Whole blood cytokine response as a measure of immunotoxicity

Activity of the Toll-like receptor ligands in children with high and low socioeconomic backgrounds

BACKGROUND

Adjuvants are essential in the induction of immunity by vaccines and interact with receptors, including the Toll-like receptors (TLRs). Responsiveness of these receptors differs between and within populations, which impacts vaccine effectiveness.

OBJECTIVE

Here we examine how the innate cytokine response towards TLR ligands differs between high and low socioeconomic status (SES) school-aged children from Makassar, Indonesia.

METHODS

We stimulated whole blood from children, of which 27 attended a high SES school and 27 children a low SES school, with ligands for TLR-2/1, -2/6, -3, -4, -5, -7, -9 and measured pro- (TNF) and anti-inflammatory (IL-10) cytokines released.

RESULTS

In the low SES there is an increased pro-inflammatory response after 24 h stimulation with TLR-2/1 ligand Pam3 and TLR-4 ligand LPS compared to the high SES. Comparison of the response to LPS after 24 h versus 72 h stimulation revealed that the pro-inflammatory response in the low SES after 24 h shifts to an anti-inflammatory response, whereas in the high SES the initial anti-inflammatory response shifts to a strong pro-inflammatory response after 72 h stimulation.

CONCLUSION

We observed differences in the TLR-mediated innate immune response between children attending low and high SES schools, which can have important implications for vaccine development.

Detection of SARS-CoV-2-independent immunoregulatory activity of COVID-19 convalescent plasma

BACKGROUND

Convalescent plasma has emerged as a potential specific treatment for coronavirus disease 2019 (COVID-19), since it contains severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) antibodies. Several studies are currently investigating the efficacy of convalescent plasma for treatment of COVID-19, with a focus on neutralizing antibodies. However, there is little information on whether convalescent plasma may contain additional immunoregulatory constituents produced by the blood donor during convalescence. Therefore, using a standardized whole blood assay employing synthetic toll-like receptor (TLR) ligands, we have investigated the immunoregulatory capacity of convalescent plasma in direct comparison to ABO-matched allogeneic control plasma.

STUDY DESIGN AND METHODS

Whole blood samples from healthy blood donors were collected, and autologous plasma was replaced by convalescent plasma or ABO-matched control plasma. Standardized innate immune triggering and monitoring was performed by adding different TLR ligands (Pam3CsK4 [TLR1/2], HKLM [TLR2], LPS [TLR4], flagellin [TLR5], ssRNA40 [TLR8], imiquimod [TLR7], and FSL-1 [TLR2/6]) and subsequent quantitative analysis of pro- and anti-inflammatory cytokines (IP-10, IL-1β, TNF-α, MCP-1, IL-6, IL-10, and IFN-γ) by cytometric bead array. Negative controls included unstimulated samples as well as samples spiked with autologous plasma.

RESULTS

COVID-19 convalescent plasma (CCP) significantly decreased pro-inflammatory cytokines production triggered by different TLR ligands in healthy donors as compared with healthy control plasma. IL-6, MCP-1, and IFN-γ represented the cytokines that are most frequently downregulated by convalescent plasma.

CONCLUSION

Our experiments reveal a potential novel, SARS-CoV-2-independent immunomodulatory activity of CCP, which may be beneficial for COVID-19 patients.

Physiologically relevant aspirin concentrations trigger immunostimulatory cytokine production by human leukocytes

Acetylsalicylic acid is a globally used non-steroidal anti-inflammatory drug (NSAID) with diverse pharmacological properties, although its mechanism of immune regulation during inflammation (especially at in vivo relevant doses) remains largely speculative. Given the increase in clinical perspective of Acetylsalicylic acid in various diseases and cancer prevention, this study aimed to investigate the immunomodulatory role of physiological Acetylsalicylic acid concentrations (0.005, 0.02 and 0.2 mg/ml) in a human whole blood of infection-induced inflammation. We describe a simple, highly reliable whole blood assay using an array of toll-like receptor (TLR) ligands 1–9 in order to systematically explore the immunomodulatory activity of Acetylsalicylic acid plasma concentrations in physiologically relevant conditions. Release of inflammatory cytokines and production of prostaglandin E₂ (PGE₂) were determined directly in plasma supernatant. Experiments demonstrate for the first time that plasma concentrations of Acetylsalicylic acid significantly increased TLR ligand-triggered IL-1β, IL-10, and IL-6 production in a dose-dependent manner. In contrast, indomethacin did not exhibit this capacity, whereas cyclooxygenase (COX)-2 selective NSAID, celecoxib, induced a similar pattern like Acetylsalicylic acid, suggesting a possible relevance of COX-2. Accordingly, we found that exogenous addition of COX downstream product, PGE₂, attenuates the TLR ligand-mediated cytokine secretion by augmenting production of anti-inflammatory cytokines and inhibiting release of pro-inflammatory cytokines. Low PGE₂ levels were at least involved in the enhanced IL-1β production by Acetylsalicylic acid.

