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

Plasmid DNA vaccines against cancer: cytotoxic T-lymphocyte induction against tumor antigens

In recent years, a number of tumor vaccination strategies have been developed. Most of these rely on the identification of tumor antigens that can be recognized by the immune system. DNA vaccination represents one such approach for the induction of both humoral and cellular immune responses against tumor antigens. Studies in animal models have demonstrated the feasibility of utilizing DNA vaccination to elicit protective antitumor immune responses. However, most tumor antigens expressed by cancer cells in humans are weakly immunogenic, and therefore require the development of strategies to potentiate DNA vaccine efficacy in the clinical setting. This review focuses on recent advances in understanding of the immunology of DNA vaccines, as well as strategies used to increase DNA vaccine potency with respect to cytotoxic T-lymphocyte activity.

Donor TLR9 gene tagSNPs influence susceptibility to aGVHD and CMV reactivation in the allo-HSCT setting without polymorphisms in the TLR4 and NOD2 genes

Owing to ethnicity of the population, those best confirmed polymorphisms in the TLR (toll-like receptor)4 and NOD2 genes with significantly prognostic impact on allogeneic hematopoietic SCT (allo-HSCT) seem to be more applicable to Europeans and are nonpolymorphic in the Asian population. The influence of innate immunity gene polymorphisms on the outcomes of allo-HSCT in those populations has been questioned. We evaluated the influence of 10 candidate single nucleotide polymorphisms (SNPs) in the TLR1, TLR2, TLR3, TLR8 and TLR9 genes on the outcomes of allo-HSCT in a Chinese population including 138 pairs of patients and unrelated donors and a second cohort of 102 pairs of patients and HLA-identical sibling donors. We found that two tagSNPs in the TLR9 gene in the donor side, +1174 A/G (rs352139) and +1635 C/T (rs352140), influenced the risk of acute GVHD (aGVHD) and CMV reactivation. Furthermore, the presence of the susceptible haplotype (A-C) in donor may be an informative predicator of worse OS at 5 years compared with those with the G-C and G-T haplotypes (58% vs 82.9%, P=0.024). Our data suggested an unrecognized association between donor TLR9 tagSNPs and the risk of HSCT-related complications in a population without polymorphisms in the TLR4 and NOD2 genes.

The distribution, clearance, and safety of an anti-MMP-9 DNAzyme in normal and MMTV-PyMT transgenic mice

Catalytic oligonucleotides, known as DNAzymes, are a new class of nucleic acid-based gene therapy that have recently been used in preclinical animal studies to treat various cancers. In this study the systemic distribution, pharmacokinetics, and safety of intravenously administered anti-MMP (matrix metalloproteinase)-9 DNAzyme (AM9D) were determined in healthy FVB and in MMTV-polyoma virus middle T (PyMT) transgenic mice bearing mammary tumors. MMP-9 is known to be involved in tumor cell development, angiogenesis, invasion, and metastasis. Sulfur-35 ((35)S) labeled ([(35)S]-AM9D) administered intravenously, without the use of carrier molecules, to healthy and mammary tumor bearing MMTV-PyMT transgenic mice distributed to all major organs. The order of percentages of [(35)S]-AM9D accumulation in different organs of healthy and MMTV-PyMT mice were blood>liver>kidney>lung>spleen>heart and mammary tumor>blood≈liver>kidney>spleen>lung>heart, respectively. The amount of AM9D accumulated in mammary tumors 2 hours post injection was 0.6% and 0.2% higher than in either blood or liver, respectively, and its rate of initial clearance from mammary tissue was at least 50% slower than the other organs. Approximately 43% of the delivered dosage of [(35)S]-AM9D was cleared from the system via feces and urine over a period of 72 hours. No evidence of acute or chronic cytotoxicity, local or widespread, associated with AM9D treatment (up to 75 mg AM9D /kg of body weight) was observed in the organs examined. These data suggest that DNAzyme in general and AM9D in particular can be used systemically as a therapeutic agent to treat patients with breast cancer or other metastatic and surgically inaccessible tumors.

Immunotherapeutic potential of CpG oligodeoxynucleotides in veterinary species

Innate immunity plays a critical role in host defense against infectious diseases by discriminating between self and infectious non-self. The recognition of infectious non-self involves germ-line encoded pattern recognition receptors (PRRs) that recognize pathogen-associated molecular patterns (PAMPs). The PAMPs are the components of pathogenic microbes which include not only the cell wall constituents but also the unmethylated 2'-deoxy-ribo-cytosine-phosphate-guanosine (CpG) motifs. These CpG motifs present within bacterial and viral DNA are recognized by toll-like receptor 9 (TLR9), and signaling by this receptor triggers a proinflammatory cytokine response which, in turn, influences both innate and adaptive immune responses. The activation of TLR9 with synthetic CpG oligodeoxynucleotides (ODNs) induces powerful Th1-like immune responses. It has been shown to provide protection against infectious diseases, allergy and cancer in laboratory animal models and some domestic animal species. With better understanding of the basic biology and immune mechanisms, it would be possible to exploit the potential of CpG motifs for animal welfare. The research developments in the area of CpG and TLR9 and the potential applications in animal health have been reviewed in this article.

Toll-like receptor agonists induce apoptosis in mouse B-cell lymphoma cells by altering NF-κB activation

Toll-like receptor 9 (TLR9) recognizes microbial DNA containing unmethylated cytosyl guanosyl (CpG) sequences, induces innate immune responses, and facilitates antigen-specific adaptive immunity. Recent studies report that in addition to stimulating innate immunity, TLR9 ligands induce apoptosis of TLR9 expressing cancer cells. To understand the mechanism of TLR9-induced apoptosis, we compared the effects of CpG containing oligodeoxynucleotides (CpG ODN) on a mouse B-cell lymphoma line, CH27, with those on mouse splenic B cells. CpG ODN inhibited constitutive proliferation and induced apoptosis in the CH27 B-cell lymphoma line. In contrast, CpG ODN-treated primary B cells were stimulated to proliferate and were rescued from spontaneous apoptosis. The induction of apoptosis required the ODNs to contain the CpG motif and the expression of TLR9 in lymphoma B cells. A decrease in Bcl-xl expression and an increase in Fas and Fas ligand expression accompanied lymphoma B-cell apoptosis. Treatment with the Fas ligand-neutralizing antibody inhibited CpG ODN-induced apoptosis. CpG ODN triggered a transient NF-κB activation in the B-cell lymphoma cell line, which constitutively expresses a high level of c-Myc, while CpG ODN induced sustained increases in NF-κB activation and c-Myc expression in primary B cells. Furthermore, an NF-κB inhibitor inhibited the proliferation of the CH27 B-cell lymphoma line. Our data suggest that the differential responses of lymphoma and primary B cells to CpG ODN are the result of differences in NF-κB activation. The impaired NF-κB activation in the CpG ODN-treated B-cell lymphoma cell line alters the balance between NF-κB and c-Myc, which induces Fas/Fas ligand-dependent apoptosis.

