Biology subjects

Holtfreter, S.

Publications and source records attributed to Holtfreter, S..

6 recordsLinked to original sources

bioRxiv2026

A mouse-adapted Staphylococcus aureus strain enables lifelong neonatal colonization and elicits a Th17-dominated immune response

The opportunistic pathogen Staphylococcus aureus persistently colonizes the anterior nares of up to 20% of the human population, yet there were no persistent mouse colonization models to study host-pathogen interaction. Using the mouse-adapted S. aureus strain JSNZ (CC88-MSSA), we established a neonatal S. aureus colonization model in C57BL/6N mice. Natural neonatal colonization was achieved by vertical transmission in a JSNZ-positive breeding colony. Offspring were followed for up to 69 weeks and found persistently colonized in the nose and cecum with high bacterial loads. Adult mice were colonized by intranasal inoculation of JSNZ; controls received PBS. The colonization patterns and the S. aureus-specific T cell responses were then monitored over a period of 28 days and compared between age-matched mice colonized as neonates or adults. The neonatal group remained persistently colonized in nose and gut with high bacterial densities. In contrast, mice colonized as adults had lower and declining bacterial loads in the nose. Some eliminated S. aureus from the nares, while all remained colonized in the gut. Neonatally colonized mice exhibited reduced nasal chemokine levels, which may have favored the prolonged S. aureus persistence. Ex vivo re-stimulation of cervical lymph node cells with an S. aureus antigen cocktail revealed a Th17-dominated antigen-specific T cell response in both colonized groups. The lymph node cells secreted large amounts of IL-17, but Th1-, Th2-associated and regulatory cytokines were also detected. The cytokine patterns were similar in both colonized groups except for IL-5, which was more abundant upon neonatal colonization. In conclusion, vertical transmission of the mouse-adapted S. aureus strain JSNZ reliably establishes persistent high-density neonatal colonization, providing a physiologically relevant model for the study of S. aureus host interactions. Route and timing of colonization do not fundamentally affect the T cell response to S. aureus.

immunology↗

bioRxiv2025

Immunoglobulin sub-class levels define inter-donor plasma variability: a longitudinal dual-lab study

Advancements in mass spectrometry have transformed plasma proteomics, allowing for high-throughput analysis of large cohorts. This study utilized the TIMES cohort, consisting of 51 healthy participants monitored monthly over 12 months, to evaluate intra- and inter-individual variability in the plasma proteome. Approximately 600 samples were analyzed in two independent laboratories, revealing strong correlations despite methodological differences. The study focused on the stability of the plasma proteome within donors over a year, with larger differences observed between donors. A support vector machine model achieved a 98% median classification accuracy, confirming stable, donor-specific proteomic profiles. Immunoglobulins, often overlooked in plasma proteomics, were found to contribute significantly to donor-specific signatures, showing pronounced inter-individual variability but remarkable intra-donor stability. In contrast, C-reactive protein and other inflammation markers exhibited significant temporal fluctuations and donor-specific baseline levels. This inter-laboratory study highlights the importance of longitudinal sampling for biomarker discovery, the robustness of MS-based proteomic workflows, and provides new insights into immunoglobulin dynamics and variability in human plasma. Synopsis O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=65 SRC="FIGDIR/small/686385v1_ufig1.gif" ALT="Figure 1"> View larger version (19K): org.highwire.dtl.DTLVardef@1e7b501org.highwire.dtl.DTLVardef@11c85d7org.highwire.dtl.DTLVardef@1971a1dorg.highwire.dtl.DTLVardef@1338061_HPS_FORMAT_FIGEXP M_FIG C_FIG O_LILongitudinal analysis of individual plasma proteomes over a one-year period revealed low intra-individual variability albeit high inter-individual differences. C_LIO_LICross-site laboratory comparisons confirmed strong concordance in analytical performance and measurement consistency. C_LIO_LIConversion of relative protein intensities to absolute concentrations revealed immunoglobulin levels on par with established clinical reference ranges. C_LIO_LIDonors were distinguishable based on their unique plasma proteome. C_LIO_LIThe immunoglobulin sub-classes are key discriminators defining inter- and intra-donor variability C_LI

