Immunostimulatory DNA pre-priming: a novel approach for prolonged Th1-biased immunity

Destabilising Effect of Class B CpG Adjuvants on Different Proteins and Vaccine Candidates

Background: Adjuvants function by enhancing the breadth, durability, and magnitude of the immune response, but little is known about their impact on vaccine stability. CpG is a widely used adjuvant that is included in several recently approved COVID-19 vaccines using Spike protein, RBD, or whole inactivated virus. Methods: Here, we investigate the in vitro stability of the Receptor-Binding Domain (RBD) of the SARS-CoV-2 Spike protein, as well as a number of other proteins formulated with a class B CpG adjuvant. Results: We show that RBD, BSA, and lysozyme proteins are less thermally stable, more aggregation-prone, and more protease-sensitive in the presence of CpG than without it, and that these effects are enhanced with prolonged incubation. For RBD, the effects of CpG are pH-independent but dependent on the salt concentration, with relative destabilisation decreasing with an increasing salt concentration, indicative of an electrostatic component to the interaction between CpG and the protein. The reduced thermal and proteolytic stability found in the presence of CpG is indicative of a preferential interaction of CpG with the unfolded state of the protein relative to its native state. It remains to be determined if these in vitro characteristics are unique to CpG or are also shared by other non-CpG commercial adjuvants, if they are antigen-dependent, and if and how they correlate with the in vivo immunogenicity of an adjuvanted vaccine. Conclusions: It is demonstrated that the CpG adjuvant is critical to enhancing immunogenicity and is a key reason for the success of multiple licensed commercial vaccines. Nonetheless, our work suggests that careful and systematic in vitro formulation studies may be warranted for the development of suitable, stable formulations of CpG-adjuvanted vaccine candidates.

Cancer vaccine designed from homologous ferritin-based fusion protein with enhanced DC-T cell crosstalk for durable adaptive immunity against tumors

Peptide vaccines based on tumor antigens face the challenges of rapid clearance of peptides, low immunogenicity, and immune suppressive tumor microenvironment. However, the traditional solution mainly uses exogenous substances as adjuvants or carriers to enhance innate immune responses, but excessive inflammation can damage adaptive immunity. In the current study, we propose a straightforward novel nanovaccine strategy by employing homologous human ferritin light chain for minimized innate immunity and dendritic cell (DC) targeting, the cationic KALA peptide for enhanced cellular uptake, and suppressor of cytokine signaling 1 (SOCS1) siRNA for modulating DC activity. Upon fusing with the KALA peptide, this nanovaccine presents as a novel 40-mer cage structure, with highly enriched antigen peptides of proper size (25 nm) for targeted delivery to lymph nodes. The loading of SOCS1 siRNA onto the KALA peptide promoted DC maturation in tumor environment, leading to a 3-fold increase in antigen presentation compared to alum adjuvant. Moreover, it demonstrates remarkable efficacy in suppressing tumor progression and metastasis, together with prolonged survival. In addition, the nanovaccine stimulates up to 40 % memory T cells, thereby achieving sustained protection against tumor re-challenge. This unprecedented nanovaccine platform can ignite fresh interdisciplinary discussions on interactive strategies for future peptide vaccine development.

Sustained chronic inflammation and altered childhood vaccine responses in children exposed to Zika virus

BACKGROUND

Congenital Zika virus (ZIKV) infection leads to severe newborn abnormalities, but its long-term impact on childhood immunity is not well understood. This study aims to investigate the serum proteomics in children exposed to ZIKV during pregnancy to understand potential immunological consequences during early childhood.

METHODS

The study included ZIKV-exposed infants (ZEI) at birth (n = 42) and children exposed to ZIKV (ZEC) at two years of age (n = 20) exposed to ZIKV during pregnancy, as well as healthy controls. Serum proteomic analysis was performed on these groups to assess inflammation and immune profiles. Additionally, antibody titres against two common childhood vaccines, DTaP and MMR, were measured in healthy controls (n = 50) and ZEC (n = 92) to evaluate vaccine-induced immunity.

FINDINGS

Results showed elevated inflammation in ZEI with birth abnormalities. Among ZEC, despite most having normal clinical outcomes at two years, their serum proteomics indicated a bias towards Th1-mediated immune responses. Notably, ZEC displayed reduced anti-Diphtheria toxin and anti-Clostridium tetani IgG levels against DTaP and MMR vaccines. They also exhibited lower antibody titres particularly against Th2-biased DTaP vaccines, but not Th1-biased MMR vaccines.

INTERPRETATION

In conclusion, the study highlights the long-term immunological consequences of congenital ZIKV exposure. Heightened inflammation was observed in ZEI with abnormalities at birth, while ZEC maintained a chronic Th1-biased immune profile. The impaired response to Th2-biased vaccines raises concerns about lasting effects of ZIKV exposure on immune responses. Consequently, there is a need for continued longitudinal clinical monitoring to identify potential immune-related complications arising from prenatal exposure to ZIKV.

FUNDING

This work was partially funded by the National Institute of Allergy and Infectious Diseases (NIAID) and National Institute of Dental and Craniofacial Research (NIDCR).

Process development for an effective COVID-19 vaccine candidate harboring recombinant SARS-CoV-2 delta plus receptor binding domain produced by Pichia pastoris

Recombinant protein-based SARS-CoV-2 vaccines are needed to fill the vaccine equity gap. Because protein-subunit based vaccines are easier and cheaper to produce and do not require special storage/transportation conditions, they are suitable for low-/middle-income countries. Here, we report our vaccine development studies with the receptor binding domain of the SARS-CoV-2 Delta Plus strain (RBD-DP) which caused increased hospitalizations compared to other variants. First, we expressed RBD-DP in the Pichia pastoris yeast system and upscaled it to a 5-L fermenter for production. After three-step purification, we obtained RBD-DP with > 95% purity from a protein yield of > 1 g/L of supernatant. Several biophysical and biochemical characterizations were performed to confirm its identity, stability, and functionality. Then, it was formulated in different contents with Alum and CpG for mice immunization. After three doses of immunization, IgG titers from sera reached to > 10⁶ and most importantly it showed high T-cell responses which are required for an effective vaccine to prevent severe COVID-19 disease. A live neutralization test was performed with both the Wuhan strain (B.1.1.7) and Delta strain (B.1.617.2) and it showed high neutralization antibody content for both strains. A challenge study with SARS-CoV-2 infected K18-hACE2 transgenic mice showed good immunoprotective activity with no viruses in the lungs and no lung inflammation for all immunized mice.

