Immunogenicity of T7 bacteriophage nanoparticles displaying G-H loop of foot-and-mouth disease virus (FMDV)

Foot-and-mouth disease (FMD) is a highly contagious disease of cloven-hoofed animals that causes severe economic losses worldwide. The G-H loop of the FMDV VP1 structural protein is the major neutralizing antigenic site. However, a fully protective G-H loop peptide vaccine requires the addition of promiscuous Th sites from a source outside VP1. Thus, we demonstrated the potential of T7 bacteriophage based nanoparticles displaying a genetically fused G-H loop peptide (T7-GH) as a FMDV vaccine candidate. Recombinant T7-GH phage was constructed by inserting the G-H loop coding region into the T7 Select 415-1b vector. Purified T7-GH phage nanoparticles were analyzed by SDS-PAGE, Western blot and Dot-ELISA. Pigs seronegative for FMDV exposure were immunized with T7-GH nanoparticles along with the adjuvant Montanide ISA206, and two commercially available FMDV vaccines (InactVac and PepVac). Humoral and cellular immune responses, as well as protection against virulent homologous virus challenge were assessed following single dose immunization. Pigs immunized T7-GH developed comparable anti-VP1 antibody titers to PepVac, although lower LPBE titers than was induced by InactVac. Antigen specific lymphocyte proliferation was detected in T7-GH group similar to that of PepVac group, however, weaker than InactVac group. Pigs immunized with T7-GH developed a neutralizing antibody response stronger than PepVac, but weaker than InactVac. Furthermore, 80% (4/5) of T7-GH immunized pigs were protected from challenge with virulent homologous virus. These findings demonstrate that the T7-GH phage nanoparticles were effective in eliciting antigen specific immune responses in pigs, highlighting the value of such an approach in the research and development of FMDV vaccines.