Sindbis Virus Vaccine Platform: A Promising Oncolytic Virus-Mediated Approach for Ovarian Cancer Treatment

This review article provides a comprehensive overview of a novel Sindbis virus vaccine platform as potential immunotherapy for ovarian cancer patients. Ovarian cancer is the most lethal of all gynecological malignancies. The majority of high-grade serous ovarian cancer (HGSOC) patients are diagnosed with advanced disease. Current treatment options are very aggressive and limited, resulting in tumor recurrences and 50-60% patient mortality within 5 years. The unique properties of armed oncolytic Sindbis virus vectors (SV) in vivo have garnered significant interest in recent years to potently target and treat ovarian cancer. We discuss the molecular biology of Sindbis virus, its mechanisms of action against ovarian cancer cells, preclinical in vivo studies, and future perspectives. The potential of Sindbis virus-based therapies for ovarian cancer treatment holds great promise and warrants further investigation. Investigations using other oncolytic viruses in preclinical studies and clinical trials are also presented.

Channeling the Natural Properties of Sindbis Alphavirus for Targeted Tumor Therapy

Sindbis alphavirus vectors offer a promising platform for cancer therapy, serving as valuable models for alphavirus-based treatment. This review emphasizes key studies that support the targeted delivery of Sindbis vectors to tumor cells, highlighting their effectiveness in expressing tumor-associated antigens and immunomodulating proteins. Among the various alphavirus vectors developed for cancer therapy, Sindbis-vector-based imaging studies have been particularly extensive. Imaging modalities that enable the in vivo localization of Sindbis vectors within lymph nodes and tumors are discussed. The correlation between laminin receptor expression, tumorigenesis, and Sindbis virus infection is examined. Additionally, we present alternative entry receptors for Sindbis and related alphaviruses, such as Semliki Forest virus and Venezuelan equine encephalitis virus. The review also discusses cancer treatments that are based on the alphavirus vector expression of anti-tumor agents, including tumor-associated antigens, cytokines, checkpoint inhibitors, and costimulatory immune molecules.

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

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

Vaccination with synthetic long peptide formulated with CpG in an oil-in-water emulsion induces robust E7-specific CD8 T cell responses and TC-1 tumor eradication

BACKGROUND

Despite considerable efforts at developing therapeutic vaccines for cancer, clinical translation of preclinical successes has been challenging, largely due to the difficulty of inducing strong and sustained cytotoxic T lymphocyte (CTL) responses in patients. Several peptide-based cancer vaccines have failed to show sustainable tumor regression in the clinic, possibly because of a lack of optimization of both the adjuvant and antigen components of the preparations. Here, we aimed to develop and optimize a vaccine format utilizing a synthetic long peptide (SLP) containing the human papilloma virus 16 (HPV16) E7 antigen, with a centrally located defined MHC class I epitope, and evaluate its immunogenicity and efficacy in combination with various adjuvant formulations.

METHODS

E7_31-73 SLP was tested alone or in combination with toll-like receptor (TLR)3, TLR4, TLR7/8 and TLR9 agonists and formulated in oil-in-water (o/w) or water-in-oil (w/o) emulsions to determine a vaccine format inducing a robust CD8 T cell response in murine models. Once a lead vaccine format was determined, we examined its ability to inhibit tumor growth in the murine TC-1 model that expresses HPV16 E7 antigen.

RESULTS

We identified the TLR9 agonist CpG formulated in a squalene-based o/w emulsion as the most potent adjuvant, inducing the expansion of multifunctional antigen specific CD8 T cells with cytolytic potential. We also demonstrated that SLP E7_31-73 + CpG + o/w emulsion vaccine can provide prophylactic and more importantly, therapeutic benefit in the TC-1 murine tumor model.

CONCLUSIONS

Our results demonstrate that the novel vaccine format E7 SLP + CpG delivered in an o/w emulsion holds potential for the promotion of strong CTL responses and tumor eradication and encourages further development of peptide/adjuvant vaccines in cancer immunotherapy strategies.

Toll-Like Receptor-3 Mediates HIV-1-Induced Interleukin-6 Expression in the Human Brain Endothelium via TAK1 and JNK Pathways: Implications for Viral Neuropathogenesis

HIV-1-associated neurocognitive disorders (HAND) is associated with blood-brain-barrier (BBB) inflammation, and inflammation involves toll-like receptors (TLRs) signaling. It is not known whether primary human brain microvascular endothelial cells (HBMEC), the major BBB component, express TLRs or whether TLRs are involved in BBB dysfunction and HAND. We demonstrate that HBMEC express TLR3, 4, 5, 7, 9, and 10, and TLR3 was the most abundant. HIV-1 and TLR3 activation increased endothelial TLR3 transcription and expression. HIV-1-positive human subjects showed significantly higher TLR3 expression in brain tissues and blood vessels, with higher TLR3 levels in subjects with HAND. HIV-1 and TLR3 activation increased endothelial IL6 expression by 6-to-127-fold (P < 0.001), activated c-jun(serine-63) and SAPK/JNK(Thr183/Tyr185). HIV-1 upregulated IL6 through interleukin-1 receptor-associated-kinase (IRAK)-1/4/TAK1/JNK pathways, via ATP-dependent JNK activation. TLR3 activation upregulated IL6 through TAK1/JNK pathways, via ATP-dependent or -independent JNK activation. HIV-1 and TLR3 activation also upregulated transcription factors associated with IL6 and TAK1/JNK pathways (Jun, CEBPA, STAT1). Blocking TLR3 activation prevented HIV-1- and TLR3 ligands-induced upregulation of these transcription factors, prevented IL6 transcription and expression, c-jun and JNK activation. HIV-1 and TLR3 ligands significantly increased monocytes adhesion and migration through the BBB, and decreased endothelial claudin-5 expression. Blocking TLR3 and JNK activation prevented HIV-1- and TLR3 ligands-induced claudin-5 downregulation, monocytes adhesion and transendothelial migration. These data suggest that viral immune recognition via endothelial TLR3 is involved in endothelial inflammation and BBB dysfunction in HIV/AIDS and HAND. Our data provides novel insights into the molecular basis of these HIV-1- and TLR3-mediated effects.

