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.

MTS1338, A Small Mycobacterium tuberculosis RNA, Regulates Transcriptional Shifts Consistent With Bacterial Adaptation for Entering Into Dormancy and Survival Within Host Macrophages

Small non-coding RNAs play a significant role in bacterial adaptation to changing environmental conditions. We investigated the dynamics of expression of MTS1338, a small non-coding RNA of Mycobacterium tuberculosis, in the mouse model in vivo, regulation of its expression in the infected macrophages, and the consequences of its overexpression in bacterial cultures. Here we demonstrate that MTS1338 significantly contributes to host-pathogen interactions. Activation of the host immune system triggered NO-inducible up-regulation of MTS1338 in macrophage-engulfed mycobacteria. Constitutive overexpression of MTS1338 in cultured mycobacteria improved their survival in vitro under low pH conditions. MTS1338 up-regulation launched a spectrum of shifts in the transcriptome profile similar to those reported for M. tuberculosis adaptation to hostile intra-macrophage environment. Using the RNA-seq approach, we demonstrate that gene expression changes accompanying MTS1338 overexpression indicate reduction in translational activity and bacterial growth. These changes indicate mycobacteria entering the dormant state. Taken together, our results suggest a direct involvement of this sRNA in the interplay between mycobacteria and the host immune system during infectious process.

Therapeutic Effect of Recombinant Mutated Interleukin 11 in the Mouse Model of Tuberculosis

Earlier we demonstrated that blocking of interleukin 11 (IL-11) by systemic administration of anti-IL-11 antibodies attenuates severity of Mycobacterium tuberculosis infection in mice. The substitution W147A in the IL-11 molecule creates the form of cytokine capable to disrupt gp130/IL11R signaling complex formation, thus serving as a high-affinity specific antagonist of IL-11-mediated signaling. We hypothesized that this mutant form of IL-11 may serve as an effective tool for inhibition of native IL-11 activity in vivo. We established the recombinant W147A mutant form of IL-11 in an optimized Escherichia coli expression system and administered it as the aerosol in the lungs of M. tuberculosis-susceptible I/St mice infected with M. tuberculosis Our results show that this therapeutic approach markedly inhibits tuberculous inflammation in lungs, increases the survival time of infected animals, and decreases expression of key inflammatory factors at the RNA and protein levels. These findings are a step toward clinical evaluation of the anti-IL-11 therapy for tuberculosis.

RNA-Seq analysis of Mycobacterium avium non-coding transcriptome

Deep sequencing was implemented to study the transcriptional landscape of Mycobacterium avium. High-resolution transcriptome analysis identified the transcription start points for 652 genes. One third of these genes represented leaderless transcripts, whereas the rest of the transcripts had 5' UTRs with the mean length of 83 nt. In addition, the 5' UTRs of 6 genes contained SAM-IV and Ykok types of riboswitches. 87 antisense RNAs and 10 intergenic small RNAs were mapped. 6 intergenic small RNAs, including 4.5S RNA and rnpB, were transcribed at extremely high levels. Although several intergenic sRNAs are conserved in M. avium and M. tuberculosis, both of these species have unique intergenic sRNAs. Moreover, we demonstrated that even conserved small RNAs are regulated differently in these species. Different sets of intergenic sRNAs may underlie differences in physiology between conditionally pathogenic M. avium and highly specialized pathogen M. tuberculosis.

Lung macrophages from bacille Calmette-Guérin-vaccinated guinea pigs suppress T cell proliferation but restrict intracellular growth of M. tuberculosis after recombinant guinea pig interferon-gamma activation

