Plasma membrane display of anti-viral single chain Fv fragments confers resistance to tobacco mosaic virus.

We tested the hypothesis that membrane-anchored anti-viral antibodies can confer viral resistance to transgenic plants. A heterologous expression system was developed for plasma membrane targeting of anti-viral antibodies using mammalian transmembrane domains. A tobacco mosaic virus (TMV) neutralizing single-chain Fv antibody fragment (scFv24) was targeted to the endoplasmic reticulum and integrated into the plasma membrane of tobacco cells, using mammalian signal peptides and membrane receptor transmembrane domains. The human platelet-derived growth factor receptor (PDGFR) transmembrane domain or the T-cell receptor β-domain (TcRβ) transmembrane domain was fused to the C-terminus of TMV-specific scFv24 to target expression of scFv24 as an extracellularly facing plasma membrane protein. Western blot and ELISA analyses were carried out to confirm functional expression of the recombinant fusion proteins scFv24-PDGFR and scFv24-TcRβ in transgenic tobacco suspension cultures and transgenic plants. Immunofluorescence and electron microscopy showed that the TcRβ transmembrane domain targeted scFv24 to the tobacco plasma membrane. Bioassays of viral infection showed that transgenic tobacco plants expressing scFv24-TcRβ were resistant to TMV infection. These results demonstrated that membrane anchored anti-viral antibody fragments are functional, can be targeted to the plasma membrane in planta and are a novel approach for engineering disease-resistant crops. [ABSTRACT FROM AUTHOR]