PolyICLC Exerts Pro- and Anti-HIV Effects on the DC-T Cell Milieu In Vitro and In Vivo

Myeloid dendritic cells (mDCs) contribute to both HIV pathogenesis and elicitation of antiviral immunity. Understanding how mDC responses to stimuli shape HIV infection outcomes will inform HIV prevention and treatment strategies. The long double-stranded RNA (dsRNA) viral mimic, polyinosinic polycytidylic acid (polyIC, PIC) potently stimulates DCs to focus Th1 responses, triggers direct antiviral activity in vitro, and boosts anti-HIV responses in vivo. Stabilized polyICLC (PICLC) is being developed for vaccine adjuvant applications in humans, making it critical to understand how mDC sensing of PICLC influences HIV infection. Using the monocyte-derived DC (moDC) model, we sought to describe how PICLC (vs. other dsRNAs) impacts HIV infection within DCs and DC-T cell mixtures. We extended this work to in vivo macaque rectal transmission studies by administering PICLC with or before rectal SIVmac239 (SIVwt) or SIVmac239ΔNef (SIVΔNef) challenge. Like PIC, PICLC activated DCs and T cells, increased expression of α4β7 and CD169, and induced type I IFN responses in vitro. The type of dsRNA and timing of dsRNA exposure differentially impacted in vitro DC-driven HIV infection. Rectal PICLC treatment similarly induced DC and T cell activation and pro- and anti-HIV factors locally and systemically. Importantly, this did not enhance SIV transmission in vivo. Instead, SIV acquisition was marginally reduced after a single high dose challenge. Interestingly, in the PICLC-treated, SIVΔNef-infected animals, SIVΔNef viremia was higher, in line with the importance of DC and T cell activation in SIVΔNef replication. In the right combination anti-HIV strategy, PICLC has the potential to limit HIV infection and boost HIV immunity.

Powerful Complex Immunoadjuvant Based on Synergistic Effect of Combined TLR4 and NOD2 Activation Significantly Enhances Magnitude of Humoral and Cellular Adaptive Immune Responses

Binding of pattern recognition receptors (PRRs) by pathogen-associated molecular patterns (PAMPs) activates innate immune responses and contributes to development of adaptive immunity. Simultaneous stimulation of different types of PRRs can have synergistic immunostimulatory effects resulting in enhanced production of molecules that mediate innate immunity such as inflammatory cytokines, antimicrobial peptides, etc. Here, we evaluated the impact of combined stimulation of PRRs from different families on adaptive immunity by generating alum-based vaccine formulations with ovalbumin as a model antigen and the Toll-like receptor 4 (TLR4) agonist MPLA and the Nucleotide-binding oligomerization domain-containing protein 2 (NOD2) agonist MDP adsorbed individually or together on the alum-ovalbumin particles. Multiple in vitro and in vivo readouts of immune system activation all showed that while individual PRR agonists increased the immunogenicity of vaccines compared to alum alone, the combination of both PRR agonists was significantly more effective. Combined stimulation of TLR4 and NOD2 results in a stronger and broader transcriptional response in THP-1 cells compared to individual PRR stimulation. Immunostimulatory composition containing both PRR agonists (MPLA and MDP) in the context of the alum-based ovalbumin vaccine also enhanced uptake of vaccine particles by bone marrow derived dendritic cells (BMDCs) and promoted maturation (up-regulation of expression of CD80, CD86, MHCII) and activation (production of cytokines) of BMDCs. Finally, immunization of mice with vaccine particles containing both PRR agonists resulted in enhanced cellular immunity as indicated by increased proliferation and activation (IFN-γ production) of splenic CD4+ and CD8+ T cells following in vitro restimulation with ovalbumin and enhanced humoral immunity as indicated by higher titers of ovalbumin-specific IgG antibodies. These results indicate that combined stimulation of TLR4 and NOD2 receptors dramatically enhances activation of both the humoral and cellular branches of adaptive immunity and suggests that inclusion of agonists of these receptors in standard alum-based adjuvants could be used to improve the effectiveness of vaccination.

Toll-like receptor-3 mediates HIV-1 transactivation via NFκB and JNK pathways and histone acetylation, but prolonged activation suppresses Tat and HIV-1 replication

TLR3 has been implicated in the pathogenesis of several viral infections, including SIV- and HIV-1-induced inflammation and AIDS. However the molecular mechanisms of these TLR3-mediated effects are not known, and it is not known whether HIV interacts with cellular TLR3 to affect disease process. Here we investigate the effects of TLR3 ligands on HIV-1 transactivation using both primary human macrophages and cells containing integrated copies of the HIV-1 promoter. We demonstrate that TLR3 activation induced upregulation of transcription factors such as c-Jun, CCAAT/enhancer-binding protein alpha (CEBPA), signal transducer and activator of transcription (STAT)-1, STAT-2, RELB, and nuclear factor kappa-B1 (NFκB1), most of which are known to regulate the HIV promoter activity. We also demonstrate that TLR3 activation increased HIV-1 transactivation via the c-Jun N-terminal kinase (JNK) and NFκB pathways. This was associated with epigenetic modifications, including decreased histone deacetylase activity, increased histone acetyl transferase (HAT) activity, and increased acetylation of histones H3 and H4 at lysine residues in the nucleosome-0 and nucleosome-1 of the HIV-1 promoter. However, prolonged TLR3 activation decreased HIV-1 transactivation, decreased HAT activity and Tat transcription, and suppressed viral replication. Overall, data suggests that TLR3 can act as viral sensor to mediate viral transactivation, cellular signaling, innate immune response, and inflammation in HIV-infected humans. Our study provides novel insights into the molecular basis for these TLR3-mediated effects.

Epicutaneous immune modulation with Bet v 1 plus R848 suppresses allergic asthma in a murine model

BACKGROUND

Combining allergen(s) with an adjuvant is a strategy to improve the efficacy and safety of allergen-specific immunotherapy. Here, we aimed at investigating the adjuvant effects of polyadenylic-polyuridylic acid (poly(A:U)), a TLR3 agonist, and R848 (resiquimod), a TLR7 agonist, in epicutaneous immunotherapy with Bet v 1, the major birch pollen allergen, to intervene in birch pollen allergy.

