Biology subjects

Günther, A.

Publications and source records attributed to Günther, A..

10 recordsLinked to original sources

bioRxiv2025

Mass mortality at penguin mega-colonies due to avian cholera confounds H5N1 HPAIV surveillance in Antarctica

In the austral summer 2023/2024, H5N1 high pathogenicity avian influenza virus (HPAIV) was reported for the first time in Antarctica. Concerns of HPAIV causing high mortality of seabirds and mammals prompted immediate efforts to track its spread and impact on endemic wildlife. In March 2024, we visited the Danger Islands archipelago, that hosts two mega-colonies of Adelie penguins, and observed an unusual mortality estimated in thousands of Adelie penguins and other species. Swabs and tissues were collected for molecular detection of infectious agents from 49 carcasses, and additional tissues for histology from a selection of 9 carcasses. We unexpectedly detected Pasteurella multocida DNA in 46 of 49 individuals, and diagnosed avian cholera, and not HPAI, as the cause of death of most of these animals. By metagenomics, we retrieved the genomic sequences of the Pasteurella multocida strain which caused the epizootic, and the phylogenetic analysis showed a close relation with strains previously reported in the Southern Ocean area. This study confirms avian cholera as a relevant cause of mortality in the Antarctic region, and overall highlights the importance of considering avian cholera in the differential diagnoses during mortality events in Antarctica, even with the concurrent circulation of HPAIV.

microbiology↗

bioRxiv2025

Opportunity Drives Spillover: Serological Surveillance across Carnivores, Omnivores and Herbivores in an HPAIV H5 Hotspot in North-East Germany, 2023-2025

In North-East Germanys offshore islands and mainland coast, wild ruminants, boar, and carnivores were tested for H5-HPAI antibodies. Wild ruminants were seronegative; 3.5% of boar and 12.5-21.9% of carnivores were seropositive, evidencing frequent spillover. Because such events may accelerate mammalian--and ultimately human--adaptation, sustained One- Health monitoring is essential. SummaryAcross offshore islands and the mainland coast of North-East Germany, H5 HPAI serosurveillance in wildlife found no seroconversion in ruminants, but positives in 3.5% of boar and 12.5-21.9% of carnivores, indicating ongoing spillover and risk of avian-to- mammalian adaptation.

ecology↗

bioRxiv2025

The expanding avian influenza panzootic: skua die-off in Antarctica

High pathogenicity avian influenza virus of subtype H5 (H5 HPAIV), clade 2.3.4.4b, invaded Antarctica in 2023. Here we show that H5 HPAIV caused high mortality in a breeding colony of skuas at one of ten sites we visited in March 2024. By combined virological and pathological analyses, we found that H5 HPAIV caused multi-organ necrosis and rapid death in skuas. Taken together with recent data, skuas in Antarctica are at risk of continued mortality from H5 HPAIV infection, threatening their already small populations. Conversely, because of their wide distribution and ecological relevance, skuas may play a substantial role in spread of the virus across Antarctica. Transdisciplinary surveillance is needed in coming years to monitor the impact of this poultry-origin disease on Antarcticas unique wildlife.

microbiology↗

bioRxiv2024

Red knots in Europe - a dead end host species or a new niche for highly pathogenic avian influenza?

The 2020/2021 epidemic in Europe of highly pathogenic avian influenza virus (HPAIV) of subtype H5 surpassed all previously recorded European outbreaks in size, genotype constellations and reassortment frequency and continued into 2022 and 2023. The causative 2.3.4.4b viral lineage proved to be highly proficient with respect to reassortment with cocirculating low pathogenic AIV and seems to establish an endemic status in northern Europe. A specific HPAIV reassortant of the subtype H5N3 was detected almost exclusively in red knots (Calidris canutus islandica) in December 2020. It caused systemic and rapidly fatal disease leading to a singular and self-limiting mass mortality affecting about 3.500 birds in the German Wadden Sea, roughly 1% of the entire flyway population of islandica red knots. Phylogenetic analyses revealed that the H5N3 reassortant very likely had formed in red knots and remained confined to this species. While mechanisms of virus circulation in potential reservoir species, dynamics of spill-over and reassortment events and the roles of environmental virus sources remain to be identified, the year-round infection pressure poses severe threats to endangered avian species, and prompts adaptation of habitat and species conservation practices. One-Sentence SummaryHigh red knot mortality in Europe (December 2020) was associated with infection of a unique genotype of HPAIV H5N3 clade 2.3.4.4b.

