Molecular cloning and characterization of duck CD83 and its effect on H9N2 avian influenza virus replication.

Cluster of Differentiation 83 (CD83) is a multifunctional regulatory molecule that has been identified in several mammals, birds, and fishes; however, no reports have described CD83 in ducks to date. Given the important role ducks play in the transmission of avian influenza viruses (AIVs), this study aimed to characterize the molecular features of duck CD83 (duCD83) and investigate its potential role during H9N2 AIV infection. We successfully cloned the coding sequence (CDS) and extracellular domain of duCD83 for the first time and expressed the recombinant protein in human embryonic kidney 293T (HEK293T) cells. The results showed that, similar to other species, duCD83 exists as a dimeric glycoprotein and is present in both membrane-bound (dumCD83) and soluble (dusCD83) forms. Sequence analysis revealed high homology between duCD83 and CD83 from swans and chickens, but lower similarity to those from mammals and fishes. Furthermore, duCD83 expression was upregulated in duck embryo fibroblasts (DEFs) following H9N2 AIV infection. Exogenous addition of dusCD83 enhanced viral replication, while knockdown of CD83 expression suppressed it. These findings suggest that duCD83 may play a role in modulating viral replication during H9N2 AIV infection.