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Inflammatory bowel disease (IBD) refers to chronic, recurrent inflammatory intestinal disorders, primarily including Crohn’s disease (CD) and Ulcerative colitis (UC). Numerous studies have elucidated the importance of the gut microbiome in IBD. Recently, numerous studies have focused on the gut virome, an intriguing and enigmatic aspect of the gut microbiome. Alterations in the composition of phages, eukaryotic viruses, and human endogenous retroviruses that occur in IBD suggest potential involvement of the gut virome in IBD. Nevertheless, the mechanisms by which it maintains intestinal homeostasis and interacts with diseases are only beginning to be understood. Here, we thoroughly reviewed the composition of the gut virome in both healthy individuals and IBD patients, emphasizing the key viruses implicated in the onset and progression of IBD. Furthermore, the complex connections between the gut virome and the intestinal barrier, immunity, and gut microbiome were dissected to advance the interpretation of IBD pathogenesis. The updated discussion of the evidence regarding the gut virome will advance our knowledge in gut virome and chronic gastrointestinal diseases. Targeting the gut virome is a promising avenue for IBD treatment in future.

The human gastrointestinal (GI) tract harbors eukaryotic and prokaryotic viruses and their genomes, metabolites, and proteins, collectively known as the “gut virome”. This complex community of viruses colonizing the enteric mucosa is pivotal in regulating host immunity. The mechanisms involved in cross communication between mucosal immunity and the gut virome, as well as their relationship in health and disease, remain largely unknown. Herein, we review the literature on the human gut virome’s composition and evolution and the interplay between the gut virome and enteric mucosal immunity and their molecular mechanisms. Our review suggests that future research efforts should focus on unraveling the mechanisms of gut viruses in human homeostasis and pathophysiology and on developing virus-prompted precision therapies.

The contribution of dysbiotic gut microbiota configuration is essential when making reference to the metabolic disorders by increasing energy. It is important to understand that the gut microbiota induced metabolic disease mechanisms and inflammations. Thus it is imperative to have an insight into the state of all chronic subclinical inflammations influencing disease outcomes. However, from the emerging studies, there still exist inconsistencies in the findings of such studies. While making the best out of the reasons for inconsistencies of the findings, this review is designed to make a clear spell out as to the inconsistence of gut microbiota with respect to diabetes. It considered gut-virome alterations and diabetes and gut-bacteriome-gut-virome-alterations and diabetes as confounding factors. The review further explained some study design strategies that will spontaneously eliminate any potential confounding factors to lead to a more evidence based diabetic-gut microbiota medicine. Lipopolysaccharide (LPS) pro-inflammatory, metabolic endotoxemia and diet/gut microbiota insulin-resistance and low-grade systemic inflammation induced by gut microbiota can trigger pro-inflammatory cytokines in insulin-resistance, consequently, leading to the diabetic condition. While diet influences the gut microbiota, the consequences are mainly the constant high levels of pro-inflammatory cytokines in the circulatory system. Of recent, dietary natural products have been shown to be anti-diabetic. The effects of resveratrol on the gut showed an improved lipid profile, anti-inflammatory properties and ameliorated the endotoxemia, tight junction and glucose intolerance.

