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

In Mice, Tuberculosis Progression Is Associated with Intensive Inflammatory Response and the Accumulation of Gr-1dim Cells in the Lungs

Infection with Mycobacterium tuberculosis (Mtb) results in different clinical outcomes ranging from asymptomatic containment to rapidly progressing tuberculosis (TB). The mechanisms controlling TB progression in immunologically-competent hosts remain unclear.To address these mechanisms, we analyzed TB progression in a panel of genetically heterogeneous (A/SnxI/St) F2 mice, originating from TB-highly-susceptible I/St and more resistant A/Sn mice. In F2 mice the rates of TB progression differed. In mice that did not reach terminal stage of infection, TB progression did not correlate with lung Mtb loads. Nor was TB progression correlated with lung expression of factors involved in antibacterial immunity, such as iNOS, IFN-gamma, or IL-12p40. The major characteristics of progressing TB was high lung expression of the inflammation-related factors IL-1beta, IL-6, IL-11 (p<0.0003); CCL3, CCL4, CXCL2 (p<0.002); MMP-8 (p<0.0001). The major predictors of TB progression were high expressions of IL-1beta and IL-11. TNF-alpha had both protective and harmful effects. Factors associated with TB progression were expressed mainly by macrophages (F4-80(+) cells) and granulocytes (Gr-1(hi)/Ly-6G(hi) cells). Macrophages and granulocytes from I/St and A/Sn parental strains exhibited intrinsic differences in the expression of inflammatory factors, suggesting that genetically determined peculiarities of phagocytes transcriptional response could account for the peculiarities of gene expression in the infected lungs. Another characteristic feature of progressing TB was the accumulation in the infected lungs of Gr-1(dim) cells that could contribute to TB progression.In a population of immunocompetent hosts, the outcome of TB depends on quantitatively- and genetically-controlled differences in the intensity of inflammatory responses, rather than being a direct consequence of mycobacterial colonization. Local accumulation of Gr-1(dim) cells is a newly identified feature of progressing TB. High expression of IL-1beta and IL-11 are potential risk factors for TB progression and possible targets for TB immunomodulation

Analysis of Cellular Phenotypes That Mediate Genetic Resistance to Tuberculosis Using a Radiation Bone Marrow Chimera Approach

Adoptive transfer of bone marrow cells from tuberculosis-resistant (I/St × A/Sn)F(1) donor mice into lethally irradiated susceptible I/St recipients changed their phenotype following infection with virulent Mycobacterium tuberculosis. Compared to I/St→I/St control animals, F(1)→I/St chimeras demonstrated (i) prolonged survival time, (ii) increased antimycobacterial function of lung macrophages, (iii) elevated gamma interferon production by lung cells, and (iv) decreased infiltration of the lungs with CD4(+) and CD8(+) T cells and Ly-6G(+) neutrophils

The picture of leukocyte infiltration of the lung tissue of I/St (left) and B6 (right) mice infected with 2×10³ CFU of <i>M. avium</i> via aerosol route 8 weeks earlier.

<p>Peroxidase immune staining with hematoxylin counter-staining (×150). Cell populations are indicated on the left side. See text for the description.</p

The picture of leukocyte infiltration of the lung tissue of I/St (left) and B6 (right) mice infected with 2×10³ CFU of <i>M. avium</i> via aerosol route 16 weeks earlier.

<p>See legend to <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0010515#pone-0010515-g002" target="_blank">Fig. 2</a>.</p

Trans-ncRNAs.

<p>For each trans-ncRNA MTB homolog and genes flanking it are shown if present. For igMAV_2868-2869 homolog in MTB has not been revealed, although the region coding for this transcript is conserved among these species. Coordinates of trans-ncRNA are presented according to MAH104 genome and their types are predicted according to RFAM database.</p>*<p>Non-coding RNAs confirmed by Northern blotting.</p

The lung tissue surrounding necrotizing granuloma centers in mice susceptible to <i>M. tuberculosis</i> and <i>M. avium</i> is markedly hypoxic.

<p>I/St mice 6 wk after <i>M. tuberculosis</i> challenge (A) and B6 mice 16 wk after <i>M. avium</i> challenge (B) were injected with 60 mg/kg body weight of Hypoxyprobe™-1 and sacrificed 3 h later. Lung cryosections were obtained and developed for indirect peroxidase staining to detect hypoxia gradients (×200).</p

Structural Modifications of 3-Triazeneindoles and Their Increased Activity Against Mycobacterium tuberculosis

We synthesized 100 novel indole-based compounds with polyaza-functionalities, including 3-triazeneindoles, and tested their activity in vitro against laboratory M. tuberculosis H37Rv and clinical izoniazid-resistant CN-40 isolates, using gross and fine titration approaches. Here we present a few 3-triazeneindoles with the highest anti-mycobacterial activity. Introduction of short lipid tails into the 3-triazeneindole core additionally increased their activity against mycobacteria engulfed by murine macrophages. We also demonstrate that the compound TU112, one of the most active in our previous study, being not bioavailable after administration in mice per os, manifests prominent anti-mycobacterial activity after intravenous or aerosol delivery, as assessed by the mouse serum and lung supernatant titration assays

Predicted riboswitches.

<p>Coordinates of the riboswitches are provided according to MAH104 genome. Genes downstream of the riboswitches and regulated by them, products of these genes and types of riboswitches according to RFAM database are demonstrated.</p