Association Between Vitamin D Insufficiency and Impaired Bone Density Among Adolescents With Perinatally Acquired HIV Infection

Background

Stunting and pubertal delay are common among children growing up with human immunodeficiency virus (HIV) and are associated with bone and muscle impairments. We investigated factors associated with bone density and muscle function in adolescents living with HIV (ALWH).

Methods

The VITALITY trial (PACTR202009897660297) investigated whether vitamin D and calcium supplementation improves musculoskeletal health among ALWH. A total of 842 ALWH aged 11-19 years, established on antiretroviral therapy (ART) for ≥6 months, were enrolled from HIV clinics in Zambia and Zimbabwe. Clinical history and examination were undertaken, and serum 25-hydroxyvitamin D3 (25[OH]D3) was measured. Dual-energy X-ray absorptiometry measured total-body-less-head bone mineral density adjusted for height (TBLH-BMDHT), and lumbar spine bone mineral apparent density (LS-BMAD) z scores. The association between a priori-defined covariates and musculoskeletal outcomes were investigated using baseline enrollment data and multivariable logistic regression.

Results

TBLH-BMDHT  z scores were impaired (mean, -1.42 for male and -0.63 female participants), as were LS-BMAD z scores (mean -1.15 for male and -0.47 for female participants). In bivariate analysis, early pubertal stage, less physical activity, and older age at ART initiation were associated with lower TBLH-BMDHT  z scores. Younger age, early pubertal stage, and low socioeconomic status were associated with lower LS-BMAD z scores. Grip-strength-for-height and jump-power-for-height z scores were associated with lower TBLH-BMDHT and LS-BMAD z scores. Low dietary vitamin D and calcium were associated with lower adjusted TBLH-BMDHT  z scores. Lower 25(OH)D3 was associated with lower adjusted TBLH-BMDHT and LS-BMAD z scores.

Conclusions

Deficits in bone density are common in ALWH. Vitamin D and calcium supplementation and promotion of exercise may improve musculoskeletal health among perinatally infected ALWH.

Microbiota alterations in patients treated for susceptible or drug-resistant TB

BACKGROUND

We investigated alterations of human microbiota under anti-TB therapies in relationship to the level of Mycobacterium tuberculosis drug response.

METHODS

Stool, sputum, and oral swab samples were analysed from participants with treatment-naïve TB and participants treated for drug-susceptible TB (DS-TB), drug-resistant TB without injectable drugs (DR-TB-inj-), or with injectable drugs (DR-TB-inj+) at 27-42 days of therapy.

RESULTS

From September 2018 to December 2019, 5 participants with treatment-naïve TB, 6 participants with DS-TB, 10 participants with DR-TB-inj-, and 4 participants with DR-TB-inj+ were recruited. Reduced alpha diversities in stool samples indicated more profound dysbiosis in participants treated for DR-TB than in participants treated for DS-TB (-12% (non-significant) for DS-TB, -44% (P < 0.001) for DR-TB-inj-, and -60% (P < 0.05) for DR-TB-inj+ compared to treatment-naïve participants). While reduced abundances were observed in numerous taxa, genus Lactobacillus revealed the most substantial abundance increase in sputa of participants treated for DR-TB compared to treatment-naïve ones (P < 0.05 for DR-TB-inj- and DR-TB-inj+). Notably, a group of nosocomial pneumonia-associated taxa was increased in oral swabs of the DR-TB-inj+ compared to the treatment-naïve group (P < 0.05).

CONCLUSIONS

Second-line anti-TB therapy in participants with DR-TB results in altered microbiota, including reduced alpha diversity and expansion of phylogenetically diverse taxa, including pathobionts.

Update: Vitamin D3 and calcium carbonate supplementation for adolescents with HIV to reduce musculoskeletal morbidity and immunopathology (VITALITY trial): study protocol for a randomised placebo-controlled trial

BACKGROUND

Of the 2 million children living with HIV globally, 90% live in sub-Saharan Africa. Despite antiretroviral therapy, longstanding HIV infection is associated with several chronic complications in children including growth failure, particularly stunting and delayed puberty. Vitamin D deficiency, which is highly prevalent among children living with HIV in sub-Saharan Africa, has further adverse impact on bone health. This trial aims to establish whether supplementation with vitamin D3 and calcium carbonate improves musculoskeletal health among peripubertal children living with HIV. This paper is an update to an already existing protocol that was previously published in Trials in 2022 and details changes in the trial outcomes.

