Reduction of T-Helper Cell Responses to Recall Antigen Mediated by Codelivery with Peptidoglycan via the Intestinal Nanomineral-Antigen Pathway

Naturally occurring intestinal nanomineral particles constituently form in the mammalian gut and trap luminal protein and microbial components. These cargo loaded nanominerals are actively scavenged by M cells of intestinal immune follicles, such as Peyer’s patches and are passed to antigen-presenting cells. Using peripheral blood mononuclear cell populations as an in vitro model of nanomineral uptake and antigen presentation, we show that monocytes avidly phagocytose nanomineral particles bearing antigen and peptidoglycan (PGN), and that the presence of PGN within particles downregulates their cell surface MHC class II and upregulates programmed death receptor ligand 1. Nanomineral delivery of antigen suppresses antigen-specific CD4⁺ T cell responses, an effect that is enhanced in the presence of PGN. Blocking the interleukin-10 receptor restores CD4⁺ T cell responses to antigen codelivered with PGN in nanomineral form. Using human intestinal specimens, we have shown that the in vivo nanomineral pathway operates in an interleukin-10 rich environment. Consequently, the delivery of a dual antigen–PGN cargo by endogenous nanomineral in vivo is likely to be important in the establishment of intestinal tolerance, while their synthetic mimetics present a potential delivery system for therapeutic applications targeting the modulation of Peyer’s patch T cell responses.

Synthetic mimetics of the endogenous gastrointestinal nanomineral: Silent constructs that trap macromolecules for intracellular delivery

Amorphous magnesium-substituted calcium phosphate (AMCP) nanoparticles (75-150nm) form constitutively in large numbers in the mammalian gut. Collective evidence indicates that they trap and deliver luminal macromolecules to mucosal antigen presenting cells (APCs) and facilitate gut immune homeostasis. Here, we report on a synthetic mimetic of the endogenous AMCP and show that it has marked capacity to trap macromolecules during formation. Macromolecular capture into AMCP involved incorporation as shown by STEM tomography of the synthetic AMCP particle with 5nm ultra-fine iron (III) oxohydroxide. In vitro, organic cargo-loaded synthetic AMCP was taken up by APCs and tracked to lysosomal compartments. The AMCP itself did not regulate any gene, or modify any gene regulation by its cargo, based upon whole genome transcriptomic analyses. We conclude that synthetic AMCP can efficiently trap macromolecules and deliver them to APCs in a silent fashion, and may thus represent a new platform for antigen delivery.

Cell-type-specific modulation of innate immune signalling by vitamin D in human mononuclear phagocytes

Vitamin D is widely reported to inhibit innate immune signalling and dendritic cell (DC) maturation as a potential immunoregulatory mechanism. It is not known whether vitamin D has global or gene‐specific effects on transcriptional responses downstream of innate immune stimulation, or whether vitamin D inhibition of innate immune signalling is common to different cells. We confirmed vitamin D inhibition of nuclear factor‐κB (NF‐κB) and p38 mitogen‐activated protein kinase (MAPK) signalling in monocyte‐derived DC (MDDC) stimulated with lipopolysaccharide (LPS). This was associated with global but modest attenuation of LPS‐induced transcriptional changes at genome‐wide level. Surprisingly, vitamin D did not inhibit innate immune NF‐κB activation in monocyte‐derived macrophages. Consistent with our findings in MDDC, ex vivo vitamin D treatment of primary peripheral blood myeloid DC also led to significant inhibition of LPS‐inducible NF‐κB activation. Unexpectedly, in the same samples, vitamin D enhanced activation of both NF‐κB and MAPK signalling in primary peripheral blood monocytes. In a cross‐sectional clinical cohort, we found no relationship between peripheral blood vitamin D levels and LPS‐inducible activation of NF‐κB and MAPK pathways in monocytes of myeloid DC. Remarkably, however, in vivo supplementation of people with vitamin D deficiency in this clinical cohort also enhanced LPS‐inducible MAPK signalling in peripheral blood monocytes. Therefore, we report that vitamin D differentially modulates the molecular response to innate immune stimulation in monocytes, macrophages and dendritic cells. These results are of importance in the design of studies on vitamin D supplementation in infectious and immunological diseases.

Diagnostic 'omics' for active tuberculosis

The decision to treat active tuberculosis (TB) is dependent on microbiological tests for the organism or evidence of disease compatible with TB in people with a high demographic risk of exposure. The tuberculin skin test and peripheral blood interferon-γ release assays do not distinguish active TB from a cleared or latent infection. Microbiological culture of mycobacteria is slow. Moreover, the sensitivities of culture and microscopy for acid-fast bacilli and nucleic acid detection by PCR are often compromised by difficulty in obtaining samples from the site of disease. Consequently, we need sensitive and rapid tests for easily obtained clinical samples, which can be deployed to assess patients exposed to TB, discriminate TB from other infectious, inflammatory or autoimmune diseases, and to identify subclinical TB in HIV-1 infected patients prior to commencing antiretroviral therapy. We discuss the evaluation of peripheral blood transcriptomics, proteomics and metabolomics to develop the next generation of rapid diagnostics for active TB. We catalogue the studies published to date seeking to discriminate active TB from healthy volunteers, patients with latent infection and those with other diseases. We identify the limitations of these studies and the barriers to their adoption in clinical practice. In so doing, we aim to develop a framework to guide our approach to discovery and development of diagnostic biomarkers for active TB.

