Novel roles of CpG oligodeoxynucleotides as a leader for the sampling and presentation of CpG-tagged antigen by dendritic cells

Application of phosphorylcholine derivative as mucosal adjuvant enhancing mucosal immune responses in the upper respiratory tract

OBJECTIVE

A phosphorylcholine (PC)-derivative with high binding ability (PCDB) was intranasally administered to mice with ovalbumin (OVA), and immune responses were investigated to determine whether PCDB has antigenicity and adjuvanticity.

METHODS

BALB/c mice were intranasally immunized with PCDB coupled with OVA, unbound PCDB plus OVA, cholera toxin (CT) plus OVA, OVA alone, and PCDB alone. Then, the production of OVA- and PC-specific antibodies in external secretions and serum, and the secretion of cytokines such as IL-4 and IFN-γ from splenic mononuclear cells by stimulation with PCDB and OVA were examined. Furthermore, the secretion of IL-12p40 from CD11c+ cells following stimulation with PCDB was observed to clarify the adjuvant effect of PCDB through TLR4.

RESULTS

Intranasal immunization with PCDB plus OVA increased OVA- and PC-specific IgA in external secretions and OVA- and PC-specific antibodies in the serum. The analysis of IgG subclasses specific to OVA and PC showed a higher production of IgG1 than IgG2, and the secretion of both IL-4 and IFN-γ was enhanced. However, IL-12p40 secretion from CD11c+ cells was increased and OVA-specific IgE production was not promoted by PCDB stimulation.

CONCLUSION

Intranasal administration of the protein antigen with PCDB enhanced immune responses specific to the mixed antigen and PC. Although PCDB acted to bias the immune response toward the Th2-type, antigen-specific IgE production did not increase. These findings suggest that PCDB has the potential to be a mucosal vaccine with both adjuvanticity and antigenicity without causing side effects due to type I allergy.

Chemically Modified Bacterial Sacculi as a Vaccine Microparticle Scaffold

Vaccine scaffolds and carrier proteins increase the immunogenicity of subunit vaccines. Here, we developed, characterized, and demonstrated the efficacy of a novel microparticle vaccine scaffold comprised of bacterial peptidoglycan (PGN), isolated as an entire sacculi. The PGN microparticles contain bio-orthogonal chemical handles allowing for site-specific attachment of immunogens. We first evaluated the purification, integrity, and immunogenicity of PGN microparticles derived from a variety of bacterial species. We then optimized PGN microparticle modification conditions; Staphylococcus aureus PGN microparticles containing azido-d-alanine yielded robust conjugation to immunogens. We then demonstrated that this vaccine scaffold elicits comparable immunostimulation to the conventional carrier protein, keyhole limpet hemocyanin (KLH). We further modified the S. aureus PGN microparticle to contain the SARS-CoV-2 receptor-binding domain (RBD)—this conjugate vaccine elicited neutralizing antibody titers comparable to those elicited by the KLH-conjugated RBD. Collectively, these findings suggest that chemically modified bacterial PGN microparticles are a conjugatable and biodegradable microparticle scaffold capable of eliciting a robust immune response toward an antigen of interest.

Chemically Tuning the Antigen Release Kinetics from Spherical Nucleic Acids Maximizes Immune Stimulation

Cancer vaccine structure is emerging as an important design factor that offers tunable parameters to enhance the targeted immune response. We report the impact of altering the antigen release rate from spherical nucleic acid (SNA) vaccines-nanoparticles with a liposomal core and surface-anchored adjuvant DNA-on immune stimulation. Peptide antigens were incorporated into SNAs using either a nonreducible linker or one of a series of reduction-triggered traceless linkers that release the native peptide at rates controlled by their substitution pattern. Compared with a nonreducible linkage, the traceless attachment of antigens resulted in lower EC50 of T cell proliferation in vitro and greater dendritic cell (DC) activation and higher T cell killing ability in vivo. Traceless linker fragmentation rates affected the rates of antigen presentation by DCs and were correlated with the in vitro potencies of SNAs. Antigen release was correlated with the ex vivo -log(EC50), and more rapid antigen release resulted in an order of magnitude improvement in the EC50 and earlier and greater antigen presentation over the same time-period. In vivo, increasing the rate of antigen release resulted in higher T cell activation and target killing. These findings provide fundamental insights into and underscore the importance of vaccine structure.

CpG Oligonucleotides as Vaccine Adjuvants

CpG Oligonucleotides (ODN) are immunomodulatory synthetic oligonucleotides specifically designed to stimulate Toll-like receptor 9. TLR9 is expressed on human plasmacytoid dendritic cells and B cells and triggers an innate immune response characterized by the production of Th1 and pro-inflammatory cytokines. This chapter reviews recent progress in understanding the mechanism of action of CpG ODN and provides an overview of human clinical trial results using CpG ODN to improve vaccines for the prevention/treatment of cancer, allergy, and infectious disease.

Development of an Enzyme-Mediated, Site-Specific Method to Conjugate Toll-Like Receptor 2 Agonists onto Protein Antigens: Toward a Broadly Protective, Four Component, Group A Streptococcal Self-Adjuvanting Lipoprotein-Fusion Combination Vaccine

Subunit vaccines composed of protein antigens covalently attached to Toll-like receptor (TLR) agonists elicit superior immune responses compared to mixtures of antigens and TLR agonists. Among different conjugation approaches, enzyme-mediated ligation is one of the few that provides an opportunity for the generation of homogeneous, molecularly defined products in which protein antigens are maintained with native structures, which is most critical to elicit protective immune responses upon vaccination. Four highly conserved protein antigens from Group A Streptococcus (GAS) have the potential to be safe and efficacious vaccine candidates. After a TLR2 agonist fibroblast-stimulating lipopeptide-1 (FSL-1) was successfully attached onto each antigen using sortase A and techniques for their purification were developed, a combination vaccine containing interleukin 8 (IL-8) protease (Streptococcus pyogenes cell envelope proteinase [SpyCEP]), Group A Streptococcal C5a peptidase (SCPA), anchorless virulence factor arginine deiminase (ADI), and trigger factor (TF)-TLR2 conjugates was produced. This combination was assessed for immunity in mice and compared with mixtures of the four antigens with FSL-1 or alum. High titer antigen-specific IgG antibodies were detected from all vaccine groups, with antibodies elicited from FSL-1 conjugates around 10-fold higher compared to the FSL-1 mixture group. Furthermore, the FSL-1 conjugates afforded a more balanced T_H1/T_H2 immune response than the alum-adjuvanted group, suggesting that this combination vaccine represents a promising candidate for the prevention of GAS diseases. Thus, we established a conjugation platform that allows for the production of defined, site-specific antigen-adjuvant conjugates, which maintain the native three-dimensional structure of antigens and can be potentially applied to a variety of protein antigens.

Expression Level of TLR9, but not Hypomethylation, Is Correlated With SLE Disease Activity

This study aims to investigate the associations of hypomethylation and over expression of the TLR9 gene with systemic lupus erythematosus (SLE). Fifteen SLE patients who were diagnosed and not treated, were selected as cases, and 32 healthy subjects were enrolled as controls. DNA and total RNA of peripheral blood mononuclear cells (PBMCs) were extracted. The methylation status of the promoter region CpG motifs of the TLR9 gene was quantitatively measured using bisulfite sequencing PCR, and the mRNA expression of the TLR9 gene was determined using real-time fluorescent quantitative PCR. The methylation level of the 10 TLR9 CpG motifs of gene did not show difference between cases and controls (P>0.05). By contrast, we observed an abnormal increase of TLT9 mRNA expression in patients (P=9.379×10(-8)), which was significantly correlated with SLEDAI (Systemic Lupus Erythematosus Disease Activity Index) (P=9.018×10(-7)). The change of TLR9 gene expression may play an important role in the pathogenesis of SLE.

