ALF-like Mediates Penaeus vannamei Innate Immunity by Recognizing Vibrio parahaemolyticus

The coordination between reactive oxygen species (ROS) and antimicrobial peptide (AMP) responses in invertebrate immunity remains poorly understood. Here, we identify the anti-lipopolysaccharide factor-like protein (ALF-like) from Penaeus vannamei as a functional hub that bridges these two defense layers. We show that ALF-like directly recognizes bacterial components and exerts broad-spectrum bactericidal activity. More importantly, in vivo knockdown and rescue experiments reveal that ALF-like not only restricts bacterial dissemination but also prevents excessive ROS production and modulates the prophenoloxidase system and antioxidant enzyme expression. Thus, ALF-like acts as a dual-functional regulator that couples rapid oxidative killing with restrained, sustained AMP-based immunity. This study offers mechanistic insights into the coordination of crustacean immunity and establishes the ALF-like protein as a promising target for aquaculture disease management.