An endogenous nanomineral chaperones luminal antigen and peptidoglycan to intestinal immune cells

In humans and other mammals it is known that calcium and phosphate ions are secreted from the distal small intestine into the lumen. However, why this secretion occurs is unclear. Here, we show that the process leads to the formation of amorphous magnesium-substituted calcium phosphate nanoparticles that trap soluble macromolecules, such as bacterial peptidoglycan and orally fed protein antigens, in the lumen and transport them to immune cells of the intestinal tissue. The macromolecule-containing nanoparticles utilize epithelial M cells to enter Peyer's patches, small areas of the intestine concentrated with particle-scavenging immune cells. In wild-type mice, intestinal immune cells containing these naturally formed nanoparticles expressed the immune tolerance-associated molecule 'programmed death-ligand 1', whereas in NOD1/2 double knockout mice, which cannot recognize peptidoglycan, programmed death-ligand 1 was undetected. Our results explain a role for constitutively formed calcium phosphate nanoparticles in the gut lumen and show how this helps to shape intestinal immune homeostasis.

Artefactual nanoparticle activation of the inflammasome platform: in vitro evidence with a nano-formed calcium phosphate

AIM

To determine whether in vitro experimental conditions dictate cellular activation of the inflammasome by apatitic calcium phosphate nanoparticles.

MATERIAL & METHODS

The responses of blood-derived primary human cells to in situ-formed apatite were investigated under different experimental conditions to assess the effect of aseptic culture, cell rest and duration of particle exposure. Cell death and particle uptake were assessed, while IL-1β and caspase 1 responses, with and without lipopolysaccharide prestimulation, were evaluated as markers of inflammasome activation.

RESULTS

Under carefully addressed experimental conditions, apatitic nanoparticles did not induce cell death or engage the inflammasome platform, although both could be triggered through artefacts of experimentation.

CONCLUSION

In vitro studies often predict that engineered nanoparticles, such as synthetic apatite, are candidates for inflammasome activation and, hence, are toxic. However, the experimental setting must be very carefully considered as it may promote false-positive outcomes.

Development of a system dynamics model for financially sustainable management of municipal watermain networks

This paper develops causal loop diagrams and a system dynamics model for financially sustainable management of urban water distribution networks. The developed causal loop diagrams are a novel contribution in that it illustrates the unique characteristics and feedback loops for financially self-sustaining water distribution networks. The system dynamics model is a mathematical realization of the developed interactions among system variables over time and is comprised of three sectors namely watermains network, consumer, and finance. This is the first known development of a water distribution network system dynamics model. The watermains network sector accounts for the unique characteristics of watermain pipes such as service life, deterioration progression, pipe breaks, and water leakage. The finance sector allows for cash reserving by the utility in addition to the pay-as-you-go and borrowing strategies. The consumer sector includes controls to model water fee growth as a function of service performance and a household's financial burden due to water fees. A series of policy levers are provided that allow the impact of various financing strategies to be evaluated in terms of financial sustainability and household affordability. The model also allows for examination of the impact of different management strategies on the water fee in terms of consistency and stability over time. The paper concludes with a discussion on how the developed system dynamics water model can be used by water utilities to achieve a variety of utility short and long-term objectives and to establish realistic and defensible water utility policies. It also discusses how the model can be used by regulatory bodies, government agencies, the financial industry, and researchers.

Effect of altered surfaces on postural sway characteristics in elderly subjects

Mobility is essentially based on successful balance control. The evaluation of functional strategies for postural stability is requisite for effective balance rehabilitation and fall prevention in elderly subjects. Our objective was to clarify control mechanisms of different standing positions reflecting challenges of typical everyday life situations. For this purpose, elderly subjects stood on different surfaces resulting in a change of the biomechanical constraints. Sway parameters out of time and frequency domain were calculated from center-of-pressure (COP) excursions. Besides the classic quantification of the amount of sway variability, we investigated the temporal organization of postural sway by means of nonlinear time series analysis. Limb load symmetry was quantified via foot pressure insoles. We found task dependent motor outputs: (1) asymmetrical loading in all conditions; (2) altered amount and structure of COP movements with dissimilar changes in medio-lateral and anterior-posterior direction; (3) changes of the motor output affect several time scales especially when standing on a balance board or with one foot on a step. Our results indicate that elderly subjects preferred forcefully one limb which supports a step-initiation strategy. Modifications of the postural sway structure refer to the interaction of multiple control mechanisms to cope with the altered demands. The identification of postural strategies employed in daily activities augments the ecological validity of postural control studies.

Application of system dynamics for developing financially self-sustaining management policies for water and wastewater systems

Recently enacted regulations in Canada and elsewhere require water utilities to be financially self-sustaining over the long-term. This implies full cost recovery for providing water and wastewater services to users. This study proposes a new approach to help water utilities plan to meet the requirements of the new regulations. A causal loop diagram is developed for a financially self-sustaining water utility which frames water and wastewater network management as a complex system with multiple interconnections and feedback loops. The novel System Dynamics approach is used to develop a demonstration model for water and wastewater network management. This is the first known application of System Dynamics to water and wastewater network management. The network simulated is that of a typical Canadian water utility that has under invested in maintenance. Model results show that with no proactive rehabilitation strategy the utility will need to substantially increase its user fees to achieve financial sustainability. This increase is further exacerbated when price elasticity of water demand is considered. When the utility pursues proactive rehabilitation, financial sustainability is achieved with lower user fees. Having demonstrated the significance of feedback loops for financial management of water and wastewater networks, the paper makes the case for a more complete utility model that considers the complexity of the system by incorporating all feedback loops.