Approaches of the Innate Immune System to Ameliorate Adaptive Immunotherapy for B-Cell Non-Hodgkin Lymphoma in Their Microenvironment

A dominant paradigm being developed in immunotherapy for hematologic malignancies is of adaptive immunotherapy that involves chimeric antigen receptor (CAR) T cells and bispecific T-cell engagers. CAR T-cell therapy has yielded results that surpass those of the existing salvage immunochemotherapy for patients with relapsed/refractory diffuse large B-cell lymphoma (DLBCL) after first-line immunochemotherapy, while offering a therapeutic option for patients with follicular lymphoma (FL) and mantle cell lymphoma (MCL). However, the role of the innate immune system has been shown to prolong CAR T-cell persistence. Cluster of differentiation (CD) 47-blocking antibodies, which are a promising therapeutic armamentarium for DLBCL, are novel innate immune checkpoint inhibitors that allow macrophages to phagocytose tumor cells. Intratumoral Toll-like receptor 9 agonist CpG oligodeoxynucleotide plays a pivotal role in FL, and vaccination may be required in MCL. Additionally, local stimulator of interferon gene agonists, which induce a systemic anti-lymphoma CD8⁺ T-cell response, and the costimulatory molecule 4-1BB/CD137 or OX40/CD134 agonistic antibodies represent attractive agents for dendritic cell activations, which subsequently, facilitates initiation of productive T-cell priming and NK cells. This review describes the exploitation of approaches that trigger innate immune activation for adaptive immune cells to operate maximally in the tumor microenvironment of these lymphomas.

Influenza Vaccines: Successes and Continuing Challenges

Influenza vaccines have been available for over 80 years. They have contributed to significant reductions in influenza morbidity and mortality. However, there have been limitations in their effectiveness, in part due to the continuous antigenic evolution of seasonal influenza viruses, but also due to the predominant use of embryonated chicken eggs for their production. The latter furthermore limits their worldwide production timelines and scale. Therefore today, alternative approaches for their design and production are increasingly pursued, with already licensed quadrivalent seasonal influenza vaccines produced in cell cultures, including based on a baculovirus expression system. Next-generation influenza vaccines aim at inducing broader and longer-lasting immune responses to overcome seasonal influenza virus antigenic drift and to timely address the emergence of a new pandemic influenza virus. Tailored approaches target mechanisms to improve vaccine-induced immune responses in individuals with a weakened immune system, in particular older adults.

Protein Immunization Induces Memory CD4+ T Cells That Lack Th Lineage Commitment

Acute viral infection generates lineage-committed Th1 and T follicular helper (Tfh) memory cells that recall their lineage-specific functions following secondary challenge with virus. However, the lineage commitment of effector and memory Th cells in vivo following protein vaccination is poorly understood. In this study, we analyzed effector and memory CD4⁺ T cell differentiation in mice (Mus musculus) following adjuvanted glycoprotein immunization compared with acute lymphocytic choriomeningitis virus infection. Glycoprotein immunization induced CXCR5^- non-Tfh effector and memory CD4⁺ T cells that surprisingly had not undergone polarization toward any particular Th cell lineage but had undergone memory differentiation. However, upon challenge with virus, these Th lineage-nonpolarized memory CD4⁺ T cells were able to generate Th1 secondary effector cells, demonstrating their lineage plasticity. In addition, Tfh and memory Tfh cells were generated in response to protein immunization, and these cells differed from infection-induced Tfh cells by their lack of the transcription factor Tbet. Rechallenge experiments demonstrated that viral infection, but not protein immunization, during either the primary or secondary immune response, restricts the recall of Bcl6 expression and the generation of germinal center Tfh cells. Together, these data demonstrate that protein immunization generates a combination of nonpolarized memory cells that are highly plastic and memory Tfh cells that can undergo further Th1-like modulation during a secondary response to viral infection.

An mRNA SARS-CoV-2 Vaccine Employing Charge-Altering Releasable Transporters with a TLR-9 Agonist Induces Neutralizing Antibodies and T Cell Memory

The SARS-CoV-2 pandemic has necessitated the rapid development of prophylactic vaccines. Two mRNA vaccines have been approved for emergency use by the FDA and have demonstrated extraordinary effectiveness. The success of these mRNA vaccines establishes the speed of development and therapeutic potential of mRNA. These authorized vaccines encode full-length versions of the SARS-CoV-2 spike protein. They are formulated with lipid nanoparticle (LNP) delivery vehicles that have inherent immunostimulatory properties. Different vaccination strategies and alternative mRNA delivery vehicles would be desirable to ensure flexibility of future generations of SARS-CoV-2 vaccines and the development of mRNA vaccines in general. Here, we report on the development of an alternative mRNA vaccine approach using a delivery vehicle called charge-altering releasable transporters (CARTs). Using these inherently nonimmunogenic vehicles, we can tailor the vaccine immunogenicity by inclusion of coformulated adjuvants such as oligodeoxynucleotides with CpG motifs (CpG-ODN). Mice vaccinated with the mRNA-CART vaccine developed therapeutically relevant levels of receptor binding domain (RBD)-specific neutralizing antibodies in both the circulation and in the lung bronchial fluids. In addition, vaccination elicited strong and long-lasting RBD-specific T_H1 T cell responses including CD4⁺ and CD8⁺ T cell memory.

The next generation of HCV vaccines: a focus on novel adjuvant development

INTRODUCTION

Considerable efforts have been made to treat and prevent acute and chronic infections caused by the hepatitis C virus (HCV). Current treatments are unable to protect people from reinfection. Hence, there is a need for development of both preventive and therapeutic HCV vaccines. Many vaccine candidates are in development to fight against HCV, but their efficacy has so far proven limited partly due to low immunogenicity.

AREAS COVERED

We explore development of novel and powerful adjuvants to achieve an effective HCV vaccine. The basis for developing strong adjuvants is to understand the innate immunity pathway, which subsequently stimulates humoral and cellular immune responses. We have also investigated immunogenicity of developed adjuvants that have been used in recent studies available in online databases such as PubMed, PMC, ScienceDirect, Google Scholar, etc.

EXPERT OPINION

Adjuvants are used as a part of vaccine formulation to boost vaccine immunogenicity and antigen delivery. Several FDA-approved adjuvants are used in licensed human vaccines. Unfortunately, no adjuvant has yet been proven to boost HCV immune responses to the extent needed for an effective vaccine. One of the promising approaches for developing an effective adjuvant is the combination of various adjuvants to trigger several innate immune responses, leading to activation of adaptive immunity.[Figure: see text].

An mRNA SARS-CoV-2 vaccine employing Charge-Altering Releasable Transporters with a TLR-9 agonist induces neutralizing antibodies and T cell memory

The SARS-CoV-2 pandemic has necessitated the rapid development of prophylactic vaccines. Two mRNA vaccines have been approved for emergency use by the FDA and have demonstrated extraordinary effectiveness. The success of these mRNA vaccines establishes the speed of development and therapeutic potential of mRNA. These authorized vaccines encode full-length versions of the SARS-CoV-2 spike protein. They are formulated with Lipid Nanoparticle (LNP) delivery vehicles that have inherent immunostimulatory properties. Different vaccination strategies and alternative mRNA delivery vehicles would be desirable to ensure flexibility of future generations of SARS-CoV-2 vaccines and the development of mRNA vaccines in general. Here, we report on the development of an alternative mRNA vaccine approach using a delivery vehicle called Charge-Altering Releasable Transporters (CARTs). Using these inherently nonimmunogenic vehicles we can tailor the vaccine immunogenicity by inclusion of co-formulated adjuvants such as oligodeoxynucleotides with CpG motifs (CpG-ODN). Mice vaccinated with the mRNA-CART vaccine developed therapeutically relevant levels of RBD-specific neutralizing antibodies in both the circulation and in the lung bronchial fluids. In addition, vaccination elicited strong and long lasting RBD-specific T _H 1 T cell responses including CD4 ⁺ and CD8 ⁺ T cell memory.

