Untersuchungen zum DEC-205-vermittelten Antigentransfer in Dendritischen Zellen als Werkzeug zur Induktion adaptiver Immunität gegen das Hepatitis C Virus

HCV infection represents a serious worldwide public healthcare problem. Despite extensive investigations no effective vaccine does yet exist. DCs play a pivotal role in mediating immunity to pathogens and represent an exceptionally attractive target for vaccination. Therefore, the aim of this thesis was to test different in vivo DC targeting strategies with respect to their applicability for inducing antiviral immunity in the liver and thus to provide the basis for the development of a DC-based HCV vaccine. In the first part of this thesis two distinct in vivo DC targeting strategies, utilizing either the endocytosis receptor DEC-205 or the TLR2/6 heterodimer, were compared using the model antigen OVA. For this, mice were immunized with aDEC-205/OVA or the TLR2/6 agonist BPPcysMPEG, which was either separately delivered with the entire protein antigen or directly linked to the immunodominant MHC-I and MHC-II peptide epitopes (BPPcysOVAMPEG). Immunization with aDEC-205/OVA was found to be exceptionally potent in inducing Th1 cells and CTLs, which were capable of efficiently clearing virus-infected hepatocytes, whereas immunization with OVA and BPPcysMPEG resulted in a Th2 dominated CD4+ T cell response and failed to induce CTLs capable of killing virus-infected liver cells. In contrast, vaccination with BPPcysOVAMPEG was as efficient as aDEC-205/OVA treatment in inducing antiviral immunity in the liver. However, since vaccination against only a limited number of antigenic determinants is of great disadvantage with respect to the highly mutating virus HCV, targeting DEC-205 on DCs in vivo was identified to be superior to the TLR2/6. In the second part of the thesis, the analyses were extended towards the design of DEC-205-based HCV vaccine. First immunization trials in mice with both aDEC-205/NS3 and aDEC-205/Core were found to induce HCV-specific immune responses, thus providing a promising starting point for the future development of a DEC-205-based HCV vaccine.HCV-Infektionen stellen weltweit ein gesundheitspolitisches Problem dar. Trotz umfangreicher wissenschaftlicher Studien ist bis heute kein geeignetes Vakzin verfügbar. DCs sind von zentraler Bedeutung für das Auslösen Pathogen-spezifischer Immunität und stellen ein attraktives Target für die Entwicklung von Impfstoffen dar. Ziel dieser Arbeit war es, verschiedene DC Targeting Strategien hinsichtlich ihrer Eignung für die Induktion antiviraler Immunität in der Leber zu testen und somit die Grundlage für die Weiterentwicklung eines DC-basierten HCV Vakzins zu schaffen. Im ersten Teil der Arbeit wurden zwei verschiedene Methoden des in vivo DC Targetings unter Verwendung des Modellantigens OVA charakterisiert, wobei entweder der Endozytoserezeptor DEC-205 oder der TLR2/6 als molekulare Targets dienten. Hierfür wurden Mäuse mit aDEC-205/OVA oder dem TLR2/6 Agonisten BPPcysMPEG, entweder als Mischung aus löslichem OVA-Protein oder als ein Konjugat mit den immundominanten MHC-I/MHC-II OVA-Peptiden (BPPcysOVAMPEG), immunisiert. Es zeigte sich, dass die Immunisierung mit aDEC-205/OVA zu einer starken Induktion von Th1-Zellen und CTLs führte, wobei diese in der Lage waren virusinfizierte Hepatozyten zu eliminieren. Im Gegensatz dazu löste die Vakzinierung mit OVA-Protein und BPPcysMPEG eine Th2 dominierte CD4+ T-Zellantwort aus. Zudem wurde keine CTL-Antwort induziert und folglich erfolgte kein CTL-vermitteltes Abtöten virusinfizierter Leberzellen. Neben aDEC-205/OVA führte die Vakzinierung mit BPPcysOVAMPEG ebenfalls zur Induktion antiviraler Immunität in der Leber. Vor dem Hintergrund, dass ein Peptidimpfstoff gegen das stark mutierende HCV deutliche Nachteile aufweist, wurde im zweiten Teil der Arbeit der DEC-205-basierte Ansatz für die Entwicklung eines HCV Vakzins favorisiert. Die Ergebnisse der Immunisierungsversuche mit aDEC-205/NS3 und aDEC-205/Core weisen auf eine vielversprechende Basis für die zukünftige Weiterentwicklung eines DEC-205-basierten HCV Vakzins hin