METHODS AND RESULTS

BALB/c mice received epicutaneous immunization (EPI) with recombinant Bet v 1 (rBet v 1) alone, or plus poly(A:U), or R848 on their depilated back using patches. Among the groups, EPI with rBet v 1 and R848 induced detectable levels of IFN-γ-producing CD4(+) T cells in lymph nodes and Bet v 1-specific IgG2a antibodies in the sera of mice. Before or after EPI, mice were sensitized with rBet v 1 plus aluminium hydroxide adjuvant and intranasally challenged with birch pollen extract. Prophylactic EPI with rBet v 1 plus R848 inhibited the production of biologically active Bet v 1-specific IgE antibodies in sensitization. Prophylactic and therapeutic EPI with rBet v 1 plus R848 suppressed lung inflammation upon challenges. Remarkably, only rBet v 1 plus R848 reduced the development of enhanced pause (PenH), a substituted parameter for airway hyper-reactivity, in challenged mice. In contrast to R848, poly(A:U) did not present adjuvant effect on the suppression of asthmatic features.

CONCLUSION

Epicutaneous immunization with rBet v 1 plus R848 induced predominant Bet v 1-specific Th1 responses and efficiently suppressed asthmatic features elicited by birch pollen. R848 could be a promising adjuvant in epicutaneous immunotherapy for birch pollen-induced allergic asthma.

Nuclear factor κB2 p52 protein has a role in antiviral immunity through IκB kinase epsilon-dependent induction of Sp1 protein and interleukin 15

In this study we describe a previously unreported function for NFκB2, an NFκB family transcription factor, in antiviral immunity. NFκB2 is induced in response to poly(I:C), a mimic of viral dsRNA. Poly(I:C), acting via TLR3, induces p52-dependent transactivation of a reporter gene in a manner that requires the kinase activity of IκB kinase ε (IKKε) and the transactivating potential of RelA/p65. We identify a novel NFκB2 binding site in the promoter of the transcription factor Sp1 that is required for Sp1 gene transcription activated by poly(I:C). We show that Sp1 is required for IL-15 induction by both poly(I:C) and respiratory syncytial virus, a response that also requires NFκB2 and IKKε. Our study identifies NFκB2 as a target for IKKε in antiviral immunity and describes, for the first time, a role for NFκB2 in the regulation of gene expression in response to viral infection.

Direct effect of dsRNA mimetics on cancer cells induces endogenous IFN-β production capable of improving dendritic cell function

Viral double-stranded RNA (dsRNA) mimetics have been explored in cancer immunotherapy to promote antitumoral immune response. Polyinosine-polycytidylic acid (poly I:C) and polyadenylic-polyuridylic acid (poly A:U) are synthetic analogs of viral dsRNA and strong inducers of type I interferon (IFN). We describe here a novel effect of dsRNA analogs on cancer cells: besides their potential to induce cancer cell apoptosis through an IFN-β autocrine loop, dsRNA-elicited IFN-β production improves dendritic cell (DC) functionality. Human A549 lung and DU145 prostate carcinoma cells significantly responded to poly I:C stimulation, producing IFN-β at levels that were capable of activating STAT1 and enhancing CXCL10, CD40, and CD86 expression on human monocyte-derived DCs. IFN-β produced by poly I:C-activated human cancer cells increased the capacity of monocyte-derived DCs to stimulate IFN-γ production in an allogeneic stimulatory culture in vitro. When melanoma murine B16 cells were stimulated in vitro with poly A:U and then inoculated into TLR3(-/-) mice, smaller tumors were elicited. This tumor growth inhibition was abrogated in IFNAR1(-/-) mice. Thus, dsRNA compounds are effective adjuvants not only because they activate DCs and promote strong adaptive immunity, but also because they can directly act on cancer cells to induce endogenous IFN-β production and contribute to the antitumoral response.

Therapeutic applications of nucleic acids and their analogues in Toll-like receptor signaling

Toll-like receptors (TLRs) belong to a family of innate immune receptors that detect and clear invading microbial pathogens. Specifically intracellular TLRs such as TLR3, TLR7, TLR8 and TLR9 recognize nucleic acids such as double-stranded RNA, single-stranded RNA and CpG DNA respectively derived from microbial components. Upon infection, nucleic acid sensing TLRs signal within endosomal compartment triggering the induction of essential proinflammatory cytokines and type I interferons to initiate innate immune responses thereby leading to a critical role in the development of adaptive immune responses. Thus, stimulation of TLRs by nucleic acids is a promising area of research for the development of novel therapeutic strategies against pathogenic infection, allergies, malignant neoplasms and autoimmunity. This review summarizes the therapeutic applications of nucleic acids or nucleic acid analogues through the modulation of TLR signaling pathways.

Programmed cell death-1 (PD-1) at the heart of heterologous prime-boost vaccines and regulation of CD8+ T cell immunity

Developing new vaccination strategies and optimizing current vaccines through heterologous prime-boost carries the promise of integrating the benefits of different yet synergistic vectors. It has been widely thought that the increased immunity afforded by heterologous prime-boost vaccination is mainly due to the minimization of immune responses to the carrier vectors, which allows a progressive build up of immunity against defined epitopes and the subsequent induction of broader immune responses against pathogens. Focusing on CD8⁺ T cells, we put forward a different yet complementary hypothesis based primarily on the systematic analysis of DNA vaccines as priming agents. This hypothesis relies on the finding that during the initiation of immune response, acquisition of co-inhibitory receptors such as programmed cell death-1 (PD-1) is determined by the pattern of antigen exposure in conjunction with Toll-like receptor (TLR)-dependent stimulation, critically affecting the magnitude and profile of secondary immunity. This hypothesis, based upon the acquisition and co-regulation of pivotal inhibitory receptors by CD8⁺ T cells, offers a rationale for gene-based immunization as an effective priming strategy and, in addition, outlines a new dimension to immune homeostasis during immune reaction to pathogens. Finally, this model implies that new and optimized immunization approaches for cancer and certain viral infections must induce highly efficacious T cells, refractory to a broad range of immune-inhibiting mechanisms, rather than solely or primarily focusing on the generation of large pools of vaccine-specific lymphocytes.