Malaria vaccine adjuvants: latest update and challenges in preclinical and clinical research

There is no malaria vaccine currently available, and the most advanced candidate has recently reported a modest 30% efficacy against clinical malaria. Although many efforts have been dedicated to achieve this goal, the research was mainly directed to identify antigenic targets. Nevertheless, the latest progresses on understanding how immune system works and the data recovered from vaccination studies have conferred to the vaccine formulation its deserved relevance. Additionally to the antigen nature, the manner in which it is presented (delivery adjuvants) as well as the immunostimulatory effect of the formulation components (immunostimulants) modulates the immune response elicited. Protective immunity against malaria requires the induction of humoral, antibody-dependent cellular inhibition (ADCI) and effector and memory cell responses. This review summarizes the status of adjuvants that have been or are being employed in the malaria vaccine development, focusing on the pharmaceutical and immunological aspects, as well as on their immunization outcomings at clinical and preclinical stages.

Early development of the Toll-like receptor 9 agonist, PF-3512676, for the treatment of patients with advanced cancers

BACKGROUND

Unmethylated oligodeoxynucleotides (ODNs) with cytosine-phosphate-guanine (CpG) motifs can potently activate the immune system through Toll-like receptor (TLR) 9. PF-3512676 is a synthetic CpG ODN that induces strong Th1-type immune responses through TLR9 and is now in clinical development.

OBJECTIVE

To review discovery and development of synthetic CpG ODNs and their effects on immune cells and to relate preclinical and early clinical development of PF-3512676.

METHODS

A literature search was performed on databases available through the National Library of Medicine (PubMed), the European Society of Medical Oncology and the American Society of Clinical Oncology.

RESULTS/CONCLUSIONS

Unmethylated CpG motifs were identified as the element of bacillus Calmette-Guérin responsible for immunostimulatory activity. Preclinical studies identified the mechanism of action (i.e., TLR9) and an optimal human sequence for antitumor activity. On the basis of preclinical studies, PF-3512676, a B-class CpG ODN, was selected for further clinical development. Phase I/II clinical trials have shown PF-3512676 to be well tolerated and to have antitumor activity as a single agent in patients with several types of advanced cancer, and to show promise as a vaccine adjuvant.

Chapter seven--Cancer treatment with gene therapy and radiation therapy

Radiation therapy methods have evolved remarkably in recent years which have resulted in more effective local tumor control with negligible toxicity of surrounding normal tissues. However, local recurrence and distant metastasis often occur following radiation therapy mostly due to the development of radioresistance through the deregulation of the cell cycle, apoptosis, and inhibition of DNA damage repair mechanisms. Over the last decade, extensive progress in radiotherapy and gene therapy combinatorial approaches has been achieved to overcome resistance of tumor cells to radiation. In this review, we summarize the results from experimental cancer therapy studies on the combination of radiation therapy and gene therapy.

Strategies for enhancing vaccine-induced CTL antitumor immune responses

Vaccine-induced cytotoxic T lymphocytes (CTLs) play a critical role in adaptive immunity against cancers. An important goal of current vaccine research is to induce durable and long-lasting functional CTLs that can mediate cytotoxic effects on tumor cells. To attain this goal, there are four distinct steps that must be achieved. To initiate a vaccine-induced CTL antitumor immune response, dendritic cells (DCs) must capture antigens derived from exogenous tumor vaccines in vivo or autologous DCs directly loaded in vitro with tumor antigens must be injected. Next, tumor-antigen-loaded DCs must activate CTLs in lymphoid organs. Subsequently, activated CTLs must enter the tumor microenvironment to perform their functions, at which point a variety of negative regulatory signals suppress the immune response. Finally, CTL-mediated cytotoxic effects must overcome the tolerance induced by tumor cells. Each step is a complex process that may be impeded in many ways. However, if these steps happen under appropriate regulation, the vaccine-induced CTL antitumor immune response will be more successful. For this reason, we should gain a better understanding of the basic mechanisms that govern the immune response. This paper, based on the steps necessary to induce an immune response, discusses current strategies for enhancing vaccine-induced CTL antitumor immune responses.

CpG plus radiotherapy: a review of preclinical works leading to clinical trial

Studies performed three decades ago in our laboratory supported the hypothesis that radiation efficacy may be augmented by bacterial extracts that stimulate non-specific systemic antitumor immune responses. Application to the clinic was halted by unacceptable side effects and toxicities resulting from exposure to whole bacterial pathogens. Later scientific advances demonstrated that DNA isolated from bacteria was immunostimulatory and could be reproduced with synthetic oligodeoxynucleotides (ODNs), thus fueling the transition from bugs to drugs. Unmethylated CpG motifs within bacterial DNA induce activation of Toll-like receptor 9 and subsequently activate antigen-specific cellular immune responses. CpG ODNs have demonstrated favorable toxicity profiles in phase I clinical trials. We showed that this potent immunoadjuvant can be used in combination with radiation therapy to enhance local and systemic responses of several murine tumors. Studies demonstrated that enhanced tumor response is mediated in part by the host immune system. Antitumor efficacy was diminished in immunocompromised mice. Animals cured by combination of radiation and CpG ODN were resistant to subsequent tumor rechallenge. This body of work contributes to our understanding of the dynamic interplay between tumor irradiation and the host immune system and may facilitate translation to clinical trials.

[Biologic modulation of ionizing radiation by Toll-like receptors agonists: towards an increase in the therapeutic index of radiotherapy?]

Toll-like receptors are ubiquitous and very well conserved throughout evolution, with important functions mediating innate and adaptative immunological mechanisms. The importance of these receptors and their agonists has been recently pointed out in immunology and cancerology, although the accurate underlying mechanisms are still under investigation. The association of agonists of these receptors with ionizing radiation has been studied in preclinical experiments with promising results. Part of these compounds is flagellin, which seems to be able to modulate the radiosensitivity of both tumors and healthy tissues.

Therapeutic administration of a synthetic CpG oligodeoxynucleotide triggers formation of anti-CpG antibodies

The synthetic oligodeoxynucleotide CpG 7909, which contains unmethylated cytosine/guanine (CpG) motifs, has potent immunostimulatory effects when coadministered with NY-ESO-1 peptides or recombinant NY-ESO-1 protein, resulting in an enhanced cellular and humoral immune response against the vaccine antigen. In this study, we report the development of anti-CpG-ODN antibodies in 21 of 37 patients who received CpG 7909 either alone or as a vaccine adjuvant. Specific anti-CpG immunoglobulin G (IgG) antibody titers ranged from 1:400 to 1:100,000. The anti-CpG antibodies cross-reacted with other synthetic CpG-ODNs but not with the DNA of mixed bacterial vaccine and were shown to be phosphorothioate backbone specific. Vaccine-related severe side effects observed in some patients were most likely not related to the development of anti-CpG antibodies. In addition, anti-CpG antibodies did not have negative effects on the vaccine immune response. These results show that anti-CpG antibodies develop in humans against short unmethylated CpG dinucleotide sequences after administration of CpG 7909. Our data therefore substantiate the potency of CpG 7909 to directly stimulate human B-cells and suggest that anti-CpG antibody monitoring should be a part of ongoing and planned clinical trials with CpG-ODNs.

