Introduction Directory UMM :Data Elmu:jurnal:A:Aquaculture:Vol187.Issue1-2.Jul2000:

Ž . Aquaculture 187 2000 15–34 www.elsevier.nl rlocateraqua-online Demonstration of residual antibacterial activity in plasma of vaccinated Penaeus Õannamei A.O. Alabi , J.W. Latchford, D.A. Jones School of Ocean Sciences, UniÕersity of Wales, Bangor, Menai Bridge, LL57 5EY, UK Received 4 August 1998 ; received in revised form 11 December 1999 ; accepted 26 December 1999 Abstract Plasma from naıve Penaeus Õannamei juveniles lacked antibacterial factors and significantly ¨ enhanced the growth of Escherichia coli strain XL1-Blue MRF X compared with sea water Ž . complex SWC nutrient medium. In contrast, plasma from prawns previously injected with both live, non pathogenic Vibrio harÕeyi strain DPEX and formalin-killed cells of V. harÕeyi strains Ž . BP04, DPEX, E. coli and sterile shrimp salt solution SSS , inhibited bacterial growth. Antibacte- rial activity appeared within 6 h and was detectable until 7 days after ‘‘ vaccine’’ administration. Lysozyme activity was not detected in plasma from vaccinated prawns. Both in vitro and in vivo bacterial killing were facilitated by vaccine administration. Activation of the prophenoloxidase Ž . proPO system was independent of bacterial virulence. q 2000 Elsevier Science B.V. All rights reserved. Keywords: Immune system; Prophenoloxidase system; Antibacterial activity

1. Introduction

Most of the bacteria causing diseases in cultured prawns from farms and hatcheries Ž have been reported as part of the normal prawn microflora Vanderzant et al., 1971; Corresponding author. Current address: Island Scallops Ltd., 5552 West Island Highway, Qualicum Beach, BC, Canada, V9K 2C8. Tel.: q1-250-757-9811; fax: q1-250-757-8370. Ž . E-mail address: islandscallopsbcsupernet.com A.O. Alabi . 0044-8486 r00r - see front matter q 2000 Elsevier Science B.V. All rights reserved. Ž . PII: S 0 0 4 4 - 8 4 8 6 0 0 0 0 3 0 5 - 7 Yasuda and Kitao, 1980; Ruangpan, 1982; Lightner, 1985, 1988, 1992; Lavilla-Pitogo et al., 1990; Owens et al., 1992; Mohney et al., 1994; Prayitno, 1994; Prayitno and . Latchford, 1995 . Increased susceptibility to disease found in farmed prawns occurs as a consequence of impairment of the immune defense mechanisms resulting from the physical and environmental abuse characteristic of many aquaculture systems. With the growing importance of disease in prawn culture systems, a detailed knowledge of the functioning of the defense system of prawns is essential in disease control and treatment. Immunostimulation of prawns using products of microbial origin has been reported to Ž enhance resistance against disease causing pathogens Adams, 1991; Prayitno, 1994; . Latchford et al., 1995; Sung et al., 1996; Alabi et al., 1999 . Although both humoral and Ž cellular factors have been implicated in these resistance procedures Itami et al., 1989; . Adams, 1991; Vargas-Albores, 1995; Vargas-Albores et al., 1993b; Sung et al., 1996 , research has been primarily focused on processes of cellular immunity especially with Ž regard to generation of reactive oxygen species Song and Hsieh, 1994; Sung et al., . Ž . 1996 , phagocytosis Hose and Martin, 1989; Vargas-Albores, 1995 , encapsulation Ž . Hose and Martin, 1989 , and multimeric systems such as the coagulation system Ž . Ž . Omori et al., 1989 and the prophenoloxidase proPO enzyme activation system ŽSoderhall, 1982; Soderhall and Unestam, 1979; Smith and Soderhall, 1983; Ashida and ¨ ¨ ¨ ¨ ¨ ¨ Soderhall, 1984; Hose et al., 1987; Chisholm and Smith, 1992; Vargas-Albores, 1995; ¨ ¨ . Vargas-Albores et al., 1993a; Sung et al., 1996 . Apart from these immediate responses to microbial infection, longer lasting antimi- crobial factors represent another component of the invertebrate immune response Ž . Ratcliff et al., 1985 . Lysozyme-like activity has already been demonstrated in the Ž haemolymph of several insects Hultmark et al., 1980; Engstrom et al., 1984; Kaaya et ¨ . Ž al., 1987 and bivalves Cheng and Rodrick, 1974; Foley and Cheng, 1977; Cheng et al., 1980 . Results of attempts to demonstrate lysozyme activity in penaeid prawns have so Ž . far been equivocal. Some authors Guzman et al., 1993 have reported haemolytic ´ Ž activity in cell free haemolymph of Penaeus Õannamei while other researchers Noga et . al., 1996 have been unsuccessful in demonstrating such with P. setifeus. Antibacterial factors with properties clearly different from those of lysozyme have Ž also been reported in insects Faye and Wyatt, 1980; Yoshida and Ashida, 1986; Boman . and Hultmark, 1987 and a few studies have described the acquisition of a longer lasting Ž ‘‘immune’’ state following exposure of prawns to killed Vibrio sp. cells Itami et al., . Ž 1989; Adams, 1991; Prayitno, 1994; Alabi et al., 1999 and immunostimulants Sung et . al., 1996 . However, the significance of these long-term resistance factors to overall disease resistance has not been shown yet. The resistance of ‘‘immunized’’ penaeid prawns to infection by a normally pathogenic bacterium following prophylaxis may provide a model for studies of prawn antibacterial immunity and knowledge of bacterial dynamics in vitro and in vivo in such prawns, coupled with studies of humoral and cellular defense mechanisms and bacterial viru- lence factors may offer increased manipulative advantages in prawn growing regions. In this study, the elicitation and duration of induced antibacterial activity was investigated and related to the capacity for in vitro and in vivo destruction of several bacterial species by immunized and naıve plasma of P. Õannamei. The ability of different bacterial ¨ species to activate the proPO system in P. Õannamei was also assessed.

2. Materials and methods