Antigen purification process for pertactin antigen

A process for purifying Bordetella pertussis p69 antigen from a Bordetella pertussis culture, comprising steps of:

• (a) separating p69 antigen containing cellular solids from supernatant liquid in the Bordetella pertussis culture, (b) treating the p69 antigen containing cellular solids to obtain a p69 antigen containing liquid;
• (c) contacting the p69 antigen containing liquid with a support comprising an immobilised metal ion, to give an eluate and a p69-containing retentate;
• (d) eluting p69 from the retentate;
• and (e) further purifying the eluate obtained by step (d) by hydrophobic interaction chromatography and anion exchange chromatography to provide purified p69, wherein the p69 does not comprise a hexa-histidine amino acid sequence tag.