Guidance on risk assessment of nanomaterials to be applied in the food and feed chain: human and animal health

The EFSA has updated the Guidance on risk assessment of the application of nanoscience and nanotechnologies in the food and feed chain, human and animal health. It covers the application areas within EFSA's remit, including novel foods, food contact materials, food/feed additives and pesticides. The updated guidance, now Scientific Committee Guidance on nano risk assessment (SC Guidance on Nano-RA), has taken account of relevant scientific studies that provide insights to physico-chemical properties, exposure assessment and hazard characterisation of nanomaterials and areas of applicability. Together with the accompanying Guidance on Technical requirements for regulated food and feed product applications to establish the presence of small particles including nanoparticles (Guidance on Particle-TR), the SC Guidance on Nano-RA specifically elaborates on physico-chemical characterisation, key parameters that should be measured, methods and techniques that can be used for characterisation of nanomaterials and their determination in complex matrices. The SC Guidance on Nano-RA also details aspects relating to exposure assessment and hazard identification and characterisation. In particular, nanospecific considerations relating to in vitro/in vivo toxicological studies are discussed and a tiered framework for toxicological testing is outlined. Furthermore, in vitro degradation, toxicokinetics, genotoxicity, local and systemic toxicity as well as general issues relating to testing of nanomaterials are described. Depending on the initial tier results, additional studies may be needed to investigate reproductive and developmental toxicity, chronic toxicity and carcinogenicity, immunotoxicity and allergenicity, neurotoxicity, effects on gut microbiome and endocrine activity. The possible use of read-across to fill data gaps as well as the potential use of integrated testing strategies and the knowledge of modes or mechanisms of action are also discussed. The Guidance proposes approaches to risk characterisation and uncertainty analysis.

An international validation study of the IL-2 Luc assay for evaluating the potential immunotoxic effects of chemicals on T cells and a proposal for reference data for immunotoxic chemicals

To evaluate the immunotoxic effects of xenobiotics, we have established the Multi-ImmunoTox assay, in which three stable reporter cell lines are used to evaluate the effects of chemicals on the IL-2, IFN-γ, IL-1β and IL-8 promoters. Here, we report the official validation study of the IL-2 luciferase assay (IL-2 Luc assay). In the Phase I study that evaluated five coded chemicals in three sets of experiments, the average within-laboratory reproducibility was 86.7%. In the Phase II study, 20 coded chemicals were evaluated at multiple laboratories. In the combined results of the Phase I and II studies, the between-laboratory reproducibility was 80.0%. These results suggested that the IL-2 Luc assay was reproducible both between and within laboratories. To determine the predictivity, we collected immunotoxicological information and constructed the reference data by classifying the chemical into immunotoxic compounds targeting T cells or others according to previously reported criteria. When compared with the reference data, the average predictivity of the Phase I and II studies was 75.0%, while that of additional 60 chemicals examined by the lead laboratory was 82.5%. Although the IL-2 Luc assay alone is not sufficient to predict immunotoxicity, it will be a useful tool when combined with other immune tests.

Guidance on risk assessment of the application of nanoscience and nanotechnologies in the food and feed chain: Part 1, human and animal health

The European Food Safety Authority has produced this Guidance on human and animal health aspects (Part 1) of the risk assessment of nanoscience and nanotechnology applications in the food and feed chain. It covers the application areas within EFSA's remit, e.g. novel foods, food contact materials, food/feed additives and pesticides. The Guidance takes account of the new developments that have taken place since publication of the previous Guidance in 2011. Potential future developments are suggested in the scientific literature for nanoencapsulated delivery systems and nanocomposites in applications such as novel foods, food/feed additives, biocides, pesticides and food contact materials. Therefore, the Guidance has taken account of relevant new scientific studies that provide more insights to physicochemical properties, exposure assessment and hazard characterisation of nanomaterials. It specifically elaborates on physicochemical characterisation of nanomaterials in terms of how to establish whether a material is a nanomaterial, the key parameters that should be measured, the methods and techniques that can be used for characterisation of nanomaterials and their determination in complex matrices. It also details the aspects relating to exposure assessment and hazard identification and characterisation. In particular, nanospecific considerations relating to in vivo/in vitro toxicological studies are discussed and a tiered framework for toxicological testing is outlined. It describes in vitro degradation, toxicokinetics, genotoxicity as well as general issues relating to testing of nanomaterials. Depending on the initial tier results, studies may be needed to investigate reproductive and developmental toxicity, immunotoxicity, allergenicity, neurotoxicity, effects on gut microbiome and endocrine activity. The possible use of read‐across to fill data gaps as well as the potential use of integrated testing strategies and the knowledge of modes/mechanisms of action are also discussed. The Guidance proposes approaches to risk characterisation and uncertainty analysis, and provides recommendations for further research in this area.

This publication is linked to the following EFSA Supporting Publications article: http://onlinelibrary.wiley.com/doi/10.2903/sp.efsa.2018.EN-1430/full

Immune responses in the aquatic gastropod Lymnaea stagnalis under short-term exposure to pharmaceuticals of concern for immune systems: Diclofenac, cyclophosphamide and cyclosporine A

This is a pioneering study in the ecotoxicological assessment of immunotoxic effects of the three selected drugs of concern to a freshwater gastropod species. Lymnaea stagnalis was exposed in the laboratory for 3 days to three drugs used for immune systems: diclofenac (nonsteroidal anti-inflammatory drug), cyclophosphamide (anti-cancer immunosuppressive drug) or cyclosporine A (anti-xenograft immunosuppressive drug). Exposure ranges included environmental realistic (1-10μgL^-1) and therapeutic concentrations (100-1000μgL^-1). At the end of exposure times, the immune parameters of individual snails were measured: hemocyte density and viability, hemocyte phagocytosis capacity and hemocyte-related oxidative activities (basal and NADPH-oxidase stimulated with zymosan particles). Diclofenac and cyclosporine A induced immune responses, although the effects were not strong. No immunosuppression was observed. Such subtle immunomodulations bring further interrogations regarding their long-term immunotoxicity and possible resulting tradeoffs with life-history traits. On the other hand, the prodrug cyclophosphamide did not induce significant immune responses. Since metabolism pathways differ greatly between vertebrates and invertebrates, this study also suggests that relevant vertebrate metabolites should be included in the immunotoxicity assessment of pharmaceuticals in non-target invertebrate species. Finally, the possible interactive effects of these pharmaceuticals sharing similar modes of action or effects features should also be explored.