IκBNS-deficiency protects mice from fatal Listeria monocytogenes infection by blunting pro-inflammatory signature in Ly6Chigh monocytes and preventing exaggerated innate immune responses

IκB proteins regulate the inhibition and activation of NF-κB transcription factor complexes. While classical IκB proteins keep NF-κB complexes inactive in the cytoplasm, atypical IκB proteins act on activated NF-κB complexes located in the nucleus. Most of the knowledge regarding the function of IκB proteins has been collected in vitro, while far less is known regarding their impact on activation and regulation of immune responses during in vivo infections. Combining in vivo Listeria monocytogenes (Lm) infection with comparative ex vivo transcriptional profiling of the hepatic response to the pathogen we observed that in contrast to wild type mice that mounted a robust inflammatory response, IκBNS-deficiency was generally associated with a transcriptional repression of innate immune responses. Whole tissue transcriptomics revealed a pronounced IκBNS-dependent reduction of myeloid cell-associated transcripts in the liver together with an exceptionally high Nfkbid promoter activity uncovered in Ly6Chigh inflammatory monocytes prompted us to further characterize the specific contribution of IκBNS in the inflammatory response of monocytes to the infectious agent. Indeed, Ly6Chigh monocytes primed during Lm infection in the absence of IκBNS displayed a blunted response compared to wild type-derived Ly6Chigh monocytes as evidenced by the reduced early expression of hallmark transcripts of monocyte-driven inflammation such as Il6, Nos2 and Il1β. Strikingly, altered monocyte activation in IκBNS-deficient mice was associated with an exceptional resistance against Lm infection and protection was associated with a strong reduction in immunopathology in Lm target organs. Of note, mice lacking IκBNS exclusively in myeloid cells failed to resist Lm infection, indicating that the observed effect was not monocyte intrinsic but monocyte extrinsic. While serum cytokine-profiling did not discover obvious differences between wild type and IκBNS-/- mice for most of the analyzed mediators, IL-10 was virtually undetectable in IκBNS-deficient mice, both in the steady state and following Lm infection. Together, we show here a crucial role for IκBNS during Lm infection with IκBNS-deficient mice showing an overall blunted pro-inflammatory immune response attributed to a reduced pro-inflammatory signature in Ly6Chigh monocytes. Reduced immunopathology and complete protection of mice against an otherwise fatal Lm infection identified IκBNS as molecular driver of inflammation in listeriosis

The STING activator c-di-AMP exerts superior adjuvant properties than the formulation poly(I:C)/CpG after subcutaneous vaccination with soluble protein antigen or DEC-205-mediated antigen targeting to dendritic cells.

Vaccination is the most efficient strategy to protect from infectious diseases and the induction of a protective immune response not only depends on the nature of the antigen, but is also influenced by the vaccination strategy and the co-administration of adjuvants. Therefore, the precise monitoring of adjuvant candidates and their immune modulatory properties is a crucial step in vaccine development. Here, one central aspect is the induction of appropriate humoral and cellular effector mechanisms. In our study we performed a direct comparison of two promising candidates in adjuvant development, the STING activator bis-(3,5)-cyclic dimeric adenosine monophosphate (c-di-AMP) and the Toll-like receptor ligand formulation poly(I:C)/CpG. These were evaluated in C57BL/6 mice using the model antigen ovalbumin (OVA) in subcutaneous vaccination with soluble protein as well as in a dendritic cell (DC) targeting approach (αDEC-OVA). Strikingly, c-di-AMP as compared to poly(I:C)/CpG resulted in significantly higher antigen-specific IgG antibody levels when used in immunization with soluble OVA as well as in antigen targeting to DC. In vaccination with soluble OVA, c-di-AMP induced a significantly stronger CTL, Th1 and IFNγ-producing CD8+ memory T cell response than poly(I:C)/CpG. The response was CTL and Th1 cell dominated, a profile shared by both adjuvants. In the context of targeting OVA to DC, c-di-AMP induced significantly increased Th1 and Th2 cell responses as compared to poly(I:C)/CpG. Interestingly, the Th1 response dominated the overall T cell response only when c-di-AMP was used, indicating a distinct modulatory property of c-di-AMP when the DC targeting immunization approach was exploited. Taken together, we describe superior properties of c-di-AMP as compared to poly(I:C)/CpG in subcutaneous vaccination with soluble antigen as well as antigen targeting to DC. This indicates exceptionally effective adjuvant properties for c-di-AMP and provides compelling evidence of its potential for further adjuvant development, especially also when using DC targeting approaches

