Expression of VHHs in Saccharomyces cerevisiae.

The production of VHHs in microorganisms is relatively straightforward, however the amount of VHH produced per volume unit can vary substantially from hardly detectable to hundreds of milligrams per liter. Expression in Escherichia coli is more commonly used at initial research phase, since production of VHHs for large-scale application in E. coli is for a number of reasons not preferred. Otherwise VHH production in GRAS organisms such as Saccharomyces cerevisiae fits very well with industrial fermentation processes, and in fact the only commercially available VHHs are produced in S. cerevisiae. Immediately after the discovery of heavy chain only antibodies, which are per definition devoid of light chains, it was investigated whether many problems encountered with the production of conventional antibodies in lower eukaryotes were absent during the production of VHHs. Here we provide a protocol for the expression of VHH genes in S. cerevisiae in a fed-batch fermentation process. This protocol is also suitable for the production of multivalent VHHs.