Pre-clinical immunotoxicity studies of nanotechnology-formulated drugs: Challenges, considerations and strategy

Assorted challenges in physicochemical characterization, sterilization, depyrogenation, and in the assessment of pharmacology, safety, and efficacy profiles accompany pre-clinical development of nanotechnology-formulated drugs. Some of these challenges are not unique to nanotechnology and are common in the development of other pharmaceutical products. However, nanoparticle-formulated drugs are biochemically sophisticated, which causes their translation into the clinic to be particularly complex. An understanding of both the immune compatibility of nanoformulations and their effects on hematological parameters is now recognized as an important step in the (pre)clinical development of nanomedicines. An evaluation of nanoparticle immunotoxicity is usually performed as a part of a traditional toxicological assessment; however, it often requires additional in vitro and in vivo specialized immuno- and hematotoxicity tests. Herein, I review literature examples and share the experience with the NCI Nanotechnology Characterization Laboratory assay cascade used in the early (discovery-level) phase of pre-clinical development to summarize common challenges in the immunotoxicological assessment of nanomaterials, highlight considerations and discuss solutions to overcome problems that commonly slow or halt the translation of nanoparticle-formulated drugs toward clinical trials. Special attention will be paid to the grand-challenge related to detection, quantification and removal of endotoxin from nanoformulations, and practical considerations related to this challenge.

Immunostimulatory effects of RACK1 pseudosubstrate in human leukocytes obtained from young and old donors

Aims of this study were to investigate the ability of RACK1 pseudosubstrate alone or in combination with classical immune stimuli to activate human leukocytes, and to restore age-associated immune defects.A total of 25 donors (17 old donors, 77-79 yrs; 8 young donors, 25-34 yrs) were enrolled. To evaluate the effect of RACK1 pseudosubstrate on cytokine production and CD86 expression the whole blood assay was used. Cultures were treated with RACK1 pseudosubstrate in the presence or absence of lipopolysaccharide (LPS) or phytohaemagglutinin (PHA) and incubated for 24 h or 48 h for LPS-induced CD86 expression, TNF-α, IL-6, IL-8, IL-10 production, and PHA-induced IL-4, IL-10, IFN-γ, respectively. RACK1 pseudosubstrate alone induced IL-6, IL-8, and CD86 expression in both young and old donors, and IFN-γ in old donors. In combination with LPS an increase in IL-8, IL-10 and TNF-α was observed, also resulting in restoration of age-associated defective production, while no changes in the other parameters investigated were found.Even if based on a small sample size, these results suggest the possibility to by-pass some of age-associated immune alterations, which may be beneficial in situations were natural immune stimulation is required, and highlight a different role of PKCβ in immune cells activation.

The in vitro effects of artificial and natural sweeteners on the immune system using whole blood culture assays

This article investigates the effects of commercially available artificial (aspartame, saccharin, sucralose) and natural sweeteners (brown sugar, white sugar, molasses) on the immune system. Human whole blood cultures were incubated with various sweeteners and stimulated in vitro with either phytohemagglutinin or endotoxin. Harvested supernatants were screened for cytotoxicity and cytokine release. Results showed that none of the artificial or natural sweeteners proved to be cytotoxic, indicating that no cell death was induced in vitro. The natural sweetener, sugar cane molasses (10 ug/mL), enhanced levels of the inflammatory biomarker IL-6 while all artificial sweeteners (10 ug/mL) revealed a suppressive effect on IL-6 secretion (P < 0.001). Exposure of blood cells to sucralose-containing sweeteners under stimulatory conditions reduced levels of the biomarker of humoral immunity, Interleukin-10 (P < 0.001). The cumulative suppression of Interleukin-6 and Interleukin-10 levels induced by sucralose may contribute to the inability in mounting an effective humoral response when posed with an exogenous threat.

A human in vitro whole blood assay to predict the systemic cytokine response to therapeutic oligonucleotides including siRNA

Therapeutic oligonucleotides including siRNA and immunostimulatory ligands of Toll-like receptors (TLR) or RIG-I like helicases (RLH) are a promising novel class of drugs. They are in clinical development for a broad spectrum of applications, e.g. as adjuvants in vaccines and for the immunotherapy of cancer. Species-specific immune activation leading to cytokine release is characteristic for therapeutic oligonucleotides either as an unwanted side effect or intended pharmacology. Reliable in vitro tests designed for therapeutic oligonucleotides are therefore urgently needed in order to predict clinical efficacy and to prevent unexpected harmful effects in clinical development. To serve this purpose, we here established a human whole blood assay (WBA) that is fast and easy to perform. Its response to synthetic TLR ligands (R848: TLR7/8, LPS: TLR4) was on a comparable threshold to the more time consuming peripheral blood mononuclear cell (PBMC) based assay. By contrast, the type I IFN profile provoked by intravenous CpG-DNA (TLR9 ligand) in humans in vivo was more precisely replicated in the WBA than in stimulated PBMC. Since Heparin and EDTA, but not Hirudin, displaced oligonucleotides from their delivery agent, only Hirudin qualified as the anticoagulant to be used in the WBA. The Hirudin WBA exhibited a similar capacity as the PBMC assay to distinguish between TLR7-activating and modified non-stimulatory siRNA sequences. RNA-based immunoactivating TLR7/8- and RIG-I-ligands induced substantial amounts of IFN-α in the Hirudin-WBA dependent on delivery agent used. In conclusion, we present a human Hirudin WBA to determine therapeutic oligonucleotide-induced cytokine release during preclinical development that can readily be performed and offers a close reflection of human cytokine response in vivo.

