APC stimulated by CpG oligodeoxynucleotide enhance activation of MHC class I-restricted T cells

Mussel Adhesive-Inspired Proteomimetic Polymer

Herein, a synthetic polymer proteomimetic is described that reconstitutes the key structural elements and function of mussel adhesive protein. The proteomimetic was prepared via graft-through ring-opening metathesis polymerization of a norbornenyl-peptide monomer. The peptide was derived from the natural underwater glue produced by marine mussels that is composed of a highly repetitive 10 amino acid tandem repeat sequence. The hypothesis was that recapitulation of the repeating unit in this manner would provide a facile route to a nature-inspired adhesive. To this end, the material, in which the arrangement of peptide units was as side chains on a brush polymer rather than in a linear fashion as in the natural protein, was examined and compared to the native protein. Mechanical measurements of adhesion forces between solid surfaces revealed improved adhesion properties over the natural protein, making this strategy attractive for diverse applications. One such application is demonstrated, using the polymers as a surface adhesive for the immobilization of live cells.

Optimized Gemcitabine Therapy in Combination with E7 Peptide Immunization Elicits Tumor Cure by Preventing Ag-Specific CTL Inhibition in Animals with Large Established Tumors

The role of chemotherapeutic agents in tumor immunotherapy is still controversial. In this study, we test using a TC-1 tumor model whether gemcitabine plus E7 peptide vaccine regimens (E7 peptides+CpG-ODN+anti-4-1BB Abs) may result in tumor cure in mice with large established tumors, with a focus on their effects on Ag-specific cytotoxic T lymphocyte (CTL) and myeloid-derived suppressor cell levels. Gemcitabine inhibited tumor growth by its direct cytotoxicity to tumor cells in vivo. E7 peptide vaccine regimens enhanced Ag-specific CTL lytic and antitumor therapeutic activity. Initial combination therapy using gemcitabine and E7 peptide vaccine regimens resulted in tumor regression with tumor relapse in animals with large established tumors, which appeared to result from the suppression of Ag-specific CTL activity by gemcitabine treatment. However, optimization of gemcitabine therapy by reducing its dose and frequency led to complete tumor regression without any recurring tumors in all tested mice even after discontinuation of therapy, possibly due to Ag-specific CTL responses. Thus, this study shows that the optimal dose and therapy frequency of gemcitabine are critical for achieving tumor cure in tumor-bearing animals undergoing E7 peptide vaccine regimen therapy, mainly by preventing CTL suppression. These findings may have implications for designing peptide-based therapeutic vaccines in cancer patients undergoing chemotherapy.

CpG Oligodeoxynucleotide Inhibits Cockroach-Induced Asthma via Induction of IFN-γ⁺ Th1 Cells or Foxp3⁺ Regulatory T Cells in the Lung

Purpose

CpG oligodeoxynucleotide (CpG-ODN), a TLR9 agonist, activates innate immunity and induces Th1 response. Although the immune modulatory effect of CpG-ODN has been extensively studied, its function in cockroach extract-induced allergic asthma has not been studied. Here, we investigated the inhibitory function of CpG-ODN in cockroach extract-induced asthma in mice with different treatment schemes.

Methods

Scheme 1: BALB/C mice were intra-nasally co-administered by cockroach extract and CpG-ODN twice a week for 3 weeks; Scheme 2: The mice were intra-nasally pre-treated with CpG-ODN at day 0 and cockroach allergen challenge was performed from day 3 as in scheme 1. Scheme 3: Cockroach allergen challenge was performed as in scheme 1 and CpG-ODN was post-treated at day 21. Then, BAL cell count, flow cytometric analysis of alveolar macrophages, regulatory T cells, and lung tissue histology, Th1 and Th2 cytokines, serum IgE, cockroach specific IgE, IgG1/IgG2a ratio, and airway hyper-responsiveness were evaluated.

Results

Mice with repeated intra-nasal exposure to CpG-ODN showed a dramatic decrease in eosinophilic inflammation, goblet cell hyperplasia, and airway hyper-responsiveness with reduction of IL-13, IL-5, and serum IgE, cockroach specific IgE and IgG1/IgG2a ratio. This inhibitory function might be related to the up-regulation of IL-10 and CD4⁺Foxp3⁺ regulatory T cells in the lung. Interestingly, one-time challenge of CpG-ODN either prior or posterior to cockroach extract exposure could modulate airway inflammation and hyper-responsiveness via increase of Th1 response.

Conclusions

Collectively, our data suggest that CpG-ODN treatment modulates Th2 inflammation in the lung by induction of regulatory T cells or Th1 response in a cockroach-induced asthma model.

Enhanced mucosal immune responses induced by a combined candidate mucosal vaccine based on Hepatitis A virus and Hepatitis E virus structural proteins linked to tuftsin

Hepatitis A virus (HAV) and Hepatitis E virus (HEV) are the most common causes of infectious hepatitis. These viruses are spread largely by the fecal-oral route and lead to clinically important disease in developing countries. To evaluate the potential of targeting hepatitis A and E infection simultaneously, a combined mucosal candidate vaccine was developed with the partial open reading frame 2 (ORF2) sequence (aa 368–607) of HEV (HE-ORF2) and partial virus protein 1 (VP1) sequence (aa 1–198) of HAV (HA-VP1), which included the viral neutralization epitopes. Tuftsin is an immunostimulatory peptide which can enhance the immunogenicity of a protein by targeting it to macrophages and dendritic cells. Here, we developed a novel combined protein vaccine by conjugating tuftsin to HE-ORF2 and HA-VP1 and used synthetic CpG oligodeoxynucleotides (ODNs) as the adjuvant. Subsequent experiments in BALB/c mice demonstrated that tuftsin enhanced the serum-specific IgG and IgA antibodies against HEV and HAV at the intestinal, vaginal and pulmonary interface when delivered intranasally. Moreover, mice from the intranasally immunized tuftsin group (HE-ORF2-tuftsin + HA-VP1-tuftsin + CpG) showed higher levels of IFN-γ-secreting splenocytes (Th1 response) and ratio of CD4⁺/CD8⁺ T cells than those of the no-tuftsin group (HE-ORF2 + HA-VP1 + CpG). Thus, the tuftsin group generated stronger humoral and cellular immune responses compared with the no-tuftsin group. Moreover, enhanced responses to the combined protein vaccine were obtained by intranasal immunization compared with intramuscular injection. By integrating HE-ORF2, HA-VP1 and tuftsin in a vaccine, this study validated an important concept for further development of a combined mucosal vaccine against hepatitis A and E infection.

Combined stimulation of TLR9 and 4.1BB augments Trp2 peptide vaccine-mediated melanoma rejection by increasing Ag-specific CTL activity and infiltration into tumor sites

Peptide vaccines are a clinically applicable therapy shown to be effective in tumor control. In this study, Trp2 peptides plus CpG-oligodeoxynucleotide treatment was found to induce Ag-specific IFN-γ and CD8+CTL responses, and antitumor activity against large established melanoma (tumor size, 7mm). A combination of anti-4.1BB antibodies with Trp2 peptides+CpG-oligodeoxynucleotide increased the antitumor cure rate from 0% to 75%. This effect was concomitant with greater induction of Ag-specific CD8+CTLs and their infiltration into the tumor sites, highlighting the importance of combined stimulation of TLR9 and 4.1BB for achieving tumor eradication. These findings may have implications for designing peptide-based therapeutic vaccines for cancer-patients.

