Induced heat shock protein production protects Artemia against vibriosis

In this thesis, the effects of heat shock protein (Hsp) 70s and their inducers to control vibriosis were determined using Artemia franciscana as model organism. Results showed that feeding recombinant Artemia Hsp70 or E. coli DnaK protein (both has a high degree of structural conservation) protected Vibrio-challenged Artemia to a similar extent. Comparison of the peptide sequence of the two proteins showed a large degree of homology, especially in the peptide-binding domain (PBD) suggesting that the protective capacity of these Hsp70s might reside within this domain. Artemia fed with these Hsp70s and challenged with V. campbellii had enhanced prophenoloxidase (proPO) expression and activity levels, suggesting that Artemia were primed against Vibrio by Hsp70s. The assumption that the protective capacity of the Hsp70s resides within their PBD was also verified. Results showed that the C-terminal end (containing the PBD) of Artemia Hsp70 or DnaK is required for Hsp70-mediated protection of Vibrio-challenged Artemia. It was also observed that when Artemia were challenged with V. campbellii, prior feeding of the truncated Hsp70s significantly enhanced the proPO expression and activity levels, indicating that the epitope responsible for priming the proPO system, consequently boosting Artemia survival, might be located within this domain. In a further study, an extract from the prickly pear fruit Opuntia ficus indica named Pro-Tex® (containing the active molecule Tex-OE®), an Hsp inducer, was tested for its protective ability against abiotic and biotic stressors. Artemia pretreated with Tex-OE® (152 ppb) for 1 h accumulated endogenous Hsp70 and exhibited enhanced survival when subjected to thermal, hyperosmotic or Vibrio challenge. Tex-OE® pretreatment elicited the proPO at both mRNA and protein activity levels, and also induced nitric oxide level, indicating that Tex-OE® is undoubtedly beneficial for eliciting protective immunity in Artemia against V. campbellii and thus can potentially be a useful preventive treatment modality for vibrios