Use of siRNA molecular beacons to detect and attenuate mycobacterial infection in macrophages

Tuberculosis in the 21th century: Current status of diagnostic methods

Tuberculosis is an infectious bacterial disease with a high mortality rate worldwide constituting a serious public health problem. The diagnostic methods commonly used by health professionals are slow and expensive and the results may take about sixty days which will cause a delay in administrating the most proper treatment to the patient, as well as increase health care costs and infection transmission possibility. Patients infected simultaneously with human immunodeficiency virus and Mycobacterium tuberculosis are a constant and worrying challenge for the scientific community which will research and develop new methods of diagnosis, new drugs and new therapies. Nowadays there are new tuberculosis diagnosis methods and some of which are already in clinical trial phases. These methods have high sensitivity, but do not replace the microbiological examination for isolation and culture of Mycobacterium spp. However, in clinical practice, microbiological, imaging, clinical and epidemiological data integration provide the best diagnosis and treatment possible. Consequently, throughout this paper, the different methods of diagnosis of human tuberculosis with its advantages and disadvantages will be covered, describing new omics and ultra-fast methods to increase knowledge and obtain a rapid diagnosis of tuberculosis.

Purification and structural characterization of Mce4A from Mycobacterium tuberculosis

The mce4A gene of Mycobacterium tuberculosis encodes a 400 amino acid residues protein of 43kDa, which is a mammalian cell entry protein (Mce4A) and plays important role in host cell invasion. Mce4A helps in long-term survival of M. tuberculosis by cholesterol utilization. Host cholesterol utilization mechanism by Mce4A is not clearly understood. In order to investigate the role of Mce4A in M. tuberculosis pathogenesis, we purified the recombinant protein by affinity chromatography, analyzed by SDS-PAGE and confirmed by western blot. We performed structural studies of Mce4A as function of pH and salt concentration by using different spectroscopic techniques. This protein was found to be stable over the wide range of pH 5.5≤pH≤11.5. An addition of sodium chloride up to the concentration of 150mM, shows no significant change in the secondary structure content of the protein. To confirm its activity, we performed isothermal titration calorimetry measurements of Mce4A in the presence of cholesterol. This is the first report of binding of cholesterol to Mce4A in vitro. Binding of cholesterol to Mce4A is sequential four-step and entropy driven process. The structural studies of this protein will help to understand the mechanism of pathogenesis of M. tuberculosis.

Expression of nuclear factor, erythroid 2-like 2-mediated genes differentiates tuberculosis

During infection and host defense, nuclear factor, erythroid 2-like 2 (Nrf2) dependent signaling is an efficient antioxidant defensive mechanism used by host cells to control the destructive effects of reactive oxygen species. This allows for effective defense responses against microbes while minimizing oxidative injury to the host cell itself. As a central regulator of antioxidant genes, Nrf2 has gained great attention in its pivotal role in infection, especially in tuberculosis (TB), the top infectious disease killer worldwide. To elucidate the genes potentially regulated by Nrf2 in TB, we conducted a meta-analysis on published gene expression datasets. Firstly, we compared the global gene expression profiles between control and Nrf2-deficient human cells. The differentially expressed genes were deemed as "Nrf2-mediated genes". Next, the whole blood gene expression pattern of TB patients was compared with that of healthy controls, pneumonia patients, and lung cancer patients. We found that the genes deregulated in TB significantly overlap with the Nrf2-mediated genes. Based on the intersection of Nrf2-mediated and TB-regulated genes, we identified an Nrf2-mediated 17-gene signature, which reflects a cluster of gene ontology terms highly related to TB physiology. We demonstrated that the 17-gene signature can be used to distinguish TB patients from healthy controls and patients with latent TB infection, pneumonia, or lung cancer. Also, the Nrf2-mediated gene signature can be used as an indicator of the anti-TB therapeutic response. More importantly, we confirmed that the predictive power of the Nrf2-mediated 17-gene signature is significantly better than the random gene sets selected from the human transcriptome. Also, the 17-gene signature performs even better than the random gene signatures selected from TB-associated genes. Our study confirms the central role of Nrf2 in TB pathogenesis and provides a novel and useful diagnostic method to differentiate TB patients from other human subjects.