METHODS/DESIGN

We will conduct an individually randomised, double-blinded, placebo-controlled trial of weekly high-dose vitamin D3 (20,000 IU) plus daily calcium carbonate (500 mg) supplementation for 48 weeks. Eight hundred and forty children living with HIV aged 11-19 years taking ART for ≥ 6 months will be enrolled and followed up for 96 weeks. The primary outcome is DXA-measured total body less-head bone mineral density Z-score (TBLH-BMD) at 48 weeks and is an update to the previous primary outcome total body less-head bone mineral content adjusted for lean mass (TBLH-BMCLBM) Z-score. The primary outcome was updated to address the substantial differences in distributions of TBLH-BMCLBM Z-score between the two sites as a result of software differences of the DXA machines. Secondary outcomes are DXA-measured TBLH-BMD Z-score adjusted for height at 48 weeks a new secondary outcome, lumbar spine bone mineral apparent density Z-score, number of respiratory infections, lean muscle mass and grip-strength at 48 and 96 weeks, and TBLH-BMD Z-score at 96 weeks. Sub-studies will investigate the effect of the intervention on vitamin D3 pathway metabolites and markers of bone turnover, intestinal microbiota, and innate and acquired immune function.

DISCUSSION

This is the largest trial to date of vitamin D supplementation in children living with HIV. Intervening to address deficits in bone accrual through childhood is critical for optimising adolescent and early adult bone health, and prevention of later adult osteoporotic fractures. Trial results will draw attention to the need to screen for and treat long-term comorbidities in children living with HIV in resource-limited settings.

TRIAL REGISTRATION

Pan African Clinical Trials Registry PACTR20200989766029. Registered on September 3, 2020. URL of trial registry record: https://pactr.samrc.ac.za TRIAL STATUS: Participant follow-up completed; data analysis ongoing.

L-Thyroxine and L-thyroxine-based antimicrobials against Streptococcus pneumoniae and other Gram-positive bacteria

Objectives

The rise of antibiotic-resistant Streptococcus pneumoniae (Sp) poses a significant global health threat, urging the quest for novel antimicrobial solutions. We have discovered that the human hormone l-thyroxine has antibacterial properties. In order to explore its drugability we perform here the characterization of a series of l-thyroxine analogues and describe the structural determinants influencing their antibacterial efficacy.

Method

We performed a high-throughput screening of a library of compounds approved for use in humans, complemented with ITC assays on purified Sp-flavodoxin, to pinpoint molecules binding to this protein. Antimicrobial in vitro susceptibility assays of the hit compound (l-thyroxine) as well as of 13 l-thyroxine analogues were done against a panel of Gram-positive and Gram-negative bacteria. Toxicity of compounds on HepG2 cells was also assessed. A combined structure-activity and computational docking analysis was carried out to uncover functional groups crucial for the antimicrobial potency of these compounds.

Results

Human l-thyroxine binds to Sp-flavodoxin, forming a 1:1 complex of low micromolar Kd. While l-thyroxine specifically inhibited Sp growth, some derivatives displayed activity against other Gram-positive bacteria like Staphylococcus aureus and Enterococcus faecalis, while remaining inactive against Gram-negative pathogens. Neither l-thyroxine nor some selected derivatives exhibited toxicity to HepG2 cells.

Conclusions

l-thyroxine derivatives targeting bacterial flavodoxins represent a new and promising class of antimicrobials.

The Mla system and its role in maintaining outer membrane barrier function in Stenotrophomonas maltophilia

Stenotrophomonas maltophilia are ubiquitous Gram-negative bacteria found in both natural and clinical environments. It is a remarkably adaptable species capable of thriving in various environments, thanks to the plasticity of its genome and a diverse array of genes that encode a wide range of functions. Among these functions, one notable trait is its remarkable ability to resist various antimicrobial agents, primarily through mechanisms that regulate the diffusion across cell membranes. We have investigated the Mla ABC transport system of S. maltophilia, which in other Gram-negative bacteria is known to transport phospholipids across the periplasm and is involved in maintaining outer membrane homeostasis. First, we structurally and functionally characterized the periplasmic substrate-binding protein MlaC, which determines the specificity of this system. The predicted structure of the S. maltophilia MlaC protein revealed a hydrophobic cavity of sufficient size to accommodate the phospholipids commonly found in this species. Moreover, recombinant MlaC produced heterologously demonstrated the ability to bind phospholipids. Gene knockout experiments in S. maltophilia K279a revealed that the Mla system is involved in baseline resistance to antimicrobial and antibiofilm agents, especially those with divalent-cation chelating activity. Co-culture experiments with Pseudomonas aeruginosa also showed a significant contribution of this system to the cooperation between both species in the formation of polymicrobial biofilms. As suggested for other Gram-negative pathogenic microorganisms, this system emerges as an appealing target for potential combined antimicrobial therapies.

