Expression in tobacco and purification of beak and feather disease virus capsid protein fused to elastin-like polypeptides

• BFDV capsid protein (CP) and truncated CP (ΔN40 CP) were transiently expressed in tobacco.
• Fusion of CP or ΔN40 CP to elastin-like polypeptides (ELPs) increased yields.
• The purification of a 26 kDa ELP by inverse transition cycling (ITC) was optimised.
• Membrane filtration ITC gave the highest recovery of ΔN40 CP-ELP fusion protein.

Psittacine beak and feather disease, caused by beak and feather disease virus (BFDV), is a threat to endangered psittacine species. There is currently no vaccine against BFDV, which necessitates the development of safe and affordable vaccine candidates. A subunit vaccine based on BFDV capsid protein (CP), the major antigenic determinant, expressed in the inexpensive and highly scalable plant expression system could satisfy these requirements. Full-length CP and a truncated CP (ΔN40 CP) were transiently expressed in tobacco (Nicotiana benthamiana) as fusions to elastin-like polypeptide (ELP). These two proteins were fused to ELPs of different lengths in order to increase expression levels and to provide a simple means of purification. The ELP fusion proteins were purified by inverse transition cycling (ITC) and it was found that a membrane filtration-based ITC method improved the recovery of ΔN40 CP-ELP51 fusion protein relative to a centrifugation-based method.