Biology subjects

Schupfer, F.

Publications and source records attributed to Schupfer, F..

5 recordsLinked to original sources

bioRxiv2026

The NimB2 opsonin promotes S. aureus recognition by macrophages in Drosophila melanogaster

Phagocytosis is a conserved effector process of innate immunity that enables specialized immune cells to detect, engulf, and degrade invading microbes as well as dying cells and cellular debris. Soluble opsonins enhance this process by coating target surfaces and promoting their recognition and uptake by phagocytic cells. In Drosophila, many phagocytic receptors of the Nimrod family have been characterized, but opsonins remain comparatively poorly understood. Here, we identified the secreted Nimrod protein NimB2 as an insect opsonin that promotes the clearance of Staphylococcus aureus. NimB2 is produced by the fat body, secreted into the hemolymph, and required for resistance to S. aureus infection. NimB2 null mutants showed reduced phagocytosis of S. aureus while maintaining Toll dependent antimicrobial peptide expression. NimB2 promotes S. aureus binding to plasmatocytes (Drosophila macrophages). Using binding assays and bacterial cell wall mutants, we found that NimB2 recognizes a lipoteichoic acid (LTA) dependent determinant on the S. aureus surface and coats the bacterium. We further show that this coating enables efficient recognition by hemocytes via the phagocytic receptor Eater, which is necessary for NimB2 dependent binding. Moreover, Eater overexpression enhances NimB2 mediated association of S. aureus with hemocytes. Together, our results establish NimB2 as an insect opsonin that links a specific bacterial ligand to a phagocytic receptor.

immunology↗

bioRxiv2025

Reproducibility of Scientific Claims in Drosophila Immunity: A Retrospective Analysis of 400 Publications

Drosophila immunity has been the focus of intense study and has impacted other research fields including innate immunity and agriculturally or epidemiologically relevant investigations of insect pests and vectors. Unsurprisingly for such a large body of work, some published results were later found to be irreplicable. Although some results have been contradicted in the literature, many have no published follow-up, either due to a lack of research or low motivation to publish negative or contradictory results. We have addressed this by performing a reproducibility project that analyses the conceptual replicability of claims from articles published on Drosophila immunity before 2011. To assess replicability, we extracted claims from 400 articles on the Drosophila immune response to bacteria and fungi and performed preliminary verification by comparing these claims to other published literature in the field. Using alternative approaches, we also experimentally tested some unchallenged claims, with no published follow-up. The intent of this analysis was to centralize evidence on insights and findings to improve clarity for scientists that may base research programs on these data. Although the aim of the ReproSci project is to assess the replicability of claims made in articles published in the field of Drosophila immunity, it is in no way an assessment of the scientific value of the research. All our data are published on a publicly available website associated with this article (https://ReproSci.epfl.ch/) that encourages community participation. This article provides a short summary of claims that were found to have contradictory evidence, which may help the community to assess past findings on Drosophila immunity and improve clarity going forward. Statistical analysis of this reproducibility study and metascience insights obtained from this approach are discussed in a companion article.

genetics↗

bioRxiv2025

Layers of immunity: Deconstructing the Drosophila effector response

The host innate immune response relies on the cooperation of multiple defence modules. In insects and other arthropods, which have only innate immune mechanisms, four main immune-specific modules have been described in the defence against microbial invaders: the Toll pathway, the Imd pathway, the melanization response, and phagocytosis by plasmatocytes. Our present understanding of their relative importance remains fragmented as their contribution to host defence has never been simultaneously assessed across a large panel of pathogens. Here, we have taken advantage of newly-described immune mutants in a controlled genetic background to systematically delete these four immune modules individually, in pairs, or even all four simultaneously. Surprisingly, immune deficient flies simultaneously deficient in all four immune modules are viable, homozygous fertile, and display no overt morphological defects, suggesting these immune mechanisms are not strictly required for organismal development. With this new set of lines, we assessed the contribution of each module individually and collectively to host defense against five viruses, three fungi, eight Gram-positive bacteria, and eight Gram-negative bacteria. Our findings show that these four modules largely function independently and additively in host defense, although synergistic effects can occur for select pairs of modules. Our study confirmed the importance of the Imd pathway against Gram-negative bacteria and the Toll pathway against Gram-positive bacteria and fungi, largely via the induction of effectors such as antimicrobial peptides (AMPs) and Bomanins (Bom), but also reveals the important role of melanization against viruses, and the contribution of phagocytosis against various germs. Additionally, by examining microbial load kinetics in different mutants, we provide insight into how these modules contribute to tolerance or resistance against specific microbes. Our study provides insights into the architecture of the Drosophila immune system, revealing differential requirements of immune modules according to each pathogen. The set of immune deficient lines provided here offer tools to better assess the role of these immune modules in host defense.

immunology↗

bioRxiv2024

An updated proteomic analysis of Drosophila hemolymph after bacterial infection

Using an in-depth Mass Spectrometry based proteomics approach, we provide a comprehensivecharacterization of the hemolymphatic proteome of adult flies upon bacterial infection. We detected and quantified changes in abundance of several known immune regulators and effectors, including multiple antimicrobial peptides, peptidoglycan-binding proteins and serine proteases. Comparison to previously published transcriptomic analyses reveals a partial overlap with our dataset, indicating that many proteins released into the hemolymph upon infection may not be regulated at the transcript level. Among them, we identify a set of muscle-derived proteins released into the hemolymph upon infection. Finally, our analysis reveals that infection induces major changes in the abundance of proteins associated with mitochondrial respiration. This study uncovers a large number of previously undescribed proteins potentially involved in the immune response.

immunology↗

bioRxiv2021

Dual proteomics of Drosophila melanogaster hemolymph infected with the heritable endosymbiont Spiroplasma poulsonii

Insects are frequently infected with heritable bacterial endosymbionts. Endosymbionts have a dramatic impact on their host physiology and evolution. Their tissue distribution is variable with some species being housed intracellularly, some extracellularly and some having a mixed lifestyle. The impact of extracellular endosymbionts on the biofluids they colonize (e.g. insect hemolymph) is however difficult to appreciate because biofluids composition can depend on the contribution of numerous tissues. Here we address the question of Drosophila hemolymph proteome response to the infection with the endosymbiont Spiroplasma poulsonii. S. poulsonii inhabits the fly hemolymph and gets vertically transmitted over generations by hijacking the oogenesis in females. Using dual proteomics on infected hemolymph, we uncovered a low level and chronic activation of the Toll immune pathway by S. poulsonii that was previously undetected by transcriptomics-based approaches. Using Drosophila genetics, we also identified candidate proteins putatively involved in controlling S. poulsonii growth. Last, we also provide a deep proteome of S. poulsonii, which, in combination with previously published transcriptomics data, improves our understanding of the post-transcriptional regulations operating in this bacterium. Summary statementWe report the changes in Drosophila melanogaster hemolymph proteome upon infection with the heritable bacterial endosymbiont Spiroplasma poulsonii.

microbiology↗