Construction of Lux-based promoter-reporter platforms in mycobacterium bovis BCG for screening new anti-TB drugs

Abstract

Despite continuous efforts to combat tuberculosis (TB) in the past few decades, TB is still regarded as a major health problem worldwide since drug resistance and limited antimicrobial treatment pose potential threats to TB control. However, targeting the virulence of MTB rather than viability has thus been proposed as an alternative direction for developing new anti-TB drugs, especially for drug-resistant TB. For avirulent Mycobacterium tuberculosis (MTB) were confirmed nonviable attacked by the host immune system. This study aimed to construct a highly efficient screening system to identify anti-TB drugs by repurposing anti-viral agents with known pharmacological properties. A library of 320 anti-viral compounds and 3 anti-TB drugs were initially used to screen bactericidal/anti-virulence efficacy against MTB complex using lux-based promoter-reporter platforms in M. bovis BCG Russia. After screening, the minimum inhibitory and minimum bactericidal concentrations of sixteen selected compounds against BCG/MTB were determined using the micro-broth dilution method. As a result, six anti-viral compounds, including elvitegravir, trifluoperazine (dihydrochloride), NH125, ebselen, letrazuril, and shikonin, eliminated M. bovis BCG. Intriguingly, five out of six compounds mentioned above except elvitegravir also eradicated three strains of MTB -H37Rv, HKU14621 (MDR-MTB), and WC274 (XDR-MTB), regarding them as antimicrobials. According to RNA-sequencing transcriptome analysis, gene expression profiles of BCG Russia in response to the sixteen selected compounds from screening were analyzed, and potential drug targets of MTB (H37Rv) treated with the five antimicrobials were predicted. Another factor of importance is that four anti-viral compounds -saquinavir, saquinavir (mesylate), ST-193 (hydrochloride), and ST-193 exhibited anti-virulence activity against the MTB complex via interfering with genes expression of ideR/phoP -essential virulence factors. Finally, the cytotoxicity of sixteen anti-viral compounds selected from screening was assessed based on an LDH assay. These new findings of antimicrobials and anti-virulence agents are promising candidates for anti-TB treatment and global tuberculosis control in future.