Fuente: PubMed "swarm" Fish Shellfish Immunol. 2025 Nov 26:111045. doi: 10.1016/j.fsi.2025.111045. Online ahead of print.ABSTRACTAeromonas dhakensis is an emerging zoonotic pathogen in aquaculture, yet the genetic determinants underlying its virulence and immunogenicity remain incompletely understood. Among its potential virulence-associated factors, the wecA gene encodes UDP-N-acetylglucosamine-1-phosphate transferase, a key enzyme in lipopolysaccharide (LPS) core oligosaccharide biosynthesis. In this study, an unmarked wecA deletion mutant (ΔwecA) and complemented strain (CΔwecA) were constructed to investigate the role of wecA in physiology, pathogenicity, and vaccine potential through in vitro assays, cell culture infection, and animal models including Caenorhabditis elegans and zebrafish. Deletion of wecA did not affect growth, swimming motility, or biofilm formation, but significantly increased sensitivity to polymyxin B, compromised membrane integrity, and enhanced swarming motility and hemolytic activity. The ΔwecA mutant exhibited markedly reduced adhesion and early cytotoxicity toward EPC cells and showed substantial attenuation in C. elegans and zebrafish, with higher LD50 values and prolonged survival. Zebrafish immunized with ΔwecA achieved considerable protection against lethal challenge (relative percent survival of 46.7% after primary and 55.6% after booster immunization), accompanied by robust activation of both transcriptional (qRT-PCR) and protein-level (ELISA) immune responses, including upregulation of mucosal barrier (mucin-2), adaptive humoral (IgM), innate immune effectors (MHC-I, TLR2, lysozyme), and various pro-inflammatory cytokines. These results indicate that wecA is crucial for envelope homeostasis and virulence in A. dhakensis. Its deletion resultes in a stable attenuated phenotype capable of inducing protective immunity, demonstrating the potential of a live-attenuated vaccine strategy to reduce disease burden and biosecurity risks in international aquaculture systems.PMID:41314358 | DOI:10.1016/j.fsi.2025.111045