Four large dams were removed from the Klamath River in Oregon and California, USA in 2023-24. This was the largest dam removal and restoration project in U.S. history, with a primary aim to restore critical habitat for threatened and endangered salmon populations that the dams had constrained to the lower half of the river basin for over a century. The dam removals resulted in profound physical changes to the river that are expected to alter host-pathogen dynamics in significant ways. Reconnecting the lower and upper portions of the river basin has increased habitat available to salmon, and adult salmon have already begun to return to streams upstream from the former dams where they were historically present. These fish now have longer migration routes, altering the distribution and abundance of both hosts and pathogens. To develop a management plan for the reconnected river, our workgroup drew from a combination of Western Science and Traditional Ecological Knowledge to inform disease risk predictions. While our initial synthesis included multiple pathogens for which there was evidence of disease related impacts, in this forum we focus on Ceratonova shasta, which is considered the primary pathogen limiting salmon recovery in this river system. For juvenile salmon, we predict a reduction in disease risk resulting from the decrease in overlap between infected salmonid and annelid hosts, attributable to the restoration habitats that favor salmonids but are less suitable for annelids. habitats, we predict increased risk of infection and disease resulting from associated with prespawn mortality, previously not observed in salmon in this cycle.

Environmental change can impact host-parasite interactions, but the effects of multiple stressors on parasites are rarely measured. Considering stressor interactions may allow parasitologists to evaluate how parasite burdens change in nature, where stressors rarely occur in isolation. This study aimed to understand how combined stressors such as warming, nutrients and pollution (i.e. metal concentrations) influence myxozoan prevalence and abundance in the Pearl River, Louisiana, USA. Fish were seined between 1963 and 2005 upstream and downstream of a pulp-mill outfall and were then preserved and accessioned into the Royal D. Suttkus Fish Collection of the Tulane University Biodiversity Research Institute. In 2024, we dissected 1188 fish individuals across 7 host species, and we identified myxozoans in 6 species. Six myxozoan genera were detected, including Chloromyxum, Henneguya, Myxidium, Myxobolus, Thelohanellus and Unicauda, with some novel host-parasite combinations. The abundance of Myxobolus infecting Carpiodes velifer gills declined by 86% over the study period, while the abundance of Myxobolus infecting Pimephales vigilax gills was significantly lower downstream of the pulp mill outfall. Among the drivers analyzed, temperature had a significant negative effect on this parasite's abundance, metal concentrations had a positive effect, and these 2 drivers interacted. Our results highlight the differential susceptibility of wild fishes to myxozoan infections and the usefulness of museum collections for understanding historical change in myxozoan burdens in fish. Since stressor-driven changes in myxozoan abundance do not follow a single pattern across species, we expect a shift in freshwater myxozoan communities with progressing climate change and pollution.

Background & Aims: Alcohol-associated liver disease (ALD) is a major cause of liver disease worldwide with scarce therapeutic options. Animal models poorly recapitulate advanced ALD precluding the development of new treatments. Organoids have emerged as a powerful human-based preclinical tool. However, current patient-derived liver organoids fail to recapitulate the epithelial heterogeneity and its generation requires liver surgical resections, thus limiting personalized disease modeling. Here, we report the development of organoids from liver needle biopsies (b-Orgs) from patients with ALD. Methods: b-Orgs were generated from tru-cut biopsies from patients at early (n=28) and advanced (n=34) stages of ALD. b-Orgs were characterized by immunofluorescence, bulk and single cell RNA-sequencing and compared to parental tissues. b-Orgs were used to model ALD progression, identify pathogenic drivers, induce alcohol-associated hepatitis (AH) and evaluate response to prednisolone. Results: Phenotypic and functional analysis of b-Orgs showed hepatocyte-enriched features. Single-cell RNA-sequencing revealed a heterogeneous cell composition comprising hepatocyte, biliary and progenitor populations, mirroring the epithelial landscape found in patients with advanced ALD. Moreover, b-Orgs preserved disease-stage features and allowed to identify the association of ELF3 with cell plasticity and disease progression. Finally, stimulation of b-Orgs with drivers of ALD induced pathophysiological features of alcohol-associated hepatitis, including ROS production, lipid accumulation, inflammation and decreased cell proliferation, which were mitigated in response to prednisolone. Conclusions: Overall, we provide a human-based model that recapitulates epithelial complexity and patient specific features, allowing to identify drivers of cell plasticity and expanding organoid-based liver disease modeling for personalized medicine. ### Competing Interest Statement The authors have declared no competing interest.

