Three CpG oligodeoxynucleotide classes differentially enhance antigen-specific humoral and cellular immune responses in mice

Pivotal role of Helicobacter pylori virulence genes in pathogenicity and vaccine development

One of the most prevalent human infections is Helicobacter pylori (H. pylori), which affects more than half of the global population. Although H. pylori infections are widespread, only a minority of individuals develop severe gastroduodenal disorders. The global resistance of H. pylori to antibiotics has reached concerning levels, significantly impacting the effectiveness of treatment. Consequently, the development of vaccines targeting virulence factors may present a viable alternative for the treatment and prevention of H. pylori infections. This review aims to provide a comprehensive overview of the current understanding of H. pylori infection, with a particular focus on its virulence factors, pathophysiology, and vaccination strategies. This review discusses various virulence factors associated with H. pylori, such as cytotoxin-associated gene A (cagA), vacuolating cytotoxin gene (vacA), outer membrane proteins (OMPs), neutrophil-activated protein (NAP), urease (ure), and catalase. The development of vaccines based on these virulence characteristics is essential for controlling infection and ensuring long-lasting protection. Various vaccination strategies and formulations have been tested in animal models; however, their effectiveness and reproducibility in humans remain uncertain. Different types of vaccines, including vector-based vaccines, inactivated whole cells, genetically modified protein-based subunits, and multiepitope nucleic acid (DNA) vaccines, have been explored. While some vaccines have demonstrated promising results in murine models, only a limited number have been successfully tested in humans. This article provides a thorough evaluation of recent research on H. pylori virulence genes and vaccination methods, offering valuable insights for future strategies to address this global health challenge.

A new multi-epitope DNA vaccine against Helicobacter Pylori infection in a BALB/c mouse model

Background

Helicobacter Pylori (H. Pylori) is a pathogen that may invade the human stomach. This bacterial strain is now causing widespread concern and considerable health issues worldwide. In contrast to antibiotic treatment, which may lead to drug resistance, vaccination therapy is emerging as a possible immunotherapy option for H. Pylori. DNA vaccines are a potential option to traditional vaccines among vaccine research methods. Furthermore, the multiepitope DNA vaccination may induce a broader immune response to suppress H. Pylori infection.

Methods

Four target antigenic proteins (outer membrane beta-barrel, outer membrane beta, HofA, and hcp beta-lactamase-like protein) were used to identify epitopes. The best B and T cell epitopes were selected to induce humoral and cellular immune responses and were connected using the HEYGAEALERAG and GGGS linkers. The peptide's physicochemical characteristics, secondary and tertiary structures, antigenicity, and allergenicity were evaluated utilizing several bioinformatics tools. The multiepitope peptide was successfully inserted into the pcDNA3.1 expression vector. The immunological responses of both the vaccinated and control groups were evaluated by measuring cytokines and antibodies.

Results

Based on the data, the multiepitope peptide consists of 278 amino acid residues and has an average molecular weight (MW) of 28643.61 Da. The peptide residues were mainly situated within the preferred and permitted areas of the Ramachandran plot, accounting for 92.86 % of the total. The VaxiJen server has calculated that the multiepitope peptide has an antigenicity score of 1.0067. BALB/c mice vaccinated with the DNA vaccine produced significantly higher levels of specific IgG antibodies (p < 0.05). The vaccinated mice exhibited a TH1-type cellular immune response characterized by the generation of IFN-γ and a longer length of life compared to the control animals (p < 0.05). In addition, the vaccination group exhibited a substantial increase in the expression level of IFN-γ and IL-1β genes compared to the control group (p < 0.05).

Conclusions

The results demonstrated that the multiepitope DNA vaccine elicited significant humoral and cellular responses, and increased survival time in BALB/c mice, indicating that selecting potential epitopes may be a viable technique for developing multiepitope-based vaccines. This can help to introduce effective vaccines.

Tertiary lymphoid structures in ovarian cancer

Ovarian cancer (OC) is a significant cause of cancer-related mortality in women worldwide. Despite advances in treatment modalities, including surgery and chemotherapy, the overall prognosis for OC patients remains poor, particularly for patients with advanced or recurrent disease. Immunotherapy, particularly immune checkpoint blockade (ICB), has revolutionized cancer treatment in various malignancies but has shown limited efficacy in treating OC, which is primarily attributed to the immunologically. Tertiary lymphoid structures (TLSs), which are ectopic aggregates of immune cells, have emerged as potential mediators of antitumor immunity. This review explores the composition, formation, and induction of tumor associated TLS (TA-TLS) in OC, along with their role and therapeutic implications in disease development and treatment. By elucidating the roles TA-TLSs and their cellular compositions played in OC microenvironment, novel therapeutic targets may be identified to overcome immune suppression and enhance immunotherapy efficacy in ovarian cancer.