CD82 controls CpG-dependent TLR9 signaling

The tetraspanin CD82 is a potent suppressor of tumor metastasis and regulates several processes including signal transduction, cell adhesion, motility, and aggregation. However, the mechanisms by which CD82 participates in innate immunity are unknown. We report that CD82 is a key regulator of TLR9 trafficking and signaling. TLR9 recognizes unmethylated cytosine-phosphate-guanine (CpG) motifs present in viral, bacterial, and fungal DNA. We demonstrate that TLR9 and CD82 associate in macrophages, which occurs in the endoplasmic reticulum (ER) and post-ER. Moreover, CD82 is essential for TLR9-dependent myddosome formation in response to CpG stimulation. Finally, CD82 modulates TLR9-dependent NF-κB nuclear translocation, which is critical for inflammatory cytokine production. To our knowledge, this is the first time a tetraspanin has been implicated as a key regulator of TLR signaling. Collectively, our study demonstrates that CD82 is a specific regulator of TLR9 signaling, which may be critical in cancer immunotherapy approaches and coordinating the innate immune response to pathogens.-Khan, N. S., Lukason, D. P., Feliu, M., Ward, R. A., Lord, A. K., Reedy, J. L., Ramirez-Ortiz, Z. G., Tam, J. M., Kasperkovitz, P. V., Negoro, P. E., Vyas, T. D., Xu, S., Brinkmann, M. M., Acharaya, M., Artavanis-Tsakonas, K., Frickel, E.-M., Becker, C. E., Dagher, Z., Kim, Y.-M., Latz, E., Ploegh, H. L., Mansour, M. K., Miranti, C. K., Levitz, S. M., Vyas, J. M. CD82 controls CpG-dependent TLR9 signaling.

The Content of CpG-DNA in Antigen-CpG Conjugate Vaccines Determines Their Cross-Presentation Activity

Cross-presentation, the process that facilitates display of exogenous antigens on MHC-I molecules, is a crucial step in the cascade of CD8 T cell activation. Potentiation of cross-presentation therefore represents an essential design criterion for development of subunit vaccines that target the induction of CD8 T cell immunity. Covalent conjugation of CpG-DNA to antigenic proteins has shown the potential to promote cross-presentation and has attracted great interest as a promising approach for vaccine development. However, heterogeneous product mixtures that result from typical conjugation schemes precluded identification of active conjugate species and impeded optimization of cross-presentation activity. In this report, we explore the effect of molecular composition of antigen-CpG conjugates on their cross-presentation activity using model Ovalbumin (OVA)-CpG conjugates. We developed a method to generate antigen-CpG conjugates with defined molecular compositions and leveraged this method to produce a series of OVA-CpG conjugates with one, two, and three CpG molecules linked to OVA. We observed that conjugates containing one CpG per OVA enhanced cross-presentation by 4-fold compared to native OVA, while conjugates with higher contents of CpG provided no cross-presentation enhancement. These differences are likely due to enhanced aggregation propensity observed for conjugates that carry more than one CpG per OVA. Our findings suggest that tuning molecular composition of antigen-CpG conjugates to maintain physical stability may be essential for achieving potent cross-presentation activity. Our method to generate defined conjugates could facilitate such molecular tuning and may be useful for continued development of antigen-CpG vaccines.

TLR9-based immunotherapy for the treatment of allergic diseases

Toll-like receptors (TLRs), a family of pattern recognition receptors expressed on many cell types of innate immunity, recognize the pathogen-associated molecular patterns of microbes. The hygiene hypothesis suggests that a reduced microbial exposure in early childhood increases the susceptibility to allergic diseases due to deviation in development of the immune system. TLRs are key roles in the right and healthy direction of adaptive immunity with the induction of T-helper 2 toward Th1 immune responses and regulatory T cells. TLR ligand CpG-ODN-based immunomodulation is independent of allergen and it mainly affects innate immune system. While, CpG-oligodeoxynucleotide-based vaccination is allergen specific and induces adaptive immune system. The use of agonists of TLR9 in two distinct strategies of immunotherapy, immunomodulation and vaccination, could be presented as the curative method for the treatment of allergic diseases.

Biotechnology approaches to produce potent, self-adjuvanting antigen-adjuvant fusion protein subunit vaccines

Traditional vaccination approaches (e.g. live attenuated or killed microorganisms) are among the most effective means to prevent the spread of infectious diseases. These approaches, nevertheless, have failed to yield successful vaccines against many important pathogens. To overcome this problem, methods have been developed to identify microbial components, against which protective immune responses can be elicited. Subunit antigens identified by these approaches enable the production of defined vaccines, with improved safety profiles. However, they are generally poorly immunogenic, necessitating their administration with potent immunostimulatory adjuvants. Since few safe and effective adjuvants are currently used in vaccines approved for human use, with those available displaying poor potency, or an inability to stimulate the types of immune responses required for vaccines against specific diseases (e.g. cytotoxic lymphocytes (CTLs) to treat cancers), the development of new vaccines will be aided by the availability of characterized platforms of new adjuvants, improving our capacity to rationally select adjuvants for different applications. One such approach, involves the addition of microbial components (pathogen-associated molecular patterns; PAMPs), that can stimulate strong immune responses, into subunit vaccine formulations. The conjugation of PAMPs to subunit antigens provides a means to greatly increase vaccine potency, by targeting immunostimulation and antigen to the same antigen presenting cell. Thus, methods that enable the efficient, and inexpensive production of antigen-adjuvant fusions represent an exciting mean to improve immunity towards subunit antigens. Herein we review four protein-based adjuvants (flagellin, bacterial lipoproteins, the extra domain A of fibronectin (EDA), and heat shock proteins (Hsps)), which can be genetically fused to antigens to enable recombinant production of antigen-adjuvant fusion proteins, with a focus on their mechanisms of action, structural or sequence requirements for activity, sequence modifications to enhance their activity or simplify production, adverse effects, and examples of vaccines in preclinical or human clinical trials.

IL4 from T Follicular Helper Cells Downregulates Antitumor Immunity

Immune cells constitute a large fraction of the tumor microenvironment and modulate tumor progression. Clinical data indicate that chronic inflammation is present at tumor sites and that IL4 in particular is upregulated. Here, we demonstrate that T follicular helper (Tfh) cells arise in tumor-draining lymph nodes where they produce an abundance of IL4. Deletion of IL4-expressing Tfh cells improves antitumor immunity, delays tumor growth, and reduces the generation of immunosuppressive myeloid cells in the lymph nodes. These findings suggest that IL4 from Tfh cells affects antitumor immunity and constitutes an attractive therapeutic target to reduce immunosuppression in the tumor microenvironment, and thus enhance the efficacy of cancer immunotherapy. Cancer Immunol Res; 5(1); 61-71. ©2016 AACR.