Through generation of the DEVoC, we added numerous previously uncharacterized viral genomes and genes to the ever-increasing worldwide pool of human gut viromes. The DEVoC, the largest human gut virome catalog generated from consistently processed fecal samples, facilitated the analysis of the 91 healthy Danish gut viromes. Gut viruses are important, yet often neglected, players in the complex human gut microbial ecosystem. Recently, the number of human gut virome studies has been increasing; however, we are still only scratching the surface of the immense viral diversity. In this study, 254 virus-enriched fecal metagenomes from 204 Danish subjects were used to generate the D anish E nteric V ir o me C atalog (DEVoC) containing 12,986 nonredundant viral scaffolds, of which the majority was previously undescribed, encoding 190,029 viral genes. The DEVoC was used to compare 91 healthy DEVoC gut viromes from children, adolescents, and adults that were used to create the DEVoC. Gut viromes of healthy Danish subjects were dominated by phages. While most phage genomes (PGs) only occurred in a single subject, indicating large virome individuality, 39 PGs were present in more than 10 healthy subjects. Among these 39 PGs, the prevalences of three PGs were associated with age. To further study the prevalence of these 39 prevalent PGs, 1,880 gut virome data sets of 27 studies from across the world were screened, revealing several age-, geography-, and disease-related prevalence patterns. Two PGs also showed a remarkably high prevalence worldwide—a crAss-like phage (20.6% prevalence), belonging to the tentative AlphacrAssvirinae subfamily, and a previously undescribed circular temperate phage infecting Bacteroides dorei (14.4% prevalence), called LoVEphage because it encodes l ots o f v iral e lements. Due to the LoVEphage’s high prevalence and novelty, public data sets in which the LoVEphage was detected were de novo assembled, resulting in an additional 18 circular LoVEphage-like genomes (67.9 to 72.4 kb). IMPORTANCE Through generation of the DEVoC, we added numerous previously uncharacterized viral genomes and genes to the ever-increasing worldwide pool of human gut viromes. The DEVoC, the largest human gut virome catalog generated from consistently processed fecal samples, facilitated the analysis of the 91 healthy Danish gut viromes. Characterizing the biggest cohort of healthy gut viromes from children, adolescents, and adults to date confirmed the previously established high interindividual variation in human gut viromes and demonstrated that the effect of age on the gut virome composition was limited to the prevalence of specific phage (groups). The identification of a previously undescribed prevalent phage illustrates the usefulness of developing virome catalogs, and we foresee that the DEVoC will benefit future analysis of the roles of gut viruses in human health and disease.

Gut viruses are important, yet often neglected, players in the complex human gut microbial ecosystem. Recently, the number of human gut virome studies has been increasing; however, we are still only scratching the surface of the immense viral diversity. In this study, 254 virus-enriched fecal metagenomes from 204 Danish subjects were used to generate the Danish Enteric Virome Catalog (DEVoC) containing 12,986 nonredundant viral scaffolds, of which the majority was previously undescribed, encoding 190,029 viral genes. The DEVoC was used to compare 91 healthy DEVoC gut viromes from children, adolescents, and adults that were used to create the DEVoC. Gut viromes of healthy Danish subjects were dominated by phages. While most phage genomes (PGs) only occurred in a single subject, indicating large virome individuality, 39 PGs were present in more than 10 healthy subjects. Among these 39 PGs, the prevalences of three PGs were associated with age. To further study the prevalence of these 39 prevalent PGs, 1,880 gut virome data sets of 27 studies from across the world were screened, revealing several age-, geography-, and disease-related prevalence patterns. Two PGs also showed a remarkably high prevalence worldwide—a crAss-like phage (20.6% prevalence), belonging to the tentative AlphacrAssvirinae subfamily, and a previously undescribed circular temperate phage infecting Bacteroides dorei (14.4% prevalence), called LoVEphage because it encodes lots of viral elements. Due to the LoVEphage’s high prevalence and novelty, public data sets in which the LoVEphage was detected were de novo assembled, resulting in an additional 18 circular LoVEphage-like genomes (67.9 to 72.4 kb). IMPORTANCE Through generation of the DEVoC, we added numerous previously uncharacterized viral genomes and genes to the ever-increasing worldwide pool of human gut viromes. The DEVoC, the largest human gut virome catalog generated from consistently processed fecal samples, facilitated the analysis of the 91 healthy Danish gut viromes. Characterizing the biggest cohort of healthy gut viromes from children, adolescents, and adults to date confirmed the previously established high interindividual variation in human gut viromes and demonstrated that the effect of age on the gut virome composition was limited to the prevalence of specific phage (groups). The identification of a previously undescribed prevalent phage illustrates the usefulness of developing virome catalogs, and we foresee that the DEVoC will benefit future analysis of the roles of gut viruses in human health and disease.

