Beneficial or detrimental activity of regulatory T cells, indoleamine 2,3-dioxygenase, and heme oxygenase-1 in the lungs is influenced by the level of virulence of Mycobacterium tuberculosis strain infection

Tuberculosis (TB) caused by the complex Mycobacterium tuberculosis (Mtb) is the main cause of death by a single bacterial agent. Last year, TB was the second leading infectious killer after SARS-CoV-2. Nevertheless, many biological and immunological aspects of TB are not completely elucidated, such as the complex process of immunoregulation mediated by regulatory T cells (Treg cells) and the enzymes indoleamine 2,3-dioxygenase (IDO) and heme oxygenase 1 (HO-1). In this study, the contribution of these immunoregulatory factors was compared in mice infected with Mtb strains with different levels of virulence. First Balb/c mice were infected by intratracheal route, with a high dose of mild virulence reference strain H37Rv or with a highly virulent clinical isolate (strain 5186). In the lungs of infected mice, the kinetics of Treg cells during the infection were determined by cytofluorometry and the expression of IDO and HO-1 by RT-PCR and immunohistochemistry. Then, the contribution of immune-regulation mediated by Treg cells, IDO and HO-1, was evaluated by treating infected animals with specific cytotoxic monoclonal antibodies for Treg cells depletion anti-CD25 (PC61 clone) or by blocking IDO and HO-1 activity using specific inhibitors (1-methyl-D,L-tryptophan or zinc protoporphyrin-IX, respectively). Mice infected with the mild virulent strain showed a progressive increment of Treg cells, showing this highest number at the beginning of the late phase of the infection (28 days), the same trend was observed in the expression of both enzymes being macrophages the cells that showed the highest immunostaining. Animals infected with the highly virulent strain showed lower survival (34 days) and higher amounts of Treg cells, as well as higher expression of IDO and HO-1 one week before. In comparison with non-treated animals, mice infected with strain H37Rv with depletion of Treg cells or treated with the enzymes blockers during late infection showed a significant decrease of bacilli loads, higher expression of IFN-g and lower IL-4 but with a similar extension of inflammatory lung consolidation determined by automated morphometry. In contrast, the depletion of Treg cells in infected mice with the highly virulent strain 5186 produced diffuse alveolar damage that was similar to severe acute viral pneumonia, lesser survival and increase of bacillary loads, while blocking of both IDO and HO-1 produced high bacillary loads and extensive pneumonia with necrosis. Thus, it seems that Treg cells, IDO and HO-1 activities are detrimental during late pulmonary TB induced by mild virulence Mtb, probably because these factors decrease immune protection mediated by the Th1 response. In contrast, Treg cells, IDO and HO-1 are beneficial when the infection is produced by a highly virulent strain, by regulation of excessive inflammation that produced alveolar damage, pulmonary necrosis, acute respiratory insufficiency, and rapid death.

Brain radiotoxicity-related 15CAcBRT gene expression signature predicts survival prognosis of glioblastoma patients

BACKGROUND

Glioblastoma is the most common and devastating primary brain cancer. Radiotherapy is standard of care; however, it is associated with brain radiation toxicity (BRT). This study used a multi-omics approach to determine whether BRT-related genes (RGs) harbor survival prognostic value and whether their encoded proteins represent novel therapeutic targets for glioblastoma.

METHODS

RGs were identified through analysis of single-nucleotide variants associated with BRT (R-SNVs). Functional relationships between RGs were established using Protein-Protein Interaction networks. The influence of RGs and their functional groups on glioblastoma prognosis was evaluated using clinical samples from the Glioblastoma Bio-Discovery Portal database and validated using the Chinese Glioma Genome Atlas dataset. The identification of clusters of radiotoxic and putative pathogenic variants in proteins encoded by RGs was achieved by computational 3D structural analysis.

RESULTS

We identified the BRT-related 15CAcBRT molecular signature with prognostic value in glioblastoma, by analysis of the COMT and APOE protein functional groups. Its external validation confirmed clinical relevance independent of age, MGMT promoter methylation status, and IDH mutation status. Interestingly, the genes IL6, APOE, and MAOB documented significant gene expression levels alteration, useful for drug repositioning. Biological networks associated with 15CAcBRT signature involved pathways relevant to cancer and neurodegenerative diseases. Analysis of 3D clusters of radiotoxic and putative pathogenic variants in proteins coded by RGs unveiled potential novel therapeutic targets in neuro-oncology.

