Torben Knuschke

The use of calcium phosphate nanoparticles encapsulating Toll-like receptor ligands and the antigen hemagglutinin to induce dendritic cell maturation and T cell activation

Dendritic cells (DCs) are potent antigen-presenting cells that possess the ability to stimulate naïve T cells. Antigen presentation by mature (activated) DCs is a prerequisite for the stimulation of antigen-specific T cells, whereas antigen presentation by immature DCs results in the generation of specific tolerance. Our aim was to develop calcium phosphate nanoparticles which can serve as carriers of immunoactive oligonucleotides into dendritic cells for their activation. We analyzed size, surface charge, and morphology of calcium phosphate nanoparticles loaded with the TLR ligands CpG and poly(I:C) and also with the antigen hemagglutinin (HA) by scanning electron microscopy, dynamic light scattering, Brownian motion analysis and ultracentrifugation. The uptake of fluorescence-labeled nanoparticles into dendritic cells was illustrated by confocal laser scanning microscopy. Immunostimulatory effects of these nanoparticles on DCs were studied, i.e., cytokine production and activation of the cells in terms of upregulation of surface molecules. We show that functionalized calcium phosphate nanoparticles are capable to induce both innate and adaptive immunity by activation of DCs.

Mechanism of the uptake of cationic and anionic calcium phosphate nanoparticles by cells

The uptake of calcium phosphate nanoparticles (diameter 120nm) with different charge by HeLa cells was studied by flow cytometry. The amount of uptaken nanoparticles increased with increasing concentration of nanoparticles in the cell culture medium. Several inhibitors of endocytosis and macropinocytosis were applied to elucidate the uptake mechanism of nanoparticles into HeLa cells: wortmannin, LY294002, nocodazole, chlorpromazine and nystatin. Wortmannin and LY294002 strongly reduced the uptake of anionic nanoparticles, which indicates macropinocytosis as uptake mechanism. For cationic nanoparticles, the uptake was reduced to a lesser extent, indicating a different uptake mechanism. The localization of nanoparticles inside the cells was investigated by conjugating them with the pH-sensitive dye SNARF-1. The nanoparticles were localized in lysosomes after 3h of incubation.

Cell targeting by antibody-functionalized calcium phosphate nanoparticles

Calcium phosphate nanoparticles were coated with a shell of silica and covalently functionalized by silanization, either with thiol or with amino groups. This permits the covalent attachment of molecules like dyes or antibodies. Between the calcium phosphate surface and the outer silica shell, biomolecules like nucleic acids (DNA or siRNA) can be incorporated as cargo. This leads to cell-specific carriers of biomolecules into cells, e.g. for transfection, gene silencing or cell activation. The cellular uptake of antibody-coated calcium phosphate nanoparticles was demonstrated on two cell lines: HeLa (epithelial cell line) and MG-63 (osteoblast-like cell line). Furthermore, the functionalization of calcium phosphate nanoparticles with a dendritic cell-specific antibody (CD11c) led to a cell-specific targeting as shown with primary murine splenocytes. Thus, the successful coating of calcium phosphate nanoparticles with cell-specific antibodies makes them suitable for many clinical applications.

Immunization with Biodegradable Nanoparticles Efficiently Induces Cellular Immunity and Protects against Influenza Virus Infection

The ability of vaccines to induce T cell responses is crucial for preventing diseases caused by viruses or bacteria. Nanoparticles (NPs) are considered an efficient tool for inducing potent immune responses. In this study, we describe a novel vaccination approach with biodegradable calcium phosphate (CaP) NPs that serve as carrier of immunoactive TLR9 ligand (CpG) combined with a viral Ag from the influenza A virus hemagglutinin. Functionalized CaP NPs were efficiently taken up by dendritic cells in vivo and elicited a potent T cell–mediated immune response in immunized mice with high numbers of IFN-γ–producing CD4+ and CD8+ effector T cells. Most importantly, both i.p. and intranasal immunization with these NPs offered protection in a mouse model of influenza virus infection. This study demonstrates the great potential of CaP NPs as a novel vaccination tool that offers substantial flexibility for several infection models.

Quantitative determination of the composition of multi-shell calcium phosphate-oligonucleotide nanoparticles and their application for the activation of dendritic cells.