CXCL10 is critical for the generation of protective CD8 T cell response induced by antigen pulsed CpG-ODN activated dendritic cells

The visceral form of leishmaniasis is the most severe form of the disease and of particular concern due to the emerging problem of HIV/visceral leishmaniasis (VL) co-infection in the tropics. Till date miltefosine, amphotericin B and pentavalent antimony compounds remain the main treatment regimens for leishmaniasis. However, because of severe side effects, there is an urgent need for alternative improved therapies to combat this dreaded disease. In the present study, we have used the murine model of leishmaniasis to evaluate the potential role played by soluble leishmanial antigen (SLA) pulsed-CpG-ODN stimulated dendritic cells (SLA-CpG-DCs) in restricting the intracellular leishmanial growth. We found that mice vaccinated with a single dose of SLA-pulsed DC stimulated by CpG-ODN were protected against a subsequent leishmanial challenge and had a dramatic reduction in parasite burden along with the generation of parasite specific cytotoxic T lymphocytes. Moreover, we demonstrate that the induction of protective immunity conferred by SLA-CpG-DCs depends entirely on the CXC chemokine IFN-γ-inducible protein 10 (CXCL10; IP-10). CXCL10 is directly involved in the generation of a parasite specific CD8⁺ T cell-mediated immune response. We observed significant reduction of CD8⁺ T cells in mice depleted of CXCL10 suggesting a direct role of CXCL10 in the generation of CD8⁺ T cells in SLA-CpG-DCs vaccinated mice. CXCL10 also contributed towards the generation of perforin and granzyme B, two important cytolytic mediators of CD8⁺ T cells, following SLA-CpG-DCs vaccination. Together, these findings strongly demonstrate that CXCL10 is critical for rendering a protective cellular immunity during SLA-CpG-DC vaccination that confers protection against Leishmania donovani infection.

Self-assembling CpG DNA nanoparticles for efficient antigen delivery and immunostimulation

DNA containing unmethylated deoxycytidylyl-deoxyguanosine (CpG) dinucleotides (CpG DNA) is a potent stimulator of immune responses through triggering of Toll-like receptor 9 (TLR9). In the present study, we synthesized cholesterol-modified CpG oligodeoxynucleotide (Chol-CpG ODN) and investigated its ability to form nanoparticles by self-assembling, then examined their immunostimulatory activity and potency to deliver antigens to antigen presenting cells (APCs). Chol-CpG ODN spontaneously formed particles in aqueous solutions. Cholesterol modification increased the stability of ODN in serum. Chol-CpG ODN was efficiently taken up by mouse macrophage-like RAW264.7 cells and induced a large amount of tumor necrosis factor-α compared with unmodified CpG ODN. Then, ovalbumin (OVA), a model antigen, was incorporated into Chol-CpG ODN nanoparticles. Cholesterol-modified GpC ODN (Chol-GpC ODN) was used to assess the importance of CpG motif on the antigen-specific immune response. Vaccination of mice with OVA/Chol-CpG ODN induced high level interferon-γ production from splenocytes. Furthermore, a high serum level of OVA-specific immunoglobulin G2a was observed in mice receiving OVA/Chol-CpG ODN. Neither CpG ODN nor Chol-GpC ODN was effective at all. These results indicate that self-assembling nanoparticles of Chol-CpG ODN are effective for inducing antigen-specific immune responses because of the high immunostimulatory activity, ability to incorporate antigens and tropism to APCs.

The role of innate immune-stimulated epithelial apoptosis during gastrointestinal inflammatory diseases

The maintenance of mucosal barrier equilibrium in the intestine requires a delicate and dynamic balance between enterocyte loss by apoptosis and the generation of new cells by proliferation from stem cell precursors at the base of the intestinal crypts. When the balance shifts towards either excessive or insufficient apoptosis, a broad range of gastrointestinal diseases can manifest. Recent work from a variety of laboratories has provided evidence in support of a role for receptors of the innate immune system, including Toll-like receptors 2, 4, and 9 as well as the intracellular pathogen recognition receptor NOD2/CARD15, in the initiation of enterocyte apoptosis. The subsequent induction of enterocyte apoptosis in response to the activation of these innate immune receptors plays a key role in the development of various intestinal diseases, including necrotizing enterocolitis, Crohn's disease, ulcerative colitis, and intestinal cancer. This review will detail the regulatory pathways that govern enterocyte apoptosis, and will explore the role of the innate immune system in the induction of enterocyte apoptosis in gastrointestinal disease.

Tumor immunotherapy using adenovirus vaccines in combination with intratumoral doses of CpG ODN

The combination of viral vaccination with intratumoral (IT) administration of CpG ODNs is yet to be investigated as an immunotherapeutic treatment for solid tumors. Here, we show that such a treatment regime can benefit survival of tumor-challenged mice. C57BL/6 mice bearing ovalbumin (OVA)-expressing EG.7 thymoma tumors were therapeutically vaccinated with adenovirus type 5 encoding OVA (Ad5-OVA), and the tumors subsequently injected with the immunostimulatory TLR9 agonist, CpG-B ODN 1826 (CpG), 4, 7, 10, and 13 days later. This therapeutic combination resulted in enhanced mean survival times that were more than 3.5× longer than naïve mice, and greater than 40% of mice were cured and capable of resisting subsequent tumor challenge. This suggests that an adaptive immune response was generated. Both Ad5-OVA and Ad5-OVA + CpG IT treatments led to significantly increased levels of H-2 K(b)-OVA-specific CD8+ lymphocytes in the peripheral blood and intratumorally. Lymphocyte depletion studies performed in vivo implicated both NK cells and CD8+ lymphocytes as co-contributors to the therapeutic effect. Analysis of tumor infiltrating lymphocytes (TILs) on day 12 post-tumor challenge revealed that mice treated with Ad5-OVA + CpG IT possessed a significantly reduced percentage of regulatory T lymphocytes (Tregs) within the CD4+ lymphocyte population, compared with TILs isolated from mice treated with Ad5-OVA only. In addition, the proportion of CD8+ TILs that were OVA-specific was reproducibly higher in the mice treated with Ad5-OVA + CpG IT compared with other treatment groups. These findings highlight the therapeutic potential of combining intratumoral CpG and vaccination with virus encoding tumor antigen.

CpG ODN, Toll like receptor (TLR)-9 agonist, inhibits metastatic colon adenocarcinoma in a murine hepatic tumor model

BACKGROUND

Colorectal liver metastases (mets) are often refractory to conventional therapies. CpG oligodeoxynucleotide 1826 (CpG), a Toll like receptor (TLR)-9 agonist, inhibits murine tumor growth by augmenting Th1 immunity. The impact of CpG on metastatic colon tumors is unknown. The purpose of this study was to determine the effect of CpG on the growth of hepatic colon cancer mets.

METHODS

Two studies with separate control groups were performed using 40 Balb/C mice (study A, CpG 50 μg/dose; study B, 100 μg/dose; n = 9-11/subgroup). Tumors were induced via portal vein injection of 2 × 10(4) CT26 colon tumor cells. After surgery, the mice were randomized; test groups were given 14 daily intraperitoneal (i.p.) CpG injections (50 or 100 μg/dose) while the control group received i.p. saline. On d 21 mice were sacrificed, the livers and spleens excised and weighed and the mets counted (reported as median ± 95% confidence interval [CI]) and histologically assessed.

RESULTS

The CpG mice had significantly fewer hepatic mets/mouse (study A, median two nodules, 95% CI, 0-3; study B, 0 nodules, 95% CI 0-0) than the control mice (study A, 6 nodules, 95% CI, 3-9, P = 0.002; Study B, 6 nodules, 95% CI, 3-9, P < 0.001). In study B, there were no mets in 9/11 CpG mice (versus 2/10 for CpG 50 μg and 0/19 for control mice). The mean liver/spleen weights of the CpG mice in both studies were significantly greater than in control mice. Histologically, high mitotic rates were noted in control mets while fewer tumor cells and histiocytic and lymphocytic infiltrates were found in CpG livers.

CONCLUSIONS

CpG inhibited liver tumor growth in this model (100 μg/dose more than 50 μg/dose). CpG was associated with increased liver and spleen weights not related to tumor burden. Increased lymphocytic and histiocytic infiltrates were noted in CpG-treated tumor nodules.