Emerging nanoparticle platforms for CpG oligonucleotide delivery

Unmethylated cytosine-phosphate-guanine (CpG) oligodeoxynucleotides (ODNs), which were therapeutic DNA with high immunostimulatory activity, have been applied in widespread applications from basic research to clinics as therapeutic agents for cancer immunotherapy, viral infection, allergic diseases and asthma since their discovery in 1995. The major factors to consider for clinical translation using CpG motifs are the protection of CpG ODNs from DNase degradation and the delivery of CpG ODNs to the Toll-like receptor-9 expressed human B-cells and plasmacytoid dendritic cells. Therefore, great efforts have been devoted to the advances of efficient delivery systems for CpG ODNs. In this review, we outline new horizons and recent developments in this field, providing a comprehensive summary of the nanoparticle-based CpG delivery systems developed to improve the efficacy of CpG-mediated immune responses, including DNA nanostructures, inorganic nanoparticles, polymer nanoparticles, metal-organic-frameworks, lipid-based nanosystems, proteins and peptides, as well as exosomes and cell membrane nanoparticles. Moreover, future challenges in the establishment of CpG delivery systems for immunotherapeutic applications are discussed. We expect that the continuously growing interest in the development of CpG-based immunotherapy will certainly fuel the excitement and stimulation in medicine research.

Nanovaccines Fostering Tertiary Lymphoid Structure to Attack Mimicry Nasopharyngeal Carcinoma

Tertiary lymphoid structures (TLSs) are formed in inflamed tissues, and recent studies demonstrated that the appearance of TLSs in tumor sites is associated with a good prognosis for tumor patients. However, the process of natural TLSs' formation was slow and uncontrollable. Herein, we developed a nanovaccine consisting of Epstein-Barr virus nuclear antigen 1 (EBNA1) and a bi-adjuvant of Mn²⁺ and cytosine-phosphate-guanine (CpG) formulated with tannic acid that significantly inhibited the development of mimicry nasopharyngeal carcinoma by fostering TLS formation. The nanovaccine activated LT-α and LT-β pathways, subsequently enhancing the expression of downstream chemokines, CCL19/CCL21, CXCL10 and CXCL13, in the tumor microenvironment. In turn, normalized blood and lymph vessels were detected in the tumor tissues of the nanovaccine group, correlated with increased infiltration of lymphocytes. Especially, the proportion of the B220⁺ CD8⁺ T, which was produced via trogocytosis between T and B cells during activation of T cells, was increased in tumors of the nanovaccine group. Furthermore, the intratumoral effector memory T cells (Tem), CD45⁺, CD3⁺, CD8⁺, CD44⁺, and CD62L^-, did not decrease after blocking the egress of T cells from tumor-draining lymph nodes by FTY-720. These results demonstrated that the nanovaccine can foster TLS formation, which thus enhances local immune responses significantly, delays tumor outgrowth, and prolongs the median survival time of murine models of mimicry nasopharyngeal carcinoma, demonstrating a promising strategy for nanovaccine development.

Heterologous administration of HPV16 E7 epitope-loaded nanocomplexes inhibits tumor growth in mouse model

The nanostructured complexes can result in enhanced vaccine efficacy by facilitating the distribution and uptake of antigens by antigen-presenting cells (APCs), thereby stimulating immune responses. Here, we hypothesized that either directly coating of nanoadjuvants including aluminum phosphate (AlPO₄) and adenovirus (Ad) with a modified HPV16 E7 MHC-I specific epitope, RAHYNIVTF_49-57, or mixing the CpG oligodeoxynucleotide (CpG-ODN) with the cationic epitope to form nanocomlexes, and their combinational therapy would enhance their anti-tumor effects in a TC-1 mouse model. The positively-charged HPV16 E7 epitope was attracted to the oppositely-charged adjuvants by electrostatic interaction to generate epitope/adjuvant nanocomplexes. We showed that coating the nanosized adjuvants with the cationic epitope increased the particles' surface charge without significant change in their size. We then tested the cellular immunogenicity and therapeutic efficacy of nanocomplexes by measuring IL-10 and IFN-γ production, the expression of CD107a as a marker of CTL response, and tumor growth inhibition. The nanocomplexes were administered either in homologous or heterologous prime-boost regimens, and heterologous immunizations including Ad/Pep-CpG/Pep, CpG/Pep-Ad/Pep, Ad/Pep-Alum/Pep, and Alum/Pep-Ad/Pep induced significantly higher levels of IL-10, IFN-γ, and CD107a-expressing CD8 T cells compared with homologous administrations. Furthermore, the tumor growth was significantly suppressed in mice receiving nanostructured complexes in the heterologous immunizations. Our study highlights the potential of the heterologous prime-boost administration of the epitope-coated nanostructures as an effective immunization strategy.