A phase III randomized study of gemcitabine and cisplatin with or without PF-3512676 (TLR9 agonist) as first-line treatment of advanced non-small-cell lung cancer

BACKGROUND

This open-label phase III study assessed the addition of Toll-like receptor 9-activating oligodeoxynucleotide PF-3512676 to gemcitabine/cisplatin chemotherapy in patients with non-small-cell lung cancer (NSCLC).

PATIENTS AND METHODS

Chemotherapy-naive patients with stage IIIB or IV NSCLC were randomized (1:1) to receive six or fewer 3-week cycles of i.v. gemcitabine (1250 mg/m2 on days 1 and 8) and cisplatin alone (75 mg/m2 on day 1, control arm) or combined with s.c. PF-3512676 0.2 mg/kg on days 8 and 15 of each chemotherapy cycle and weekly thereafter until progression or unacceptable toxicity (experimental arm). No crossover was planned. The primary end point was overall survival (OS).

RESULTS

A total of 839 patients were randomized. Baseline demographics were well balanced. Median OS (11.0 versus 10.7 months; P=0.98) and median progression-free survival (PFS) (both 5.1 months) were similar between groups. Grade≥3 hematologic adverse events (AEs), injection-site reactions, and influenza-like symptoms were more frequently reported among patients receiving PF-3512676. At the first-interim analysis, the Data Safety Monitoring Committee recommended study discontinuation. Administration of PF-3512676 was halted based on efficacy futility and increased grade≥3 AEs (experimental arm).

CONCLUSIONS

Addition of PF-3512676 to gemcitabine/cisplatin chemotherapy did not improve OS or PFS but did increase toxicity.

Toll-like receptor 4 stimulation initiates an inflammatory response that decreases cardiomyocyte contractility

Toll-like receptors (TLRs) have been identified as primary innate immune receptors for the recognition of pathogen-associated molecular patterns by immune cells, initiating a primary response toward invading pathogens and recruitment of the adaptive immune response. TLRs, especially Toll-like receptor 4 (TLR4), can also be stimulated by host-derived molecules and are expressed in the cardiovascular system, thus acting as a possible key link between cardiovascular diseases and the immune system. TLR4 is involved in the acute myocardial dysfunction caused by septic shock and myocardial ischemia. We used wild-type (WT) mice, TLR4-deficient (TLR4-knockout [ko]) mice, and chimeras that underwent myeloablative bone marrow transplantation to dissociate between TLR4 expression in the heart (TLR4-ko/WT) and the immunohematopoietic system (WT/TLR4-ko). Following lipopolysaccharide (LPS) challenge (septic shock model) or coronary artery ligation, myocardial ischemia (MI) model, we found WT/TLR4-ko mice challenged with LPS or MI displayed reduced cardiac function, increased myocardial levels of interleukin-1β and tumor necrosis factor-α, and upregulation of mRNA encoding TLR4 prior to myocardial leukocyte infiltration. The cardiac function of TLR4-ko or WT/TLR4-ko mice was less affected by LPS and demonstrated reduced suppression by MI compared with WT. These results suggest that TLR4 expressed in the cardiomyocytes plays a key role in this acute phenomenon.

CpG oligodeoxynucleotide 1826 enhances the Lewis lung cancer response to radiotherapy in murine tumor

CpG oligodeoxynucleotides (ODNs) are synthetic DNA sequences containing unmethylated cytosine-guanine motifs with potent immune modulatory effects. Via Toll-like receptor 9 agonists of dendritic cells and B cells, CpG ODNs induce cytokines, activate natural killer cells, and elicit vigorous T-cell responses that lead to significant antitumor effects. On the basis of these properties of CpG ODNs, a previous study has tested that they could enhance tumor response to single-dose radiotherapy. The present study extended this finding to the fractionated radiotherapy of the Lewis lung cancer and assessed the ability of CpG ODN 1826 to increase the immune function of mice and the effect of CpG ODN 1826 on the apoptosis of Lewis lung cancer. First, tumor growth delay was observed, and the enhancement ratio of CpG ODN 1826 was found to be 2.4; decreased tumor weight was found after combined treatments with CpG ODN 1826 and X-ray radiation compared with either treatment alone (P < 0.01). Second, enhanced cell apoptotic index was found after combined treatments with CpG ODN 1826 and X-ray radiation compared with either treatment alone (p < 0.01). Increased tumor necrosis factor-α and decreased interleukin-10 concentration in serum and enhanced spleen exponent were observed after combined treatments with CpG ODN 1826 and X-ray radiation compared with X-ray radiation treatment alone (p < 0.01). Results suggest that CpG-ODN1826 can increase the radiosensitivity of Lewis lung cancer, which may be associated with stimulation of immune system and enhanced cell apoptosis.

TLR9 agonists oppositely modulate DNA repair genes in tumor versus immune cells and enhance chemotherapy effects

Synthetic oligodeoxynucleotides expressing CpG motifs (CpG-ODN) are a Toll-like receptor 9 (TLR9) agonist that can enhance the antitumor activity of DNA-damaging chemotherapy and radiation therapy in preclinical mouse models. We hypothesized that the success of these combinations is related to the ability of CpG-ODN to modulate genes involved in DNA repair. We conducted an in silico analysis of genes implicated in DNA repair in data sets obtained from murine colon carcinoma cells in mice injected intratumorally with CpG-ODN and from splenocytes in mice treated intraperitoneally with CpG-ODN. CpG-ODN treatment caused downregulation of DNA repair genes in tumors. Microarray analyses of human IGROV-1 ovarian carcinoma xenografts in mice treated intraperitoneally with CpG-ODN confirmed in silico findings. When combined with the DNA-damaging drug cisplatin, CpG-ODN significantly increased the life span of mice compared with individual treatments. In contrast, CpG-ODN led to an upregulation of genes involved in DNA repair in immune cells. Cisplatin-treated patients with ovarian carcinoma as well as anthracycline-treated patients with breast cancer who are classified as "CpG-like" for the level of expression of CpG-ODN modulated DNA repair genes have a better outcome than patients classified as "CpG-untreated-like," indicating the relevance of these genes in the tumor cell response to DNA-damaging drugs. Taken together, the findings provide evidence that the tumor microenvironment can sensitize cancer cells to DNA-damaging chemotherapy, thereby expanding the benefits of CpG-ODN therapy beyond induction of a strong immune response.

Immunotherapy for cutaneous malignancy

BACKGROUND

Immunotherapy for cutaneous malignancy involves manipulating the immune system to treat and prevent skin cancer. Although initial efforts were fraught with low success rates and technical challenges, more-recent endeavors have yielded response rates approaching 50% for treating metastatic melanoma. Many of these advances are a result of increasing knowledge of the immune system's intricacies and continued progress in laboratory techniques.

OBJECTIVE

To review our current understanding of the skin immune system and discuss how these factors contribute to the host response to malignancy and to report the current state of immunotherapeutic techniques.

MATERIALS AND METHODS

An extensive PubMed literature search was conducted in topics involving immunotherapy with specific relevance to cutaneous malignancy using the MeSH terms "immunotherapy" and "skin cancer."

