Figure 1. CHIKV structural cassette expression and VLP production, using recombinant baculoviruses.

A) Schematic representation of the CHIKV structural cassette, as it was expressed in insect cells. Shaded areas represent transmembrane domain and ss signifies signal sequences. A, F and S indicate autocatalytic, furin and signalase cleavage sites, respectively. Asterisks indicate N-glycosylation sites and the molecular mass (in kDa) of the proteins is depicted. B) CHIKV E1 and E2 expression in the Sf21 cell (C) and medium (M) fraction was analysed by WB using α-E1 and α-E2 polyclonal antibodies. VLPs were precipitated using PEG-6000 (PEG) and subsequently purified using discontinuous sucrose gradient centrifugation (Suc). C) The glycosylation status of CHIKV E1 and E2 was analysed by WB after PNGase F treatment. Ac-GFP was used as a negative control.