Discrepant antitumor efficacies of three CpG oligodeoxynucleotide classes in monotherapy and co-therapy with PD-1 blockade

Unmethylated CpG oligodeoxynucleotides (ODNs) activate plasmacytoid dendritic cells (pDCs) and B cells to induce humoral and cellular immunity, and are under development for the treatment of multiple cancers. However, the specific differences in antitumor effects among the three CpG ODN classes when administered as a monotherapy or in co-therapy with the anti-PD-1 antibody are unclear. We compared the immunostimulatory effects in vitro and antitumor effects in a CT26 subcutaneous mouse tumor model among the three CpG ODN classes. We found that CpG-A slightly suppressed tumor growth but possessed no synergistic antitumor effects with the anti-PD-1 antibody. CpG-B at low doses significantly inhibited tumor growth and possessed synergistic antitumor effects with the anti-PD-1 antibody. A high dose of CpG-C was required to achieve antitumor effects comparable to those of CpG-B, which was consistent with the immunostimulatory effects in B-cell proliferation and TLR9-NF-κB activation. Importantly, CpG-C in combination with anti-PD-1 antibody inhibited tumor growth more quickly and effectively than CpG-B because CpG-B significantly upregulated PD-L1 expression on multiple host immune cells to promote tumor immune escape. Moreover, co-therapy increased the infiltration of effector memory T cells. In summary, CpG-B and CpG-C with different optimal concentrations possessed strong antitumor effects, while CpG-C was more rapid and effective for co-therapy with the anti-PD-1 antibody.

Stimulation Effects and Mechanisms of Different Adjuvants on a Norovirus P Particle-Based Active Amyloid-β Vaccine

BACKGROUND

Adjuvants are important components of vaccines and effectively enhance the immune response of specific antigens. However, the role of adjuvants or combinations of adjuvants in stimulating immunogenicity of the amyloid-β (Aβ) vaccine, as well as molecular mechanisms underlying such stimulation still remain unclear. A previous study of ours developed a norovirus P particle-based active Aβ epitope vaccine, PP-3copy-Aβ1-6-loop123, which stimulates a high titer of Aβ-specific antibodies in mouse Alzheimer's disease (AD) models.

OBJECTIVE

The most effective and safe adjuvant that maximizes the immunogenicity of our protein vaccine was determined.

METHODS

We investigated four adjuvants (CpG, AS02, AS03, and MF59), and combinations of those, for capacity to enhance immunogenicity, and performed transcriptome analysis to explore mechanisms underlying the role of these in AD immunotherapy.

RESULTS

Addition of the adjuvant, AS02, remarkably improved the immunogenicity of the PP-3copy-Aβ1-6-loop123 vaccine without triggering an Aβ-specific T-cell response. Combinations of adjuvants, particularly CpG +  AS02 and CpG + AS03, elicited a significantly elevated and prolonged Aβ-specific antibody response. Gene ontology and Kyoto Encyclopedia of Genes and Genomes analyses indicated that a combination of two adjuvants was more effective in activating immune-related pathways, thereby enhancing the immunogenicity of PP-3copy-Aβ1-6-loop123.

CONCLUSION

These findings demonstrated that adjuvants can be used as enhancers in AD protein vaccination, and that a combination of CpG and AS-related adjuvants may be a very effective adjuvant candidate suitable for further clinical trials of the PP-3copy-Aβ1-6-loop123 vaccine. Our studies also revealed potential mechanisms underlying the stimulation of immune response of protein vaccines by adjuvants.

A Novel C Type CpG Oligodeoxynucleotide Exhibits Immunostimulatory Activity In Vitro and Enhances Antitumor Effect In Vivo

Background

C type CpG oligodeoxynucleotides (CpG-C ODNs), possessing the features of both A type and B type CpG ODNs, exert a variety of immunostimulatory activities and have been demonstrated as an effective antitumor immunotherapy. Based on the structural characteristics, we designed 20 potential ODNs with the aim of synthesizing an optimal, novel CpG-C ODN specific to human and murine Toll-like receptor 9 (TLR9). We also sought to investigate the in vitro immunostimulatory and in vivo antitumor effects of the novel CpG-C ODN.

Methods

Twenty potential CpG-C ODNs were screened for their ability to secrete interferon (IFN)-α, and interleukin (IL)-6 and tumor necrosis factor (TNF)-α production for the three most promising sequences were assayed in human peripheral blood mononuclear cells (PBMCs) by enzyme-linked immunosorbent assay (ELISA) or cytometric bead array assay. The functions of human and mouse B cells, and cytokine production in mice induced by the most promising sequence, HP06T07, were determined by flow cytometry and ELISA. Growth and morphology of tumor tissues in in vivo murine models inoculated with CT26 cells were analyzed by a growth inhibition assay and immunohistochemistry, respectively.

