Biology subjects

Schramm, G.

Publications and source records attributed to Schramm, G..

3 recordsLinked to original sources

bioRxiv2025

Schistosoma mansoni-induced host immunopathology is gut microbiota dependent

Despite progress in schistosomiasis control during recent decades in endemic areas, this parasitic blood-fluke infection continues to pose a substantial public health burden. In depth understanding of the mechanisms behind the complex immunopathology and drivers of morbidity in schistosomiasis is urgently needed. Chronic infection with the parasitic blood fluke Schistosoma mansoni manifests the most severe pathology in relation to egg-induced host immune responses and fibrosis development. Host immune homeostasis is influenced by the commensal gut microbiota, which may therefore also affect systemic immunopathology induced by S. mansoni. Both humans and experimental animal models show metabolomic changes related to gut microbial and liver metabolism during S. mansoni infection, further supporting a link between gut microbiota and regulation of S. mansoni pathology. To investigate whether a radically changed gut microbiota composition would result in changed S. mansoni egg-induced pathology, a mouse model combining antibiotic treatment and infection was established. In the model, the commensal gut microbial composition of female C57BL/6-NTac mice was altered by oral administration of a broad-spectrum ampicillin-vancomycin cocktail prior to infection with S. mansoni and throughout the experiment. An ecosystem view of the host immune milieu was collated by measuring a wide range of parameters: gut microbiome characterisation, immune profiling on the transcriptional level (ileum and liver) supported by flow cytometry of cells (spleen and mesenteric lymph nodes) and bead-based measurements of immune parameters in sera, short-chain fatty acid measurements in sera and caecal content, intestinal permeability assessment, liver enzyme levels in sera, and histology and stereology to characterise immunopathology (ileum and liver). The application of stereological principles to address the non-spherical nature of egg-induced liver granulomas and ileum inflammation supported by liver enzyme levels, collagen deposition, and immune parameters, enabled demonstration of significantly less granuloma formation in livers from antibiotics treated mice compared to controls. The observed difference in the degree of egg-induced inflammatory response in livers from infected mice mediated by antibiotics treatment, was not observed in ileum tissue and could not be explained by infection burden. Our mouse model results demonstrate a role for the gut microbiota and intestinal immune milieu in regulation of systemic S. mansoni infection-driven liver pathology and, hence, potential morbidity. In translational context, these findings warrant that drivers of gut microbial changes and intestinal immune milieu must be considered when pursuing novel holistic interventions for treatment or alleviation of persistent schistosomiasis.

immunology↗

bioRxiv2020

Tumor Necrosis Factor and Schistosoma mansoni egg antigen Omega-1 shape distinct aspects of the early egg-induced granulomatous response

Infections by schistosomes result in granulomatous lesions around parasite eggs entrapped within the host tissues. The host and parasite determinants of the Schistosoma mansoni egg-induced granulomatous response are areas of active investigation. Some studies in mice implicate Tumor Necrosis Factor (TNF) produced in response to the infection whereas others fail to find a role for it. In addition, in the mouse model, the S. mansoni secreted egg antigen omega-1 is found to induce granulomas but the underlying mechanism remains unknown. We have recently developed the zebrafish larva as a model to study macrophage recruitment and granuloma formation in response to Schistosoma mansoni eggs. Here we use this model to investigate the mechanisms by which TNF and omega-1 shape the early granulomatous response. We find that TNF, specifically signaling through TNF receptor 1, is not required for macrophage recruitment to the egg and granuloma initiation but does mediate granuloma enlargement. In contrast, omega-1 mediates initial macrophage recruitment, with this chemotactic activity being dependent on its RNase activity. Our findings further the understanding of the role of these host- and parasite-derived factors and show that they impact distinct facets of the granulomatous response to the schistosome egg.

microbiology↗

bioRxiv2020

STAT2 signaling as double-edged sword restricting viral dissemination but driving severe pneumonia in SARS-CoV-2 infected hamsters

Introductory paragraphSince the emergence of SARS-CoV-2 causing COVID-19, the world is being shaken to its core with numerous hospitalizations and hundreds of thousands of deaths. In search for key targets of effective therapeutics, robust animal models mimicking COVID-19 in humans are urgently needed. Here, we show that productive SARS-CoV-2 infection in the lungs of mice is limited and restricted by early type I interferon responses. In contrast, we show that Syrian hamsters are highly permissive to SARS- CoV-2 and develop bronchopneumonia and a strong inflammatory response in the lungs with neutrophil infiltration and edema. Moreover, we identify an exuberant innate immune response as a key player in pathogenesis, in which STAT2 signaling plays a dual role, driving severe lung injury on the one hand, yet restricting systemic virus dissemination on the other. Finally, we assess SARS-CoV- 2-induced lung pathology in hamsters by micro-CT alike used in clinical practice. Our results reveal the importance of STAT2-dependent interferon responses in the pathogenesis and virus control during SARS-CoV-2 infection and may help rationalizing new strategies for the treatment of COVID-19 patients.

microbiology↗