Understanding the correlation between in vitro and in vivo immunotoxicity tests for nanomedicines

Preclinical characterization of novel nanotechnology-based formulations is often challenged by physicochemical characteristics, sterility/sterilization issues, safety and efficacy. Such challenges are not unique to nanomedicine, as they are common in the development of small and macromolecular drugs. However, due to the lack of a general consensus on critical characterization parameters, a shortage of harmonized protocols to support testing, and the vast variety of engineered nanomaterials, the translation of nanomedicines into clinic is particularly complex. Understanding the immune compatibility of nanoformulations has been identified as one of the important factors in (pre)clinical development and requires reliable in vitro and in vivo immunotoxicity tests. The generally low sensitivity of standard in vivo toxicity tests to immunotoxicities, inter-species variability in the structure and function of the immune system, high costs and relatively low throughput of in vivo tests, and ethical concerns about animal use underscore the need for trustworthy in vitro assays. Here, we consider the correlation (or lack thereof) between in vitro and in vivo immunotoxicity tests as a mean to identify useful in vitro assays. We review literature examples and case studies from the experience of the NCI Nanotechnology Characterization Lab, and highlight assays where predictability has been demonstrated for a variety of nanomaterials and assays with high potential for predictability in vivo.

Anti-inflammatory effect of fluvastatin on IL-8 production induced by Pseudomonas aeruginosa and Aspergillus fumigatus antigens in cystic fibrosis

BACKGROUND

Early in life, patients with cystic fibrosis (CF) are infected with microorganisms including bacteria and fungi, particularly Pseudomonas aeruginosa and Aspergillus fumigatus. Since recent research has identified the anti-inflammatory properties of statins (besides their lipid-lowering effects), we investigated the effect of fluvastatin on the production of the potent neutrophil chemoattractant chemokine, IL-8, in whole blood from CF patients, stimulated by Pseudomonas aeruginosa (LPS) and Aspergillus fumigatus (AFA) antigens.

RESULTS

Whole blood from adult patients with CF and from healthy volunteers was collected at the Rennes University Hospital (France). Blood was pretreated for 1 h with fluvastatin (0-300 µM) and incubated for 24 h with LPS (10 µg/mL) and/or AFA (diluted 1/200). IL-8 protein levels, quantified by ELISA, were increased in a concentration-dependent manner when cells were stimulated by LPS or AFA. Fluvastatin strongly decreased the levels of IL-8, in a concentration-dependent manner, in whole blood from CF patients. However, its inhibitory effect was decreased or absent in whole blood from healthy subjects. Furthermore, the inhibition induced by fluvastatin in CF whole blood was reversed in the presence of intermediates within the cholesterol biosynthesis pathway, mevalonate, farnesyl pyprophosphate or geranylgeranyl pyrophosphate that activate small GTPases by isoprenylation.

CONCLUSIONS

For the first time, the inhibitory effects of fluvastatin on CF systemic inflammation may reveal the important therapeutic potential of statins in pathological conditions associated with the over-production of pro-inflammatory cytokines and chemokines as observed during the manifestation of CF. The anti-inflammatory effect could be related to the modulation of the prenylation of signalling proteins.

In vitro cytokine release from human peripheral blood mononuclear cells in the assessment of the immunotoxic potential of chemicals

Alternative methods to the use of animals in testing of chemicals are needed. We investigated if the immunotoxic potential of 12 dietary toxicants could be predicted from effects on cytokine release from human peripheral blood mononuclear cells (PBMC) after in vitro exposure. Nine cytokines were selected to reflect different types of immune responses. The toxicants were classified as immunotoxic or non-immunotoxic substances according to the published in vivo data. Isolated human PBMC were exposed for 20 h to three concentrations of each of the 12 substances in the presence of human liver S9 fraction. After further incubation of PBMC in fresh medium containing the mitogen phytohemagglutinin (PHA, 10 μg/ml) for 48 h, release of the nine selected cytokines into the supernatant as well as cell proliferation were measured by Luminex technology™ and the BrdU incorporation assay, respectively. All 12 substances investigated affected the release of one or more cytokines, and each of the substances showed different cytokine release patterns. Within the limitations of the study design, the present study suggests that the effect of the substances on mitogen-induced cytokine release from PBMC cannot predict their immunotoxic potential, but may be useful in mechanistic studies.

