Rapid pathotyping of Newcastle disease virus using a single-chain Fv displayed on phage against the C-terminal end of the F2 polypeptide

Summary.

 Filamentous bacteriophage display technology has been used to generate specific antibody fragments for differentiating virulent and avirulent Newcastle disease virus. A single-chain Fv fragment to the motif ¹¹²RRQ¹¹⁴, present at the F2 C-terminal end of many virulent Newcastle disease virus isolates, was isolated from a phage display library derived from a rabbit immunized with a peptide conjugate. An ELISA evaluation was carried out to test its ability to differentiate between 11 avirulent and 34 virulent NDV isolates. The antibody fragment reacted with 25/28 virulent viruses with the putative motif ¹¹²RRQ¹¹⁴. The three exceptions were viruses with an arginine instead of glycine, at position 110 of the fusion protein, just preceding the cleavage site. Five of six virulent isolates, whose predicted motif was different from that usually found in virulent strains, also tested negative. However, the antibody did react with one isolate with the motif ¹¹²KRQ¹¹⁴. There was no apparent reactivity with any of the avirulent isolates tested. We conclude that this antibody may, in the future, be a useful aid for the pathotyping of NDV isolates.