Beryllium, an adjuvant that promotes gamma interferon production

Adaptive Immunity in Pulmonary Sarcoidosis and Chronic Beryllium Disease

Pulmonary sarcoidosis and chronic beryllium disease (CBD) are inflammatory granulomatous lung diseases defined by the presence of non-caseating granulomas in the lung. CBD results from beryllium exposure in the workplace, while the cause of sarcoidosis remains unknown. CBD and sarcoidosis are both immune-mediated diseases that involve Th1-polarized inflammation in the lung. Beryllium exposure induces trafficking of dendritic cells to the lung in a mechanism dependent on MyD88 and IL-1α. B cells are also recruited to the lung in a MyD88 dependent manner after beryllium exposure in order to protect the lung from beryllium-induced injury. Similar to most immune-mediated diseases, disease susceptibility in CBD and sarcoidosis is driven by the expression of certain MHCII molecules, primarily HLA-DPB1 in CBD and several HLA-DRB1 alleles in sarcoidosis. One of the defining features of both CBD and sarcoidosis is an infiltration of activated CD4+ T cells in the lung. CD4+ T cells in the bronchoalveolar lavage (BAL) of CBD and sarcoidosis patients are highly Th1 polarized, and there is a significant increase in inflammatory Th1 cytokines present in the BAL fluid. In sarcoidosis, there is also a significant population of Th17 cells in the lungs that is not present in CBD. Due to persistent antigen exposure and chronic inflammation in the lung, these activated CD4+ T cells often display either an exhausted or anergic phenotype. Evidence suggests that these T cells are responding to common antigens in the lung. In CBD there is an expansion of beryllium-responsive TRBV5.1+ TCRs expressed on pathogenic CD4+ T cells derived from the BAL of CBD patients that react with endogenous human peptides derived from the plexin A protein. In an acute form of sarcoidosis, there are expansions of specific TRAV12-1/TRBV2 T cell receptors expressed on BAL CD4+ T cells, indicating that these T cells are trafficking to and expanding in the lung in response to common antigens. The specificity of these pathogenic CD4+T cells in sarcoidosis are currently unknown.

Immunologic Effects of Beryllium Exposure

Metal-induced hypersensitivity is driven by T-cell sensitization to metal ions. Although numerous metals are associated with the development of diffuse parenchymal lung disease, beryllium-induced hypersensitivity is the best-studied to date. This review focuses on the interaction between innate and adaptive immunity that leads to the development of chronic beryllium disease. After beryllium exposure, activation of the innate immune system occurs through the engagement of pattern-recognition receptors. This activation leads to cell death, release of alarmins, and activation and migration of dendritic cells to lung-draining lymph nodes. These events culminate in the development of an adaptive immune response that is characterized by beryllium-specific, T-helper type 1-polarized, CD4⁺ T-cells and granuloma formation in the lung. The unique ability of beryllium to bind to human leukocyte antigen-DP molecules that express a glutamic acid at position 69 of the β-chain alters the charge and conformation of the human leukocyte antigen-DP-peptide complex. These changes induce post-translational modifications that are recognized as non-self. In essence, the ability of beryllium to create neoantigens underlies the genesis of chronic beryllium disease, and demonstrates the similarity between beryllium-induced hypersensitivity and autoimmunity.

The Formation and Function of Granulomas

Granulomas are organized aggregates of macrophages, often with characteristic morphological changes, and other immune cells. These evolutionarily ancient structures form in response to persistent particulate stimuli-infectious or noninfectious-that individual macrophages cannot eradicate. Granulomas evolved as protective responses to destroy or sequester particles but are frequently pathological in the context of foreign bodies, infections, and inflammatory diseases. We summarize recent findings that suggest that the granulomatous response unfolds in a stepwise program characterized by a series of macrophage activations and transformations that in turn recruit additional cells and produce structural changes. We explore why different granulomas vary and the reasons that granulomas are protective and pathogenic. Understanding the mechanisms and role of granuloma formation may uncover new therapies for the multitude of granulomatous diseases that constitute serious medical problems while enhancing the protective function of granulomas in infections.