Results

Among the 20 designed ODNs, HP06T07 significantly induced IFN-α, IL-6, and TNF-α secretion, and promoted B-cell activation and proliferation in a dose-dependent manner in human PBMCs and mouse splenocytes in vitro. Intratumoral injection of HP06T07 notably suppressed tumor growth and prolonged survival in the CT26 subcutaneous mouse model in a dose-dependent manner. HP06T07 administered nine times at 2-day intervals (I2) eradicated tumor growth at both primary and distant sites of CT26 tumors. HP06T07 restrained tumor growth by increasing the infiltration of T cells, NK cells, and plasmacytoid dendritic cells (pDCs).

Conclusions

HP06T07, a novel CpG-C ODN, shows potent immunostimulatory activity in vitro and suppresses tumor growth in the CT26 subcutaneous mouse model.

Targeting Cellular and Tissue HIV Reservoirs With Toll-Like Receptor Agonists

The elimination of both cellular and tissue latent reservoirs is a challenge toward a successful HIV cure. "Shock and Kill" are among the therapeutic strategies that have been more extensively studied to target these reservoirs. These strategies are aimed toward the reactivation of the latent reservoir using a latency-reversal agent (LRA) with the subsequent killing of the reactivated cell either by the cytotoxic arm of the immune system, including NK and CD8 T cells, or by viral cytopathic mechanisms. Numerous LRAs are currently being investigated in vitro, ex vivo as well as in vivo for their ability to reactivate and reduce latent reservoirs. Among those, several toll-like receptor (TLR) agonists have been shown to reactivate latent HIV. In humans, there are 10 TLRs that recognize different pathogen-associated molecular patterns. TLRs are present in several cell types, including CD4 T cells, the cell compartment that harbors the majority of the latent reservoir. Besides their ability to reactivate latent HIV, TLR agonists also increase immune activation and promote an antiviral response. These combined properties make TLR agonists unique among the different LRAs characterized to date. Additionally, some of these agonists have shown promise toward finding an HIV cure in animal models. When in combination with broadly neutralizing antibodies, TLR-7 agonists have shown to impact the SIV latent reservoir and delay viral rebound. Moreover, there are FDA-approved TLR agonists that are currently being investigated for cancer therapy and other diseases. All these has prompted clinical trials using TLR agonists either alone or in combination toward HIV eradication approaches. In this review, we provide an extensive characterization of the state-of-the-art of the use of TLR agonists toward HIV eradication strategies and the mechanism behind how TLR agonists target both cellular and tissue HIV reservoirs.

A Built-In CpG Adjuvant in RSV F Protein DNA Vaccine Drives a Th1 Polarized and Enhanced Protective Immune Response

Human respiratory syncytial virus (RSV) is the most significant cause of acute lower respiratory infection in children. However, there is no licensed vaccine available. Here, we investigated the effect of five or 20 copies of C-Class of CpG ODN (CpG-C) motif incorporated into a plasmid DNA vaccine encoding RSV fusion (F) glycoprotein on the vaccine-induced immune response. The addition of CpG-C motif enhanced serum binding and virus-neutralizing antibody responses in BALB/c mice immunized with the DNA vaccines. Moreover, mice vaccinated with CpG-modified vaccines, especially with the higher 20 copies, resulted in an enhanced shift toward a Th1-biased antibody and T-cell response, a decrease in pulmonary pathology and virus replication, and a decrease in weight loss after RSV challenge. This study suggests that CpG-C motif, cloned into the backbone of DNA vaccine encoding RSV F glycoprotein, functions as a built-in adjuvant capable of improving the efficacy of DNA vaccine against RSV infection.