The dermis as a portal for dendritic cell-targeted immunotherapy of cutaneous melanoma

Complete surgical excision at an early stage remains the only curative treatment for cutaneous melanoma with few available adjuvant therapy options. Nevertheless, melanoma is a relatively immunogenic tumor type and particularly amenable to immunotherapeutic approaches. A dense network of cutaneous dendritic cells (DC) may account for the reported efficacy of vaccination through the skin and provide an attractive target for the immunotherapy of melanoma. Several phenotypically distinct DC subsets are discernable in the skin, among others, epidermal Langerhans cells and dermal DC. Upon appropriate activation both subsets can efficiently migrate to melanoma-draining lymph nodes (LN) to prime T cell-mediated responses. Unfortunately, from an early stage, melanoma development is characterized by strong immune suppression, facilitating unchecked tumor growth and spread. Particularly the primary tumor site and the first-line tumor-draining LN, the so-called sentinel LN, bear the brunt of this melanoma-induced immune suppression-and these are exactly the sites where anti-melanoma effector T cell responses should be primed by DC in order to prevent early metastasis. Through local immunopotentiation or through DC-targeted vaccination, the dermis may be utilized as a portal to activate DC and kick-start or boost effective T cell-mediated anti-melanoma immunity, even in the face of this immune suppression.

CpG oligonucleotides for immunotherapeutic treatment of neuroblastoma

Neuroblastoma is the most common extracranial solid tumor malignancy of childhood. Although it is generally responsive to treatment, high risk cases of neuroblastoma frequently recur. The prognosis for relapsed cases is extremely poor despite aggressive therapy. The frequency of relapse and subsequent failure of further treatment has spurred the need to develop non toxic and more effective treatments for targeting residual tumor cells during the phase of minimal residual disease. Traditional cancer therapies are non-specific, leading to the destruction of normal, healthy tissues. Failure to induce specific tumor immunity may be due to several immunosuppressive factors. Primary amongst these factors are: lack of co-stimulatory molecules on the surface of tumor cells, the ability of the tumor to modulate immunity in a suppressive manner and the presence of an immunosuppressive microenvironment at the location of the tumor. Unfortunately, tumor tolerance impedes the ability to establish immunity to tumor antigens and overcoming this tolerance is essential to developing effective tumor immunity. Vaccine strategies that target host immune effector cells with synthetic oligodeoxynucleotides (ODNs) that contain unmethylated CpG motifs (CpG-ODNs) represent a novel approach to overcoming tolerance in cancer therapy. This approach enables biasing of host immunity toward a proinflammatory Th1 and thus anti-tumor response. The addition of immunogenic tumor specific antigen to the CpG-ODN vaccine may allow for specific targeting and killing of established tumors.

Innovative strategies for co-delivering antigens and CpG oligonucleotides

Cytosine-phosphorothioate-guanine oligodeoxynucleotides (CpG ODN) is a recent class of immunostimulatory adjuvants that includes unmethylated CpG dinucleotide sequences similar to those commonly found in bacterial DNA. CpG ODN specifically triggers toll like receptor 9 (TLR9), which is found within phagoendosomes of antigen presenting cells (APCs) such as dendritic cells (DCs). CpG ODN triggers activation and maturation of DCs and helps to increase expression of antigens. CpG ODN can be used to induce polarized Th1 type immune responses. Several studies have shown that antigens and CpG ODN must be co-localized in the same APC to generate the most potent therapeutic antigen-specific immune responses. Delivery vehicles can be utilized to ensure co-delivery of antigens and CpG ODN to the same APCs and to significantly increase uptake by APCs. These strategies can result in antigen-specific immune responses that are 5 to 500-fold greater than administration of antigen alone. In this review, we discuss several recent and innovative strategies to co-delivering antigens and CpG ODN adjuvants to APCs. These approaches include the utilization of conjugate molecules, multi-component nanorods, liposomes, biodegradable microparticles, pulsatile release chips and cell-microparticle hybrids.

Stimulatory effects of CpG oligodeoxynucleotide on dendritic cell-based immunotherapy of colon cancer in CEA/HLA-A2 transgenic mice

Immunostimulatory DNA containing unmethylated cytosine-guanine (CpG) motifs have been successfully used as adjuvants to enhance the immunity of vaccines designed to trigger antitumor T-cell responses. We examined the effect of a CpG oligodeoxynucleotide (CpG ODN) for its ability to potentiate the activity of tumor antigen-pulsed dendritic cells (DC) in a clinically relevant mouse model, which is transgenic for both carcinoembryonic antigen (CEA) and HLA-A2 for the treatment of colon carcinoma in a therapeutic setting. The systemic administration of CpG ODN 1826 alone had modest effect on tumor growth when tumors were palpable and had no effect with larger tumor burden. However, coadministration of CpG ODN 1826 with the vaccine provided significant increase in tumor-free survival compared with mice immunized with DC-based vaccines alone. The DC/CpG combined vaccination strategy resulted in increased secretion of Th1 cytokines and HLA-A2-restricted CEA-specific CTL responses were also enhanced. Both tumor regression and extended tumor-free survival resulting from DC/CpG combination therapy required the participation of T cells. Tumor-free mice were resistant to tumor rechallenge and immunity conferred by the vaccine was transferable in athymic nude mice. These results provide evidence that vaccination with antigen-pulsed DC with CpG ODN as adjuvant can lead to effective tumor regression and long-term survival in a murine model of colon carcinoma.

Bone marrow-derived dendritic cells pulsed with tumor lysates induce anti-tumor immunity against gastric cancer ex vivo

AIM: To investigate whether bone marrow-derived dendritic cells pulsed with tumor lysates induce immunity against gastric cancer ex vivo.

METHODS: c-kit⁺ hematopoietic progenitor cells were magnetically isolated with a MiniMACS separator from BALB/c mice bone marrow cells. These cells were cultured with cytokines GM-CSF, IL-4, and TNFα to induce their maturation. They were analysed by morphological observation, phenotype analysis, and mixed lymphocyte reaction (MLR). Bone marrow-derived DCs (BM-DCs) were pulsed with tumor cell lysate obtained by rapid freezing and thawing at a 1:3 DC:tumor cell ratio. Finally, cytotoxic T lymphocyte (CTL) activity and interferon gamma (IFNγ) secretion was evaluated ex vivo.

RESULTS: c-kit⁺ hematopoietic progenitor cells from mice bone marrow cells cultured with cytokines for 8 d showed the character of typical mature DCs. Morphologically, observed by light microscope, these cells were large with oval or irregularly shaped nuclei and with many small dendrites. Phenotypically, FACS analysis showed that they expressed high levels of Ia, DEC-205, CD11b, CD80 and CD86 antigen, moderate levels of CD40, and negative for F4/80. Functionally, these cells gained the capacity to stimulate allogeneic T cells in MLR assay. However, immature DCs cultured with cytokines for 5 d did not have typical DCs phenotypic markers and could not stimulate allogeneic T cells. Ex vivo primed T cells with SGC-7901 tumor cell lysate-pulsed (TP) DCs were able to induce effective CTL activity against SGC-7901 tumor cells (E:T = 100:1, 69.55% ± 6.05% specific lysis), but not B16 tumor cells, and produced higher levels of IFNγ when stimulated with SGC-7901 tumor cells but not when stimulated with B16 tumor cells (1575.31 ± 60.25 pg/mL in SGC-7901 group vs 164.11 ± 18.52 pg/mL in B16 group, P < 0.01).

CONCLUSION: BM-derived DCs pulsed with tumor lysates can induce anti-tumor immunity specific to gastric cancer ex vivo.

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

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

Amelioration of myocarditis by statin through inhibiting cross-talk between antigen presenting cells and lymphocytes in rats

Statins, inhibitors of 3-hydroxy-3-methylglutary-coenzyme A (HMG-CoA) reductase, have been recognized as a new type of immunomodulator and reported to have anti-inflammatory effect. To investigate the effect of simvastatin, a lipophilic statin, on myocarditis, we explored whether simvastatin is able to inhibit experimental autoimmune myocarditis (EAM) and adoptive transfer of EAM in rats. We found that administration of simvastatin not only interfered with the development of EAM, but also inhibited the transfer. Antigen presenting cells (APCs) were proved to be important for the development of EAM. The ability of myocarditic splenocytes to transfer myocarditis was enhanced after co-culture with APCs. During co-culture of the myocarditic splenocytes and the APCs, simvastatin not only decreased percentages of CD28 expression in CD4-positive myocarditic splenocytes, and CD80 and CD86 expressions in APCs, but also inhibited the production of tumor necrosis factor (TNF)-partial differential in the CD4-positive myocarditic splenocytes and the APCs. These results indicate that simvastatin was able to ameliorate EAM through the inhibition of cross-talk between lymphocytes and APCs, suggesting beneficial role of simvastatin in the treatment of autoimmune myocarditis.

