Class B scavenger receptor resists WSSV replication by recognizing the viral lipid molecule and promoting phagocytosis.

Class B scavenger receptors (SRBs) have been well-studied in bacteria-induced immune responses in invertebrates. However, the status of SRB-defending viruses remains unclear. In this study, we identified a scavenger receptor in (crayfish), which is homologous to mammalian SRBs, and designated it as SRB. The expression of SRB was upregulated after the WSSV challenge. The survival rate of crayfish was decreased, but the WSSV copy number increased after SRB knockdown during virus invasion. In addition, SRB bound to WSSV. Furthermore, we detected how SRB interacted with WSSV, and we found that SRB could bind to cholesta-3,5-diene, (CD3,5), a novel WSSV lipid ligand, rather than dibutyl phthalate (DBP). Besides, SRB could bind to VP19, VP26, and VP28, rather than VP24. Mutant-binding experiments demonstrated that the hydrophobic domain (130-180 aa) of SRB is important for recognizing WSSV. Furthermore, SRB might promote lysosomal eliminating function to degrade WSSV. Altogether, we identified a new mechanism for scavenger receptor recognition and resistance to WSSV.IMPORTANCESRB could bind to WSSV directly. SRB could interact with WSSV via binding to lipid molecule CD3,5 and viral envelope proteins. SRB could influence lysosomal activation.