Biodegradable calcium phosphate nanoparticles as carriers for the immunoactive toll-like receptor ligands CpG and polyinosinic-polycytidylic acid for the activation of dendritic cells (DC) combined with the viral antigen hemagglutinin (HA) were prepared. A purification method based on ultracentrifugation and ultrasonication was developed to separate the nanoparticles from dissolved biomolecules. The number of biomolecules, i.e., oligonucleotides and peptide, incorporated into the nanoparticles was quantitatively determined by UV-spectroscopy, using fluorescent derivatives of the biomolecules. The immunostimulatory effects of purified calcium phosphate nanoparticles on DC were studied, i.e., cytokine production and activation of the cells in terms of the upregulation of surface molecules. Purified calcium phosphate nanoparticles, i.e., without dissolved biomolecules, are capable of inducing adaptive immunity by activation of DC. Immunostimulatory effects of purified calcium phosphate nanoparticles on DC were demonstrated by increased expression of co-stimulatory molecules and MHC II and by cytokine secretion. In addition, DC treated with purified functionalized calcium phosphate nanoparticles induced an antigen-specific T-cell response in vitro.

CD8+ T-Cell Response Promotes Evolution of Hepatitis C Virus Nonstructural Proteins

BACKGROUND & AIMS Hepatitis C virus (HCV) acquires mutations that allow it to escape the CD8+ T-cell response, although the extent to which this process contributes to viral evolution at the population level is not clear. We studied viral adaptation using data from a large outbreak of HCV genotype 1b infection that occurred among women immunized with contaminated immunoglobulin from 1977 to 1978. METHODS The HCV nonstructural protein coding regions NS3-NS5B were sequenced from 78 patients, and mutations were mapped according to their location inside or outside previously described CD8+ T-cell epitopes. A statistical approach was developed to identify sites/regions under reproducible selection pressure associated with HLA class I. RESULTS The frequency of nonsynonymous mutations was significantly higher inside previously described CD8+ T-cell epitopes than outside-particularly in NS3/4A and NS5B. We identified new regions that are under selection pressure, indicating that not all CD8+ T-cell epitopes have been identified; 6 new epitopes that interact with CD8+ T cells were identified and confirmed in vitro. In some CD8+ T-cell epitopes mutations were reproducibly identified in patients that shared the relevant HLA allele, indicating immune pressure at the population level. There was statistical support for selection of mutations in 18 individual epitopes. Interestingly, 14 of these were restricted by HLA-B allele. CONCLUSIONS HLA class I-associated selection pressure on the nonstructural proteins and here predominantly on NS3/4A and NS5B promotes evolution of HCV. HLA-B alleles have a dominant effect in this selection process. Adaptation of HCV to the CD8+ T-cell response at the population level creates challenges for vaccine design.

Prophylactic and therapeutic vaccination with a nanoparticle-based peptide vaccine induces efficient protective immunity during acute and chronic retroviral infection.

UNLABELLED Retroviral infections e.g. HIV still represent a unique burden in the field of vaccine research. A common challenge in vaccine design is to find formulations that create appropriate immune responses to protect against and/or control the given pathogen. Nanoparticles have been considered to be ideal vaccination vehicles that mimic invading pathogens. In this study, we present biodegradable calcium phosphate (CaP) nanoparticles, functionalized with CpG and retroviral T cell epitopes of Friend virus (FV) as excellent vaccine delivery system. CaP nanoparticles strongly increased antigen delivery to antigen-presenting cells to elicit a highly efficient T cell-mediated immune response against retroviral FV infection. Moreover, single-shot immunization of chronically FV-infected mice with functionalized CaP nanoparticles efficiently reactivated effector T cells which led to a significant decrease in viral loads. Thus, our findings clearly indicate that a nanoparticle-based peptide immunization is a promising approach to improve antiretroviral vaccination. FROM THE CLINICAL EDITOR In this study, biodegradable calcium phosphate nanoparticles were used as a vaccine delivery system after functionalization with CpG and Friend virus-derived T-cell epitopes. This vaccination strategy resulted in increased T-cell mediated immune response even in chronically infected mice, providing a promising approach to the development of clinically useful antiretroviral vaccination strategies.

Generation and function of immunosuppressive human and murine CD8+ T cells by transforming growth factor-β and retinoic acid.