Stenotrophomonas maltophilia affects the gene expression profiles of the major pathogens Pseudomonas aeruginosa and Staphylococcus aureus in an in vitro multispecies biofilm model

IMPORTANCE

In the past, studies have focused on bacterial pathogenicity in mono-species infections, in part ignoring the clinical relevance of diseases caused by more than one pathogen (i.e., polymicrobial infections). However, it is now common knowledge that multiple bacteria species are often involved in the course of an infection. For treatment of such infections, it is absolutely important to understand the dynamics of species interactions at possible infection sites and the molecular mechanisms behind these interactions. Here, we studied the impact of Stenotrophomonas maltophilia on its commensals Pseudomonas aeruginosa and Staphylococcus aureus in multispecies biofilms. We analyzed the 3D structural architectures of dual- and triple-species biofilms, niche formation within the biofilms, and the interspecies interactions on a molecular level. RNAseq data identified key genes involved in multispecies biofilm formation and interaction as potential drug targets for the clinical combat of multispecies infection with these major pathogens.

tet-Dependent Gene Expression in Stenotrophomonas maltophilia

Stenotrophomonas maltophilia is increasingly recognized as an important nosocomial pathogen among the Gram-negative bacteria. Intrinsic resistance to different classes of antibiotics makes treatment of infections challenging. A deeper understanding of S. maltophilia physiology and virulence requires molecular genetic tools. Here, we describe the implementation of tetracycline-dependent gene regulation (tet regulation) in this bacterium. The exploited tet regulatory sequence of transposon Tn10 contained the tetR gene and three intertwined promoters, one of which was required for regulated expression of a target gene or operon. The episomal tet architecture was tested with a gfp variant as a quantifiable reporter. Fluorescence intensity was directly correlated with the concentration of the inducer anhydrotetracycline (ATc) applied and the duration of induction. Also, the expression of the rmlBACD operon of S. maltophilia K279a was subjected to tet control. These genes code for the synthesis of dTDP-l-rhamnose, an activated nucleotide sugar precursor of lipopolysaccharide (LPS) formation. A ΔrmlBACD mutant was complemented with a plasmid carrying this operon downstream of the tet sequence. In the presence of ATc, the LPS pattern was similar to that of wild-type S. maltophilia, whereas without the inducer, fewer and apparently shorter O-antigen chains were detected. This underscores the functionality and usefulness of the tet system for gene regulation and, prospectively, the validation of targets for new anti-S. maltophilia drugs. IMPORTANCE Stenotrophomonas maltophilia is an emerging pathogen in hospital settings and poses a threat to immunocompromised patients. Due to a high level of resistance to different types of antibiotics, treatment options are limited. We here adapted a tool for inducible expression of genes of interest, known as the tet system, to S. maltophilia. Genes relevant to producing surface carbohydrate structures (lipopolysaccharide [LPS]) were placed under the control of the tet system. In the presence of an inducer, the LPS pattern was similar to that of wild-type S. maltophilia, whereas in the "off" state of the system (without inducer), fewer and apparently shorter versions of LPS were detected. The tet system is functional in S. maltophilia and may be helpful to reveal gene-function relationships to gain a deeper understanding of the bacterium's physiology and virulence.

Amorphous Drug Nanoparticles for Inhalation Therapy of Multidrug-Resistant Tuberculosis

Tuberculosis (TB) is one of the most prevalent infectious diseases. The global TB situation is further complicated by increasing patient numbers infected with Mycobacterium tuberculosis (M.tb.) strains resistant to either one or two of the first-line therapeutics, promoted by insufficient treatment length and/or drug levels due to adverse reactions and reduced patient compliance. An intriguing approach to improve anti-TB therapy relates to nanocarrier-based drug-delivery systems, which enhance local drug concentrations at infection sites without systemic toxicity. Recently developed anti-TB antibiotics, however, are lipophilic and difficult to transport in aqueous systems. Here, the very lipophilic TB-antibiotics bedaquiline (BDQ) and BTZ (1,3-benzothiazin-4-one 043) are prepared as high-dose, amorphous nanoparticles via a solvent-antisolvent technique. The nanoparticles exhibit mean diameters of 60 ± 13 nm (BDQ) and 62 ± 44 nm (BTZ) and have an extraordinarily high drug load with 69% BDQ and >99% BTZ of total nanoparticle mass plus a certain amount of surfactant (31% for BDQ, <1% for BTZ) to make the lipophilic drugs water-dispersible. Suspensions with high drug load (4.1 mg/mL BDQ, 4.2 mg/mL BTZ) are stable for several weeks. In vitro and in vivo studies employing M.tb.-infected macrophages and susceptible C3HeB/FeJ mice show promising activity, which outperforms conventional BDQ/BTZ solutions (in DMF or DMSO) with an up to 50% higher efficacy upon pulmonary delivery. In vitro, the BDQ/BTZ nanoparticles demonstrate their ability to cross the different biological barriers and to reach the site of the intracellular mycobacteria. In vivo, high amounts of the BDQ/BTZ nanoparticles are found in the lung and specifically inside granulomas, whereas only low BDQ/BTZ-nanoparticle levels are observed in spleen or liver. Thus, pulmonary delivered BDQ/BTZ nanoparticles are promising formulations to improve antituberculosis treatment.