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.

CD4+ T Cells Induced by Tuberculosis Subunit Vaccine H1 Can Improve the HIV-1 Env Humoral Response by Intrastructural Help

The induction of a potent and long-lasting, broadly neutralizing antibody response is one of the most promising approaches in HIV-1 vaccination. Recently, we demonstrated that Gag-specific T helper cells induced by DNA priming can enhance and modulate the HIV Env-specific B cell response upon virus-like particle (VLP) boost by intrastructural help (ISH). In order to minimize the induction of potentially harmful HIV specific T_H cells, we explored the possibility to harness the heterologous T_H cells induced by a recombinant tuberculosis subunit vaccine H1, which contains a fusion protein of Ag85B and ESAT-6 antigens in combination with the liposomal adjuvant CAF01. To provide ISH, immunodominant MHC-II restricted peptides from the H1 vaccine were genetically incorporated into the HIV 1 Gag protein and used for HIV VLP production. ISH effects on Env-specific antibody levels and B cell differentiation were analyzed in mice primed against H1 and boosted with VLPs. In contrast to non-primed mice, a significant increase of Env-specific IgG levels for up to 26 weeks after the last immunization was observed. This increase was largely caused by elevated IgG2b and IgG2c levels in mice that received H1 priming. Additionally, ISH enhanced the frequency of Env-specific long-lived plasma cells in the bone marrow. In this study, we were able to demonstrate that a heterologous prime-boost regimen consisting of the H1 tuberculosis subunit vaccine and T helper epitope modified HIV-1 VLPs resulted in enhanced HIV Env antibody and B cell responses, mediated by intrastructural help.

Innate Immune Response against Hepatitis C Virus: Targets for Vaccine Adjuvants

Despite successful treatments, hepatitis C virus (HCV) infections continue to be a significant world health problem. High treatment costs, the high number of undiagnosed individuals, and the difficulty to access to treatment, particularly in marginalized susceptible populations, make it improbable to achieve the global control of the virus in the absence of an effective preventive vaccine. Current vaccine development is mostly focused on weakly immunogenic subunits, such as surface glycoproteins or non-structural proteins, in the case of HCV. Adjuvants are critical components of vaccine formulations that increase immunogenic performance. As we learn more information about how adjuvants work, it is becoming clear that proper stimulation of innate immunity is crucial to achieving a successful immunization. Several hepatic cell types participate in the early innate immune response and the subsequent inflammation and activation of the adaptive response, principally hepatocytes, and antigen-presenting cells (Kupffer cells, and dendritic cells). Innate pattern recognition receptors on these cells, mainly toll-like receptors, are targets for new promising adjuvants. Moreover, complex adjuvants that stimulate different components of the innate immunity are showing encouraging results and are being incorporated in current vaccines. Recent studies on HCV-vaccine adjuvants have shown that the induction of a strong T- and B-cell immune response might be enhanced by choosing the right adjuvant.

Unmethylated CpG motif-containing genomic DNA fragment of Bacillus calmette-guerin promotes macrophage functions through TLR9-mediated activation of NF-B and MAPKs signaling pathways

The potency of synthetic CpG-oligo-deoxynucleotides (CpG-ODNs) adjuvants in modulating the immune cell functions through the TLR pathway has been tested and reported previously. However, the cellular signaling involved in the stimulation of macrophages by natural, CpG motif-containing adjuvant and the effector functions modulated by such stimulation has not been well studied. Here, we used in vitro and ex vivo murine macrophage assay systems, and mouse model of in vivo stimulation to explore the signaling pathway and the effector functions mediated by BC01. Results show that BC01 can induce the production of TNF-α and MCP-1 in macrophages by up-regulating the activation of NF-κB and MAPKs signaling pathway, and elevated the expression of MHC-II, CD40, CD80, and CD86. Upon stimulation with BC01, the peritoneal macrophages isolated from TLR9−/− mice produced significantly low levels of pro-inflammatory cytokines, attenuated the activation of NF-κB and MAPKs signaling pathways, and showed reduced phagocytosis. Following in vivo stimulation with BC01, the TLR9−/− mice produced significantly lower levels of pro-inflammatory cytokines in the serum and lymph nodes showed reduced cell proliferation. These results indicate that BC01 is an efficient agonist of TLR9 that can significantly enhance the host-protective immune functions of macrophages.

Assessment of the immunogenicity and protective efficiency of a novel dual-promoter DNA vaccine, harboring SAG1 and GRA7 genes, from RH strain of Toxoplasma gondii in BALB/c mice

BACKGROUND

Toxoplasmosis, a protozoan parasitic disease caused by Toxoplasma gondii, has been a serious human and veterinary medicine problem with global distribution. In the current study, we assessed immunogenicity and protective efficiency of a novel dual-promoter DNA vaccine, harboring SAG1 and GRA7 genes, from RH strain of Toxoplasma gondii (T. gondii) with or without CpG-ODN as adjuvant in a murine model.

METHODS

BALB/c mice were immunized intramuscularly with pVitro-SAG1-GRA7 alone and pVitro-SAG1-GRA7 with CpG-ODN three times at three-week intervals. Enzyme-linked immunosorbent assay (ELISA) was used to assess total IgG, IgG1 and IgG2a antibodies and gamma interferon (IFN-γ) and interleukin-10 (IL-10) cytokines in mice sera. Four weeks post final vaccination, MTT assay and lethal challenge-infection with 1×103 tachyzoites of T. gondii RH strain were carried out to assess stimulation index (SI) and mice survival time, respectively.

RESULTS

The IgG levels in mice immunized with multicomponent vaccines, including pVitro-SAG1-GRA7 alone and pVitro-SAG1-GRA7 with CpG-ODN, were significantly higher than those in control mice or single-gene DNA-vaccinated ones (P<0.05). Furthermore, level of IgG2a in mice receiving pVitro-SAG1-GRA7 with CpG-ODN was significantly higher than that in mice receiving pVitro-SAG1-GRA7 alone (P<0.05). The Toxoplasma lysate antigen (TLA)-stimulated lymphocytes from pVitro-SAG1-GRA7 with CpG-ODN group responded more dramatically than those from control groups or single-gene DNA-vaccinated groups (P<0.001). The pVitro-SAG1-GRA7 with CpG-ODN-vaccinated mice developed high levels of IgG2a and IFN-γ (P<0.001) and low levels of IgG1 and IL-10, compared to control groups, suggesting a modulated immune response type Th1. In addition, survival time of the mice immunized with pVitro-SAG1-GRA7 with CpG-ODN was significantly extended, compared to controls (P<0.05); however, all mice died.

CONCLUSION

The multivalent pVitro-SAG1-GRA7 DNA vaccine with CpG-ODN adjuvant is a promising vaccine candidate against toxoplasmosis.

