In 2015, more than 10% of tuberculosis (TB)-related deaths were attributable to M. tuberculosis with multiple drug-resistance (MDR-TB) and extensively drug-resistance (XDR-TB) (WHO 2016). In combination with insufficient commitment to the treatment regimen, the genetic heterogeneity and clonality of the patient's M. tuberculosis, as well as the poor permeability of the tuberculosis granuloma for the drug, can lead to monotherapy, despite the use of several drugs, which further promotes the spread of MDR and XDR-TB. Of particular concern is the rapid spread of resistance to newly introduced into clinical practice second-line drugs, intended for the treatment of MDR-TB — delamanid and bedaquiline. Thus, the spread of drug resistance to chemotherapy, along with the limited possibilities of chemotherapy in patients with MDR-TB and XDR-TB, dictate the need to supplement canonical chemotherapy with TB treatment methods directed at the host. MicroRNAs (miRs) are short sequences of single-stranded RNA that control up to 60% of genes encoding protein synthesis at a post-transcriptional level. Accumulating data points to the essential role of miRs in fine tuning the host response to infection, primarily by modulating the expression of proteins involved in the reactions of innate and adaptive immune responses. Despite the fact that the established functions of miRs activity are intracellular, a number of studies have discovered highly stable extracellular miRs circulating in blood. Currently, the possibility of using these molecules as biomarkers is being actively investigated. Chronic TB inflammation is characterized by parallel or step-bystep development of regulatory and pro-inflammatory processes that affect the severity and outcome of the disease. Both pro- and anti-inflammatory effects are elements of the bacterial strategy in the struggle for survival in the host organism. In this review we discuss the role of miRs as markers of tuberculosis infection, the nature and prognosis of the course of the disease, the involvement of miRs in the regulation of the innate and adaptive immunity in tuberculosis infection, and the perspectives for clinical usage of miRs as means for diagnosis and treatment of tuberculosis.

The protection against tuberculosis infection is largely determined by the ability of host tissue macrophages to limit the growth and spread of mycobacteria. Able to multiply within the host macrophages, mycobacteria have developed a number of protective mechanisms preventing phagosome-lysosome fusion, thereby evading damaging effects of lysosomal enzymes. Saposins are small, acidic, thermostable, non-enzymatic glycoproteins that participate as co-fac-tors in degradation of short oligosaccharide head group glycosphingolipids. Saposins A, B, C and D are formed in acidic endosomes due to cleavage of initial prosaposin molecule. The effect of saposins on human immune response is mediated by their involvement in presenting mycobacterial antigens on CD1 molecules. Preliminary studies with electron microscopy allowed to uncover saposin D-bound damaging effect on Mycobacterium tuberculosis in acidic environment. These data allowed us to suggest that saposin D is an important protective component fighting against TB infection. The aim of the study was to explore how saposin D deficiency might affect formation of anti-tuberculosis immune response and ability of macrophages to inhibit M. tuberculosis growth. Materials and methods. Interstitial pulmonary macrophages and peritoneal macrophages were isolated from wild type C57BL/6 strain and saposin D deficient C57BL/6-SapD-/- mouse strains. Results. It was found that as compared to macrophages from mice, macrophages from wild type strain significantly better controlled mycobacteria growth in vitro. To study an opportunity of compensating for deficient saposin D in peritoneal macrophages from C57BL/6-SapD-/- mice, a saposin D gene-bearing lentiviral vector was created. Transfection of SAPD-deficient peritoneal macrophages with expression vector compensated for saposin D deficiency in such cells and restored bactericidal function. The mechanisms of action for current anti-TB drugs are mediated by various metabolic pathways in mycobacteria (inhibited biosynthesis of fatty acids, arabinogalactan, peptidoglycan and protein; inhibition of DNA-dependent processes, proton pumps and cytochrome P450-dependent monooxygenases). Conclusion. It was shown that saposin D deficiency affects activation of macrophage bactericidal function in vitro. Our study data may be a prerequisite for biologically substantiated potential of using a vector construct bearing natural human protein gene such as saposin D, as a new anti-tuberculosis drug.

No abstract

Since 1924, BCG vaccine is used to protect children from the most severe forms of tuberculosis. At the same time, the protective effect of BCG in adults is variable. The potential for revaccination with live vaccine is further limited by the rapid spread of HIV infection. The early-secreted Mycobacterium tuberculosis proteins have been used extensively in TB vaccine development, due to their high immunogenicity and have shown protective effect in animal models. The aim of our study was to evaluate the opportunity to increase the anti-TB resistance in experimental animals by re-vaccination with a new subunit vaccine preparation following primary immunization with BCG. To perform such boost vaccination, we used a combination of the Ag85B-TB10.4-FliC chimeric protein, and the plasmid DNA encoding Ag85A antigen. Efficiency of the boost vaccination was evaluated in a model of M. tuberculosis H37Rv aerosol infection of C57BL / 6 laboratory mice, either in the intact animals, or those vaccinated with BCG only, or BCG followed by revaccination with the test vaccine. The data concerning mycobacteria outgrowth from the organs, and life-span of animals after infection were subject to comparative analysis. We have demonstrated that additional boost vaccination with the vaccine under study, as compared with conventional BCG vaccination, leads to further inhibition of mycobacteria dissemination from the site of infection, and significantly prolonged survival of infected animals.