Adenoviral Vector Codifying for TNF as a Co-Adjuvant Therapy against Multi-Drug-Resistant Tuberculosis

Mycobacterium tuberculosis is the main causal agent of pulmonary tuberculosis (TB); the treatment of this disease is long and involves a mix of at least four different antibiotics that frequently lead to abandonment, favoring the surge of drug-resistant mycobacteria (MDR-TB), whose treatment becomes more aggressive, being longer and more toxic. Thus, the search for novel strategies for treatment that improves time or efficiency is of relevance. In this work, we used a murine model of pulmonary TB produced by the MDR-TB strain to test the efficiency of gene therapy with adenoviral vectors codifying TNF (AdTNF), a pro-inflammatory cytokine that has protective functions in TB by inducing apoptosis, granuloma formation and expression of other Th1-like cytokines. When compared to the control group that received an adenoviral vector that codifies for the green fluorescent protein (AdGFP), a single dose of AdTNF at the chronic active stage of the disease produced total survival, decreasing bacterial load and tissue damage (pneumonia), which correlated with an increase in cells expressing IFN-γ, iNOS and TNF in pneumonic areas and larger granulomas that efficiently contain and eliminate mycobacteria. Second-line antibiotic treatment against MDR-TB plus AdTNF gene therapy reduced bacterial load faster within a week of treatment compared to empty vector plus antibiotics or antibiotics alone, suggesting that AdTNF is a new potential type of treatment against MDR-TB that can shorten second-line chemotherapy but which requires further experimentation in other animal models (non-human primates) that develop a more similar disease to human pulmonary TB.

The Use of Viral Vectors for Gene Therapy and Vaccination in Tuberculosis

Tuberculosis (TB), an infection caused by Mycobacterium tuberculosis (Mtb), is one of the primary causes of death globally. The treatment of TB is long and based on several drugs, producing problems in compliance and toxicity, increasing Mtb resistance to first-line antibiotics that result in multidrug-resistant TB and extensively drug-resistant TB. Thus, the need for new anti-TB treatments has increased. Here, we review some model strategies to study gene therapy based on the administration of a recombinant adenovirus that encodes diverse cytokines, such as IFNγ, IL12, GM/CSF, OPN, TNFα, and antimicrobial peptides to enhance the protective immune response against Mtb. These models include a model of progressive pulmonary TB, a model of chronic infection similar to latent TB, and a murine model of pulmonary Mtb transmission to close contacts. We also review new vaccines that deliver Mtb antigens via particle- or virus-based vectors and trigger protective immune responses. The results obtained in this type of research suggest that this is an alternative therapy that has the potential to treat active TB as an adjuvant to conventional antibiotics and a promising preventive treatment for latent TB reactivation and Mtb transmission. Moreover, Ad vector vaccines are adequate for preventing infectious diseases, including TB.

The Use of Particulate Systems for Tuberculosis Prophylaxis and Treatment: Opportunities and Challenges

The use of particles to develop vaccines and treatments for a wide variety of diseases has increased, and their success has been demonstrated in preclinical investigations. Accurately targeting cells and minimizing doses and adverse side effects, while inducing an adequate biological response, are important advantages that particulate systems offer. The most used particulate systems are liposomes and their derivatives, immunostimulatory complexes, virus-like particles, and organic or inorganic nano- and microparticles. Most of these systems have been proven using therapeutic or prophylactic approaches to control tuberculosis, one of the most important infectious diseases worldwide. This article reviews the progress and current state of the use of particles for the administration of TB vaccines and treatments in vitro and in vivo, with a special emphasis on polymeric particles. In addition, we discuss the challenges and benefits of using these particulate systems to provide researchers with an overview of the most promising strategies in current preclinical trials, offering a perspective on their progress to clinical trials.