Beryllium-Induced Hypersensitivity: Genetic Susceptibility and Neoantigen Generation

Chronic beryllium (Be) disease is a granulomatous lung disorder that results from Be exposure in a genetically susceptible host. The disease is characterized by the accumulation of Be-responsive CD4(+) T cells in the lung, and genetic susceptibility is primarily linked to HLA-DPB1 alleles possessing a glutamic acid at position 69 of the β-chain. Recent structural analysis of a Be-specific TCR interacting with a Be-loaded HLA-DP2-peptide complex revealed that Be is coordinated by amino acid residues derived from the HLA-DP2 β-chain and peptide and showed that the TCR does not directly interact with the Be(2+) cation. Rather, the TCR recognizes a modified HLA-DP2-peptide complex with charge and conformational changes. Collectively, these findings provide a structural basis for the development of this occupational lung disease through the ability of Be to induce posttranslational modifications in preexisting HLA-DP2-peptide complexes, resulting in the creation of neoantigens.

Comparative Safety of Vaccine Adjuvants: A Summary of Current Evidence and Future Needs

Use of highly pure antigens to improve vaccine safety has led to reduced vaccine immunogenicity and efficacy. This has led to the need to use adjuvants to improve vaccine immunogenicity. The ideal adjuvant should maximize vaccine immunogenicity without compromising tolerability or safety. Unfortunately, adjuvant research has lagged behind other vaccine areas such as antigen discovery, with the consequence that only a very limited number of adjuvants based on aluminium salts, monophosphoryl lipid A and oil emulsions are currently approved for human use. Recent strategic initiatives to support adjuvant development by the National Institutes of Health should translate into greater adjuvant choices in the future. Mechanistic studies have been valuable for better understanding of adjuvant action, but mechanisms of adjuvant toxicity are less well understood. The inflammatory or danger-signal model of adjuvant action implies that increased vaccine reactogenicity is the inevitable price for improved immunogenicity. Hence, adjuvant reactogenicity may be avoidable only if it is possible to separate inflammation from adjuvant action. The biggest remaining challenge in the adjuvant field is to decipher the potential relationship between adjuvants and rare vaccine adverse reactions, such as narcolepsy, macrophagic myofasciitis or Alzheimer's disease. While existing adjuvants based on aluminium salts have a strong safety record, there are ongoing needs for new adjuvants and more intensive research into adjuvants and their effects.

MyD88 dependence of beryllium-induced dendritic cell trafficking and CD4⁺ T-cell priming

Beryllium exposure results in beryllium hypersensitivity in a subset of exposed individuals, leading to granulomatous inflammation and fibrosis in the lung. In addition to its antigenic properties, beryllium has potent adjuvant activity that contributes to sensitization via unknown pathways. Here we show that beryllium induces cellular death and release of interleukin (IL)-1α and DNA into the lung. Release of IL-1α was inflammasome independent and required for beryllium-induced neutrophil recruitment into the lung. Beryllium enhanced classical dendritic cell (cDC) migration from the lung to draining lymph nodes (LNs) in an IL-1R-independent manner, and the accumulation of activated cDCs in the LN was associated with increased priming of CD4(+) T cells. DC migration was reduced in Toll-like receptor 9 knockout (TLR9KO) mice; however, cDCs in the LNs of TLR9-deficient mice were highly activated, suggesting a role for more than one innate receptor in the effects on DCs. The adjuvant effects of beryllium on CD4(+) T-cell priming were similar in wild-type, IL-1R-, caspase-1-, TLR2-, TLR4-, TLR7-, and TLR9-deficient mice. In contrast, DC migration, activation, and the adjuvant effects of beryllium were significantly reduced in myeloid differentiation primary response gene 88 knockout (MyD88KO) mice. Collectively, these data suggest that beryllium exposure results in the release of damage-associated molecular patterns that engage MyD88-dependent receptors to enhance pulmonary DC function.

p38 Mitogen-Activated Protein Kinase in beryllium-induced dendritic cell activation

