A major limitation of current humanized mouse models is that they primarily enable the analysis of human-specific pathogens that infect hematopoietic cells. However, most human pathogens target other ...cell types, including epithelial, endothelial and mesenchymal cells. Here, we show that implantation of human lung tissue, which contains up to 40 cell types, including nonhematopoietic cells, into immunodeficient mice (lung-only mice) resulted in the development of a highly vascularized lung implant. We demonstrate that emerging and clinically relevant human pathogens such as Middle East respiratory syndrome coronavirus, Zika virus, respiratory syncytial virus and cytomegalovirus replicate in vivo in these lung implants. When incorporated into bone marrow/liver/thymus humanized mice, lung implants are repopulated with autologous human hematopoietic cells. We show robust antigen-specific humoral and T-cell responses following cytomegalovirus infection that control virus replication. Lung-only mice and bone marrow/liver/thymus-lung humanized mice substantially increase the number of human pathogens that can be studied in vivo, facilitating the in vivo testing of therapeutics.
New therapeutic strategies are needed to treat drug resistant tuberculosis (TB) and to improve treatment for drug sensitive TB. Pyrazinamide (PZA) is a critical component of current first-line TB ...therapy. However, the rise in PZA-resistant TB cases jeopardizes the future utility of PZA. To address this problem, we used the guinea pig model of TB and tested the efficacy of an inhaled dry powder combination, referred to as Pyrazinoic acid/ester Dry Powder (PDP), which is comprised of pyrazinoic acid (POA), the active moiety of PZA, and pyrazinoic acid ester (PAE), which is a PZA analog. Both POA and PAE have the advantage of being able to act on PZA-resistant Mycobacterium tuberculosis. When used in combination with oral rifampicin (R), inhaled PDP had striking effects on tissue pathology. Effects were observed in lungs, the site of delivery, but also in the spleen and liver indicating both local and systemic effects of inhaled PDP. Tissue granulomas that harbor M. tuberculosis in a persistent state are a hallmark of TB and they pose a challenge for therapy. Compared to other treatments, which preferentially cleared non-necrotic granulomas, R+PDP reduced necrotic granulomas more effectively. The increased ability of R+PDP to act on more recalcitrant necrotic granulomas suggests a novel mechanism of action. The results presented in this report reveal the potential for developing therapies involving POA that are optimized to target necrotic as well as non-necrotic granulomas as a means of achieving more complete sterilization of M. tuberculosis bacilli and preventing disease relapse when therapy ends.
Mycobacteria possess Mce transporters that import lipids and are thought to function analogously to ATP-binding cassette (ABC) transporters. However, whereas ABC transporters import substrates using ...a single solute-binding protein (SBP) to deliver a substrate to permease proteins in the membrane, mycobacterial Mce transporters have a potential for six SBPs (MceA to MceF) working with a pair of permeases (YrbEA and YrbEB), a cytoplasmic ATPase (MceG), and multiple Mce-associated membrane (Mam) and orphaned Mam (Omam) proteins to transport lipids. In this study, we used the model mycobacterium
to study the requirement for individual Mce, Mam, and Omam proteins in Mce4 transport of cholesterol. All of the Mce4 and Mam4 proteins we investigated were required for cholesterol uptake. However, not all Omam proteins, which are encoded by genes outside
loci, proved to contribute to cholesterol import. OmamA and OmamB were required for cholesterol import, while OmamC, OmamD, OmamE, and OmamF were not. In the absence of any single Mce4, Mam4, or Omam protein that we tested, the abundance of Mce4A and Mce4E declined. This relationship between the levels of Mce4A and Mce4E and these additional proteins suggests a network of interactions that assemble and/or stabilize a multiprotein Mce4 transporter complex. Further support for Mce transporters being multiprotein complexes was obtained by immunoprecipitation-mass spectrometry, in which we identified every single Mce, YrbE, MceG, Mam, and Omam protein with a role in cholesterol transport as associating with Mce4A. This study represents the first time any of these Mce4 transporter proteins has been shown to associate.
How lipids travel between membranes of diderm bacteria is a challenging mechanistic question because lipids, which are hydrophobic molecules, must traverse a hydrophilic periplasm. This question is even more complex for mycobacteria, which have a unique cell envelope that is highly impermeable to molecules. A growing body of knowledge identifies Mce transporters as lipid importers for mycobacteria. Here, using protein stability experiments and immunoprecipitation-mass spectrometry, we provide evidence for mycobacterial Mce transporters existing as multiprotein complexes.
