The World Health Organization reference reagent for vascular endothelial growth factor,VEGF165

Preparations of human sequence recombinant vascular endothelial growth factor-165 (VEGF₁₆₅) synthesized in Escherichia coli were formulated and lyophilized at NIBSC. Following evaluation at NIBSC, the first preparation, 01/424, has been distributed since 2002 as a NIBSC research reagent, but shows variation between ampoules in the volume and crystalline appearance of the lyophilized plug. A second preparation, 02/286, was subsequently lyophilized in a different formulation. Preparation 02/286 has now been evaluated in a collaborative study for its suitability to serve as a reference standard, and compared with preparation 01/424, by five laboratories using in vitro bioassays or immunoassays. On the basis of the results reported here, the World Health Organization (WHO) established the preparation coded 02/286 as the WHO reference reagent (RR) for human VEGF₁₆₅, with an assigned unitage of 13,000 units per ampoule. Details on ordering the WHO RR can be found at www.nibsc.ac.uk.