Safety and immunotoxicity assessment of immunomodulatory monoclonal antibodies

Most therapeutic monoclonal antibodies (mAbs) licensed for human use or in clinical development are indicated for treatment of patients with cancer and inflammatory/autoimmune disease and as such, are designed to directly interact with the immune system. A major hurdle for the development and early clinical investigation of many of these immunomodulatory mAbs is their inherent risk for adverse immune-mediated drug reactions in humans such as infusion reactions, cytokine storms, immunosuppression and autoimmunity. A thorough understanding of the immunopharmacology of a mAb in humans and animals is required to both anticipate the clinical risk of adverse immunotoxicological events and to select a safe starting dose for first-in-human (FIH) clinical studies. This review summarizes the most common adverse immunotoxicological events occurring in humans with immunomodulatory mAbs and outlines non-clinical strategies to define their immunopharmacology and assess their immunotoxic potential, as well as reduce the risk of immunotoxicity through rational mAb design. Tests to assess the relative risk of mAb candidates for cytokine release syndrome, innate immune system (dendritic cell) activation and immunogenicity in humans are also described. The importance of selecting a relevant and sensitive toxicity species for human safety assessment in which the immunopharmacology of the mAb is similar to that expected in humans is highlighted, as is the importance of understanding the limitations of the species selected for human safety assessment and supplementation of in vivo safety assessment with appropriate in vitro human assays. A tiered approach to assess effects on immune status, immune function and risk of infection and cancer, governed by the mechanism of action and structural features of the mAb, is described. Finally, the use of immunopharmacology and immunotoxicity data in determining a minimum anticipated biologic effect Level (MABEL) and in the selection of safe human starting dose is discussed.

Metabolic endotoxemia and saturated fat contribute to circulating NGAL concentrations in subjects with insulin resistance

OBJECTIVE

Lipocalin-2 (neutrophil gelatinase-associated lipocalin, NGAL) is an innate immune system protein that has been linked to insulin resistance and obesity, but the mechanisms behind these associations are poorly known. We hypothesized that endotoxin (lipopolysaccharide, LPS) and fat intake were in the background of these associations.

DESIGN

We studied four cohorts: (1) a cross-sectional study in 194 subjects; (2) the changes in NGAL concentration induced by diet and weight loss in 36 obese women (with circadian rhythm in 8 of them); (3) the effects of acute fat intake on circulating NGAL concentration in 42 morbidly obese subjects; and (4) LPS-induced NGAL secretion ex vivo (whole blood and adipose tissue explants).

RESULTS

Serum NGAL concentration was significantly associated with fasting triglycerides and LPS-binding protein in patients with type 2 diabetes. In obese subjects, the intake of saturated fatty acids was the factor that best explained the variance of NGAL changes after weight loss (contributing independently to 14% of NGAL variance). In fact, weight loss significantly changed the circadian rhythm of NGAL. The acute increase in circulating NGAL after fat overload was significantly associated with fasting insulin (r=0.52, P<0.001), homeostasis model assessment of insulin resistance (HOMA-IR) (r=0.36, P=0.02) and post-load triglyceride concentrations (r=0.38, P=0.018). LPS-induced NGAL secretion from adipose tissue explants did not change significantly, but LPS led to a significant increase in NGAL concentration in the whole blood obtained from patients with type 2 diabetes.

CONCLUSION

Metabolic endotoxemia and saturated fat might contribute to circulating NGAL concentration in patients with insulin resistance.

Decreased circulating lactoferrin in insulin resistance and altered glucose tolerance as a possible marker of neutrophil dysfunction in type 2 diabetes

CONTEXT

Lactoferrin is an innate immune system protein with multiple beneficial health activities.

OBJECTIVE

To gain insight in the interaction between innate immune system and metabolic disturbances (obesity and insulin resistance), we investigated the relationship between circulating lactoferrin and chronic inflammation-associated insulin resistance according glucose tolerance status in Caucasian population.

DESIGN, SETTING, PARTICIPANTS, AND MAIN OUTCOME MEASURES

Circulating nonstressed lactoferrin (ELISA), metabolic variables, and inflammatory markers were measured in 229 men, 94 with normal (NGT) and 135 with altered glucose tolerance (AGT). Lactoferrin secretion by neutrophil was investigated in whole-blood culture (four young NGT subjects, four older NGT subjects, and four patients with type 2 diabetes) under microbial lipopolysaccharide (LPS) with IL-6 and rosiglitazone treatment. We also tested the lactoferrin action in THP-1 cells under LPS stimulus.

RESULTS

Circulating lactoferrin was significantly decreased in patients with AGT (431.5 +/- 187.5 vs. 493.5 +/- 238.9 ng/ml, P = 0.02). In addition, circulating lactoferrin was negatively associated with hyperglycemia and obesity measures and positively with insulin sensitivity. Lactoferrin was negatively related to inflammatory markers, especially in AGT subjects. In ex vivo experiments, we found a significant decrease in LPS-induced lactoferrin release from neutrophils in subjects with type 2 diabetes. IL-6 coincubation decreased LPS-induced lactoferrin release in NGT subjects (P < 0.001). Finally, rosiglitazone treatment led to increased lactoferrin secretion (398 +/- 193 vs. 280.1 +/- 104.9 ng/ml, P < 0.0001). Lactoferrin decreased nuclear factor-kappabeta activation and IL-6, IL-8, and macrophage chemoattractant protein-1 expression under LPS challenge.

CONCLUSIONS

Decreased circulating lactoferrin levels may play a role in chronic low level inflammation-associated insulin resistance.