Dendritic cells (DC) play a role in the regulation of immune responses to haptens, which in turn impact DC maturation. Whether beryllium (Be) is able to induce DC maturation and if this occurs via the MAPK pathway is not known. Primary monocyte-derived DCs (moDCs) models were generated from Be non-exposed healthy volunteers as a non-sensitized cell model, while PBMCs from BeS (Be sensitized) and CBD (chronic beryllium disease) were used as disease models. The response of these cells to Be was evaluated. The expression of CD40 was increased significantly (p<0.05) on HLA-DP Glu69+ moDCs after 100 μM BeSO₄-stimulation. BeSO₄ induced p38MAPK phosphorylation, while IκB-α was degraded in Be-stimulated moDCs. The p38 MAPK inhibitor SB203580 blocked Be-induced NF-κB activation in moDCs, suggesting that p38MAPK and NF-κB are dependently activated by BeSO₄. Furthermore, in BeS and CBD subjects, SB203580 downregulated Be-stimulated proliferation in a dose-dependent manner, and decreased Be-stimulated TNF-α and IFNγ cytokine production. Taken together, this study suggests that Be-induces non-sensitized Glu69+ DCs maturation, and that p38MAPK signaling is important in the Be-stimulated DCs activation as well as subsequent T cell proliferation and cytokine production in BeS and CBD. In total, the MAPK pathway may serve as a potential therapeutic target for human granulomatous lung diseases.

Induction of protection against leishmaniasis in susceptible BALB/c mice using simple DOTAP cationic nanoliposomes containing soluble Leishmania antigen (SLA)

A suitable adjuvant and delivery system are needed to develop an effective vaccine against leishmaniasis. To induce a Th1 type of response and protection in BALB/c mice against Leishmania major infection, 1,2-dioleoyl-3-trimethylammonium-propane (DOTAP) nanoliposomes bearing an intrinsic adjuvanticity, were used as an antigen delivery system and immunoadjuvant for soluble Leishmania antigens (SLA). DOTAP liposomes containing different concentrations of SLA were prepared by using lipid film method followed by sonication. The prepared vesicles showed a diameter of about 100nm, a positive zeta potential and approximately 70% encapsulation efficiency of SLA. BALB/c mice were immunized subcutaneously (SC), three times in a 3-week interval with different concentrations of liposomal SLA (12.5, 25, and 50μg of SLA/50μl/mice), free SLA and as well as free liposome. The group of mice received 50μg of SLA in DOTAP-nanoliposomes showed a significantly (p<0.001) smaller footpad swelling and the lowest spleen and footpad parasite burden after the challenge. This group also showed the highest IFN-γ production compared to the other groups, lower IL-4 level and higher IgG2a antibody titer. Taken together, the results indicated that simple DOTAP nanoliposome containing 1μg/μl SLA are appropriate delivery systems to induce a Th1 type of immune response and protection against L. major infection in BALB/c mice.

Immunotoxicity of 3 chemical forms of beryllium following inhalation exposure

The toxicity of 3 chemical forms of beryllium (Be) was compared in this study. A total of 160 mice equally divided into 4 groups were exposed by inhalation (nose only) for 3 consecutive weeks, 5 d/week, 6 h/d. One group was used as control, while the 3 others were exposed to fine particles of Be metal, Be oxide (BeO), or Be aluminum (BeAl). Except for the controls, the target level of exposure was 250 μg/m(3). In all, 35 mice/group were sacrificed 1 week postexposure and another 5 mice 3 weeks postexposure. The BeO group showed the highest lung Be concentration with higher interleukin 12 (IL-12) and interferon-γ (IFN-γ) levels, while the Be group produced the most severe lung inflammation and higher tumor necrosis factor-α (TNF-α) and CD4+ T cells levels. Data suggested that Be and BeO apparently produced more pulmonary toxicity than BeAl. However, this conclusion is not definitive, because of different confounding factors such as particle sizes, specific surface area, and solubility.

Beryllium alters lipopolysaccharide-mediated intracellular phosphorylation and cytokine release in human peripheral blood mononuclear cells

Beryllium exposure in susceptible individuals leads to the development of chronic beryllium disease, a lung disorder marked by release of inflammatory cytokine and granuloma formation. We have previously reported that beryllium induces an immune response even in blood mononuclear cells from healthy individuals. In this study, we investigate the effects of beryllium on lipopolysaccharide-mediated cytokine release in blood mononuclear and dendritic cells from healthy individuals. We found that in vitro treatment of beryllium sulfate inhibits the secretion of lipopolysaccharide-mediated interleukin 10, while the release of interleukin 1beta is enhanced. In addition, not all lipopolysaccharide-mediated responses are altered, as interleukin 6 release in unaffected upon beryllium treatment. Beryllium sulfate-treated cells show altered phosphotyrosine levels upon lipopolysaccharide stimulation. Significantly, beryllium inhibits the phosphorylation of signal transducer and activator of transducer 3, induced by lipopolysaccharide. Finally, inhibitors of phosphoinositide-3 kinase mimic the effects of beryllium in inhibition of interleukin 10 release, while they have no effect on interleukin 1beta secretion. This study strongly suggests that prior exposures to beryllium could alter host immune responses to bacterial infections in healthy individuals, by altering intracellular signaling.

