Abstract
Rapid emergence of multiple-drug resistance (MDR) of pathogens, together with sluggish discovery of new antibacterial agents has led to the need for high demand of alternative treatments. Among which Pseudomonas aeruginosa involves in around 8−10% of all healthcare-associated infections. Cell surface pathogen-associated molecular patterns (PAMPs) especially glycan moieties play important roles in host-pathogen interaction. Hence bacterial cell surface polysaccharide components have drawn research attention as molecular targets for new therapeutic development. Among various natural resources a Taiwanese horseshoe crab plasma lectin (HPL) has been identified to recognize lipopolysaccharide (LPS) on bacterial cell wall in 2000 followed by functional characterization in 2006. Our laboratory has generated soluble recombinant HPL (rHPL) in an Escherichia coli expression system in 2014. rHPL possssed a mixed secondary structure, and disulfide bond formation was essential for its bacterial binding activity. Both glycan array screening and magnetic reduction (MR) assays revealed that rHPL specifically recognized a unique glycan moiety, rhamnose, located on bacterial PAMPs but not human cell surface. In 2017 multivaent rhamnobosides were synthesized to show higher binding affinities to rHPL than L-rhamnose monosaccharide did. Binding constant between rHPL and rhamnose-containing protein was determined to be in micro-molar range. Moreover, rHPL was discovered to aggregate P. aeruginosa and also inhibit biofilm formation and host cell infection of 2 strains PAO1 and PA14 in a dose dependent manner. Taken together, rHPL may serve as a rhamnose binding protein acting as a natural pathogen recognition molecule, and may further facilitate development of novel diagnostic and therapeutic agent.