Ceratomyxosis due to the myxozoan parasite Ceratonova shasta affects salmonids, causing severe enteritis leading to hemorrhaging and necrosis. The waterborne parasite stages penetrate host gills and reach the fish intestine through the bloodstream. Steelhead trout (Oncorhynchus mykiss) populations from C. shasta endemic watersheds (sympatric) are less susceptible than populations from non-endemic watersheds (allopatric). We investigated the immune effectors behind these different susceptibilities. Both steelhead trout strains were exposed to C. shasta genotype 0. Intestinal tissue and serum samples of control and exposed sympatric and allopatric fish were taken at 8, 15, 22, 29, 57, and 183 days post exposure. Gills were taken at 1 and 8 days post exposure. Parasite abundance and histopathology were evaluated on tissue sections of fish that tested PCR+ for the parasite. Zap70+ T cells, IgT+ B cells, and IgD+ B cells were quantified, and the presence of specific IgM was evaluated from fish sera by immunohistochemistry. Parasite counts were significantly lower and limited to a shorter duration in sympatric fish. The initial intestinal inflammatory response in both fish strains was characterized by hyperplasia of the lamina propria-submucosa and epithelial infiltration of lymphocytes. Remarkably, hyperplasia was resolved earlier in sympatric fish, whereas in allopatric fish, hyperplasia was not resolved by the end of the experiment, coinciding with high intestinal parasite counts and sporogenesis. An increase of intestinal Zap70+ T cells occurred before IgT+ B cells peaked, earlier in sympatric than in allopatric fish. Low numbers of intestinal IgD+ B cells were detected in both strains. In gills, an early increase of Zap70+ T cells was observed in both fish strains at 1 day post exposure, and an increase of IgD+ B cells occurred only in the allopatric strain. Specific circulating IgM was detected much later in both fish strains, only at 57 and 183 days post exposure. In conclusion, sympatric steelhead trout restricted intestinal proliferation of C. shasta genotype 0 more effectively than allopatric fish, probably due to an earlier T cell response triggering a stronger IgT-based mucosal adaptive response in the intestine. Specific circulating IgM appeared later in both sympatric and allopatric fish, probably also contributing systemic protection.

Human-driven Arctic warming and resulting sea ice loss have been associated with declines in several polar bear populations. However, quantifying how individual responses to environmental change integrate and scale to influence population dynamics in polar bears has yet to be achieved. We developed an individual-based bioenergetic model and hindcast population dynamics across 42 years of observed sea ice conditions in Western Hudson Bay, a region undergoing rapid environmental change. The model successfully captured trends in individual morphometrics, reproduction, and population abundance observed over four decades of empirical monitoring data. Our study provides evidence for the interplay between individual energetics and environmental constraints in shaping population dynamics and for the fundamental role of a single limiting mechanism-energy-underpinning the decline of an apex Arctic predator.

BACKGROUND & AIMS:Animal models poorly recapitulate advanced alcohol-associated liver disease (ALD), precluding the development of new treatments. Organoids have emerged as a powerful human-based preclinical tool; however, current patient-derived liver organoids fail to capture epithelial heterogeneity and require surgical resections, limiting their use in personalized disease modeling. Here, we describe the development of organoids from liver needle biopsies (b-Orgs) obtained from patients with ALD. METHODS:b-Orgs were generated from tru-cut biopsies from patients at early (n = 28) and advanced (n = 34) stages of ALD. b-Orgs were characterized by immunofluorescence, bulk and single-cell RNA sequencing, and compared to parental tissues. b-Orgs were used to model ALD progression, identify pathogenic drivers, induce alcohol-associated hepatitis and evaluate response to prednisolone. RESULTS:Phenotypic and functional analysis of b-Orgs showed hepatocyte-enriched features. Single-cell RNA sequencing revealed a heterogeneous cell composition comprising hepatocyte, biliary and progenitor populations, mirroring the epithelial landscape found in patients with advanced ALD. Importantly, b-Orgs preserved disease stage features and revealed an association between ELF3, cell plasticity, and disease progression. Finally, stimulation of b-Orgs with drivers of ALD induced pathophysiological features of alcohol-associated hepatitis, including reactive oxygen species production, lipid accumulation, inflammation and decreased cell proliferation, which were attenuated by prednisolone. CONCLUSIONS:We describe a human-based model that captures epithelial complexity and patient-specific features of ALD. This approach enables the identification of drivers of cell plasticity and highlights the potential of organoid-based liver disease modeling for personalized medicine. IMPACT AND IMPLICATIONS:While organoids have emerged as a powerful human-based preclinical tool, current patient-derived liver organoids fail to capture epithelial heterogeneity and require surgical resections, limiting their use in personalized disease modeling. Here, we describe the generation of biopsy-derived organoids (b-Orgs) from patients with varying stages of alcohol-related liver disease. b-Orgs capture the liver epithelial cell composition found in patients' liver tissue and are efficiently generated from different stages of the disease, providing a platform for patient-tailored disease modeling and drug testing.