A new TLR2 agonist promotes cross-presentation by mouse and human antigen presenting cells

Cross-presentation is the process by which professional APCs load peptides from an extracellularly derived protein onto class I MHC molecules to trigger a CD8(+) T cell response. The ability to enhance this process is therefore relevant for the development of antitumor and antiviral vaccines. We investigated a new TLR2-based adjuvant, Small Molecule Immune Potentiator (SMIP) 2.1, for its ability to stimulate cross-presentation. Using OVA as model antigen, we demonstrated that a SMIP2.1-adjuvanted vaccine formulation induced a greater CD8(+) T cell response, in terms of proliferation, cytokine production and cytolytic activity, than a non-adjuvanted vaccine. Moreover, using an OVA-expressing tumor model, we showed that the CTLs induced by the SMIP2.1 formulated vaccine inhibits tumor growth in vivo. Using a BCR transgenic mouse model we found that B cells could cross-present the OVA antigen when stimulated with SMIP2.1. We also used a flow cytometry assay to detect activation of human CD8(+) T cells isolated from human PBMCs of cytomegalovirus-seropositive donors. Stimulation with SMIP2.1 increased the capacity of human APCs, pulsed in vitro with the pp65 CMV protein, to activate CMV-specific CD8(+) T cells. Therefore, vaccination with an exogenous antigen formulated with SMIP2.1 is a successful strategy for the induction of a cytotoxic T cell response along with antibody production.

Virus-like nanostructures for tuning immune response

Synthetic vaccines utilize viral signatures to trigger immune responses. Although the immune responses raised against the biochemical signatures of viruses are well characterized, the mechanism of how they affect immune response in the context of physical signatures is not well studied. In this work, we investigated the ability of zero- and one-dimensional self-assembled peptide nanostructures carrying unmethylated CpG motifs (signature of viral DNA) for tuning immune response. These nanostructures represent the two most common viral shapes, spheres and rods. The nanofibrous structures were found to direct immune response towards Th1 phenotype, which is responsible for acting against intracellular pathogens such as viruses, to a greater extent than nanospheres and CpG ODN alone. In addition, nanofibers exhibited enhanced uptake into dendritic cells compared to nanospheres or the ODN itself. The chemical stability of the ODN against nuclease-mediated degradation was also observed to be enhanced when complexed with the peptide nanostructures. In vivo studies showed that nanofibers promoted antigen-specific IgG production over 10-fold better than CpG ODN alone. To the best of our knowledge, this is the first report showing the modulation of the nature of an immune response through the shape of the carrier system.

Experimental Immunization Based on Plasmodium Antigens Isolated by Antibody Affinity

Vaccines blocking malaria parasites in the blood-stage diminish mortality and morbidity caused by the disease. Here, we isolated antigens from total parasite proteins by antibody affinity chromatography to test an immunization against lethal malaria infection in a murine model. We used the sera of malaria self-resistant ICR mice to lethal Plasmodium yoelii yoelii 17XL for purification of their IgGs which were subsequently employed to isolate blood-stage parasite antigens that were inoculated to immunize BALB/c mice. The presence of specific antibodies in vaccinated mice serum was studied by immunoblot analysis at different days after vaccination and showed an intensive immune response to a wide range of antigens with molecular weight ranging between 22 and 250 kDa. The humoral response allowed delay of the infection after the inoculation to high lethal doses of P. yoelii yoelii 17XL resulting in a partial protection against malaria disease, although final survival was managed in a low proportion of challenged mice. This approach shows the potential to prevent malaria disease with a set of antigens isolated from blood-stage parasites.

TLR-9 agonist immunostimulatory sequence adjuvants linked to cancer antigens

The primary goal of cancer vaccines is to elicit tumor-specific cytotoxic T lymphocytes (CTL) capable of eradicating established tumors and preventing/eradicating their metastatic spread. CpG oligonucleotides (CpG ODN) activate and support the maturation of immune cells, including plasmacytoid dendritic cells and B lymphocytes, that express Toll-like receptor 9 (TLR9) and are capable of presenting tumor antigens to T cells. Thus, CpG ODN are effective vaccine adjuvants. The adjuvant activity of CpG ODN is improved by maintaining them in close physical and temporal proximity to the co-administered vaccine antigen. This work describes a method of chemically conjugating CpG ODN to antigens and/or cancer cells that improve the resulting CTL response.

Recent progress concerning CpG DNA and its use as a vaccine adjuvant

CpG Oligonucleotides (ODN) are immunomodulatory synthetic oligonucleotides designed to specifically agonize Toll-like receptor 9. Here, we review recent progress in understanding the mechanism of action of CpG ODN and provide an overview of human clinical trial results using CpG ODN to improve the vaccines for cancer, allergy and infectious disease.

TLR9-mediated ARF6 activation is involved in advancing CpG ODN cellular uptake

Nucleic acid cellular uptake into endosomes is critical in eliciting nucleotide-sensing toll-like receptors (TLRs) innate immune responses. ADP-ribosylation factor 6 (ARF6) is a member of the Ras superfamily, which is critical to a wide variety of cellular events including endocytosis. Our previous report indicated that ARF6 plays a critical role in CpG ODN/TLR9-mediated responses. Here, we further explored that the basal level of active ARF6 is nonspecifically responsible for initiation of ODNs uptake, which is relatively CpG motif independent. While the initiation of CpG ODN uptake but not GpC ODN uptake can promote TLR9 responses thereby enhancing ARF6 activation which may lead to further nonspecifically increase of cellular uptake of stimulatory CpG ODN as well as nonstimulatory GpC ODN. Because nucleotide-sensing TLR9 plays a role in contributing to immune diseases, selective activation or inhibition of ARF6 might be useful in certain immunological or therapeutic applications.

TLR ligand-peptide conjugate vaccines: toward clinical application

Approaches to treat cancer with therapeutic vaccination have made significant progress. In order to induce efficient antitumor immunity, a vaccine should target and activate antigen-presenting cells, such as the dendritic cell, while delivering the tumor-derived antigen of choice. Conjugates of synthetic peptides and ligands of pattern-recognition receptors (PRRs) combine these features and, given their synthetic nature, can be produced under GMP conditions. Therefore, conjugation of antigenic peptides to potent PRR ligands is a promising vaccination approach for the treatment of cancer. This review focuses on the different PRR families that can be exploited for the design of conjugates and explores the results obtained so far with PRR ligands conjugated to antigen. The uptake and processing of Toll-like receptor ligand-peptide conjugates are discussed in more detail, as well as future directions that may further enhance the immunogenicity of conjugates.

Pivotal role of ADP-ribosylation factor 6 in Toll-like receptor 9-mediated immune signaling

CpG oligodeoxynucleotide (CpG ODN) cellular uptake into endosomes, the rate-limiting step of Toll-like receptor 9 (TLR9) signaling, is critical in eliciting innate immune responses. ADP-ribosylation factor 6 (ARF6) is a member of the Ras superfamily, which is critical to a wide variety of cellular events including endocytosis. Here, we found that inhibition of ARF6 by dominant mutants and siRNA impaired CpG ODN-mediated responses, whereas cells expressing the constitutively active ARF6 mutant enhanced CpG ODN-induced cytokine production. Inhibition of ARF6 impaired TLR9 trafficking into endolysosomes, thereby inhibiting proceed functional cleavage of TLR9. Additional studies showed that CpG ODN uptake was increased in ARF6-activated cells but impaired in ARF6-defective cells. Furthermore, cells pretreated with CpG ODN but not GpC ODN had increased CpG ODN uptake due to CpG ODN-induced ARF6 activity. Further studies with ARF6-defective and ARF6-activated cells demonstrated that class III phosphatidylinositol 3-kinases (PI3K) was required for downstream ARF6 regulation of CpG ODN uptake. Together, our findings demonstrate that a novel class III PI3K-ARF6 axis pathway mediates TLR9 signaling by regulating the cellular uptake of CpG ODN.

