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Abstract Spectinamides are a novel class of antibiotics under development for the treatment of MDR- and XDR-tuberculosis, with 1599 and 1445 as early lead candidates within this group. In order to evaluate and differentiate the pharmacological properties of these compounds and assist in candidate selection and design of optimal dosing regimens in animal models of Mtb infection, time kill curve assessments were performed in a previously established in vitro PK/PD model system. The performed studies and subsequent pharmacometric analysis indicate that the anti-mycobacterial activity of 1599 exhibits concentration-dependent killing whereas 1445 shows time-dependent killing. These findings are supported by the fact that the PKPD index that best describes bacterial killing is T > MIC for 1445, but fC max /AUC for 1599. The differential killing behavior among the lead candidates can be rationalized by the differences in post-antibiotic effect: 15.7 h for 1445 compared the 133 h for 1599. Overall, the PK/PD based analysis of the in vitro pharmacologic killing profile of spectinamides 1599 and 1445 on mycobacteria provided valuable insights that contributed to lead candidate selection and preclinical development of these compounds. Graphical abstract Unlabelled Image [ABSTRACT FROM AUTHOR]

Tuberculosis is still a global health burden. It is caused by Mycobacterium tuberculosis which afflicts around one third of the world's population and costs around 1.3 million people their lives every year. Bacillus Calmette-Guerin vaccine is inefficient to prevent overt infection. Additionally, the lengthy inconvenient course of treatment, along with the raising issue of antimicrobial resistance, result in incomplete eradication of this infectious disease. The lack of proper animal models that replicate the latent and active courses of human tuberculosis infection remains one of the main reasons behind the poor advancement in tuberculosis research. Danio rerio, commonly known as zebrafish, is catching more attention as an animal model in tuberculosis research field. This shift is based on the histological and pathological similarities between Mycobacterium marinum infection in zebrafish and Mycobacterium tuberculosis infection in humans. Being small, cheap, transparent, and easy to handle have added further advantages to the use of zebrafish model. Besides better understanding of the pathogenesis of tuberculosis, Mycobacterium marinum infected zebrafish model is useful for evaluating novel vaccines against human tuberculosis, high throughput small molecule screening, repurposing established drugs with possible antitubercular activity, and assessing novel antituberculars for hepatotoxicity. [ABSTRACT FROM AUTHOR]

The main challenge for vaccine development or improvement is the lack of safe adjuvants or immunostimulants that induce protective immune responses and can be used for mucosal immunization, which is a highly desirable strategy for vaccination against infectious diseases acquired by oral or intranasal routes. One promising alternative is the use of biodegradable and biocompatible polymeric microparticles. Recently, we developed an immobilization and delivery system with starch microparticles (SMPs) and a starch-binding domain (SBD tag ) suitable for the mucosal administration of antigens and the induction of antigen-specific immune responses. Here, we explore the immunostimulant and reinforcing potential of the system using BALB/c mice with progressive pulmonary tuberculosis (PPT). The heat shock protein alpha-crystallin from Mycobacterium tuberculosis immobilized on SMPs (µAcr-SBD tag ) or SMPs alone were administered nasally as boosters to BCG-vaccinated mice without any extra adjuvant. The mice were challenged intratracheally with either moderately virulent or highly virulent M. tuberculosis strains. Our results showed that the administration of either the immobilized antigen or SMPs as a booster for the BCG vaccination induced a significant reduction of bacterial loads in the lungs of mice, even more than in mice that received the BCG vaccination alone. Since no difference was observed in pulmonary bacillary burdens between the two reinforced groups, the obtained effect was most likely primarily caused by the starch. As determined by histological study, the administration of boosters did not contribute to the progress of pneumonia, which diminishes the safety concerns related to the administration of SMPs intranasally. Taken together, our findings suggest that this system may be considered as a new carbohydrate-based adjuvant suitable for mucosal vaccines against tuberculosis and other infectious diseases, and more generally, they highlight the potential of particulate α-glucans as immune response modifiers. [ABSTRACT FROM AUTHOR]

