The H2-A Class II molecule α/ß-chain cis-mismatch severely affects cell surface expression, selection of conventional CD4+ T cells and protection against TB infection.

Introduction: To dissect the role of the part of the H2 complex comprised of the MHC-II genes in the control of tuberculosis (TB) infection, we previously established a panel of recombinant congenic mouse strains bearing different segments of the H2 j haplotype on the B6 (H2 b) genetic background. Fine genetic mapping, gene sequencing and assessment of TB phenotypes resulted in identification of the H2-Ab gene as a major factor of TB control. Methods: We further narrowed the MHC-II H2 j interval by spotting a new recombination event, sequencing newly established DNA configuration and establishing a mouse strain B6.I-103 in which j/b recombination occurred within the coding sequence of the H2-Ab gene. Results: Unexpectedly, a novel H2-Aα b/AßjE0 haplotype provided exclusively high susceptibility to TB challenge. Immunologic analysis revealed an altered CD4+ T-cell selection and maintenance in B6.I-103 mice, as well as seriously impaired expression of the H2-Aαb/Aßj molecule on the surface of antigen presenting cells. Unlike previously reported cases of Class II malfunctioning, the defective phenotype arose not from strong structural mutations, but from regular recombination events within the MHC-II recombination hot spot region. Discussion: Our findings provide evidence that Class II α/ß-chain cis-allelic mismatches created by regular genetic recombination may severely affect immune system functioning. This issue is discussed in the context of the MHC evolution.

Prolonged B-Lymphocyte-Mediated Immune and Inflammatory Responses to Tuberculosis Infection in the Lungs of TB-Resistant Mice.

During tuberculosis (TB) infection, B-lymphocytes migrate to the lungs and form B-cell follicles (BCFs) in the vicinity of TB granulomata. B-cell-lacking mice display enhanced susceptibility to TB infection, and early B-cell depletion in infected non-human primates alters T-lymphocyte cytokine responses and increases bacterial burdens in the lungs. However, the role of B cells during late TB stages remained unaddressed. Here, we demonstrate that B cells and BCFs persist up to weeks 25-45 post-challenge in the lungs of TB-resistant C57BL/6 (B6) mice. In hyper-susceptible I/St mice, B-cell content markedly drops between weeks 12-16 post-infection, paralleled by diffuse lung tissue inflammation and elevated gene expression levels for pro-inflammatory cytokines IL-1, IL-11, IL-17a, and TNF-α. To check whether B-cells/BCFs control TB infection at advanced stages, we specifically depleted B-cells from B6 mice by administrating anti-CD20 mAbs at week 16 post-infection. This resulted in more rapid cachexia, a shortened lifespan of the infected animals, an increase in (i) lung-infiltrating CD8+ T cells, (ii) IL-6 production by F4/80+ macrophages, (iii) expression levels of genes for neutrophil-attracting factors CXCL1 and IL-17, and tissue-damaging factors MMP8, MMP9, and S100A8. Taken together, our results suggest that lung B cells and BCFs are moderately protective against chronic TB infection.

An In Vivo Model of Separate M. tuberculosis Phagocytosis by Neutrophils and Macrophages: Gene Expression Profiles in the Parasite and Disease Development in the Mouse Host.

The role of neutrophils in tuberculosis infection remains less well studied compared to that of the CD4+ T-lymphocytes and macrophages. Thus, alterations in Mycobacterium tuberculosis transcription profile following phagocytosis by neutrophils and how these shifts differ from those caused by macrophage phagocytosis remain unknown. We developed a mouse model that allows obtaining large amounts of either neutrophils or macrophages infected in vivo with M. tuberculosis for mycobacteria isolation in quantities sufficient for the whole genome RNA sequencing and aerosol challenge of mice. Here, we present: (i) the differences in transcription profiles of mycobacteria isolated from liquid cultures, neutrophils and macrophages infected in vivo; (ii) phenotypes of infection and lung inflammation (life span, colony forming units (CFU) counts in organs, lung pathology, immune cells infiltration and cytokine production) in genetically TB-susceptible mice identically infected via respiratory tract with neutrophil-passaged (NP), macrophage-passaged (MP) and conventionally prepared (CP) mycobacteria. Two-hour residence within neutrophils caused transcriptome shifts consistent with mycobacterial transition to dormancy and diminished their capacity to attract immune cells to infected lung tissue. Mycobacterial multiplication in organs did not depend upon pre-phagocytosis, whilst survival time of infected mice was shorter in the group infected with NP bacilli. We also discuss possible reasons for these phenotypic divergences.

