A peptide fusion to the capsid protein (CP) of Cucumber mosaic virus (CMV) was designed to express either a 17 amino acid (aa) neutralizing epitope of the Newcastle disease virus (NDV) fusion (F) protein or an eight aa neutralizing epitope of the NDV hemagglutinin-neuraminidase (HN) protein. Fusions of the F, HN and HN2 (duplicated HN epitope) were made in the internal beta H-beta I loop (motif 5) within the CMV CP. Recombinant RNA3 transcripts of the Ixora strain of CMV were inoculated on to Nicotiana benthamiana, together with CMV RNA1 and CMV RNA2. When the F and HN epitopes were placed in the internal motif, the modified virus was infectious and the HN NDV epitope was recognized by anti-NDV sera. However, in some plants, deletions of one to several of the inserted amino acids occurred. A duplication of the HN epitope rendered the virus non-viable.