Systemic activation of dendritic cells by Toll-like receptor ligands or malaria infection impairs cross-presentation and anti-viral immunity

The mechanisms responsible for the immunosuppression associated with sepsis or some chronic blood infections remain poorly understood. Here we show that infection with a malaria parasite (Plasmodium berghei) or simple systemic exposure to bacterial or viral Toll-like receptor ligands inhibited cross-priming. Reduced cross-priming was a consequence of downregulation of cross-presentation by activated dendritic cells due to systemic activation that did not otherwise globally inhibit T cell proliferation. Although activated dendritic cells retained their capacity to present viral antigens via the endogenous major histocompatibility complex class I processing pathway, antiviral responses were greatly impaired in mice exposed to Toll-like receptor ligands. This is consistent with a key function for cross-presentation in antiviral immunity and helps explain the immunosuppressive effects of systemic infection. Moreover, inhibition of cross-presentation was overcome by injection of dendritic cells bearing antigen, which provides a new strategy for generating immunity during immunosuppressive blood infections.

Analysis of the effect of different NKT cell subpopulations on the activation of CD4 and CD8 T cells, NK cells, and B cells

Objective. NKT cells have diverse immune regulatory functions including activation of cells involved in Th1- and Th2-type immune activities. Most previous studies have investigated the functions of NKT cells as a single family but more recent evidence indicates the distinct functional properties of NKT cell subpopulation. This study aims to determine whether NKT cell subpopulations have different stimulatory activities on other immune cells that may affect the outcome of NKT cell-based immunotherapy. Methods. NKT cells and NKT cell subpopulations (CD4(+)CD8(-), CD4(-)CD8(+), CD4(-)CD8(+)) were cocultured with PBMC and their activities on immune cells including CD4(+) and CD8(+) T cells, NK cells, and B cells were assessed by flow cytometry. The production of cytokines in culture was measured by enzyme-linked immunsorbent assay. Results. The CD4(+)CD8(-) NKT cells demonstrated substantially greater stimulatory activities on CD4(+) T cells, NK cells, and B cells than other NKT cell subsets. The CD4(-)CD8(+) NKT cells showed the greatest activity on CD8(+) T cells, and were the only NKT cell subset that activated these immune cells. The CD4(-)CD8(-) NKT cells showed moderate stimulatory activity on CD4(+) T cells and the least activity on other immune cells. Conclusion. The results here suggest that NKT cell subpopulations differ in their abilities to stimulate other immune cells. This highlights the potential importance of manipulating specific NKT cell subpopulations for particular therapeutic situations and of evaluating subpopulations, rather than NKT cells as a group, during investigation of a possible role of NKT cells in various disease settings. (c) 2006 International Society for Experimental Hematology. Published by Elsevier Inc.

Metal binding to transferrin and immune reactions in Parkinson's disease

The binding of iron (59Fe) and gallium (67Ga) to the plasma protein transferrin (Tf) was investigated by G75 gel filtration chromatography in control patients and treated and untreated patients with Parkinson's disease (PD). Fe-Tf binding was 100% in all controls and PD patients suggesting that a defect in Fe-Tf binding was not involved in the aetiology of PD. Ga-Tf binding was significantly reduced in both untreated and treated PD patients compared to controls. In addition, treated PD patients had significantly higher Ga-Tf binding than untreated patients. A reduction in metal binding to Tf could result in the increase of a low molecular weight species which may more readily enter the CNS. Alternatively, it could lead to a decrease in the transport of essential metals into the brain via the Tf receptor system. A significant elevation in neopterin was demonstrated within the plasma of untreated PD patients compared to controls suggesting the activation of a cellular immune response. Furthermore, plasma neopterin was lower in treated compared to untreated PD patients, although the difference was not significant. There was no evidence for the activation of the humoral immune response in untreated or treated PD patients as measured by circulating immune complex (CIC) levels within the plasma. An inverse relationship between Ga-Tf binding and neopterin was observed in untreated PD patients. The addition of oxidants in the form of potassium permanganate and activated manganese dioxide reduced Ga-Tf binding in control plasma. However, relatively little response was observed using monocyte preparations. The results suggest that oxidants produced by activation of the cellular immune system could damage the Tf molecule thereby reducing its ability to bind metals.