Bérylliose pulmonaire chronique (2e partie)

INTRODUCTION

Chronic beryllium disease (CBD) is an occupational lung disease caused by the inhalation of beryllium dust, fumes or metallic salts.

CURRENT DATA

Beryllium affects the lungs via particles deposited in the pulmonary alveoli. These are ingested by alveolar macrophages which act as antigen presenting cells to CD4+ T lymphocytes. T lymphocytes proliferate in response to beryllium antigens and combined with macrophages produce numerous epithelioid granulomas with the release of inflammatory cytokines (IFNgamma, IL-2, TNFalpha and IL6) and growth factors. Beryllium induces macrophage apoptosis which reduces its clearance from the lung which in turn contributes to the host's continual re-exposure and thus a chronic granulomatous disorder. Pulmonary granulomatous inflammation is the primary manifestation of CBD, but the disease occasionally involves other organs such as the liver, spleen, lymph nodes and bone marrow. The clinical, radiological, and histopathological features of CBD can be difficult to distinguish from sarcoidosis. The Beryllium lymphocyte proliferation test (BeLPT) demonstrates a beryllium specific immune response, confirms the diagnosis of CBD, and excludes sarcoidosis.

CONCLUSIONS AND PERSPECTIVES

CBD provides a human model of pulmonary granulomatous disease produced by an occupational exposure, occurring more frequently in those with a genetic pre-disposition. It can be differentiated from sarcoidosis by specific immunological testing.

Flow cytometric test for beryllium sensitivity

BACKGROUND

Chronic beryllium disease (CBD) is an occupational granulomatous disorder characterized by hypersensitivity to beryllium, mediated by CD4+ T lymphocytes, and predominantly affects the lungs. In this disorder, lymphocyte proliferative responses to beryllium, measured by 3H thymidine incorporation, are used for diagnosis of CBD, for screening asymptomatic workers or former workers to detect unrecognized disease, and for surveillance as a bioassay to detect abnormal exposures. Problems with test variability and the use of radioactivity have recently led to the search for alternative methods.

METHODS

We applied a 5,6-carboxyfluorescein diacetate succinimidyl ester flow cytometric technique for measurement of mitogen- and antigen-induced T-lymphocyte proliferation to a group of beryllium-exposed sensitized individuals and beryllium-unexposed controls.

RESULTS

We detected mitogen and antigen proliferative responses in CD3+, CD4+, and CD8+ subpopulations. Phytohemagglutinin and Candida stimulated CD4+ and CD8+ T-cell responses, but beryllium appeared to stimulate only CD3+/CD4+ responses.

CONCLUSIONS

This technique may provide a sensitive, nonradioactive alternative to the traditional proliferation tests that measure beryllium sensitivity. It offers the added specificity of enabling phenotypic description of the responding cell type and may prove to be easier to standardize for clinical use.

Chronic beryllium disease: a model interaction between innate and acquired immunity

Beryllium (Be) is a lightweight and durable metal useful to a variety of manufacturing processes. With the use of Be in industrial settings, a number of health effects were noted including acute pneumonitis, sensitization to Be, interstitial lung disease and dermatological disease. Interstitial mononuclear cell inflammation and granuloma formation are the primary processes that occur in the lungs of Be-exposed workers, resulting in chronic beryllium disease (CBD). Recent studies have begun to describe the role of Be in the pathogenesis of CBD. These studies reveal that the host's response to Be involves components of the innate immune system or inflammatory responses. Inflammatory responses to Be can establish a state of acquired, Be antigen-specific, cell-mediated immunity. Despite triggering both the innate and acquired immune responses, Be is not eliminated from the host. Rather, it establishes pathways leading to chronic granulomatous inflammation. We will examine recent studies describing the host's cellular and molecular responses to Be, responses that promote granuloma formation.