The human gut virome includes a diverse collection of viruses that infect our own cells as well as other commensal organisms, directly impacting on our well-being. Despite its predominance, the virome remains one of the least understood components of the gut microbiota, with appropriate analysis toolkits still in development. Based on its interconnectivity with all living cells, it is clear that the virome cannot be studied in isolation. Here we review the current understanding of the human gut virome, specifically in relation to other constituents of the microbiome, its evolution and life-long association with its host, and our current understanding in the context of inflammatory bowel disease and associated therapies. We propose that the gut virome and the gut bacterial microbiome share similar trajectories and interact in both health and disease and that future microbiota studies should in parallel characterize the gut virome to uncover its role in health and disease.

Background The gut virome has been implicated in inflammatory bowel disease (IBD), yet a full understanding of the gut virome in IBD patients, especially across diverse geographic populations, is lacking. Results In this study, we conducted a comprehensive gut virome-wide association study in a Chinese cohort of 71 IBD patients (15 with Crohn’s disease and 56 with ulcerative colitis) and 77 healthy controls via viral-like particle (VLP) and bulk virome sequencing of their feces. By utilizing an integrated gut virus catalog tailored to the IBD virome, we revealed fundamental alterations in the gut virome in IBD patients. These characterized 139 differentially abundant viral signatures, including elevated phages predicted to infect Escherichia , Klebsiella , Enterococcus_B , Streptococcus , and Veillonella species , as well as IBD-depleted phages targeting Prevotella , Ruminococcus_E , Bifidobacterium , and Blautia species . Remarkably, these viral signatures demonstrated high consistency across diverse populations such as those in Europe and the USA, emphasizing their significance and broad relevance in the disease context. Furthermore, fecal virome transplantation experiments verified that the colonization of these IBD-characterized viruses can modulate experimental colitis in mouse models. Conclusions Building upon these insights into the IBD gut virome, we identified potential biomarkers for prognosis and therapy in IBD patients, laying the foundation for further exploration of viromes in related conditions. -rW5fkHC-UvmYPog5oPfKK Video Abstract

Key Points CRISPR–Cas (clustered regularly interspaced short palindromic repeats–CRISPR-associated proteins) is an adaptive immune system in bacteria and archaea, which is categorized into three distinct types (known as type I, type II and type III) that differ in their compositions and mechanisms of action. Adaptive immunity occurs in three distinct stages: acquisition, expression and interference. In all three types of CRISPR–Cas system, spacer acquisition relies on a pair of conserved Cas proteins (Cas1 and Cas2), which are probably assisted by a variable set of additional (potentially both Cas and non-Cas) enzymes. Primary processing of CRISPR RNAs (crRNAs) is catalysed either by Cas6-like ribonucleases (in the type I and type III systems) or by RNase III (which targets the crRNA and transactivating crRNA (tracrRNA) duplex in type II systems). Mature crRNAs form CRISPR ribonucleoprotein (crRNP) complexes by associating with either Cascade-like multiprotein complexes (in type I and type III systems) or the multidomain Cas9 protein (in type II systems). Discrimination of 'self' nucleic acid from 'non-self' nucleic acid enables crRNP complexes to specifically target invading nucleic acid (usually DNA). Some complexes recruit additional nucleases (for example, Cas3 in type I systems), whereas other crRNPs have intrinsic nuclease domains (for example, Cas9 in type II systems). Fundamental studies have elucidated many mechanistic features of CRISPR–Cas functionality by integrating genetics, biochemistry and structural biology. This has provided an excellent basis for developing a wide range of applications, from the manipulation of gene expression in bacteria to genome editing in eukaryotes. In this Review, van der Oost et al . summarize the recent structural and biochemical insights into the molecular mechanisms of RNA-guided interference by CRISPR–Cas systems in bacteria and archaea. By comparing the three main types of CRISPR–Cas systems, they highlight the unique and conserved properties of the system and also discuss outstanding questions that require further study. Bacteria and archaea have evolved sophisticated adaptive immune systems, known as CRISPR–Cas (clustered regularly interspaced short palindromic repeats–CRISPR-associated proteins) systems, which target and inactivate invading viruses and plasmids. Immunity is acquired by integrating short fragments of foreign DNA into CRISPR loci, and following transcription and processing of these loci, the CRISPR RNAs (crRNAs) guide the Cas proteins to complementary invading nucleic acid, which results in target interference. In this Review, we summarize the recent structural and biochemical insights that have been gained for the three major types of CRISPR–Cas systems, which together provide a detailed molecular understanding of the unique and conserved mechanisms of RNA-guided adaptive immunity in bacteria and archaea.

