Demonstration of residual antibacterial activity in plasma of vaccinated Penaeus vannamei

Plasma from naive Penaeus vannamei juveniles lacked antibacterial factors a nd significantly enhanced the growth of Escherichia coli strain XL1-Blue MR F' compared with sea water complex (SWC) nutrient medium. In contrast, plas ma from prawns previously injected with both live, non pathogenic Vibrio ha rveyi strain DPEX and formalin-killed cells of V. harveyi strains BP04, DPE X, E, coli and sterile shrimp salt solution (SSS), inhibited bacterial grow th. Antibacterial activity appeared within 6 h and was detectable until 7 d ays after "vaccine" administration. Lysozyme activity was not detected in p lasma from vaccinated prawns. Both in vitro and in vivo bacterial killing w ere facilitated by vaccine administration. Activation of the prophenoloxida se (proPO) system was independent of bacterial virulence. (C) 2000 Elsevier Science B.V. All rights reserved.