Insights from healthy mares reveal that mammalian uteri harbor a diverse virome.

Overview

• This study investigates the presence and diversity of viruses within the uterus of healthy mares (female horses), uncovering a previously unknown and complex community of native viruses (virome) in the mammalian uterus.

Introduction to Viromes and Their Importance

• The Earth is home to an estimated 10^31 virions, primarily bacteriophages (phages) that infect bacteria, profoundly influencing microbial ecosystems.
• Despite their abundance, viromes remain relatively understudied, especially in domestic animals and within specific organs like the uterus.
• Prior research has characterized the bacterial microbiome of the mammalian uterus as dynamic and commensal, but the viral component within the uterus has not been characterized before this study.

Research Objectives and Novelty

• This study aimed to identify and characterize the native virome present in the equine uterus, using healthy mares as a model.
• It is the first research to report and establish a comprehensive uterine virome in any mammal.

Methodology and Data Collection

• Samples were taken from healthy mares to extract and sequence viral genomes present in the uterine environment.
• A database was compiled consisting of 513 non-redundant viral genomes exceeding 2 kilobases in length.
• Taxonomic annotation was performed to classify the viruses at the genus level and understand their diversity.

Key Results and Findings

• The uterine virome was sparse but highly diverse.
• Dominant viral taxa identified included the genera:
  • Gammaretrovirus (a genus of retroviruses)
  • Mamastrovirus (astroviruses commonly found in mammals)
  • Sapovirus (a type of calicivirus, often associated with gastrointestinal infections)
  • Rosenblumvirus (a genus of phages)
• 75% of the assembled viral genomes represented novel species that had not been previously identified, indicating substantial unexplored viral diversity.
• Phylogenetic analyses showed distinct viral clades unique to the uterine environment, hinting at specialized adaption or evolution within this niche.
• Predictions of bacterial hosts for the detected phages aligned well with previous studies of equine uterine bacteria, providing ecological context for phage-host interactions.
• Antibiotic resistance genes were identified within the viral genomes, suggesting possible mechanisms for horizontal gene transfer between viruses and bacteria in the uterus.

Significance and Implications of the Study

• This work is pioneering as it lays the foundation for understanding the virome in the mammalian uterus.
• Discovering native phages and their interactions with bacterial hosts opens opportunities for phage therapy to treat reproductive infectious diseases in animals and potentially humans.
• Recognition of antibiotic resistance genes in the uterine virome raises important considerations for antimicrobial resistance spread within the maternal gestational environment.
• The research underscores the complexity and biological significance of the maternal reproductive microbiome, beyond just bacteria.

Future Directions

• Further studies are needed to expand the uterine virome databases across different species and reproductive states.
• More research can elucidate the functional roles of the virome in uterine health, reproduction, maternal-fetal interactions, and disease susceptibility.
• Understanding virome dynamics may help harness beneficial viral elements or control harmful infectious agents to improve reproductive outcomes.
• Integrating virome data with bacterial microbiome and host immune profiles will provide a holistic view of the uterine ecosystem.