Circulating nucleic acids in type 1 diabetes may modulate the thymocyte turnover rate

The autoimmunity of type 1 diabetes is associated with T-cell hyperactivity. Current study was designed to examine the effect of circulating ribonucleic acids (RNAs), isolated from type 1 diabetic patients on proliferative, apoptotic and inflammatory potential of rat thymocytes. Rat thymocytes were assayed for proliferating nuclear cell antigen (PCNA), Bcl-2, Bax and NF-κB level, using the flow cytometric and fluorometric assays. Cells were allocated into groups, treated with RNAs purified from plasma of juvenile diabetics, adult type 1 diabetic patients, control healthy children, healthy adult persons, nucleic acids and polynucleotide standards (RNA, polyC, PolyA, PolyIC, and CpG). The upregulation of PCNA and Bcl-2 protein and downregulation of Bax protein and NF-κB was shown when the thymocytes where incubated with RNA purified from plasma of juvenile type 1 diabetic patients. The dysregulation of inflammatory cascade and central tolerance may be a defect in autoimmune diseases related to innate immunity leading to corresponding alteration in adaptive immune response.

Opposing effects of toll-like receptor (TLR3) signaling in tumors can be therapeutically uncoupled to optimize the anticancer efficacy of TLR3 ligands

Many cancer cells express Toll-like receptors (TLR) that offer possible therapeutic targets. Polyadenylic-polyuridylic acid [poly(A:U)] is an agonist of the Toll-like receptor TLR3 that displays anticancer properties. In this study, we illustrate how the immunostimulatory and immunosuppressive effects of this agent can be uncoupled to therapeutic advantage. We took advantage of two TLR3-expressing tumor models that produced large amounts of CCL5 (a CCR5 ligand) and CXCL10 (a CXCR3 ligand) in response to type I IFN and poly(A:U), both in vitro and in vivo. Conventional chemotherapy or in vivo injection of poly(A:U), alone or in combination, failed to reduce tumor growth unless an immunochemotherapeutic regimen of vaccination against tumor antigens was included. CCL5 blockade improved the efficacy of immunochemotherapy, whereas CXCR3 blockade abolished its beneficial effects. These findings show how poly(A:U) can elicit production of a range of chemokines by tumor cells that reinforce immunostimulatory or immunosuppressive effects. Optimizing the anticancer effects of TLR3 agonists may require manipulating these chemokines or their receptors.

Lymph node-targeted immunotherapy mediates potent immunity resulting in regression of isolated or metastatic human papillomavirus-transformed tumors

PURPOSE

The goal of this study was to investigate the therapeutic potential of a novel immunotherapy strategy resulting in immunity to localized or metastatic human papillomavirus 16-transformed murine tumors.

EXPERIMENTAL DESIGN

Animals bearing E7-expressing tumors were coimmunized by lymph node injection with E7 49-57 antigen and TLR3-ligand (synthetic dsRNA). Immune responses were measured by flow cytometry and antitumor efficacy was evaluated by tumor size and survival. In situ cytotoxicity assays and identification of tumor-infiltrating lymphocytes and T regulatory cells were used to assess the mechanisms of treatment resistance in bulky disease. Chemotherapy with cyclophosphamide was explored to augment immunotherapy in late-stage disease.

RESULTS

In therapeutic and prophylactic settings, immunization resulted in a considerable expansion of E7 49-57 antigen-specific T lymphocytes in the range of 1/10 CD8(+) T cells. The resulting immunity was effective in suppressing disease progression and mortality in a pulmonary metastatic disease model. Therapeutic immunization resulted in control of isolated tumors up to a certain volume, and correlated with antitumor immune responses measured in blood. In situ analysis showed that within bulky tumors, T-cell function was affected by negative regulatory mechanisms linked to an increase in T regulatory cells and could be overcome by cyclophosphamide treatment in conjunction with immunization.

CONCLUSIONS

This study highlights a novel cancer immunotherapy platform with potential for translatability to the clinic and suggests its potential usefulness for controlling metastatic disease, solid tumors of limited size, or larger tumors when combined with cytotoxic agents that reduce the number of tumor-infiltrating T regulatory cells.

siRNAs: their potential as therapeutic agents--Part I. Designing of siRNAs

RNA interference (RNAi) is a novel and essential biological process, as well as a powerful experimental tool with the potential to be used in therapeutic development. RNAi-based strategies have the capability of being able to be driven from bench to bedside. It is very important to develop the precise tools for designing the siRNAs to get the most efficient knockdown of the target genes and to reduce any off-target effects. In this review we have discussed the strategies and parameters required for effective siRNA designing and synthesis, based on already published literature.

Adjuvants targeting innate and adaptive immunity synergize to enhance tumor immunotherapy

Because of mechanisms of self-tolerance, many tumor-specific CD8 T cells exhibit low avidity for tumor antigens and would benefit from strategies that enhance their numbers and effector function. Here we demonstrate that the combined use of two different types of immune adjuvants, one that directly targets the CD8 cell, IL-2/anti-IL-2 mAb complexes, and one that targets the innate immune system, poly(I:C), can achieve this goal. Provision of IL-2/mAb complexes was found to enhance the activation and effector function of low-avidity tumor-specific T cells, yet this was insufficient to achieve tumor eradication. The addition of poly(I:C) further increased the accumulation of granzyme B-expressing effectors within the tumor and resulted in tumor eradication. This strategy presents many of the benefits of whole-body irradiation, including the provision of high levels of homeostatic cytokines, enhanced expansion of effector cells relative to regulatory T cells, and provision of inflammatory cytokines, and is therefore likely to serve as a strategy for both tumor vaccines and adoptive immunotherapy of cancer.

Altered degradation of circulating nucleic acids and oligonucleotides in diabetic patients

Foreign, infection-associated or endogenously generated circulating nucleotide motifs may represent the critical determinants for the activation of the Toll-like receptors (TLRs), leading to immune stimulation and cytokine secretion. The importance of circulating nucleases is to destroy nucleic acids and oligonucleotides in the blood stream and during cell entry. Patients with juvenile insulin-dependent diabetes, adult patients with insulin-dependent diabetes and adult patients with type 2 diabetes were allocated to the study, together with the age-matched control subjects. Plasma RNase and nuclease activity were examined, in relation to different substrates-TLRs response modifiers, and circulating RNA and oligonucleotides were isolated. The fall in enzyme activity in plasma was obtained for rRNA, poly(C), poly(U), poly(I:C), poly(A:U) and CpG, especially in juvenile diabetics. In order to test the non-enzymatic glycation, commercial RNase (E.C.3.1.27.5) and control plasma samples were incubated with increasing glucose concentrations (5, 10, 20 and 50 mmol/l). The fall of enzyme activity was expressed more significantly in control plasma samples than for the commercial enzyme. Total amount of purified plasma RNA and oligonucleotides was significantly higher in diabetic patients, especially in juvenile diabetics. The increase in the concentration of nucleotides corresponded to the peak absorbance at 270 nm, similar to polyC. The electrophoretic bands shared similar characteristics between controls and each type of diabetic patients, except that the bands were more expressed in diabetic patients. Decreased RNase activity and related increase of circulating oligonucleotides may favor the increase of nucleic acid "danger motifs", leading to TLRs activation.