The intestinal immune system is constantly challenged by foreign antigens and commensal bacteria. Therefore, proper control of the intestinal microenvironment is required. One important arm of this regulatory network consists of regulatory T cells. In contrast to CD4+ Foxp3+ regulatory T cells, which have been well characterized, immunomodulatory CD8+ T cells that express Foxp3 are less well defined in terms of their generation and function. Failures of these regulatory mechanisms contribute to the development of inflammatory bowel disease. In this study we demonstrate that the frequency of CD8+ Foxp3+ T cells is reduced in the peripheral blood of patients with ulcerative colitis. As these cells might play a currently underestimated role in the maintenance of intestinal homeostasis, we have investigated human and murine CD8+ Foxp3+ T cells generated by stimulating naive CD8+ T cells in the presence of transforming growth factor‐β and retinoic acid, mediators that are abundantly produced in the intestinal mucosa. These CD8+ Foxp3+ fully competent regulatory T cells show strong expression of regulatory molecules CD25, Gpr83 and CTLA‐4 and exhibit cell–cell contact‐dependent immunosuppressive activity in vitro. Our study illustrates a previously unappreciated critical role of CD8+ Foxp3+ T cells in controlling potentially dangerous T cells and in the maintenance of intestinal homeostasis.

Virus-Induced Type I Interferon Deteriorates Control of Systemic Pseudomonas Aeruginosa Infection.

Background: Type I interferon (IFN-I) predisposes to bacterial superinfections, an important problem during viral infection or treatment with interferon-alpha (IFN-α). IFN-I-induced neutropenia is one reason for the impaired bacterial control; however there is evidence that more frequent bacterial infections during IFN-α-treatment occur independently of neutropenia. Methods: We analyzed in a mouse model, whether Pseudomonas aeruginosa control is influenced by co-infection with the lymphocytic choriomeningitis virus (LCMV). Bacterial titers, numbers of neutrophils and the gene-expression of liver-lysozyme-2 were determined during a 24 hours systemic infection with P. aeruginosa in wild-type and Ifnar-/- mice under the influence of LCMV or poly(I:C). Results: Virus-induced IFN-I impaired the control of Pseudomonas aeruginosa. This was associated with neutropenia and loss of lysozyme-2-expression in the liver, which had captured P. aeruginosa. A lower release of IFN-I by poly(I:C)-injection also impaired the bacterial control in the liver and reduced the expression of liver-lysozyme-2. Low concentration of IFN-I after infection with a virulent strain of P. aeruginosa alone impaired the bacterial control and reduced lysozyme-2-expression in the liver as well. Conclusion: We found that during systemic infection with P. aeruginosa Kupffer cells quickly controlled the bacteria in cooperation with neutrophils. Upon LCMV-infection this cooperation was disturbed.

Combination of nanoparticle-based therapeutic vaccination and transient ablation of regulatory T cells enhances anti-viral immunity during chronic retroviral infection.

BackgroundRegulatory T cells (Tregs) have been shown to limit anti-viral immunity during chronic retroviral infection and to restrict vaccine-induced T cell responses. The objective of the study was to assess whether a combinational therapy of nanoparticle-based therapeutic vaccination and concomitant transient ablation of Tregs augments anti-viral immunity and improves virus control in chronically retrovirus-infected mice. Therefore, chronically Friend retrovirus (FV)-infected mice were immunized with calcium phosphate (CaP) nanoparticles functionalized with TLR9 ligand CpG and CD8+ or CD4+ T cell epitope peptides (GagL85–93 or Env gp70123–141) of FV. In addition, Tregs were ablated during the immunization process. Reactivation of CD4+ and CD8+ effector T cells was analysed and the viral loads were determined.ResultsTherapeutic vaccination of chronically FV-infected mice with functionalized CaP nanoparticles transiently reactivated cytotoxic CD8+ T cells and significantly reduced the viral loads. Transient ablation of Tregs during nanoparticle-based therapeutic vaccination strongly enhanced anti-viral immunity and further decreased viral burden.ConclusionOur data illustrate a crucial role for CD4+ Foxp3+ Tregs in the suppression of anti-viral T cell responses during therapeutic vaccination against chronic retroviral infection. Thus, the combination of transient Treg ablation and therapeutic nanoparticle-based vaccination confers robust and sustained anti-viral immunity.