Improved mini-Tn7 Delivery Plasmids for Fluorescent Labeling of Stenotrophomonas maltophilia

Fluorescently labeled bacterial cells have become indispensable for many aspects of microbiological research, including studies on biofilm formation as an important virulence factor of various opportunistic bacteria of environmental origin such as Stenotrophomonas maltophilia. Using a Tn7-based genomic integration system, we report the construction of improved mini-Tn7 delivery plasmids for labeling of S. maltophilia with sfGFP, mCherry, tdTomato and mKate2 by expressing their codon-optimized genes from a strong, constitutive promoter and an optimized ribosomal binding site. Transposition of the mini-Tn7 transposons into single neutral sites located on average 25 nucleotides downstream of the 3'-end of the conserved glmS gene of different S. maltophilia wild-type strains did not have any adverse effects on the fitness of their fluorescently labeled derivatives. This was demonstrated by comparative analyses of growth, resistance profiles against 18 antibiotics of different classes, the ability to form biofilms on abiotic and biotic surfaces, also independent of the fluorescent protein expressed, and virulence in Galleria mellonella. It is also shown that the mini-Tn7 elements remained stably integrated in the genome of S. maltophilia over a prolonged period of time in the absence of antibiotic selection pressure. Overall, we provide evidence that the new improved mini-Tn7 delivery plasmids are valuable tools for generating fluorescently labeled S. maltophilia strains that are indistinguishable in their properties from their parental wild-type strains. IMPORTANCE The bacterium S. maltophilia is an important opportunistic nosocomial pathogen that can cause bacteremia and pneumonia in immunocompromised patients with a high rate of mortality. It is now considered as a clinically relevant and notorious pathogen in cystic fibrosis patients but has also been isolated from lung specimen of healthy donors. The high intrinsic resistance to a wide range of antibiotics complicates treatment and most likely contributes to the increasing incidence of S. maltophilia infections worldwide. One important virulence-related trait of S. maltophilia is the ability to form biofilms on any surface, which may result in the development of increased transient phenotypic resistance to antimicrobials. The significance of our work is to provide a mini-Tn7-based labeling system for S. maltophilia to study the mechanisms of biofilm formation or host-pathogen interactions with live bacteria under non-destructive conditions.

Amikacin@SiO2 core@shell nanocarriers to treat pulmonal bacterial infections

AMC@SiO₂ core@shell nanocarriers (AMC: amikacin) are realized and contain an exceptionally high drug load of 0.8 mg mg^-1 (i.e. 80% AMC of total nanocarrier mass). They are prepared via a solvent-antisolvent approach with AMC nanoparticles formed in a first step, which are then covered and stabilised by a thin silica shell in a one-pot synthesis. In total, the core@shell nanocarriers exhibit a mean diameter of 240 nm with an inner AMC core of 200 nm and an outer silica shell of 20 nm. Subsequent to synthesis, the nanocarriers can be stored in frozen dimethylsulfoxide (DMSO) and applied directly after warming to room temperature with particle contents of 5 mg mL^-1. Size, structure, and composition of the AMC@SiO₂ core@shell nanocarriers are evidenced by electron microscopy (SEM, TEM), spectroscopic methods (EDXS, FT-IR, UV-Vis), as well as X-ray powder diffraction and elemental analysis. As proof-of-concept, the AMC release and the activity of the novel nanocarriers are tested against two relevant, difficult-to-treat and notoriously multidrug resistant, bacterial pathogens: Mycobacterium tuberculosis (M.tb.) and Mycobacterium abscessus (M.abs.). Colloidal stability, storage stability, high drug load, and activity of the AMC@SiO₂ core@shell nanocarriers are promising for, e.g., aerosol-type pulmonal application.