CONCLUSIONS

15CAcBRT is a BRT-related molecular signature with prognostic significance for glioblastoma patients and represents a hub for drug repositioning and development of novel therapies.

Close Related Drug-Resistance Beijing Isolates of Mycobacterium tuberculosis Reveal a Different Transcriptomic Signature in a Murine Disease Progression Model

Mycobacterium tuberculosis (MTB) lineage 2/Beijing is associated with high virulence and drug resistance worldwide. In Colombia, the Beijing genotype has circulated since 1997, predominantly on the pacific coast, with the Beijing-Like SIT-190 being more prevalent. This genotype conforms to a drug-resistant cluster and shows a fatal outcome in patients. To better understand virulence determinants, we performed a transcriptomic analysis with a Beijing-Like SIT-190 isolate (BL-323), and Beijing-Classic SIT-1 isolate (BC-391) in progressive tuberculosis (TB) murine model. Bacterial RNA was extracted from mice lungs on days 3, 14, 28, and 60. On average, 0.6% of the total reads mapped against MTB genomes and of those, 90% against coding genes. The strains were independently associated as determined by hierarchical cluster and multidimensional scaling analysis. Gene ontology showed that in strain BL-323 enriched functions were related to host immune response and hypoxia, while proteolysis and protein folding were enriched in the BC-391 strain. Altogether, our results suggested a differential bacterial transcriptional program when evaluating these two closely related strains. The data presented here could potentially impact the control of this emerging, highly virulent, and drug-resistant genotype.

Structural homology between 11 beta-hydroxysteroid dehydrogenase and Mycobacterium tuberculosis Inh-A enzyme: Dehydroepiandrosterone as a potential co-adjuvant treatment in diabetes-tuberculosis comorbidity

Metabolic syndrome is considered the precursor of type 2 diabetes mellitus. Tuberculosis is a leading infection that constitutes a global threat remaining a major cause of morbi-mortality in developing countries. People with type 2 diabetes mellitus are more likely to suffer from infection with Mycobacterium tuberculosis. For both type 2 diabetes mellitus and tuberculosis, there is pulmonary production of anti-inflammatory glucocorticoids mediated by the enzyme 11β-hydroxysteroid dehydrogenase type 1 (11β-HSD1). The adrenal hormone dehydroepiandrosterone (DHEA) counteracts the glucocorticoid effects of cytokine production due to the inhibition of 11β-HSD1. Late advanced tuberculosis has been associated with the suppression of the Th1 response, evidenced by a high ratio of cortisol/DHEA. In a murine model of metabolic syndrome, we determined whether DHEA treatment modifies the pro-inflammatory cytokines due to the inhibition of the 11β-HSD1 expression. Since macrophages express 11β-HSD1, our second goal was incubating them with DHEA and Mycobacterium tuberculosis to show that the microbicide effect was increased by DHEA. Enoyl-acyl carrier protein reductase (InhA) is an essential enzyme of Mycobacterium tuberculosis involved in the mycolic acid synthesis. Because 11β-HSD1 and InhA are members of a short-chain dehydrogenase/reductase family of enzymes, we hypothesize that DHEA could be an antagonist of InhA. Our results demonstrate that DHEA has a direct microbicide effect against Mycobacterium tuberculosis; this effect was supported by in silico docking analysis and the molecular dynamic simulation studies between DHEA and InhA. Thus, DHEA increases the production of pro-inflammatory cytokines in the lung, inactivates GC by 11β-HSD1, and inhibits mycobacterial InhA. The multiple functions of DHEA suggest that this hormone or its synthetic analogs could be an efficient co-adjuvant for tuberculosis treatment.

A significant therapeutic effect of silymarin administered alone, or in combination with chemotherapy, in experimental pulmonary tuberculosis caused by drug-sensitive or drug-resistant strains: In vitro and in vivo studies

For many years, tuberculosis (TB) has been a major public health problem worldwide. Advances for treatment and eradication have been very limited. Silymarin (Sm) is a natural product with antioxidant and hepatoprotective activities that has been proposed as a complementary medicine to reduce the liver injury produced by the conventional anti-TB chemotherapy. Sm also has immunoregulatory and microbicide properties. In this study, we determined the effect of Sm on the growth control of mycobacteria. In vitro studies showed that Sm and Silibinin (the principal active compound of Sm) have microbicidal activity against drug-sensitive and multidrug-resistant (MDR) mycobacteria, induce the production of protective cytokines from infected macrophages, and improve the growth control of mycobacteria (p ≤ 0.0001). Studies in vivo using a model of progressive pulmonary TB in BALB/c mice infected with drug-sensitive or MDR mycobacteria have shown that Sm induces significant expression of Th-1 cytokines such as IFN-γ and IL-12 as well as TNFα, which produce significant therapeutic activity when administered alone and apparently have a synergistic effect with chemotherapy. These results suggest that Sm has a bactericidal effect and can contribute to the control and establishment of a TH1 protective immune response against mycobacterial infection. Thus, it seems that this flavonoid has a promising potential as adjuvant therapy in the treatment of TB.

