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

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

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

STUDIES ON PROTECTIVE EFFECTS OF A VACCINE, BASED ON RECOMBINANT Ag85, TB10 AND FliC PROTEINS

At present time, there is an obvious need for a new generation of vaccines as the most effective preventive approach, in order to stop spreading of tuberculosis infection. So far, the most popular strategy is aimed at heterological vaccination. The idea is to use BCG, or improved BCG, or attenuated M. tuberculosis for primary vaccination. For the further booster vaccination one may apply thw s.c. subunit or vector vaccines, containing protective mycobacterial proteins. The aim of our investigation was to evaluate protective effects of a new vaccine based on recombinant bacterial proteins Ag85, ТВ10 and FliC. We used a model with aerosol M. tuberculosis H37Rv infection, and compared lung and spleen CFU counts and life-span of vaccinated versus non-vaccinated С57BL/6 mice. As a result, we revealed three vaccine variants with comparable protective capacity against BCG using our experimental model. The most promising variant is suggested for testing in preclinical trials

J. Exp. Med.

The cross talk between host and pathogen starts with recognition of bacterial signatures through pattern recognition receptors (PRRs), which mobilize downstream signaling cascades. We investigated the role of the cytosolic adaptor caspase recruitment domain family, member 9 (CARD9) in tuberculosis. This adaptor was critical for full activation of innate immunity by converging signals downstream of multiple PRRs. Card9(-/-) mice succumbed early after aerosol infection, with higher mycobacterial burden, pyogranulomatous pneumonia, accelerated granulocyte recruitment, and higher abundance of proinflammatory cytokines and granulocyte colony-stimulating factor (G-CSF) in serum and lung. Neutralization of G-CSF and neutrophil depletion significantly prolonged survival, indicating that an exacerbated systemic inflammatory disease triggered lethality of Card9(-/-) mice. CARD9 deficiency had no apparent effect on T cell responses, but a marked impact on the hematopoietic compartment. Card9(-/-) ranulocytes failed to produce IL-10 after Mycobaterium tuberculosis infection, suggesting that an absent antiinflammatory feedback loop accounted for granulocyte-dominated pathology, uncontrolled bacterial replication, and, ultimately, death of infected Card9(-/-) mice. Our data provide evidence that deregulated innate responses trigger excessive lung inflammation and demonstrate a pivotal role of CARD9 signaling in autonomous innate host defense against tuberculosis

Correlation between structural and transport properties of ca-doped la nickelates and their electrochemical performance

This work presents the results from a study of the structure and transport properties of Ca-doped La2NiO4+δ. La2−xCaxNiO4+δ (x = 0–0.4) materials that were synthesized via combustion of organic-nitrate precursors and characterized by X-ray diffraction (XRD), in situ XRD using synchrotron radiation, thermogravimetric analysis (TGA) and isotope exchange of oxygen with C18O2. The structure was defined as orthorhombic (Fmmm) for x = 0 and tetragonal (I4/mmm) for x = 0.1–0.4. Changes that occurred in the unit cell parameters and volume as the temperature changed during heating were shown to be caused by the excess oxygen loss. Typical for Ruddlesden–Popper phases, oxygen mobility and surface reactivity decreased as the Ca content was increased due to a reduction in the over-stoichiometric oxygen content with the exception of x = 0.1. This composition demonstrated its superior oxygen transport properties compared to La2NiO4+δ due to the enhanced oxygen mobility caused by structural features. Electrochemical data obtained showed relatively low polarization resistance for the electrodes with a low Ca content, which correlates well with oxygen transport properties. © 2021 by the authors. Licensee MDPI, Basel, Switzerland.The materials synthesis as well as electrochemical study were performed in a framework of the budget task of the IHTE UB RAS with using the equipment of the shared access center “Composition of compounds”. The TGA and isotope exchange studies were supported by the Ministry of Science and Higher Education of the Russian Federation within the governmental order for Boreskov Institute of Catalysis (projects АААА‐А21‐121011390007‐7, АААА‐А21‐ 121011390009‐1). The SXRD experiments were performed at the shared research center SSTRC on the basis of the Novosibirsk VEPP‐3 complex at BINP SB RAS, using equipment supported by pro‐ ject RFMEFI62119X0022

Identification of T-Cell Antigens Specific for Latent Mycobacterium Tuberculosis Infection

