Targeted RNA-Seq Reveals the M. tuberculosis Transcriptome from an In Vivo Infection Model.

The study of host-pathogen interactions using in vivo models with intracellular pathogens like Mycobacterium tuberculosis (Mtb) entails technical limitations, such as: (i) Selecting an efficient differential lysis system to enrich the pathogen cells; (ii) obtaining sufficient high-quality RNA; and (iii) achieving an efficient rRNA depletion. Thus, some authors had used flow cytometers to separate infected cells or significantly increase the sequencing depth of host-pathogen RNA libraries to observe the pathogens' gene expression. However, these options carry additional expenses in specialized equipment typically not available for all laboratories. Here, we propose an experimental protocol involving differential cell lysis and a probe-based ribosomal depletion to determine the gene expression of Mtb and its host during in vivo infection. This method increased the number of observed pathogen-expressed genes from 13 using the traditional RNA-seq approach to 702. After eliminating rRNA reads, we observed that 61.59% of Mtb sequences represented 702 genes, while 38.41% represented intergenic regions. Some of the most expressed genes codified for IS1081 (Rv2512c) transposase and eight PE-PGRS members, such as PGRS49 and PGRS50. As expected, a critical percent of the expressed genes codified for secreted proteins essential for infection, such as PE68, lppN, and LpqH. Moreover, three Mtb ncRNAs were highly expressed (small RNA MTS2823, transfer-messenger RNA RF00023, and ribozyme RF00010). Many of the host-expressed genes were related to the inflammation process and the expression of surfactant proteins such as the Sftpa and Sftpc, known to bind Mtb to alveolar macrophages and mi638, a microRNA with no previous associations with pulmonary diseases. The main objective of this study is to present the method, and a general catalog of the Mtb expressed genes at one point of the in vivo infection. We believe our method represents a different approach to the existing ones to study host-pathogen interactions in tuberculosis and other similar intracellular infections, without the necessity of specialized equipment.

Therapeutic effect of recombinant adenovirus encoding interferon-gamma in a murine model of progressive pulmonary tuberculosis.

We constructed recombinant adenoviruses encoding murine interferon-gamma (AdIFNgamma) and tested its therapeutic efficiency in a well characterized model of progressive pulmonary tuberculosis (TB) in Balb/c mice, infected through the trachea with the laboratory drug-susceptible H37Rv strain or multidrug-resistant (MDR) clinical isolate. When the disease was in a late phase, 2 months after infection, we administered by intratracheal cannulation a single dose [1.7 x 10(9) plaque forming units (pfu)] of AdIFNgamma or the control adenovirus. Groups of mice were killed at different time-points and the lungs were examined to determine bacilli colony forming units (CFU), cytokine/chemokine gene expression, and CD4/CD8 subpopulations, and also subjected to automated histomorphometry. In comparison with the control group, after 2 weeks of treatment and during the next 6 months, AdIFNgamma-treated animals infected with either the H37Rv strain or the MDR strain showed significantly lower bacilli loads and tissue damage (pneumonia), higher expressions of IFN-gamma, tumor necrosis factor (TNF), and inducible nitric oxide synthase (iNOS), and bigger granulomas. When compared with the results from conventional chemotherapy or AdIFNgamma treatment alone, the combined treatment with AdIFNgamma plus conventional chemotherapy shortened the time taken for reduction of bacillary load. This shows that gene therapy with AdIFNgamma efficiently reconstituted the protective immune response and controlled the progress of pulmonary TB produced by MDR or non-MDR strains.

[Gamma interferon: basics aspects, clinic significance and terapeutic uses]. / Interferón gamma: aspectos básicos, importancia clínica y usos terapéuticos.

Interferons are a family of pleiotropic cytokines, their name was assigned because of their anti-replicative viral activity. IFNgamma or immune type II interferon does not share receptors with the type I interferon, its structure is different and its gene is located in different chromosome, although its biologic effects are similar. Along of several years of research, it has been found that IFNgamma enhances the transcription of genes involved in immunomodulation, antiviral responses and antitumoral activities. Regarding to the immune system, IFNgamma increases the cytotoxic and phagocytic activity of macrophages and upregulates the expression of major histocompatibility complex (MHC) class I and class II molecules in dendritics cells and other antigen presenting cells. IFNgamma also promotes the development and differentiation of naive CD4+ T lymphocytes to Th1 helper subset. Indeed, this cytokine has a key role in the control of bacterial, micotic, viral and parasitic infections. Depending of the micro-environment, IFNgamma has a dual role as pro or anti inflammatory cytokine. Novel therapeutic strategies are currently being developed with the aim to enhance the immune response or replace IFNgamma gene abnormal expression with beneficial results in humans, being recombinant IFNgamma safe and well tolerated.

Therapeutic Effect of Recombinant Adenovirus Encoding Interferon-γ in a Murine Model of Progressive Pulmonary Tuberculosis.

We constructed recombinant adenoviruses encoding murine interferon-γ (AdIFNγ) and tested its therapeutic efficiency in a well characterized model of progressive pulmonary tuberculosis (TB) in Balb/c mice, infected through the trachea with the laboratory drug-susceptible H37Rv strain or multidrug-resistant (MDR) clinical isolate. When the disease was in a late phase, 2 months after infection, we administered by intratracheal cannulation a single dose [1.7 × 109 plaque forming units (pfu)] of AdIFNγ or the control adenovirus. Groups of mice were killed at different time-points and the lungs were examined to determine bacilli colony forming units (CFU), cytokine/chemokine gene expression, and CD4/CD8 subpopulations, and also subjected to automated histomorphometry. In comparison with the control group, after 2 weeks of treatment and during the next 6 months, AdIFNγ-treated animals infected with either the H37Rv strain or the MDR strain showed significantly lower bacilli loads and tissue damage (pneumonia), higher expressions of IFN-γ, tumor necrosis factor (TNF), and inducible nitric oxide synthase (iNOS), and bigger granulomas. When compared with the results from conventional chemotherapy or AdIFNγ treatment alone, the combined treatment with AdIFNγ plus conventional chemotherapy shortened the time taken for reduction of bacillary load. This shows that gene therapy with AdIFNγ efficiently reconstituted the protective immune response and controlled the progress of pulmonary TB produced by MDR or non-MDR strains.