CpG or IFN-α are more potent adjuvants than GM-CSF to promote anti-tumor immunity following idiotype vaccine in multiple myeloma

Idiotype (Id) protein in combination with GM-CSF has been used as vaccines for immunotherapy of patients with myeloma and B-cell tumors and the results have been disappointing. To search for better immune adjuvants to improve the efficacy of Id-based immunotherapy in myeloma, we evaluated and compared the efficacy of vaccination of Id protein in combination with CpG or IFN-α, or GM-CSF as a control, in the 5TGM1 myeloma mouse model. Our results showed that Id vaccine combined with CpG or IFN-α, but not GM-CSF, not only efficiently protected mice from developing myeloma but also eradicated established myeloma. The therapeutic responses were associated with an induction of strong humoral immune responses including anti-Id antibodies, and cellular immune responses including Id- and myeloma-specific CD8+ cytotoxic T lymphocytes (CTLs), CD4+ type-1 T-helper (Th1) cells and memory T cells in mice receiving Id vaccine combined with CpG or IFN-α. Furthermore, Id vaccine combined with CpG or IFN-α induced Id- and tumor-specific memory immune responses that protected surviving mice from tumor rechallenge. Thus, our study clearly shows that CpG or IFN-α are better immune adjuvants than GM-CSF. This information will be important for improving the strategies of Id-based immunotherapy for patients with myeloma and other B-cell tumors.

Immunostimulatory CpG-DNA and PSA-peptide vaccination elicits profound cytotoxic T cell responses

OBJECTIVE

Novel strategies for the treatment of advanced prostate cancer (CaP), including immunotherapy or gene therapy, are currently under evaluation with Sipuleucel-T as first FDA-approved immunotherapeutic. Here, we examine cytosine-phosphorothioate-guanine (CpG)-DNA oligonucleotides (ODN) to boost cytokine responses and costimulatory molecule expression on murine bone marrow-derived dendritic cells (mBMDC). Furthermore, we evaluate the potency of a PSA-peptide based vaccine in combination with CpG-DNA to elicit specific cytotoxic T cell (CTL) responses.

MATERIALS AND METHODS

mBMDC were stimulated with CpG-DNA (1668: 5'-TCCATGACGTTCCTGATGCT-3') or non-stimulatory control-ODN (1720: 5'-TCCATGAGCTTCCTGATGCT-3'). Subsequently, expression of the costimulatory molecules CD40 and CD86 and induction of proinflammatory cytokines (interleukin (IL)-6 and IL-12) were analyzed. For induction of PSA-peptide specific CTL, female C57BL/6 mice were immunized with PSA-peptide 65-73 (HCIRNKSVI) alone or in combination with 1668 or 1720-ODN. In vivo cytotoxicity assay determined PSA-peptide specific cytotoxicity 1 week after vaccination.

RESULTS

Treatment of mBMDC with stimulatory CpG-DNA ODN resulted in pronounced up-regulation of costimulatory molecule expression on mBMDC in a dose-dependent manner. CpG-ODN significantly increased production of IL-6 and IL-12 in mBMDC (P < 0.001). Induction of PSA-peptide specific CTL responses in mice immunized with PSA-peptide and CpG-DNA were significantly greater than those of PSA-peptide and control-ODN immunized mice or PSA-peptide only vaccination.

CONCLUSIONS

CpG-DNA acts as potent adjuvant for vaccination therapies and elicits profound PSA-peptide specific CTL responses in combination with an immunodominant PSA-peptide. CpG-ODN mediated immunotherapy represents a potentially inexpensive, safe, easy-to-produce, and easy-to-handle treatment alternative. Therefore, further evaluation of CpG-DNA in immunization therapies against CaP is warranted.

CpG and non-CpG oligodeoxynucleotides directly costimulate mouse and human CD4+ T cells through a TLR9- and MyD88-independent mechanism

TLR ligands are known to activate APCs, but direct T cell responsiveness to TLR ligands is controversial. Because of their clinical relevance, we performed in-depth studies of the effects of the TLR9-associated ligands, oligodeoxynucleotides (ODNs), on highly purified T lymphocytes. Both CpG and non-CpG ODNs directly costimulate mouse and human CD4(+) T cells, resulting in activation marker upregulation, cytokine secretion, elevated TCR phosphorylation, and proliferation. Surprisingly, ODN costimulation occurred independently of TLR9 and MyD88, as well as ICOS, CD28, and TRIF. TLR9-antagonist ODNs likewise promoted T cell activation, which has important implications for the study of these "inhibitory" ODNs in inflammatory diseases. Cytokine profiling revealed that ODNs promote polarization of distinct Th subsets, and that ODNs differentially affect human naive and memory T cells. Our studies reveal a striking and unexpected ability of ODNs to directly activate and polarize T cells, presenting an opportunity to enhance the paradigm for selection of therapeutic ODNs in humans.

Adjuvant properties of Cytosine-phosphate-guanosine oligodeoxynucleotide in combination with various polycations in an ovalbumin-vaccine model

Oligonucleotides containing CpG motifs (cytosine-phosphate-guanosine oligodeoxynucleotide [CpG ODN]) display strong immunostimulatory effects, and polycations have been previously reported as cellular delivery system. In the present study, we investigated the adjuvant properties of combinations of a CpG ODN with various polycations (poly-arginine, poly-lysine, poly-histidine, or chitosan) in an ovalbumin vaccination model. We showed that, when combined to CpG ODN, poly-arginine and poly-histidine, but not poly-lysine or chitosan, enhanced efficiently both the IgG antibody production and the number of splenocytes secreting interferon-gamma after stimulation with a CD8+ T cell-restricted peptide. Interestingly, CpG ODN-poly-arginine, which was the most efficient, compared favorably to the complete Freund's adjuvant and aluminium salts and induced no local toxicity, making this combination a very attractive adjuvant for vaccines.

Conjugation of lipid and CpG-containing oligonucleotide yields an efficient method for liposome incorporation

For optimal stimulation of T cells, protein-based vaccines must deliver protein antigens to antigen-presenting cells while simultaneously providing immunostimulatory signals. Listeriolysin O (LLO)-containing liposomes have been utilized to efficiently deliver protein antigens to the cytosolic pathway for antigen processing and major histocompatibility complex class I-dependent presentation while codelivering immunostimulatory CpG-oligodeoxyribonuceotides (ODNs). In this report, we describe the synthesis of lipid-CpG-ODN conjugates utilizing maleimide-phosphatidylethanolamine (PE) lipids and 5'-sulfhdryl-containing CpG-ODNs as a method for facile incorporation of CpG-ODNs in liposomal vaccine carriers, an alternative to co-encapsulation inside liposomes and as a means to enhance delivery of CpG-ODNs to their major receptor, Toll-like receptor 9 (TLR9), in the endosome. The characterization and biological evaluation of the vaccine delivery system made of liposomes, which contain the lipid-CpG-ODN conjugates inserted in the liposomal membrane, is described. We demonstrate in vitro in bone marrow derived macrophages that the lipid-CpG-ODN conjugates incorporated onto the liposome bilayers interact with their receptor TLR9 as readily as liposome-encapsulated ODNs and exert their immunostimulatory capabilities. The liposomal vaccine delivery systems were evaluated in mice using ovalbumin (OVA) as a model antigen, and the results indicate equally robust OVA-specific cytotoxic T lymphocyte responses and similar Th1 immune skewing capabilities between liposomes containing lipid-conjugated or encapsulated CpG-ODNs. Overall, this work indicates that conjugating PE lipids and CpG-ODNs results in an efficient method that allows facile incorporation of CpG-ODNs into a liposome-based delivery platform while retaining the immune-stimulating capabilities of CpG-ODNs.