Immune regulatory effect of osteopontin gene therapy in a murine model of multi-drug resistant pulmonary tuberculosis

Tuberculosis (TB) has been for many years a major public health problem since treatment is long and sometimes ineffective favoring the increase of multi-drug-resistant mycobacteria (MDR). Gene therapy is a novel and effective tool to regulate immune responses. In this study we evaluated the therapeutic effect of an adenoviral vector codifying osteopontin (AdOPN), a molecule known for their roles to favour Th1 and Th17 type-cytokine expression which are crucial in TB containment. A single-dose of AdOPN administration in BALB/c mice suffering late progressive pulmonary MDR-TB, produced significant lower bacterial load and pneumonia, due to higher expression of IFN-γ, IL-12 and IL-17 in coexistence with increase of granulomas in number and size, resulting in higher survival, in contrast with mice treated with the control adenovirus that codify the green fluorescent protein (AdGFP). Combined therapy of AdOPN with a regimen of 2nd line antibiotics produced a better control of bacterial load in lung during the first days of treatment, suggesting that AdOPN can shorten chemotherapy. Taken together, gene therapy with AdOPN leads to higher immune responses against TB infection, resulting in a new potential treatment against pulmonary TB that can co-adjuvant chemotherapy.

Evaluation of a virulent strain of Mycobacterium avium subsp. Paratuberculosis used as a heat-killed vaccine

Bovine paratuberculosis is one of the most important chronic infectious diseases in livestock. This disease is difficult to control because of its inefficient management (test and cull strategy and inadequate biosecurity). Thus, the development of an effective vaccine is essential. In this study, we evaluated a local virulent strain (6611) of Mycobacterium avium subsp. paratuberculosis as an inactivated vaccine in comparison with the Silirum vaccine in mouse model and cattle. Regarding the mice model, only the groups vaccinated with 6611 showed lower colony forming unit (CFU) counts with a lower lesion score in the liver in comparison to the control group at 6 and 12 weeks post-challenge (wpc). The immune response was predominantly humoral (IgG1), although both vaccinated groups presented a cellular response with IFNγ production as well, but the 6611 group had also significant production of IL-2, IL-6, IL-17a, TNF, and IL-10. In cattle, the 6611 vaccinated group was the only one that maintained significant antibody values at the end of the trial, with significant production of IgG2 and IFNγ. No PPDb reactor was detected in the vaccinated animals, according to the intradermal caudal fold tuberculin test. Our results indicate that the 6611 local strain protected mice from challenge with a virulent strain, by inducing a humoral and cellular immune response. In the bovine, the natural host, the evaluated vaccine also induced humoral and cellular immune responses, with higher levels of CD4 + CD25+ and CD8 + CD25+ T cells populations than the commercial vaccine. Despite the encouraging results obtained in this study, an experimental challenge trial in cattle is mandatory to evaluate the efficacy of our candidate vaccine in the main host.

Inhibition of Chlamydial Infection by CRISPR/Cas9-SAM Mediated Enhancement of Human Peptidoglycan Recognition Proteins Gene Expression in HeLa Cells

The global problem of emerging resistance of microorganisms to antibiotics makes the search for new natural substances with antibacterial properties relevant. Such substances include peptidoglycan recognition proteins (PGLYRP), which are the components of the innate immunity of many organisms, including humans. These proteins have a unique mechanism of action that allows them to evade the resistance of bacteria to them, as well as to be active against both Gram-positive and Gram-negative bacteria. However, the use of antimicrobial recombinant proteins is not always advisable due to the complexity of local delivery of the proteins and their stability; in this regard it seems appropriate to activate the components of the innate immunity. The aim of this study was to increase the expression level of native peptidoglycan recognition protein genes in HeLa cells using genome-editing technology with synergistic activation mediators (CRISPR/Cas9-SAM) and evaluate antichlamydial effect of PGLYRP. We demonstrated activation of the chlamydial two-component gene system (ctcB-ctcC), which played a key role in the mechanism of action of the peptidoglycan recognition proteins. We generated the HeLa cell line transduced with lentiviruses encoding CRISPR/Cas9-SAM activation system with increased PGLYRP gene expression. It was shown that activation of the own peptidoglycan recognition proteins gene expression in the cell line caused inhibition of the chlamydial infection development. The proposed approach makes it possible to use the capabilities of innate immunity to combat infectious diseases caused by Gram-positive and Gram-negative bacteria.