The guinea pig model of low-dose pulmonary tuberculosis has been used to study the pathogenesis of infection as well as the mechanisms of bacille Calmette-Guérin (BCG) vaccine-induced resistance. We investigated the function of lung cells from naive and BCG-vaccinated guinea pigs after enzymatic digestion of lung tissue with collagenase and DNase I. The total lung digest cells proliferated poorly to purified protein derivative (PPD) but comparatively better to ConA as assessed by [(3)H]-thymidine uptake. However, the non-adherent population obtained after plastic adherence of lung digests showed an enhanced response to concanavalin A (ConA) and PPD. Therefore, proliferation to ConA and PPD of nylon wool-purified T cells co-cultured with peritoneal (PMøs), alveolar (AMøs) or lung macrophages (LMøs) was assessed. Co-cultures of lung T cells and PMøs showed maximum proliferation to PPD, whereas proliferation was suppressed significantly by the addition of AMøs or LMøs. The response of T cells to ConA was unaffected in co-cultures. Incubation of co-cultures with recombinant guinea pig interferon-gamma (rgpIFN-gamma) did not reverse the suppression. In contrast, rgpIFN-gamma-treated plastic adherent LMøs that were non-specific esterase-positive were capable of reducing the intracellular growth of Mycobacterium tuberculosis. Similarly, total, non-adherent and adherent lung digest cells from BCG-vaccinated guinea pigs showed IFN-gamma and tumour necrosis factor (TNF)-alpha mRNA expression in response to ConA, lipopolysaccharide or PPD by reverse transcription-polymerase chain reaction followed by release of TNF protein but not IFN. These studies indicate that rgp-IFN-gamma-treated lung tissue macrophages from BCG-vaccinated guinea pigs are defective for inducing antigen-specific proliferation in T cells, but control the intracellular accumulation of virulent M. tuberculosis.

Antimycobacterial activity of bacteriocins and their complexes with liposomes

OBJECTIVES

Bacteriocins (Bcn) are natural peptides that are secreted by several taxonomically distant bacteria and exert bactericidal activity against other bacterial species. Their capacity to inhibit growth of virulent Mycobacterium tuberculosis H37Rv was evaluated in this study.

METHODS

Five different Bcn were isolated and purified from bacterial culture supernatants, their amino acid sequence was determined, and activity against mycobacteria assessed in three different models: in vitro mycobacterial cultures, in vitro infection of mouse macrophages and in vivo high-dose infection of inbred mice.

RESULTS

In the in vitro model, four out of five Bcn exhibited stronger antimycobacterial activity than equal concentrations of a widely used anti-TB antibiotic, rifampicin. These Bcn were non-toxic for mouse macrophages at a concentration of 0.1 mg/L (>MIC(90) of these compounds). Pure Bcn did not inhibit mycobacterial growth within murine macrophages when added at 0.01-0.1 mg/L, suggesting that at physiologically tolerable concentrations these molecules do not penetrate through the membrane of eukaryotic cells. However, when administered as a complex with phosphatidylcholine-cardiolipin liposomes, Bcn5 (selected as a model compound due to its cytotoxicity and antimycobacterial activity regular titration curves) demonstrated capacity both to inhibit intracellular growth of M. tuberculosis and to prolong survival of mice in an acute TB model.

CONCLUSIONS

Given that the mechanism of Bcn bactericidal activity differs from that of all commonly used antibiotics, their possible involvement in complex TB therapies deserves further study.

An ex vivo study of T lymphocytes recovered from the lungs of I/St mice infected with and susceptible to Mycobacterium tuberculosis

I/St mice, previously characterized as susceptible to Mycobacterium tuberculosis H37Rv, were given 10(3) or 10(5) CFU intravenously. At two time points postinoculation, the cell suspensions that resulted from enzymatic digestion of lungs were enumerated and further characterized phenotypically and functionally. Regarding the T-cell populations recovered at 2 and 5 weeks postinfection, two main results were obtained: (i) the population of CD44(-) CD45RB+ cells disappeared within 2 weeks postinfection, while the number of CD44(+) CD45RB-/low cells slowly increased between weeks 2 and 5; (ii) when cocultured with irradiated syngeneic splenocytes, these lung T cells proliferated in the presence of H37Rv sonicate. Using H37Rv sonicate and irradiated syngeneic splenocytes to reactivate lung T cells, we selected five CD3(+) CD4(+) CD8(-) T-cell clones. In addition to the H37Rv sonicate, the five clones react to both a short-term culture filtrate and an affinity-purified 15- to 18-kDa mycobacterial molecule as assessed by the proliferative assay. However, there was a clear difference between T-cell clones with respect to cytokine (gamma interferon [IFN-gamma] and interleukin-4 [IL-4] and IL-10) profiles: besides one Th1-like (IFN-gamma+ IL-4(-)) clone and one Th0-like (IFN-gamma+ IL-4(+) IL-10(+)) clone, three clones produced predominantly IL-10, with only marginal or no IL-4 and IFN-gamma responses. Inhibition of mycobacterial growth by macrophages in the presence of T cells was studied in a coculture in vitro system. It was found that the capacity to enhance antimycobacterial activity of macrophages fully correlated with INF-gamma production by individual T-cell clones following genetically restricted recognition of infected macrophages. The possible functional significance of cytokine diversity among T-cell clones is discussed.