Tumor-targeted delivery of siRNA by self-assembled nanoparticles

We have developed a self-assembled nanoparticle (NP) that efficiently delivers small interfering RNA (siRNA) to the tumor by intravenous (IV) administration. The NP was obtained by mixing carrier DNA, siRNA, protamine, and lipids, followed by post-modification with polyethylene glycol and a ligand, anisamide. Four hours after IV injection of the formulation into a xenograft model, 70-80% of injected siRNA/g accumulated in the tumor, approximately 10% was detected in the liver and approximately 20% recovered in the lung. Confocal microscopy showed that fluorescent-labeled siRNA was efficiently delivered into the cytoplasm of the sigma receptor expressing NCI-H460 xenograft tumor by the targeted NPs, whereas free siRNA and non-targeted NPs showed little uptake. Three daily injections (1.2 mg/kg) of siRNA formulated in the targeted NPs silenced the epidermal growth factor receptor (EGFR) in the tumor and induced approximately 15% tumor cell apoptosis. Forty percent tumor growth inhibition was achieved by treatment with targeted NPs, while complete inhibition lasted for 1 week when combined with cisplatin. The serum level of liver enzymes and body weight monitoring during the treatment indicated a low level of toxicity of the formulation. The carrier itself also showed little immunotoxicity (IMT).

Protection of pigs from lethal challenge by a DNA vaccine based on an alphavirus replicon expressing the E2 glycoprotein of classical swine fever virus

In a previous study, it has been shown that a Semliki Forest virus (SFV) replicon vectored DNA vaccine (pSFV1CS-E2) expressing the E2 glycoprotein of classical swine fever virus (CSFV) conferred full protection for pigs immunized three times with 600 microg of the vaccine. This study was designed to evaluate further the efficacy of the vaccine with lower dosage and fewer inoculations. Pigs were immunized twice with 100 microg of pSFV1CS-E2 (n=5) or control plasmid pSFV1CS (n=3), respectively, and challenged with virulent Shimen strain 6 weeks following the booster immunization. Pigs immunized with pSFV1CS-E2 developed high titers of specific neutralizing antibodies against CSFV after the booster, and the antibody titers increased rapidly upon challenge. The immunized animals showed no clinical symptoms except short-term fever and low-level viremia, whereas, the control pigs immunized with the control plasmid produced no detectable antibody prior to challenge, and showed obvious clinical signs following challenge, and two pigs died of illness. All control animals developed extended viremia as detected by nested RT-PCR and real-time RT-PCR. Severe pathologic lesions typical of CSFV infection were observed at necropsy. It is concluded that the alphavirus replicon-vectored DNA-based vaccine can be a potential marker vaccine against CSFV.

Immunobiology of toll-like receptors in allergic disease

Allergic diseases prevalence rates have increased dramatically over the last 50 years in developed countries and one explanation might be that modern practices in public health lead to a decreased exposure towards pathogens resulting in a misguided immune response. Recently, it has become evident that immune responses against pathogens are initiated by Toll-like receptors (TLRs) that recognize a variety of structures derived from viruses, bacteria, fungi or protozoa. In this review we will discuss TLR ligands, TLR signaling in regard to Th1 and Th2 immune responses, their involvement in the development and their therapeutic potential in treatment of allergic disease.

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

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

The adjuvant effects of the toll-like receptor 3 ligand polyinosinic-cytidylic acid poly (I:C) on antigen-specific CD8+ T cell responses are partially dependent on NK cells with the induction of a beneficial cytokine milieu

Poly (I:C), a TLR3 ligand, has shown promise as a vaccine adjuvant to CD8(+) T cell responses. The underlying mechanisms involved in creating this adjuvant response in vivo, however, have not been well defined. In this study, we explored the contribution of NK cells and inflammatory cytokines in mediation the poly (I:C) adjuvant effects. Enhanced antigen-specific CD8(+) T cell responses were observed only when poly (I:C) was administered within 4h of peptide vaccination. Poly (I:C) treatment was associated with a rapid induction of inflammatory cytokines in the serum, including IL-6, IL-10, MCP-1, TNF-alpha, IFN-alpha, and IFN-gamma, and selective increases in the numbers of NK (NK1.1(+)CD11b(+)) cells and Mvarphi (NK1.1(-)CD11b(+)), but not NK T (CD3(+)NK1.1(+)) cells. NK cells were required for the adjuvant effects of poly (I:C). Poly (I:C) treatment in TNF-alpha, type I IFNR, IFN-gamma, IL-6, IL-12Rbeta2, or IL-15 gene-deficient mice revealed a reciprocal interaction and interdependence in the induction of these cytokines, where the absence of one cytokine impacted on the production of others. Further, the adjuvant effects of poly (I:C) were dependent on the endogenous levels of type I IFNs, TNF-alpha, IFN-gamma, IL-12, and IL-15. IFN-alpha and IFN-beta, but not TNF-alpha or IL-6, were able to mimic the adjuvant effects of poly (I:C). We conclude that the adjuvant effects of poly (I:C) on antigen-specific CD8(+) T cells appeared to be exquisitely dependent on the rapid induction of certain beneficial cytokines produced in part by NK cells.

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

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

Stable expression of shRNAs in human CD34+ progenitor cells can avoid induction of interferon responses to siRNAs in vitro

RNA interference occurs when cytoplasmic small interfering RNAs (siRNAs) enter the RNA-induced silencing complex and one strand guides cleavage of the target RNA by the Argonaute 2 protein. A significant concern when applying siRNAs or expressing small hairpin RNAs (shRNAs) in human cells is activation of the interferon (IFN) response. Synthetic siRNAs harboring certain motifs can induce an immune response when delivered to mouse and human immune cells such as peripheral blood mononuclear cells, monocytes, plasmacytoid dendritic cells (pDCs) and nonplasmacytoid dendritic cells (mDCs). In the present study we have tested the immunostimulatory effects of lipid-delivered siRNAs versus Pol III promoter-expressed shRNAs in primary CD34+ progenitor-derived hematopoietic cells. We show that in this system, lipid-delivered siRNAs are potent inducers of IFNalpha and type I IFN gene expression, whereas the same sequences when expressed endogenously are nonimmunostimulatory.