Understanding the Reciprocal Interplay Between Antibiotics and Host Immune System: How Can We Improve the Anti-Mycobacterial Activity of Current Drugs to Better Control Tuberculosis?

Tuberculosis (TB), caused by Mycobacterium tuberculosis (Mtb) infection, remains a global health threat despite recent advances and insights into host-pathogen interactions and the identification of diverse pathways that may be novel therapeutic targets for TB treatment. In addition, the emergence and spread of multidrug-resistant Mtb strains led to a low success rate of TB treatments. Thus, novel strategies involving the host immune system that boost the effectiveness of existing antibiotics have been recently suggested to better control TB. However, the lack of comprehensive understanding of the immunomodulatory effects of anti-TB drugs, including first-line drugs and newly introduced antibiotics, on bystander and effector immune cells curtailed the development of effective therapeutic strategies to combat Mtb infection. In this review, we focus on the influence of host immune-mediated stresses, such as lysosomal activation, metabolic changes, oxidative stress, mitochondrial damage, and immune mediators, on the activities of anti-TB drugs. In addition, we discuss how anti-TB drugs facilitate the generation of Mtb populations that are resistant to host immune response or disrupt host immunity. Thus, further understanding the interplay between anti-TB drugs and host immune responses may enhance effective host antimicrobial activities and prevent Mtb tolerance to antibiotic and immune attacks. Finally, this review highlights novel adjunctive therapeutic approaches against Mtb infection for better disease outcomes, shorter treatment duration, and improved treatment efficacy based on reciprocal interactions between current TB antibiotics and host immune cells.

Immunotherapeutic effect of adenovirus encoding antimicrobial peptides in experimental pulmonary tuberculosis

As components of the innate immune response, antimicrobial peptides (AMPs) efficiently contribute to infection control and maintenance of a latent state in pulmonary tuberculosis (TB). As a therapeutic strategy, the administration of recombinant AMPs could be limited by enzymatic degradation and high production costs. Likewise, strategies based on the induction of AMPs have generated controversial results. In this study, 2 recombinant type-5 adenoviruses (Ad) expressing the human β-defensin 3 (HβD3) or cathelicidin (LL37) were assessed in a murine pulmonary TB model. Mice infected with either a high dose of a drug-sensitive (H37Rv) or a multidrug-resistant (MDR) strain of Mycobacterium tuberculosis (Mtb) were treated with a single administration of AdHβD3, AdLL37, AdGFP (control vector expressing a green fluorescent protein), or saline solution (SS). Lungs were obtained to determine the bacterial burden, histologic damage, and cytokine expression at different time points. Mice treated with AdHβD3 or AdLL37 showed significantly lower bacterial load and pneumonia, and higher proinflammatory cytokine expression than the control groups AdGFP and SS. A synergistic therapeutic effect could be observed when first- or second-line antibiotics (ABs) were administered with adenoviral therapy in animals infected with H37Rv or MDR strains, respectively. Adenovirus-delivered AMP's administration constitutes a promising adjuvant therapy for current anti-TB drugs by enhancing a protective immune response and potentially reducing current AB regimes' duration.

Evaluation of Direct and Cell-Mediated Lactoferrin Gene Therapy for the Maxillofacial Area Abscesses in Rats

