In vivo selection of sFv from phage display libraries

The development of phage display technology has facilitated the development of many new and sometimes novel antibody based reagents for scientific res earch. However, present methods for selection from phase-sFv display librar ies are limited to selection against purified antigens or ex vivo cells of known origin and phenotype. Existing methods therefore preclude the isolati on of sFv against unknown molecules in their natural environment, where exp ression is complex and subject to diverse control mechanisms. Since such a complex environment is difficult to mimic in vitro, the development of an i n vivo selection procedure would greatly enhance the selection from phage d isplay antibody libraries and lead to the development of reagents against c ell surface molecules in their natural environment. This would be particula rly advantageous for isolation of sFv against vascular endothelium which ca n readily change phenotype when cultured and is believed to express molecul es in a tissue specific manner and in response to different stimuli. We des cribe here the development of an in vivo selection procedure in the mouse a nd demonstrate its potential for the selection of sFv from a phase-sFv libr ary. The target antigen for one sFv is expressed solely on the thymic endot helium, while the second, a 165-170 kDa molecule in present on both thymic endothelium and the perivascular epithelium. (C) 2000 Elsevier Science B.V. All rights reserved.