Portunus trituberculatus cryptocyanin seizes swimming crab reovirus and improves crab survival

Abstract

Crustaceans lack immunoglobulins, and their humoral immunity relies on immune factors present in the hemolymph. A native hemolymph protein with a molecular mass of approximately 120 kDa was found to bind the swimming crab (Portunus trituberculatus) reovirus (SCRV) via virus overlay protein binding assays. This protein was identified as cryptocyanin using matrix-assisted laser desorption/ionization time-of-flight mass spectrometry analysis and sequence alignment. The interaction between SCRV and cryptocyanin was confirmed by coimmunoprecipitation. In the antiviral assays in vivo, cryptocyanin enhanced the survival of P. trituberculatus. Our findings showed for the first time that cryptocyanin can seize viruses, suggesting that cryptocyanin may participate in anti‑infective immunity. This study identifies cryptocyanin as a novel and essential component of the invertebrate innate immune system and provides a theoretical basis for elucidating its function in antiviral defense mechanisms.