Recombinant alphaviruses as vectors for anti-tumour and anti-microbial immunotherapy

BACKGROUND

Vectors derived from alphaviruses are gaining interest for their high transfection potency and strong immunogenicity.

OBJECTIVES

After a brief introduction on alphaviruses and their vectors, an overview is given on current preclinical immunotherapy studies using vector systems based on alphaviruses. The efficacy of alphavirus vectors in inducing immune responses will be illustrated by a more detailed description of immunization studies using recombinant Semliki Forest virus for the treatment of human papilloma virus-induced cervical cancer.

RESULTS

Immunization with recombinant alphavirus results in the induction of humoral and cellular immune responses against microbes, infected cells and cancer cells. Preclinical studies demonstrate that infectious diseases and cancer can be treated prophylactically as well as therapeutically.

CONCLUSIONS

Alphavirus-based genetic immunization strategies are highly effective in animal model systems, comparing quite favourably with any other approach. Therefore, we hope and expect to see an efficient induction of tumour-or microbial immunity and a positive outcome in future clinical efficacy studies.

Immunological responses after immunisation of mice with microparticles containing antigen and single stranded RNA (polyuridylic acid)

Certain toll-like receptor (TLR) agonists, e.g. CpG DNA, can be used as potent vaccine 'adjuvants'. It is known that some sequences of single stranded (ss) RNA stimulate proinflammatory and antiviral responses following interaction with TLR 7 and 8. We have encapsulated ovalbumin (OVA) in the presence and absence of polyuridylic acid (poly-U) inside polylactide microparticles. In comparison to microparticles containing only OVA, bulk cultures of bone marrow-derived plasmacytoid and myeloid dendritic cells produced more (P<0.05) IL-12 and interferon (IFN)-alpha when stimulated with microparticles containing OVA and poly-U. Subcutaneous injection of comicroencapsulated OVA and poly-U resulted in statistically elevated levels of serum anti-OVA IgG1 (P<0.05 versus naïve mice). Conversely, anti-OVA IgG1 levels in C57 BL6 mice immunised with OVA loaded microparticles (without RNA) were statistically indifferent to naïve animals. Furthermore, injection of coencapsulated OVA and poly-U resulted in (P<0.05) greater numbers of OVA specific IFN-gamma secreting T-cells as compared with mice injected with OVA loaded microparticles. A similar trend was seen in mice immunised with OVA loaded microparticles decorated with CpG or solutions of admixed OVA and CpG (P<0.05). These data demonstrate, for the first time, that appropriately formulated ssRNA can act as a potent adjuvant and modulator of adaptive immunological responses.

Profiles of NK, NKT cell activation and cytokine production following vaccination against hepatitis B

Human natural killer (NK) cells (CD56+ CD3-) represent crucial components of the innate immune system especially against viral infections and because their activation can modulate the outcome of the adaptive immune response. NKT cells (CD56+CD3+), a lymphocyte T population characterized by expression of surface markers of NK cells, are known to be abundant in the liver and their activation could be associated with hepatic injury. Using three-color flow cytometry to measure surface receptors and intracellular cytokines, we have explored early activation signals and cytokine production in NK and NKT cells within a group of hepatitis B vaccinated and non-vaccinated individuals. A specific increase of the CD56bright cell population, the activation receptor CD69 and IFN-gamma, was observed in NK cells following incubation with recombinant HBsAg in responders to vaccination. Comparable results were observed in NKT cells showing an increment of CD69, CD25, IL-2 and IFN-gamma expression in responder subjects. These parameters were statistically diminished in non-responder individuals (p<0.05) in both groups of cells. These results demonstrate a diminished activation of these cells in non-responders to the vaccine, suggesting that NK and NKT cells play an important role in the immune response following hepatitis B vaccination.

Ischemia-reperfusion injury activates innate immunity in rat kidneys

BACKGROUND

There is growing evidence of a role of the immune system in the pathophysiology of ischemia-reperfusion (I/R) injury, but the influence of I/R injury on innate immunity is still undetermined.

METHODS

Sprague-Dawley rats were used. I/R injury was induced by clamping both renal arteries for 45 min, and the rats were killed 1, 3, 5, and 7 days later. Activation of innate immunity was evaluated in terms of the expression of toll-like receptor (TLR) 2 or TLR4 mRNAs and protein, by the level of the TLR ligand (heat shock protein [HSP] 70), and maturation of dendritic cells by double-label immunohistochemistry of dendritic cells for major histocompatibility complex (MHC) class II antigen.

RESULTS

I/R injury increased TLR2 and TLR4 mRNA and protein expression, and they were mainly observed on renal tubular cells. I/R injury also produced endogenous TLR ligand (HSP70) on renal tubular cells. I/R injury increased not only the numbers of dendritic cells but also the production of MHC class II antigen in dendritic cells, suggesting maturation of these cells. Activation of innate immunity was observed at day 1, peaked at days 3 to 5 after I/R injury, and thereafter gradually decreased.

CONCLUSIONS

I/R injury rapidly activates the innate immune response.

The binding affinity of double-stranded RNA motifs to HIV-1 Tat protein affects transactivation and the neutralizing capacity of anti-Tat antibodies elicited after intranasal immunization

In this study we examined the hypothesis that the binding affinity of two double-stranded (ds) RNA motifs to HIV-1 Tat protein might affect transactivation and the type of anti-Tat immune responses. Using surface plasmon resonance technology we demonstrated the capacity of the poly(A):poly(U) (pA:pU) motif to bind with high affinity to a totally synthetic Tat protein and to inhibit more efficiently the Tat/transactivation response element (TAR) RNA interaction as compared to the poly(I):poly(C) (pI:pC) motif. Furthermore, the pA:pU motif was tenfold more effective in inhibiting Tat-driven transactivation than the pI:pC motif. Following intranasal immunization of mice, both dsRNA motifs enhanced the antibody (serum and mucosal) and cellular responses to Tat. However, only the serum samples of mice immunized with Tat + pI:pC inhibited Tat-driven transactivation. The profile of serum antibody subclasses together with the secreted cytokines by Tat-stimulated splenocyte cultures indicated that both dsRNA motifs favored the induction of a balanced Th1 and Th2 immune response. The demonstration in this study that two dsRNA motifs had a marked effect on Tat/TAR RNA interaction and on the neutralizing capacity of anti-Tat specific antibody responses highlights their potential for biological applications and the importance of selecting the appropriate motif as an adjuvant for vaccine design.