Immunotoxicology: Opportunities for Non-animal Test Development

At present, several animal-based assays are used to assess immunotoxic effects such as immunosuppression and sensitisation. The use of whole animals, however, presents several secondary issues, including expense, ethical concerns and relevance to human risk assessment. There is a growing belief that non-animal approaches can eliminate these issues without impairing human safety, provided that biological markers are available to identify the immunotoxic potentials of new chemicals to which humans may be exposed. Driven by the 7th Amendment to the EU Cosmetics Directive, the new EU policy on chemicals (the REACH system), proposals to update the European legislation on the protection of animals used in research, and emerging visions and strategies for predicting toxicity, such in vitro methods are likely to play a major role in the near future. The realisation that the immune system can be the target of many chemicals, resulting in a range of adverse effects on the host's health, has raised serious concerns from the public and within the regulatory agencies. Hypersensitivity and immunosuppression are considered the primary focus for developing in vitro methods in immunotoxicology. However, in vitro assays to detect immunostimulation and autoimmunity are also needed. This review of the state-of-the-art in the field of in vitro immunotoxicity, reveals a lack of cell-based immunotoxicity assays for predicting the toxicity of xenobiotics toward the immune system in a simple, fast, economical and reliable way.

Measurement of cytokine production using whole blood

Whole blood (WB) ex vivo stimulation assays are useful for measuring cytokine responses due to the easy access of samples from healthy donors and patients and the minimal processing of the sample required. Because the assay mimics the natural environment, WB culture may be the best milieu in which to study cell activation and cytokine production in vitro. Whole blood stimulation has been used to investigate the cellular responsiveness to a variety of stimuli, including bacterial endotoxin (LPS), antigens, allergens, and antibiotics. Various clinical uses of whole blood stimulation assays have been suggested, including the assessment of autoimmune diseases, the monitoring of drug and vaccine efficacy, and immunotoxicity. Thus, whole blood cell culture may be useful in studying the biological effects of potential allergenic and/or antigenic substances or drugs on immune cell activation and cytokine secretion.

Expression of Th1/Th2 cytokines in human blood after in vitro treatment with chlorpyrifos, and its metabolites, in combination with endotoxin LPS and allergen Der p1

Exposure to organophosphate (OP) pesticides has been associated with respiratory symptoms and may be related to asthma; however, few studies have examined the molecular basis for these associations. Asthma and allergic disorders are characterized by elevated Th2 cytokines (IL-4, IL-5, IL-13), whereas the chronic inflammatory response in asthmatic airways is maintained by Th1 cytokine IFN-gamma. The goal of this in vitro study was to examine the effects of OP chlorpyrifos (CPF), and its metabolites chlorpyrifos-oxon (CPO) and 3,5,6-trichloro-2-pyridinol (TCP), singly, and in combination with endotoxin lipopolysaccharide (LPS) or house dust mite Dermatophagoides pteronyssinus (Der p1) allergen, on expression of IFN-gamma and IL-4, Th1 and Th2 signature cytokines, respectively. Cytokine expression was measured by ELISA and flow cytometry. Human blood cultures were treated with CPF/CPO/TCP (1-1000 microg ml(-1)) and LPS (1.5-2.5 microg ml(-1)) or Der p1 (200 AU ml(-1)) and supernatants were collected at 48 h. Pesticides CPF, CPO and TCP did not induce cytokine expression in vitro, while LPS and Der p1 induced IFN-gamma and IL-4 expression, respectively. Whole blood cultures treated with low doses of CPO (1 and 10 microg ml(-1)), in combination with LPS, expressed higher levels of IFN-gamma than LPS alone (P < 0.05). While CPO increased LPS-dependent induction of IFN-gamma, CPO treatment did not alter Der p1 induction of IL-4. The interaction between CPO and LPS, which results in an increased type 1 immune response, should be investigated further, particularly since the combination of OP pesticides and endotoxin is common in rural, agricultural communities.

In vitro tests to evaluate immunotoxicity: A preliminary study

The implementation of Registration, Evaluation and Authorisation of new and existing Chemicals (REACH) will increase the number of laboratory animals used, if alternative methods will not be available. In the meantime, REACH promotes the use of in vitro tests and, therefore, a set of appropriated alternative testing methods and assessment strategies are needed. The immune system can be a target for many chemicals including environmental contaminants and drugs with potential adverse effects on human health. The aim of this study was to evaluate the predictivity of a set of in vitro assays to detect immunosuppression. The tests have been performed on human, rat and murine cells. Different endpoints have been assessed: cytotoxicity, cytokine release, myelotoxicity and mitogen responsiveness. For each of these endpoints IC50s values have been calculated. Six chemical substances, representative of the full range of in vivo responses and for which good human and/or animal data are available either from databases or literature, have been selected: two chemicals classified as not immunotoxic (Urethane and Furosemide), and four (tributyltin chloride (TBTC), Verapamil, Cyclosporin A, Benzo(a)pyrene) with different effect on immune system. All the tests confirmed the strong immunotoxic effect of TBTC as well as they confirmed the negative controls. For one chemical (Verapamil) the IC50 is similar through the different tests. The IC50s obtained with the other chemicals depend on the endpoints and on the animal species. The clonogenic test (CFU-GM) and the mitogen responsiveness showed similar IC50s between human and rodent cells except for Cyclosporin A and TBTC. All different tests classified the compounds analyzed in the same way.

Whole blood TNF-alpha production as a sensitive measure for immunotoxicity of anticancer drugs

The immunotoxicity of anticancer drugs has been measured with whole blood TNF-alpha production induced by LPS-stimulation. Cis-platinum (CDDP) or 5-fluorouracil (5-FU) was given intravenously to mice once a day for three days. The amount of produced-TNF-alpha lowered significantly in CDDP 2 mg/kg and 5 mg/kg, while the number of leukocytes scarcely changed even when a significant decrease in body weight was observed at the dose of 5 mg/kg. On the other hand, 5-FU 20 mg/kg also caused a significant decline in the amount of produced TNF-alpha but it showed no apparent effects on the number of leukocytes and the body weight. These results indicate that LPS-induced TNF-alpha production is a more sensitive measure than leukocyte count used conventionally to detect the immunotoxicity of two anticancer drugs, CDDP and 5-FU, and suggest that it might be a more practical index for hazard identification in clinical treatment with anticancer drugs.

