Abstract: In order to construct the UL41 gene deletion strain of duck enteritis virus (DEV), the recombinant fosmid D1 dUL41 with UL41 gene deletion was constructed by using Red/ET recombinant technique with the recombinant fosmid D1 containing UL41 gene as the backbone. The UL41 gene deletion fosmid D1 dUL41 was co-transfected into duck embryo fibroblasts (DEF) with four other parent fosmids containing DEV genomic fragments, and the UL41 gene deletion strain rDEV-SD19/dUL41 was obtained. After the UL41 deletion virus was inoculated on DEF, the virus genome was extracted for PCR identification and sequencing, and the expression of UL41 gene in the infected cells was detected by indirect immunofluorescence assay. The growth curve of the rescued gene deletion virus was tested and its replication characteristics in vitro were analyzed. The PCR and sequencing results showed that the recombinant fosmid D1 dUL41 with UL41 deletion was obtained in this study. Typical plaque lesions can be produced after co-transfection of the UL41-deletion fosmid with other parent fosmids containing DEV genomic fragments. The results of PCR and sequencing showed that UL41 gene was successfully deleted from the DEV genome, and indirect immunofluorescence assay showed that there was no expression of UL41 protein after the inoculation of rDEV-SD19/dUL41 in DEFs. The growth curve in vitro showed that the replication ability of rDEV-SD19/dUL41 in DEF was significantly lower than that of the parent virus, indicating that UL41 gene plays important roles in DEV replication. The construction of DEV UL41 gene deletion strain lays a foundation for the study of the function of UL41 gene in DEV infection and pathogenesis.

Key words: duck enteritis virus, UL41 gene, gene deletion, replication ability