Defining the antigen-specific T-cell response to vaccination and poly(I:C)/TLR3 signaling: evidence of enhanced primary and memory CD8 T-cell responses and antitumor immunity

Poly(I:C), a synthetic double-stranded RNA polymer and a TLR3 agonist, can be used as a vaccine adjuvant to enhance adaptive immunity. However, the antigen-specific CD8 T-cell response to peptide vaccination and poly(I:C) has not been clearly defined. Here, the authors characterized the antigen-specific CD8 T-cell response to peptide vaccination and poly(I:C) and specifically addressed the hypothesis that poly(I:C) can enhance antitumor immunity. To define the antigen-specific T-cell response, the authors established a model based on the adoptive transfer of T cells from the OT-1 T-cell receptor transgenic mouse. In this model, vaccination with peptide alone resulted in a limited, transient expansion of antigen-specific CD8 T cells. In contrast, peptide vaccination with concomitant administration of poly(I:C) resulted in a dramatic sustained increase in the number of antigen-specific CD8 T cells. This increase in cell number was associated with an increase in CD8 T-cell function, as defined by specific IFN-gamma and TNF-alpha production, and protection from tumor challenge. The adjuvant effects of poly(I:C) appear to be at least partially dependent on an increase in the transcription of the anti-apoptotic molecules Bcl-3 and Bcl-xL and a concomitant decrease in apoptosis during the contraction phase of the primary T-cell response. In addition, administration of poly(I:C) enhanced the response to a nonimmunogenic self-antigen in a dendritic cell vaccine-based vaccine strategy. Collectively, these results confirm the potential of poly(I:C) as a vaccine adjuvant and suggest that targeting of TLR3 is likely to be a valuable addition to peptide-based vaccination strategies.

Induction of human papilloma virus E6/E7-specific cytotoxic T-lymphocyte activity in immune-tolerant, E6/E7-transgenic mice

Despite promising preclinical results of various therapeutic anticancer immunization strategies, these approaches may not be effective enough to eradicate tumors in cancer patients. While most animal models are based on fast-growing transplantable tumors, malignancies in, for example, cervical cancer patients in general develop much more slowly, which may lead to immune suppression and/or immune tolerance. As a consequence, the immunomodulating signal of any therapeutic immunization regimen should be sufficiently potent to overcome this immunocompromised condition. In previous studies, we demonstrated that an experimental vaccine against human papillomavirus (HPV)-induced cervical cancer, based on Semliki Forest virus (SFV), induces robust HPV-specific cellular immune responses in mice. Now we studied whether this strategy is potent enough to also prime a cellular immune response in immune-tolerant HPV transgenic mice, in which CTL activity cannot be induced using protein or DNA vaccines. We demonstrate that, depending on the route of immunization, SFV-expressing HPV16 E6 and E7 indeed has the capacity to induce HPV16 E7-specific cytotoxic T cells in HPV-transgenic mice.

A critical assessment of the potential of short interfering RNA therapeutics

siRNA technology is now being extensively investigated both academically and commercially as a therapeutic modality because of its ability, at low concentration, to effectively downregulate the expression of target genes in tissue culture. However, the road to therapeutic siRNAs, similar to antisense oligodeoxyribonucleotides, an older technology that is also based on Watson-Crick base-pair complementation and which have not performed well in the clinic, will undoubtedly be long and challenging despite the initial enthusiasm.:

Genetic differentiation of poly I:C from B:9-23 peptide induced experimental autoimmune diabetes

Type 1 diabetes is an immune-mediated disease, in which T cells of the adaptive immune system mediate beta cell destruction. Recently the innate immune system has been linked to etiopathogenesis of several autoimmune diseases including type 1 diabetes, as innate effector cells (e.g. dendritic cells, monocytes/macrophages and NK cells) can prime and promote or regulate (auto)immune responses. We have previously developed an experimental autoimmune diabetes (EAD) model with insulin peptide B:9-23 immunization in transgenic H-2(d)mice expressing the costimulatory molecule B7.1 in their islets (under the Rat Insulin Promotor, RIP). We compared the induction of diabetes with polyinosinic-polycytidylic acid (Poly I:C), a mimic of double stranded viral RNA versus insulin B:9-23 peptide in mice following backcrossing of the B7.1 transgene on to BALB/c mice from original B7.1 C57Bl/6 mice. We find that diabetes induction by Poly I:C is C57Bl/6 associated, whereas B:9-23 peptide induced diabetes and induction of insulin autoantibodies (IAA) are dependent on BALB/c genes. This B:9-23 peptide induced diabetes is consistent with MHC class II H-2(d)being necessary for the response to this peptide. Of note Poly I:C induction of diabetes was lost while B:9-23 induction was retained with backcrossing to BALB/c mice. Interaction of genes and environment (antigenic epitope and viral mimic) can be important in the pathogenesis of immune mediated diabetes and activation of the innate immune system (e.g. Poly I:C) may be one key determinant.

Toll-like receptor ligands: hygiene, atopy and therapeutic implications

PURPOSE OF REVIEW

Allergic and certain other inflammatory diseases have become more common in industrialized countries over the past few decades. One potential explanation for such trends is that with a decreased incidence of microbial exposures, as a result of modern public health practices, an important source of immune stimulation has been lost, with a consequent increase in inflammatory responses and their associated diseases. This review will focus on our current understanding of how microbial exposures impact on host immunity and the pathogenesis of allergic diseases.

RECENT FINDINGS

In the past decade, it has become clear that a number of molecular interactions between immunocytes and microbial compounds are mediated by Toll-like receptors on host cells. Moreover, recent investigations have suggested that ligands for different Toll-like receptors have the potential both to inhibit and promote the development of allergic hypersensitivities and diseases.

SUMMARY

On the basis of studies discussed herein, we speculate that physiological exposures to Toll-like receptor ligands have important yet complex effects on immune homeostasis and host susceptibility towards atopic diseases. Moreover, we anticipate that a fuller understanding of how physiological Toll-like receptor ligand exposures impact on immune development will lead to novel therapeutic interventions for the prevention and treatment of atopic diseases.

