ERAP1 and infection: To investigate the relative contribution of the polymorphic positions 349 and 725 to the unusual functions of ERAP1 allotype 10, we used site-directed mutagenesis to generate ERAP1 allotype 10 variants V349M and Q725R as well as the double variant V349M Q725R, expressed the recombinant proteins in insect cells after infection with the appropriate recombinant baculovirus, and purified them by affinity chromatography as described in the “Materials and methods” section.