Pleiotropic Effect of IL-6 Produced by B-Lymphocytes During Early Phases of Adaptive Immune Responses Against TB Infection.

The role of B cells migrating to the lung and forming follicles during tuberculosis (TB) inflammation is still the subject of debate. In addition to their antibody production and antigen-presenting functions, B cells secrete different cytokines and chemokines, thus participating in complex networks of innate and adaptive immunity. Importantly, lung B-cells produce high amounts of the pleiotropic gp130 cytokine IL-6. Its role during TB infection remains controversial, partly due to the fact that IL-6 is produced by different cell types. To investigate the impact of IL-6 produced by B cells on TB susceptibility and immune responses, we established a mouse strain with specific IL-6 deficiency in B cells (CD19cre-IL-6fl/fl, B-IL-6KO) on the B6 genetic background. Selective abrogation of IL-6 in B cells resulted in shortening the lifespan of TB-infected B-IL-6KO mice compare to the wild-type controls. We provide evidence that at the initial TB stages B cells serve as a critical source of IL-6. In the lung, the effect of IL-6 deficiency in B cells is associated rather with B and T cell functioning, than with macrophage polarization. TB-infected B-IL-6KO mice displayed diminished sizes of B cells themselves, CD4+IFN-γ+, Th17+, and CD4+CXCR5+ follicular T cell populations. The pleiotropic effect of B-cell-derived IL-6 on T-cells demonstrated in our study bridges two major lymphocyte populations and sheds some light on B- and T-cells interactions during the stage of anti-TB response when the host switches on a plethora of acquired immune reactions.

Prolonged infection triggered by dormant Mycobacterium tuberculosis: Immune and inflammatory responses in lungs of genetically susceptible and resistant mice.

We developed an approach for substantial attenuation of Mycobacterium tuberculosis by prolonged culturing under gradually acidifying conditions. Bacteria subjected to acidification lost the capacity to form colonies on solid media, but readily resuscitated their growth in the murine host, providing a useful model to study in vivo development of infection mimicking latent and reactivation tuberculosis (TB) in humans. Here we characterize biomarkers of lung pathology and immune responses triggered by such attenuated bacteria in genetically TB-susceptible and resistant mice. In susceptible I/St mice, CFU counts in lungs and spleens were ~1.5-log higher than in resistant B6 mice, accompanied by diffuse pneumonia and excessive lung infiltration with highly activated CD44+CD62L- T-lymphocytes resulting in death between months 7-9 post challenge. B6 mice were characterized by development of local inflammatory foci, higher production of pro-inflammatory IL-6 and IL-11 cytokines and a more balanced T-cell activation in their lungs. CFU counts remained stable in B6 mice during the whole 18-mo observation period, and all mice survived. Thus, we established a mouse model of fatal reactivation TB vs. indefinite mycobacterial possession after identical challenge and characterized the features of immune responses in the lung tissue underlining these polar phenotypes.

Reciprocal control of Mycobacterium avium and Mycobacterium tuberculosis infections by the alleles of the classic Class II H2-Aß gene in mice.

