Submitted to: Virology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/15/2008
Publication Date: 12/1/2008
Citation: Holinka-Patterson, L.G., Fernandez-Sainz, I., O'Donnell, V., Prarat, M.V., Gladue, D.P., Lu, Z., Risatti, G., Borca, M.V. 2008. Development of a live attenuated antigenic marker classical swine fever vaccine. Virology. 384:106-113. Interpretive Summary: Classical Swine Fever (CSF) is a highly contagious disease affecting swine worldwide caused by a virus (CSFV). Current commercial vaccines are very effective but vaccinated animals cannot be discriminated from others that suffered infection with wild type viruses. Marker vaccines induce an antibody response that can be differentiated from that induced by the natural infection and, therefore, could be promising tools for disease control. Here, we report the rational development of an experimental live attenuated CSFV strain harboring a double antigenic marker. The strain, named FlagT4 virus (FlagT4v), is completely attenuated in swine but confers protection against challenge with wild type virus as early as 2 days after administration. Furthermore, the antibody response elicited by FlagT4v can be differentiated from that induced by infection with wild type CSFV. FlagTv is an excellent candidate for development of an effective marker vaccine.
Technical Abstract: Classical Swine Fever, caused by Classical Swine Fever Virus (CSFV), is a highly contagious disease affecting swine worldwide. The two main strategies for disease control are prophylactic vaccination and non-vaccination “stamping out” policies. In a vaccination-to-live strategy, marker vaccines could be promising tools, allowing distinction between vaccinated and naturally infected swine. Here, we report the rational development of an experimental live attenuated CSFV strain carrying a double antigenic marker. FlagT4 virus (FlagT4v) was obtained by combining genetic determinants of attenuation from two CSFV Brescia strain-derived recombinant viruses: RB-C22v and T4v. The dual antigenic markers in FlagT4v consist of a positive foreign marker, the highly antigenic synthetic Flag® epitope, introduced into RB-C22v via a 19mer insertion in the E1 glycoprotein; and a negative marker derived from T4v consisting of mutated CSFV amino acid residues 830 to 834 in the structural glycoprotein E2, abolishing the highly conserved epitope recognized by monoclonal antibody WH303 (mAbWH303). Immunization of pigs with FlagT4v via nasal inoculation induced a complete sterile protection against challenge with virulent strain Brescia both at 3 and 28 days post-infection (DPI). Intramuscularly administered FlagT4v induced the same efficient protection starting at 2 DPI. Sera obtained from FlagT4v immunized pigs at 28 DPI reacted strongly against the Flag® epitope but failed to inhibit binding of mAbWH303 to a synthetic peptide representing the mAbWH303 epitope. Serology results validate the strategy of the double antigenic marker FlagT4v used here. Thus, these results constitute a proof-of-concept for rational design of a CSFV antigenically marked live attenuated virus (LAV).