BACKGROUND AND AIMS: Short-term mortality in alcohol-related hepatitis (AH) is high, and no current therapy results in durable benefit. A role for interleukin (IL)-1(3 has been demonstrated in the pathogenesis of alcohol-induced steatohepatitis. This study explored the safety and efficacy of canakinumab (CAN), a monoclonal antibody targeting IL-1(3, in the treatment of patients with AH. METHODS: Participants with biopsy-confirmed AH and discriminant function >= 32 but Model for End-Stage Liver Disease <= 27 were randomly allocated 1:1 to receive either CAN 3 mg/kg or placebo (PBO). Liver biopsies were taken before and 28 days after treatment. The primary endpoint was the overall histological improvement in inflammation analyzed by the modified intention-to-treat principle. RESULTS: Fifty-seven participants were randomized: 29 to CAN and 28 to PBO. Two participants had histology that did not corroborate the clinical diagnosis. Of the remaining 55 participants, paired histology data were evaluable from 48 participants. In CAN-treated participants, 14 (58%) of 24 demonstrated histological improvement compared with 10 (42%) of 24 in the PBO group (P = .25). There was no improvement in prognostic scores of liver function. Four (7%) of the 55 participants died within 90 days, 2 in each group. The number of serious adverse events was similar between CAN vs PBO. In post hoc exploratory analyses after adjustment for baseline prognostic factors, CAN therapy was associated with overall histological improvement (P = .04). CONCLUSIONS: CAN therapy in severe AH participants with Model for End-Stage Liver Disease <= 27 did not alter biochemical or clinical outcomes compared with PBO. Nonsignificant histological improvements did not translate into clinical benefit. EudraCT, Number: 2017-003724-79; ClinicalTrials.gov, Number: NCT03775109.

Background & Aims: Severe alcohol-related hepatitis (sAH) is an inflammatory condition with high short-term mortality. Hypothesis-driven approaches have failed to identify effective treatments. Given the role of lipids as inflammatory mediators, this study aimed to identify lipidomic changes and lipid species associated with sAH and mortality risk. Methods: Untargeted lipidomics was performed on serum samples from two cohorts of patients with sAH and decompensated cirrhosis (DC). Principal component analysis and orthogonal partial least squares discriminant analysis were used to assess lipidome changes. Correlations were made with lipoproteins, lipid mediators, cytokines, cytokeratin fragments, and histological indices. Results: In the first part, 78 patients with sAH were matched on bilirubin levels with 23 patients with DC. Lipidomics identified a distinct sAH signature involving glycerophospholipids, including PC(34:2) (odds ratio [OR] 2.18, 95% confidence interval [CI] 1.45–7.05, p = 0.01), PC(O–38:5) (OR 3.31, 95% CI 2.23–7.14, p = 0.002), PI(38:4) (OR 0.71, 95% CI 0.46–0.88, p = 0.02), and LPC(18:1) (OR 0.47, 95% CI 0.32–0.82, p = 0.01). These lipids demonstrated excellent discriminatory power between sAH and DC with areas under the receiver operating characteristic curve (AUROCs) between 0.87 and 0.88. In the second part, in 159 sAH patients, specific lipids, including carnitines CAR(2:0) (OR 2.51, 95% CI 1.25–4.96, p = 0.008) and CAR(16:1) (OR 2.21, 95% CI 1.09–7.48, p = 0.009), were linked to 90-day mortality. Acylcarnitines correlated with disease severity parameters such as model for end-stage liver disease, pro-inflammatory cytokines levels, and hepatocyte ballooning on pathology. Conclusions: Untargeted lipidomics identified a glycerophospholipid and sphingolipid signature distinguishing sAH from DC, implicating lipid species involved in liver regeneration and immune function. Acylcarnitine accumulation in patients with sAH and poor prognosis suggests mitochondrial dysfunction and warrants further investigation into therapeutic potential. Impact and implications: Lipids can act as mediators at the interface between the immune system and metabolism, potentially contributing to the pathogenesis and outcomes of patients with severe alcohol-related hepatitis, prompting us to investigate lipidomic changes in this population using untargeted approaches, compared with patients with decompensated cirrhosis. This study highlights a distinct lipidomic signature in patients with severe alcohol-related hepatitis compared with decompensated cirrhosis, primarily involving glycerophospholipids and sphingolipids. Specific lipid classes, such as acylcarnitines, suggest significant mitochondrial dysfunction and are associated with disease severity and short-term mortality in patients with severe alcohol-related hepatitis. These findings underscore the importance of targeted investigations into these lipid species, their pathways, and their links to disease severity and outcomes, particularly in this condition that currently lacks specific treatments.