New innovative vaccines are highly needed to combat the global threat posed by tuberculosis. Efficient components–antigens and adjuvants–are crucial for development of modern recombinant TB vaccines. This study describes a new vaccine (GamTBvac) consisting of two mycobacterial antigen fusions (Ag85A and ESAT6-CFP10)–with dextran-binding domain immobilized on dextran and mixed with an adjuvant consisting of DEAE-dextran core, and with CpG oligodeoxynucleotides (TLR9 agonists). GamTBvac and its components were assessed for immunogenicity and protective efficacy in GamTBvac-prime/boost and BCG-prime/ GamTBvac-boost in murine and guinea pig TB models. Results show that in both infectious models, GamTBvac has a strong immunogenicity and significant protective effect against Mycobacterium tuberculosis strain H37Rv under aerosol and intravenous challenges. GamTBvac showed a particularly strong protective effect as a BCG booster vaccine. [ABSTRACT FROM AUTHOR]

Infection with Mycobacterium tuberculosis (Mtb) is the leading cause of death in human immunodeficiency virus (HIV)+ individuals, particularly in Sub-Saharan Africa. Management of this deadly co-infection is a significant global health challenge that is exacerbated by the lack of efficient vaccines against both Mtb and HIV, as well as the lack of reliable and robust animal models for Mtb/HIV co-infection. Here we describe a tractable and reproducible mouse model to study the reactivation dynamics of latent Mtb infection following the loss of CD4+ T cells as it occurs in HIV-co-infected individuals. Whereas intradermally (i.d.) infected C57BL/6 mice contained Mtb within the local draining lymph nodes, depletion of CD4+ cells led to progressive systemic spread of the bacteria and induction of lung pathology. To interrogate whether reactivation of Mtb after CD4+ T cell depletion can be reversed, we employed interleukin (IL)-2/anti-IL-2 complex-mediated cell boost approaches. Although populations of non-CD4 lymphocytes, such as CD8+ memory T cells, natural killer (NK) cells and double-negative (DN) T cells significantly expanded after IL-2/anti-IL-2 complex treatment, progressive development of bacteremia and pathologic lung alterations could not be prevented. These data suggest that the failure to reverse Mtb reactivation is likely not due to anergy of the expanded cell subsets and rather indicates a limited potential for IL-2-complex-based therapies in the management of Mtb/HIV co-infection. [ABSTRACT FROM AUTHOR]

