ORAL VACCINES: USE OF PLANTS FOR THE EXPRESSION OF the main surface antigen 1 (SAG1) of Toxoplasma gondii

SANCHEZ LOPEZ, E.; RADONIC, L.; MUNERA, J.; SANDER, V.; LOPEZ BILBAO, M.; CLEMENTE, M.

Quindío

Congreso; 15th biennial meeting on Toxoplasma Biology and Toxoplasmosis; 2019

Universidad del Quindio

There is an urgent need to develop vaccines against Toxoplasma gondii. Since the portal of entry of T. gondii is the mucosa, Toxoplasma infection is an interesting model to study the optimization of expression systems based on plants and to assess the effectiveness of oral plant-made vaccines. Here, in order to improve the expression levels of vaccine antigen expressed in plants, we evaluated the role of plant Hsp90s as carrier of the SAG1 antigen. We assayed stable transformation system of lettuce plants and transient expression of tobacco leaves by agroinfiltration to test the performance of four different constructs carrying mature SAG1 protein (SAG1m) or a B- and T-cell epitopes of SAG1 peptide fused to Nicotiana benthamiana Hsp90 (NbHsp90.3) or Arabidopsis thaliana Hsp90 (AtHsp81.2). The agroinfiltration with AtHsp81.2-SAG1HC construct produced the highest level of SAG1 expression being the AtHsp81.2-SAG1HC protein accumulation60-fold higher than AtHsp81.2-SAG1m (120 μg of AtHsp81.2-SAG1HC vs. 2 μg of AtHsp81.2-SAG1m per gram of fresh leaves). On the other hand, SAG1m yields in transgenic lettuce plants expressing AtHsp81.2-SAG1m or NbHsp90.3-SAG1m ranged from 35 to 45 μg per g of lyophilized leaves. Finally, a total of 5 positive human serum samples were able to react with the recombinant fusion proteins suggesting that the SAG1 versions fused to plant Hsp90s can be recognized by antibodies from Toxoplasma-infected humans. Our results suggest that plant Hsp90s improve the recombinant protein yields in plants and have the potential to elicit immune responses in immunization protocols.