Generation of human MHC (HLA-A11/DR1) transgenic mice for vaccine evaluation

The rapid occurrence of emerging infectious diseases demonstrates an urgent need for a new preclinical experimental model that reliably replicates human immune responses. Here, a new homozygous humanized human leukocyte antigen (HLA)-A11/DR1 transgenic mouse (HLA-A11(+/+)/DR01(+/+)/H-2-β2m(-/-)/IAβ(-/-)) was generated by crossing HLA-A11 transgenic (Tg) mice with HLA-A2(+/+)/DR01(+/+)/H-2-β2m(-/-)/IAβ(-/-) mice. The HLA-A11-restricted immune response of this mouse model was then examined. HLA-A11 Tg mice expressing a chimeric major histocompatibility complex (MHC) molecule comprising the α1, α2, and β2m domains of human HLA-A11 and the α3 transmembrane and cytoplasmic domains of murine H-2D(b) were generated. The correct integration of HLA-A11 and HLA-DR1 into the genome of the HLA-A11/DR1 Tg mice (which lacked the expression of endogenous H-2-I/II molecules) was then confirmed. Immunizing mice with a recombinant HBV vaccine or a recombinant HIV-1 protein resulted in the generation of IFN-γ-producing cytotoxic T lymphocyte (CTL) and antigen-specific antibodies. The HLA-A11-restricted CTL response was directed at HLA immunodominant epitopes. These mice represent a versatile animal model for studying the immunogenicity of HLA CTL epitopes in the absence of a murine MHC response. The established animal model will also be useful for evaluating and optimizing T cell-based vaccines and for studying differences in antigen processing between mice and humans.

CpG oligodeoxynucleotides with crude parasite antigens reduce worm recovery in Opisthorchis viverrini infected hamsters

Opisthorchis viverrini, a human liver fluke, is still an endemic parasitic infection in Thailand and nearly all countries in Southeast Asia. O. viverrini induces a chronic stage of infection in hamsters. During the first 2 weeks of infection, Th1 inducing cytokine, IL-12, increased but was down regulated in chronic infection. In this study it was found that unmethylated-CpG ODN (oligodeoxynucleotides) 1826 increased hamster mononuclear cell proliferation and stimulated IFN-γ production in vitro. The IFN-γ levels in hamster sera were significantly increased in hamsters injected with CpG ODN 1826 alone or plus crude somatic antigens (CSAg). Further investigation using the flow cytometer found that CD4⁺T cells and IFN-γ⁺ CD4⁺T cells (Th1-like cells) in the hamster blood were significantly increased. The role of these cells in the protective responses in hamsters was evaluated by challenging with 25 metacercaria and observation for 3 months. The number of worms recovered was significantly reduced in the hamsters injected with CpG ODN 1826 with CSAg, but not in CpG ODN 1826 alone groups when compared to PBS control. The percent of reduction in hamsters against this parasite were 32.95% and 21.49% in the CpG ODN 1826 with CSAg and CpG ODN 1826 alone. This study indicates that CpG ODN 1826 plus parasite antigens elicit a Th1-like response that leads to the enhancement of worm reduction.

Immunomodulatory nanoparticles ameliorate disease in the Leishmania (Viannia) panamensis mouse model

Leishmania (Viannia) panamensis (L. (V.) panamensis) is a species of protozoan parasites that causes New World leishmaniasis, which is characterized by a hyper-inflammatory response. Current treatment strategies, mainly chemotherapeutic, are suboptimal due to adverse effects, long treatment regimens, and increasing drug resistance. Recently, immunotherapeutic approaches have shown promise in preclinical studies of leishmaniasis. As NPs may enable broad cellular immunomodulation through internalization in phagocytic and antigen-presenting cells, we tested the therapeutic efficacy of biodegradable NPs encapsulating a pathogen-associated molecular pattern (PAMP), CpG-rich oligonucleotide (CpG; NP-CpG), in mice infected with L. (V.) panamensis. NP-CpG treatment reduced lesion size and parasite burden, while neither free CpG nor empty NP showed therapeutic effects. NP-encapsulation led to CpG persistence at the site of infection along with an unexpected preferential cellular uptake by myeloid derived suppressor cells (MDSCs; CD11b(+)Ly6G(+)Ly6C(-)) as well as CD19(+) dendritic cells. This corresponded with the suppression of the ongoing immune response measured by the reduction of pathogenic cytokines IL-10 and IL-13, as well as IL-17 and IFNγ, in comparison to other treatment groups. As chronic inflammation is generally associated with the accumulation of MDSCs, this study may enable the rational design of cost-effective, safe, and scalable delivery systems for the treatment of inflammation-mediated diseases.

Antibody responses induced by recombinant ALV-A gp85 protein vaccine combining with CpG-ODN adjuvant in breeder hens and the protection for their offspring against early infection

