A nonspecific component of BCG vaccination

Decades of research on the mechanisms of immunological protection against Mycobacterium tuberculosis, the causative agent of tuberculosis (ТВ), did not allow us to draw a final conclusion about the relative importance of specific pathways when forming protective immunological memory. The BCG vaccine, being the only so far approved tuberculosis vaccine protects children from severe forms of ТВ infection. It is still unclear why BCG does not save from primary infection, reactivation of ТВ and latent carrying. At the same time, the association between BCG vaccination and a reduced risk of non-mycobacterial infections, allergies, cancer and general mortality has been demonstrated. Such nonspecific effects of BCG are dependent mostly on the innate immune cells, rather than on specific memory Т cells. There is evidence of an adjuvant effect of BCG vaccination with respect to the humoral immune response to a variety of childhood vaccines. This review is focused mostly on the analysis of works aimed at studying the relatively recently identified mechanism for generating the non-specific effect of the BCG vaccine, i.e., development of induced natural immunity. This phenomenon is mediated by NOD2 signaling and epigenetic macrophage modification and, due to BCG vaccination, leads to enhanced capacity of macrophages to produce TNFa and IL-6 in response to stimulation by BCG-nonrelated microorganisms or TLR ligands. Induced immunity does not only reshape transmission of immunological signals between the cells of innate immune system, but also induces profound changes in the balance of metabolic pathways, such as glycolysis, oxidative phosphorylation, metabolism of amino acids and fatty acids, being accompanied by enhanced ability of innate immune cells to respond to the secondary stimulation. Realizing these intracellular processes opens up new opportunities for therapeutic intervention into the regulation of immune processes accompanying infectious and inflammatory diseases. In general, an in-depth study of the non-specific component of BCG vaccination should lead to emergence of new ideas about the mechanisms of its protective action, as well as affect development of a new ТВ vaccine. This knowledge can stimulate changes in global vaccination policy, aiming for optimization of vaccination benefits and reduction of childhood morbidity and mortality, as well as decrease of the post-vaccinal complications

Interleukin-11 Drives Early Lung Inflammation during Mycobacterium tuberculosis Infection in Genetically Susceptible Mice

IL-11 is multifunctional cytokine whose physiological role in the lungs during pulmonary tuberculosis (TB) is poorly understood. Here, using in vivo administration of specific antibodies against IL-11, we demonstrate for the first time that blocking IL-11 diminishes histopathology and neutrophilic infiltration of the lung tissue in TB-infected genetically susceptible mice. Antibody treatment decreased the pulmonary levels of IL-11 and other key inflammatory cytokines not belonging to the Th1 axis, and down-regulated IL-11 mRNA expression. This suggests the existence of a positive feedback loop at the transcriptional level, which is further supported by up-regulation of IL-11 mRNA expression in the presence of rIL-11 in in vitro cultures of lung cells. These findings imply a pathogenic role for IL-11 during the early phase of Mycobacterium tuberculosis-triggered disease in a genetically susceptible host

PROTECTIVE EFFECT INDUCED BY THE NEW SUBUNIT TUBERCULOSIS VACCINE WHEN USED AS A BCG BOOST IS ASSOCIATED WITH INHIBITION OF MYCOBACTERIAL DISSEMINATION

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

Saposin D acting on macrophage bacteriostatic function in experimental tuberculosis infection

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

MicroRNA AND TUBERCULOSIS

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

DURATION OF IMMUNE RESPONSE INDUCED BY THE VACCINE BASED ON RECOMBINANT Ag85, TB10 AND FliC PROTEINS

Already about one hundred years BCG remains the only widely used tuberculosis (TB) vaccine. It is known that intensity of the BCG-induced Th1 immune response decreases over time and comes to naught within 10-15 years. It significantly distinguishes BCG from the vaccines providing a lifelong protection such as vaccines against poliomyelitis or measles, and can be bound to natural restriction of duration of a persistence of the BCG-induced CD4+ T-cells. Data on insufficient ability of BCG to stimulate life-long immunological memory is accumulating. Earlier in our lab on the model of rather resistant to TB C57BL/6 mice infection with the virulent laboratory strain of Mycobacterium tuberculosis (Mtb) H37Rv protective activity (comparable to that of BCG Russia) of 3 subunit vaccine variants was demonstrated as assessed by lung and spleen CFU counts and life span of animals after infection. The aim of this study was to study the characteristics and duration of the immune response induced by the most effective variant of these vaccines. Groups of C57BL/6 mice were vaccinated intramuscularly twice with two-week intervals with 10 μg protein conjugated to 200 μl of an aluminum hydroxide emulsion. Immune response (production of specific antibodies, vaccine proteinstimulated production of interferon gamma and proliferation in vitro) was monitored during 10 months after vaccination. We have shown that the test vaccine induces in mice the formation of long-term immunological memory to a bacterial antigen. Moreover, in the presence of glutoxim the immunological memory spectrum shifts to a "protective" type, i.e. the predominance of the cellular component of the immune response over the antibody response is stimulated. The next step will be the investigation of vaccine effectiveness for revaccination after primary BCG immunization

Anti-IL-11 antibody therapy decreases levels of IL-11 and pro-inflammatory factors in the lung tissue without shifting the IL-12 – IFN-γ/IL-10 balance.

<p>Cytokine contents in lung homogenates were assessed by ELISA for 4 mice in each group. The results of one of two similar experiments are displayed as mean ± SEM.</p

Treatment with anti-IL-11 antibodies significantly attenuates the severity of TB in I/St mice.

<p>(A) ∼3-fold decrease in lung CFU counts compared to control animals. (B and C) Lung pathology in individual animals. None of anti-IL-11-treated mice developed necrotic TB foci evident in control mice <i>a</i>, <i>d</i> and <i>g</i> (circled). (D) Statistical evaluation of the proportion of inflamed lung tissue. CFU counts and morphometry were performed in all mice included in 2 independent experiments (total N = 16 and 17 for experimental and control groups, respectively). Histology is displayed for individual mice analyzed in one experiment (N = 7 for each group).</p

Protein levels of IL-11 affect IL-11 mRNA expression.

<p>(A) <i>In vivo</i> administration of anti-IL-11 antibodies leads to a selective down-regulation of IL-11 mRNA. The level of expression was quantified in 5 individual mice per group, using qrt-PCR and normalization against the level of GAPDH expression. Results obtained in 1 of 2 similar experiments are expressed as mean ± SEM (for IL-11 expression <i>P</i> = 0.021, for other cytokines <i>P</i>>0.05). (B) Introduction of 100 ng/ml rIL-11 in cultures of lung cells up-regulates the expression of IL-11 mRNA. Results of two similar experiments are expressed as mean of 3 wells ± SEM (<i>P</i><0.01, ANOVA, compared to negative controls and cultures stimulated with 10 ng/ml IL-11).</p

Properties of anti-IL-11 polyclonal antibodies.

<p>(A) Reactivity of affinity purified rabbit globulin preparation against mIL-11 assessed in ELISA format. No reactivity was found in pre-immune globulin (diamonds); immunoglobulin from rabbits immunized thrice with rmIL-11 showed very strong reactivity (squares); after exhaustion on mycobacterial sonicate adsorbent, specific anti-IL-11 reactivity dropped but was readily detected (triangles). (B) Immune blotting with rmIL-11 with polyclonal rabbit anti-mIL-11 antibodies (preparation identical to one displayed as triangles in (A). Tracks: 1, 2 – immune rabbits 1 and 2; 3, 4 – pre-immune rabbits 1 and 2; 5 – conjugate-free control.</p