RESULTS

Despite initially poor patient responses to these treatment modalities, recent gains in scientific knowledge and clinical intervention protocols have brought immunotherapy to the forefront of prospective skin cancer therapeutics, particularly for advanced melanoma.

CONCLUSIONS

Current treatment options for advanced cutaneous malignancies such as melanoma are low in efficacy. Immunotherapies have the potential to provide novel approaches to address this, particularly when used in combination. The authors have indicated no significant interest with commercial supporters.

Antitumor activity mediated by CpG: the route of administration is critical

Unmethylated CpG oligodeoxynucleotides (CpG) are synthetic toll-like receptor 9 agonists that activate innate immune cells and which have been tested as an immune therapy in a number of cancer clinical trials. Although some antitumor immune responses have been reported, so far the majority of studies have failed to show significant clinical responses to CpG. Here we showed that the route of administration is critical to the antitumor activity of CpG. Although intravenous (i.v.) injection of CpG was capable of inducing the activation and expansion of tumor antigen-specific T cells, most of these activated T cells failed to migrate to tumor sites. By contrast, intratumoral (i.t.) injection of CpG led to extensive tumor infiltration of antigen-specific T cells and subsequent tumor suppression. We further showed that very high levels of inflammatory chemokines [regulated upon activation, normal T-cell expressed, and secreted (RANTES), interferon-inducible protein-10 (IP-10), monocyte chemoattractant protein-1, monocyte chemotactic protein (MCP5), macrophage inflammatory proteins (MIP1α, and MIP1β)] were induced in the tumor microenvironment after i.t. CpG injection, compared with administration by the i.v. route. It is interesting to note that, in vivo depletion of plasmacytoid dendritic cells greatly reduced the levels of chemokines induced; also, T-cell accumulation and antitumor effect were impaired. We also showed that i.t. but not i.v. CpG injection induced a broad antigen-specific T-cell response against tumor-derived antigens. Collectively, our data provides evidence that the route of CpG administration is a critical factor in mediating antitumor activity. By inducing localized inflammatory signals at tumor sites, i.t. CpG effectively promotes the migration, activation and function of immune cells, ultimately leading to improved tumor control.

Targeted chemoimmunotherapy using drug-loaded aptamer-dendrimer bioconjugates

We reported an innovative, targeted chemoimmuno drug-delivery system. Although chemoimmunotherapy, as an alternative to or in combination with conventional therapeutic systems, has been in the forefront of recent oncological research, as presently configured, such systems face several major obstacles for efficient clinical application. Here, we establish a novel nano-platform for effective chemoimmunotherapy designed to overcome the drawbacks of conventional cancer therapies, describing a delivery system based on a dendrimer and a single-strand DNA-A9 PSMA (prostate-specific membrane antigen) RNA aptamer hybrid. Employing these vehicles, we demonstrate the promising possibility of this chemoimmuno therapeutic system against prostate cancer in in vivo and in vitro models.

Improvement of the immunity of pig to Hog cholera vaccine by recombinant plasmid with porcine interleukin-6 gene and CpG motifs

In order to observe the dosage-effect of recombinant pig interleukin-6 gene and CpG motifs on the immune responses of swine to vaccine, a novel recombinant eukaryotic VPIL6C plasmid was packed with chitosan nanoparticles (CNP) prepared by ionic cross linkage, which contains pig interleukin-6 gene and immunostimulatory sequence consisted of 11 CpG motifs. CNP-VRIL6C was then utilized to inoculate 30-day-old piglets intramuscularly at the dosage of 0.5, 1.0 and 1.5mg/per capita, respectively. Meanwhile, the piglets were injected with attenuated classical Hog cholera vaccine and designated as A1, A2 and A3 group. The blood was weekly collected from the piglets after vaccination to detect the changes of immunoglobulins, specific antibody, interleukins, IFN-γ and immune cells. The results were found that compared to those of the control piglets injected with VR1020-CNP, the content of IgG, IgA and IgM, specific antibodies, IL-2, IL-6 and IFN-γ significantly increased in the sera from the treated three groups from 14 to 70 days after vaccination (P<0.05); the number of T(H), T(C) and CD3(+) positive T cells raised obviously in the blood of VPIL6C treated piglets (P<0.05). Also the above immune indexes of A1 group were significantly lower to different extent in comparison with those of A2 and A3 group from 14 to 56 days post inoculation (P>0.05). Moreover, the lymphocytes also remarkably elevated in the treated groups (P<0.05). These indicate that VPIL6C entrapped with CNP is a novel effective adjuvant to boost the humoral and cellular immunity of pig to Hog cholera, implying it's potentiality to enhance the resistance of pig against infectious diseases.

Toll-like receptor 9 agonists as cancer therapeutics

INTRODUCTION

Toll-like receptor 9 (TLR9) agonists, commonly referred to as CpG oligodeoxynucleotides (ODN), have been added to the arsenal of anti-cancer drugs as monotherapy or in combination with chemotherapy, radiotherapy and other immunotherapeutic approaches as they increase antigen presentation and boost anti-tumor T- and B-cell responses. Several synthetic TLR9 agonists have been developed for clinical grade use and displayed substantial efficacy in the preclinical and clinical models.

AREAS COVERED

This review summarizes TLR9 signaling and the impact of TLR9 agonists on the immune response. The most recent experimental and clinical data are analyzed as well as the development of new TLR9 agonists in current clinical trials.

EXPERT OPINION

Application of TLR9 agonists, in particular, combination strategies with chemo- or radiotherapy seem a promising and efficient immunotherapeutic approach in cancer patients even with refractory disease. Simultaneous application of TLR9 agonists aims at supporting the patient's immune response and overcoming specific immunosuppressant strategies developed by tumors. Combinatory approaches of the future might also seek for synergism of TLR9 agonists with other immunomodulatory strategies such as B-cell activation using the CD40-CD40L system.

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.

Neoadjuvant immunotherapy enhances radiosensitivity through natural killer cell activation

We investigated whether natural killer (NK) cells in the tumor microenvironment have a radiosensitization effect. The radiosensitization effect of combined CpG and Herceptin((R)) (Genentech, Inc., South San Francisco, CA) (CpG/Herceptin), given before or after radiation, was evaluated by using a murine colon cancer cell line overexpressing human HER2/neu, CT26HER2/neu. In vitro radiosensitization effects were investigated by coculture of CT26HER2/neu with splenocytes, CpG, and Herceptin before applying radiation. Tumor cells, cocultured with CpG-pretreated splenocytes and Herceptin, were more vulnerable to radiation damage. In BALB/c mice injected with CT26HER2/neu, CpG/Herceptin administered before radiotherapy was associated with a better retardation of tumor growth than when administered after radiotherapy. The radiosensitization effect was significantly abrogated by NK-cell depletion, indicating that NK cells play an essential role in it. Further, surviving mice treated with CpG or CpG/Herceptin and reverse transcriptase were resistant to renewed tumor challenge, suggesting the presence of an induced immune response to the tumor. Neoadjuvant immunotherapy with CpG/Herceptin may improve response to radiotherapy of HER2/neu-expressing tumors.