Respiratory Bordetella bronchiseptica Carriage is Associated with Broad Phenotypic Alterations of Peripheral CD4+CD25+ T Cells and Differentially Affects Immune Responses to Secondary Non-Infectious and Infectious Stimuli in Mice

The respiratory tract is constantly exposed to the environment and displays a favorable niche for colonizing microorganisms. However, the effects of respiratory bacterial carriage on the immune system and its implications for secondary responses remain largely unclear. We have employed respiratory carriage with Bordetella bronchiseptica as the underlying model to comprehensively address effects on subsequent immune responses. Carriage was associated with the stimulation of Bordetella-specific CD4+, CD8+, and CD4+CD25+Foxp3+ T cell responses, and broad transcriptional activation was observed in CD4+CD25+ T cells. Importantly, transfer of leukocytes from carriers to acutely B. bronchiseptica infected mice, resulted in a significantly increased bacterial burden in the recipient’s upper respiratory tract. In contrast, we found that respiratory B. bronchiseptica carriage resulted in a significant benefit for the host in systemic infection with Listeria monocytogenes. Adaptive responses to vaccination and influenza A virus infection, were unaffected by B. bronchiseptica carriage. These data showed that there were significant immune modulatory processes triggered by B. bronchiseptica carriage, that differentially affect subsequent immune responses. Therefore, our results demonstrated the complexity of immune regulation induced by respiratory bacterial carriage, which can be beneficial or detrimental to the host, depending on the pathogen and the considered compartment

Chemical Conjugation of a Purified DEC-205-Directed Antibody with Full-Length Protein for Targeting Mouse Dendritic Cells In Vitro and In Vivo.

Targeted antigen delivery to cross-presenting dendritic cells (DC) in vivo efficiently induces T effector cell responses and displays a valuable approach in vaccine design. Antigen is delivered to DC via antibodies specific for endocytosis receptors such as DEC-205 that induce uptake, processing, and MHC class I- and II-presentation. Efficient and reliable conjugation of the desired antigen to a suitable antibody is a critical step in DC targeting and among other factors depends on the format of the antigen. Chemical conjugation of full-length protein to purified antibodies is one possible strategy. In the past, we have successfully established cross-linking of the model antigen ovalbumin (OVA) and a DEC-205-specific IgG2a antibody (αDEC-205) for in vivo DC targeting studies in mice. The first step of the protocol is the purification of the antibody from the supernatant of the NLDC (non-lymphoid dendritic cells)-145 hybridoma by affinity chromatography. The purified antibody is activated for chemical conjugation by sulfo-SMCC (sulfosuccinimidyl 4-[N-maleimidomethyl] cyclohexane-1-carboxylate) while at the same time the sulfhydryl-groups of the OVA protein are exposed through incubation with TCEP-HCl (tris (2-carboxyethyl) phosphine hydrochloride). Excess TCEP-HCl and sulfo-SMCC are removed and the antigen is mixed with the activated antibody for overnight coupling. The resulting αDEC-205/OVA conjugate is concentrated and freed from unbound OVA. Successful conjugation of OVA to αDEC-205 is verified by western blot analysis and enzyme-linked immunosorbent assay (ELISA). We have successfully used chemically crosslinked αDEC-205/OVA to induce cytotoxic T cell responses in the liver and to compare different adjuvants for their potential in inducing humoral and cellular immunity following in vivo targeting of DEC-205+ DC. Beyond that, such chemically coupled antibody/antigen conjugates offer valuable tools for the efficient induction of vaccine responses to tumor antigens and have been proven to be superior to classical immunization approaches regarding the prevention and therapy of various types of tumors

Influenza A virus infection predisposes hosts to secondary infection with different Streptococcus pneumoniae serotypes with similar outcome but serotype-specific manifestation.