Immunogenicity of a Bivalent Adjuvanted Glycoconjugate Vaccine against Salmonella Typhimurium and Salmonella Enteritidis

Salmonella enterica serovars Typhimurium and Enteritidis are the predominant causes of invasive non-typhoidal Salmonella (iNTS) disease. Considering the co-endemicity of S. Typhimurium and S. Enteritidis, a bivalent vaccine formulation against both pathogens is necessary for protection against iNTS disease, thus investigation of glycoconjugate combination is required. In the present work, we investigated the immune responses induced by S. Typhimurium and S. Enteritidis monovalent and bivalent glycoconjugate vaccines adjuvanted with aluminum hydroxide (alum) only or in combination with cytosine-phosphorothioate-guanine oligodeoxynucleotide (CpG). Humoral and cellular, systemic and local, immune responses were characterized in two different mouse strains. All conjugate vaccines elicited high levels of serum IgG against the respective O-antigens (OAg) with bactericidal activity. The bivalent conjugate vaccine induced systemic production of antibodies against both S. Typhimurium and S. Enteritidis OAg. The presence of alum or alum + CpG adjuvants in vaccine formulations significantly increased the serum antigen-specific antibody production. The alum + CpG bivalent vaccine formulation triggered the highest systemic anti-OAg antibodies and also a significant increase of anti-OAg IgG in intestinal washes and fecal samples, with a positive correlation with serum levels. These data demonstrate the ability of monovalent and bivalent conjugate vaccines against S. Typhimurium and S. Enteritidis to induce systemic and local immune responses in different mouse strains, and highlight the suitability of a bivalent glycoconjugate formulation, especially when adjuvanted with alum + CpG, as a promising candidate vaccine against iNTS disease.

CpG oligodeoxynucleotide nanomedicines for the prophylaxis or treatment of cancers, infectious diseases, and allergies

Unmethylated cytosine-guanine dinucleotide-containing oligodeoxynucleotides (CpG ODNs), which are synthetic agonists of Toll-like receptor 9 (TLR9), activate humoral and cellular immunity and are being developed as vaccine adjuvants to prevent or treat cancers, infectious diseases, and allergies. Free CpG ODNs have been used in many clinical trials implemented to verify their effects. However, recent research has reported that self-assembled CpG ODNs, protein/peptide–CpG ODN conjugates, and nanomaterial–CpG ODN complexes demonstrate higher adjuvant effects than free CpG ODNs, owing to their improved uptake efficiency into cells expressing TLR9. Moreover, protein/peptide–CpG ODN conjugates and nanomaterial–CpG ODN complexes are able to deliver CpG ODNs and antigens (or allergens) to the same types of cells, which enables a higher degree of prophylaxis or therapeutic effect. In this review, the author describes recent trends in the research and development of CpG ODN nanomedicines containing self-assembled CpG ODNs, protein/peptide–CpG ODN conjugates, and nanomaterial–CpG ODN complexes, focusing mainly on the results of preclinical and clinical studies.

Cocaine Vaccine Development: Evaluation of Carrier and Adjuvant Combinations That Activate Multiple Toll-Like Receptors

Although cocaine abuse and addiction continue to cause serious health and societal problems, an FDA-approved medication to treat cocaine addiction has yet to be developed. Employing a pharmacokinetic strategy, an anticocaine vaccine provides an attractive avenue to address these issues; however, current vaccines have shown varying degrees of efficacy, indicating that further formulation is necessary. As a means to improve vaccine efficacy, we examined the effects of varying anticocaine vaccine formulations by combining a Toll-like receptor 9 (TLR9) agonist with a TLR5 agonist in the presence of alum. The TLR9 agonist used was cytosine-guanine oligodeoxynucleotide 1826 (CpG 1826), while the TLR5 agonist was flagellin (FliC). Formulations with the TLR9 agonist elicited superior anticocaine antibody titers and blockade of hyperlocomotor effects compared to vaccines without CpG 1826. This improvement was seen regardless of whether the TLR5 agonist, FliC, or the nonadjuvanting Tetanus Toxoid (TT) was used as the carrier protein. Additional insights into the value of FliC as a carrier versus adjuvant was also investigated by generating two unique formats of the protein, wild-type and mutated flagellin (mFliC). While the mFliC conjugate retained its ability to stimulate mTLR5, it yielded reduced cocaine sequestration and functional blockade relative to FliC and TT. Overall, this work indicates that activation of TLR9 can improve the function of cocaine vaccines in the presence of TLR5 activation by FliC, with any potential additive effects limited by the inefficiency of FliC as a carrier protein as compared to TT.

Adjuvants in the Driver's Seat: How Magnitude, Type, Fine Specificity and Longevity of Immune Responses Are Driven by Distinct Classes of Immune Potentiators

The mechanism by which vaccine adjuvants enhance immune responses has historically been considered to be the creation of an antigen depot. From here, the antigen is slowly released and provided to immune cells over an extended period of time. This "depot" was formed by associating the antigen with substances able to persist at the injection site, such as aluminum salts or emulsions. The identification of Pathogen-Associated Molecular Patterns (PAMPs) has greatly advanced our understanding of how adjuvants work beyond the simple concept of extended antigen release and has accelerated the development of novel adjuvants. This review focuses on the mode of action of different adjuvant classes in regards to the stimulation of specific immune cell subsets, the biasing of immune responses towards cellular or humoral immune response, the ability to mediate epitope spreading and the induction of persistent immunological memory. A better understanding of how particular adjuvants mediate their biological effects will eventually allow them to be selected for specific vaccines in a targeted and rational manner.

Mechanisms of action of adjuvants

Adjuvants are used in many vaccines, but their mechanisms of action are not fully understood. Studies from the past decade on adjuvant mechanisms are slowly revealing the secrets of adjuvant activity. In this review, we have summarized the recent progress in our understanding of the mechanisms of action of adjuvants. Adjuvants may act by a combination of various mechanisms including formation of depot, induction of cytokines and chemokines, recruitment of immune cells, enhancement of antigen uptake and presentation, and promoting antigen transport to draining lymph nodes. It appears that adjuvants activate innate immune responses to create a local immuno-competent environment at the injection site. Depending on the type of innate responses activated, adjuvants can alter the quality and quantity of adaptive immune responses. Understanding the mechanisms of action of adjuvants will provide critical information on how innate immunity influences the development of adaptive immunity, help in rational design of vaccines against various diseases, and can inform on adjuvant safety.

CpG DNA as a vaccine adjuvant

Synthetic oligodeoxynucleotides (ODNs) containing unmethylated CpG motifs trigger cells that express Toll-like receptor 9 (including human plasmacytoid dendritic cells and B cells) to mount an innate immune response characterized by the production of Th1 and proinflammatory cytokines. When used as vaccine adjuvants, CpG ODNs improve the function of professional antigen-presenting cells and boost the generation of humoral and cellular vaccine-specific immune responses. These effects are optimized by maintaining ODNs and vaccine in close proximity. The adjuvant properties of CpG ODNs are observed when administered either systemically or mucosally, and persist in immunocompromised hosts. Preclinical studies indicate that CpG ODNs improve the activity of vaccines targeting infectious diseases and cancer. Clinical trials demonstrate that CpG ODNs have a good safety profile and increase the immunogenicity of coadministered vaccines.

