Biology subjects

Zeelen, J. P.

Publications and source records attributed to Zeelen, J. P..

4 recordsLinked to original sources

bioRxiv2025

Targets of the human antibody response to the variant surface glycoprotein of Trypanosoma brucei

Human African Trypanosomiasis (HAT) is a severe disease endemic to Sub-Saharan Africa caused by the parasite Trypanosoma brucei. Diagnosis of the chronic form of HAT relies heavily on serological screening tests that detect specific antibodies. Trypanosoma brucei parasites rely on the antigenic variation of their variant surface glycoproteins (VSG) to evade host antibody recognition. Although VSG is the primary target of host antibodies, studies of the antibody response to VSG have been limited by low-throughput approaches that allow for the analysis of only a few VSG proteins at a time, primarily in animal models. Here, we use phage immunoprecipitation sequencing (PhIP-seq) to characterize the antibody response to VSG in HAT patient serum. Using a comprehensive T7 bacteriophage display library containing peptides representing 12,108 unique T. brucei VSGs, our analysis revealed significant differences in the anti-VSG antibody between the acute and chronic forms of HAT. Our results show that, in chronic HAT, the top lobe of the VSG is the primary interface of antibody interactions. By characterizing the targets of anti-VSG immunity, we also identified a potential bias in the CATT, the most common test used for HAT screening. Finally, we were able to identify sets of seroprevalent VSG peptides for each form of the disease that successfully distinguish between infected and uninfected individuals. Our results demonstrate the utility of characterizing host antibody responses against African trypanosomes, which can reveal unique features of parasite biology while also uncovering new diagnostic targets.

microbiology↗

bioRxiv2025

Chromosome segregation in Escherichia coli involves DNA binding by the MinC-MinD complex

The Escherichia coli Min system, composed of the proteins MinC, MinD, and MinE, is crucial for directing septum formation at mid-cell. MinD has also been shown to bind DNA in a non-sequence-specific manner and to tether plasmid DNA to liposomes. A role for the Min system in chromosome segregation has been proposed, whereby repeated, transient membrane-tethering events mediated by MinD could help prevent backward movements of the duplicated chromosomes once entropic forces weaken. However, the contribution of the other Min proteins to DNA binding has remained unclear. Here, we demonstrate that DNA binding is strongly enhanced when MinD and MinC form a complex, while MinE and FtsZ (at high concentrations) interfere with this binding. We reveal a critical role for the linker connecting MinCs N- and C-terminal domains in both DNA binding and inhibition of FtsZ polymerization. E. coli strains expressing MinC linker variants from the native locus, in combination with the alpha subunit of HU tagged with GFP, display chromosomes that appear more spread throughout the cell. This phenotype could reflect reduced compaction, chromosome segregation defects, or a combination of both. These findings suggest a previously unrecognized role for the MinC linker in DNA binding and provide new insights into a potential physiological role of MinCD-DNA bnding in chromosome organization and/or dynamics.

microbiology↗

bioRxiv2023

A Structural Classification of the Variant Surface Glycoproteins of the African Trypanosome

Long-term immune evasion by the African trypanosome is achieved through repetitive cycles of surface protein replacement with antigenically distinct versions of the dense Variant Surface Glycoprotein (VSG) coat. Thousands of VSG genes and pseudo-genes exist in the parasite genome that, together with genetic recombination mechanisms, allow for essentially unlimited immune escape from the hosts adaptive immune system. The diversity space of the "VSGnome" at the protein level was thought to be limited to a few related folds whose structures were determined more than 30 years ago. However, recent progress has shown that the VSGs possess significantly more architectural variation than had been appreciated. Here we combine experimental X-ray crystallography with deep-learning structural prediction using Alphafold to produce models of hundreds of VSG proteins. We classify the VSGnome into groups based on protein architecture and oligomerization state, contextualize recent bioinformatics clustering schemes, and extensively map VSG-diversity space. We demonstrate that in addition to the structural variability and post-translational modifications observed thus far, VSGs are also characterized by variations in oligomerization state and possess inherent flexibility and alternative conformations, lending additional variability to what is exposed to the immune system. Finally, these additional experimental structures and the hundreds of Alphafold predictions confirm that the molecular surfaces of the VSGs remain distinct from variant to variant, supporting the hypothesis that protein surface diversity is central to the process of antigenic variation used by this organism during infection.

microbiology↗

bioRxiv2021

Nanobody Mediated Macromolecular Crowding Induces Membrane Fission and Remodeling in the African Trypanosome

The dense Variant Surface Glycoprotein (VSG) coat of African trypanosomes represents the primary host-pathogen interface. Antigenic variation prevents clearing of the pathogen by employing a large repertoire of antigenically distinct VSG genes, thus neutralizing the hosts antibody response. To explore the epitope space of VSGs, we generated anti-VSG nanobodies and combined high-resolution structural analysis of VSG-nanobody complexes with binding assays on living cells, revealing that these camelid antibodies bind deeply inside the coat. One nanobody caused rapid loss of cellular motility, possibly due to blockage of VSG mobility on the coat, whose rapid endo-and exocytosis is mechanistically linked to T. brucei propulsion and whose density is required for survival. Electron microscopy studies demonstrated that this loss of motility was accompanied by rapid formation and shedding of nanovesicles and nanotubes, suggesting that increased protein crowding on the dense membrane can be a driving force for membrane fission in living cells.

microbiology↗