Π-Π interactions stabilize PeptoMicelle-based formulations of Pretomanid derivatives leading to promising therapy against tuberculosis in zebrafish and mouse models

Tuberculosis is the deadliest bacterial disease globally, threatening the lives of millions every year. New antibiotic therapies that can shorten the duration of treatment, improve cure rates, and impede the development of drug resistance are desperately needed. Here, we used polymeric micelles to encapsulate four second-generation derivatives of the antitubercular drug pretomanid that had previously displayed much better in vivo activity against Mycobacterium tuberculosis than pretomanid itself. Because these compounds were relatively hydrophobic and had limited bioavailability, we expected that their micellar formulations would overcome these limitations, reduce toxicities, and improve therapeutic outcomes. The polymeric micelles were based on polypept(o)ides (PeptoMicelles) and were stabilized in their hydrophobic core by π-π interactions, allowing the efficient encapsulation of aromatic pretomanid derivatives. The stability of these π-π-stabilized PeptoMicelles was demonstrated in water, blood plasma, and lung surfactant by fluorescence cross-correlation spectroscopy and was further supported by prolonged circulation times of several days in the vasculature of zebrafish larvae. The most efficacious PeptoMicelle formulation tested in the zebrafish larvae infection model almost completely eradicated the bacteria at non-toxic doses. This lead formulation was further assessed against Mycobacterium tuberculosis in the susceptible C3HeB/FeJ mouse model, which develops human-like necrotic granulomas. Following intravenous administration, the drug-loaded PeptoMicelles significantly reduced bacterial burden and inflammatory responses in the lungs and spleens of infected mice.

Oral SARS-CoV-2 reduction by local treatment: A plasma technology application?

The SARS-CoV-2 pandemic reemphasized the importance of and need for efficient hygiene and disinfection measures. The coronavirus' efficient spread capitalizes on its airborne transmission routes via virus aerosol release from human oral and nasopharyngeal cavities. Besides the upper respiratory tract, efficient viral replication has been described in the epithelium of these two body cavities. To this end, the idea emerged to employ plasma technology to locally reduce mucosal viral loads as an additional measure to reduce patient infectivity. We here outline conceptual ideas of such treatment concepts within what is known in the antiviral actions of plasma treatment so far.

Tuberculostearic Acid-Containing Phosphatidylinositols as Markers of Bacterial Burden in Tuberculosis

One-fourth of the global human population is estimated to be infected with strains of the Mycobacterium tuberculosis complex (MTBC), the causative agent of tuberculosis (TB). Using lipidomic approaches, we show that tuberculostearic acid (TSA)-containing phosphatidylinositols (PIs) are molecular markers for infection with clinically relevant MTBC strains and signify bacterial burden. For the most abundant lipid marker, detection limits of ∼10² colony forming units (CFUs) and ∼10³ CFUs for bacterial and cell culture systems were determined, respectively. We developed a targeted lipid assay, which can be performed within a day including sample preparation—roughly 30-fold faster than in conventional methods based on bacterial culture. This indirect and culture-free detection approach allowed us to determine pathogen loads in infected murine macrophages, human neutrophils, and murine lung tissue. These marker lipids inferred from mycobacterial PIs were found in higher levels in peripheral blood mononuclear cells of TB patients compared to healthy individuals. Moreover, in a small cohort of drug-susceptible TB patients, elevated levels of these molecular markers were detected at the start of therapy and declined upon successful anti-TB treatment. Thus, the concentration of TSA-containing PIs can be used as a correlate for the mycobacterial burden in experimental models and in vitro systems and may prospectively also provide a clinically relevant tool to monitor TB severity.

Vitamin D3 and calcium carbonate supplementation for adolescents with HIV to reduce musculoskeletal morbidity and immunopathology (VITALITY trial): study protocol for a randomised placebo-controlled trial

BACKGROUND

Of the 2 million children living with HIV globally, 90% live in sub-Saharan Africa. Despite antiretroviral therapy, longstanding HIV infection is associated with several chronic complications in children including growth failure, particularly stunting and delayed puberty. Vitamin D deficiency, which is highly prevalent among children living with HIV in sub-Saharan Africa, has a further adverse impact on bone health. This trial aims to establish whether supplementation with vitamin D3 and calcium carbonate improves musculoskeletal health among peripubertal children living with HIV.

