Reversible Mannosylation as a Covalent Binding Adjuvant Enhances Immune Responses for Porcine Circovirus Type 2 Vaccine

Capsid protein of porcine circovirus type 2 (PCV2) is an ideal subunit vaccine candidate for the postweaning multisystemic wasting syndrome. In this study, mannan-mediated targeting of PCV2(Delta Cap42-233) protein to antigen presenting cells (APCs) was investigated for the development of PCV2 vaccine. Mannan was attached to PCV2(Delta Cap42-233) protein via an acid sensitive Schiff base reaction. The mannosylated protein was endowed with the capacity to target the mannose receptor on APCs as well as the ability of controlled release of the antigen in the acidic condition of the lysosome. Finally, the immune response of mannosylated PCV2(Delta Cap42-233) protein in mice was evaluated. The mannosylated protein exhibited the ability to stimulate humoral immune response and enhance the immunity. Thus, acid-sensitive and APCs-targeting mannosylated PCV2(Delta Cap42-233) protein represents a promising candidate for the potential commercial application as an efficient vaccine against porcine circovirus.