ecology↗

bioRxiv2023

Pathogen-prey-predator relations of avian raptors during epizootics of highly pathogenic avian influenza virus HPAIV H5N1 (clade 2.3.4.4b) in Germany

Transition of highly pathogenic clade 2.3.4.4b H5 avian influenza virus (HPAIV) from epizootic to enzootic status in Northern European countries was associated with severe losses and even mass mortalities among various wild bird species. Both avian and mammalian raptors hunting infected debilitated birds or scavenging on virus-contaminated avian carcasses contracted HPAIV infection. This precarious pathogen-prey-predator relation further worsened when in 2021 and 2022 outbreaks in Germany overlapped with the hatching season of avian raptor species. Retro- and prospective surveillance revealed avian raptors as important indicators of HPAIV and its genetic diversity on the one hand. On the other hand, their role as victims of HPAIV is stipulated. The first case of an HPAIV H5N1-related death of a white-tailed sea eagle (Haliaeetus albicilla; WTSE) hatch in Germany, 2021, followed by several such cases in 2022, and a low overall seropositivity rate of 5.0-7.9% among WTSE nestlings, raised fears of a serious negative impact on reproduction rates of WTSEs and other birds of prey when HPAIV becomes enzootic in an ecosystem. However, comparably stable breeding success of WTSE in the study area in 2022 and a potentially evolving natural immunity raises hope for a less severe long-term impact. Article impact statementAdapted surveillance measures were developed to assess risks for the conservation of avian raptors due to the panzootic spread of HPAIV.

microbiology↗

bioRxiv2023

Lung injury shifts pulmonary capillary endothelial cells towards regeneration-associated Lrg1+ subpopulations with delayed dynamics in aged mice

Aging increases the risk of developing fibrotic diseases by hampering tissue regeneration after injury. Using longitudinal single-cell RNA-seq and spatial transcriptomics, here we compare the transcriptome of bleomycin-induced fibrotic lungs of young and aged mice, at 3 time points corresponding to the peak of fibrosis, regeneration and resolution. We find that lung injury shifts the transcriptomic profiles of three pulmonary capillary endothelial cells (PCEC) subpopulations. The associated signatures are linked to pro-angiogenic signaling with strong Lrg1 expression and do not progress similarly throughout the resolution process between young and old animals. Moreover, part of this set of resolution-associated markers is also detected in PCEC from samples of patients with idiopathic pulmonary fibrosis. Finally, we find that aging also alters the transcriptome of PCEC which display typical pro-fibrotic and pro-inflammatory features. We propose that age-associated alterations in specific PCEC subpopulations may interfere with the process of lung progenitor differentiation, thus contributing to the persistent fibrotic process typical of human pathology.

pathology↗

bioRxiv2022

Cell-intrinsic ceramides determine T cell function during melanoma progression

Acid sphingomyelinase (Asm) and acid ceramidase (Ac) are parts of the sphingolipid metabolism. Asm hydrolyzes sphingomyelin to ceramide, which is further metabolized to sphingosine by Ac. Ceramide generates ceramide-enriched platforms that are involved in receptor clustering within cellular membranes. However, the impact of cell-intrinsic ceramide on T cell function is not well characterized. By using T cell-specific Asm- or Ac-deficient mice, with reduced or elevated ceramide levels in T cells, we identified ceramide to play a crucial role in T cell function in vitro and in vivo. T cell-specific ablation of Asm in Asmflox/flox/CD4cre mice resulted in enhanced tumor progression associated with impaired T cell responses, whereas Acflox/flox/CD4cre mice showed reduced tumor growth rates and elevated T cell activation compared to the respective controls upon tumor transplantation. Further in vitro analysis revealed that decreased ceramide content supports CD4+ regulatory T cell differentiation and interferes with cytotoxic activity of CD8+ T cells. In contrast, elevated ceramide concentration in CD8+ T cells from Acflox/flox/CD4cre mice was associated with enhanced cytotoxic activity. Strikingly, ceramide co-localized with the T cell receptor (TCR) and CD3 in the membrane of stimulated T cells and phosphorylation of TCR signaling molecules was elevated in Ac-deficient T cells. Hence, our results indicate that modulation of ceramide levels, by interfering with the Asm or Ac activity has an effect on T cell differentiation and function and might therefore represent a novel therapeutic strategy for the treatment of T cell-dependent diseases such as tumorigenesis.

