Abstract: 【Aim】 The objective of this study is to explore the effects of chronic bee paralysis virus (CBPV) infection on the immunity and gut microbiota of Apis cerana cerana. 【Methods】 The newly emerged adult workers of A. c. cerana were infected with CBPV by injecting CBPV RNA, and the survival rate was recorded. qRT-PCR was used to detect the genomic copy number of CBPV and the expression levels of 15 immune-related genes (PGRP-S2, Cactus1, Toll, PGRPLC-like, Relish, Defensin1, Hymenoptaecin, SP14, PPO, Dicer, HSP70, HSP90, Stat, Stam and PISA3) in the CBPV-infected A. c. cerana workers. Metagenomic sequencing was used to detect the change of the gut microbiota structure in the CSBV-infected A. c. cerana workers, and alpha- and beta- diversity analyses of gut microbiota were performed. 【Results】The survival rate of A. c. cerana adult workers infected with CBPV gradually decreased as compared with that of the control group injected with 1×PBS, and the cumulative survival rate decreased to 27% on the 7th day after infection. The overall trend of the genomic copy number of CBPV increased sharply and steadily from the 1st-4th day, with a 10⁶-fold increase of genomic copy number on the 4th day after infection. Meanwhile, CBPV infection significantly activated the Toll immune pathway genes, especially the antimicrobial peptide genes Defensin1 and Hymenoptaecin, with their expression levels significantly up-regulated on the 1st-5th day after CBPV infection and more than 10-fold on the 5th day. Metagenomic sequencing result showed that CBPV infection affected the gut microbiota structure, and significantly changed the gut microbiota diversity of A. c. cerana workers, especially the relative abundance of Lactobacillus apis and Snodgrassella alvi was significantly down-regulated in the CBPV-infected A. c. cerana as compared with that in the control. 【Conclusion】 CBPV infection can cause the death of A. c. cerana workers, activate the expression of antimicrobial peptide genes and significantly reduce the relative abundance of beneficial bacteria in the gut. The results provide an important theoretical basis for developing bees’ new health management strategies and prevention and control measures.

Key words: Apis cerana cerana, chronic bee paralysis virus, immunity, antimicrobial peptides, gut microbiota