In vitro assembly of chimeric virus-like particles composed of a porcine circovirus 2b capsid protein and a B-cell epitope of infectious bursal disease virus.

Objectives: To develop a method for in vitro assembly of recombinant proteins expressed in E. coli into chimeric virus-like particles (cVLPs).

Results: A fusion protein (Bepi-Cap-A) between capsid protein (Cap) of PCV2b and B cell epitope (Bepi) of IBDV was expressed in E. Coli, and purified. For assembling them into cVLPs (Bepi-Cap-VLP), the Bepi-Cap-A was suspended in buffer C [0.03% ("%" stands for "v/v" unless otherwise indicated) polyethylene glycol, 0.4 M Tris, 10 mM β-mercaptoethanol, 5% glycerol, 0.02% (w/v) gellan gum, 0.1 M glycine, 0.03% Tween 80, 500 mM NaCl], and incubated. After centrifugation, the pellet was resuspended in buffer D [50 mM NaHPO, 50 mM NaHPO, 0.01% (w/v) gellan gum, 0.05 mM EDTA, 500 mM NaCl, 0.03% Tween 80, pH 6.5], and then dialyzed against dialysis buffer (50 mM NaHPO, 50 mM NaHPO, 500 mM NaCl, 0.03% Tween 80, pH 6.5). The procedure resulted in typical and immunogenic Bepi-Cap-VLP.

Conclusions: The data provide a method which is feasible for in vitro assembly of recombinant proteins into chimeric virus-like particles.