Resistance to antibacterial therapy requires the discovery of new methods for the treatment of infectious diseases. Lactoferrin (LTF) is a well-known naïve first-line defense protein. In the present study, we suggested the use of an adenoviral vector (Ad5) carrying the human gene encoding LTF for direct and cell-mediated gene therapy of maxillofacial area phlegmon in rats. Abscesses were developed by injection of the purulent peritoneal exudate in the molar region of the medial surface of the mandible. At 3-4 days after phlegmon maturation, all rats received ceftriaxone and afterward were subcutaneously injected around the phlegmon with: (1) Ad5 carrying reporter gfp gene encoding green fluorescent protein (Ad5-GFP control group), (2) Ad5 carrying LTF gene (Ad5-LTF group), (3) human umbilical cord blood mononuclear cells (UCBC) transduced with Ad5-GFP (UCBC + Ad5-GFP group), and (4) UCBC transduced with Ad5-LTF (UCBC + Ad5-LTF group). Control rats developed symptoms considered to be related to systemic inflammation and were euthanized at 4-5 days from the beginning of the treatment. Rats from therapeutic groups demonstrated wound healing and recovery from the fifth to seventh day based on the type of therapy. Histological investigation of cervical lymph nodes revealed purulent lymphadenitis in control rats and activated lymphatic tissue in rats from the UCBC + Ad5-LTF group. Our results propose that both approaches of LTF gene delivery are efficient for maxillofacial area phlegmon recovery in rats. However, earlier wound healing and better outcomes in cervical lymph node remodeling in the UCBC + Ad5-LTF group, as well as the lack of direct exposure of the viral vector to the organism, which may cause toxic and immunogenic effects, suggest the benefit of cell-mediated gene therapy.

Evidence that changes in antimicrobial peptides during tuberculosis are related to disease severity, clinical presentation, specific therapy and levels of immune-endocrine mediators

Given the role of host defense peptides (HDPs) in the defensive response against mycobacteria, we analyzed the circulating levels of LL-37, β-defensin-2 and -3 in newly diagnosed patients with pulmonary (PTB) or pleural tuberculosis (PLTB) in whom measurements of pleural fluids were also performed. Severe PTB patients displayed higher circulating amounts of β-defensin-3, statistically different from controls, further decreasing upon antimycobacterial treatment. LL-37 concentrations appeared within the normal range at diagnosis, but tended to increase during treatment, becoming statistically upon its completion in moderate cases. PLTB patients revealed decreased levels of β-defensin-2 in presence of increased amounts of β-defensin-3 and LL-37; in their plasma or pleural fluids. Considering the immune-endocrine dysregulation of tuberculosis, we also performed correlation analysis detecting positive associations between levels of cortisol, IL-6 and β-defensin-3 in plasma from untreated severe patients as did their dehydroepiandrosterone and LL-37 values. Increased presence of β-defensins, may represent an attempt to improve defensive mechanisms; which also take part in the inflammatory reaction accompanying TB, reinforced by the association with immune-endocrine mediators. The divergent profile of PLTB patients, decreased β-defensin-2 but increased β-defensin-3 and LL-37 levels, suggests a differential role of these HDPs in a situation characterized for its better protective response.

The use of immunotherapy for the treatment of tuberculosis

INTRODUCTION

Tuberculosis (TB) is the first cause of mortality by a single infectious agent in the world, causing more than one million deaths worldwide as reported by the World Health Organization (WHO). For the optimal control of TB infection, a protective immune response that limits bacterial spread without causing damage to the host is essential. Although most healthy individuals are capable of generating protective responses, patients who suffer pulmonary TB commonly present a defective immune function. Areas covered: We intend to highlight the potential of novel immunotherapeutic strategies that enhance and promote effective immune responses. The following methodology was undertaken for establishing a literature search: the authors used PubMed to search for 'Pulmonary Tuberculosis' and keywords that denoted the novel immunotherapeutic strategies discussed in length in the text including antibodies, antimicrobial peptides, cell therapy, cytokines and gene therapy. Expert commentary: The current therapeutic regimens for this disease are complex and involve the prolonged use of multiple antibiotics with diverse side effects that lead to therapeutic failure and bacterial resistance. The standard appliance of immunotherapy and its deployment to vulnerable populations will require coordinated work and may serve as a powerful tool to combat the ensuing threat of TB.