Impact of immunomodulatory oligodeoxynucleotides on cytokine production in the lipopolysaccharide-stimulated human whole blood model

BACKGROUND

In studying potential immunotherapeutics for sepsis, we used a lipopolysaccharide (LPS)-stimulated whole blood model to test the immunomodulating capacity of cytosine-phospho-guanine oligodeoxynucleotides (CpG ODNs). We hypothesized that CpG ODNs would have considerable counterinflammatory effects on LPS-induced cytokine production.

METHODS

We administered 4 micromol/L of CpG ODNs (2216, D19, 2006, K3, or 1668) or guanine-phospho-cytosine (GpC) ODNs (control D or control K) immediately after LPS (10 ng/mL) stimulation of heparinized human whole blood. Samples were incubated for 1, 3, 6, 12, and 24 hours. Media and LPS were used as negative and positive controls. Cell-free supernatants were obtained and evaluated for interferon gamma (IFN-gamma), interleukin (IL)-12(p40), tumor necrosis factor alpha, IL-6, IL-10, IFN-alpha, IL-8, and IL-1beta by ELISA.

RESULTS

Compared to LPS alone, significantly reduced levels of IFN-gamma, IL-12(p40), tumor necrosis factor alpha, and IL-6 were associated with both CpG and GpC ODNs administration to LPS-stimulated whole blood. IL-10 levels were concomitantly increased. However, IFN-alpha generation was CpG specific as was increased IL-8 levels. Lastly, only 2216 was associated with decreased IL-1beta levels.

CONCLUSIONS

CpG ODNs and GpC ODNs in the LPS-stimulated whole blood model demonstrate differential counterinflammatory effects, but only CpG ODNs were associated with proinflammatory cytokine production. With further examination, we may find that these observed immunomodulatory differences could potentially be exploited for therapeutic benefit.

Plasma interferon-gamma and interleukin-10 concentrations in systemic meningococcal disease compared with severe systemic Gram-positive septic shock

OBJECTIVE

To analyze plasma interferon-gamma and interleukin-10 concentrations in patients with systemic meningococcal disease and patients with severe Gram-positive septic shock caused by Streptococcus pneumoniae or Staphylococcus aureus. To study the in vitro cytokine (interferon-gamma and interleukin-10) responses in a whole blood model boosted with heat-killed Neisseria meningitidis, S. pneumoniae, and S. aureus before and after treatment with recombinant interleukin-10 or recombinant interferon-gamma.

DESIGN

Experimental study.

SETTING

Laboratory.

SUBJECTS

Plasma samples were collected from patients with systemic meningococcal disease (n = 66) and patients with severe Gram-positive septic shock caused by S. pneumoniae (n = 4) or S. aureus (n = 3).

INTERVENTIONS

Whole blood was boosted with heat-killed N. meningitidis, S. pneumoniae, and S. aureus (1 x 106 colony forming units/mL), and plasmas were analyzed for interleukin-10 or interferon-gamma at 0, 5, 12, and 24 hrs. Furthermore, recombinant interleukin-10 or recombinant interferon-gamma was added before bacteria, and the effect on the secretion of interferon-gamma and interleukin-10, respectively, was analyzed after 24 hrs.

MEASUREMENTS AND MAIN RESULTS

The median concentration of interferon-gamma was 15 pg/mL and of interleukin-10 was 10,269 pg/mL in patients with meningococcal septic shock (n = 24) compared with median interferon-gamma concentration of 3400 pg/mL and interleukin-10 concentration of 465 pg/mL in patients with severe Gram-positive shock (p =.001). Increased interferon-gamma concentrations were associated with case fatality (p =.011). In a whole blood model we demonstrated that 1 x 106 colony forming units/mL of N. meningitidis induced more interleukin-10 but less interferon-gamma than S. pneumoniae. S. aureus induced minimal secretion of both cytokines. Recombinant interleukin-10 efficiently down-regulated the secretion of interferon-gamma, and vice versa, as shown in a whole blood model.

CONCLUSION

We speculate whether high concentrations of interleukin-10 contribute to the low concentrations of interferon-gamma in fulminant meningococcal septicemia. In addition, it appears as if interferon-gamma plays a minor role in the pathophysiology of meningococcal septic shock.

Determination of the eicosanoid response to inflammatory stimuli in whole blood and its pharmacological modulation ex vivo