BACKGROUND: T-cell responses against dormancy-, resuscitation-, and reactivation-associated antigens of Mycobacterium tuberculosis are candidate biomarkers of latent infection in humans. METHODOLOGY/PRINCIPAL FINDINGS: We established an assay based on two rounds of in vitro restimulation and intracellular cytokine analysis that detects T-cell responses to antigens expressed during latent M. tuberculosis infection. Comparison between active pulmonary tuberculosis (TB) patients and healthy latently M. tuberculosis-infected donors (LTBI) revealed significantly higher T-cell responses against 7 of 35 tested M. tuberculosis latency-associated antigens in LTBI. Notably, T cells specific for Rv3407 were exclusively detected in LTBI but not in TB patients. The T-cell IFNgamma response against Rv3407 in individual donors was the most influential factor in discrimination analysis that classified TB patients and LTBI with 83% accuracy using cross-validation. Rv3407 peptide pool stimulations revealed distinct candidate epitopes in four LTBI. CONCLUSIONS: Our findings further support the hypothesis that the latency-associated antigens can be exploited as biomarkers for LTBI

Whole genome identification of Mycobacterium tuberculosis vaccine candidates by comprehensive data mining and bioinformatic analyses

<p>Abstract</p> <p>Background</p> <p><it>Mycobacterium tuberculosis</it>, the causative agent of tuberculosis (TB), infects ~8 million annually culminating in ~2 million deaths. Moreover, about one third of the population is latently infected, 10% of which develop disease during lifetime. Current approved prophylactic TB vaccines (BCG and derivatives thereof) are of variable efficiency in adult protection against pulmonary TB (0%–80%), and directed essentially against early phase infection.</p> <p>Methods</p> <p>A genome-scale dataset was constructed by analyzing published data of: (1) global gene expression studies under conditions which simulate intra-macrophage stress, dormancy, persistence and/or reactivation; (2) cellular and humoral immunity, and vaccine potential. This information was compiled along with revised annotation/bioinformatic characterization of selected gene products and <it>in silico </it>mapping of T-cell epitopes. Protocols for scoring, ranking and prioritization of the antigens were developed and applied.</p> <p>Results</p> <p>Cross-matching of literature and <it>in silico</it>-derived data, in conjunction with the prioritization scheme and biological rationale, allowed for selection of 189 putative vaccine candidates from the entire genome. Within the 189 set, the relative distribution of antigens in 3 functional categories differs significantly from their distribution in the whole genome, with reduction in the Conserved hypothetical category (due to improved annotation) and enrichment in Lipid and in Virulence categories. Other prominent representatives in the 189 set are the PE/PPE proteins; iron sequestration, nitroreductases and proteases, all within the Intermediary metabolism and respiration category; ESX secretion systems, resuscitation promoting factors and lipoproteins, all within the Cell wall category. Application of a ranking scheme based on qualitative and quantitative scores, resulted in a list of 45 best-scoring antigens, of which: 74% belong to the dormancy/reactivation/resuscitation classes; 30% belong to the Cell wall category; 13% are classical vaccine candidates; 9% are categorized Conserved hypotheticals, all potentially very potent T-cell antigens.</p> <p>Conclusion</p> <p>The comprehensive literature and <it>in silico</it>-based analyses allowed for the selection of a repertoire of 189 vaccine candidates, out of the whole-genome 3989 ORF products. This repertoire, which was ranked to generate a list of 45 top-hits antigens, is a platform for selection of genes covering all stages of <it>M. tuberculosis </it>infection, to be incorporated in rBCG or subunit-based vaccines.</p

SAPOSIN-LIKE PROTEINS IN ANTI-INFECTIOUS IMMUNE RESPONSE

Abstract. Besides the multiple hydrolytic enzymes, lysosomes are equipped with proteins apt to activate sphyngo-lipids — saposins (SAP). SAP belong to a broad and diverse family of moderate-size (~80 AA) saposin-like proteins (SAPLIP) containing specific domains with three disulfid e bonds bridging six cysteine residues. The diversity of SAPLIPS is likely explained by their involvement in distinct phases of engulfed bacteria digesting. Functionally similar SAPLIP were identified in a wide range of species — from amoeba to mammals, including humans. Saposins per se form a subfamily with six members: saposins A-D and the protein GM2 which possesses activatory functions. SAP do not have enzymatic activity, are heat-stable and protease resistant. The major in vivo function of SAP is released via participation in sphyngolipid catabolism and membrane digestion. In addition, complex association of SAP with membrane bi-layer and CD1 glycolipids is essential for loading lipid antigens onto antigen-presenting CD1 molecules for subsequent activation of lipid-specific T-cells. Of particular interest is participation of SAP in cross-presentation of bacterial antigens to CD8+ T-cells. A broad spectrum of SAP and SAPLIP involvement in the reactions of innate and adaptive immunity indicates their evolutionary conserved role in host defense