Particle size and surface charge affect particle uptake by human dendritic cells in an in vitro model (original) (raw)
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Journal of Controlled Release, 2001
This work focuses on microparticles as potential antigen delivery systems to target professional antigen-presenting cells. Surface modified polystyrene microparticles were administered to human-derived macrophages (MFs) and dendritic cells (DCs) in vitro to evaluate the phagocytosis activity of each cell type. To discriminate between internalised particles and those closely attached to the outside of the cells, particle internalisation was verified by confocal laser scanning microscopy. Especially positively charged particles tend to stick to the outer cell membrane and may lead to false positive results when measured by conventional microscopy. In contrast, fluorescence microscopy in combination with an extracellular fluorescence quenching agent (trypan blue) allows the unequivocal assessment of particle uptake for screening purposes. For this assay, the fluorescent label needs to be in direct contact to the quenching agent and cannot be localised inside the particle core. Different types of microparticles varying in size, surface-material and zeta potential resulted in vast differences regarding their uptake by MFs and DCs as well as the maturation of DCs. Negatively-charged carboxylated and bovine serum albumin-coated particles were phagocytosed by MFs to a relatively small extent. Interestingly, phagocytosis of these particles was still significantly lower in DCs while positively charged poly-L-lysine (PLL) coated particles induced high phagocytosis activity in both cell types. By comparing our results with literature data, we conclude that phagocytosis activity of DCs and MFs largely depends on particle size and surface charge and is also influenced by the character of bulk and coating material. PLL can be directed to DCs and MFs with comparable efficiency and, in addition, induce maturation of DCs.
Designing polymeric particles for antigen delivery
Chemical Society Reviews, 2011
By targeting dendritic cells, polymeric carriers in the nano to lower micron range constitute very interesting tools for antigen delivery. In this critical review, we review how new immunological insights can be exploited to design new carriers allowing one to tune immune responses and to further increase vaccine potency (137 references).
Endocytosis of micro- and nanosized particles in vitro by human dendritic cells
Biochemistry (Moscow) Supplement Series A: Membrane and Cell Biology, 2009
The ability of human dendritic cells (DC) to uptake synthetic micro-and nanosized particles was assessed by flow cytometry and fluorescent microscopy. DCs were differentiated in vitro from blood monocytes in the presence of recombinant cytokines. Further maturation of DC in culture after the addition of maturation factors resulted in the increased expression of HLA-DR and co-stimulatory molecules CD80, CD83, CD86, in comparison with immature DC. Active internalization of Fluoresbrite-YG fluorescent microbeads (0.2 μ m) was noted for immature but not mature DCs. The decrease of endocytic activity after DC maturation correlated with the reduced expression of CD209, the surface membrane receptor participating in phagocytosis. Unlike microparticles, the uptake of nanoscale Quantum dots-655 did not depend on the stage of DC maturation and probably was mediated by a different endocytosis mechanism.
Proceedings of the National Academy of Sciences, 2005
Activating the immune system to trigger a specific response is a major challenge in vaccine development. In particular, activating sufficient cytotoxic T lymphocyte-mediated cellular immunity, which is crucial for the treatment of many diseases including cancer and AIDS, has proven to be especially challenging. In this study, antigens were encapsulated in acid-degradable polymeric particle carriers to cascade cytotoxic T lymphocyte activation. To target dendritic cells, the most potent antigen-presenting cells, the particle carriers, were further conjugated with monoclonal antibodies. A series of ex vivo and in vivo studies have shown increased receptor-mediated uptake of antibody-conjugated particles by dendritic cells as well as migration of particle-carrying dendritic cells to lymph nodes and stimulation of naïve T cells leading to enhanced cellular immune response as confirmed by specific cell lysis and IFN-γ secretion.