To observe the antibody responses induced by recombinant A subgroup avian leukosis virus (ALV-A) gp85 protein vaccine plus CpG-ODN adjuvant and the protection of maternal antibodies (MAbs) for the hatched chickens against early infection, the gp85 gene was amplified from the proviral cDNA of ALV-A-SDAU09C1 strain using PCR and the recombinant plasmid containing target gene was constructed and expressed in EscherichiaColi. The expressed product was confirmed using SDS-PAGE and western blot that it is about 46KD of recombinant protein. The purified recombinant proteins combining with CpG-ODN adjuvant or Freund's adjuvant were inoculated into the breeder hens, the ALV-A antibodies in serum and in egg-yolk were detected; the fertilized eggs from the vaccinated hens with different titers of egg-yolk antibody were hatched and then challenged with 10(4.2)/0.1mL TCID50 of ALV-A-SDAU09C1 strain, all the hatched chickens were weekly detected for the viremias and the cloacal swab P27 antigen and pathological lesions; the neutralizing test of antisera in vitro was conducted. The results showed that the recombinant gp85 proteins combining with CpG-ODN adjuvant could induce the breeder hens to produce better antibody responses than gp85 protein with Freund's adjuvant or without adjuvant; the MAbs with higher titers induced by CpG-ODN+gp85 proteins could obviously decrease the ratios of viremias (13% vs 33%), cloacal detoxification (20% vs 67%) and death (0% vs 22%) caused by ALV-A infection than those by gp85 protein without adjuvant. The results of the neutralizing test indicated that the antisera from the hatched chickens could neutralize the ALV-A-SDAU09C1 strain in vitro, but which depends on the antibody titers. The results of IFA confirmed that the serum antibody could combine with the ALV in DF1 cells. It can be concluded that the prepared ALV-A gp85 subunit vaccine combining with CpG-ODN adjuvant could induce the breeder hens to produce better neutralizing antibody responses and protect 80% of their offspring chickens against early infection.

Design and Structural Requirements of the Potent and Safe TLR-9 Agonistic Immunomodulator MGN1703

Single-stranded oligodeoxynucleotides (ODN), containing nonmethylated cytosine–guanine motifs (CpG ODN), are recognized by the innate immune system as “danger signals.” CpG ODN are efficacious immunomodulators but require phosphorothioate (PT) or other backbone modifications for metabolic stability, which cause toxicities in mice and primates. We therefore designed a covalently closed DNA molecule (dSLIM^®) where two single-stranded loops containing CG motifs are connected through a double-stranded stem in the absence of any nonnatural DNA component. The most promising immunomodulator, MGN1703, comprises two loops of 30 nucleotides containing three CG motifs each, and a connecting stem stem of 28 base pairs. MGN1703 stimulates cytokine secretion [interferon (IFN)-α, IFN-γ, interleukin (IL)-12, IL-6, and IL-2] and activates immune cells by increased expression of CD80, CD40, human leukocyte antigen (HLA)-DR and ICAM-1. Efficacy of immunomodulation strictly depends on the descriptive dumbbell shape and size of the molecule. Variations in stem length and loop size lead to reduced potency of the respective members of the dSLIM^® class. In a representative mouse model, toxicities from injections of high amounts of a CpG ODN-PT and of MGN1703 were evaluated. The CpG ODN-PT group showed severe organ damage, whereas no such or other pathologies were found in the MGN1703 group. Oncological clinical trials of MGN1703 already confirmed our design.

MGN1703, an immunomodulator and toll-like receptor 9 (TLR-9) agonist: from bench to bedside

The adaptive immune system has been the main focus of immunological strategies in oncology with only more recent approaches targeting innate immunity. Endosomal toll-like receptors (TLR-7, TLR-9) activate innate immune responses by signaling damage-associated molecular patterns (DAMP) from decaying tumor cells. This has led to the development of DNA-based TLR-9 agonists, which induce antitumor activity through innate and subsequent adaptive immune responses. Early clinical trials with CpG-ODN as TLR-9 agonists were associated with unfavorable tolerability and narrow clinical efficacy, leading to failure in pivotal trials. dSLIM, the active ingredient of MGN1703, is a DNA-based, radically different molecular alternative to CpG-ODN, which results in genuine antitumor immunomodulation. Preclinical and clinical studies of MGN1703 have confirmed that this TLR-9 agonist has therapeutic potential in a variety of solid tumors, while long-term treatment with high doses was very well tolerated. A pivotal trial of first-line maintenance treatment with MGN1703 in patients with metastatic colorectal cancer is underway.

Combinations of various CpG motifs cloned into plasmid backbone modulate and enhance protective immunity of viral replicon DNA anthrax vaccines

DNA vaccines are generally weak stimulators of the immune system. Fortunately, their efficacy can be improved using a viral replicon vector or by the addition of immunostimulatory CpG motifs, although the design of these engineered DNA vectors requires optimization. Our results clearly suggest that multiple copies of three types of CpG motifs or combinations of various types of CpG motifs cloned into a viral replicon vector backbone with strong immunostimulatory activities on human PBMC are efficient adjuvants for these DNA vaccines to modulate and enhance protective immunity against anthrax, although modifications with these different CpG forms in vivo elicited inconsistent immune response profiles. Modification with more copies of CpG motifs elicited more potent adjuvant effects leading to the generation of enhanced immunity, which indicated a CpG motif dose-dependent enhancement of antigen-specific immune responses. Notably, the enhanced and/or synchronous adjuvant effects were observed in modification with combinations of two different types of CpG motifs, which provides not only a contribution to the knowledge base on the adjuvant activities of CpG motifs combinations but also implications for the rational design of optimal DNA vaccines with combinations of CpG motifs as "built-in" adjuvants. We describe an efficient strategy to design and optimize DNA vaccines by the addition of combined immunostimulatory CpG motifs in a viral replicon DNA plasmid to produce strong immune responses, which indicates that the CpG-modified viral replicon DNA plasmid may be desirable for use as vector of DNA vaccines.

