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An efficient fermentation method for the production of two modified recombinant Pseudomonas aeruginosa exotoxin As cloned in Escherichia coli BL21(lambda DE3) was developed. Cell densities of 16-30 g dry weight/1 were found to be most suitable for the induction of protein synthesis, which was under the isopropyl beta-D-thiogalactopyranoside (IPTG)-inducible T7 expression system. A concentration of 0.6 mM IPTG and induction time of 90 min were found to give the best results for production of the modified toxins. Using this procedure, gram amounts of the proteins were obtained in a 3-1 bench-top fermentor. The high density growth of the bacteria did not impair the integrity of the proteins and did not interfere with the purification procedure.

Melittin, a bee venom peptide consisting of 26 amino acid residues, elicited high IgG and IgE antibody responses in mice of BALB/c and CAF1 strains, but not in mice of A/J, AKR, and C57BL/6 strains. Greater than 80% of the melittin-specific antibodies in sera of responder mice were found to bind the hydrophilic carboxyl-terminal heptapeptide of melittin. Three melittin-specific monoclonal antibodies were obtained from responder mice by the hybridoma technique. Two are of the IgG1 isotype and one is of the IgE isotype. One monoclonal antibody of the IgG1 isotype binds the carboxyl-terminal heptapeptide of melittin, while the other two monoclonal antibodies do not. However, competitive binding studies suggest that all three monoclonal Ig bind at the same, or adjacent, site of melittin. These findings, together with the known amphiphilic property of melittin, suggest that the immunogenicity of this peptide is a consequence of its binding to cell surface phospholipids.