METHODS/DESIGN

We will conduct an individually randomised, double-blinded, placebo-controlled trial of weekly high-dose vitamin D3 (20,000 IU) plus daily calcium carbonate (500mg) supplementation for 48 weeks. Eight hundred and forty children living with HIV aged 11-19 years taking ART for ≥6 months will be enrolled and followed up for 96 weeks. The primary outcome is total body less-head bone mineral content for lean mass adjusted for height (TBLH-BMCLBM) Z-score at 48 weeks, measured by dual-energy X-ray absorptiometry (DEXA). Secondary outcomes are DEXA-measured lumbar spine bone mineral apparent density Z-score, number of respiratory infections, lean muscle mass and grip strength at 48 and 96 weeks and TBLH-BMCLBM Z-scores at 96 weeks. Sub-studies will investigate the effect of the intervention on vitamin D3 pathway metabolites and markers of bone turnover, intestinal microbiota, and innate and acquired immune function.

DISCUSSION

This is the largest trial to date of vitamin D supplementation in children living with HIV. Intervening to address deficits in bone accrual in childhood is critical for optimising adolescent and early adult bone health and prevention of later adult osteoporotic fractures. Trial results will draw attention to the need to screen for and treat long-term comorbidities in children living with HIV in resource-limited settings.

TRIAL REGISTRATION

Pan African Clinical Trials Registry PACTR20200989766029 . Registered on 3 September 2020.

Selective Targeting of Human and Animal Pathogens of the Helicobacter Genus by Flavodoxin Inhibitors: Efficacy, Synergy, Resistance and Mechanistic Studies

Antimicrobial resistant (AMR) bacteria constitute a global health concern. Helicobacter pylori is a Gram-negative bacterium that infects about half of the human population and is a major cause of peptic ulcer disease and gastric cancer. Increasing resistance to triple and quadruple H. pylori eradication therapies poses great challenges and urges the development of novel, ideally narrow spectrum, antimicrobials targeting H. pylori. Here, we describe the antimicrobial spectrum of a family of nitrobenzoxadiazol-based antimicrobials initially discovered as inhibitors of flavodoxin: an essential H. pylori protein. Two groups of inhibitors are described. One group is formed by narrow-spectrum compounds, highly specific for H. pylori, but ineffective against enterohepatic Helicobacter species and other Gram-negative or Gram-positive bacteria. The second group includes extended-spectrum antimicrobials additionally targeting Gram-positive bacteria, the Gram-negative Campylobacter jejuni, and most Helicobacter species, but not affecting other Gram-negative pathogens. To identify the binding site of the inhibitors in the flavodoxin structure, several H. pylori-flavodoxin variants have been engineered and tested using isothermal titration calorimetry. An initial study of the inhibitors capacity to generate resistances and of their synergism with antimicrobials commonly used in H. pylori eradication therapies is described. The narrow-spectrum inhibitors, which are expected to affect the microbiota less dramatically than current antimicrobial drugs, offer an opportunity to develop new and specific H. pylori eradication combinations to deal with AMR in H. pylori. On the other hand, the extended-spectrum inhibitors constitute a new family of promising antimicrobials, with a potential use against AMR Gram-positive bacterial pathogens.

The knowns and unknowns of latent Mycobacterium tuberculosis infection

Humans have been infected with Mycobacterium tuberculosis (Mtb) for thousands of years. While tuberculosis (TB), one of the deadliest infectious diseases, is caused by uncontrolled Mtb infection, over 90% of presumed infected individuals remain asymptomatic and contain Mtb in a latent TB infection (LTBI) without ever developing disease, and some may clear the infection. A small number of heavily Mtb-exposed individuals appear to resist developing traditional LTBI. Because Mtb has mechanisms for intracellular survival and immune evasion, successful control involves all of the arms of the immune system. Here, we focus on immune responses to Mtb in humans and nonhuman primates and discuss new concepts and outline major knowledge gaps in our understanding of LTBI, ranging from the earliest events of exposure and infection to success or failure of Mtb control.