BACKGROUND:Polygenic Risk Scores (PRS) based on results from genome-wide association studies offer the prospect of risk stratification for many common and complex diseases. We developed a PRS for alcohol-associated cirrhosis by comparing single-nucleotide polymorphisms among patients with alcohol-associated cirrhosis (ALC) versus drinkers who did not have evidence of liver fibrosis/cirrhosis. METHODS:Using a data-driven approach, a PRS for ALC was generated using a meta-genome-wide association study of ALC (N=4305) and an independent cohort of heavy drinkers with ALC and without significant liver disease (N=3037). It was validated in 2 additional independent cohorts from the UK Biobank with diagnosed ALC (N=467) and high-risk drinking controls (N=8981) and participants in the Indiana Biobank Liver cohort with alcohol-associated liver disease (N=121) and controls without liver disease (N=3239). RESULTS:A 20-single-nucleotide polymorphisms PRS for ALC (PRSALC) was generated that stratified risk for ALC comparing the top and bottom deciles of PRS in the 2 validation cohorts (ORs: 2.83 [95% CI: 1.82 -4.39] in UK Biobank; 4.40 [1.56 -12.44] in Indiana Biobank Liver cohort). Furthermore, PRSALC improved the prediction of ALC risk when added to the models of clinically known predictors of ALC risk. It also stratified the risk for metabolic dysfunction -associated steatotic liver disease -cirrhosis (3.94 [2.23 -6.95]) in the Indiana Biobank Liver cohort -based exploratory analysis. CONCLUSIONS:PRSALC incorporates 20 single-nucleotide polymorphisms, predicts increased risk for ALC, and improves risk stratification for ALC compared with the models that only include clinical risk factors. This new score has the potential for early detection of heavy drinking patients who are at high risk for ALC.

Myxosporeans are a diverse group of cnidarian endoparasites of aquatic animals, with more than 2,600 described species. The genus Ceratomyxa includes some 270 species that are mostly coelozoic and infect the gall bladders of mainly marine fish. During our survey in Tapajós River in the Brazilian Amazon, two Ceratomyxa species were discovered in the gallbladders of the anostomid fishes Schyzodon fasciatus and Schyzodon vittatus. Based on myxospore morphology and sequencing of small subunit ribosomal DNA, we propose that these are novel Ceratomyxa species. Ceratomyxa deformis n. sp. from S. fasciatus and Ceratomyxa anomala n. sp. from S. vittatus are similar in morphology, with mature myxospores slightly arcuate with rounded ends. Plasmodia are elongated, and can move by expanding and contracting the cytoplasm. This amoeboid-like motility is heretofore unreported in freshwater South American Ceratomyxa species. Ultrastructural analyses showed the plasmodial organization of both species comprised a cytoplasmic region harboring organelles and sporogonic stages and an internal large vacuole. Phylogenetic analysis corroborates monophyletic grouping of freshwater Ceratomyxa species from South America. Ceratomyxa deformis n. sp. and C. anomala n. sp., which are the first Ceratomyxa species described in anostomid fishes, grouped as sister taxa to C. gracillima and C. mandi, which infect bile in pimelodid fishes from the Amazon region.