Co-administration of carcinoembryonic antigen and HIV TAT fusion protein with CpG-oligodeoxynucleotide induces potent antitumor immunity

Although dendritic cells (DC) have been well demonstrated as a strong cellular adjuvant for a tumor vaccine, there are several limitations for clinical application. A protein-based vaccine using a potent adjuvant is an appealing approach for tumor antigen-specific immunotherapy because of their simplicity, safety, efficacy and capacity for repeated administration. CpG-oligodeoxynucleotides (ODN) have been used as adjuvants to stimulate innate and adaptive immune responses for cancer treatment. The authors evaluated the adjuvant effects of CpG-ODN in a vaccine incorporating recombinant fusion protein of the HIV TAT PTD domain and carcinoembryonic antigen (TAT-CEA). Mice vaccinated with TAT-CEA and CpG-ODN (TAT-CEA + CpG) showed enhanced CEA-specific immunity, including cytotoxic T-lymphocytes (CTL) activity and interferon (IFN)-gamma secreting T cells compared with CEA and CpG-ODN (CEA + CpG) or TAT-CEA vaccination alone. Vaccination with TAT-CEA + CpG elicited Th1-based responses, as indicated by the higher ratio of immunoglobulin (Ig)G2a antibody/IgG1 antibodies specific for CEA. The survival rate was significantly increased after vaccination with TAT-CEA + CpG in a tumor model using MC38/CEA2. Furthermore, the TAT-CEA +/- CpG vaccine groups showed similar antitumor immunity to the CEA peptide-pulsed DC (CEA peptide/DC) vaccine groups. These data suggest that coadministration of TAT fusion protein with CpG-ODN may serve as a potential formulation for enhancing antitumor activity.

Comparison of DNA- and mRNA-Transfected Mouse Dendritic Cells as Potential Vaccines against the Human Papillomavirus Type 16 associated Oncoprotein E7

Background

Dendritic cells (DCs) mediate the generation of strong cytotoxic T-lymphocyte (CTL) responses by functioning in antigen presentation and exerting adjuvant properties. We compared several activation markers and parameters of biological activity of DNA- and mRNA-transfected DCs in vitro and in vivo.

Methods

CpG-matured, bone marrow derived C57BL/6 mouse DCs were electroporated either with enhanced green fluorescence protein (EGFP) or human papillomavirus type 16 (HPV16) E7 expression plasmids or in vitro transcribed mRNAs encoding for the codon-optimized E7 or a shuffled version thereof. Activation marker expression and antigen presentation was analysed by fluorescence-activated cell sorting. The migratory behaviour of transfected DCs were investigated by in vitro chemotaxis experiments and cytokine expression by ELISA. CTL-priming capacity of transfected DCs were determined by vaccination of mice.

Results

mRNA transfection produced a two- to fourfold increase of the activation markers CD40, CD80, CD86 and MHC I and MHC II molecules. Predominately antigen-expressing DCs migrated after mRNA transfection. Furthermore, mRNA-transfected DCs were capable of inducing a chemokine gradient. After maturation, electroporation and activation with soluble CD40 ligand and interferon-γ, DCs displayed a T-helper cell type 2 cytokine expression pattern. Nevertheless, E7-transfected DCs were able to prime E7-specific CTL responses in vivo. The highest E7-specific CTL frequencies were found in mice immunized with mRNA-transfected DCs. The in vitro expanded CTLs exerted functional E7-specific cytotoxic activity.

Conclusions

Genetically modified DCs are suitable vehicles for the induction of E7-specific CTL responses in mice and hence could help to eradicate HPV-associated lesions in humans.

A comparative study of the antigen-specific immune response induced by co-delivery of CpG ODN and antigen using fusion molecules or biodegradable microparticles

CpG ODN are toll-like receptor 9 (TLR9) agonists that can enhance antigen presentation by antigen presenting cells (APCs) such as dendritic cells (DCs). The most potent antigen-specific responses are seen when CpG ODN and the antigen are co-localized in the same APC. CpG ODN-antigen fusion molecules and biodegradable microparticles entrapping CpG ODN and antigen can ensure both components are delivered to the same APC. In this study, we compared the efficacy of the CpG-ODN fusion molecules against biodegradable microparticles entrapping antigen and CpG ODN. Microparticles were prepared using a double emulsion solvent evaporation methodology. CpG ODN-OVA fusion molecules were prepared by mixing maleimide-activated protein with thiolated CpG ODN. Both CpG ODN-OVA fusion molecules and microparticles co-entrapping CpG ODN and OVA generated stronger IgG2a and interferon-gamma (IFN-gamma) responses than delivery of soluble CpG ODN and OVA. The microparticles generated stronger IgG2a and IFN-gamma immune responses than did CpG ODN-antigen fusion molecules.

Potent antigen-specific immune responses stimulated by codelivery of CpG ODN and antigens in degradable microparticles

CpG ODN stimulates a TH1 response through its receptor Toll-like receptor 9 (TLR9). TLR9 is a receptor that is found intracellularly. Microparticles are efficiently internalized by dendritic cells (DCs) and macrophages and would thus be an ideal delivery vehicle for CpG ODN to reach its target site thereby enhancing the TH1 response to an antigen also encapsulated in the microparticle. Here, we show that careful control over fabrication parameters can produce biodegradable microparticles with predictable size distributions, surface morphology, and shape. Entrapment efficiencies of the model antigen OVA ranged from 19% to 23% with an average loading of 10 microg/mg of microparticles. For CpG ODN, these values were 33% to 35%, which corresponded to an average loading of 8.5 microg/mg of microparticles. The microparticles release CpG ODN and OVA in a burst followed by sustained release profile. At the highest concentration of microparticles incubated with a pure DC cell line, 92% of DCs had internalized microparticles by 16 hours, confirming that DCs efficiently take up the microparticles. Microparticles are capable of inducing DC maturation as determined by up-regulation of CD80 and CD86 markers. Although the presence of CpG ODN in the microparticles did not impact on the phenotype of the DCs, it was necessary for DCs to induce activation of antigen-specific T cells as indicated by interferon-gamma production. Microparticles entrapping both antigen and CpG ODN induced significantly higher amounts of anti-OVA antibody production than other preparations such as the soluble OVA and CpG ODN (P<0.01) and stimulated stronger IgG2a production than delivery of microparticles entrapping antigen alone. We conclude that co-encapsulating immunostimulatory CpG ODN and antigen in degradable microparticles is an effective approach to enhancing development of a TH1 immune response.

Characterization of the MUC1.Tg/MIN transgenic mouse as a model for studying antigen-specific immunotherapy of adenomas

A bigenic MUC1.Tg/MIN mouse model was developed by crossing Apc/(MIN/+) (MIN) mice with human MUC1 transgenic mice to evaluate MUC1 antigen-specific immunotherapy of intestinal adenomas. The MUC1.Tg/MIN mice developed adenomas at a rate comparable to that of MIN mice and had similar levels of serum MUC1 antigen. A MUC1-based vaccine consisting of MHC class I-restricted MUC1 peptides, a MHC class II-restricted pan-helper peptide, unmethylated CpG oligodeoxynucleotide and GM-CSF caused flattening of adenomas and significantly reduced the number of large adenomas. Immunization was successful in generating a MUC1-directed immune response evidenced by increased MUC1 peptide-specific anti-tumor cytotoxicity and IFN-gamma secretion by lymphocytes.