Vaccine adjuvants: putting innate immunity to work

Adjuvants enhance immunity to vaccines and experimental antigens by a variety of mechanisms. In the past decade, many receptors and signaling pathways in the innate immune system have been defined and these innate responses strongly influence the adaptive immune response. The focus of this review is to delineate the innate mechanisms by which adjuvants mediate their effects. We highlight how adjuvants can be used to influence the magnitude and alter the quality of the adaptive response in order to provide maximum protection against specific pathogens. Despite the impressive success of currently approved adjuvants for generating immunity to viral and bacterial infections, there remains a need for improved adjuvants that enhance protective antibody responses, especially in populations that respond poorly to current vaccines. However, the larger challenge is to develop vaccines that generate strong T cell immunity with purified or recombinant vaccine antigens.

Inflammatory bowel diseases: when natural friends turn into enemies-the importance of CpG motifs of bacterial DNA in intestinal homeostasis and chronic intestinal inflammation

From numerous studies during the last years it became evident that bacteria and bacterial constituents play a decisive role both in the maintenance of intestinal immune homeostasis as well as in the development and perpetuation of chronic intestinal inflammation. In this review we focus on the role of bacterial DNA which is a potent immunomodulatory component of the bacterial flora. Bacterial DNA has been shown to be protective against experimental colitis. In contrast bacterial DNA essentially contributes to the perpetuation of an already established chronic intestinal inflammation in a Toll-like receptor (TLR)9-dependent manner. This dichotomic action may be explained by a different activation status of essential regulators of TLR signaling like Glycogen synthase kinase 3-β (GSK3-β) depending on the pre-activation status of the intestinal immune system. In this review we suggest that regulators of TLR signaling may be interesting therapeutic targets in IBD aiming at the restoration of intestinal immune homeostasis.

Presence of bacterial-DNA in cirrhosis identifies a subgroup of patients with marked inflammatory response not related to endotoxin

BACKGROUND/AIMS

Serum lipopolysaccharide-binding protein and bacterial-DNA have been proposed as markers of bacterial translocation and this study aimed to evaluate the immune response registered by bacterial-DNA from Gram-positive and Gram-negative microorganisms and the effect on lipopolysaccharide-binding protein, to further investigate both markers.

METHODS

Thirty-two patients were distributed into two groups according to the presence of bacterial-DNA, determined by broad-range PCR of 16SrRNA gene. Serum endotoxin, lipopolysaccharide-binding protein, cytokines and nitric oxide products were measured by ELISA.

RESULTS

Serum endotoxin and lipopolysaccharide-binding protein were non-significantly higher in patients with bacterial-DNA than in those without bacterial-DNA. Regarding patients with bacterial-DNA from Gram-positive microorganisms (n = 8), these levels were similar to those in patients without bacterial-DNA (n = 16), and significantly lower than in patients with bacterial-DNA from Gram-negative bacteria. Tumour necrosis factor-alpha and interleukin-6 were significantly increased in patients with vs without bacterial-DNA (324.93+/-70.76 vs 134.91+/-34.58microg/mL; p<0.05; 294.96+/-87.48 vs 175.92+/-60.58microg/mL, p < 0.05, respectively). Patients with bacterial-DNA from Gram-positive microorganisms also showed significantly higher levels for both cytokines than patients without bacterial-DNA, and similar to those in patients with bacterial-DNA from Gram-negative bacteria.

CONCLUSIONS

Patients with translocation of bacterial-DNA from Gram-positive microorganisms showed increased proinflammatory cytokines unrelated to endotoxin, which would not be detected by serum lipopolysaccharide-binding protein measurement.

Impact of class A, B and C CpG-oligodeoxynucleotides on in vitro activation of innate immune cells in human immunodeficiency virus-1 infected individuals

Oligodeoxynucleotides (ODN) with unmethylated deoxycytidyl-deoxyguanosine dinucleotides (CpG-ODNs) stimulate Toll-like receptor 9 (TLR9) in plasmacytoid dendritic cells (pDC) and B cells and activate innate and adaptive immunity. Three classes of synthetic CpG-ODNs, class A, B and C, activate cells through TLR9; our goal was to evaluate their effect on cells from human immunodeficiency virus (HIV)-1(+) individuals. We compared the frequencies and the unstimulated activation status of immune effector cells in HIV-1(+) and HIV-1(-) individuals. Fewer pDC, myeloid dendritic cells (mDC), B cells, natural killer (NK) cells and invariant natural killer T cells (iNKT) were present in HIV-1(+) peripheral blood mononuclear cells (PBMC) and their baseline activation status was higher than HIV-1(-) PBMC. Exposure of HIV-1(+) PBMC to all classes of CpG-ODNs led to activation and maturation of pDC based on CD86, CD80, and CD83 expression similar to that of cells from HIV-1(-) individuals. The percentage of CpG-ODN stimulated pDC that express CD40 was dramatically higher when cells were obtained from HIV-1(+) than from HIV-1(-) individuals. B-lymphocytes were activated similarly in HIV-1(+) and HIV-1(-) individuals. mDC, NK and iNKT cell, which lack TLR9, were indirectly activated. Interferon-alpha (IFN-alpha) and interferon inducible protein 10 (IP-10) secretion was induced by class A or C but not class B CpG-ODN, but the concentrations were less than those produced by HIV-1(-) PBMC. HIV-1 infected individuals have fewer innate effector cells that are chronically activated, but these cells can be further activated by CpG-ODN, which suggests that synthetic CpG-ODNs could be used to enhance the immune system in HIV-1 infected individuals.

Update on toll-like receptor ligands and allergy: implications for immunotherapy

Innate responses to microbes are mediated in large part via toll-like receptors (TLRs) that recognize a diverse family of ligands produced by viruses, bacteria, and fungi. Great effort has been directed toward translating this knowledge into the development of therapies for the prevention and treatment of diseases, including those fueled by allergic (Th2-biased) hypersensitivities. In this review, we consider the ways in which ligands for different TLRs influence the allergic phenotype. In addition, an update on safety and efficacy data from clinical trials of allergic patients treated with TLR9 ligand-based interventions is provided. Finally, recent experimental results that help elucidate how ambient TLR ligand exposures influence allergic risk and their relevance to the development of TLR ligand-based therapeutics are discussed. Investigations presented within this opinion paper suggest that several TLR ligands could have clinical utility in the treatment of allergic diseases, whereas other TLR ligands appear less attractive, as they facilitate development of Th2-biased hypersensitivities in murine studies.

CpG oligodeoxynucleotides are potent enhancers of radio- and chemoresponses of murine tumors

BACKGROUND AND PURPOSE

Synthetic oligodeoxynucleotides (ODNs) containing unmethylated cytosine-guanine (CpG) motifs bind to Toll-like receptor 9 (TLR9) and stimulate both innate and adaptive immune reactions and possess anti-tumor activity. We recently reported that CpG ODN 1826 strongly enhances radioresponse of both immunogenic [Milas L, Mason K, Ariga H, et al. CpG oligodeoxynucleotide enhances tumor response to radiation. Cancer Res 2004;64:5074-7] and non-immunogenic [Mason KA, Ariga H, Neal R, et al. Targeting toll-like receptor-9 with CpG oligodeoxynucleotides enhances tumor response to fractionated radiotherapy. Clin Cancer Res 2005;11:361-9] murine tumors. Using two immunogenic murine tumors, a fibrosarcoma (FSa) and a mammary carcinoma (MCa-K), the present study explored whether CpG ODN 1826 also improves the response of murine tumors to the chemotherapeutic agent docetaxel (DOC).

