Functional Improvement of Human Cardiotrophin 1 Produced in Tobacco Chloroplasts by Co-Expression with Plastid Thioredoxin m

Human cardiotrophin 1 (CT1), a cytokine with excellent therapeutic potential, was previously expressed in tobacco chloroplasts. However, the growth conditions required to reach the highest expression levels resulted in an impairment of its bioactivity. In the present study, we have examined new strategies to modulate the expression of this recombinant protein in chloroplasts so as to enhance its production and bioactivity. In particular, we assessed the effect of both the fusion and co-expression of Trx m with CT1 on the production of a functional CT1 by using plastid transformation. Our data revealed that the Trx m fusion strategy was useful to increase the expression levels of CT1 inside the chloroplasts, although CT1 bioactivity was significantly impaired, and this was likely due to steric hindrance between both proteins. By contrast, the expression of functional CT1 was increased when co-expressed with Trx m, because we demonstrated that recombinant CT1 was functionally active during an in vitro signaling assay. While Trx m/CT1 co-expression did not increase the amount of CT1 in young leaves, our results revealed an increase in CT1 protein stability as the leaves aged in this genotype, which also improved the recombinant protein’s overall production. This strategy might be useful to produce other functional biopharmaceuticals in chloroplasts

The vaccine adjuvant extra domain A from fibronectin retains its proinflammatory properties when expressed in tobacco chloroplasts

We previously showed that recombinant extra domain A from fibronectin (EDA) purified from Escherichia coli was able to bind to toll-like receptor 4 (TLR4) and stimulate production of proinflammatory cytokines by dendritic cells. Because EDA could be used as an adjuvant for vaccine development, we aimed to express it from the tobacco plastome, a promising strategy in molecular farming. To optimize the amount of recombinant EDA (rEDA) in tobacco leaves, different downstream sequences were evaluated as potential fusion tags. Plants generated by tobacco plastid transformation accumulated rEDA at levels up to 2% of the total cellular protein (equivalent to approximately 0.3 mg/g fresh weight) when translationally fused to the first 15 amino acids of green fluorescence protein (GFP). The recombinant adjuvant could be purified from tobacco leaves using a simple procedure, involving ammonium sulfate precipitation and anion exchange chromatography. Purified protein was able to induce production of tumour necrosis factor-alpha (TNF-alpha) either by bone marrow-derived dendritic cells or THP-1 monocytes. The rEDA produced in tobacco leaves was also able to induce upregulation of CD54 and CD86 maturation markers on dendritic cells, suggesting that the rEDA retains the proinflammatory properties of the EDA produced in E. coli and thus could be used as an adjuvant in vaccination against infectious agents and cancer. Taken together, these results demonstrate that chloroplasts are an attractive production vehicle for the expression of this protein vaccine adjuvant

Functional Improvement of Human Cardiotrophin 1 Produced in Tobacco Chloroplasts by Co-Expression with Plastid Thioredoxin m

Human cardiotrophin 1 (CT1), a cytokine with excellent therapeutic potential, was previously expressed in tobacco chloroplasts. However, the growth conditions required to reach the highest expression levels resulted in an impairment of its bioactivity. In the present study, we have examined new strategies to modulate the expression of this recombinant protein in chloroplasts so as to enhance its production and bioactivity. In particular, we assessed the effect of both the fusion and co-expression of Trx m with CT1 on the production of a functional CT1 by using plastid transformation. Our data revealed that the Trx m fusion strategy was useful to increase the expression levels of CT1 inside the chloroplasts, although CT1 bioactivity was significantly impaired, and this was likely due to steric hindrance between both proteins. By contrast, the expression of functional CT1 was increased when co-expressed with Trx m, because we demonstrated that recombinant CT1 was functionally active during an in vitro signaling assay. While Trx m/CT1 co-expression did not increase the amount of CT1 in young leaves, our results revealed an increase in CT1 protein stability as the leaves aged in this genotype, which also improved the recombinant protein’s overall production. This strategy might be useful to produce other functional biopharmaceuticals in chloroplasts