Genetic control of host susceptibility to M. avium, an important lung pathogen of immune-compromised individuals, remains incompletely defined. Apart from the slc11a1 (Nramp1) gene, which plays a pivotal role in genetic control of a few intracellular pathogens, including M. avium, in mice, we know nothing about genetic loci determining susceptibility to and/or severity of M. avium-triggered disease. Previously, our lab developed a panel of H2-congenic, recombinant mouse strains for identification of the MHC genes involved in the control of M. tuberculosis infection. In the present study, we applied a few recombinant strains from this panel to study $ possible influence of allelic variations in classical Class II genes on the development of M. avium infection. Our results demonstrate a clear difference in lung pathology, post-infection survival time, lung neutrophil influx and corresponding chemokine/cytokine responses, as well as the degree of lung T lymphocyte activation, between mouse strains differing by the alleles of a single highly polymorphic Class II H2-Aß gene. Paradoxically, mice carrying the H2-Aßb allele, which provides a notable protective effect against M. tuberculosis compared to the H2-Aßj allele, were more susceptible to M. avium infection as indicated by several parameters of the disease. We discuss possible reasons for such a reciprocal expression of phenotypes determined by a single allelic variant during two "similar" infections that may concern differences in virulence, NO-sensitivity, intracellular life style and antigenic composition between these two mycobacterial species.

A new model for chronic and reactivation tuberculosis: Infection with genetically attenuated Mycobacterium tuberculosis in mice with polar susceptibility.

TB infection in mice develops relatively rapidly which interferes with experimental dissection of immune responses and lung pathology features that differ between genetically susceptible and resistant hosts. Earlier we have shown that the M. tuberculosis strain lacking four of five Rpf genes (ΔACDE) is seriously attenuated for growth in vivo. Using this strain, we assessed key parameters of lung pathology, immune and inflammatory responses in chronic and reactivation TB infections in highly susceptible I/St and more resistant B6 mice. ΔACDE mycobacteria progressively multiplied only in I/St lungs, whilst in B6 lung CFU counts decreased with time. Condensed TB foci apeared in B6 lungs at week 4 of infection, whilst in I/St their formation was delayed. At the late phase of infection, in I/St lungs TB foci fused resulting in extensive pneumonia, whereas in B6 lungs pathology was limited to condensed foci. Macrophage and neutrophil populations characteristically differed between I/St and B6 mice at early and late stages of infection: more neutrophils accumulated in I/St and more macrophages in B6 lungs. The expression level of chemokine genes involved in neutrophil influx was higher in I/St compared to B6 lungs. B6 lung cells produced more IFN-γ, IL-6 and IL-11 at the early and late phases of infection. Overall, using a new mouse model of slow TB progression, we demonstrate two important features of ineffective infection control underlined by shifts in lung inflammation: delay in early granuloma formation and fusion of granulomas resulting in consolidated pneumonia late in the infectious course.

B-lymphocytes forming follicle-like structures in the lung tissue of tuberculosis-infected mice: Dynamics, phenotypes and functional activity.

During tuberculosis (TB) infection, B cells form follicles in close vicinity of lung granuloma. We assessed the dynamics of follicle formation, surface phenotypes and functional activity of lung B cells during TB course in genetically susceptible mice. The follicles appeared early post infection and peaked at weeks 7-8. Lung B cells resembled classical B2 cells (CD19+IgMloIgDhiCD1d-CD21/35intCD5-CD11b-CD43-), but differed from them by the absence of B2 marker CD23. Lung B-cells constitutively expressed MHC II molecules, presented mycobacterial antigens to immune CD4+ T-cells and produced high amounts of IL-6 and IL-11, but no classical type 1 (TNF-α, IFN-γ), or anti-inflammatory (IL-10, TGF-ß) cytokines. The total antibody response in tuberculous lung showed almost no specificity to mycobacteria. A panel of monoclonal antibodies obtained from lung B cells contained only few clones with reactivity to mycobacteria. Our results suggest that anti-TB B cell response in the lung has clear pathological and doubtful protective role.

Pathways for H2 Activation on (Ni)-MoS2 Catalysts.

The activation of H2 and H2S on (Ni)MoS2/Al2O3 leads to the formation of SH groups with acid character able to protonate 2,6-dimethylpyridine. The variation in concentrations of SH groups induced by H2 and H2S adsorption shows that both molecules dissociate on coordinatively unsaturated cations and neighboring S(2-). In the studied materials, one sulfur vacancy and four SH groups per 10 metal atoms exist at the active edges of MoS2 under the conditions studied. H2-D2 exchange studies show that Ni increases the concentration of active surface hydrogen by up to 30% at the optimum Ni loading, by increasing the concentration of H2 and H2S chemisorption sites.