MATERIALS AND METHODS

CpG ODN 1826 (100 microg) was given sc three times: when leg tumors were 6mm, when they grew to 8mm and again 1 week later. DOC (33 mg/kg iv) and local tumor radiation (10Gy) were given when tumors were 8mm. Effects of the treatments were assayed by tumor growth delay, defined as days for tumors to grow from 8 to 12 mm in diameter.

RESULTS

Treatment with CpG ODN 1826 resulted in strongly enhanced response of FSa tumors to radiation and MCa-K tumors to the chemotherapeutic agent DOC. Enhancement of tumor treatment response was demonstrated by a strong prolongation in the primary tumor treatment endpoint, tumor growth delay. Coincidentally, this treatment also resulted in a higher rate of tumor cure than that observed after tumor radiotherapy or chemotherapy alone. When all three agents were combined the effect was comparable to that of the combination of CpG ODN 1826 with radiation in the case of FSa or of the combination of CpG ODN 1826 with DOC in the case of MCa-K.

CONCLUSION

Overall results show that CpG ODN 1826 can markedly improve tumor response to radiation and chemotherapy (DOC), suggesting that CpG ODNs have potential to be beneficial when used singly or in combination with other standard treatment modalities such as taxane chemotherapy, radiotherapy or both.

Dietary nucleotides and human immune cells. II. Modulation of PBMC growth and cytokine secretion

OBJECTIVE

The immune system is dependent on purines and pyrimidines as building blocks for DNA and RNA synthesis to enable rapid cell proliferation and protein synthesis. Emerging evidence suggests that dietary nucleotides optimize immune function. We investigated whether growth and function of human immune cells were affected by an exogenous source of nucleotides during specific antigen challenge.

METHODS

Peripheral blood mononuclear cells from healthy individuals (n = 10) were stimulated with influenza virus antigen and either DNA sodium from fish soft roe (DNA), RNA from bakers yeast (Saccharomyces cerevisiae) (RNA), 2' deoxyadenosine 5'-monophosphate sodium (dAMP), 2' deoxycytidine 5'-monophosphate sodium (dCMP), 2' deoxyguanosine 5'-monophosphate sodium (dGMP), 2' deoxyuridine 5'-monophosphate sodium (dUMP) or thymidine sodium (TMP). Growth effects were ascertained by measuring the amount of tritium-labeled thymidine, incorporated into cell DNA. Cell function was measured by detection of IFN-gamma, TNF-alpha and IL-10 production.

RESULTS

Specific nucleotide derivatives alone did not affect the growth of healthy peripheral blood mononuclear cells. However, the nucleotide derivatives influenced immune cell growth and cytokine secretion when cocultured with specific antigen. DNA, RNA, dAMP, dCMP and dUMP increased influenza virus antigen induced immune cell proliferation. In contrast dGMP and TMP inhibited the antigen-induced growth response. RNA and dAMP cocultured with virus antigen significantly increased peripheral blood mononuclear cell secretion of IFN-gamma, IL-10 and TNF-alpha. DNA increased virus antigen-induced immune cell secretion of IFN-gamma only, whereas dUMP significantly increased secretion of IL-10 only. dGMP completely inhibited virus-triggered IFN-gamma secretion, whereas TMP did not change the virus induced secretion pattern of measured cytokines.

CONCLUSION

Nucleotide derivatives affect growth and function of specific virus antigen-stimulated human immune cells in vitro.

Toll-like receptor ligands and atopy: a coin with at least two sides

Allergic disease prevalence rates have increased dramatically in affluent countries over the last half century. One proposed explanation is that decreased exposures to microbes caused by modern public health practices has led to deficiencies in an important source of immune education and a consequent increase in the risk of pathogenic immune responses to environmental antigens. Recently, it has become clear that innate responses to microbes are mediated in large part by Toll-like receptors (TLRs), which recognize a diverse family of ligands produced by viruses, bacteria, and fungi. In this perspectives article we will review experimental evidence suggesting that TLRs also play a dominant role in innate responses to noninfectious immunostimulatory materials present in environments of daily living. We will further discuss how ligands for different TLRs can polarize the T(H) bias of adaptive responses in opposing directions. Finally, we will consider how TLRs might contribute to the genesis of atopy and the clinical potential of pharmacologic interventions that target TLRs for the prevention and treatment of allergic diseases.

Hyperproduction of IFN-gamma by CpG oligodeoxynucleotide-induced exacerbation of atopic dermatitis-like skin lesion in some NC/Nga mice

Under conventional conditions, NC/Nga mice spontaneously develop an atopic dermatitis (AD)-like skin lesion accompanied by immunoglobulin E (IgE) hyperproduction and the expression of T helper 2 (Th2) cytokines. CpG DNA activates a strong interferon-gamma (IFN-gamma)-dominated T helper 1 (Th1) response, while inhibiting Th2-dependent allergies. In this study, we examined whether CpG oligodeoxynucleotide (ODN) could prevent the development of the skin lesions in NC/Nga mice. Sixteen of 26 NC/Nga mice did not exhibit dermatitis after CpG ODN was administered intraperitoneally every 2 wk for a total of five times. CpG ODN administration induced IFN-gamma production, which inhibited the production of Th2 cytokines (interleukin (IL)-4, IL-5, and IL-13) in both spleen and lymph node cells and culminated in a decrease in the serum IgE level. These data suggest that the CpG ODN has a therapeutic effect against AD; however, some mice (10 of 26) treated with CpG ODN exhibited an exacerbation of dermatitis accompanied by the hyperproduction of IFN-gamma, although Th2 cytokines were suppressed. These results suggest that the suppression of Th2 cytokines may not completely prevent dermatitis and that IFN-gamma may play a role in developing dermatitis in some NC/Nga mice.

Dietary nucleotides and human immune cells. II. Modulation of PBMC growth and cytokine secretion

OBJECTIVE

The immune system is dependent on purines and pyrimidines as building blocks for DNA and RNA synthesis to enable rapid cell proliferation and protein synthesis. Emerging evidence suggests that dietary nucleotides optimize immune function. We investigated whether growth and function of human immune cells were affected by an exogenous source of nucleotides during specific antigen challenge.

METHODS

Peripheral blood mononuclear cells from healthy individuals (n = 10) were stimulated with influenza virus antigen and DNA-Na+ from fish soft roe, RNA from bakers yeast (Saccharomyces cerevisiae), 2'deoxyadenosine 5'-monophosphate sodium, 2'deoxycytidine 5'-monophosphate sodium, 2'deoxyguanosine 5'-monophosphate sodium, or 2'deoxyuridine 5'-monophosphate disodium. Growth effects were ascertained by measuring the amount of tritium-labeled Thymidine 5'-monophosphate sodium incorporated into cell DNA. Cell function was measured by detection of interferon-gamma (IFN-gamma), tumor necrosis factor-alpha, and interleukin-10 production.

