Activation of prophenoloxidase, agglutinin and antibacterial activity in haemolymph of the black tiger prawn, Penaeus monodon, by immunostimulants

Abstract

The in vitro effect of the microbial cell wall components peptidoglycan (PG), lipopolysaccharide (LPS) and laminarin (β-1,3 glucan) on the haemolymph agglutinating and antibacterial activities were investigated in the black tiger shrimp, Penaeus monodon, using phenoloxidase (PO) activity as a reference. The effect on these factors of 3 orally administered commercial stimulants, PENSTIM, BRM-01 and BRM-02, was also determined. The study was done using shrimp haemocyte lysate fraction (HLF). It was shown that PO, agglutinating and antibacterial activities occurred naturally in shrimp haemolymph and varied considerably amongst individuals. Concentrations of PG at 0·4% and LPS at 0·002% added to HLF gave 22-fold and 11-fold increased PO activity in vitro, respectively, over the activity of HLF alone. By contrast, addition of laminarin did not increase PO activity. Attempts to stimulate agglutinating and antibacterial activity in vitro or in vivo were unsuccessful. On the contrary, 0·002% LPS was found to have an inhibitory effect on antibacterial activity. Specifically, a lower antibacterial activity was detected in samples treated with LPS after clotting (HLF), than in those treated before clotting. This suggested that LPS was involved in mechanisms for both clotting and for antibacterial activity. No relationships were found amongst PO, agglutinin and antibacterial activities in shrimp haemolymph either naturally or by activation. © 1999 Academic Press.