Presentation of epitope sequences from foreign viruses on the surface of apple latent spherical virus particles.

Apple latent spherical virus (ALSV) has small isometric particles that are comprised of two single-stranded RNA species (RNA1 and RNA2) and three capsid proteins (Vp25, Vp20, and Vp24). We constructed ALSV vectors for presenting foreign peptides on the surface of virus particles. In these vectors, peptides can be fused to either of two C-terminal regions of Vp20 (amino acid positions between G171 and P172 or between P172 and L173) or the C-terminus (T192) of Vp24. An ALSV vector presenting the epitope sequences of the coat protein (CP) of zucchini yellow mosaic virus (ZYMV) could systemically infect host plants and was specifically recognized by antiserum against ZYMV by ELISA, immunoelectron microscopy, and immunoblotting. RT-PCR showed that the epitope sequences up to 20 amino acids were stably maintained in the chimeric ALSV for more than 10 serial passages and at least six months. Purified chimeric ALSV particles induced an immune response and the production of antibodies against ZYMV-CP in rabbits. The ALSV vector was also used for expression of an epitope from VP1 of foot-and-mouth disease virus.