Host Antimicrobial Peptides: The Promise of New Treatment Strategies against Tuberculosis

Tuberculosis (TB) continues to be a devastating infectious disease and remerges as a global health emergency due to an alarming rise of antimicrobial resistance to its treatment. Despite of the serious effort that has been applied to develop effective antitubercular chemotherapies, the potential of antimicrobial peptides (AMPs) remains underexploited. A large amount of literature is now accessible on the AMP mechanisms of action against a diversity of pathogens; nevertheless, research on their activity on mycobacteria is still scarce. In particular, there is an urgent need to integrate all available interdisciplinary strategies to eradicate extensively drug-resistant Mycobacterium tuberculosis strains. In this context, we should not underestimate our endogenous antimicrobial proteins and peptides as ancient players of the human host defense system. We are confident that novel antibiotics based on human AMPs displaying a rapid and multifaceted mechanism, with reduced toxicity, should significantly contribute to reverse the tide of antimycobacterial drug resistance. In this review, we have provided an up to date perspective of the current research on AMPs to be applied in the fight against TB. A better understanding on the mechanisms of action of human endogenous peptides should ensure the basis for the best guided design of novel antitubercular chemotherapeutics.

The Role of Mast Cells in Tuberculosis: Orchestrating Innate Immune Crosstalk?

Tuberculosis causes more annual deaths globally than any other infectious disease. However, progress in developing novel vaccines, diagnostics, and therapies has been hampered by an incomplete understanding of the immune response to Mycobacterium tuberculosis (Mtb). While the role of many immune cells has been extensively explored, mast cells (MCs) have been relatively ignored. MCs are tissue resident cells involved in defense against bacterial infections playing an important role mediating immune cell crosstalk. This review discusses specific interactions between MCs and Mtb, their contribution to both immunity and disease pathogenesis, and explores their role in orchestrating other immune cells against infections.

Opening Pandora's Box: Mechanisms of Mycobacterium tuberculosis Resuscitation

Mycobacterium tuberculosis (Mtb) characteristically causes an asymptomatic infection. While this latent tuberculosis infection (LTBI) is not contagious, reactivation to active tuberculosis disease (TB) causes the patient to become infectious. A vaccine has existed for TB for a century, while drug treatments have been available for over 70 years; despite this, TB remains a major global health crisis. Understanding the factors which allow the bacillus to control responses to host stress and mechanisms leading to latency are critical for persistence. Similarly, molecular switches which respond to reactivation are important. Recently, research in the field has sought to focus on reactivation, employing system-wide approaches and animal models. Here, we describe the current work that has been done to elucidate the mechanisms of reactivation and stop reactivation in its tracks.

Activity of human beta defensin-1 and its motif against active and dormant Mycobacterium tuberculosis

The ineffectiveness of anti-tuberculous therapy against dormant and drug-resistant mycobacteria demands scrutiny of alternative candidates like antimicrobial peptides having different mechanisms of action. The present study was designed to explore the activity of human beta defensin-1 (HBD-1) and its in silico identified short motif Pep-B against active and dormant Mycobacterium tuberculosis (M. tb) H37Rv. Activity of HBD-1 and Pep-B was determined against actively growing M. tb in vitro, inside monocyte-derived macrophages (MDMs) and dormant bacilli in in vitro potassium deficiency and human peripheral blood mononuclear cell (PBMC) granuloma models using colony-forming unit enumeration. The minimum inhibitory concentrations (MIC) of HBD-1 and Pep-B were found to be 2 and 20 μg/ml, respectively. These peptides also inhibited intracellular mycobacterial growth at concentrations lower than in vitro MICs along with increased IFN-γ levels. Although at higher concentration, HBD-1 (× 2 MIC) and Pep-B (× 2 MIC) led to decrease in in vitro dormant mycobacterial load as compared to rifampicin (× 25 MIC) and isoniazid (× 16 MIC). Similarly, both peptides showed higher killing efficacy against dormant mycobacteria inside granuloma as compared to rifampicin. Thus, the present study indicates that HBD-1 and its motif are effective antimicrobial players against both actively growing and dormant mycobacteria.