosyltransferase TarS, on the cell wall glycopolymer Wall Teichoic Acid (WTA). Recently, an alternative WTA glycosyltransferase, TarP, was identified in methicillin-resistant S. aureus strains belonging to clonal complexes (CC) 5 and CC398. TarP also modifies WTA with {beta}-GlcNAc but at the C-3 position of the WTA ribitol phosphate (RboP) subunit. Here, we aimed to unravel the impact of {beta}-GlcNAc linkage position for langerin binding and LC activation. In addition, we performed structure-binding studies using a small panel of unique chemically-synthesized WTA molecules to assess langerin-WTA binding requirements. Using FITC-labeled recombinant human langerin and genetically-modified S. aureus strains, we observed that langerin similarly recognized bacteria that produce either TarS- or TarP-modified WTA. Furthermore, using chemically-synthesized WTA, representative of the different S. aureus WTA glycosylation patterns, established that {beta}-GlcNAc is sufficient to confer langerin binding. Functionally, tarP-expressing S. aureus induce increased cytokine production and maturation of in vitro-generated LCs compared to tarSexpressing S. aureus. Overall, our data suggest that LCs are able to sense all {beta}-GlcNAc-WTA producing S. aureus strains, likely performing an important role as first responders upon S. aureus skin invasion.

microbiology↗

bioRxiv2018

A specific, glycomimetic Langerin ligand for human Langerhans cell targeting

Langerhans cells are a subset of dendritic cells residing in the epidermis of the human skin. As such, they are key mediators of immune regulation and have emerged as prime targets for novel transcutaneous cancer vaccines. Importantly, the induction of protective T cell immunity by these vaccines requires the efficient and specific delivery of both tumor-associated antigens and adjuvants. Langerhans cells uniquely express Langerin (CD207), an endocytic C-type lectin receptor. Here, we report the discovery of a specific, glycomimetic Langerin ligand employing a heparin-inspired design strategy that integrated NMR spectroscopy and molecular docking. The conjugation of these glycomimetics to liposomes enabled the specific and efficient targeting of Langerhans cells in the human skin. This delivery platform provides superior versatility and scalability over antibody-based approaches and thus addresses current limitations of dendritic cell-based immunotherapies.

immunology↗

bioRxiv2017

Wall teichoic acid is a pathogen-associated molecular pattern of Staphylococcus aureus that is recognized by langerin (CD207) on skin Langerhans cells

Staphylococcus aureus is a major cause of skin and soft tissue infections and aggravator of the inflammatory skin disease atopic dermatitis (AD). Epicutaneous exposure to S. aureus induces Th17 responses through skin Langerhans cells (LCs), which paradoxically contribute to host defense but also to AD pathogenesis. The underlying molecular mechanisms of the association between S. aureus and skin inflammation are poorly understood. Here, we demonstrate that human LCs directly interact with S. aureus through the pattern-recognition receptor langerin (CD207). Human, but not mouse, langerin interacts with S. aureus through the conserved {beta}-N-acetylglucosamine (GlcNAc) modifications on wall teichoic acid (WTA), thereby discriminating S. aureus from other staphylococcal species. Importantly, the specific S. aureus WTA glycoprofile strongly influences the level of Th1-and Th17-polarizing cytokines that are produced by in vitro generated LCs. Finally, in a murine epicutaneous infection model, S. aureus induced a more pronounced influx of inflammatory cells and pro-inflammatory cytokine transcripts in skin of human langerin transgenic mice compared to wild-type mice. Our findings provide molecular insight into the unique pro-inflammatory capacities of S. aureus in relation to inflammatory skin disease.

microbiology↗