BACKGROUND:Myxozoa is a class of cnidarian parasites that encompasses over 2,400 species. Phylogenetic relationships among myxozoans remain highly debated, owing to both a lack of informative morphological characters and a shortage of molecular markers. Mitochondrial (mt) genomes are a common marker in phylogeny and biogeography. However, only five complete myxozoan mt genomes have been sequenced: four belonging to two closely related genera, Enteromyxum and Kudoa, and one from the genus Myxobolus. Interestingly, while cytochrome oxidase genes could be identified in Enteromyxum and Kudoa, no such genes were found in Myxobolus squamalis, and another member of the Myxobolidae (Henneguya salminicola) was found to have lost its entire mt genome. To evaluate the utility of mt genomes to reconstruct myxozoan relationships and to understand if the loss of cytochrome oxidase genes is a characteristic of myxobolids, we sequenced the mt genome of five myxozoans (Myxobolus wulii, M. honghuensis, M. shantungensis, Thelohanellus kitauei and, Sphaeromyxa zaharoni) using Illumina and Oxford Nanopore platforms.RESULTS:Unlike Enteromyxum, which possesses a partitioned mt genome, the five mt genomes were encoded on single circular chromosomes. An mt plasmid was found in M. wulii, as described previously in Kudoa iwatai. In all new myxozoan genomes, five protein-coding genes (cob, cox1, cox2, nad1, and nad5) and two rRNAs (rnl and rns) were recognized, but no tRNA. We found that Myxobolus and Thelohanellus species shared unidentified reading frames, supporting the view that these mt open reading frames are functional. Our phylogenetic reconstructions based on the five conserved mt genes agree with previously published trees based on the 18S rRNA gene.CONCLUSIONS:Our results suggest that the loss of cytochrome oxidase genes is not a characteristic of all myxobolids, the ancestral myxozoan mt genome was likely encoded on a single circular chromosome, and mt plasmids exist in a few lineages. Our findings indicate that myxozoan mt sequences are poor markers for reconstructing myxozoan phylogenetic relationships because of their fast-evolutionary rates and the abundance of repeated elements, which complicates assembly.

Background Checkpoint inhibitor-induced hepatitis (CPI-hepatitis) is an emerging problem with the widening use of CPIs in cancer immunotherapy. Here, we developed a mouse model to characterize the mechanism of CPI-hepatitis and to therapeutically target key pathways driving this pathology.Methods C57BL/6 wild-type (WT) mice were dosed with toll-like receptor (TLR)9 agonist (TLR9-L) for hepatic priming combined with anti-cytotoxic T lymphocyte antigen-4 (CTLA-4) plus anti-programmed cell death 1 (PD-1) (“CPI”) or phosphate buffered saline (PBS) control for up to 7 days. Flow cytometry, histology/immunofluorescence and messenger RNA sequencing were used to characterize liver myeloid/lymphoid subsets and inflammation. Hepatocyte damage was assessed by plasma alanine transaminase (ALT) and cytokeratin-18 (CK-18) measurements. In vivo investigations of CPI-hepatitis were carried out in Rag2−/− and Ccr2rfp/rfp transgenic mice, as well as following anti-CD4, anti-CD8 or cenicriviroc (CVC; CCR2/CCR5 antagonist) treatment.Results Co-administration of combination CPIs with TLR9-L induced liver pathology closely resembling human disease, with increased infiltration and clustering of granzyme B+perforin+CD8+ T cells and CCR2+ monocytes, 7 days post treatment. This was accompanied by apoptotic hepatocytes surrounding these clusters and elevated ALT and CK-18 plasma levels. Liver RNA sequencing identified key signaling pathways (JAK-STAT, NF-ΚB) and cytokine/chemokine networks (Ifnγ, Cxcl9, Ccl2/Ccr2) as drivers of CPI-hepatitis. Using this model, we show that CD8+ T cells mediate hepatocyte damage in experimental CPI-hepatitis. However, their liver recruitment, clustering, and cytotoxic activity is dependent on the presence of CCR2+ monocytes. The absence of hepatic monocyte recruitment in Ccr2rfp/rfp mice and CCR2 inhibition by CVC treatment in WT mice was able to prevent the development and reverse established experimental CPI-hepatitis.Conclusion This newly established mouse model provides a platform for in vivo mechanistic studies of CPI-hepatitis. Using this model, we demonstrate the central role of liver infiltrating CCR2+ monocyte interaction with tissue-destructive CD8+ T cells in the pathogenesis of CPI-hepatitis and highlight CCR2 inhibition as a novel therapeutic target.

In the published publication [...]