RESULTS

Specific nucleotide derivatives alone did not affect the growth of healthy peripheral blood mononuclear cells. However, the nucleotide derivatives influenced immune cell growth and cytokine secretion when cocultured with specific antigen. DNA, RNA, deoxyadenosine monophosphate, deoxycytidine monophosphate, and deoxyuridine monophosphate increased influenza virus antigen-induced immune cell proliferation. In contrast, deoxyadenosine monophosphate and thymosine monophosphate inhibited the antigen-induced growth response. RNA and deoxyadenosine monophosphate cocultured with virus antigen significantly increased peripheral blood mononuclear cell secretion of IFN-gamma, interleukin-10, and tumor necrosis factor-alpha. DNA increased virus antigen-induced immune cell secretion of IFN-gamma only, whereas deoxyuridine monophosphate significantly increased secretion of interleukin-10 only. Deoxyguanosine monophosphate completely inhibited virus-triggered IFN-gamma secretion, whereas thymosine monophosphate did not change the secretion pattern of measured cytokines.

CONCLUSION

Nucleotide derivatives affect growth and function of specific virus antigen-stimulated human immune cells in vitro.

Salmonella typhimurium grown in iron-rich media, inactivated with ferric chloride and adjuvanted with homologous bacterial DNA is potent and efficacious vaccine in mice

The present study describes our attempt to construct a novel vaccine formulation that affords full protection against murine typhoid under experimental conditions. Ferric chloride, 100mM, as inactivating agent, bacterial growth under iron-rich conditions and homologous bacterial DNA as adjuvant were used for construction of the experimental Salmonella typhimurium vaccine. The vaccine inoculated twice at 2 weeks interval in Swiss albino mice elicited statistically significant IgG levels when compared with non-adjuvanted and other control groups. All the mice inoculated with the novel vaccine withstood challenge with 50 LD(50) dose of S. typhimurium strain St 585. No significant safety problems were found in mice.

Targeting Toll-like Receptor 9 with CpG Oligodeoxynucleotides Enhances Tumor Response to Fractionated Radiotherapy

Synthetic oligodeoxynucleotides containing unmethylated CpG motifs detected by Toll-like receptor 9 of dendritic cells and B cells have potent immunomodulatory effects. CpG oligodeoxynucleotides induce cytokines, activate natural killer cells, and elicit T-cell responses leading to antitumor effects, including improved efficacy of chemotherapeutic agents and, as we reported recently, synergy between CpG oligodeoxynucleotide 1826 and single-dose radiotherapy of an immunogenic mouse fibrosarcoma. The present study extends this finding to the fractionated radiotherapy of the fibrosarcoma tumor and assesses the ability of CpG oligodeoxynucleotide 1826 to increase the radioresponse of a tumor (nonimmunogenic fibrosarcoma). The experiments used a murine immunogenic fibrosarcoma tumor, fibrosarcoma growing in the leg of mice, and response to radiotherapy was assessed by tumor growth delay and tumor cure rate (TCD50, radiation dose yielding 50% tumor cure). Multiple s.c. peritumoral or i.t. administrations of CpG oligodeoxynucleotide 1826 at a dose of 100 μg per mouse were given when established tumors were 6 mm in diameter. Local tumor irradiation was initiated when tumors grew to 8 mm in diameter; radiation was delivered in 1 to 9 Gy fractions given twice daily separated by 6 to 7 hours for 5 consecutive days to achieve a total dose of 10 to 90 Gy. CpG oligodeoxynucleotide 1826, given as a single agent, had only a small antitumor effect, but it dramatically enhanced fibrosarcoma response to radiotherapy. Although 83.1 (79.2-90.0) Gy total dose were needed to achieve tumor cures in 50% of mice treated with radiotherapy alone, only 23.0 (11.5-32.7) Gy total dose were needed in mice treated with both CpG oligodeoxynucleotide 1826 and radiotherapy. The magnitude of potentiation of tumor radioresponse at the TCD50 level was by a factor of 3.61, a much higher value than that (a factor of 1.93) that we reported for single-dose radiotherapy. Mice cured of their tumors by combined CpG oligodeoxynucleotide 1826 plus radiotherapy were highly resistant to s.c. tumor take or development of tumor nodules in the lung from i.v. injected tumor cells when rechallenged with fibrosarcoma cells 100 to 120 days after the treatment, suggesting the development of a memory response. CpG oligodeoxynucleotide 1826 also increased radioresponse of the nonimmunogenic fibrosarcoma tumor by a factor of 1.41 and 1.73 when CpG oligodeoxynucleotide 1826 was given s.c. and i.t., respectively. These findings show that CpG oligodeoxynucleotides are highly potent enhancers of tumor response to both single-dose and fractionated radiation and as such have potential to improve clinical radiotherapy.

Induction of antigen cross-presentation by Toll-like receptors

Cross-presentation is the pathway by which exogenous antigens are routed for presentation on MHC class I for activation of CD8(+) T cells. This pathway is important for the development of CD8(+) cytotoxic T lymphocyte responses against tumors and infectious pathogens that do not directly infect APC. We review studies showing that certain Toll-like receptors mediate cross-presentation by dendritic cells, initiating cytosolic processing of antigen after inducing dendritic cell maturation. The implications of these studies for understanding CD8(+) T cell activation and implementing novel vaccine strategies is considered.

Allergen-independent immunostimulatory sequence oligodeoxynucleotide therapy attenuates experimental allergic rhinitis

While effective for the prevention and treatment of allergic rhinitis (AR) symptoms, currently available medications do not reverse allergen specific hypersensitivities. Therefore, pharmacotherapeutics are not curative and their daily use is often required for years. These investigations were conducted to determine whether immunostimulatory sequence oligodeoxynucleotide (ISS-ODN) delivery protects previously sensitized mice from AR hypersensitivity responses and modulates their allergen specific immune profiles. Mice were first sensitized with ovalbumin (OVA) and alum, twenty-four hr before beginning a series of seven daily intranasal (i.n.) allergen challenges, subsets of mice received a single i.n. or intradermal (i.d.) dose of ISS-ODN or control oligodeoxynucleotide (C-ODN), a single intraperitoneal (i.p.) injection of dexamethasone (DXM), or no intervention. Mice receiving i.d. or i.n. ISS-ODN were found to have attenuated immediate and late phase effector cell responses to i.n. OVA challenge. Specifically, ISS-ODN treated mice had less histamine and cysteinyl leukotriene release and eosinophilic inflammation in their nasal passages than mice treated with C-ODN. In addition, splenocytes from ISS-ODN but not C-ODN treated mice displayed attenuated OVA-specific interleukin (IL)-4, IL-5, and IL-13 but increased interferon-gamma responses. Finally, ISS-ODN was generally a more effective treatment than DXM, both in blunting AR hypersensitivity responses and in shifting T helper 2 Th2-biased immune parameters towards Th1 dominance. As ISS-ODN delivery rapidly attenuated effector cell responses in this AR model in an allergen independent manner, the present results suggest that therapy with ISS-ODN alone may be an effective alternative to corticosteroid medications for the clinical management of AR.

