Expression of Antibody Fragments in Pichia pastoris

Since the advent of hybridoma technology 25 years ago, monoclonal antibodies (Abs) have revolutionized many aspects of biological research and health care. After some initial setbacks, Abs are also beginning to make an impact as therapeutic agents in the clinic (1 ). In the last decade, novel selection technologies, such as phage display and ribosome display, have emerged, allowing the isolation of Abs directly from diverse repertoires of V genes (2 ). Phage display, in particular, has become a mature technology, allowing Abs with nanomolar (or even subnanomolar) affinities to be made to order against virtually any Ag, including self Ags (3 see Note 1)). Furthermore, using highthroughput technologies, such as robotics and array screening, a multitude of Abs against a given Ag (or mixtures thereof) can now be isolated simultaneously, greatly increasing the options for assay or drug development (see Note 2 ).