Production of specific antibodies against protein A fusion proteins.

The gene for Staphylococcal protein A was fused to the coding sequence of bacterial beta-galactosidase, alkaline phosphatase and human insulin-like growth factor I (IGF-I). The fusion proteins, expressed in bacteria, were purified by affinity chromatography on IgG-Sepharose and antibodies were raised in rabbits. All three fusion proteins elicited specific antibodies against both the inserted protein sequences and the protein A moiety. In the case of IGF-I, the protein A moiety in the fusion protein may act as an adjuvant since native IGF-I alone is a poor immunogen. The results suggest that the protein A fusion system can be used for efficient antibody production against peptides or proteins expressed from cloned or synthetic genes. To facilitate such gene fusions a set of optimized vectors have been constructed.