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.

Identification of the serotypes of bacterial meningitis agents; implication for vaccine usage.

BACKGROUND AND OBJECTIVES: Bacterial meningitis is one of the most serious infections and should be treated as emergency. As it has significant morbidity and mortality throughout the world, every country should have precise information regarding the etiological agents of disease and populations at risk to design public health prevention strategy. In the present study in addition of evaluation of common etiological agents (Haemophilus influenzae, Neisseria meningitidis, and Streptococcus pneumoniae) in bacterial meningitis cases, we sero-grouped or serotyped the obtained agents in order to predict the usefulness of existing vaccines against bacterial meningitis. MATERIALS AND METHODS: Cerebrospinal fluid of 182 suspected meningitis patients were collected, from which 114 cases were approved by biochemical, microbiological and molecular tests as bacterial meningitis. The isolated bacteria were serogrouped or serotyped to determine the dominant serotypes. RESULTS: Streptococcus pneumoniae accounted for 36%, Haemophilus influenza for 26% and Neisseria meningitidis for 14% of cases. From 13 serogroups of N. meningitides the most frequent serogroups, were meningococcus group B (51%), C(24%) A (18%), Z(2%), W135 (1%) and 3% was not identified. In H. influenzae group only serotype b (100%) have been identified and in pneumococcal meningitis the most common serotype among our cases were 18C (44%) followed by14 (17%), 19A (13%), 6A (9%), 7F (4%), 4(3%), 3 (3%), 9V (2%), 8 (2%), 23f (2%), 5 (1%). CONCLUSION: Since there is no nationwide mass immunization program for common agents of bacterial meningitis in Iran, the result of this study can be used to improve the existing vaccines to cover the detected serotypes and consequently reduce the incidence of bacterial meningitis.