Metastasis remains a leading cause of morbidity and mortality from solid tumors. Lack of comprehensive systems to study the progression of metastasis contributes to the low success of treatment. We ...developed a novel three‐dimensional in vitro reconstructed metastasis (rMet) model that incorporates extracellular matrix (ECM) elements characteristic of the primary (breast, prostate, or lung) and metastatic (bone marrow, BM) sites. A cytokine‐rich liquid interphase separates the primary and distant sites, further recapitulating circulation. Similar to main events underlying the metastatic cascade, the rMet model fractionated human tumor cell lines into sub‐populations with distinct invasive and migratory abilities: (i) a primary tumor‐like fraction mainly consisting of non‐migratory spheroids; (ii) an invasive fraction that invaded through the primary tumor ECM, but failed to acquire anchorage‐independence and reach the BM; and (iii) a highly migratory BM‐colonizing population that invaded the primary ECM, survived in the “circulation‐like” media, and successfully invaded and proliferated within BM ECM. BM‐colonizing fractions successfully established metastatic bone lesions in vivo, whereas the tumor‐like spheroids failed to engraft the bones, showing the ability of the rMet model to faithfully select for highly aggressive sub‐populations with a propensity to colonize a metastatic site. By applying the rMet model to study real‐time ECM remodeling, we show that tumor cells secrete collagenolytic enzymes for invading the primary site ECM but not for entering the BM ECM, indicating possible differences in ECM remodeling mechanisms at primary tumor versus metastatic sites.
Study of metastasis is challenging due to a lack of models that resemble its multi‐step nature in a physiologically relevant manner. The authors describe a three‐dimensional reconstructed metastasis (rMet) model that enables a comparative, real‐time study of metastasis and its molecular events. Since the rMet model recapitulates the native tissue microenvironment, it is an invaluable preclinical tool to study mechanisms of metastasis and explore putative therapeutics and preventative measures.
Tuberculosis (TB) is a major global health challenge, with approximately 1.4 million deaths per year. There is still a need to develop novel treatments for patients infected with Mycobacterium ...tuberculosis (Mtb). There have been many large-scale phenotypic screens that have led to the identification of thousands of new compounds. Yet, there is very limited investment in TB drug discovery which points to the need for new methods to increase the efficiency of drug discovery against Mtb. We have used machine learning approaches to learn from the public Mtb data, resulting in many data sets and models with robust enrichment and hit rates leading to the discovery of new active compounds. Recently, we have curated predominantly small-molecule Mtb data and developed new machine learning classification models with 18 886 molecules at different activity cutoffs. We now describe the further validation of these Bayesian models using a library of over 1000 molecules synthesized as part of EU-funded New Medicines for TB and More Medicines for TB programs. We highlight molecular features which are enriched in these active compounds. In addition, we provide new regression and classification models that can be used for scoring compound libraries or used to design new molecules. We have also visualized these molecules in the context of known molecular targets and identified clusters in chemical property space, which may aid in future target identification efforts. Finally, we are also making these data sets publicly available, representing a significant increase to the available Mtb inhibition data in the public domain.
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Neuroblastoma (NB) is the second leading extracranial solid tumor of early childhood with about two-thirds of cases presenting before the age of 5, and accounts for roughly 15 percent ...of all pediatric cancer fatalities in the United States. Treatments against NB are lacking, resulting in a low survival rate in high-risk patients. A repurposing approach using already approved or clinical stage compounds can be used for diseases for which the patient population is small, and the commercial market limited. We have used Bayesian machine learning, in vitro cell assays, and combination analysis to identify molecules with potential use for NB. We demonstrated that pyronaridine (SH-SY5Y IC50 1.70 µM, SK-N-AS IC50 3.45 µM), BAY 11–7082 (SH-SY5Y IC50 0.85 µM, SK-N-AS IC50 1.23 µM), niclosamide (SH-SY5Y IC50 0.87 µM, SK-N-AS IC50 2.33 µM) and fingolimod (SH-SY5Y IC50 4.71 µM, SK-N-AS IC50 6.11 µM) showed cytotoxicity against NB. As several of the molecules are approved drugs in the US or elsewhere, they may be repurposed more readily for NB treatment. Pyronaridine was also tested in combinations in SH-SY5Y cells and demonstrated an antagonistic effect with either etoposide or crizotinib. Whereas when crizotinib and etoposide were combined with each other they had a synergistic effect in these cells. We have also described several analogs of pyronaridine to explore the structure–activity relationship against cell lines. We describe multiple molecules demonstrating cytotoxicity against NB and the further evaluation of these molecules and combinations using other NB cells lines and in vivo models will be important in the future to assess translational potential.
