Effective expression and immunogenicity analysis of HIV-1 HXB2 subtype Tat protein deleted the cysteine-rich region in E. coli
Objective Deleting the cysteine-rich region (22-37 amino acids)of HIV-1 HXB2 Tat protein(whole length is 101 amino acids) to improve its stability and expression level in E.coli and to analyze the immunogenicity of Tat protein without the cystein-rich region [Tat(△C)protein]. Methods Tat DNA deleted the cysteine-rich region (64-111 nucleotides), named as Tat(△C)DNA, was obtained in vitro by PCR and cloned into pET-32a vector. pET-32a-Tat(△C)plasmid and the pET-32a-Tat plasmid were established and transformed into E.coli BL21(DE3) strains respectively to express and purify the protein. Three rabbits were vaccinated with pET-32a-Tat(△C)protein, then testify the reactivity of sera from rabbits by ELISA and Western blot. Results The dense of the purified pET-32a-Tat(△C)protein was 7.12 mg/ml,which was greatly more than pET-32a-Tat protein(1.50 mg/ml). Dimer of pET-32a-Tat protein can be observed just after the protein purification and stored at 25℃ and 4℃ for 7 days, but dimer of pET-32a-Tat(△C)protein was not formed at the same condition. Experimental rabbits were immunized with pET-32a-Tat(△C)protein and produced high titre of anti-pET-32a-Tat(△C)serum(1∶320 000), the antibody can react specifically with Tat(△C)protein, Tat protein (1-101 AA)and synthetic Tat(1-86 AA) protein. Deletion mutation of the cysteine-rich region of Tat protein was first performed in the study. Conclusion The expression level in E.coli and the stability of Tat protein deleted the cysteine-rich region can be increased greatly, and the protein remains good immunogenicity. The results may provide a novel antigen for further development of HIV-1 Tat vaccine. 
 
Key words: 
Human immunodeficiency virus type-1;  Deletion of cysteine-rich region;  Tat protein