Soluble proteins induce strong CD8+ T cell and antibody responses through electrostatic association with simple cationic or anionic lipopeptides that target TLR2

The low immunogenicity exhibited by most soluble proteins is generally due to the absence of molecular signatures that are recognized by the immune system as dangerous. In this study, we show that electrostatic binding of synthetic branched cationic or anionic lipopeptides that contain the TLR-2 agonist Pam(2)Cys markedly enhance a protein's immunogenicity. Binding of a charged lipopeptide to oppositely charged protein Ags resulted in the formation of stable complexes and occurs at physiologic pH and salt concentrations. The induction of cell-mediated responses is dependent on the electrostatic binding of lipopeptide to the protein, with no CD8(+) T cells being elicited when protein and lipopeptide possessed the same electrical charge. The CD8(+) T cells elicited after vaccination with lipopeptide-protein Ag complexes produced proinflammatory cytokines, exhibited in vivo lytic activity, and protected mice from challenge with an infectious chimeric influenza virus containing a single OVA epitope as part of the influenza neuraminidase protein. Induction of a CD8(+) T cell response correlated with the ability of lipopeptide to facilitate Ag uptake by DCs followed by trafficking of Ag-bearing cells into draining lymph nodes. Oppositely charged but not similarly charged lipopeptides were more effective in DC uptake and trafficking. Very high protein-specific Ab titers were also achieved by vaccination with complexes composed of oppositely charged lipopeptide and protein, whereas vaccination with similarly charged constituents resulted in significant but lower Ab titers. Regardless of whether similarly or oppositely charged lipopeptides were used in the induction of Ab, vaccination generated dominant IgG1 isotype Abs rather than IgG2a.

Allergic rhinitis is associated with decreased expression of Toll-like receptor 9 by sinonasal epithelial cells

BACKGROUND

Toll-like receptors (TLRs) are important in sinonasal mucosal innate immunity. Previous studies demonstrate that sinonasal epithelial cell (SNEC) TLR9 expression is reduced in T-helper 2 (Th2) cytokine-predominant chronic rhinosinusitis with polyps, and with the in vitro application of Th2 cytokines. To further investigate in vivo modulation of TLR9 by the local cytokine environment, this study examines TLR9 expression in freshly isolated SNECs from subjects with and without active allergic rhinitis (AR).

METHODS

SNECs were gathered via endoscopic-guided middle meatal brushings from 9 AR subjects who were skin-prick test (SPT)-positive to environmental allergens in season at the time of study, and 8 controls. Flow cytometry was utilized to compare SNEC TLR9 expression in the 2 groups.

RESULTS

TLR9 expression by SNEC in the AR group was significantly reduced compared to normals (35% ± 26% vs 76% ± 10%, p = 0.002).

CONCLUSION

Similar to observations in eosinophilic chronic rhinosinusitis, this study shows that active AR is associated with decreased SNEC TLR9 expression. These findings are consistent with the concept that Th2 cytokines suppress expression of TLR9 and other innate immune genes. Multiple endogenous and microbial factors likely modulate sinonasal innate immunity to maintain homeostasis and prevent infection in AR.

CpG-conjugated apoptotic tumor cells elicit potent tumor-specific immunity

The primary goal of cancer immunotherapy is to elicit an immune response capable of eradicating established tumors and preventing tumor metastasis. One strategy to achieve this goal utilizes whole killed tumor cells as the primary immunogen. Killed tumor cells provide a comprehensive source of tumor-associated antigens (TAAs), thereby eliminating the need to identify individual antigens. Unfortunately, killed tumor cells tend to be poorly immunogenic. To overcome this limitation, we covalently conjugated immunostimulatory CpG oligodeoxynucleotides (ODN) to apoptotic tumor cells and examined their ability to induce TAA-specific immune responses. Results indicate that CpG conjugation enhances the uptake of cell-based vaccines by dendritic cells (DCs), up-regulates co-stimulatory molecule expression, and promotes the production of immunostimulatory cytokines. Vaccination with CpG-conjugated tumor cells triggers the expansion of tumor-specific cytotoxic T lymphocytes (CTL) that reduce the growth of established tumors and prevents their metastatic spread. Thus, conjugating CpG ODN to cell-based tumor vaccines is an important step toward improving cancer immunotherapy.

The capacity to induce cross-presentation dictates the success of a TLR7 agonist-conjugate vaccine for eliciting cellular immunity

Covalent conjugation of TLR agonists to protein Ags often facilitates the generation of a CD8(+) T cell response. However, mechanisms underlying the efficacy of the conjugate over its unconjugated counterpart have been largely uninvestigated. In this study, we show that conjugation of a TLR7 agonist enhances CD8(+) T cell responses without affecting Ag persistence and with minimal impact on cellular uptake of the Ag in vivo. Instead, the conjugated form induced a robust accumulation of dendritic cells (DCs) in regional lymph nodes. Perhaps more importantly, cross-presentation in DCs was detected only when the Ag was delivered in the conjugated form with the TLR7 agonist. Collectively, these data represent the first demonstration that a TLR agonist-Ag conjugate elicits CD8(+) T cell responses based not on its capacity to induce DC maturation or Ag persistence and uptake, but on the engagement of DC cross-presentation pathways.

Oligonucleotide based-strategies for allergy with special reference to siRNA

BACKGROUND

Allergic diseases are a significant global health care problem. Current pharmacological approaches address symptoms but do not alter the underlying immune dysregulation. Current allergen-specific immunotherapy has several drawbacks. Therefore, approaches that attenuate allergic responses safely and effectively at the level of upstream causative events are desirable. Oligonuleotide-based therapies [CpG DNA, antisense oligonucleotides, and small interfering RNA (siRNA)] are promising approaches.

OBJECTIVE/METHODS

We review developments in oligonucleotide-based therapies and the potential of siRNA for treating allergy.

RESULTS/CONCLUSIONS

Strategies with oligonucleotides basically aim to reduce T helper type 2 (Th2) responses. It is controversial whether the reduction of Th2 responses does, in fact, attenuate allergic diseases. Increased understanding of allergic mechanisms will enhance the efficacy of oligonucleotide-based therapy.

Innate immunity

Recent years have witnessed an explosion of interest in the innate immune system. Questions about how the innate immune system senses infection and empowers a protective immune response are being answered at the molecular level. These basic science discoveries are being translated into a more complete understanding of the central role innate immunity plays in the pathogenesis of many human infectious and inflammatory diseases. It is particularly exciting that we are already seeing a return on these scientific investments with the emergence of novel therapies to harness the power of the innate immune system. In this review we explore the defining characteristics of the innate immune system, and through more detailed examples, we highlight recent breakthroughs that have advanced our understanding of the role of innate immunity in human health and disease.