Experimental approaches for the treatment of malignant gliomas

Malignant gliomas, which include glioblastomas and anaplastic astrocytomas, are the most common primary tumors of the brain. Over the past 30 years, the standard treatment for these tumors has evolved to include maximal safe surgical resection, radiation therapy and temozolomide chemotherapy. While the median survival of patients with glioblastomas has improved from 6 months to 14.6 months, these tumors continue to be lethal for the vast majority of patients. There has, however, been recent substantial progress in our mechanistic understanding of tumor development and growth. The translation of these genetic, epigenetic and biochemical findings into therapies that have been tested in clinical trials is the subject of this review.

Targeted microbeads for attraction and induction of specific innate immune response in the tumor microenvironment

Antitumor activity of molecules and cells of the innate immune system has been reported. Here we propose a method for targeting preferred innate immune cells and magnifying their tumoricidal effect at the tumor microenvironment, by modular multiple-component complexes (termed TILTAN). As a model, micro-scale complexes were assembled carrying monoclonal anti-HER2 antibodies, lipopolysaccharide and/or mannose. The complexes showed high binding capacity to HER2-positive cancer cells in vitro, high induction of interleukin-1 RNA transcription by the activated monocytes and ability to mediate monocytes' attachment to HER2-positive cells. TILTAN treatment was found safe in in vivo testing and induced change in interleukin-1 RNA transcription in tumors xenografts. We thus present a new vision of targeting a desired innate immune response to the tumor microenvironment.

CpG oligodeoxynucleotides as TLR9 agonists: therapeutic applications in cancer

Toll-like receptors (TLRs) are part of the innate immune system, and they belong to the pattern recognition receptors (PRR) family. The PRR family is designed to recognize and bind conserved pathogen-associated molecular patterns, which are not generated by the host and are restricted and essential to micro-organisms. TLR9, which recognizes unmethylated CpG (cytosine guanosine dinucleotide), is a very promising target for therapeutic activation. Stimulation of TLR9 activates human plasmacytoid dendritic cells and B cells, and results in potent T helper-1 (T(h)1)-type immune responses and antitumor responses in mouse tumor models and in patients. Several pharmaceutical companies, such as Pfizer, Idera, and Dynavax, are developing CpG oligodeoxynucleotides (ODNs) for the treatment of cancer, along with other conditions, such as infections and allergy. CpG ODNs have shown promising results as vaccine adjuvants and in combination with cancer immunotherapy. Several TLR9 agonists are being developed and have entered clinical trials to evaluate their safety and efficacy for the treatment of several hematopoietic and solid tumors. In this review, we discuss the use of CpG ODNs in several phase I and II clinical trials for the treatment of NHL, renal cell carcinoma, melanoma, and non-small cell lung cancer, either alone or in combination with other agents.

Targeting the immune system in non-small-cell lung cancer: bridging the gap between promising concept and therapeutic reality

Developing effective immunotherapy for lung cancer is a daunting but hugely attractive challenge. Until recently, non-small-cell lung cancer (NSCLC) was thought of as a nonimmunogenic tumor, but there is now evidence highlighting the integral role played by both inflammatory and immunologic responses in lung carcinogenesis. Despite recent encouraging preclinical and phase I/II data, there are a paucity of phase III trials showing a clear clinical benefit for vaccines in lung cancer. There are many difficulties to overcome before the development of a successful therapy. Perhaps a measurable immune response may not translate into a clinically meaningful or radiologic response. Patient selection may also be a problem for ongoing clinical studies. The majority of trials for lung cancer vaccines are focused on patients with an advanced stage of the disease; however, the ideal candidates may be patients with a lower tumor burden and stage I or II disease. Selecting the exact antigens to target is also difficult. It will likely require multiple epitopes of a diverse set of genes restricted to multiple haplotypes to generate a truly effective vaccine that is able to overcome the various immunologic escape mechanisms that tumors use. This review discusses the most promising active immunotherapy using protein/peptide vaccines, whole cell vaccines, and dendritic cell vaccines and examines current phase I and II clinical trial data on some novel nonspecific immunomodulating agents.

Intracerebral administration of CpG oligonucleotide for patients with recurrent glioblastoma: a phase II study

Immunostimulating oligodeoxynucleotides containing CpG motifs (CpG-ODN) have shown promising efficacy in cancer models when injected locally. In a phase I clinical trial, intratumoral infusions of CpG-ODN in glioblastoma (GBM) patients were well tolerated at doses up to 20 mg. This phase II trial was designed to study the efficacy of a local treatment by CpG-ODN in patients with recurrent GBMs. Patients with recurrent GBM occurring at least 3 months after radiotherapy, and previously treated with 1 or 2 regimens of chemotherapy received 20 mg of CpG-ODN (CpG-28) by convection-enhanced delivery. The primary endpoint was the percentage of patients without tumor progression 6 months after inclusion. Secondary endpoints were tolerance, survival, and radiological response. Thirty-four patients were enrolled in two centers between November 2004 and March 2006. Thirty-one patients received CpG-ODN treatment. The progression-free survival (PFS) at 6 months was 19%. One partial response and 3 minor responses were observed. The median overall survival was 28 weeks. Eight patients (24%) were alive 1 year after inclusion and 5 patients (15%) were alive after 2 years. Treatment was usually well tolerated. As reported previously, the most common toxicities were lymphopenia, mild fever, seizures, and transient neurological worsening. Despite a few cases showing a radiological response, CpG-28 showed modest activity on the 6-month PFS in this patient population. The molecular or clinical characteristics of a subgroup of patients that could potentially benefit from such an approach remain to be defined.

Ascites regression and survival increase in mice bearing advanced-stage human ovarian carcinomas and repeatedly treated intraperitoneally with CpG-ODN

Tumor cell growth, even in advanced stages of ovarian cancer, is nearly always restricted to the peritoneal cavity; therefore, repeated intraperitoneal injections of oligodeoxynucleotides containing dinucleotides with unmethylated CpG motifs (CpG-ODN) recruiting and activating innate effector cells throughout the abdominal cavity to the tumor site might control tumor cell growth and ascites formation. After a single CpG-ODN treatment, in IGROV-1 ovarian tumor ascites-bearing athymic mice, the number of tumor cells declined rapidly and markedly, and ascites volumes declined shortly after treatment (5 h), increasing thereafter at a slower rate than in controls. When administered every 7 days for 4 weeks, CpG-ODN had only a marginal effect on survival time, whereas administration 5 days/wk for 3 or 4 weeks led to a significantly increased survival time as compared with controls (P<0.005) and completely controlled ascites growth without apparent toxicity, although a disorganization of lymphoid organs was observed. Bio-plex assay of cytokine levels in peritoneal fluid of ascites-bearing mice after CpG-ODN treatment revealed an increase in interleukin (IL)-6, IL-10, IL-12, and interferon-gamma at 24 hours, which returned to control mice levels at 48 to 96 hours, whereas the high levels of angiogenic factors remained unchanged. Depletion of natural killer or monocytes/macrophages only slightly influenced the CpG-ODN-induced reduction of ascites tumor cells, indicating that the antitumor activity might not be related to a specific cell/cytokine but rather to the repertoire of cells and cytokines accumulated in the peritoneal cavity. Thus, our data suggest a relevant role for repeated activation of cells and cytokines of innate immunity in the therapy of ovarian cancer patients with malignant ascites.