molecular biology↗

bioRxiv2025

E3 ubiquitin ligase SKP2 limits autophagy during S. aureus infection

Ubiquitination is a posttranslational modification that affects protein function, stability, and localization and is thereby balancing protein homeostasis. During infection, ubiquitination is crucial in regulating host cell signaling pathways in pathogen recognition, clearance and mounting an efficient immune response. S. aureus is an opportunistic pathogen that is able to invade and multiply within both phagocytic and non-phagocytic mammalian cells depending on virulence factor expression of the respective S. aureus strain. Selective autophagy serves as a host defense mechanism to combat intracellular bacterial persistence by targeting and degrading intracellular pathogens. However, S. aureus can subvert autophagosomal degradation and exploit these organelles for intracellular replication. We examined the role of the E3 ligase S-phase kinase-associated protein 2 (SKP2), a component of the SKP1-Cullin1-F-box (SCF) - complex, during S. aureus infection in alveolar epithelial and in macrophage-like cells. Upon S. aureus infection, we demonstrate increased SKP2 abundance through acetylation-induced stabilization and translocation into the cytoplasm. Cytoplasmic SKP2 modulated autophagy induction. By downregulation of SKP2, the level of the autophagy marker LC3-II was elevated which was accompanied by increased survival of intracellular S. aureus. Conversely, SKP2 overexpression in host cells reduced LC3-II levels followed by reduced intracellular bacteria. These findings underscore that SKP2 is an important regulator of autophagy, preventing excessive autophagy from being exploited by S. aureus. In conclusion, our findings reveal novel molecular mechanisms involved in the interaction between host cells and S. aureus providing potential approaches for targeted therapeutic intervention. ImportanceStaphylococcus aureus is a major pathogen responsible for a wide range of human and animal infections and toxin-mediated syndromes. For many years, S. aureus was mainly recognized as an extracellular pathogen. However, it has been shown that S. aureus can survive in epithelial cells and phagocytes. Intracellular persistence complicates the treatment by protecting the bacteria from antibiotics and immune detection. Elimination of pathogens from intracellular compartments relies on cellular mechanisms such as recognition and ubiquitination by host E3 ligases followed by selective autophagy. S. aureus has developed strategies to manipulate this process by evading degradation by interfering with autophagosome formation or even exploiting the formation of autophagosomes as replication niches. The present study reveals an intricate cellular response pathway that is involved in the intracellular recognition and elimination of the pathogen. This knowledge opens new avenues towards targeted treatment.

microbiology↗

bioRxiv2025

Spontaneous preputial gland adenitis in Staphylococcus aureus-colonized male C57Bl/6 mice triggers a Th17-driven immune response

Colonization with the pathobiont Staphylococcus aureus increases the risk of endogenous S. aureus infections if the balance between host and microbe is disturbed. We developed a model of persistent S. aureus colonization using the mouse-adapted strain JSNZ. The bacteria transfer from parents to offspring, producing lifelong, usually asymptomatic colonization. Here we report that S. aureus-colonized adult male mice frequently develop spontaneous preputial gland infections (preputial gland adenitis, PGA), which are characterized by pronounced pus production and gland enlargement. This study aimed to characterize PGA in terms of phenotype, causative agents, and the pathogen-specific antibody and T cell responses. We compared three groups: naive mice, colonized PGA-negative mice, and colonized PGA-positive mice. PGA occurred in 8/12 (67%) of male breeding animals and in 17/25 (68%) of adult male offspring. The infection did not self-resolve and persisted for several months. Genotyping identified the colonizing strain JSNZ as the causative agent. The infection caused purulent inflammation, with massive bacterial aggregates and neutrophil infiltrates filling the gland lumen. This inflammation completely disrupted the glandular architecture. PGA induced a strong but localized release of IL-1, IL-1{beta}, IL-17, MIP-1, and KC in the infected gland. T cells from PGA-draining lymph nodes, as well as splenocytes, reacted to in vitro re-stimulation with a S. aureus antigen cocktail with the proliferation of Th17 cells, and the release of IL-17 and IFN-{gamma}, corresponding to a type 3/1- immune response. Colonized PGA-positive mice also mounted a robust S. aureus-specific serum antibody response. In conclusion, the pathology of this spontaneous, chronic S. aureus infection is driven by a strong, type 3-biased immune response that, however, fails to clear the bacteria. This endogenous PGA model provides a valuable tool for studying host-pathogen interactions in natural S. aureus infection.

