Quaternary ammoniums activate human dendritic cells and induce a specific T-cell response in vitro

BACKGROUND

In many countries, neuro-muscular blocking agents (NMBAs) are the first cause of perioperative anaphylaxis. Epidemiological studies identified pholcodine, a quaternary ammonium-containing opiate as one of the sensitization sources. However, NMBA anaphylaxis exists in countries where pholcodine was unavailable, prompting the hypothesis of other sensitizing molecules, most likely quaternary ammonium compounds (QACs). Indeed, QACs are commonly used as disinfectants, antiseptics, preservatives, and detergents. Occupational exposure to QACs has been reported as a risk factor for NMBA anaphylaxis, but little is known about the sensitization mechanism and the capacity of these molecules to elicit an immune response. We aimed to establish the immunogenicity of QACs representative of the main existing chemical structures.

METHODS

We measured the sensitization potential of seven QACs (two polyquaterniums, three alkyl-ammoniums and two aromatic ammoniums) by using two standard dendritic cells (DCs) models (THP-1 cell line and monocyte derived-dendritic cells). The allergenicity of the sensitizing compounds was further tested in heterologous and autologous T-cell-DC co-culture models.

RESULTS

Amongst the seven molecules tested, four could modulate activation markers on DCs, and thus can be classified as chemical sensitizers (polyquaterniums-7 and -10, ethylhexadecyldimethylammonium and benzethonium). This activation was accompanied by the secretion of pro-inflammatory and maturation cytokines. Furthermore, activation by polyquaternium-7 could induce T-cell proliferation in heterologous and autologous coculture models, demonstrating that this molecule can induce a specific CD4+ T cell response.

CONCLUSIONS

We provide evidence at the cellular level that some QACs can elicit an immune response, which could be in line with the hypothesis of these molecules' role in NMBA sensitization.

Antibodies internalization mechanisms by dendritic cells and their role in therapeutic antibody immunogenicity

Internalization and processing by antigen-presenting cells such as dendritic cells (DCs) are critical steps for initiating a T-cell response to therapeutic antibodies. Consequences are the production of neutralizing antidrug antibodies altering the clinical response, the presence of immune complexes, and, in some rare cases, hypersensitivity reactions. In recent years, significant progress has been made in the knowledge of cellular uptake mechanisms of antibodies in DCs. The uptake of antibodies could be directly related to their immunogenicity by regulating the quantity of materials entering the DCs in relation to antibody structure. Here, we summarize the latest insights into cellular uptake mechanisms and pathways in DCs. We highlight the approaches to study endocytosis, the impact of endocytosis routes on T-cell response, and discuss the link between how DCs internalize therapeutic antibodies and the potential mechanisms that could give rise to immunogenicity. Understanding these processes could help in developing assays to evaluate the immunogenicity potential of biotherapeutics.

Infliximab aggregates produced in severe and mild elevated temperature stress conditions induce an extended specific CD4 T-cell response

Aggregation has been widely described as a factor contributing to therapeutic antibody immunogenicity. Although production of high-affinity anti-drug antibodies depends on the activation of CD4 T lymphocytes, little is known about the T-cell response induced by antibody aggregates, especially for aggregates produced in mild conditions resulting from minor handling errors of vials. Large insoluble infliximab (IFX) aggregates produced in severe elevated temperature stress conditions have been previously shown to induce human monocyte-derived dendritic cell (moDC) maturation. We here showed that large IFX aggregates recruit in vitro a significantly higher number of CD4 T-cells compared to native IFX. Moreover, a larger array of T-cell epitopes encompassing the entire variable regions was evidenced compared to the native antibody. We then compared the responses of moDCs to different types of aggregates generated by submitting IFX to mild conditions of various times of incubation at an elevated temperature. Decreasing stress duration reduced aggregate size and quantity, and subsequently altered moDC activation. Of importance, IFX aggregates generated in mild conditions and not altering moDC phenotype generated an in vitro T-cell response with a higher frequency of CD4 T cells compared to native IFX. Moreover, cross-reactivity studies of aggregate-specific T cells showed that some T cells could recognize both native and aggregated IFX, while others responded only to IFX aggregates. Taken together, our results suggest that aggregation of antibodies in mild elevated temperature stress conditions is sufficient to alter moDC phenotype in a dose-dependent manner and to increase T-cell response.