Impact of Atmospheric Microparticles on the Development of Oxidative Stress in Healthy City/Industrial Seaport Residents.

Atmospheric microsized particles producing reactive oxygen species can pose a serious health risk for city residents. We studied the responses of organisms to microparticles in 255 healthy volunteers living in areas with different levels of microparticle air pollution. We analyzed the distribution of microparticles in snow samples by size and content. ELISA and flow cytometry methods were employed to determine the parameters of the thiol-disulfide metabolism, peroxidation and antioxidant, genotoxicity, and energy state of the leukocytes. We found that, in the park areas, microparticles with a size of 800 µm or more were predominant (96%), while in the industrial areas, they tended to be less than 50 µm (93%), including size 200-300 nm (7%). In the industrial areas, we determined the oxidative modification of proteins (21% compared to the park areas, p ≤ 0.05) and DNA (12%, p ≤ 0.05), as well as changes in leukocytes' energy potential (53%, p ≤ 0.05). An increase in total antioxidant activity (82%, p ≤ 0.01) and thiol-disulfide system response (thioredoxin increasing by 33%, p ≤ 0.01; glutathione, 30%, p ≤ 0.01 with stable reductases levels) maintains a balance of peroxidation-antioxidant processes, protecting cellular and subcellular structures from significant oxidative damage.

Mycobacterium avium-triggered diseases: pathogenomics.

The species Mycobacterium avium includes several subspecies representing highly specialized avian and mammalian pathogens, non-obligatory pathogens of immune compromised humans and saprophitic organisms. Recently obtained information concerning the diversity of M. avium genomic structures not only clarified phylogenic relationships within this species, but began to shed light on the question of how such closely related microorganisms adapt to the occupation of distinct ecological niches. In this review we discuss specific features of M. avium genetic composition, as well as genetic and molecular aspects of M. avium hominissuis (MAH)-triggered disease pathogenesis, including virulence, penetration, immune response manipulation and host genetic control.

Host genetics in granuloma formation: human-like lung pathology in mice with reciprocal genetic susceptibility to M. tuberculosis and M. avium.

Development of lung granulomata is a hallmark of infections caused by virulent mycobacteria, reflecting both protective host response that restricts infection spreading and inflammatory pathology. The role of host genetics in granuloma formation is not well defined. Earlier we have shown that mice of the I/St strain are extremely susceptible to Mycobacterium tuberculosis but resistant to M. avium infection, whereas B6 mice show a reversed pattern of susceptibility. Here, by directly comparing: (i) characteristics of susceptibility to two infections in vivo; (ii) architecture of lung granulomata assessed by immune staining; and (iii) expression of genes encoding regulatory factors of neutrophil influx in the lung tissue, we demonstrate that genetic susceptibility of the host largely determines the pattern of lung pathology. Necrotizing granuloma surrounded by hypoxic zones, as well as a massive neutrophil influx, develop in the lungs of M. avium-infected B6 mice and in the lungs of M. tuberculosis-infected I/St mice, but not in the lungs of corresponding genetically resistant counterparts. The mirror-type lung tissue responses to two virulent mycobacteria indicate that the level of genetic susceptibility of the host to a given mycobacterial species largely determines characteristics of pathology, and directly demonstrate the importance of host genetics in pathogenesis.

A human-like TB in genetically susceptible mice followed by the true dormancy in a Cornell-like model.