CpG oligodeoxynucleotide protect neonatal piglets from challenge with the enterotoxigenic E. coli

CpG motifs activates mammalian lymphocytes and macrophages to produce cytokines and polyclonal Ig. These include IFN-γ, IL-12, TNF-a, which are important in the control of bacterial infection. But thus far, the innate immunostimulatory effects of CpG ODN against pathogen have been established mainly in mouse, monkey, sheep, chicken, but not in neonatal piglets. The purpose of this study is to determine the potential protection of CpG ODN against enterotoxigenic Escherichia coli (ETEC) (with which neonatal piglets were susceptible to infection in our lab) in neonatal piglets. Here, we show intranasal (IN)-mucosal and intramuscularly (IM) systemic administration of CpG ODN could enhance innate cellular (cytokine) immunity in the sera and intestine mucosa post challenge, and thereafter the development of antigen-specific antibodies in piglets. IN and IM immunizations of neonatal piglets without antigen both reduced the ETEC excretion and alleviated diarrhoea symptoms upon challenge, and IN route had better protection effects than IM route. Protection in this study was linked to induction of a Th1 response which induced by CpG ODN. Co-delivery with Emulsigen (EM), could improve protection mediated by CpG ODN. These observations indicate that IN administration of 100 μg/kg CpG ODN with 20% EM codelivery may represent a valuable strategy for induction of innate immunity against ETEC infection in neonatal piglets.

Topical CpG adjuvantation of a protein-based vaccine induces protective immunity to Listeria monocytogenes

Robust CD8(+) T cell responses are essential for immune protection against intracellular pathogens. Using parenteral administration of ovalbumin (OVA) protein as a model antigen, the effect of the Toll-like receptor 9 (TLR9) agonist, CpG oligodeoxynucleotide (ODN) 1826, as an adjuvant delivered either topically, subcutaneously, or intramuscularly on antigen-specific CD8(+) T cell responses in a mouse model was evaluated. Topical CpG adjuvant increased the frequency of OVA-specific CD8(+) T cells in the peripheral blood and in the spleen. The more effective strategy to administer topical CpG adjuvant to enhance CD8(+) T cell responses was single-dose administration at the time of antigen injection with a prime-boost regimen. Topical CpG adjuvant conferred both rapid and long-lasting protection against systemic challenge with recombinant Listeria monocytogenes expressing the cytotoxic T lymphocyte (CTL) epitope of OVA(257-264) (strain Lm-OVA) in a TLR9-dependent manner. Topical CpG adjuvant induced a higher proportion of CD8(+) effector memory T cells than parenteral administration of the adjuvant. Although traditional vaccination strategies involve coformulation of antigen and adjuvant, split administration using topical adjuvant is effective and has advantages of safety and flexibility. Split administration of topical CpG ODN 1826 with parenteral protein antigen is superior to other administration strategies in enhancing both acute and memory protective CD8(+) T cell immune responses to subcutaneous protein vaccines. This vaccination strategy induces rapid and persistent protective immune responses against the intracellular organism L. monocytogenes.

Maternal antibody induced by recombinant gp85 protein vaccine adjuvanted with CpG-ODN protects against ALV-J early infection in chickens

In this study, the efficacy of a recombinant protein vaccine encoding the gp85 gene from the subgroup J avian leukosis virus (ALV-J) co-administered with cytosine-phosphate-guanine oligodeoxynucleotide (CpG-ODN) or Freund's adjuvants was investigated for the protection against early ALV-J infection in chickens. The gp85 gene from ALV-J was amplified using polymerase chain reaction (PCR), and the recombinant protein was expressed in Escherichia coli. The purified recombinant protein was injected intramuscularly into the breeder hens along with CpG-ODN or Freund's adjuvants, and the antibodies in the serum were assayed regularly post inoculation. The fertilized eggs from the vaccinated hens were hatched, the hatched chickens were challenged with 10(2.2) 50% tissue culture infective dose (TCID50) ALV-J on 1 day, and the maternal antibodies in the hatched chickens were examined regularly before and after the challenge. The viremia was determined weekly, and a histopathological analysis of the immunosuppressive lesions was performed. The results suggest that the gp85 recombinant protein was successfully prepared and was inoculated with CpG-ODN adjuvant into breeder hens to induce serological antibody against ALV-J in the hens and in the hatched chickens. The positive maternal antibodies in the hatched chickens provided effective protection for most chickens against viremia and dramatically decreased the number of immunosuppressive lesions; these protective effects were better than those of the gp85 recombinant protein plus Freund's adjuvant. The data will provide a scientific basis for the application of the ALV-J subunit vaccine to control ALV-J infection in chicken flocks.

