Production of the major soluble antigen of Renibacterium salmoninarum in Escherichia coli K12

A DNA fragment containing all but the first 90 base pairs of gene msa encoding p57, the major soluble antigen of Renibacterium salmoninarum, was cloned in the plasmid vector pUC18 and subsequently a soluble fusion protein was produced using the pMAL expression vector system. The fusion protein retained major epitopes shared with the native p57 molecule and provided a source of protein suitable for further immunological analysis which was independent of in vitro cultures of this slow growing organism. Antiserum raised against the purified fusion protein was used to probe Western blots of cell extracts and extracellular products derived from R. salmoninarum cultured in vitro. The results show that under conditions of iron-restriction, both the production and processing of p57 are reduced.