Mouse tuberculosis (TB) models that utilize genetically susceptible mouse strains demonstrate many features of human lung disease. In the present study, pathology caused by progressive M. tuberculosis H37Rv infection in TB-susceptible I/St mice following the low-dose aerosol challenge showed close similarity to human TB, with formation of necrotic granuloma with adjusting B-cell-rich follicles. A remarkable feature was the development of hypoxic zones around TB lesions by day 60 of infection. Necrotizing inflammatory foci were abundantly infiltrated with Ly-6G+ neutrophils. The levels of mRNA for neutrophil-recruiting factors (KC, MIP-2, IL-17 and IL-6) were all significantly increased in infected compared to naïve animals. A profound elevation of the mRNA level for IFN-gamma resulted neither in mycobacterial growth inhibition, nor in IL-17 response counter-regulation. Three-month therapy with RIF and INH resulted in eradication of culturable mycobacteria (at least 9 months following withdrawal), recovery of the lung tissue structure, and normalization of inflammatory genes expression. However, stable mycobacterial DNA (M. tuberculosis-specific insertion IS6110 detected by the qrt-PCR) was retained in the lungs for a long time after culturable bacilli were eliminated, and combination of lung homogenate liquid cultures with auramine staining demonstrated the presence of acid-fast bacilli with unaltered mycobacterial morphology. The lack of mycobacterial growth on agar, their microscopic detection in concentrated liquid cultures, and the increase in numbers of IS6110 copies in vivo at late stages of cured infection suggest that in our model dormant M. tuberculosis survived in the host.

Specificity and efficacy of dendritic cell-based vaccination against tuberculosis with complex mycobacterial antigens in a mouse model.

Dendritic cells (DC) likely play important and unique roles in the generation of protective immunity to mycobacteria. In order to clarify their contributions, bone marrow-derived DC loaded with Mycobacterium tuberculosis sonicate antigens were used to stimulate T cell proliferation both in vitro and in vivo and to vaccinate C57BL/6 mice against subsequent challenge with virulent mycobacteria. Antigen-pulsed DC developed in fetal calf serum (FCS-DC), but not DC developed in normal mouse serum (NMS-DC), stimulated significant proliferation of both naïve and immune T cells in vitro. The difference between cell populations developed in FCS and NMS in the content of CD11c(+) cells and in production of key cytokines indicated that NMS is less supportive for the development of activated DC. However, following adoptive transfer of a single dose of antigen-pulsed DC into naive recipients, NMS-DC induced T cells that proliferated in response to mycobacterial antigen, whereas FCS-DC stimulated strong non-specific proliferation. Vaccination with two doses of antigen-pulsed NMS-DC by the subcutaneous route induced significant protection against intravenous challenge with a moderate dose of virulent M. tuberculosis. DC-vaccinated mice exhibited significant reductions in bacillary loads in the lungs and spleens, and markedly reduced lung pathology. Three doses of antigen-pulsed NMS-DC induced a significant increase in survival time following high dose challenge, which correlated with a significant increase in IFN-gamma-producing cells in both lung and lymphoid tissues, as assessed by the ELISPOT assay. Taken together, these results indicate that DC play a critical role in the induction of protective resistance against virulent mycobacterial challenge accompanied by the development of antigen-reactive, IFN-gamma-producing T cells, and that their antigenic specificity is influenced by the culture conditions under which the DC are developed.

Mycobacterial dissemination and cellular responses after 1-lobe restricted tuberculosis infection of genetically susceptible and resistant mice.

BACKGROUND AND METHODS: To study mycobacterial dissemination and immune-cell trafficking in tuberculosis, we developed a mouse model in which we introduced 1 microL of Mycobacterium tuberculosis directly into the middle lobe of the right lung. We investigated the kinetics of both mycobacterial spread to different anatomical sites and recruitment of phagocytes and activated lymphocytes. RESULTS: Mycobacterial dissemination was independent of susceptibility to infection and was identical in H-2-congenic mouse strains with high and low resistance to tuberculosis. In resistant mice, recruitment of phagocytic cells to the uninfected lung occurred before the appearance of mycobacteria and decreased shortly thereafter. In susceptible mice, this recruitment was delayed in both lungs but increased during a 10-week period. Recruitment of CD4+ and CD8+ lymphocytes to the contralateral lung was observed before mycobacterial dissemination in both strains, so mycobacterial seeding of secondary tissues occurred in the presence of immune lymphocytes. In resistant mice, more T cells expressed the CD44hi CD62lo activation phenotype, and higher levels of interferon- gamma were produced. CONCLUSIONS: Mycobacterial spread to lymphoid organs preceded spread to the initially uninfected contralateral lung. Genetic differences in susceptibility to tuberculosis are associated with differences in dynamics of the immune response, rather than differences in mycobacterial trafficking.