Development of TLR9 agonists for cancer therapy

In vertebrates, the TLRs are a family of specialized immune receptors that induce protective immune responses when they detect highly conserved pathogen-expressed molecules. Synthetic agonists for several TLRs, including TLR3, TLR4, TLR7, TLR8, and TLR9, have been or are being developed for the treatment of cancer. TLR9 detects the unmethylated CpG dinucleotides prevalent in bacterial and viral DNA but not in vertebrate genomes. As discussed in this Review, short synthetic oligodeoxynucleotides containing these immune stimulatory CpG motifs activate TLR9 in vitro and in vivo, inducing innate and adaptive immunity, and are currently being tested in multiple phase II and phase III human clinical trials as adjuvants to cancer vaccines and in combination with conventional chemotherapy and other therapies.

Increased sensitivity of radiated murine cervical cancer tumors to E7 subunit vaccine-driven CTL-mediated killing induces synergistic anti-tumor activity

The development of therapeutic vaccines has important implications for the treatment of cancer patients. Here we investigate whether human papillomavirus (HPV) E7 subunit vaccines can enhance tumor radioresponse using an established cervical cancer animal model. Radiation plus E7 subunit vaccines improved complete response, cure, and recurrence rates of tumors dramatically compared with single therapy alone. In particular, both components of the E7 subunit vaccines (E7 protein and CpG-oligodeoxynucleotide) were required for the induction of antigen (Ag)-specific cytotoxic T-lymphocyte (CTL) responses and for therapeutic synergy with radiotherapy. Moreover, with combined therapy the radiation dose could be reduced by 16 Gy to achieve an equivalent anti-tumor efficacy to radiation treatment alone. This therapeutic synergy was found to be mediated by CD8(+) CTLs and was concomitant with histological changes (presence of apoptotic bodies and multinucleated giant cells; heavy infiltration of lymphocytes), as determined by in vivo T-cell depletion and histological analysis. Finally, phenotypic changes of radiated tumors and their increased sensitivity to CTL-mediated killing appeared to be responsible for therapeutic synergy. These results show that E7 subunit vaccines act as a potent enhancer of tumor radioresponse and that this is mediated by increased sensitivity of radiated tumors to CTL-mediated killing. This study further suggests that E7-targeted therapeutic vaccines have the potential to improve radiotherapy in patients with cervical cancer.

Photodynamic therapy-generated tumor cell lysates with CpG-oligodeoxynucleotide enhance immunotherapy efficacy in human papillomavirus 16 (E6/E7) immortalized tumor cells

Immunotherapy with photodynamic therapy (PDT) offers great promise as a new alternative for cancer treatment; however, its use remains experimental. In this study, we examined the immunotherapeutic significance of human papillomavirus (HPV)-immortalized tumor cell lysates induced by PDT with CpG-oligodeoxynucleotide (ODN). PDT-cell lysates were generated by irradiating Radachlorin (5 microg/mL) preloaded TC-1 cells carrying HPV 16 E7. PDT-cell lysates plus ODN coinjection for protection against E7-expressing tumors as well as specific immune responses were evaluated with the following tests: heat shock protein 70 (HSP70) enzyme-linked immunosorbent assay, in vitro and in vivo tumor growth inhibition, interferon-gamma (IFN-gamma) and tumor necrosis factor-alpha (TNF-alpha) assay, cytotoxic T-lymphocyte assay, and fluorescence activated cell sorting (FACS) analysis. PDT-cell lysates plus ODN coinjection showed a significant suppression of tumor growth at both prophylactic and therapeutic levels, compared to PDT (or F/T)-cell lysates or ODN alone. In addition, we evaluated the level of the immune response with the coinjection. HSP70, an important regulator of inflammatory and immune response, was observed in abundance in the PDT-cell lysates. IFN-gamma production and cytotoxic T lymphocytes (CTL) responses were induced by PDT-cell lysates plus ODN injection. The coinjection resulted in PDT-cell lysate-specific antibodies (IgG1, IgG2a, IgG2b, and IgG3) and T-helper cell responses significantly higher than PDT-cell lysates alone. Moreover, IFN-gamma production and CTL responses were significantly induced in the PDT-cell lysate plus ODN immunized groups. These enhanced immune responses appeared to be mediated by CD8+ T cells only. These data suggest that PDT-cell lysates plus ODN injection may be an effective approach to induce CTL immune responses as a possible immunotherapeutic strategy for cancer therapy.

Therapeutic synergy of human papillomavirus E7 subunit vaccines plus cisplatin in an animal tumor model: causal involvement of increased sensitivity of cisplatin-treated tumors to CTL-mediated killing in therapeutic synergy

PURPOSE

The goal of this study was to investigate the therapeutic potentials of combining chemotherapy with human papillomavirus (HPV) E7 subunit vaccines in an animal tumor model and to determine the underlying therapeutic mechanisms.

EXPERIMENTAL DESIGN

Animals bearing HPV E6/E7-expressing tumors were treated intratumorally with a selected cytotoxic drug, cisplatin, twice at 1-week interval and s.c. with E7 subunit vaccines thrice at 1-week interval. Tumor chemoimmunoresponse was measured by tumor size. Ag-specific CTL activities and tumor histology were checked in mice under treatments. Apoptosis, in vivo T-cell subset depletion, adoptive CTL transfer, and tumor regression were used to determine the mechanisms for antitumor therapeutic effects.

RESULTS

Combined therapy using cisplatin plus E7 subunit vaccines improved cure and recurrence rates of tumors and long-term antitumor immunity dramatically more than single therapy alone. In particular, both components of E7 subunit vaccines were required for induction of Ag-specific CTL as well as therapeutic synergy when combined with cisplatin. This therapeutic synergy was abrogated by depletion of CD8(+) T cells in vivo and was concomitant with histologic changes (such as heavy infiltration of lymphocytes and reduced tumor cell density). Finally, the increased sensitivity of cisplatin-treated tumors to CTL-mediated killing was found to be responsible for therapeutic synergy.

CONCLUSIONS

E7 subunit vaccines plus cisplatin mediate antitumor therapeutic synergy through the increased sensitivity of cisplatin-treated tumors to CTL-mediated killing. Moreover, E7-based therapeutic vaccines have the potential to improve chemotherapy in patients with cervical cancer.

Immunomodulatory effects associated with a live vaccine against Leishmania major containing CpG oligodeoxynucleotides

The inoculation of live Leishmania major to produce a lesion that heals (leishmanization) is to date the only vaccine against cutaneous leishmaniasis that has proven effective in humans, but it still has an unacceptable frequency of large ulcerating lesions that are slow to heal or, in rare cases, non-healing. We have previously shown that C57BL/6 mice vaccinated intradermally with 10(4) L. major/50 microg CpG oligodeoxynucleotides develop little or no dermal lesions and show early containment of parasite growth in the vaccination site, eliminating safety concerns related to the inoculation of live organisms. The addition of CpG to the live vaccine resulted in early activation of dermal dendritic cells and increased IL-6 production, as well as in a reduction in the accumulation of Foxp3(+)CD4(+)CD25(+) regulatory T (T(reg)) cells that naturally occurs in the skin following Leishmania infection. Neutralization of IL-6 caused the development of larger lesions and increased local T(reg) cell numbers. Transfer of vaccine-primed dendritic cells into IL-6-deficient mice mitigated lesion development, indicating that IL-6 reconstitution limited pathology in the vaccination site.

Immunomodulatory oligonucleotides as novel therapy for breast cancer: pharmacokinetics, in vitro and in vivo anticancer activity, and potentiation of antibody therapy

Oligonucleotides containing CpG motifs and immunomodulatory oligonucleotides (IMO) containing a synthetic immunostimulatory dinucleotide and a novel DNA structure have been suggested to have potential for the treatment of various human diseases. In the present study, a newly designed IMO was evaluated in several models of human (MCF-7 and BT474 xenograft) and murine (4T1 syngeneic) breast cancer. Pharmacokinetics studies of the IMO administered by s.c., i.v., p.o., or i.p. routes were also accomplished. The IMO was widely distributed to various tissues by all four routes, with s.c. administration yielding the highest concentration in tumor tissue. The IMO inhibited the growth of tumors in all three models of breast cancer, with the lowest dose of the IMO inhibiting MCF-7 xenograft tumor growth by >40%. Combining the IMO with the anticancer antibody, Herceptin, led to potent antitumor effects, resulting in >96% inhibition of tumor growth. The IMO also exerted in vitro antitumor activity, as measured by cell growth, apoptosis, and proliferation assays in the presence of Lipofectin. This is the first report of the pharmacokinetics of this agent in normal and tumor-bearing mice. Based on the present results, we believe that the IMO is a good candidate for clinical development for breast cancer therapy used either alone or in combination with conventional cancer therapeutic agents.