Background: Tuberculosis is an infectious disease caused by the Mycobacterium tuberculosis complex has already been identified in a great number of wild species. Captive animals may have a potential source for zoonoses, because is related to factors such as cohabitation, direct contact with the public, presence of biological vectors, nutritional deficiencies, absence of sanitary barriers, precautionary hygienic measures and sanitary vigilance. In Brazil, there is little information on tuberculosis in captivity animals, and little attention is given to the risks of disease transmission from humans. The aim of this study was to report the first diagnosed case of tuberculosis Tapirus terrestris in Brazilian Amazon region. Case: One Tapirus terrestris was kept by local zoobotanic foundation in city of Marabá, Southeast of Pará state, Brazilian Amazon, and became ill. Physical examination revealed cough, sneezing, nasal outflow, dyspnea, hyperthermia and lethargy, leading to death. Necropsy demonstrated severe pulmonary alterations: thickening of the inter-alveolar septa, alveolar emphysema, and miliary nodules with dimensions up to 5 mm, which were yellowish-white, caseous, and sometimes calcified. Additionally, large areas of caseous compaction of the parenchyma, characteristic of caseous tuberculosis. Histopathological analysis revealed a process characteristic of mycobacterial infection, with alveoli filled with caseous exudate and thickened septa and fibrocytes, in addition to recently formed tubercles, some with caseous necrosis, calcifications and Langhans cells. In the Ziehl-Neelsen staining, alcohol-acid resistant bacilli were observed in the mesenteric lymph nodes. No mycobacterial growth was observed in Lowenstein-Jensen culture medium. A nested PCR followed by a sequencing assay targeting the hsp65 gene and M. tuberculosis complex member was detected. Water and M. tuberculosis H37Rv were used as negative and positive controls, respectively. Discussion: This article reports the first case of tuberculosis in T. terrestris in Amazonia. The case of infection was caused by a complex of Mycobacterium tuberculosis, as well as reports of other studies described in wild animals. This record presented clinical and pathological similarity with the cases of a tapir and coati at the zoo of Curitiba, and non-human primates in bioteries in Belém. The disease was reported, also, in a T. indicus female in Bangkok, Thailand. In another study with two tapirs there was positivity of tuberculin test result in a Swedish zoo. In necropsy findings of tuberculosis in a Malayan tapir showed multiple white, caseous nodules spread throughout the lungs. Studies have shown that lesions can be in various organs, among them the mediastinal and mesenteric lymph nodes, liver, spleen, kidneys, ovaries, serosa, diaphragm, intestines and uterus. For exemple in a case of disseminated tuberculosis caused by M. tuberculosis in a Malayan tapir were described multiple granulomes, some coalescent, characterized by necrotic caseous centers, with some Langhans giant cells and a discrete fibrotic zone. In the present work, the results of the anatomopathological and molecular assays confirmed the clinical suspicion of respiratory infection and established the conclusive diagnosis of pulmonary tuberculosis caused by M. tuberculosis complex member. It is worth noting that tuberculosis is an important zoonotic disease affecting survival of the species, posing an extinction threat and also a public health concern. [ABSTRACT FROM AUTHOR]

Non-human primates, primarily macaques, have been used to study tuberculosis for decades. However, in the last 15 years, this model has been refined substantially to allow careful investigations of the immune response and host-pathogen interactions in Mycobacterium tuberculosis infection. Low-dose challenge with fully virulent strains in cynomolgus macaques result in the full clinical spectrum seen in humans, including latent and active infection. Reagents from humans are usually cross-reactive with macaques, further facilitating the use of this model system to study tuberculosis. Finally, macaques develop the spectrum of granuloma types seen in humans, providing a unique opportunity to investigate bacterial and host factors at the local (lung and lymph node) level. Here, we review the past decade of immunology and pathology studies in macaque models of tuberculosis. [ABSTRACT FROM AUTHOR]

Despite the availability of Mycobacterium tuberculosis (Mtb) drugs for over 50 years, tuberculosis ( TB) remains at pandemic levels. New drugs are urgently needed for resistant strains, shortening duration of treatment, and targeting different stages of the disease, especially for treatment during human immunodeficiency virus co-infection. One solution to the conundrum that antibiotics kill the bacillus yet select for resistance is to target the host rather than the pathogen. Here, we discuss recent progress in so-called 'host-directed therapeutics' ( HDTs), focusing on two general mechanistic strategies: (i) HDTs that disrupt Mtb pathogenesis in macrophages and (ii) immunomodulatory HDTs that facilitate protective immune responses that kill Mtb or reduce deleterious responses that exacerbate disease. HDTs hold significant promise as adjunctive therapies in that they are less likely to engender resistance, will likely have efficacy against antibiotic-resistant strains, and may have activity against non-replicating Mtb. However, TB is a complex and variegated disease, and human populations exhibit significant diversity in their immune responses to it, which presents a complicated landscape for HDTs to navigate. Nevertheless, we suggest that a detailed mechanistic understanding of drug action, together with careful selection of disease stage targets and dosing strategies may overcome such limitations and allow the development of HDTs as effective adjunctive treatment options for TB. [ABSTRACT FROM AUTHOR]