Stimulation of the immune system by therapeutic antisense oligodeoxynucleotides and small interfering RNAs via nucleic acid receptors

Most of the therapeutic applications for synthetic oligodeoxynucleotides (ODN) and oligoribonucleotides (ORN) relate to mechanisms of manipulating gene expression based on Watson-Crick base pairing to endogenous nucleic acids. However, in recent years it has become apparent that the immune system has evolved defense mechanisms against infections that are based on the detection of infecting viral and bacterial nucleic acids. In some cases, synthetic ODN and ORN can trigger these defenses and, therefore, can interfere with or distort the mechanism of action of antisense ODN or small interfering RNAs.

HER-2/neu (657-665) represents an immunogenic epitope of HER-2/neu oncoprotein with potent antitumor properties

The HER-2/neu oncoprotein is a promising cancer vaccine target. We describe herein a novel HLA-A2.1-restricted epitope, encompassing amino acids 657-665 (AVVGILLVV), which is naturally presented by human breast and ovarian cell lines. HER-2/neu(657-665), [HER-2(9(657))], binds with high affinity to HLA-A2.1 molecules as revealed by a prediction algorithm (SYFPEITHI) and in functional assays. This peptide was found to be immunogenic in HLA-A2.1 transgenic (HHD) mice inducing peptide-specific CTL, which responded with increased IFNgamma production, degranulation, and in vitro as well as in vivo cytotoxicity. Most important, HER-2(9(657)) functioned as a therapeutic vaccine by enabling HHD mice to reject established transplantable tumors. Cured mice resisted tumor growth when re-challenged with the same tumor, demonstrating the capacity of HER-2(9(657)) to generate tumor-specific memory immune response. Finally, this peptide was also found to be immunogenic in PBMCs from HLA-A2.1(+) patients with HER-2/neu(+) breast cancer. Our data encourage further exploitation of HER-2(9(657)) as a promising candidate for peptide-based cancer vaccines.

Immunotherapeutic applications of CpG oligodeoxynucleotide TLR9 agonists

Toll-like receptor 9 (TLR9) agonists have demonstrated substantial potential as vaccine adjuvants, and as mono- or combination therapies for the treatment of cancer and infectious and allergic diseases. Commonly referred to as CpG oligodeoxynucleotides (ODN), TLR9 agonists directly induce the activation and maturation of plasmacytoid dendritic cells and enhance differentiation of B cells into antibody-secreting plasma cells. Preclinical and early clinical data support the use of TLR9 agonists as vaccine adjuvants, where they can enhance both the humoral and cellular responses to diverse antigens. In mouse tumor models TLR9 agonists have shown activity not only as monotherapy, but also in combination with multiple other therapies including vaccines, antibodies, cellular therapies, other immunotherapies, antiangiogenic agents, radiotherapy, cryotherapy, and some chemotherapies. Phase I and II clinical trials have indicated that these agents have antitumor activity as single agents and enhance the development of antitumor T-cell responses when used as therapeutic vaccine adjuvants. CpG ODN have shown benefit in multiple rodent and primate models of asthma and other allergic diseases, with encouraging results in some early human clinical trials. Although their potential clinical contributions are enormous, the safety and efficacy of these TLR9 agonists in humans remain to be determined.

Lipid-based delivery of CpG oligonucleotides enhances immunotherapeutic efficacy

There has been significant interest in the potential of cytosine-guanine (CpG) containing oligodeoxynucleotides (ODN) as an immunotherapy for malignant, infectious and allergic diseases. While human trials have yielded promising results, clinical use of free CpG ODN still faces several challenges which limit their effectiveness. These include suboptimal in vivo stability, toxicity, unfavorable pharmacokinetic/biodistribution characteristics, lack of specificity for target cells and the requirement for intracellular uptake. To overcome these challenges, optimized lipid-based delivery systems have been developed to protect the CpG ODN payload, modify their circulation/distribution so as to enhance immune cell targeting and facilitate intracellular uptake. Ultimately, lipid-mediated delivery has the capacity to increase the immunopotency of CpG ODN and enhance their prophylactic or therapeutic efficacy in a range of diseases. Lipid-encapsulation provides a feasible strategy to optimize the immunostimulatory activity and immunotherapeutic efficacy of CpG ODN, thereby allowing their full clinical potential to be realized.

TLR9-activating DNA up-regulates ZAP70 via sustained PKB induction in IgM+ B cells

In the past, ZAP70 was considered a T cell-specific kinase, and its aberrant expression in B-CLL cells was interpreted as a sign of malignant transformation and dedifferentiation. It was only recently that ZAP70 was detected in normal human B cells. In this study, we show that TLR9-activated B cells resemble B-cell chronic lymphocytic leukemia cells with regard to CD5, CD23, CD25, and heat shock protein 90 expression. Furthermore, stimulatory CpG and GpC DNA oligonucleotides target CD27(+)IgM(+) and CD27(-)IgM(+) B cells (but not IgM(-) B cells) and enhance ZAP70 expression predominantly in the IgM(+)CD27(+) B cell subset. ZAP70 is induced via activation of TLR-7 or -9 in a MyD88-dependent manner, depends on protein kinase B (PKB)/mammalian target of rapamycin signaling and is rapamycin sensitive. Furthermore, ZAP70 expression levels correlate with induction of cyclin A2, prolonged B cell proliferation, and sustained induction of PKB. These events are not observed upon CD40 ligation. However, this deficit can be overcome by the expression of constitutively active PKB, given that CD40 ligation of PKB-transgenic B cells induces B cell proliferation and ZAP70 expression. These results highlight a major difference between CD40- and TLR-7/9-mediated B cell activation and suggest that ZAP70 expression levels in B cells give an estimate of the proliferative potential and the associated PKB availability.

Therapeutic strategies for targeting mononuclear phagocytes in cancer

The initiation and progression of cancer is dependent on factors both intrinsic and extrinsic to the malignant cells. Stromal, vascular endothelial, and inflammatory cells are the principal normal populations that support tumors by supplying factors and nutrients. The mononuclear phagocyte lineage, which includes monocytes, macrophages, and dendritic cells is of particular clinical interest because lineage members can enhance tumor angiogenesis and metastasis, or alternately contribute to tumor destruction. Thus therapies that regulate these cells represent an innovative approach for improving patient survival in childhood cancer.

Immunotherapy for advanced melanoma

Immunotherapy for melanoma has undergone significant change since the first attempts to treat patients with high dose IL-2. Herein, strategies to boost patient antitumor immunity through vaccination, treatment with agents that augment host immunity, and adoptive cell transfer will be discussed. The first two strategies have yielded only limited clinical success, but adoptive cell transfer therapy, particularly following a lymphodepleting, preconditioning regimen has resulted in objective response rates approaching 50%. For a number of reasons, lymphodepletion appears to be critical for maintenance of circulating antitumor T cells following adoptive cell transfer. Balancing antitumor efficacy, autoimmunity, and reconstitution of a functioning immune system remain challenging and potentially life-threatening issues.