In vivo control of acute lymphoblastic leukemia by immunostimulatory CpG oligonucleotides

Despite considerable success in treating newly diagnosed childhood acute lymphoblastic leukemia (ALL), relapsed disease remains a significant clinical challenge. Using a NOD/SCID mouse xenograft model, we report that immunostimulatory DNA oligonucleotides containing CpG motifs (CpG ODNs) stimulate significant immune activity against primary human ALL cells in vivo. The administration of CpG ODNs induced a significant reduction in systemic leukemia burden, mediated continued disease control, and significantly improved survival of mice with established human ALL. The death of leukemia cells in vivo was independent of the ability of ALL cells to respond directly to CpG ODNs and correlated with the production of IL-12p70, IFN-α, and IFN-γ by the host. In addition, depletion of natural killer cells by anti–asialo-GM1 treatment significantly reduced the in vivo antileukemic activity of CpG ODN. This antileukemia effect was not limited to the xenograft model because natural killer cell–dependent killing of ALL by human peripheral blood mononuclear cells (PBMCs) was also increased by CpG ODN stimulation. These results suggest that CpG ODNs have potential as therapeutic agents for the treatment of ALL.

Antitumor therapeutic effects of e7 subunit and DNA vaccines in an animal cervical cancer model: antitumor efficacy of e7 therapeutic vaccines is dependent on tumor sizes, vaccine doses, and vaccine delivery routes

We previously reported that E7 subunit and DNA vaccines are both capable of inducing antitumor protection through induction of antigen-specific CTL. In this study, we investigated their ability to control established tumors according to tumor size, vaccine doses, and vaccine delivery routes. Antitumor therapeutic efficacy of both vaccine types was dependent on tumor burden. However, E7 subunit vaccines induced a higher level of antitumor therapeutic activities at the tested dose compared to DNA vaccines. This was concomitant with induction of antibody, CTL, and IFN-gamma responses, as well as histologic changes (heavy infiltration of lymphocytes and presence of apoptotic bodies). In vaccine dose titration assays, 50 and 100 microg of DNA vaccines exhibited an equivalent antitumor efficacy to 0.5 and 1 microg of E7 subunit vaccines, respectively, i.e., a 100-fold difference in E7 dosage, suggesting the importance of vaccine doses for achieving antitumor immunity. Furthermore, tumors of a larger size were controlled by intratumoral injection with E7 subunit vaccines, underscoring the importance of vaccine delivery routes for antitumor therapeutic efficacy. Thus, these data suggest that antitumor therapeutic efficacy of E7 therapeutic vaccines is determined by vaccine doses, vaccine delivery routes, and tumor sizes, and that these vaccines could be another addition to conventional therapy modalities against cervical cancer.

CpG oligonucleotides enhance the tumor antigen-specific immune response of an anti-idiotype antibody-based vaccine strategy in CEA transgenic mice

A murine monoclonal anti-idiotype (Id) antibody, 3H1 has been developed and characterized previously. Anti-Id 3H1 mimics a specific epitope of carcinoembryonic antigen (CEA) and can be used as a surrogate antigen for CEA. 3H1 induced anti-CEA immunity in different species of animals as well as humans and showed promise as a potential vaccine candidate in phase I/II clinical trials for colon cancer patients. One area of interest to us has been the development of new immune adjuvants that may augment the potency of 3H1 as a tumor vaccine. Oligodeoxynucleotides containing unmethylated CpG motifs (CpG ODN) are potent immunostimulatory agents capable of enhancing the Ag-specific Th1 response when used as immune adjuvants. In this study, we have evaluated the efficacy of 3H1 as a tumor vaccine when admixed with a select CpG ODN 1826 in transgenic mice that express human CEA. The vaccine potential of 3H1 was also assessed in the presence of another widely used adjuvant, QS-21. 3H1 coupled to keyhole limpet hemocyanin (KLH) and mixed with Freund's adjuvant (FA) was used as a gold standard in this system. 3H1 vaccination with different adjuvants induced both humoral and cellular anti-3H1, as well as anti-CEA immunity in CEA transgenic mice. The immune sera could lyse CEA-transfected murine colon carcinoma cells, C15 effectively in an antibody-dependent cellular cytotoxicity assay. The anti-CEA antibody responses were somewhat comparable in each adjuvant-treated group of mice, whereas cellular immune responses were significantly greater when CpG was used as an adjuvant. Splenocytes obtained from 3H1-CpG-immunized mice showed an increased proliferative CD4(+) Th1-type T-cell response when stimulated in vitro with 3H1 or CEA and secreted elevated levels of Th1 cytokines (IL-2, IFN-gamma). This vaccine also induced MHC class I antigen-restricted CD8(+) T-cell responses. In a solid tumor model, C15 tumor growth was significantly inhibited by 3H1 vaccinations. In 3H1-CpG-vaccinated mice, the duration of survival was, however, longer compared to the 3H1-QS21-vaccinated mice. These findings suggest that 3H1-CpG vaccinations can break peripheral tolerance to CEA and induce protective antitumor immunity in this murine model transgenic for human CEA.

Reciprocal and dynamic control of CD8 T cell homing by dendritic cells from skin- and gut-associated lymphoid tissues

T cell activation by intestinal dendritic cells (DC) induces gut-tropism. We show that, reciprocally, DC from peripheral lymph nodes (PLN-DC) induce homing receptors promoting CD8 T cell accumulation in inflamed skin, particularly ligands for P- and E-selectin. Differential imprinting of tissue-tropism was independent of Th1/Th2 cytokines and not restricted to particular DC subsets. Fixed PLN-DC retained the capacity to induce selectin ligands on T cells, which was suppressed by addition of live intestinal DC. By contrast, fixed intestinal DC failed to promote gut-tropism and instead induced skin-homing receptors. Moreover, the induction of selectin ligands driven by antigen-pulsed PLN-DC could be suppressed "in trans" by adding live intestinal DC, but PLN-DC did not suppress gut-homing receptors induced by intestinal DC. Reactivation of tissue-committed memory cells modified their tissue-tropism according to the last activating DC's origin. Thus, CD8 T cells activated by DC acquire selectin ligands by default unless they encounter fixation-sensitive signal(s) for gut-tropism from intestinal DC. Memory T cells remain responsive to these signals, allowing for dynamic migratory reprogramming by skin- and gut-associated DC.

Enhanced tumor-specific long-term immunity of hemagglutinating [correction of hemaggluttinating] virus of Japan-mediated dendritic cell-tumor fused cell vaccination by coadministration with CpG oligodeoxynucleotides

Immunization with dendritic cells (DCs) using various Ag-loading approaches has shown promising results in tumor-specific immunotherapy and immunoprevention. Fused cells (FCs) that are generated from DCs and tumor cells are one of effective cancer vaccines because both known and unknown tumor Ags are presented on the FCs and recognized by T cells. In this study, we attempted to augment antitumor immunity by the combination of DC-tumor FC vaccination with immunostimulatory oligodeoxynucleotides containing CpG motif (CpG ODN). Murine DCs were fused with syngeneic tumor cells ex vivo using inactivated hemagglutinating virus of Japan (Sendai virus). Mice were intradermally (i.d.) immunized with FCs and/or CpG ODN. Coadministration of CpG ODN enhanced the phenotypical maturation of FCs and unfused DCs, and the production of Th1 cytokines, such as IFN-gamma and IL-12, leading to the induction of tumor-specific CTLs without falling into T cell anergy. In addition, immunization with FCs + CpG ODN provided significant protection against lethal s.c. tumor challenge and spontaneous lung metastasis compared with that with either FCs or CpG ODN alone. Furthermore, among mice that rejected tumor challenge, the mice immunized with FCs + CpG ODN, but not the mice immunized with FCs or CpG ODN alone, completely rejected tumor rechallenge, indicating that CpG ODN provided long-term maintenance of tumor-specific immunity induced by FCs. Thus, the combination of DC-tumor FCs and CpG ODN is an effective and feasible cancer vaccine to prevent the generation and recurrence of cancers.

