Construction and application of a yeast expression system for thymosin α1

We want to construct a yeast expression system for thymosin alpha 1 (T alpha 1) to make the orally administered Tat preparation possible. The whole Tat DNA fragment was obtained by PCR. After being digested with restriction enzymes, it was cloned into pYES2 vector. Sequencing was performed to identify the recombinant. The sequence of T alpha 1 in recombinant coincided with the original one reported in Genbank. When pYES2-T alpha 1 plasmid was transformed into yeast, galactose instead of glucose was used to induce T alpha 1 expression. Western blot was performed to identify the quality of the expressed T alpha 1. Dried yeast containing pYEST2-T alpha 1 was fed to Balb/c mice whose immunities were inhibited by cyclophosphamide in advance. Synthesized Tal peptide was used as positive control and empty yeast was used as negative control. Compared with the negative control group. both dried yeast containing pYEST2-T alpha 1 and synthesized T alpha 1 peptide can significantly increase the CD8+ level (22.74 +/- 1.09 and 18.77 +/- 4.72 vs 7.49 +/- 2.14,p < 0.01), while both of them had little effect on the CD4+ lymphocytes (61.86 +/- 6.94 and 65.91 +/- 4.78 vs 57.93 +/- 10.40,p > 0.05). We concluded that a high effective yeast expression system for T alpha 1 was constructed successfully and the T alpha 1 protein expressed by this system can improve CD8+ level in immune inhibited mice.