Immunotherapeutic effects of recombinant adenovirus encoding interleukin 12 in experimental pulmonary tuberculosis

High dose of Mycobacterium tuberculosis (Mtb) strain H37Rv administered by intratracheal injection in BALB/c mice induce progressive tuberculosis (TB). In this model, during the first month there is a temporal control of bacillary growth, in coexistence with macrophage activation, granuloma formation and Th-1 response. Then, bacterial proliferation recommences, accompanied by progressive pneumonia and decreasing expression of protective cytokines (IFN-γ and TNF-α). In this model, we studied the IL-12 gene expression kinetics and cellular source. There is a rapid and progressive IL-12 expression peaking at day 14, when granulomas start their formation and numerous macrophages show strong IL-12 immunostaining, while during progressive TB there is a significant decrease of IL-12 expression and occasional macrophages showed IL-12 immunolabeling. In the second part of this study, we determined the immunotherapeutic effect of recombinant adenoviruses that codify IL-12 (AdIL-12). Intratracheal administration of only one dose of AdIL-12 one day before Mtb infection produced significant decrease of bacterial loads, lesser pneumonia and higher expression of TNF-α, IFN-γ and iNOS. When only one dose of AdIL-12 was given in healthy mice cohoused with infected mice with highly virulent and transmissible Mtb, total prevention of infection was conferred. Moreover, when AdIL-12 was administered by intranasal route in animals suffering late active TB after 2 months of infection, a very low pulmonary bacilli burdens was detected. These experimental data confirm that IL-12 is a significant cytokine in the immune protection against Mtb, and gene therapy based in adenoviruses coding this cytokine increased protective immunity and prevent Mtb transmission.

Dual role of hypoxia-inducible factor 1 α in experimental pulmonary tuberculosis: its implication as a new therapeutic target

AIM

Investigate the role of hypoxia-inducible factor-1α (HIF-1α) in pulmonary tuberculosis (TB).

METHODS & RESULTS

A model of progressive pulmonary TB in BALB/c mice, immunohistochemistry and digital pathology were used. High HIF-1α expression was observed during early TB in activated macrophages. During late TB, even higher HIF-1α expression was observed in foamy macrophages, which are resistant to apoptosis. Blocking HIF-1α during early infection with 2-methoxyestradiol worsened the disease, while during late TB, it induced macrophage apoptosis and decreased bacillary loads.

CONCLUSION

HIF-1α has a dual role in experimental TB. This finding could have therapeutic implications because combined treatment with 2-methoxyestradiol and antibiotics appeared to eliminate mycobacteria more efficiently than conventional chemotherapy during advanced disease.

Immunogenicity and protection conferred by Mycobacterium habana in a murine model of pulmonary tuberculosis

Mycobacterium habana was isolated in Cuba in 1971. Later, was demonstrated its protection capacity in mycobacterial infection. Here we determined the level of virulence, immunogenicity and the efficacy of three different M. habana strains as attenuated live vaccines. Intratracheal infection of BALB/c mice with high dose M. habana TMC 5135 or IPK-337 strains permitted 100% survival and limited tissue damage. Mice infected with M. habana IPK-220 showed lower attenuation, so it was discarded for the vaccination experiments. Strains IPK-337 and TMC 5135 were used as subcutaneous vaccine and compared with BCG. Nude mice vaccinated with strain 5135 showed longer but non-significant survival than BCG vaccinated animals. Cell suspensions from M. habana vaccinated mice produced higher IFNγ after stimulation with mycobacterial antigens than BCG recipients. After four months of challenge with Mycobacterium tuberculosis strain H37Rv, mice vaccinated with BCG substrain Phipps or strain TMC 5135 showed total survival, while 60% survival was exhibited by animals vaccinated with M. habana IPK-337. Both M. habana strains do not prevent the infection with M. tuberculosis but avoided the progression of the experimental disease; strain TMC 5135 showed similar level of protection than BCG.