WNT6/ACC2-induced storage of triacylglycerols in macrophages is exploited by Mycobacterium tuberculosis

In view of emerging drug-resistant tuberculosis (TB), host-directed adjunct therapies are urgently needed to improve treatment outcomes with currently available anti-TB therapies. One approach is to interfere with the formation of lipid-laden "foamy" macrophages in the host, as they provide a nutrient-rich host cell environment for Mycobacterium tuberculosis (Mtb). Here, we provide evidence that Wnt family member 6 (WNT6), a ligand of the evolutionarily conserved Wingless/Integrase 1 (WNT) signaling pathway, promotes foam cell formation by regulating key lipid metabolic genes including acetyl-CoA carboxylase 2 (ACC2) during pulmonary TB. Using genetic and pharmacological approaches, we demonstrated that lack of functional WNT6 or ACC2 significantly reduced intracellular triacylglycerol (TAG) levels and Mtb survival in macrophages. Moreover, treatment of Mtb-infected mice with a combination of a pharmacological ACC2 inhibitor and the anti-TB drug isoniazid (INH) reduced lung TAG and cytokine levels, as well as lung weights, compared with treatment with INH alone. This combination also reduced Mtb bacterial numbers and the size of mononuclear cell infiltrates in livers of infected mice. In summary, our findings demonstrate that Mtb exploits WNT6/ACC2-induced storage of TAGs in macrophages to facilitate its intracellular survival, a finding that opens new perspectives for host-directed adjunctive treatment of pulmonary TB.

Perspectives for systems biology in the management of tuberculosis

Standardised management of tuberculosis may soon be replaced by individualised, precision medicine-guided therapies informed with knowledge provided by the field of systems biology. Systems biology is a rapidly expanding field of computational and mathematical analysis and modelling of complex biological systems that can provide insights into mechanisms underlying tuberculosis, identify novel biomarkers, and help to optimise prevention, diagnosis and treatment of disease. These advances are critically important in the context of the evolving epidemic of drug-resistant tuberculosis. Here, we review the available evidence on the role of systems biology approaches - human and mycobacterial genomics and transcriptomics, proteomics, lipidomics/metabolomics, immunophenotyping, systems pharmacology and gut microbiomes - in the management of tuberculosis including prediction of risk for disease progression, severity of mycobacterial virulence and drug resistance, adverse events, comorbidities, response to therapy and treatment outcomes. Application of the Grading of Recommendations, Assessment, Development and Evaluation (GRADE) approach demonstrated that at present most of the studies provide "very low" certainty of evidence for answering clinically relevant questions. Further studies in large prospective cohorts of patients, including randomised clinical trials, are necessary to assess the applicability of the findings in tuberculosis prevention and more efficient clinical management of patients.

Mycobacterium tuberculosis Complex Lineage 3 as Causative Agent of Pulmonary Tuberculosis, Eastern Sudan1

Pathogen-based factors associated with tuberculosis (TB) in eastern Sudan are not well defined. We investigated genetic diversity, drug resistance, and possible transmission clusters of Mycobacterium tuberculosis complex (MTBC) strains by using a genomic epidemiology approach. We collected 383 sputum specimens at 3 hospitals in 2014 and 2016 from patients with symptoms suggestive of TB; of these, 171 grew MTBC strains. Whole-genome sequencing could be performed on 166 MTBC strains; phylogenetic classification revealed that most (73.4%; n = 122) belonged to lineage 3 (L3). Genome-based cluster analysis showed that 76 strains (45.9%) were grouped into 29 molecular clusters, comprising 2–8 strains/patients. Of the strains investigated, 9.0% (15/166) were multidrug resistant (MDR); 10 MDR MTBC strains were linked to 1 large MDR transmission network. Our findings indicate that L3 strains are the main causative agent of TB in eastern Sudan; MDR TB is caused mainly by transmission of MDR L3 strains.

Therapies for tuberculosis and AIDS: myeloid-derived suppressor cells in focus

The critical role of suppressive myeloid cells in immune regulation has come to the forefront in cancer research, with myeloid-derived suppressor cells (MDSCs) as a main oncology immunotherapeutic target. Recent improvement and standardization of criteria classifying tumor-induced MDSCs have led to unified descriptions and also promoted MDSC research in tuberculosis (TB) and AIDS. Despite convincing evidence on the induction of MDSCs by pathogen-derived molecules and inflammatory mediators in TB and AIDS, very little attention has been given to their therapeutic modulation or roles in vaccination in these diseases. Clinical manifestations in TB are consequences of complex host-pathogen interactions and are substantially affected by HIV infection. Here we summarize the current understanding and knowledge gaps regarding the role of MDSCs in HIV and Mycobacterium tuberculosis (co)infections. We discuss key scientific priorities to enable application of this knowledge to the development of novel strategies to improve vaccine efficacy and/or implementation of enhanced treatment approaches. Building on recent findings and potential for cross-fertilization between oncology and infection biology, we highlight current challenges and untapped opportunities for translating new advances in MDSC research into clinical applications for TB and AIDS.