Influenza A virus (IAV) and Streptococcus pneumoniae (S. pn.) are major causes of respiratory tract infections, particularly during co-infection. The synergism between these two pathogens is characterized by a complex network of dysregulated immune responses, some of which last until recovery post IAV infection. Despite the high serotype-diversity of S. pn. and the serotype-replacement observed since the introduction of conjugate vaccines, little is known about pneumococcal strain-dependency in the enhanced susceptibility to severe secondary S. pn. infection following IAV infection. Thus we studied how pre-infection with IAV alters host susceptibility to different S. pn. strains with varying degrees of invasiveness using a highly invasive serotype 4, an invasive serotype 7F and a carrier serotype 19F strain. A murine model of pneumococcal co-infection during the acute phase of IAV infection showed a significantly increased degree of pneumonia and mortality for all tested pneumococcal strains at otherwise sublethal doses. The incidence and kinetics of systemic dissemination however remained bacterial strain-dependent. Furthermore we observed strain-specific alterations in the pulmonary levels of alveolar macrophages, neutrophils and inflammatory mediators ultimately affecting immunopathology. During the recovery phase following IAV infection, bacterial growth in the lungs and systemic dissemination were enhanced in a strain-dependent manner. Altogether, this study shows that acute IAV infection predisposes the host to lethal S. pn. infection irrespective of the pneumococcal serotype, while the long lasting synergism between IAV and S. pn. is bacterial strain-dependent. These results hold implications for developing tailored therapeutic treatment regimens for dual infections during future IAV outbreaks

Targeted antigen delivery to dendritic cells elicits robust antiviral T cell-mediated immunity in the liver.

Hepatotropic viruses such as hepatitis C virus cause life-threatening chronic liver infections in millions of people worldwide. Targeted in vivo antigen-delivery to cross-presenting dendritic cells (DCs) has proven to be extraordinarily efficient in stimulating antigen-specific T cell responses. To determine whether this approach would as well be suitable to induce local antiviral effector T cells in the liver we compared different vaccine formulations based on either the targeting of DEC-205 or TLR2/6 on cross-presenting DCs or formulations not involving in vivo DC targeting. As read-outs we used in vivo hepatotropic adenovirus challenge, histology and automated multidimensional fluorescence microscopy (MELC). We show that targeted in vivo antigen delivery to cross-presenting DCs is highly effective in inducing antiviral CTLs capable of eliminating virus-infected hepatocytes, while control vaccine formulation not involving DC targeting failed to induce immunity against hepatotropic virus. Moreover, we observed distinct patterns of CD8+ T cell interaction with virus-infected and apoptotic hepatocytes in the two DC-targeting groups suggesting that the different vaccine formulations may stimulate distinct types of effector functions. Our findings represent an important step toward the future development of vaccines against hepatotropic viruses and the treatment of patients with hepatic virus infection after liver transplantation to avoid reinfection

Evidence for three genetic loci involved in both anorexia nervosa risk and variation of body mass index

The maintenance of normal body weight is disrupted in patients with anorexia nervosa (AN) for prolonged periods of time. Prior to the onset of AN, premorbid body mass index (BMI) spans the entire range from underweight to obese. After recovery, patients have reduced rates of overweight and obesity. As such, loci involved in body weight regulation may also be relevant for AN and vice versa. Our primary analysis comprised a cross-trait analysis of the 1000 single-nucleotide polymorphisms (SNPs) with the lowest P-values in a genome-wide association meta-analysis (GWAMA) of AN (GCAN) for evidence of association in the largest published GWAMA for BMI (GIANT). Subsequently we performed sex-stratified analyses for these 1000 SNPs. Functional ex vivo studies on four genes ensued. Lastly, a look-up of GWAMA-derived BMI-related loci was performed in the AN GWAMA. We detected significant associations (P-values <5 × 10-5, Bonferroni-corrected P<0.05) for nine SNP alleles at three independent loci. Interestingly, all AN susceptibility alleles were consistently associated with increased BMI. None of the genes (chr. 10: CTBP2, chr. 19: CCNE1, chr. 2: CARF and NBEAL1; the latter is a region with high linkage disequilibrium) nearest to these SNPs has previously been associated with AN or obesity. Sex-stratified analyses revealed that the strongest BMI signal originated predominantly from females (chr. 10 rs1561589; Poverall: 2.47 × 10-06/Pfemales: 3.45 × 10-07/Pmales: 0.043). Functional ex vivo studies in mice revealed reduced hypothalamic expression of Ctbp2 and Nbeal1 after fasting. Hypothalamic expression of Ctbp2 was increased in diet-induced obese (DIO) mice as compared with age-matched lean controls. We observed no evidence for associations for the look-up of BMI-related loci in the AN GWAMA. A cross-trait analysis of AN and BMI loci revealed variants at three chromosomal loci with potential joint impact. The chromosome 10 locus is particularly promising given that the association with obesity was primarily driven by females. In addition, the detected altered hypothalamic expression patterns of Ctbp2 and Nbeal1 as a result of fasting and DIO implicate these genes in weight regulation

