Patent ID: 8680018

Claim:
A method for helper phage rescue of a phagemid comprising a fusion polypeptide to form progeny phage, wherein: (a) the helper phage encodes a viral coat protein comprising a protease-sensitive cleavage site; wherein the helper phage is a filamentous bacteriophage M13, fd or related species; wherein the viral coat protein is encoded by gene 3 of the filamentous bacteriophage M13, fd or related species; and wherein the protease-sensitive cleavage site is introduced between the second and third domain of the gene 3 protein; (b) the phagemid encoding a fusion polypeptide; wherein the sequence encoding the fusion polypeptides is fused to a sequence encoding a viral coat protein; and wherein the viral coat protein is encoded by gene 3 of the filamentous bacteriophage M13, fd or related species; (c) the progeny phage are exposed to trypsin capable of cleaving the protease-cleavable site, such that the cleavage of the protein encoded by gene 3 derived from the helper phage impairs the phage's ability to mediate infection, and (d) the phage progeny are propagated by infection in bacteria.