Human dendritic cell maturation induced by amorphous silica nanoparticles is Syk-dependent and triggered by lipid raft aggregation

BACKGROUND

Synthetic amorphous silica nanoparticles (SAS-NPs) are widely employed in pharmaceutics, cosmetics, food and concretes. Workers and the general population are exposed daily via diverse routes of exposure. SAS-NPs are generally recognized as safe (GRAS) by the Food and Drug Administration, but because of their nanoscale size and extensive uses, a better assessment of their immunotoxicity is required. In the presence of immune "danger signals", dendritic cells (DCs) undergo a maturation process resulting in their migration to regional lymph nodes where they activate naive T-cells. We have previously shown that fumed silica pyrogenic SAS-NPs promote the two first steps of the adaptative immune response by triggering DC maturation and T-lymphocyte response, suggesting that SAS-NPs could behave as immune "danger signals". The present work aims to identify the mechanism and the signalling pathways involved in DC phenotype modifications provoked by pyrogenic SAS-NPs. As a pivotal intracellular signalling molecule whose phosphorylation is associated with DC maturation, we hypothesized that Spleen tyrosine kinase (Syk) may play a central role in SAS-NPs-induced DC response.

RESULTS

In human monocyte-derived dendritic cells (moDCs) exposed to SAS-NPs, Syk inhibition prevented the induction of CD83 and CD86 marker expression. A significant decrease in T-cell proliferation and IFN-γ, IL-17F and IL-9 production was found in an allogeneic moDC:T-cell co-culture model. These results suggested that the activation of Syk was necessary for optimal co-stimulation of T-cells. Moreover, Syk phosphorylation, observed 30 min after SAS-NP exposure, occurred upstream of the c-Jun N-terminal kinase (JNK) Mitogen-activated protein kinases (MAPK) and was elicited by the Src family of protein tyrosine kinases. Our results also showed for the first time that SAS-NPs provoked aggregation of lipid rafts in moDCs and that MβCD-mediated raft destabilisation altered Syk activation.

CONCLUSIONS

We showed that SAS-NPs could act as an immune danger signal in DCs through a Syk-dependent pathway. Our findings revealed an original mechanism whereby the interaction of SAS-NPs with DC membranes promoted aggregation of lipid rafts, leading to a Src kinase-initiated activation loop triggering Syk activation and functional DC maturation.

The spleen tyrosine kinase (SYK): A crucial therapeutic target for diverse liver diseases

Spleen tyrosine kinase (SYK) is an enigmatic protein tyrosine kinase, and involved in signal transduction related with lots of cellular processes. It's highly expressed in the cells of hematopoietic origin and acts as an important therapeutic target in the treatment of autoimmune diseases and allergic disorders. In recent years, more and more evidences indicate that SYK is expressed in non-hematopoietic cells and effectively regulates various non-immune biological responses as well. In this review, we mainly summary the role of SYK in different liver diseases. Robust SYK expression has been discovered in hepatocytes, hepatic stellate cells, as well as Kupffer cells, which participates in the regulation of numerous signal transduction in various liver diseases (e.g. hepatitis, liver fibrosis and hepatocellular carcinoma). In addition, the blockage of SYK activity using small molecule modulators is considered as a significant therapeutic strategy against liver diseases, and both hepatic SYK and non-hepatic SYK could become highly promising therapeutic targets. Totally, even though some critical points about the significance of SYK in liver diseases treatment still need further elaboration, more reliable biotechnical or pharmacological therapy modes will be established based on the better understanding of the relationship between SYK and liver diseases.