Evidence for three genetic loci involved in both anorexia nervosa risk and variation of body mass index

The maintenance of normal body weight is disrupted in patients with anorexia nervosa (AN) for prolonged periods of time. Prior to the onset of AN, premorbid body mass index (BMI) spans the entire range from underweight to obese. After recovery, patients have reduced rates of overweight and obesity. As such, loci involved in body weight regulation may also be relevant for AN and vice versa. Our primary analysis comprised a cross-trait analysis of the 1000 single-nucleotide polymorphisms (SNPs) with the lowest P-values in a genome-wide association meta-analysis (GWAMA) of AN (GCAN) for evidence of association in the largest published GWAMA for BMI (GIANT). Subsequently we performed sex-stratified analyses for these 1000 SNPs. Functional ex vivo studies on four genes ensued. Lastly, a look-up of GWAMA-derived BMI-related loci was performed in the AN GWAMA. We detected significant associations (P-values &lt;5 × 10-5, Bonferroni-corrected P&lt;0.05) for nine SNP alleles at three independent loci. Interestingly, all AN susceptibility alleles were consistently associated with increased BMI. None of the genes (chr. 10: CTBP2, chr. 19: CCNE1, chr. 2: CARF and NBEAL1; the latter is a region with high linkage disequilibrium) nearest to these SNPs has previously been associated with AN or obesity. Sex-stratified analyses revealed that the strongest BMI signal originated predominantly from females (chr. 10 rs1561589; Poverall: 2.47 × 10-06/Pfemales: 3.45 × 10-07/Pmales: 0.043). Functional ex vivo studies in mice revealed reduced hypothalamic expression of Ctbp2 and Nbeal1 after fasting. Hypothalamic expression of Ctbp2 was increased in diet-induced obese (DIO) mice as compared with age-matched lean controls. We observed no evidence for associations for the look-up of BMI-related loci in the AN GWAMA. A cross-trait analysis of AN and BMI loci revealed variants at three chromosomal loci with potential joint impact. The chromosome 10 locus is particularly promising given that the association with obesity was primarily driven by females. In addition, the detected altered hypothalamic expression patterns of Ctbp2 and Nbeal1 as a result of fasting and DIO implicate these genes in weight regulation

Evidence for three genetic loci involved in both anorexia nervosa risk and variation of body mass index

The maintenance of normal body weight is disrupted in patients with anorexia nervosa (AN) for prolonged periods of time. Prior to the onset of AN, premorbid body mass index (BMI) spans the entire range from underweight to obese. After recovery, patients have reduced rates of overweight and obesity. As such, loci involved in body weight regulation may also be relevant for AN and vice versa. Our primary analysis comprised a cross-trait analysis of the 1000 single-nucleotide polymorphisms (SNPs) with the lowest P-values in a genome-wide association meta-analysis (GWAMA) of AN (GCAN) for evidence of association in the largest published GWAMA for BMI (GIANT). Subsequently we performed sex-stratified analyses for these 1000 SNPs. Functional ex vivo studies on four genes ensued. Lastly, a look-up of GWAMA-derived BMI-related loci was performed in the AN GWAMA. We detected significant associations (P-values <5 × 10-5, Bonferroni-corrected P<0.05) for nine SNP alleles at three independent loci. Interestingly, all AN susceptibility alleles were consistently associated with increased BMI. None of the genes (chr. 10: CTBP2, chr. 19: CCNE1, chr. 2: CARF and NBEAL1; the latter is a region with high linkage disequilibrium) nearest to these SNPs has previously been associated with AN or obesity. Sex-stratified analyses revealed that the strongest BMI signal originated predominantly from females (chr. 10 rs1561589; Poverall: 2.47 × 10-06/Pfemales: 3.45 × 10-07/Pmales: 0.043). Functional ex vivo studies in mice revealed reduced hypothalamic expression of Ctbp2 and Nbeal1 after fasting. Hypothalamic expression of Ctbp2 was increased in diet-induced obese (DIO) mice as compared with age-matched lean controls. We observed no evidence for associations for the look-up of BMI-related loci in the AN GWAMA. A cross-trait analysis of AN and BMI loci revealed variants at three chromosomal loci with potential joint impact. The chromosome 10 locus is particularly promising given that the association with obesity was primarily driven by females. In addition, the detected altered hypothalamic expression patterns of Ctbp2 and Nbeal1 as a result of fasting and DIO implicate these genes in weight regulation