Epithelial toll-like receptor 9 signaling in colorectal inflammation and cancer: clinico-pathogenic aspects

Toll-like receptors (TLRs) recognize specific motifs which are frequently present in bacteria, fungi, prokaryotes and viruses. Amongst TLRs, TLR9 can be activated by such bacterial or viral DNA fragments, immunoglobulin-DNA complexes or synthetic oligonucleotides, which all contain unmethylated cytosine-guanine nucleotide sequences (CpGs). Emerging data indicate that TLR9 signaling has a role in, and may influence, colorectal carcinogenesis and colonic inflammation. CpGs are classified into three groups according to their influence on both the antigen-specific humoral- and cellular immunity, and the production of type 1 interferons and proinflammatory cytokines. TLR9 activation via CpGs may serve as a new therapeutic target for several cancerous and various inflammatory conditions. Due to its probable anti-cancer effects, the application possibilities of TLR9-signaling modulation may be extremely diverse even in colorectal tumors. In this review we aimed to summarize the current knowledge about TLR-signaling in the pathogenesis and therapy of inflammatory bowel diseases and colorectal cancer. Due to the species-specific differences in TLR9 expression, however, one must be careful in translating the animal model data into the human system, because of the differences between CpG-oligodeoxynucleotide-responsive cells. TLR9 agonist DNA-based immunomodulatory sequences could also represent a promising therapeutic alternative in systemic inflammatory conditions and chronic colonic inflammations as their side effects are not significant.

Monitoring Therapeutic Treatments against Burkholderia Infections Using Imaging Techniques

Burkholderia mallei, the etiologic agent of glanders, are Category B select agents with biothreat potential, and yet effective therapeutic treatments are lacking. In this study, we showed that CpG administration increased survival, demonstrating protection in the murine glanders model. Bacterial recovery from infected lungs, liver and spleen was significantly reduced in CpG-treated animals as compared with non-treated mice. Reciprocally, lungs of CpG-treated infected animals were infiltrated with higher levels of neutrophils and inflammatory monocytes, as compared to control animals. Employing the B. mallei bioluminescent strain CSM001 and the Neutrophil-Specific Fluorescent Imaging Agent, bacterial dissemination and neutrophil trafficking were monitored in real-time using multimodal in vivo whole body imaging techniques. CpG-treatment increased recruitment of neutrophils to the lungs and reduced bioluminescent bacteria, correlating with decreased bacterial burden and increased protection against acute murine glanders. Our results indicate that protection of CpG-treated animals was associated with recruitment of neutrophils prior to infection and demonstrated, for the first time, simultaneous real time in vivo imaging of neutrophils and bacteria. This study provides experimental evidence supporting the importance of incorporating optimized in vivo imaging methods to monitor disease progression and to evaluate the efficacy of therapeutic treatment during bacterial infections.

Three types of human CpG motifs differentially modulate and augment immunogenicity of nonviral and viral replicon DNA vaccines as built-in adjuvants

NakedDNA vaccines given by intramuscular injection are efficient in mouse models, but they require improvement for human use. As the immunogenicity of DNA vaccines depends, to a large extent, on the presence of CpG motifs as built-in adjuvants, we addressed this issue by inserting three types of human CpG motifs (A-type, B-type, and C-type) into the backbone of nonviral DNA and viral DNA replicon vectors with distinct immunostimulatory activities on human PBMCs. The adjuvant effects of CpG modifications in DNA vaccines expressing three types of antigens (β-Gal, AHc, or PA4) were then characterized in mice and found to significantly enhance antigen-specific humoral and cell-mediated immune responses. The three types of CpG motifs also differentially affected and modulated immune responses and protective potency against botulinum neurotoxin serotype A and Bacillus anthracis A16R challenge. Taken together, these results demonstrate that insertion of human CpG motifs can differentially modulate the immunogenicity of nonviral DNA vaccines as well as viral DNA replicon vaccines. Our study provides not only a better understanding of the in vivo activities of CpG motif adjuvants but implications for the rational design of such motifs as built-in adjuvants for DNA vectors targeting specific antigens.