IMB-BZ as an Inhibitor Targeting ESX-1 Secretion System to Control Mycobacterial Infection.

BACKGROUND: Resistance to anti-tuberculosis (TB) drugs is a major issue in TB control, and demands the discovery of new drugs targeting the virulence factor ESX-1. METHODS: We first established a high-throughput screen (HTS) assay for the discovery of ESX-1 secretion inhibitors. The positive hits were then evaluated for the potency of diminishing the survival of virulent mycobacteria and reducing bacterial virulence. We further investigated the probability of inducing drug resistance and the underlying mechanism using mycobacterial protein fragment complementation. RESULTS: A robust HTS assay was developed to identify small molecules that inhibit ESX-1 secretion without impairing bacterial growth in vitro. A hit named IMB-BZ specifically inhibits the secretion of CFP-10 and reduces virulence in an ESX-1-dependent manner, therefore resulting in significant reduction in intracellular and in vivo survival of mycobacteria. Blocking the CFP-10-EccCb1 interaction directly or indirectly underlies the inhibitory effect of IMB-BZ on the secretion of CFP-10. Importantly, our finding shows that the ESX-1 inhibitors pose low risk of drug resistance development by mycobacteria in vitro as compared with traditional anti-TB drugs, and exhibit high potency against chronic mycobacterial infection. CONCLUSIONS: Targeting ESX-1 may lead to the development of novel therapeutics for tuberculosis. IMB-BZ holds the potential for future development into a new anti-TB drug.

Identification of immune-associated genes involved in latent Mycobacterium marinum infection.

Tuberculosis (TB) is a high mortality infectious disease caused by Mycobacterium tuberculosis (Mtb), and often develops into latent infection. About 5～10% of latent infections turn into active tuberculosis when the host immune system becomes deficient. Therefore, exploring the latent infection mechanism of Mtb is pivotal for the prevention and treatment of tuberculosis. We first established the zebrafish latent infection model and the chronic infection model utilizing Mycobacterium marinum, which has the highly similar gene background to Mtb. Using the latent infection model, we characterized the gene expression profiles and found 462 genes expressed differentially in the latent period and chronic tuberculosis infection. These differentially expressed genes are involved in various biological processes including transcription, transcriptional regulation, organism development, and immune responses. Among them, nineteen immune-related genes were found to express differentially in the latent period. By analyzing immune related protein network, the genes in the center of the network, including Nos2b, TNFα, IL1, TNFß, TLR1, TLR2, and TLR4b, displayed significant deferential expression in latent infection and chronic infection period of zebrafish, suggesting that these genes might play an important role in controlling latent infection of Mtb. Identifying immune biomarker related to the status of tuberculosis latent infection might lead to novel strategy for diagnosis and treatment.