In vitro activities of small peptides from snake venom against clinical isolates of drug-resistant Mycobacterium tuberculosis

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Abstract

The recent re-emergence of tuberculosis, especially the multidrug-resistant cases, has highlighted the importance of screening effective novel drugs against Mycobacterium tuberculosis. In this study, the in vitro activities of small peptides isolated from snake venom were investigated against multidrug-resistant M. tuberculosis. Minimum inhibitory concentrations (MICs) were determined by the Bactec TB-460 radiometric method. A small peptide with the amino acid sequence ECYRKSDIVTCEPWQKFCYREVTFFPNHPVYLSGCASECTETNSKWCCTTDKCNRARGG (designated as vgf-1) from Naja atra (isolated from Yunnan province of China) venom had in vitro activity against clinically isolated multidrug-resistant strains of M. tuberculosis. The MIC was 8.5 mg/l. The antimycobacterial domain of this 60aa peptide is under investigation.

Introduction

The increasing incidence of tuberculosis in immunocompromised people and the emergence of multidrug-resistant strains have emphasized the urgent need to develop novel antimycobacterial agents. At least 2% of tuberculosis is caused by multidrug-resistant Mycobacterium tuberculosis (MDR-TB) [1], [2]. The cure rate of MDR-TB is reduced to less than 60% compared with nearly 100% for pan-sensitive strains [1]. Greater efforts are needed to develop high-efficacy drugs against M. tuberculosis, especially those readily and simply produced from some natural source. To our knowledge, there are no reports on the activity of snake toxin components against M. tuberculosis and clinically isolated MDR-TB.

Snake venom are rich in biologically active components. In this report, several components from Naja atra snake venom were screened for activity against MDR-TB.

Section snippets

Sample preparation

Fractions to be studied were obtained by ion exchange chromatography of snake venom and high-performance liquid chromatography (HPLC) using the method of Sun et al. [3]. Briefly, 3 g of the lyophilized N. atra crude venom from South Yunnan, China, was dissolved in 20 ml of sodium acetate buffer (0.05 mol/l, pH 6.0). The solution was applied to a SP-Sephadex-C-25 column (2.6 cm×50 cm) equilibrated with the same buffer. Pooled fractions were dialyzed against sodium phosphate buffer (0.01 mol/l,

Results

The activities of the small peptide vgf-1 from snake venom against MDR-TB were determined using the Bactec radiometric methodology in 7H12 broth. The MIC values are summarized in Table 1. The vgf-1 showed activity against drug-resistant M. tuberculosis and MDR-TB. Cultures from Bactec vials were also plated for viable count determination at both the start and at the end of the experiments for all tests. There is a good correlation between MICs obtained in 7H12 broth and viable counts.

Identical

Discussion

Natural products such as plant-derived molecules have been previously reported as antimycobacterial agents [4], [5]. Small peptides, such as the 9-kDa granulysin, a peptide belonging to the saposin-like protein family, which occurs in the granules of human cytotoxic T-lymphocyte and natural killer cell, shows antimycobacterial activity [6] and the antimycobacterial functional domain contains a disulphide bond consisting of 22–29 amino acid residues [7], [8]. Small natural anti-bacterial

Acknowledgements

We are grateful to Zhou Bonian, Xiao Heping and Jin Anjia of Shanghai Pulmonary Hospital for their kind help during the study. The study was funded by the National 10th Five-year Key Project (2001DA705D03).

References (10)

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