Development of an enzyme-linked immunosorbent assay for staphylococcal protein A produced in Escherichia coli by pUC8 based plasmids containing the Staphylococcus aureus Cowan I protein A gene.

Staphylococcal protein A, a cell wall component of several strains of Staphylococcus aureus has found many uses as a research tool, as a diagnostic reagent and even as a possible therapeutic agent in cancer. These uses have arisen exclusively out of its almost unique property of binding specifically to the Fc region of many immunoglobulin molecules. As Staphylococcus aureus is pathogenic, it has been desirable for industrial purposes to clone the gene coding for protein A into Escherichia coli and to develop a sensitive assay free from interference by bacterial components. We describe an ELISA assay which is capable of detecting staphylococcal protein A in bacterial lysates at levels as low as 1.0 ng/ml and which is free of interference from lysozyme, lysostaphin, endogenous peroxidases or other bacterial antigens.