Immunomodulation of allergic disease

This review focuses on sublingual immunotherapy (SLIT), toll-like receptor-9 (TLR-9) vaccines using cytosine phosphorothioate guanosine (CpG)-allergen conjugates, and anti-IL-5 as novel immunomodulating therapies in allergy. At present, all three approaches are investigational in the United States and require further study to determine their safety and effectiveness. SLIT provides a novel oral route of administering an allergen to induce tolerance to inhaled allergens. Studies of SLIT in allergic rhinitis demonstrate that it reduces symptoms and medication use and is associated with a low incidence of systemic allergic reactions. Initial phase II studies with TLR-9 vaccines conjugated to a ragweed allergen demonstrate that they reduce symptoms of allergic rhinitis during the ragweed season. Anti-IL-5 is effective as a corticosteroid-sparing agent in the hypereosinophilic syndrome. It has not shown benefit in moderate asthmatics with persistent symptoms but may reduce aspects of airway remodeling in asthma.

CpG-ODN-based immunotherapy is effective in controlling the growth of metastasized tumor cells

Synthetic oligodeoxynucleotides (ODN) containing unmethylated CpG motifs (CpG-ODN) act as potent immune stimulators by activating innate immunity through toll-like receptor 9. These immunomodulatory effects of CpG-ODN have been reported to be associated with anti-tumor immunity. In this study, we used a murine B16F10 melanoma model and a CT26 colon cancer model to assess whether CpG-ODN-based immunotherapy was effective in inhibiting tumor cells that have already metastasized to distant organs. Systemic administration of CpG-ODN after melanoma cell injection resulted in a significant inhibition of pulmonary colonization. When CpG-ODN was administered after tumor cell injection, it also inhibited pulmonary metastasis of the tumor cells, albeit to a lesser degree in the latter case. Systemic administration of CpG-ODN after subcutaneous inoculation of CT26 colon cancer cells diminished pulmonary metastasis from the primary tumor sites. Additionally, CpG-ODN also inhibited the growth of pulmonary colonization of the colon tumor cells when CpG-ODN was administered after the primary tumors had been surgically removed. These data indicate that CpG-ODN was effective in inhibiting pulmonary metastasis of the B16F10 melanoma and CT26 colon cancer cells, as well as the growth of metastasized tumor cells. Our results suggest that CpG-ODN-based immunotherapy may be beneficial in controlling micrometastasis after surgery in clinical settings.

Induction of multispecific Th-1 type immune response against HCV in mice by protein immunization using CpG and Montanide ISA 720 as adjuvants

Recent studies demonstrate that Th1-type immune responses against a broad spectrum of hepatitis C virus (HCV) gene products are crucial to the resolution of acute HCV infection. We investigated new vaccine approaches to augment the strength of HCV-specific Th1-type immune responses. ELISPOT assay revealed that single or multiple protein immunization using both CpG ODN and Montanide ISA 720 as adjuvants induced much stronger IFN-gamma-producing Th1 responses against core, NS3 and NS5b targets than did the formulation without these adjuvants. Protein vaccination using CpG ODN and Montanide ISA 720 as adjuvants also greatly enhanced humoral responses to HCV core, E1/E2 and NS3. When specific IgG isotypes were assayed, protein immunization using CpG ODN and Montanide ISA 720 as adjuvants produced higher titers of IgG2a dominant antibodies than did protein immunization alone, indicating a more Th1-biased pathway. This increase in IgG2a is consistent with the induction of Th1 cells secreting IFN-gamma demonstrated by ELISPOT assay. In conclusion, protein immunization using CpG ODN and Montanide ISA 720 as adjuvants greatly enhanced cellular (Th1 type) as well as humoral immune responses against HCV in Balb/c mice. The use of adjuvants appears critical to the induction of Th1 immune responses during HCV vaccination with recombinant proteins.

[Platelets "Toll-like receptor" engagement stimulates the release of immunomodulating molecules]

Platelets are nonnucleated cellular elements that play a role in the process of haemostasis, and also in various ways in innate immunity and in inflammation. Platelets also contain numerous secretory products and can exert critical roles in several aspects of haemostasis. In addition, they house and secrete a variety of cytokines, chemokines and associated molecules which behave as ligands for receptors/counterparts displayed by endothelial cells lining tissue vessels and most leukocyte subsets. These latter studies show that platelets have an important role in innate as well as adaptive immunity; thus platelets can take part in an immune directive response. Moreover, platelets display receptors for several types of cytokines/chemokines along with FcgammaRII receptors. Finally, platelets not only express a variety of Toll-like receptors, with recently identified functions or not as-yet fully identified, but have also been demonstrated to express the key tandem pair of inflammatory and antigen presentation molecules (CD40 and CD40-ligand/CD154), this latter function making them the major purveyors of soluble CD40L in the plasma. It appears that platelets may be regarded as one of the neglected components of immune cell regulators, and platelets contribute to some interesting aspects in bridging innate and adaptive immunity. We propose that platelets discriminate danger signals and adapt the subsequent responses, with polarized cytokine secretion. Platelets may recognize several types of infectious pathogens and limit microbial colonization by sequestering these pathogens and releasing immunomodulatory factors. This review allows us to re-explore indications that platelets exert direct anti-infection immunity and we will present experimentally-driven arguments in favour of a role of platelet TLR in regulating certain immune activities.

The adjuvant effect of CpG oligodeoxynucleotide linked to the non-toxic B subunit of cholera toxin for induction of immunity against H. pylori in mice

The present study was carried out to test the immunostimulatory and adjuvant effects of the non-toxic B subunit of cholera toxin (CTB), CpG oligodeoxynucleotide (ODN) and CpG ODN linked to CTB (CTB-CpG) for generation of immunity against H. pylori in mice. Herein, we showed that CTB-CpG induces more potent proinflammatory cytokine and chemokine responses in the cervical and the mesenteric lymph nodes (CLN and MLN, respectively) cells in vitro compared with those of CTB and CpG ODN. The adjuvant effects of these agents were examined following intranasal immunization of C57Bl/6 mice with H. pylori lysate in combination with CpG ODN, CTB or CTB-CpG. All three immunization regimes resulted in high H. pylori-specific IgG antibody responses; however, only the CTB-CpG and, to some extent, the CpG ODN immunized mice mounted a sustainable IgG2c antibody response. Importantly, mice immunized with H. pylori antigen and CTB-CpG or CpG ODN, but not CTB, developed strong H. pylori-specific proliferative and IFN-gamma responses in their MLN CD4+ T cells upon recall antigen stimulation in vitro. These mice also had significantly lower bacterial load compared with the control-infected mice. Furthermore, the CTB-CpG and the CpG ODN immunized mice developed increased specific IgA antibody responses in their gastrointestinal tracts following H. pylori challenge. These results imply that CTB-CpG and CpG ODN, but not CTB, could serve as nasal adjuvants for induction of a H. pylori-specific Th1 type immunity in MLN and also a specific mucosal IgA antibody response in the gastrointestinal tract upon H. pylori challenge.