Shaping of Monocyte-Derived Dendritic Cell Development and Function by Environmental Factors in Rheumatoid Arthritis

Dendritic cells (DC) are heterogeneous cell populations essential for both inducing immunity and maintaining immune tolerance. Chronic inflammatory contexts, such as found in rheumatoid arthritis (RA), severely affect the distribution and the function of DC, contributing to defective tolerance and fueling inflammation. In RA, the synovial fluid of patients is enriched by a subset of DC that derive from monocytes (Mo-DC), which promote deleterious Th17 responses. The characterization of environmental factors in the joint that impact on the development and the fate of human Mo-DC is therefore of great importance in RA. When monocytes leave the blood and infiltrate inflamed synovial tissues, the process of differentiation into Mo-DC can be influenced by interactions with soluble factors such as cytokines, local acidosis and dysregulated synoviocytes. Other molecular factors, such as the citrullination process, can also enhance osteoclast differentiation from Mo-DC, favoring bone damages in RA. Conversely, biotherapies used to control inflammation in RA, modulate also the process of monocyte differentiation into DC. The identification of the environmental mediators that control the differentiation of Mo-DC, as well as the underlying molecular signaling pathways, could constitute a major breakthrough for the development of new therapies in RA.

HP-β-CD for the formulation of IgG and Ig-based biotherapeutics

The main challenge to develop HCF for IgG and Ig-based therapeutics is to achieve essential solubility, viscosity and stability of these molecules in order to maintain product quality and meet regulatory requirement during manufacturing, production, storage, shipment and administration processes. The commonly used and FDA approved excipients for IgG and Ig -based therapeutics may no longer fulfil the challenge of HCF development for these molecules to certain extent, especially for some complex Ig-based platforms. 2-Hydroxypropyl beta-cyclodextrin (HP-β-CD) is one of the promising excipients applied recently for HCF development of IgG and Ig-based therapeutics although it has been used for formulation of small synthesized chemical drugs for more than thirty years. This review describes essential aspects about application of HP-β-CD as excipient in pharmaceutical formulation, including physico-chemical properties of HP-β-CD, supply chain, regulatory, patent landscape, marketed drugs with HP-β-CD, analytics and analytical challenges, stability and control strategies, and safety concerns. It also provides an overview of different studies, and outcomes thereof, regarding formulation development for IgGs and Ig-based molecules in liquid and solid (lyophilized) dosage forms with HP-β-CD. The review specifically highlights the challenges for formulation manufacturing of IgG and Ig-based therapeutics with HP-β-CD and identifies areas for future work in pharmaceutical and formulation development.

Immunological Evaluation In Vitro of Nanoparticulate Impurities Isolated From Pharmaceutical-Grade Sucrose

Sucrose is a commonly used stabilizing excipient in protein formulations. However, recent studies have indicated the presence of nanoparticulate impurities (NPIs) in the size range of 100-200 nm in pharmaceutical-grade sucrose. Furthermore, isolated NPIs have been shown to induce protein aggregation when added to monoclonal antibody formulations. Moreover, nanoparticles are popular vaccine delivery systems used to increase the immunogenicity of antigens. Therefore, we hypothesized that NPIs may have immunostimulatory properties. In this study, we evaluated the immunomodulatory effects of NPIs in presence and absence of trastuzumab in vitro with monocyte-derived dendritic cells (moDCs). Exposure of trastuzumab, the model IgG used in this study, to NPIs led to an increase in concentration of proteinaceous particles in the sub-micron range. When added to moDCs, the NPIs alone or in presence of trastuzumab did not affect cell viability or cytotoxicity. Moreover, no significant effect on the expression of surface markers, and cytokine and chemokine production was observed. Our findings showed, surprisingly, no evidence of any immunomodulatory activity of NPIs. As this study was limited to a single IgG formulation and to in vitro immunological read-outs, further work is required to fully understand the immunogenic potential of NPIs.