Plant viruses show great potential for production of pharmaceuticals in plants. Such viruses can harbor a small antigenic, peptide(s) as a part of their coat proteins (CP) and elicit an antigen-specific immune response. Here, we report the high yield and consistency in production of recombinant alfalfa mosaic virus (A1MV) particles for specific presentation of the small loop 15 amino acid epitope from domain-4 of the Bacillus anthracis protective antigen (PA-D4s). The epitope was inserted immediately after the first 25 N-terminal amino acids of A1MV CP to retain genome activation and binding of CP to viral RNAs. Recombinant A1MV particles were efficiently produced in tobacco, easily purified for immunological analysis, and exhibited extended stability and systemic proliferation in planta. Intraperitional injections of mice with recombinant plant virus particles harboring the PA-D4s epitope elicited a distinct immune response. Western blotting and ELISA analysis showed that sera from immunized mice recognized both native PA antigen and the A1MV CP. (c) 2005 Elsevier Inc. All rights reserved.