Deficiency of the Intramembrane Protease SPPL2a Alters Antimycobacterial Cytokine Responses of Dendritic Cells

Signal peptide peptidase-like 2a (SPPL2a) is an aspartyl intramembrane protease essential for degradation of the invariant chain CD74. In humans, absence of SPPL2a leads to Mendelian susceptibility to mycobacterial disease, which is attributed to a loss of the dendritic cell (DC) subset conventional DC2. In this study, we confirm depletion of conventional DC2 in lymphatic tissues of SPPL2a^-/- mice and demonstrate dependence on CD74 using SPPL2a^-/- CD74^-/- mice. Upon contact with mycobacteria, SPPL2a^-/- bone marrow-derived DCs show enhanced secretion of IL-1β, whereas production of IL-10 and IFN-β is reduced. These effects correlated with modulated responses upon selective stimulation of the pattern recognition receptors TLR4 and Dectin-1. In SPPL2a^-/- bone marrow-derived DCs, Dectin-1 is redistributed to endosomal compartments. Thus, SPPL2a deficiency alters pattern recognition receptor pathways in a CD74-dependent way, shifting the balance from anti- to proinflammatory cytokines in antimycobacterial responses. We propose that in addition to the DC reduction, this altered DC functionality contributes to Mendelian susceptibility to mycobacterial disease upon SPPL2a deficiency.

In vitro and in vivo antitubercular activity of benzothiazinone-loaded human serum albumin nanocarriers designed for inhalation

The aim of this study was to investigate the potential of human serum albumin (HSA) as a solubilising agent/drug delivery vehicle for pulmonary administration of antimycobacterial benzothiazinone (BTZ) compounds. The solubility of four novel BTZ compounds (IR 20, IF 274, FG 2, AR 112) was enhanced 2 to 140-fold by incubation with albumin (0.38-134 μg/mL). Tryptophan 213 residue quenching studies indicated moderate binding strength to Sudlow's site I. Nanoparticle manufacture achieved 37-60% encapsulation efficiency in HSA particles (169 nm, zeta potential -31 mV). Drug release was triggered by proteases with >50% released in 4 h. The antimycobacterial activity of IR 20 and FG 2 loaded in HSA nanoparticles was enhanced compared to DMSO/phosphate buffered saline (PBS) or albumin/PBS solutions in an in vitro M. tuberculosis-infected macrophage model. Intranasal instillation was used to achieve pulmonary delivery daily over 10 days to M. tuberculosis infected mice for FG2 HSA nanoparticles (0.4 mg/kg), FG 2 DMSO/saline (0.4 and 8 mg/kg) and a reference compound, BTZ043, DMSO/saline (0.4 and 8 mg/kg). A lower lung M. tuberculosis burden was apparent for all BTZ cohorts, but only significant for BTZ043 at both doses. In conclusion, mechanisms of HSA nanoparticle loading and release of BTZ compounds were demonstrated, enhanced antimycobacterial activity of the nanoparticle formulations was demonstrated in a biorelevant in vitro bioassay and the effectiveness of BTZ by pulmonary delivery in vivo was established with pilot evidence for effectiveness when delivered by HSA nanoparticles. Finally, the feasibility of developing an inhaled nanoparticle-in-microparticle powder formulation was ascertained.

Differential Roles of the Calcium Ion Channel TRPV4 in Host Responses to Mycobacterium tuberculosis Early and Late in Infection

Mycobacterium tuberculosis subverts host immunity to proliferate within host tissues. Non-selective transient receptor potential (TRP) ion channels are involved in host responses and altered upon bacterial infections. Altered expression and localization of TRPV4 in macrophages upon virulent M. tuberculosis infection together with differential distribution of TRPV4 in human tuberculosis (TB) granulomas indicate a role of TRPV4 in TB. Compared with wild-type mice, Trpv4-deficient littermates showed transiently higher mycobacterial burden and reduced proinflammatory responses. In the absence of TRPV4, activation failed to render macrophages capable of controlling mycobacteria. Surprisingly, Trpv4-deficient mice were superior to wild-type ones in controlling M. tuberculosis infection in the chronic phase. Thus, Trpv4 is important in host responses to mycobacteria, although with opposite functions early versus late in infection. Ameliorated chronic infection in the absence of Trpv4 and its expression in human TB lesions indicate TRPV4 as putative target for host-directed therapy.

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Mtb down-modulates TRPV4 expression in macrophages

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Trpv4^−/− macrophages cannot be activated to drive phagosome maturation and NO production

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Trpv4-deficient mice are more resistant to Mtb

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TRPV4-positive macrophages in the periphery of human granuloma but not at the center