Polyanhydride microparticles enhance dendritic cell antigen presentation and activation
Acta biomaterialia, 2011
a b s t r a c t 25 The present study was designed to evaluate the adjuvant activity of polyanhydride microparticles 26 prepared in the absence of additional stabilizers, excipients or immune modulators. Microparticles com-27 posed of varying ratios of either 1,6-bis(p-carboxyphenoxy)hexane (CPH) and sebacic acid or 1,8-bis(p-28 carboxyphenoxy)-3,6-dioxaoctane and CPH were added to in vitro cultures of bone marrow-derived 29 dendritic cells (DCs). Microparticles were efficiently and rapidly phagocytosed by DCs in the absence 30 of opsonization and without centrifugation or agitation. Within 2 h, internalized particles were rapidly 31 localized to an acidic, phagolysosomal compartment. By 48 h, only a minor reduction in microparticle 32 size was observed in the phagolysosomal compartment, indicating minimal particle erosion consistent 33 with being localized within an intracellular microenvironment favoring particle stability. Polyanhydride 34 microparticles increased DC surface expression of major histocompatability complex class II, the co-stim-35 ulatory molecules CD86 and CD40, and the C-type lectin CIRE (murine DC-SIGN; CD209). In addition, 36 microparticle stimulation of DCs also enhanced secretion of the cytokines IL-12p40 and IL-6, a phenom-37 enon found to be dependent on polymer chemistry. DCs cultured with polyanhydride microparticles and 38 ovalbumin induced polymer chemistry-dependent antigen-specific proliferation of both CD4 + OT-II and 39 CD8 + OT-I T cells. These data indicate that polyanhydride particles can be tailored to take advantage of 40 the potential plasticity of the immune response, resulting in the ability to induce immune protection 41 against many types of pathogens. 42 43 44 45 65 presentation; and (iii) induce co-stimulatory signals on APCs nec-66 essary for activation of naive T cells [5,6]. Currently, the common 67 adjuvants employed in human vaccines are aluminum-based salts 68 (e.g. alum) and often require multiple doses to achieve protective 69 immunity. The resulting immune response is primarily antibody-70 mediated, with limited engagement of an effector T cell population 71 [7]. The use of aluminum-based salts is often associated with the 72 induction of adverse reactions at the site of injection. However, 73 we and others have extensively studied polyanhydrides, a novel 74 class of biodegradable polymers, as protein carriers and/or vaccine 75 delivery systems with inherent adjuvant properties [8-20]. 76 Currently approved by the US Food and Drug Administration 1742-7061/$ -see front matter Ó
Journal of Drug Targeting, 2003
Dendritic cells (DC) need to be stimulated before they can function to initiate immune responses. This study investigates whether microparticles loaded with antibodies specific for selected receptors expressed by DC can induce stimulation of these cells. Plain microparticles were compared with microparticles which were surface-loaded with specific antibodies for human CD40, Fcg, avb3 and avb5 integrin receptors. The antibodies were either physically adsorbed or covalently linked to the microparticle surface. Anti-CD40 antibody and human IgG immobilised on the surface of microparticles induced enhanced DC maturation and activation as expressed by CD83 and CD86 upregulation. IL-12 secretion was induced at a detectable but relatively low level. Both anti-integrin antibodies (anti-avb3 and anti-avb5) induced comparable and considerable maturation of DC, but only anti-avb3 antibody induced significant activation of DC, whereas anti-avb5 did not. The stimulatory effects were most pronounced by employing microparticles with covalently linked antibodies, but were also observed to a minor extent when the antibodies were physically adsorbed to polystyrene and biodegradable poly(lactide-co-glycolide) microparticles. Engineering of microparticles by surface conjugation of specific ligands to stimulate DC may increase the effectiveness of microparticulate vaccine delivery systems.
Vaccines that facilitate antigen entry into dendritic cells
Immunology and Cell Biology, 2004
Although vaccines have been highly successful in preventing and treating many infectious diseases (including smallpox, polio and diphtheria) diseases prevalent in the developing world such as malaria and HIV, that suppress the host immune system, require new, multiple strategies that will be defined by our growing understanding of specific immune activation. The definition of adjuvants, previously thought of as any substance that enhanced the immunogenicity of antigen, could now include soluble mediators and antigenic carriers that interact with surface molecules present on DC (e.g. LPS, Flt3L, heat shock protein) particulate antigens which are taken up by mechanisms available to APC but not other cell types (e.g. immunostimulatory complexes, latex, polystyrene particles) and viral/ bacterial vectors that infect antigen presenting cells (e.g. vaccinia, lentivirus, adenovirus). These approaches, summarized herein, have shown potential in vaccinating against disease in animal models, and in some cases in humans. Of these, particle-antigen conjugates provide rapid formulation of the vaccine, easy storage and wide application, with both carrier and adjuvant functions that activate DC. Combined vaccines of the future could use adjuvants such as virus-like particles and particles targeted towards a predominant cellular type or immune response, with target cell activation enhanced by growth factors or maturation signals prior to, or during immunization. Collectively, these new additions to adjuvant technology provide opportunities for more specific immune regulation than previously available.