Eradication of ovarian tumor xenografts by locoregional administration of targeted immunotherapy

PURPOSE

Oligodeoxynucleotides containing unmethylated CpG motifs (CpG-ODN) are potent activators of innate and adaptive immunity. Recognition of CpG-ODN is mediated by Toll-like receptor 9 expressed by immune cells, endothelial and epithelial cells, and fibroblasts. We examined the antitumor effect of CpG-ODN and the role of administration route on human ovarian cancers growing in the peritoneal cavity of nude mice.

EXPERIMENTAL DESIGN

Mice implanted i.p. with human ovarian carcinoma cells were treated i.p., s.c., or i.v. and assessed for survival and tumor-free incidence. Peritoneal washings were analyzed for keratinocyte chemokine production and for functional and phenotypic profiles as indicators of the cell types involved in mediating the antitumor effects.

RESULTS

IGROV-1-bearing mice treated i.p. survived significantly longer than those treated i.v. or s.c. (P=0.0005), and nearly half of them (8 of 17) were tumor-free by the end of the experiment, a rate never achieved using a variety of chemotherapeutic drugs. High rates of tumor-free mice were observed in three other ovarian tumor xenografts treated i.p. Compared with peritoneal washings of mice treated s.c. or i.v., those from mice treated i.p. showed the highest level of serum and tissue keratinocyte chemokine, the highest number of natural killer cells and neutrophils, and the highest antiproliferative activity in vitro.

CONCLUSIONS

The superior antitumor effect obtained by locoregional administration of CpG-ODN in i.p. tumor-bearing mice with a limited adaptive immune response points to the importance of innate effector cells amplification at the site of tumor growth and suggests the promise of i.p. CpG-ODN in clinical trials for ovarian cancer.

Randomized phase II trial of a toll-like receptor 9 agonist oligodeoxynucleotide, PF-3512676, in combination with first-line taxane plus platinum chemotherapy for advanced-stage non-small-cell lung cancer

PURPOSE

This study assessed the efficacy of the combination of standard taxane plus platinum chemotherapy with the synthetic Toll-like receptor 9-activating oligodeoxynucleotide PF-3512676 in patients with non-small-cell lung cancer (NSCLC).

PATIENTS AND METHODS

Chemotherapy-naive patients with stage IIIB to IV NSCLC were randomly assigned (one to two ratio) to receive four to six cycles of taxane/platinum chemotherapy alone or with 0.2 mg/kg of subcutaneous PF-3512676 on days 8 and 15 of each 3-week cycle. The primary end point was objective response rate (ORR).

RESULTS

Baseline demographics were similar between treatment arms, although significantly more patients in the PF-3512676 arm had stage IV disease (85% compared with 62% in the chemotherapy-alone arm). The modified intent-to-treat analysis (n = 111) demonstrated a 38% ORR (confirmed and unconfirmed) in the PF-3512676 arm (n = 74) and 19% in the chemotherapy-alone arm (n = 37) by investigator evaluation. Blinded, independent radiologic review for 90 patients showed a similar trend in confirmed response rate (19% and 11%, respectively). Median survival was 12.3 months in the PF-3512676 arm and 6.8 months in the chemotherapy-alone arm, and 1-year survival was 50% and 33%, respectively. Mild to moderate local injection site reactions and flu-like symptoms were the most common PF-3512676-related adverse events, but grade 3/4 neutropenia, thrombocytopenia, and anemia were all reported more commonly for patients in the PF-3512676 arm.

CONCLUSION

The addition of PF-3512676 to taxane plus platinum chemotherapy for first-line treatment of NSCLC improves objective response and may improve survival. Confirmatory phase III trials are ongoing.

Tumor destruction using electrochemotherapy followed by CpG oligodeoxynucleotide injection induces distant tumor responses

PURPOSE

Electrochemotherapy (ECT) is an effective local therapy of human cutaneous cancers but has no effect on distant untreated tumors. We addressed whether tumor-associated antigens released after ECT could induce an efficient systemic immunity when associated with an appropriate immunoadjuvant.

METHODS AND RESULTS

We first studied the nature of the cellular recruitment and the expression of various toll-like receptors (TLRs) in tumors treated by ECT. We found that ECT induced a massive recruitment of CD11c and CD11b positive cells in the tumors and a strong increase of TLR9 expression. We then tested antitumor effects of the combination: ECT followed by TLR-9 ligands, CpG oligodeoxynucleotides (CpG ODN), in three murine tumor models. We found that this combination triggered both potent local synergistic antitumor effects, on the ipsi-lateral ECT-treated tumor, and more interestingly, a systemic antitumor response on the contra-lateral untreated tumor, in the three models. The systemic protection was T-cell dependent as it was not observed in nude littermates. The combination induced tumor-specific T cell effectors in the tumor-draining lymph nodes and in the spleen which secreted significantly more gamma-interferon upon activation than with ECT or CpG ODN alone.

CONCLUSIONS

Our data show that ECT and CpG ODN synergize and induce a significant increase of the local effect and a systemic T-dependent antitumor response. Such combination constitutes a potential innovative vaccination strategy using in situ tumor-associated antigens that could eventually be translated into the clinic.

CpG oligonucleotides enhance proliferative and effector responses of B Cells in HIV-infected individuals

Stimulation through TLR represents a new therapeutic approach for enhancing Ab responses to vaccination. Considering that Ab responses are decreased in HIV disease and that B cells express TLR9 and respond to TLR9 agonists, we investigated the responsiveness of B cell subpopulations from HIV-infected and uninfected individuals to the TLR9 agonist CpG oligonucleotide type B (CpG-B) in the presence and absence of BCR ligation and T cell help (CD40L). CpG-B was equally effective in stimulating the proliferation of naive B cells of HIV-infected individuals and HIV-negative individuals, and, when combined with BCR and CD40 ligation, cytokine secretion by naive B cells was also comparable in HIV-infected and uninfected individuals. In contrast, CD27(+) memory/activated B cells of HIV-infected individuals with active disease were less responsive to CpG-B in terms of proliferation and cytokine secretion when compared with CD27(+) B cells of HIV-negative and HIV-infected individuals whose viremia was controlled by antiretroviral therapy. These findings suggest that despite abnormalities in memory B cells of HIV-infected individuals with active disease, naive B cells of HIV-infected individuals, irrespective of disease status, can respond to TLR9 agonists and that the incorporation of such agents in vaccine formulations may enhance their Ab responses to vaccination.

Synthetic oligonucleotides as modulators of inflammation

Synthetic oligodeoxynucleotides (ODN) containing unmethylated CpG motifs mimic the immunostimulatory activity of bacterial DNA. CpG ODN directly stimulate human B cells and plasmacytoid dendritic cells, promote the production of Th1 and proinflammatory cytokines, and trigger the maturation/activation of professional APC. CpG ODN are finding use in the treatment of cancer, allergy, and infection. In contrast, ODN containing multiple TTAGGG motifs mimic the immunosuppressive activity of self-DNA, down-regulating the production of proinflammatory and Th1 cytokines. Preclinical studies suggest that "suppressive" ODN may slow or prevent diseases characterized by pathologic immune stimulation, including autoimmunity and septic shock. Extensive studies in animal models suggest that the therapeutic value of CpG and TTAGGG ODN may be optimized by early administration.

