Cellulose-Affinity Isolation of Vaccine Candidate Antigens from Transgenic Plants

Apart from tradition, the biospecific affinity isolation has become one of the most rapidly growing concerns with cellulose binding domains (CBDs), a high-capacity tag for cost-effective purifications of fusion proteins. We report here a new strategy optimized for isolation of two fusion proteins, the FGF-1 (a human functional protein) and the H5N1 (a vaccine candidate antigen) tagged with CBD were grown in transient Nicotiana benthamiana and transgenic Arabidopsis thaliana respectively. A notable fraction of the recombinant proteins was lost through plant debris pelleted from the plant-slurry made. However, this issue was resolved by adjusting tissue-to-buffer ratios with 1:10 and 1:15 in those plants respectively. Washing efficiencies were improved by agitating column beds with acidic buffer (20mM NaAc. pH 4.0) in Nicotiana and alkaline buffer (10mM Tris-base pH 8.0) in Arabidopsis. Adsorption and coupling of tagged proteins on cellulose matrices were affected by the buffer-logged resins. The column-beds, after pumping the moisture out, showed efficient in binding of antigens with almost no losses detected by immunoblot signals. The bound antigens were released efficiently from the cellulose matrices by 1% Cellobiose and 2% Triethylamine respectively. The successive purifications of these antigenic proteins with identical tags likely indicate the efficiency of the proposed strategy in providing a generic and cost-effective method to purify fusion proteins propagated in transgenic plants.