Recognition of pathogens by immune cells initiates the release of numerous signaling molecules, including cytokines and eicosanoids. Here, we describe a simple procedure by which eicosanoids such as prostaglandin E(2) (PGE(2)), leukotriene B(4) (LTB(4)) and thromboxane B(2) (TxB(2)) can be measured using commercial enzyme immunoassays (EIAs) in the supernatant of whole blood stimulated with inflammatory stimuli. This is illustrated for numerous stimuli. The kinetics by which lipopolysaccharide (LPS) induces cyclooxygenase (COX)-2 expression in this setup were determined by quantitative reverse transcription polymerase chain reaction (RT-PCR). The eicosanoid response of the blood of 160 healthy volunteers to 1 microg/ml LPS was measured. To determine whether the action of a drug in vivo is represented ex vivo in the eicosanoid response of blood, one volunteer took a standard dose of a number of commercially available cyclooxygenase inhibitors on different days and the eicosanoid response of his blood to LPS was determined before ingestion as well as 2 and 6 h afterwards. The efficacy of the different pharmaceuticals on cyclooxygenase but not lipoxygenase products or cytokines could be monitored ex vivo. Similarly, ex vivo eicosanoid release was measured in blood from 10 volunteers who had taken 50 mg flurbiprofen. The method described extends approaches for studying whole blood cytokine release to the lipid mediators formed from arachidonic acid. These important signaling molecules represent targets for pharmacological intervention, which can now be monitored in vitro, as well as ex vivo employing the same model. Furthermore, the assay could be used to characterize the immune status of patient groups or to monitor the course of disease.

A model of human whole blood lymphokine release for in vitro and ex vivo use

Endotoxin (lipopolysaccharide, LPS) inducible cytokine release by human whole blood is increasingly used to model inflammatory responses in vitro, to detect the presence of pyrogenic contaminations as well as to monitor disease states or immunomodulatory treatments ex vivo. However, the LPS-stimulated blood model primarily allows the assessment of monocyte responses. Here, a whole blood model was established which allows assessment of lymphocyte responses. Four different superantigens, namely staphylococcal enterotoxin A and B (SEA, SEB), toxic shock syndrome toxin-1 (TSST-1) or streptococcal exotoxin A (SPEA) were tested with respect to the induction of lymphokine release. All superantigens were capable of inducing significant amounts of the lymphokines interferon-gamma (IFNgamma), interleukin 2 (IL-2), IL-4, IL-5, IL-13 and tumor necrosis factor beta (TNFbeta) after 72 h of incubation. Concentration-dependencies and kinetics were determined. Blood from 160 healthy donors was used to assess the variability of SEB-inducible lymphokine release. Interindividual differences were more pronounced compared to LPS-inducible monokine release. However, the individual response was maintained when blood from six donors was tested once a week for 8 weeks, suggesting that the individual response represents a donor characteristic. The model appears to be suitable for the evaluation of immunomodulatory agents in vitro as well as ex vivo.

Evaluation and prevalidation of an immunotoxicity test based on human whole-blood cytokine release

Immunotoxicology is a relatively new field in toxicology, and is one of emerging importance, because immunotoxicity appears to contribute to the development of cancer, autoimmune disorders, allergies and other diseases. At present, there is a lack of human cell-based immunotoxicity assays for predicting the toxicity of xenobiotics toward the immune system in a simple, fast, economical and reliable way. Existing immunotoxicity tests are mainly performed in animals, although species differences favour human-based testing. Whole-blood cytokine release models have attracted increasing interest, and are broadly used for pharmacological in vitro and ex vivo studies, as well as for pyrogenicity testing. We have adapted those methods for immunotoxicity testing, to permit the potency testing of immunostimulants and immunosuppressants. Following stimulation with a lipopolysaccharide or staphylococcal enterotoxin B, monocytes and lymphocytes release interleukin-1beta and interleukin-4, respectively. Thirty-one pharmaceutical compounds, with known effects on the immune system, were used to optimise and standardise the method, by analysing their effects on cytokine release. The in vitro results were expressed as IC50 values for immunosuppression, and SC(4) (fourfold increase) values for immunostimulation, and compared with therapeutic serum concentrations of the compounds in patients, and in vivo LD50 values from animal studies. The in vitro results correlated well with the in vivo data, so the test appears to reflect immunomodulation. Results were reproducible (CV = 20 +/- 5%), and the method could be transferred to another laboratory (r(2) = 0.99). We therefore propose this method for further validation and for use in immunotoxicity testing strategies.

Evaluation of immune functions of rainbow trout (Oncorhynchus mykiss)--how can environmental influences be detected?

In fish, the first line of defense against infectious microorganisms is based on a broad range of nonspecific humoral and cellular immune mechanisms ("innate immunity") which without prior specific activation can act in forming a more static barrier (Fish Shellfish Immunol. 10 (2000) 243; Dev. Comp. Immunol. 25 (2001) 827). This natural resistance is normally effective enough to protect fish from infectious diseases until specific immune responses are being induced (Fig. 1; Dev. Comp. Immunol. 25 (2001) 841). Healthy fish exhibit both nonspecific and specific immune responses depending directly on environmental temperature. Pollution of the natural aquatic environment with industrial or agricultural sewage is an important immunosuppressing factor resulting in higher susceptibility to infectious diseases. To date, the possible immunotoxicity of a substance is evaluated using quantification of humoral factors like lysozyme, complement, C-reactive protein or total immunoglobulins but less often using functional assays. Furthermore, most of the functional assays (phagocytosis, respiratory burst, proliferative response) are based on the measurement of the response of resting but not of specific activated immune cells. However, the physiological responses of the immune system to an infection are based on a complex, stepwise activation and proliferation, especially of the specific immune functions after first contact to the microorganisms. In this report we describe in vitro methods for the evaluation of cellular immune functions of different leukocyte populations after specific in vivo triggering of the immune system. Parameters to be evaluated are activation and proliferation of leukocyte populations, phagocytosis and respiratory burst, secretion of antigen-specific antibodies and specific cell-mediated cytotoxicity. Furthermore, challenge models with bacterial (Aeromonas salmonicida) and viral pathogens (Viral Haemorrhagic Septicemia Virus, VHSV) are presented.