Production of Escherichia coli-based virus-like particle vaccine against porcine circovirus type 2 challenge in piglets: Structure characterization and protective efficacy validation

• Soluble non-tag full-length PCV2 capsid protein (rCap) was produced in Escherichia coli and self-assembled into VLP in vitro.
• The Cryo-EM structure of PCV2 rCap VLP was determined to 4.5 Å resolution.
• PCV2 rCap VLP-based vaccine displayed strong protective efficacy against PCV2 challenge as a commercial vaccine.

We report the strategies leading to the large-production of soluble non-tag full-length porcine circovirus type 2 (PCV2) Cap protein in Escherichia coli. Under neutral pH condition, the purified recombinant Cap protein derived from E. coli expression self-assembles into homogenous round virus-like particle at the similar size of that of the intact PCV2 virus, which is further characterized by Cryo-EM single particle structure determined at 4.5 Å. The engineered PCV2 rCap VLP was tested as a subunit vaccine for the protective efficacy against PCV2 challenge on 3-week old piglets. Similar to commercial available PCV2 vaccine, the Cap VLP-immunized piglets developed specific antibody-mediated response and were protected from the virulent SH PCV2 strain challenge. Hence, the production of E. coli based PCV2Cap-VLP could be applied as a cost-friendly and effective subunit vaccine to control PCV2 spreading in developing countries.