Construction of Aeromonas salmonicida subsp. achromogenes
AsaP1-toxoid strains and study of their ability to induce immunity in Arctic char, Salvelinus alpinus L.
JOURNAL OF FISH DISEASES 2015;
38:891-900. [PMID:
25271952 DOI:
10.1111/jfd.12303]
[Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/06/2014] [Revised: 07/15/2014] [Accepted: 07/28/2014] [Indexed: 06/03/2023]
Abstract
The metalloendopeptidase AsaP1 is one of the major extracellular virulence factors of A. salmonicida subsp. achromogenes, expressed as a 37-kDa pre-pro-peptide and processed to a 19-kDa active peptide. The aim of this study was to construct mutant strains secreting an AsaP1-toxoid instead of AsaP1-wt, to study virulence of these strains and to test the potency of the AsaP1-toxoid bacterin and the recombinant AsaP1-toxoids to induce protective immunity in Arctic char. Two A. salmonicida mutants were constructed that secrete either AsaP1E294A or AsaP1Y309F . The secreted AsaP1Y309F -toxoid had weak caseinolytic activity and was processed to the 19-kDa peptide, whereas the AsaP1E294A -toxoid was found as a 37-kDa pre-pro-peptide suggesting that AsaP1 is auto-catalytically processed. The LD50 of the AsaP1Y309F -toxoid mutant in Arctic char was significantly higher than that of the corresponding wt strain, and LD50 of the AsaP1E294A -toxoid mutant was comparable with that of an AsaP1-deficient strain. Bacterin based on AsaP1Y309F -toxoid mutant provided significant protection, comparable with that induced by a commercial polyvalent furunculosis vaccine. Detoxification of AsaP1 is very hard, expensive and time consuming. Therefore, an AsaP1-toxoid-secreting mutant is more suitable than the respective wt strain for production of fish bacterins aimed to protect against atypical furunculosis.
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