Cloning, characterisation and functional analysis of horseshoe crab c-reactive proteins

Abstract

The horseshoe crab, Carcinoscorpius rotundicauda, possesses a powerful innate immune system capable of clearing Gram-negative bacteria (GNB) infections that would be lethal to mice. Rapid bacterial clearance suggests the existence of frontline defense molecules that recognize lipopolysaccharide (LPS). C-reactive protein (CRP)-1 and -2 are extracellular lectins that bind LPS. This study aims to elucidate the roles of CRP-1 and -2. CRP-1 and-2 interact with different protein partners, and possibly mediate different immune response pathways. rCRP-1 and -2 interact with proteins of the na??ve cell-free hemolymph (CFH). This represents a pool of innate immune molecules that associate into a a??pathogen-recognition complexa?? early in infection. The interactions of both rCRP-1 and -2 are enhanced during infection and in the presence of calcium. CRP-2 exhibits bacterial agglutination and bactericidal activities. Calcium did not enhance bactericidal activity, suggesting it is not necessary for CRP-2a??s antimicrobial properties but is important for a??pathogen-recognition complexa?? recruitment.