B subunit of Shiga toxin-based vaccines synergize with alpha-galactosylceramide to break tolerance against self antigen and elicit antiviral immunity

The nontoxic B subunit of Shiga toxin (STxB) targets in vivo Ag to dendritic cells that preferentially express the glycolipid Gb(3) receptor. After administration of STxB chemically coupled to OVA (STxB-OVA) or E7, a polypeptide derived from HPV, in mice, we showed that the addition of alpha-galactosylceramide (alpha-GalCer) resulted in a dramatic improvement of the STxB Ag delivery system, as reflected by the more powerful and longer lasting CD8(+) T cell response observed even at very low dose of immunogen (50 ng). This synergy was not found with other adjuvants (CpG, poly(I:C), IFN-alpha) also known to promote dendritic cell maturation. With respect to the possible mechanism explaining this synergy, mice immunized with alpha-GalCer presented in vivo the OVA(257-264)/K(b) complex more significantly and for longer period than mice vaccinated with STxB alone or mixed with other adjuvants. To test whether this vaccine could break tolerance against self Ag, OVA transgenic mice were immunized with STxB-OVA alone or mixed with alpha-GalCer. Although no CTL induction was observed after immunization of OVA transgenic mice with STxB-OVA, tetramer assay clearly detected specific anti-OVA CD8(+) T cells in 8 of 11 mice immunized with STxB-OVA combined with alpha-GalCer. In addition, vaccination with STxB-OVA and alpha-GalCer conferred strong protection against a challenge with vaccinia virus encoding OVA with virus titers in the ovaries reduced by 5 log compared with nonimmunized mice. STxB combined with alpha-GalCer therefore appears as a promising vaccine strategy to more successfully establish protective CD8(+) T cell memory against intracellular pathogens and tumors.

Polylactide-coglycolide microspheres co-encapsulating recombinant tandem prion protein with CpG-oligonucleotide break self-tolerance to prion protein in wild-type mice and induce CD4 and CD8 T cell responses

Prion diseases are fatal neurodegenerative diseases that are characterized by the conformational conversion of the normal, mainly alpha-helical cellular prion protein (PrP) into the abnormal beta-sheet-rich infectious isoform (PrP(Sc)). The immune system neither shows reaction against cellular PrP nor PrP(Sc), most likely due to profound self-tolerance. In previous studies, we were able to partly overcome self-tolerance using recombinantly expressed dimeric PrP (tandem PrP (tPrP)), in association with different adjuvants. Proof of principle for antiprion efficacy was obtained in vitro and in vivo. In this study, we demonstrate the induction of a specific Th1 T cell response in wild-type mice immunized with tPrP and CpG-oligonucleotide (ODN). Biochemical influences such as refolding conditions, ionic strength, pH, and interaction with CpG-ODN affected antigenic structure and thus improved immunogenicity. Furthermore, s.c. immunization with tPrP and CpG-ODN co-encapsulated in biodegradable polylactide-coglycolide microspheres (PLGA-MS) enhanced CD4 T cell responses and, more prominent, the induction of CD8 T cells. In this vaccination protocol, PLGA-MS function as endosomal delivery device of Ag plus CpG-ODN to macrophages and dendritic cells. In contrast, PLGA-MS-based DNA vaccination approaches with a tPrP construct generated poor humoral and T cell responses. Our data show that prophylactic and therapeutic immunization approaches against prion infections might be feasible using tPrP Ag and CpG-ODN adjuvant without detectable side effects.

Vaccine protocols for enhanced immunogenicity of exogenous antigens

Vaccination protocols aim at the delivery of exogenous antigen (Ag) to antigen-presenting cells (APCs) concurrent with the activation of APCs by adjuvants. Activated APCs then cross-present the Ag, cross-prime T effector cells, and activate B cells. Classical protocols rely on a mixture of both Ag and the adjuvant. However, a disadvantage of this strategy is that simultaneous "loading" and activation of APCs is not guaranteed. As a consequence, heterogeneous APC populations will be generated, including APCs being either Ag-presenting or only activated, thus rendering the adaptive immune response suboptimal. Therefore, novel strategies are needed that provide both constituents to the same APC in order to generate a homogeneous Ag-presenting and activated cell population. Here we show that these requirements can be fulfilled via two distinct methods, either by covalently linking Ag to the adjuvant or by co-encapsulating Ag and adjuvant into biodegradable microparticles. These novel vaccine protocols allow the generation of robust T-cell and B-cell responses that match immunogenicity of live vectors. Their characteristics with regard to efficacy, flexibility, and clinical applicability are discussed.

Distinct uptake mechanisms but similar intracellular processing of two different toll-like receptor ligand-peptide conjugates in dendritic cells

Covalent conjugation of Toll-like receptor ligands (TLR-L) to synthetic antigenic peptides strongly improves antigen presentation in vitro and T lymphocyte priming in vivo. These molecularly well defined TLR-L-peptide conjugates, constitute an attractive vaccination modality, sharing the peptide antigen and a defined adjuvant in one single molecule. We have analyzed the intracellular trafficking and processing of two TLR-L conjugates in dendritic cells (DCs). Long synthetic peptides containing an ovalbumin cytotoxic T-cell epitope were chemically conjugated to two different TLR-Ls the TLR2 ligand, Pam(3)CysSK(4) (Pam) or the TLR9 ligand CpG. Rapid and enhanced uptake of both types of TLR-L-conjugated peptide occurred in DCs. Moreover, TLR-L conjugation greatly enhanced antigen presentation, a process that was dependent on endosomal acidification, proteasomal cleavage, and TAP translocation. The uptake of the CpG approximately conjugate was independent of endosomally-expressed TLR9 as reported previously. Unexpectedly, we found that Pam approximately conjugated peptides were likewise internalized independently of the expression of cell surface-expressed TLR2. Further characterization of the uptake mechanisms revealed that TLR2-L employed a different uptake route than TLR9-L. Inhibition of clathrin- or caveolin-dependent endocytosis greatly reduced uptake and antigen presentation of the Pam-conjugate. In contrast, internalization and antigen presentation of CpG approximately conjugates was independent of clathrin-coated pits but partly dependent on caveolae formation. Importantly, in contrast to the TLR-independent uptake of the conjugates, TLR expression and downstream TLR signaling was required for dendritic cell maturation and for priming of naïve CD8(+) T-cells. Together, our data show that targeting to two distinct TLRs requires distinct uptake mechanism but follows similar trafficking and intracellular processing pathways leading to optimal antigen presentation and T-cell priming.

Immunotherapy with CpG DNA conjugated with T-cell epitope peptide of an allergenic Cry j 2 protein is useful for control of allergic conditions in mice

Immunotherapy using T-cell epitope peptides or CpG DNA conjugated with allergenic protein is useful, although the mechanisms of these therapies differ. However, the combination of CpG DNA and peptide, but not protein, had not been documented. Therefore, we investigated CpG DNA conjugated with peptide to obtain positive synergistic effects. In the first experiment, mice were vaccinated with a conjugate of CpG DNA and Cry j 2 T-cell epitope peptide p246-259 (CpG-peptide); a mixture of CpG DNA and peptide (CpG+peptide); peptide alone, or PBS alone, and immunized with Cry j 2. In the second experiment, mice were immunized with Cry j 2 and injected with CpG-peptide, CpG+peptide, peptide only, or PBS only. In both experiments, Cry j 2-specific IgE, IL-4, and IL-5 were significantly lower in mice given CpG-peptide, versus those given CpG+peptide, peptide alone, or PBS alone. However, IgG2a, IgG2b and IFN-gamma did not increase in mice injected with CpG-peptide. In the third experiment, CpG-peptide significantly attenuated nasal symptoms (sneezing and nasal rubbing) compared to CpG+peptide, peptide alone, or PBS alone. Mice were also injected with a conjugate of CpG DNA and Cry j 2 protein (CpG-Cry j 2) or CpG-peptide to compare prime responses. Mice vaccinated with CpG-Cry j 2 generated Cry j 2-specific IgG1, whereas those vaccinated with CpG-peptide did not produce IgG1. This study demonstrated, for the first time, that immunotherapy with CpG DNA conjugated with a T-cell peptide is useful in preventing and treating allergic conditions.

