Expression of Thanatin in HEK293 Cells and Investigation of its 
Antibacterial Effects on Some Human Pathogens

BACKGROUND: Thanatin is the smallest member of Beta-hairpin class of cationic peptide derived from insects with vast activities against various pathogens. OBJECTIVE: In this study, the antimicrobial activity of this peptide against some species of human bacterial pathogens as well as its toxicity on NIH cells were evaluated. METHODS: Thanatin DNA sequence was cloned into pcDNA3.1+ vector and transformed into a DH5α bacterial strain. Then the recombinant plasmids were transfected into HEK-293 cells by calcium phosphate co-precipitation. After applying antibiotic treatment, the supernatant medium containing thanatin was collected. The peptide quantity was estimated by SDS-PAGE and GelQuant software. The antimicrobial activity of this peptide was performed with Minimum Inhibitory Concentration (MIC) method. In addition, its toxicity on NIH cells were evaluated by MTT assay. RESULTS: The peptide quantity was estimated approximately 164.21 μmolL(-1). The antibacterial activity of thanatin was estimated between 0.99 and 31.58 μmolL(-1) using MIC method. The result of cytotoxicity test on NIH cell line showed that the peptide toxicity up to the concentration of 394.10 μmolL(-1) and for 48 hours, was not statistically significant from negative control cells (P>0.05). The antimicrobial assay demonstrated that thanatin had an antibacterial effect on some tested microorganisms. The results obtained in this study also showed that thanatin had no toxicity on mammalian cell lines including HEK293 and NIH. CONCLUSION: Antimicrobial peptides such as thanatin are considered to be appropriate alternatives to conventional antibiotics in treating various human pathological diseases bacteria.