Anti-tumor activity of an anti-endoglin monoclonal antibody is enhanced in immunocompetent mice

In the present study, we investigated the mechanisms by which anti-endoglin (EDG; CD105) monoclonal antibodies (mAbs) suppress angiogenesis and tumor growth. Antihuman EDG mAb SN6j specifically bound to murine endothelial cells and was internalized into the cells in vitro. SN6j effectively suppressed angiogenesis in mice in the Matrigel plug assay. We found that SN6j is more effective for tumor suppression in immunocompetent mice than in SCID mice. We hypothesized that T cell immunity is important for effective antitumor efficacy of SN6j in vivo. To test this hypothesis, we investigated effects of CpG oligodeoxynucleotides (ODN) and depletion of CD4(+) T cells and/or CD8(+) T cells on antitumor efficacy of SN6j in mice. Systemic (i.v.) administration of a relatively small dose (0.6 mug/g body weight/dose) of SN6j suppressed growth of established s.c. tumors of colon-26 in BALB/c mice and improved survival of the tumor-bearing mice. Addition of CpG ODN to SN6j synergistically enhanced antitumor efficacy of SN6j. In contrast, such enhancing effects of CpG ODN were not detected in SCID mice. Antitumor efficacy of SN6j in BALB/c mice was abrogated when CD4(+) T cells and/or CD8(+) T cells were depleted; effect of CD8(+) T cell depletion was stronger. Interestingly, CD4-depletion decreased tumor growth while CD8-depletion enhanced tumor growth in the absence of SN6j. SN6j induced apoptosis in human umbilical vein endothelial cells in a dose-dependent manner which indicates an additional mechanism of antiangiogenesis by SN6j. (c) 2008 Wiley-Liss, Inc.

Synergistic antitumor effects of CpG oligodeoxynucleotide and STAT3 inhibitory agent JSI-124 in a mouse melanoma tumor model

One of the major limitations for cancer immunotherapy is related to the frequent existence of an intra-tumoral immunosuppressive environment, to which STAT3 (Signal transducer and activator of transcription-3) activation in tumor and dendritic cells (DCs) are believed to contribute. In this study, we tested the hypothesis that the combination of CpG (a DC activator) and JSI-124 (a STAT3 inhibitor) may generate synergistic antitumor effects compared to CpG or JSI-124 alone. B16-F10, a mouse melanoma cell line that has constitutively active STAT3, was grafted in C57BL/6 mice and then tumor-bearing mice treated intra-tumorally with (a) phosphate buffered saline, (b) 10 microg CpG, (c) 1 mg kg(-1) JSI-124 or (d) 10 microg CpG+1 mg kg(-1) JSI-124. The effects of treatments on tumor growth, survival and antitumor immune responses were evaluated. Although significant antitumor effects were detected with the single-agent treatments, the CpG+JSI-124 treatment resulted in synergistic antitumor effects compared to CpG or JSI-124 alone. Correlating with these findings, the combination therapy resulted in significantly higher intra-tumoral levels of several proinflammatory, TH1-related cytokines (including IL-12, IFN-gamma, TNF-alpha and IL-2), increases in intra-tumoral CD8+ and CD4+ T cells expressing activation/memory markers and NK cells and increases in activated DCs in the tumors and regional lymph nodes (LNs). Concomitantly, the combination therapy led to a significantly decreased level of immunosuppression, as evidenced by lower intra-tumoral level of VEGF and TGF-beta, and decreased number of CD4+CD25+Foxp3+ regulatory T cells in the regional LNs. This study has provided the proof-of-principle for combining CpG and JSI-124 to enhance antitumor immune responses.

Enhancement of immunity and resistance in mice by pig IL-6 gene and CpG motifs encapsulated in chitosan nanoparticle

This study was conducted to explore the synergetic effect of a novel plasmid containing a porcine IL-6 gene and CpG motifs on immunity of mice in order to develop an effective adjuvant to boost resistance against infection. The synthetic oligodeoxynucleotide containing 11 CpG motifs was inserted into the reconstructed VR1020 plasmid containing the pig IL-6 gene (VRPIL6), designated VRIL6C, and then encapsulated in chitosan nanoparticles (CNP) prepared by ionic cross linkage, designated VRIL6C-CNP. The 3-week old mice were injected, respectively, with VRIL6C-CNP, VRIL6-CNP, CpG-CNP and VR1020-CNP to detect the changes of immunity. At 28 days post inoculation, the mice were challenged with virulent hemolytic serotype 2 Streptococcus to test their resistance against infection. The results showed that there was a significant increase in immunoglobulins and interleukins in mice receiving VRIL6C-CNP compared with the control groups, as well as an increase in the lymphocytes and monocytes in the inoculated mice, so that the immunity was remarkably improved in the VRIL6C-CNP group. The challenge provoked stronger immunity and protection against infection in the VRIL6C-CNP group than in the control mice that manifested severe symptoms and lesions. This suggests that VRIL6C-CNP could remarkably enhance the nonspecific immunity of mice, and facilitate the development of an effective immunopotentiator to promote the resistance of the animals against infection.

Promotion of immunity of mice to Pasteurella multocida and hog cholera vaccine by pig interleukin-6 gene and CpG motifs

A novel oligodeoxynuleotides containing 11 CpG motifs was synthesized and inserted into the VR1020 plasmid containing pig interleukin-6 (IL-6) gene (VPIL6) to construct recombinant plasmid, VPIL6C. The chitosan nanoparticles (CNP) were prepared by ionic cross linkage to entrap the VPIL6C (VPIL6C-CNP), VPIL6 (VPIL6-CNP) and CpG (CpG-CNP). 42-Day old female mice were divided into four groups and intramuscularly injected respectively with 6 pmol VPIL6C-CNP, VPIL6-CNP, CpG-CNP and VR1020-CNP along with the bivalent vaccines against the Pasteurellosis and hog cholera. The blood was weekly collected from mice after vaccination to detect the changes of immunoglobulins, specific antibodies, IL-2, IL-4, IL-6 and immune cells. 28 days after vaccination, the mice were orally challenged with virulent Pasteurella multocida. The results showed that in comparison with those of the control VR1020 group, the content of immunoglobulins, specific antibodies and interleukins significantly increased in the sera from the treated two groups (P<0.05). Meanwhile, the number of lymphocytes and monocytes also remarkably elevated in the treated groups (P<0.05). The immune responses of VPIL6C mice were notably stronger than those of VPIL6 and CpG group. The challenge results proved that the overall immunity was further promoted in the treated mice which resisted the challenge infection; while the control mice manifested evident symptoms and lesions, and died of infection. These suggested that VPIL6C-CNP could better promote the immunity and resistance of mice against Pasteurellosis than VPIL6-CNP and CpG-CNP, and facilitate the development of effective adjuvant to enhance the immunity of animal against infection.