microbiology↗

bioRxiv2025

Integrated genomic and proteomic analysis of the mouse-adapted Staphylococcus aureus strain JSNZ

Mouse-adapted Staphylococcus aureus strains have become increasingly relevant in infection research thanks to their ability to better recapitulate clinical infection dynamics in mouse models. However, detailed characterisations required to establish a corresponding reference strain are still lacking. The mouse-adapted CC88 strain JSNZ appears to be an ideal candidate for a reference strain, because CC88 is widespread among laboratory mice and frequently employed in mouse colonisation and infection models. Moreover, JSNZ demonstrates high genetic transformability comparable to that of commonly used laboratory strains. Here, we present a comprehensive genomic and proteomic characterisation of JSNZ. Whole genome sequencing was performed using a combination of short and long reads. Proteomic profiling was conducted under standard laboratory conditions in TSB and RPMI during exponential and stationary growth using LC-MS/MS. The updated, closed genome sequence of JSNZ was integrated into AureoWiki for user-friendly access and direct comparison to long-established reference strains. Genome data revealed a deletion in the restriction endonuclease gene hsdR, likely explaining the observed efficient transformation while retaining DNA modification capabilities. This positions JSNZ as a hub for genetic modification of other CC88 isolates. Proteomic profiling of JSNZ indicated broad similarity to common S. aureus reference strains. However, a striking exception was the novel serine protease Jep, which constituted approximately 75% of the exoproteome in stationary TSB cultures. Overall, these findings affirm JSNZ as a robust and genetically tractable model strain for murine S. aureus infection research and contribute a valuable standardised resource to enhance experimental reproducibility and cross-study consistency in the field. Graphical abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=119 SRC="FIGDIR/small/674026v1_ufig1.gif" ALT="Figure 1"> View larger version (42K): org.highwire.dtl.DTLVardef@130b864org.highwire.dtl.DTLVardef@199b1f2org.highwire.dtl.DTLVardef@171b6e0org.highwire.dtl.DTLVardef@9d371f_HPS_FORMAT_FIGEXP M_FIG C_FIG

microbiology↗

bioRxiv2017

Natural Colonization of Laboratory Mice with Staphylococcus aureus Primes a Systemic Immune Response

BackgroundWhether mice are an appropriate model for S. aureus infection and vaccination studies is a matter of debate, because they are not considered as natural hosts of S. aureus. Sparked by an outbreak of S. aureus infections in laboratory mice, we investigated whether laboratory mice are commonly colonized with S. aureus and whether this might impact on infection experiments.\n\nMethodsWe characterized 99 S. aureus isolates from laboratory mice (spa typing, virulence gene PCR), and quantified murine antibodies using FlexMap technology.\n\nResultsSpecific-pathogen-free mice from various vendors were frequently colonized with S. aureus (0-21%). S. aureus was readily transmitted from murine parents to offspring, which became persistently colonized. Most murine isolates belonged to the lineage CC88 (54%). Murine strains showed features of host adaptation, such as absence of hlb-converting phages and superantigen genes, as well as enhanced coagulation of murine plasma. Importantly, S. aureus colonization induced a systemic IgG response specific for numerous S. aureus proteins, including several vaccine candidates.\n\nConclusionLaboratory mice are natural hosts of S. aureus and, therefore, provide better infection models than previously assumed. Pre-exposure to S. aureus is a possible confounder in S. aureus infection and vaccination studies.

immunology↗