Tuberculosis (TB), caused by Mycobacterium tuberculosis (Mtb), remains a leading cause of death with 1.6 million deaths worldwide reported in 2021. Oral pyrazinamide (PZA) is an integral part of ...anti-TB regimens, but its prolonged use has the potential to drive the development of PZA-resistant Mtb. PZA is converted to the active moiety pyrazinoic acid (POA) by the Mtb pyrazinamidase encoded by pncA, and mutations in pncA are associated with the majority of PZA resistance. Conventional oral and parenteral therapies may result in subtherapeutic exposure in the lung; hence, direct pulmonary administration of POA may provide an approach to rescue PZA efficacy for treating pncA-mutant PZA-resistant Mtb. The objectives of the current study were to (i) develop novel dry powder POA formulations, (ii) assess their feasibility for pulmonary delivery using physicochemical characterization, (iii) evaluate their pharmacokinetics (PK) in the guinea pig model, and (iv) develop a mechanism-based pharmacokinetic model (MBM) using in vivo PK data to select a formulation providing adequate exposure in epithelial lining fluid (ELF) and lung tissue. We developed three POA formulations for pulmonary delivery and characterized their PK in plasma, ELF, and lung tissue following passive inhalation in guinea pigs. Additionally, the PK of POA following oral, intravenous, and intratracheal administration was characterized in guinea pigs. The MBM was used to simultaneously model PK data following administration of POA and its formulations via the different routes. The MBM described POA PK well in plasma, ELF, and lung tissue. Physicochemical analyses and MBM predictions suggested that POA maltodextrin was the best among the three formulations and an excellent candidate for further development as it has: (i) the highest ELF-to-plasma exposure ratio (203) and lung tissue-to-plasma exposure ratio (30.4) compared with POA maltodextrin and leucine (75.7/16.2) and POA leucine salt (64.2/19.3) and (ii) the highest concentration in ELF (C maxELF: 171 nM) within 15.5 min, correlating with a fast transfer into ELF after pulmonary administration (K PM: 22.6 1/h). The data from the guinea pig allowed scaling, using the MBM to a human dose of POA maltodextrin powder demonstrating the potential feasibility of an inhaled product.
The Mce transporters of mycobacteria import lipids from the environment, across an outer and an inner membrane (diderm structure), and into the cytoplasm where lipids serve as precursors for lipid ...biogenesis or can be broken down for energy. Each mce operon is composed of two predicted permease-encoding genes and six mce genes encoding proteins (MceA-F) predicted to function as solute binding proteins (SBPs). Genes encoding Mce Associated Membrane (Mam) proteins are linked to mce operons, although their function remains unknown. Furthermore, there are orphaned Mce Associated Membrane proteins (Omams), which share predicted structural similarity to Mam proteins but are encoded by genes that are not linked to mce operons. An unlinked gene encodes an ATPase, MceG, that is predicted to function in all Mce systems. Our goal is to determine how Mce transporters work by characterizing the Mce4 transporter, a cholesterol import system for mycobacteria. To define contributions of Mce proteins, we began by making mutants lacking individual Mce4 proteins in the model mycobacteria, M. smegmatis, and analyzed Mce4 transporter function of the mutants using cholesterol uptake and utilization assays. Our results demonstrate that Mce4A,E,F, Mam4A,B, and OmamA,B proteins each have non-redundant roles. We hypothesized that Mce4A,E,F, Mam4A,B, and OmamA,B function together in a large, multi-protein complex. In support of our hypothesis, we discovered that the absence of individual Mce, Mam, or Omam proteins results in reduced levels of the other Mce4 components, which is consistent with these proteins stabilizing one another in a complex. Additionally, mass spectrometry (MS) analysis of Mce4A-HA immunoprecipitations (IPs) identified all mce locus-encoding components (YrbE4A,B, Mce4A-F, Mam4AB) as well as OmamA,B, and MceG as interactors of Mce4A-HA, suggesting that these components exist in complex with one another. The IP-MS analysis also reveals potentially unidentified components of the Mce4 transporter. Our characterization of the Mce4 transport system provides evidence of a multi-protein complex with non-redundant components in the mycobacterial cell wall and lays the groundwork to address mechanistic questions of cell envelope lipid transport, answers to which will provide insight into the challenges of lipid transport for all diderm structures.
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