Proteins accessible to immune surveillance show significant T-cell epitope depletion:implications for vaccine design

T cell activation is the final step in a complex pathway through which pathogen-derived peptide fragments can elicit an immune response. For it to occur, peptides must form stable complexes with Major Histocompatibility Complex (MHC) molecules and be presented on the cell surface. Computational predictors of MHC binding are often used within in silico vaccine design pathways. We have previously shown that, paradoxically, most bacterial proteins known experimentally to elicit an immune response in disease models are depleted in peptides predicted to bind to human MHC alleles. The results presented here, derived using software proven through benchmarking to be the most accurate currently available, show that vaccine antigens contain fewer predicted MHC-binding peptides than control bacterial proteins from almost all subcellular locations with the exception of cell wall and some cytoplasmic proteins. This effect is too large to be explained from the undoubted lack of precision of the software or from the amino acid composition of the antigens. Instead, we propose that pathogens have evolved under the influence of the host immune system so that surface proteins are depleted in potential MHC-binding peptides, and suggest that identification of a protein likely to contain a single immuno-dominant epitope is likely to be a productive strategy for vaccine design.

Extracellular cathepsin S and intracellular caspase 1 activation are surrogate biomarkers of particulate-induced lysosomal disruption in macrophages

BACKGROUND: Particulate matter has been shown to stimulate the innate immune system and induce acute inflammation. Therefore, while nanotechnology has the potential to provide therapeutic formulations with improved efficacy, there are concerns such pharmaceutical preparations could induce unwanted inflammatory side effects. Accordingly, we aim to examine the utility of using the proteolytic activity signatures of cysteine proteases, caspase 1 and cathepsin S (CTSS), as biomarkers to assess particulate-induced inflammation.

METHODS: Primary peritoneal macrophages and bone marrow-derived macrophages from C57BL/6 mice and ctss(-/-) mice were exposed to micro- and nanoparticulates and also the lysosomotropic agent, L-leucyl-L-leucine methyl ester (LLOME). ELISA and immunoblot analyses were used to measure the IL-1β response in cells, generated by lysosomal rupture. Affinity-binding probes (ABPs), which irreversibly bind to the active site thiol of cysteine proteases, were then used to detect active caspase 1 and CTSS following lysosomal rupture. Reporter substrates were also used to quantify the proteolytic activity of these enzymes, as measured by substrate turnover.

RESULTS: We demonstrate that exposure to silica, alum and polystyrene particulates induces IL-1β release from macrophages, through lysosomal destabilization. IL-1β secretion positively correlated with an increase in the proteolytic activity signatures of intracellular caspase 1 and extracellular CTSS, which were detected using ABPs and reporter substrates. Interestingly IL-1β release was significantly reduced in primary macrophages from ctss(-/-) mice.

CONCLUSIONS: This study supports the emerging significance of CTSS as a regulator of the innate immune response, highlighting its role in regulating IL-1β release. Crucially, the results demonstrate the utility of intracellular caspase 1 and extracellular CTSS proteolytic activities as surrogate biomarkers of lysosomal rupture and acute inflammation. In the future, activity-based detection of these enzymes may prove useful for the real-time assessment of particle-induced inflammation and toxicity assessment during the development of nanotherapeutics.

Activation of STING-Dependent Innate Immune Signaling By S-Phase-Specific DNA Damage in Breast Cancer

BACKGROUND: Previously we identified a DNA damage response-deficient (DDRD) molecular subtype within breast cancer. A 44-gene assay identifying this subtype was validated as predicting benefit from DNA-damaging chemotherapy. This subtype was defined by interferon signaling. In this study, we address the mechanism of this immune response and its possible clinical significance.

METHODS: We used immunohistochemistry (IHC) to characterize immune infiltration in 184 breast cancer samples, of which 65 were within the DDRD subtype. Isogenic cell lines, which represent DDRD-positive and -negative, were used to study the effects of chemokine release on peripheral blood mononuclear cell (PBMC) migration and the mechanism of immune signaling activation. Finally, we studied the association between the DDRD subtype and expression of the immune-checkpoint protein PD-L1 as detected by IHC. All statistical tests were two-sided.