CpG DNA and cancer immunotherapy: orchestrating the antitumor immune response

PURPOSE OF REVIEW

Cancer treatment is entering an era of targeted approaches. One such approach is use of the immune system to recognize and eliminate malignant cells. Synthetic CpG oligonucleotides (CpG DNA) are a relatively new class of agents that have the ability to stimulate a potent, orchestrated tumor-specific immune response. This review provides an overview of the immunologic effects of CpG DNA and summarizes the results of preclinical investigations that have led to ongoing development of CpG DNA as a component of clinical cancer immunotherapy.

RECENT FINDINGS

New studies demonstrate that at least three classes of CpG DNA sequences exist, each with different physical characteristics and biologic effects. Preliminary studies in several animal models of cancer suggest that CpG DNA have the ability to induce tumor regression by activating innate immunity, enhancing antibody dependent cellular cytotoxicity, and serving as potent vaccine adjuvants that elicit a specific, protective immune response.

SUMMARY

Animal models suggest that CpG DNA may have many uses in cancer immunotherapy. Early clinical trials suggest that CpG DNA can be administered safely to humans, and studies are ongoing to understand how these agents may play a role in cancer immunotherapy.

Enhancement of antibody responses in DNA vaccination using a vector encoding a universal T-helper cell epitope

DNA vaccination appears as a very promising approach to raise protective antibodies against a variety of proteins from pathogens or tumor cells, but is often hindered by the low immunogenicity of the genetic vectors used for the immunizations. To enhance the humoral response through improvement of the antigenic presentation of newly synthesized proteins upon vaccination, we engineered a plasmid coding for a low immunogenic protein (an scFv, i.e. the single-chain Fragment variable of a well-characterized antibody) fused to a small-size universal T-helper cell epitope derived from tetanus toxin, whose efficiency in classical protein-based immunization protocols has already been demonstrated. We found that immunization of C57Bl/6 mice using this vector greatly enhanced the production not only of specific antibodies recognizing essentially conformational epitopes on the undenatured scFv protein but also of antibodies against linear epitopes on the denatured protein. Since this T-epitope is known to be accommodated by several haplotypes of H-2 molecules in mice, as well as by various class II MHC molecules in humans, the results reported here allow us to conclude that this method could be of general interest for future applications of genetic immunization, including DNA-based vaccinations in humans.

CpG-ODN-stimulated dendritic cells act as a potent adjuvant for E7 protein delivery to induce antigen-specific antitumour immunity in a HPV 16 E7-associated animal tumour model

We previously reported that both E7 and CpG-oligodeoxynucleotide (ODN) are required for protecting animals from human papillomavirus (HPV) 16 E7-associated tumour challenge. Here we investigate dendritic cells (DC)-based approach in this protection. In the study, we isolated bone marrow-derived DC and stimulated DC with E7 and ODN. In vitro stimulation of DC with E7 plus ODN resulted in more production of interleukin-12, as compared to that with E7 or ODN alone. Further injection with E7+ODN-stimulated DC resulted in more significant tumour protection, as compared to stimulation with E7 or ODN alone. We further evaluated the levels of immune responses induced by DC stimulated with E7+ODN. We observed little enhancement of E7-specific antibody and T helper cell proliferative responses by E7+ODN stimulation, as compared to E7 stimulation. However, there was some enhancement of interferon-gamma (IFN-gamma) production from CD4+ T cells and a more significant production of IFN-gamma from CD8+ T cells by E7+ODN stimulation, as compared to E7 stimulation alone. This was consistent with intracellular IFN-gamma staining levels of CD8+ T cells. Tumour protection further appeared to be mediated by CD8+ T cells, as determined by in vivo T-cell depletion. Thus, these data suggest that upon ODN stimulation DC might function as a potent adjuvant for E7 protein delivery for induction of protective cellular immunity against HPV E7-associated tumour challenge.

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.

Antigenic epitopes fused to cationic peptide bound to oligonucleotides facilitate Toll-like receptor 9-dependent, but CD4+ T cell help-independent, priming of CD8+ T cells

A priority in current vaccine research is the development of adjuvants that support the efficient priming of long-lasting, CD4(+) T cell help-independent CD8(+) T cell immunity. Oligodeoxynucleotides (ODN) with immune-stimulating sequences (ISS) containing CpG motifs facilitate the priming of MHC class I-restricted CD8(+) T cell responses to proteins or peptides. We show that the adjuvant effect of ISS(+) ODN on CD8(+) T cell priming to large, recombinant Ag is enhanced by binding them to short, cationic (arginine-rich) peptides that themselves have no adjuvant activity in CD8(+) T cell priming. Fusing antigenic epitopes to cationic (8- to 10-mer) peptides bound to immune-stimulating ISS(+) ODN or nonstimulating NSS(+) ODN (without CpG-containing sequences) generated immunogens that efficiently primed long-lasting, specific CD8(+) T cell immunity of high magnitude. Different MHC class I-binding epitopes fused to short cationic peptides of different origins showed this adjuvant activity. Quantitative ODN binding to cationic peptides strikingly reduced the toxicity of the latter, suggesting that it improves the safety profile of the adjuvant. CD8(+) T cell priming supported by this adjuvant was Toll-like receptor 9 dependent, but required no CD4(+) T cell help. ODN (with or without CpG-containing sequences) are thus potent Th1-promoting adjuvants when bound to cationic peptides covalently linked to antigenic epitopes, a mode of Ag delivery prevailing in many viral nucleocapsids.

Myeloid differentiation factor 88-dependent post-transcriptional regulation of cyclooxygenase-2 expression by CpG DNA: tumor necrosis factor-alpha receptor-associated factor 6, a diverging point in the Toll-like receptor 9-signaling

The immune stimulatory unmethylated CpG motifs present in bacterial DNA (CpG DNA) induce expression of cyclooxygenase-2 (cox-2). The present study demonstrates that CpG DNA can up-regulate cox-2 expression by post-transcriptional mechanisms in RAW264.7 cells. To determine the CpG DNA-mediated signaling pathway that post-transcriptionally regulates cox-2 expression, a cox-2 translational reporter (COX2-3'-UTR-luciferase) was generated by inserting sequences within the 3'-untranslated region (UTR) of cox-2 to the 3' end of the luciferase gene under control of the SV40 promoter. CpG DNA-induced COX2-3'-UTR-luciferase activity was completely inhibited by an endosomal acidification inhibitor chloroquine, a Toll-like receptor 9 antagonist inhibitory CpG DNA, or overexpression of a dominant negative (DN) form of MyD88. However, overexpression of DN-IRAK-1 or DN-TRAF6 resulted in substantial, but not complete, inhibition of the CpG DNA-induced COX2-3'-UTR-luciferase activity. Activation of all three MAPKs (ERK, p38, and JNK) was required for optimal COX2-3'-UTR-luciferase activity induced by CpG DNA. Overexpression of DN-TRAF6 suppressed CpG DNA-mediated activation of p38 and JNK, but not ERK, explaining the partial inhibitory effects of DN-TRAF6 on CpG DNA-induced COX2-3'-UTR-luciferase activity. Co-expression of DN-TRAF6 and N17Ras completely inhibited CpG DNA-induced COX2-3'-UTR-luciferase activity, indicating the involvement of Ras in CpG DNA-mediated ERK and COX2-3'-UTR regulation. Collectively, our results suggest that MyD88 and MAPKs play a key regulatory role in CpG DNA-mediated cox-2 expression at the post-transcriptional level and that TRAF6 is a diverging point in the Toll-like receptor 9-signaling pathway for CpG DNA-mediated MAPK activation.