Ankylosing spondylitis (AS), a chronic autoimmune disease, has been linked to the gut bacteriome. To investigate the characteristics of the gut virome in AS, we profiled the gut viral community of 193 AS patients and 59 healthy subjects based on a metagenome-wide analysis of fecal metagenomes from two publicly available datasets. AS patients revealed a significant decrease in gut viral richness and a considerable alteration of the overall viral structure. At the family level, AS patients had an increased abundance of and and a decreased abundance of and . We identified 1,004 differentially abundant viral operational taxonomic units (vOTUs) between patients and controls, including a higher proportion of AS-enriched viruses and control-enriched viruses. Moreover, the AS-enriched vOTUs were more likely to infect bacteria such as , , and , whereas the control-enriched vOTUs were more likely to be , , , , and bacteriophages. Additionally, some viral functional orthologs differed significantly in frequency between the AS-enriched and control-enriched vOTUs, suggesting the functional role of these AS-associated viruses. Moreover, we trained classification models based on gut viral signatures to discriminate AS patients from healthy controls, with an optimal area under the receiver operator characteristic curve (AUC) up to 0.936, suggesting the clinical potential of the gut virome for diagnosing AS. This work provides novel insight into the AS gut virome, and the findings may guide future mechanistic and therapeutic studies for other autoimmune diseases.

Background Schizophrenia (SCZ) is a multifactorial psychiatric disorder increasingly linked to gut microbial dysbiosis. While bacterial alterations have been widely studied, the role of the gut virome in SCZ remains largely unexplored. This study aimed to characterize the gut virome in SCZ and identify potential viral biomarkers associated with the disease. Methods We analyzed fecal metagenomic data from 171 individuals (90 SCZ patients and 81 controls) using the Chinese Gut Virus Catalog (cnGVC). We assessed gut virome diversity, identified SCZ-associated vOTUs, explored virus–bacteria correlations, and evaluated diagnostic potential using random forest models. In addition, we examined follow-up samples from SCZ patients to assess the impact of antipsychotic treatment on the gut virome. Results We identified 171 vOTUs that differed significantly between SCZ patients and controls, with 124 enriched in SCZ—mainly from Siphoviridae and Flandersviridae . Correlation analysis revealed altered virus–bacteria interactions in SCZ, including disease-specific associations with Akkermansia and Clostridia . A random forest classifier based on virome features achieved an AUC of 93.2%, outperforming the bacterial model. External validation using ASD and PD cohorts yielded lower AUCs (61.2–67.0%), suggesting disease specificity. In follow-up samples collected after three months of treatment, we observed partial changes in alpha diversity, while beta diversity remained stable, indicating that antipsychotic therapy may alter specific viral taxa without broadly reshaping the overall gut virome structure. Conclusions This study provides evidence of distinct gut virome alterations in SCZ and identifies specific viral markers with strong diagnostic potential. These findings highlight the underappreciated role of the gut virome in psychiatric disorders and support its utility as a non-invasive biomarker for SCZ diagnosis and future therapeutic development.