Molecular and cellular control of T1/T2 immunity at the interface between antimicrobial defense and immune pathology

The immune system evolved to rapidly recognize infectious threats and promptly mobilize cellular effectors to the infection site. Establishment of a robust T1-type immunity is a prerequisite for effective defense against most viruses and intracellular bacteria. However, accumulating evidence shows that T1 and T2 responses during such infections are not mutually exclusive. A possibility may be that the dual T1-T2 nature of antiviral immune responses is merely a byproduct of less than perfect crossregulatory mechanisms. Herein, we discuss molecular and cellular mechanisms of T-cell differentiation along with recent evidence supporting the hypothesis that rather than representing an epiphenomenon, coinduction of virus-specific T2 cells plays a significant homeostatic role. Thus, molecular pathways that regulate IL-4 production during influenza virus infection monitor T1-mediated immune responses in vital organs such as lungs and prevent immune pathology that may otherwise interfere with recovery from disease. Such evidence suggests that coinduction of T2 immunity maintains immune homeostasis during T1-mediated defense reactions. Finally, we outline implications on the earlier concept of T1/T2 dichotomy, supporting a model in which these two subsets, rather than being mutually antagonistic, together facilitate the recovery from infection.

Superior Therapeutic Efficacy of Alphavirus-Mediated Immunization against Human Papilloma Virus Type 16 Antigens in a Murine Tumour Model: Effects of the Route of Immunization

In our efforts to develop a strong, effective immune response against cervical carcinoma and premalignant disease, we study the use of recombinant Semliki Forest virus (SFV) encoding the oncoproteins E6 and E7 from high-risk human papilloma viruses (HPVs). Optimal immunization conditions are required for immunotherapeutic treatment of cervical cancer as it has been postulated that cervical cancer patients are immune-suppressed and/or immunologically tolerant for HPV. We previously generated an optimized construct encoding a fusion protein of HPV16 E6 and E7 and a translational enhancer (enhE6,7). Immunization of mice with SFV-enhE6,7 was shown to induce cytoxic T cell (CTL) responses and resulted in the eradication of established tumours. We now demonstrate, using HPV16-specific MHC class I tetramers, that high pCTL frequencies can be induced. However, this induction is strongly influenced by the route of immunization applied. Whilst in bulk CTL assays, requiring in vitro restimulation, CTL activity can be observed upon sc, ip, iv and im immunization, detectable pCTL frequencies, without in vitro restimulation, are only induced upon im and iv immunization. The route of immunization also strongly influences the dose of viral vector needed to induce CTLs and tumour therapy. As few as 5x104 SFV-enhE6,7, primed and boosted iv, are needed to eradicate tumours in six out of seven mice treated. Furthermore, exponentially growing tumours of approximately 500 mm3 in size were seen to completely resolve and even tumours as large as 1500 mm3 decreased to one-third of their size. Apart from this potency, SFV vectors can safely be used for the expression of oncoproteins such as E6 and E7, since the viral RNA is not integrated in the host genome. Thus SFV-enhE6,7 meets with the criteria that a vaccine against cervical cancer should be safe and induce a very strong, long-lasting CTL response, strong enough to eradicate existing tumours.

HIV-1-infected monocyte-derived dendritic cells do not undergo maturation but can elicit IL-10 production and T cell regulation

Dendritic cells (DCs) undergo maturation during virus infection and thereby become potent stimulators of cell-mediated immunity. HIV-1 replicates in immature DCs, but we now find that infection is not accompanied by many components of maturation in either infected cells or uninfected bystanders. The infected cultures do not develop potent stimulating activity for the mixed leukocyte reaction (MLR), and the DCs producing HIV-1 gag p24 do not express CD83 and DC-lysosome-associated membrane protein maturation markers. If different maturation stimuli are applied to DCs infected with HIV-1, the infected cells selectively fail to mature. When DCs from HIV-1-infected patients are infected and cultured with autologous T cells, IL-10 was produced in 6 of 10 patients. These DC-T cell cocultures could suppress another immune response, the MLR. The regulation was partially IL-10-dependent and correlated in extent with the level of IL-10 produced. Suppressor cells only developed from infected patients, rather than healthy controls, and the DCs had to be exposed to live virus rather than HIV-1 gag peptides or protein. These results indicate that HIV-1-infected DCs have two previously unrecognized means to evade immune responses: maturation can be blocked reducing the efficacy of antigen presentation from infected cells, and T cell-dependent suppression can be induced.

Immune responsiveness, tolerance and dsRNA: implications for traditional paradigms

Double-stranded (ds)RNA motifs are central to immune regulation and block tolerance to tumor-associated, self- and foreign antigens. In addition, they could explain why DNA vectors encoding self-replicating mRNA (replicons) are more immunogenic than conventional DNA vaccines. Accumulating evidence on the immunomodulatory roles of dsRNAs warrants a reconsideration of various models of immune homeostasis.

Infection-triggered regulatory mechanisms override the role of STAT 4 in control of the immune response to influenza virus antigens

Accurate control of the balance of the T1 and T2 cells during antiviral immunity is essential for optimizing immune effector functions and for avoiding potentially severe immunopathology. We examined the in vivo role of the signal transducer and activator of transcription (STAT) 4 in regulating the T1/T2 balance during the response to live influenza virus and isolated viral proteins. We found that the differentiation of gamma interferon (IFN-gamma)-producing Th1 and Tc1 cells after inoculation of live virus occurred independently of STAT 4 expression. Influenza virus-specific T2 and Tc2 responses were well controlled in such STAT 4-deficient mice unless IFN-gamma was eliminated as well. In contrast, the STAT 4-dependent signaling pathway played a more essential role in regulating the T1/T2 balance after immunization with viral proteins and, in particular, inactivated nonreplicating virus. Pulmonary infection was cleared even in the absence of both functional STAT 4 genes and functional IFN-gamma genes because virus-neutralizing antibodies were still generated, consistent with a substantial redundancy in different antiviral effector pathways. Thus, replicating agents such as live influenza virus can elicit IFN-gamma and control T2 immunity independently of STAT 4, whereas the profile of immunity to isolated proteins is more reliant on an intact STAT 4 signaling pathway.