immunology↗

bioRxiv2022

The acid ceramidase/ceramide axis controls parasitemia in Plasmodium yoelii-infected mice by regulating erythropoiesis

Acid ceramidase (Ac) is part of the sphingolipid metabolism and responsible for the degradation of ceramide. As bioactive molecule, ceramide is involved in the regulation of many cellular processes. However, the impact of cell-intrinsic Ac activity and ceramide on the course of Plasmodium infection remains elusive. Here, we use Ac-deficient mice with ubiquitously increased ceramide levels to elucidate the role of endogenous Ac activity in a murine malaria model. Interestingly, ablation of Ac leads to alleviated parasitemia associated with decreased T cell responses in the early phase of Plasmodium yoelii (P. yoelii) infection. Mechanistically, we identified dysregulated erythropoiesis with reduced numbers of reticulocytes, the preferred host cells of P. yoelii, in Ac-deficient mice. Furthermore, we demonstrate that administration of the Ac inhibitor carmofur to wild type mice has similar effects on P. yoelii infection and erythropoiesis. Notably, therapeutic carmofur treatment after manifestation of P. yoelii infection is efficient in reducing parasitemia. Hence, our results provide evidence for the involvement of Ac and ceramide in controlling P. yoelii infection by regulating red blood cell development.

microbiology↗

bioRxiv2020

Mature black alder shows intermittent events of high stem methane emissions

O_LITree stems can be a source of the greenhouse gas methane (CH4). However, assessments of the global importance are complicated by a lack of research and a high variability between ecosystems. Here, we determined the contribution of emissions from tree stems of mature black alder (Alnus glutinosa (L.) Gaertn.) to overall CH4 exchange in two temperate peatlands. C_LIO_LIWe measured emissions from stems and soils using closed chambers in a drained and a wet alder forest over two years. Further, we studied the importance of alder leaves as substrate for methanogenesis in an incubation experiment. C_LIO_LIStem CH4 emissions were shortlived and occurred only during times of inundation at the wet site. The drained site did not show stem emissions and the soil acted as a small CH4 sink. The contribution of stem emissions to the overall CH4 budget was below 0.3% in both sites. C_LIO_LIOur results show that also mature black alders intermittently can be a source of CH4. However, the low share of stem-mediated CH4 emissions in both forests may indicate that this pathway is only of minor relative importance in temperate peatlands. C_LI

ecology↗

bioRxiv2019

Prompt rewetting of drained peatlands reduces climate warming despite methane emissions

Peatlands are strategic areas for climate change mitigation because of their matchless carbon stocks. Drained peatlands release this carbon to the atmosphere as carbon dioxide (CO2). Peatland rewetting effectively stops these CO2 emissions, but also re-establishes the emission of methane (CH4). Essentially, management must choose between CO2 emissions from drained or CH4 emissions from rewetted peatland. This choice must consider radiative effects and atmospheric lifetimes of both gases, with CO2 being a weak but persistent and CH4 a strong but short-lived greenhouse gas. The resulting climatic effects are, thus, strongly time-dependent. We used a radiative forcing model to compare forcing dynamics of global scenarios for future peatland management using areal data from the Global Peatland Database. Our results show that CH4 radiative forcing does not undermine the climate change mitigation potential of peatland rewetting. Instead, postponing rewetting increases the long-term warming effect of continued CO2 emissions. Warnings against CH4 emissions from rewetted peatlands are therefore unjustified and counterproductive.

ecology↗