CpG immunostimulatory sequences enhance contact hypersensitivity responses in mice

Bacterial DNA and synthetic cytidine-phosphate-guanosine-oligodeoxynucleotides (CpG ODN) potently activate dendritic cells (DC) and therefore have been proposed as adjuvants for vaccination strategies. Although CpG ODN are considered as safe adjuvants this study shows that CpG ODN are responsible for enhanced antigen-specific skin inflammatory reactions. We used the murine model of contact hypersensitivity (CHS) to 2,4-dinitrofluorobenzene (DNFB) in which hapten-specific CD8+T cytotoxic 1 cells are effector cells. Subcutaneous injection of CpG ODN, 1 d before sensitization enhanced the CHS response to DNFB and resulted in increased recruitment of CD8+ T cells at the challenge sites, whereas control ODN injection did not have any effect. This effect was local and not systemic as it was only observed when DNFB was applied at the same site as the CpG motifs. CpG ODN-induced enhancement of CHS was due to increased antigen-presenting cell functions of DC since: (i) CpG ODN-injected skin revealed upregulated expression of major histocompatibility complex class II, CD80, and CD86 molecules and (ii) CpG ODN treatment of DNFB-derivatized DC enhanced the intensity of CHS responses after in vivo transfer. Taken together, the results show that CpG ODN may be responsible for immune side-effects such as worsening of T cell-mediated skin diseases.

Antigen-immunostimulatory oligonucleotide conjugates: mechanisms and applications

Conjugation of protein antigen with immunostimulatory oligonucleotides creates a potent immunogen. Physical linking of oligonucleotides to antigen enhances antigen uptake and targets the adjuvant properties of the oligonucleotides to the antigen-presenting cell. In addition, the conjugated oligonucleotides appear to have improved immunostimulatory abilities compared to free oligonucleotides, presumably due to enhanced activation of Toll-like receptor 9. Immunization with these conjugate preparations elicits antigen-specific antibody responses, a T-helper cell 1-biased cytokine profile from CD4 T cells, and CD8 cytotoxic T-lymphocyte activity that is CD4 independent. The humoral and cellular immune responses induced by these conjugates suggest they can be used to create effective vaccines against infectious pathogens and tumors and to beneficially modulate allergic responses. Indeed, recent clinical trial data show symptom relief and immunomodulation of the allergic response in patients with allergic rhinitis. This review considers the mechanisms of action of antigen-oligonucleotide conjugates and discusses available data regarding their use for the prevention and treatment of infectious, oncologic, and allergic diseases.

The therapeutic potential of antigen-oligonucleotide conjugates

Conjugation of protein antigen with immunostimulatory oligonucleotides creates a potent immunogen that elicits antigen-specific antibody responses, a Th1-biased cytokine profile, and CD8 cytotoxic T lymphocyte activity. The wide range of humoral and cellular immune responses induced by these conjugates suggests they can be used to create effective vaccines against infectious pathogens and tumors and to beneficially modulate the immune responses seen in allergic diseases. This review summarizes the available data on the use of antigen-oligonucleotide conjugates and discusses their potential use for the treatment of infectious, oncologic, and allergic diseases in humans.

Antitumor applications of stimulating toll-like receptor 9 with CpG oligodeoxynucleotides

Tumor immunotherapy has evolved from the use of crude bacterial extracts to chemically synthesized ligands for specific immune receptors, such as Toll-like receptors (TLRs). One of the most promising targets for therapeutic immune activation is TLR9, which detects unmethylated CpG dinucleotides present in viral and prokaryotic genomes, which are generally methylated in host DNA. This review describes the immune effects of synthetic CpG oligonucleotides as TLR9 ligands and their applications in cancer immunotherapy.

Contrasting activity of cytosin-guanosin dinucleotide oligonucleotides in mice with experimental colitis

Intestinal inflammation in inflammatory bowel disease (IBD) and experimental models of colitis is characterized by a dysregulated intestinal immune response with elevated levels of Th1 cytokines. The luminal flora has been implicated as a major factor contributing to the initiation and perpetuation of inflammation in experimental colitis by mechanisms not known. Bacterial DNA contains unmethylated cytosin-guanosin dinucleotides (CpG) which strongly activate Th1-mediated immune responses. To test whether these CpG-motifs modulate intestinal inflammation we treated mice with dextran sulphate sodium (DSS)-induced colitis with CpG-containing oligodeoxynucleotides (CpG-ODN). CpG-ODN given after the onset of DSS colitis aggravated the disease, as indicated by a significantly increased loss of body weight and a 30% increase of the histological score. Further, we found a severe increase of proinflammatory cytokines (interleukin (IL)-6: 40-fold; interferon (IFN)-gamma: 11-fold). In a pretreatment setting CpG-ODN reduced weight loss significantly and reduced intestinal inflammation by 45%. Colonic IFN-gamma and IL-6 mRNA levels were reduced by 75%, and IL-10 was elevated by 400% compared to controls. The prophylactic CpG-effect was not imitated by IL-12 because IL-12 pretreatment was not protective. In time-course experiments, CpG-ODN pretreatment over 5 days resulted in a tolerance effect concerning its IFN-gamma-inducing quality, and during the following days of colitis induction IL-10 secretion from mesenterial lymph node cells was elevated compared to controls. Therefore, the prophylactic effect of CpG-ODN might be explained by its tolerizing effect and/or the increased ability for IL-10 production during the consecutive intestinal inflammation.

Toll-like receptor-9 induced by physical trauma mediates release of cytokines following exposure to CpG motif in mouse skin

The skin plays a crucial role in defence against microbial infection via the innate immune system, but the exact cellular mechanisms of this defence are not well understood. Toll-like receptors (TLRs), a newly recognized 10-member family of vertebrate pattern recognition receptors (PRRs), have been identified as crucial mediators of innate immune recognition. Although both TLR2 and TLR4 have been detected in normal human skin, little is known about the expression and function of TLR9, a CpG motif receptor, in skin. In this study, reverse transcription-polymerase chain reaction and in situ hybridization analysis were used to identify TLR9 mRNA expression in mouse skin. Results showed that TLR9 mRNA was not detected in normal mouse skin, but its presence in skin could be induced by intradermal injection of either normal saline, or the bacteria-based CpG motif in a time- and volume-dependent manner. Furthermore, intradermal injection of CpG motif induced increased expression of mRNAs for proinflammatory cytokines such as interleukin (IL)-1, IL-6, IL-12 and tumour necrosis factor alpha. This suggests that TLR9, while not present basally in skin, can be induced by physical trauma and then mediate responses to CpG motif. In conclusion, TLR9 is involved in the innate immune response in skin and that it may have a role in secondary inflammation following physical trauma such as epidermal damage or microbial infection. This role of TLR9 may help explain the previously identified enhancement of DNA immunization by CpG ODN.

A subset of Toll-like receptor ligands induces cross-presentation by bone marrow-derived dendritic cells

Dendritic cells (DCs) are capable of cross-presenting exogenous Ag to CD8(+) CTLs. Detection of microbial products by Toll-like receptors (TLRs) leads to activation of DCs and subsequent orchestration of an adaptive immune response. We hypothesized that microbial TLR ligands could activate DCs to cross-present Ag to CTLs. Using DCs and CTLs in an in vitro cross-presentation system, we show that a subset of microbial TLR ligands, namely ligands of TLR3 (poly(inosinic-cytidylic) acid) and TLR9 (immunostimulatory CpG DNA), induces cross-presentation. In contrast to presentation of Ag to CD4(+) T cells by immature DCs, TLR-induced cross-presentation is mediated by mature DCs, is independent of endosomal acidification, and relies on cytosolic Ag processing machinery.