Ingestion of polystyrene microplastics by Bombyx mori larvae disrupts midgut epithelial barrier integrity and potentially promotes susceptibility to BmNPV infection

Microplastics (MPs) are ubiquitous environmental contaminants with potential implications for host-virus interactions, which has attracted global interest because MPs have been recognized as emerging pollutants. Despite growing concern over MPs, their influence on viral infections, particularly in invertebrate models, remains poorly understood. In this study, we employed the silkworm, Bombyx mori, as a model organism to investigate the impact of microplastic (MP) exposure on viral replication and the gut microbiome. Real-time PCR and Western blotting results showed that exposure to MPs was accompanied by significantly increased BmNPV viral gene expression (ie-1, vp39, gp41) and VP39 production in the midgut, suggesting an increase in BmNPV replication. Exposure to MPs disrupted gut microbiome composition, leading to a decrease in beneficial bacteria (e.g., Vibrionaceae) and an increase in opportunistic pathogens, potentially contributing to increased susceptibility to BmNPV. Notably, the increased permeability of the midgut epithelium in response to MP exposure likely facilitated viral entry and enhanced infection. These findings underscore the potential risks of MPs in facilitating viral replication and systemic infection and emphasize the necessity of further research to explore the complex relationships between MPs, gut microbiota, and viral infections across different ecological settings.