Integrative analysis of circRNA/miRNA/mRNA regulatory network in Bombyx mori fat body. Firstly, RNA-seq and small RNA sequencing were used to identify the differentially expressed circRNAs, mRNAs and miRNAs of B. Mori fat body with BmNPV infection or not. Subsequently, GO and KEGG pathway analysis of host genes and target genes for circRNAs were performed. PCR with divergent primers and convergent primers and Sanger sequencing were used to validate selected circRNAs. Then, based on ceRNA theory, DEcircRNA-DEmiRNA-DEmRNA regulatory network upon BmNPV infection was constructed. Finally, the differential expressions of circ_0001432 and its corresponding miRNA and mRNA in the network were validated by qPCR. • 77 DEcircRNA, 32 DEmiRNA and 730 DEmRNA were identified in BmNPV-infected fat body. • DEcircRNA/DEmiRNA/DEmRNA gene regulatory networks were constructed. • circRNA_0001432 may regulate genes in response to BmNPV infection. Bombyx mori nucleopolyhedrosis virus (BmNPV) is one of the greatest threats to sustainable development of the sericulture industry. Circular RNA (circRNA), a type of non-coding RNA, has been shown to play important roles in gene expression regulation, immune response, and diseases. The fat body is a tissue with both metabolic and immune functions. To explore the potential immune function of circRNAs, we analyzed differentially expressed (DE)circRNAs, microRNAs(miRNAs), and mRNAs in the B. mori fat body in response to BmNPV infection using high-throughput RNA sequencing. A total of 77 DEcircRNAs, 32 DEmiRNAs, and 730 DEmRNAs that are associated with BmNPV infection were identified. We constructed a DEcircRNA/DEmiRNA/DEmRNA and DEcircRNA/DEmiRNA/BmNPV gene regulatory network and validated the differential expression of circ_0001432 and its corresponding miRNA (miR-2774c and miR-3406-5p) and mRNA (778467 and 101745232) in the network. Tissue-specific expression of circ_0001432 and its expression at different time points were also examined. KEGG pathway analysis of DEmRNAs, target genes of DEmiRNAs, and host genes of DEcircRNAs in the network showed that these genes were enriched in several metabolic pathways and signaling pathways, which could play important roles in insect immune responses. Our results suggest that circRNA could be involved in immune responses of the B. mori fat body and help in understanding the molecular mechanisms underlying silkworm–pathogen interactions. [ABSTRACT FROM AUTHOR]