Enhancement of Expression Level of Modified t-PA (TNKase) in Leishmania tarentolae by Induction System

Background: The expression of bio-therapeutic proteins in mammalian cells, such as CHO, attains high homogeneity related to post-translational modifications. Although CHO remains the most popular cell line for bestselling biotherapeutic proteins on the market, there are still drawbacks such as expensive culture media, long time line, and high drug cost. Recently, researches on a novel Leishmania protozoan system have confirmed that this low-level eukaryote could represent a competitive alternative to the mammalian cell lines. Methods: The full length of coding sequence of modified tPA TNKase (tenecteplase) was synthesized and cloned into an inducible expression vector of L. tarentolae T7-TR cells. Results: The expression of the construct was driven by a Tet-inducible promoter. A Leishmania secretory signal sequence was also added to the expression cassette to facilitate the release of the recombinant protein into the medium. The secretory recombinant protein was analyzed and confirmed by SDS-PAGE and Western blot analyses. The expression level of TNKase in this novel system of L. tarentolae was 810 IU/mL after induction, which means that the percentage of expression increases two times compared to previous models in L. tarentolae. The TNKase activity was comparable with Activase. Conclusion: Our results suggested that expressed TNK (modified tPA) is functionally compatible with Activase regarding their effect on fibrinolysis. Given the post-translational modification similarities between mammalian and L. tarentolae, it is speculated that this system is capable of producing complex proteins such as tPA similar to mammalian system, with easier manipulation and non-expensive method.

Evaluation of HTLV-1 activity in HAM/TSP patients using proviral load and Tax mRNA expression after In Vitro lymphocyte activation.

OBJECTIVES: HTLV-1 is the first human retrovirus that has been recognized and is associated with HAM/TSP and ATLL. Studies have shown that less than five percent of HTLV-1 infected carriers develop HAM/TSP or ATLL and about ninety-five percent remain asymptomatic. Therefore, the proviral load with Tax may affect cellular genes such as cytokines and oncogenes, as well as involve in pathogenicity. MATERIALS AND METHODS: Thirty HAM/TSP patients, thirty HTLV-1 healthy carriers, and MT-2 cell line were evaluated for HTLV-1 activity. PBMCs were isolated and activated using PMA and ionomycine. Real-time PCR and TaqMan methods were performed using specific primers and fluorescence probes for Tax expression and proviral load assessment. B2microglobulin (ß2m) and albumin were used as controls in Tax expression and in proviral load, respectively. RESULTS: An insignificant increase in Tax expression was observed in rest PBMCs of HAM/TSP patients compared to healthy carriers. However, after lymphocyte activation there was a significant increase in Tax expression in HAM/TSP patients (P=0.042). The Proviral load in patients was significantly higher than in carriers. Moreover, there was a significant correlation between Tax mRNA expression in activated PBMCs and proviral load (R=0.37, P=0.012). CONCLUSION: Although proviral load had been addressed as a valuable index for monitoring HTLV-1 infected subjects, the results of this study demonstrated that Tax expression in activated PBMCs along with proviral load assessment in HAM/TSP patients are a more reliable factor for determining the prognosis and monitoring healthy carriers and HAM/TSP patients.