RESULTS: We found that DDRD breast tumors were associated with CD4+ and CD8+ lymphocytic infiltration (Fisher's exact test P < .001) and that DDRD cells expressed the chemokines CXCL10 and CCL5 3.5- to 11.9-fold more than DNA damage response-proficient cells (P < .01). Conditioned medium from DDRD cells statistically significantly attracted PBMCs when compared with medium from DNA damage response-proficient cells (P < .05), and this was dependent on CXCL10 and CCL5. DDRD cells demonstrated increased cytosolic DNA and constitutive activation of the viral response cGAS/STING/TBK1/IRF3 pathway. Importantly, this pathway was activated in a cell cycle-specific manner. Finally, we demonstrated that S-phase DNA damage activated expression of PD-L1 in a STING-dependent manner.

CONCLUSIONS: We propose a novel mechanism of immune infiltration in DDRD tumors, independent of neoantigen production. Activation of this pathway and associated PD-L1 expression may explain the paradoxical lack of T-cell-mediated cytotoxicity observed in DDRD tumors. We provide a rationale for exploration of DDRD in the stratification of patients for immune checkpoint-based therapies.

A Recommender System based on the Immune Network

Abstract-The immune system is a complex biological system with a highly distributed, adaptive and self-organising nature. This paper presents an artificial immune system (AIS) that exploits some of these characteristics and is applied to the task of film recommendation by collaborative filtering (CF). Natural evolution and in particular the immune system have not been designed for classical optimisation. However, for this problem, we are not interested in finding a single optimum. Rather we intend to identify a sub-set of good matches on which recommendations can be based. It is our hypothesis that an AIS built on two central aspects of the biological immune system will be an ideal candidate to achieve this: Antigen - antibody interaction for matching and antibody - antibody interaction for diversity. Computational results are presented in support of this conjecture and compared to those found by other CF techniques.

A Recommender System based on Idiotypic Artificial Immune Networks

The immune system is a complex biological system with a highly distributed, adaptive and self-organising nature. This paper presents an Artificial Immune System (AIS) that exploits some of these characteristics and is applied to the task of film recommendation by Collaborative Filtering (CF). Natural evolution and in particular the immune system have not been designed for classical optimisation. However, for this problem, we are not interested in finding a single optimum. Rather we intend to identify a sub-set of good matches on which recommendations can be based. It is our hypothesis that an AIS built on two central aspects of the biological immune system will be an ideal candidate to achieve this: Antigen-antibody interaction for matching and idiotypic antibody-antibody interaction for diversity. Computational results are presented in support of this conjecture and compared to those found by other CF techniques.

Artificial Immune Tissue using Self-Organizing Networks

As introduced by Bentley et al. (2005), artificial immune systems (AIS) are lacking tissue, which is present in one form or another in all living multi-cellular organisms. Some have argued that this concept in the context of AIS brings little novelty to the already saturated field of the immune inspired computational research. This article aims to show that such a component of an AIS has the potential to bring an advantage to a data processing algorithm in terms of data pre-processing, clustering and extraction of features desired by the immune inspired system. The proposed tissue algorithm is based on self-organizing networks, such as self-organizing maps (SOM) developed by Kohonen (1996) and an analogy of the so called Toll-Like Receptors (TLR) affecting the activation function of the clusters developed by the SOM.

An Immune Network Intrusion Detection System Utilising Correlation Context

Network Intrusion Detection Systems (NIDS) are computer systems which monitor a network with the aim of discerning malicious from benign activity on that network. While a wide range of approaches have met varying levels of success, most IDSs rely on having access to a database of known attack signatures which are written by security experts. Nowadays, in order to solve problems with false positive alerts, correlation algorithms are used to add additional structure to sequences of IDS alerts. However, such techniques are of no help in discovering novel attacks or variations of known attacks, something the human immune system (HIS) is capable of doing in its own specialised domain. This paper presents a novel immune algorithm for application to the IDS problem. The goal is to discover packets containing novel variations of attacks covered by an existing signature base.