Oral sensitization to peanut is highly enhanced by application of peanut extracts to intact skin, but is prevented when CpG and cholera toxin are added

BACKGROUND

CpG oligonucleotides might offer an alternative to conventional immunotherapy in preventing and potentially reversing Th2-biased immune deregulation which leads to allergy. However, non-invasive ways of administration, especially in peanut-allergic patients, should be explored.

METHODS

One hundred micrograms of whole peanut protein extract (PE) alone, or mixed with cholera toxin (CT, 50 microg) plus CpG (100 microg) as adjuvant, was applied on intact skin of mice (40 min, twice). Initiation of an immune response was monitored by detection of specific antibodies in sera. The effect of this pretreatment on a further oral sensitization by PE was then evaluated by assaying antibodies and cytokines specific for PE and purified allergens. Cytokine production in liver 40 min after skin application was also assayed.

RESULTS

Two brief skin applications of PE alone highly potentiated further oral sensitization, as demonstrated by very intense specific IgE, IL-4 and IL-5 productions. Conversely, skin pretreatment with PE and CT + CpG efficiently prevented further sensitization via gastro-intestinal exposure. In both cases, the specificity of the antibodies and cytokines was the same as in control mice. CT + CpG treatment allowed the rapid production of IL-12 and TGFbeta in liver and of specific IgG2a in sera, suggesting the activation of Th1 and/or regulatory T cells.

CONCLUSIONS

Oral sensitization to peanut is highly enhanced by a previous short exposure of allergens to intact skin. Conversely, the use of CT + CpG adjuvant for skin application efficiently prevents further oral sensitization. The potential of such treatment in specific immunotherapy needs to be evaluated.

Toll-like Receptor Recognition Regulates Immunodominance in an Antimicrobial CD4+ T Cell Response

Although Toll-like Receptors (TLRs) play a major function in innate recognition of pathogens, their role in antigen processing and presentation in vivo is poorly understood. Here we establish that Toxoplasma gondii profilin, a TLR11 ligand present in the parasite, is an immunodominant antigen in the CD4(+) T cell response to the pathogen. The immunogenicity of profilin was entirely dependent on both TLR11 recognition and signaling through the adaptor myeloid differentiation factor 88 (MyD88). Selective responsiveness to this parasite protein was regulated at the level of antigen presentation by dendritic cells (DC) and required both TLR signaling and major histocompatibility complex (MHC) class II recognition acting in cis. These findings support a major influence of TLR recognition in antigen presentation by DC in vivo and establish a mechanism by which TLR ligand association regulates the immunogenicity of microbial antigens.

TLR9-based immunotherapy for allergic disease

A significant amount of data generated over the last few years supports the contention that Toll-like receptor (TLR) 9-based immunotherapy is effective in the prevention and treatment of animal models of allergic disorders. We will review here our experience with two distinct therapeutic strategies: TLR9-based immunomodulation and TLR9-based vaccination. Immunomodulation of allergic inflammation by TLR9 ligand (TLR9-L) is transient. It prevents both the early and late phases of the allergic reaction in experimental models of allergic asthma, rhinitis, and conjunctivitis. It also reverses ongoing allergic inflammation. Indoleamine 2.3-dioxygenase, the rate-limiting enzyme of tryptophan, is induced by TLR9-L and mediates, in part, these anti-inflammatory effects. TLR9-based immunomodulation is independent of allergens and, therefore, has a potential therapeutic advantage in a broad spectrum of allergic patients. On the other hand, TLR9-based vaccination therapy is an allergen-specific mode of immunotherapy, which provides long-term inhibition of allergen-specific hypersensitivities. Current clinical trials with TLR9-based immunotherapy demonstrate high immunogenic and therapeutic efficacy, as well as improved safety when compared with conventional allergen desensitization. Thus, if proven efficient, therapeutic strategies with TLR9-L may revolutionize the current treatment of allergic diseases.

Adjuvant activity of CpG oligodeoxynucleotides

Synthetic oligodeoxynucleotides (ODNs) containing unmethylated CpG motifs directly stimulate human B cells and plasmacytoid dendritic cells (pDCs), thereby promoting the production of Th1 and proinflammatory cytokines and the maturation/activation of professional antigen-presenting cells. These activities enable CpG ODNs to act as immune adjuvants, accelerating and boosting antigen-specific immune responses by 5- to 500-fold. The CpG motifs present in bacterial DNA plasmids may contribute to the immunogenicity of DNA vaccines. Ongoing clinical studies indicate that CpG ODNs are safe and well tolerated when administered as adjuvants to humans and can improve vaccine-induced immune responses.

Synthesis and in Vitro Characterization of Antigen-Conjugated Polysaccharide as a CpG DNA Carrier

Oligodeoxynucleotides containing unmethylated CpG sequences (CpG DNAs) are known as an immune adjuvant. CpG DNAs coupled with a particular antigen enabling both CpG DNA and antigen delivery to the same antigen-presenting cell have been shown to be more effective. Based on our previous finding that beta-(1-->3)-D-glucan schizophyllan (SPG) can be used as a CpG DNA carrier, here we present the synthesis of an antigen-conjugated SPG and the characterization of the conjugate. Ovalbumin (OVA, 43 kDa) was used as a model antigen, and two OVA were conjugated to one SPG molecule (M(w) = 150,000), denoted by OVA-SPG. Circular dichroism and gel electrophoresis showed that OVA-SPG could form a complex with a (dA)(40)-tailed CpG DNA at the 3' end (1,668-(dA)(40)). When OVA-SPG was added to macrophages (J774.A1), the amount of the ingested OVA-SPG was increased compared with that of OVA itself, suggesting that Dectin-1 (proinflammatory nonopsonic receptor for beta-glucans) is involved to ingest OVA-SPG. Furthermore, the complex of the conjugate and DNA was co-localized in the same vesicles, implying that OVA (antigen) and CpG DNA (adjuvant) were ingested into the cell at the same time. This paper shows that OVA-SPG can be used as a CpG DNA carrier to induce antigen-specific immune responses.

Contribution of interferon-beta to the immune activation induced by double-stranded DNA

Introducing double-stranded DNA (dsDNA) into the cytoplasm of macrophages and dendritic cells triggers the activation of these professional antigen-presenting cells (APCs). This process is characterized by the up-regulation of costimulatory molecules and the production of various cytokines, chemokines, and antibacterial/viral factors. Current findings indicate that interferon-beta (IFN-beta) plays a key role in the stimulatory cascade triggered by dsDNA. Both immune and non-immune cells respond to intracytoplasmic dsDNA by up-regulating IFN-beta) expression, a process that reduces host susceptibility to infection. The immune activation induced by dsDNA is independent of MyD88, TRIF and DNA-PKcs, indicating that a Toll-like receptor-independent mechanism underlies the cellular activation mediated by intracytoplasmic dsDNA.