The intratumoral application of poly-G-oligodeoxynucleotides does not augment the naturally induced antitumoral CD8-T-cell response in P815 mastocytomas

DNA sequences containing CpG have been described to induce a strong immune reaction by acting on a variety of immune cells including a strong and pronounced antitumoral response. Poly-G-oligodeoxynucleotides (ODNs) on the other hand have been attributed the preferential induction of CD8-T-cell proliferation when used in vitro. This activity led us to the investigation of the possible antitumoral properties of poly-G-ODNs in an established CD8-dependent tumor eradication model. We used the well described poly-G-ODN 1628 in its capacity to enhance antitumoral CD8 response in the cutaneous mastocytoma P815. When injecting 30 microg of the purified phosphothioate-modified oligo into the tumor bearing area of P815 challenged mice for up to 12 consecutive days we did not observe increased tumor rejection as compared to the group of mice injected with a control oligo. The 1628-injected mice did not produce higher numbers of P815-specific CD8 cells as measured by P1A-, and P1E-tetramer staining and Immunoscope analysis. Furthermore, tumor-specific CD8 cells in 1628 did not show enhanced antitumoral cytotoxicity when analyzing lymphocyte-tumor cell co-cultures or transcription of the cytotoxic CD8-cell associated molecules interferon gamma, FAS ligand, perforin, or granzyme B by quantitative real-time RT-PCR. These experiments show that there is no enhanced induction of an antitumoral CD8 response after in situ administration of poly-G-ODNs in the P815 mastocytoma model.

Vaccine adjuvants: role and mechanisms of action in vaccine immunogenicity

Inactivated vaccines require adjuvants to stimulate an immune response. The choice of adjuvant or immune enhancer determines whether the immune response is effective, ineffective or damaging. Accordingly, there is a need for new adjuvants that stimulate the appropriate immunity, for example, T cell immunity for intracellular pathogens and cancer vaccines. In several adjuvants, the identification of chemical groups that interact with specific cell toll-like receptors (innate immunity) or receptors for co-stimulatory ligands (adaptive immunity), has enabled the establishment of structure-function relationships that are useful in the design of new adjuvants. Because of the crucial immunomodulating role of adjuvants, sub-unit vaccine development will remain dependent on new adjuvants.

In vivo impact of CpG1826 oligodeoxynucleotide on CD8 T cell primary responses and survival

CpG oligodeoxynucleotide (ODN) promotes maturation of APCs in vivo and induces strong type 1 T cell responses in mice. In this study, we have investigated the ability of CpG1826 to modulate peptide-specific CD8 T cell responses in a context where CD4 T cells are likely to play a minor role. The effects of CpG1826 were evaluated in a system where a population of NP68-specific F5 TCR transgenic CD8 T cells is diluted into a polyclonal host following adoptive transfer into C57BL/10 syngeneic recipients. Using this approach, we found that CpG1826 enhanced the ability of F5 CD8 T cells to undergo multiple divisions in vivo, to express IFN-gamma ex vivo, and to up-regulate memory-associated cell surface markers such as CD122 (IL-2Rbeta) and Ly-6C. Moreover, CpG1826 greatly increased in vivo cytotoxic activity. Using tetramer detection, we found that CpG1826 promoted long-term survival of Ag-specific CD8 T cells after immunization while no NP68-specific cells were detected when the cognate peptide was injected alone. These results indicate that CpG1826 acts as an adjuvant which increases CD8 T cell effector responses and promotes long-term survival of NP68 peptide-specific cells in vivo. They also suggest that this adjuvant can modulate CD8 T cell responses in a system which is likely to be independent of CD4 T cell help.

Platelet-mediated modulation of adaptive immunity. A communication link between innate and adaptive immune compartments

Platelets are highly reactive components of the circulatory system with well-documented hemostatic function. Recent studies extend platelet function to modulation of local inflammatory events through the release of chemokines, cytokines, and a number of immunomodulatory ligands, including CD154. We hypothesized that platelet-derived CD154 modulates adaptive immunity. The data reported herein demonstrate that platelets, via CD154, induce dendritic cell maturation, B cell isotype switching, and augment CD8(+) T cell responses both in vitro and in vivo. Platelet transfusion studies demonstrate that platelet-derived CD154 alone is sufficient to induce isotype switching and augment T lymphocyte function during viral infection, leading to enhanced protection against viral rechallenge. Additionally, depletion of platelets in normal mice results in decreased antigen-specific antibody production.

Myeloid differentiation factor 88-dependent transcriptional regulation of cyclooxygenase-2 expression by CpG DNA: role of NF-kappaB and p38

CpG DNA induces macrophage cyclooxgenase-2 (Cox-2) production. In this study, we have investigated a biochemical signaling pathway and transcription factors responsible for transcriptional regulation of the Cox-2 gene expression induced by CpG DNA. CpG DNA-induced Cox-2 promoter activity was completely inhibited by an endosomal acidification inhibitor (chloroquine), a TLR9 antagonist inhibitory CpG DNA, or overexpression of a dominant negative (DN) form of MyD88. In contrast, overexpression of DN-IRAK1 or DN-TRAF6 only partially inhibited CpG DNA-induced Cox-2 promoter activity and NF-kappaB activation, indicating the presence of additional signaling modulators downstream of MyD88. CpG DNA-induced Cox-2 promoter activity was substantially suppressed in cells overexpressing super-suppressive IkappaB (IkappaB-arachidonic acid), DN-p38, or DN-CREB. In addition, Cox-2 promoter-luciferase reporters with alterations in predicted cis-acting transcriptional regulatory elements revealed that C/EBP, Ets-1, NF-kappaB, and CREB-binding sites are essential for optimal Cox-2 expression in response to CpG DNA. Conclusively, these results demonstrate that endosomal DNA processing and TLR9/MyD88-dependent activation of NF-kappaB and p38 are required for transcriptional regulation of Cox-2 expression induced by CpG DNA, and suggest that interleukin-1 receptor-associated kinase and/or TRAF6 may be a diverging point for NF-kappaB activation in response to CpG DNA in RAW264.7 cells.

Toll-like receptor ligand links innate and adaptive immune responses by the production of heat-shock proteins

The report shows that CpG can exert additional adjuvant effects by inducing cells that are normally inferior antigen (Ag)-presenting cells to participate in immune induction by cross-priming. Macrophages (Mphi) exposed to protein Ag in the presence of bioactive CpG DNA released material that induced primary CD8(+) T cell responses in DC-naïve T cell cultures. This cross-priming event was accompanied by up-regulation of the stress protein response as well as inflammatory cytokine expression in treated Mphi. The material released was indicated to contain inducible heat shock protein-70 and epitope peptide, which in turn, were presented by dendritic cells (DCs) to responder T cells. Such an adjuvant effect by CpG may serve to salvage immunogenic material from otherwise inert depot cellular sites and additionally stimulate DCs to effectively cross-prime. The cross-priming, shown also to occur in vivo, may be particularly useful when Ag doses are low and have minimal opportunity for delivery to DCs for consequent direct priming.

TOLL-like receptors linking innate and adaptive immune response

Invading pathogens are controlled by the innate and adaptive arms of the immune system. Adaptive immunity, which is mediated by B and T lymphocytes, recognises pathogens by rearranged high affinity receptors. However, the establishment of adaptive immunity is often not rapid enough to eradicate microorganisms as it involves cell proliferation, gene activation and protein synthesis. More rapid defense mechanisms are provided by innate immunity, which recognises invading pathogens by germ-line-encoded pattern recognition receptors (PRR). Recent evidence shows that this recognition can mainly be attributed to the family of TOLL-like receptors (TLR). Binding of pathogen-associated molecular patterns (PAMP) to TLR induces the production of reactive oxygen and nitrogen intermediates (ROI and RNI), pro-inflammatory cytokines, and up-regulates expression of co-stimulatory molecules, subsequently initiating the adaptive immunity. In this review, we will summarize the discovery and the critical roles of the TLR family in host defense, briefly allude to signaling mechanisms mediating the response to TLR ligands, and will provide an update on current knowledge regarding the ligand specificity of these receptors and their role in immunity of domestic animals, particularly cattle.