Passive immunization of the tiger prawn, Penaeus monodon, using rabbit antisera to Vibrio harveyi

Passive immunization, toxicity neutralization and the persistence of passive protection in the tiger prawn (Penaeus monodon) were investigated using rabbit antisera to the formalinized extracellular products (ECP) (R alpha ECP) and/or formalinized bacterial cells (R alpha BC) of luminescent Vibrio harveyi strain 820514 originally isolated from diseased tiger prawns. Rabbit antiserum to bovine serum albumin (R alpha BSA) or phosphate-buffered saline (PBS, pH 7.2) both served as controls. The toxicity of ECP to prawns was neutralized by pre-incubation with R alpha ECP. Passive immunization by pre-injection of R alpha BC or R alpha ECP into prawns 3 d in advance protected against a lethal dose challenge of bacteria. To determine the persistence of passive protection by rabbit antiserum in tiger prawns, the R alpha BC, R alpha ECP, R alpha BSA or PBS were injected into prawns. At 10, 17 or 24 d post-immunization, groups of prawns were given a lethal dose challenge of bacteria. The prawns in the two control groups were all killed within the first 2 d following challenge at all three challenge dates. Pre-injection with R alpha BC and R alpha ECP provided total protection for 10 and 17 d, respectively, with all treated prawns surviving for at least 2 weeks post-challenge. This is the first study using mammalian antisera to investigate toxicity neutralization, passive immunization and persistence of passive protection by rabbit antisera in prawns. The results could be useful in future studies on virulence mechanisms and disease control of vibriosis in cultured prawns.