Protection of Artemia from vibriosis by heat shock and heat shock proteins
Disease imposes an important constraint on aquaculture and in this context vibriosis brings about massive mortalities in many commercial species, ranging from fish to shrimp, with resultant heavy monetary losses. During my work the application of heat shock proteins (Hsps) as an approach to disease control in aquaculture was explored, with gnotobiotic brine shrimp Artemia larvae as the model organism. The thesis contains several findings, featuring the interesting observation that a non-lethal heat shock at 37°C for 30 min followed by a 6 h recovery period and a combined hypothermic/hyperthermic shock with temperature reduction from 28°C to 4°C for 1 h followed by incubation at 37°C for 30 min and a 6 h recovery at ambient temperature optimally enhanced resistance of gnotobiotic Artemia larvae against pathogenic vibrios and induced Hsp70 maximally. The resulting two-fold increase in survival of larvae in concert with stress protein synthesis suggested that endogenous Hsp70 functions in protection. Likewise, feeding gnotobiotic Artemia with E. coli cells over-producing prokaryotic heat shock proteins, particularly the 70kDa DnaK, promotes resistance to infection by a pathogenic bacterium. This study demonstrates for the first time that Hsp70 homologs can induce a protective effect towards a pathogen when it is supplied via the feed to the host, perhaps via immune enhancement. Importantly, this work reveals the potential application of Hsps as a way to enhance shrimp resistance and as a novel microbial countermeasure to infection. These techniques represent efficient strategies to control Vibrio infection in brine shrimp and may serve as alternatives to antibiotic use in aquaculture. Moreover, we provide new evidence for relationships between Hsps and immunity in Artemia.
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