Recombinant anti-lipopolysaccharide factor isoform 3 and the prevention of vibriosis in the black tiger shrimp, Penaeus monodon

Abstract

Anti-lipopolysaccharide factors are antimicrobial peptides previously identified in shrimps and other crustaceans. The high activity against a shrimp pathogenic bacterium, Vibrio harveyi, of the recombinant Penaeus monodon anti-lipopolysaccharide factor isoform 3 protein (rALF Pm3) suggested its potential use in the control or prevention of outbreaks of vibriosis in shrimp farming. We further investigated its activity in vivo in terms of neutralization and protective effects in shrimps challenged with V. harveyi. Prior incubation of V. harveyi with rALF Pm3 at concentrations of 6.25 µM or higher completely neutralized the bacteria's pathogenicity to shrimps as shown by 100% shrimp survival following systemic challenge with an otherwise lethal dose. Pre-injection of shrimps with rALF Pm3 prior to V. harveyi infection reduced the cumulative mortality 2.4 fold compared to the control shrimps injected with saline solution, suggesting a potential prophylactic effect. The effects of rALF Pm3 injection on the expression levels of five immune genes, ALF Pm3, phagocytosis activating protein (PAP), prophenoloxidase activating enzyme (PPA), cytosolic manganese superoxide dismutase (SOD) and survivin were examined to detect changes in the different reactions of the shrimp immune responses. The results indicated that rALF Pm3 is likely to affect various defense pathways. The present study suggests a potential use of rALF Pm3 in therapeutic and pharmaceutical applications in aquaculture.