The expression of ten tuberculosis candidate genes in lung and lymph nodes of cynomologus macaques vaccinated and experimentally infected with Mycobacterium tuberculosis (Mtb) was quantified. The expression of TNFα, IL10, IL1β, TLR4, IL17, IL6, IL12, and iNOS in the lungs of vaccinated animals was higher than that of non-vaccinated animals. [ABSTRACT FROM AUTHOR]

Abstract: In this review, published peer-reviewed preclinical studies using prime-boost tuberculosis (TB) vaccine regimens in animal challenge models for tuberculosis have been evaluated. These studies have been divided into groups that describe prime-boost vaccine combinations that performed better than, equivalent to, or worse than the currently used BCG vaccine. Review of the data has revealed interesting findings, including that more than half of the published studies using BCG as a prime combined with a novel boost vaccine give better efficacy than BCG alone and that the greatest reduction in Mycobacterium tuberculosis (M.tb.) colonization of animal tissues is provided by viral vectored vaccines delivered intranasally. Careful evaluation of these data should assist in defining the value of prime-boost regimens for advancement into human TB vaccine trials and stimulate the development of criteria for choosing which vaccine candidates should be studied further. [Copyright &y& Elsevier]

Abstract: In vitro, Toll-like receptors (TLR)2, 4 and 9 as well as NOD-like receptor 2 critically determine macrophage responses to Mycobacterium tuberculosis (Mtb) infection. However, in low-dose experimental murine tuberculosis, single or multiple deficiencies in TLRs 2, 4, 9 or NOD2 have little, if any, impact on early mycobacterial growth containment, granuloma formation and survival. Here, we analyzed the relevance of NALP3, one component of the danger-signaling inflammasome, for (i) Mtb-induced cytokine secretion in vitro and in vivo, (ii) restriction of Mtb replication in infected organs and (iii) granuloma formation. In the absence of functional NALP3, there was no IL-1β and IL-18 production in Mtb-infected dendritic cells and macrophages in vitro, whereas secretion of IL-1α, IL-12p40 and TNF remained unaffected. After three weeks of infection, NALP3-deficient as well as IL-18-deficient mice were as capable as wildtype mice of restricting Mtb loads at a plateau level within well-differentiated granulomas. In conclusion, despite its involvement in cytokine processing, NALP3 is not essential for induction of protective immunity to Mtb. [ABSTRACT FROM AUTHOR]

Abstract: In order to determine the relative importance of fucosyltransferase (Fuc-T)-directed functionalization of selectin ligands for chronic inflammatory and antibacterially protective responses in vivo, mice selectively deficient for Fuc-TIV, Fuc-TVII or both were infected by aerosol with Mycobacterium tuberculosis H37Rv. Fuc-TIV/Fuc-TVII-deficient, and to a lesser extent, Fuc-TVII-deficient mice succumbed significantly faster to infection than Fuc-TIV-deficient and wildtype (WT) mice, although no differentially increased bacterial load or qualitatively different histopathology was apparent in moribund mice. To determine if the cause of accelerated death was associated with defective induction of immune responses in the lung due to the diminished T cell content in the mediastinal lymph nodes of Fuc-T-deficient mice, intravenous infection in WT or double-deficient mice was performed. Again, Fuc-TIV/Fuc-TVII mice succumbed significantly faster than WT mice. To determine whether the early demise of Fuc-TIV/Fuc-TVII-deficient mice was due to accelerated tissue pathology, a mouse model of mycobacteria-induced granuloma necrosis was used. There was no difference in the kinetics and quality of caseation induced by Mycobacterium avium TMC724 in all mouse strains investigated. Together, our data show that a deficiency in Fuc-TVII, and in a more pronounced fashion, a combined deficiency in both Fuc-TIV and Fuc-TVII, leads to accelerated death following M. tuberculosis infection that is neither caused by increased bacterial proliferation nor by discernibly gross differences in tissue pathology. These results suggest that targeting selectin ligand function during treatment of chronic inflammatory disorders may run the risk of accelerating TB disease progression. [Copyright &y& Elsevier]