Antigen purification

A method for purifying at least one antigen harvested from a source organism, comprising:

• extracting cellular debris from the at least one antigen by adding an extraction buffer to an extract at a ratio of the extraction buffer and the extract expressed as extraction buffer:extract by wt;
• after the extracting step, concentrating the at least one antigen by passing the at least one antigen through a tangential flow filtration apparatus;
• and
• performing separations comprising sub-steps of separating host cell contaminants from the at least one antigen, subjecting the at least one antigen to affinity chromatography to elute the at least one antigen, and after the separating host cell contaminants and affinity chromatograph sub-steps, subjecting the at least one antigen to multi-modal chromatography to separate residual impurities from the at least one antigen.