Single chain Fv antibody fragments have been selected from a synthetic
phage-antibody library following three and four rounds of affinity se
lection with purified potato virus Y, common strain (PVYo). The select
ed fragments were highly specific for PVY and detected seven out of ni
ne isolates of PVYo whilst failing to detect three isolates of PVYN an
d 12 isolates of PVYNTN. Nucleotide sequence of the scFv genes showed
the variable heavy fragments belonged to the human VH4 family, whilst
the variable light fragments belonged to the V lambda 1 family. The fr
agments were used in ELISA to detect virus at concentrations of 50 ng/
ml in plant sap and in comparisons with commercially available PVY mon
oclonal antibodies were shown to have similar limits of detection. Thi
s is the first report of the selection of a scFv specific for a member
of the potyviridae, and its use in detecting and differentiating stra
ins of PVY in infected plant sap. The results highlight the potential
of the technology for the selection of strain specific antibodies with
an avidity equivalent to traditional monoclonal antibodies raised aga
inst viral pathogens and their use for viral diagnosis. (C) 1998 Elsev
ier Science B.V. All rights reserved.