Recombinant adenovirus induces maturation of dendritic cells via an NF-kappaB-dependent pathway

Optimal conditions for adenoviral transduction of immature dendritic cells without affecting the tolerogenic activity of DC-based immunotherapy

Dendritic cells (DCs) play a pivotal role in maintaining immune tolerance. Using recombinant adenovirus (rAd) to deliver vectors to immature dendritic cells (imDCs) is an important method for studying the tolerogenic function of DCs. We found that using RPMI medium and a higher MOI during transduction increased the expression of CD80, CD86, and MHC-II on the surface of imDCs. Our data reveal a significant increase in the secretion of the pro-inflammatory cytokine IL-6 in the group showing the most pronounced phenotypic changes. In the mouse heart transplant model, imDCs with unstable phenotype and function due to adenoviral transduction resulted in an increased proportion of Th1 and Th17 cells in recipients. However, these effects can be managed, and our proposed optimized transduction strategy significantly minimizes these adverse effects. Our study holds significant implications for the development and optimization of immunotherapy utilizing tolerogenic dendritic cells.

Harnessing adenovirus in cancer immunotherapy: evoking cellular immunity and targeting delivery in cell-specific manner

Recombinant adenovirus (rAd) regimens, including replication-competent oncolytic adenovirus (OAV) and replication-deficient adenovirus, have been identified as potential cancer therapeutics. OAV presents advantages such as selective replication, oncolytic efficacy, and tumor microenvironment (TME) remodeling. In this perspective, the principles and advancements in developing OAV toolkits are reviewed. The burgeoning rAd may dictate efficacy of conventional cancer therapies as well as cancer immunotherapies, including cancer vaccines, synergy with adoptive cell therapy (ACT), and TME reshaping. Concurrently, we explored the potential of rAd hitchhiking to adoptive immune cells or stem cells, highlighting how this approach facilitates synergistic interactions between rAd and cellular therapeutics at tumor sites. Results from preclinical and clinical trials in which immune and stem cells were infected with rAd have been used to address significant oncological challenges, such as postsurgical residual tumor tissue and metastatic tissue. Briefly, rAd can eradicate tumors through various mechanisms, resulting from tumor immunogenicity, reprogramming of the TME, enhancement of cellular immunity, and effective tumor targeting. In this context, we argue that rAd holds immense potential for enhancing cellular immunity and synergistically improving antitumor effects in combination with novel cancer immunotherapies.

Adenoviral vector-based platforms for developing effective vaccines to combat respiratory viral infections

Since the development of the first vaccine against smallpox over two centuries ago, vaccination strategies have been at the forefront of significantly impacting the incidences of infectious diseases globally. However, the increase in the human population, deforestation and climate change, and the rise in worldwide travel have favored the emergence of new viruses with the potential to cause pandemics. The ongoing severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) pandemic is a cruel reminder of the impact of novel pathogens and the suboptimal capabilities of conventional vaccines. Therefore, there is an urgent need to develop new vaccine strategies that allow the production of billions of doses in a short duration and are broadly protective against emerging and re-emerging infectious diseases. Extensive knowledge of the molecular biology and immunology of adenoviruses (Ad) has favored Ad vectors as platforms for vaccine design. The Ad-based vaccine platform represents an attractive strategy as it induces robust humoral and cell-mediated immune responses and can meet the global demand in a pandemic situation. This review describes the status of Ad vector-based vaccines in preclinical and clinical studies for current and emerging respiratory viruses, particularly coronaviruses, influenza viruses and respiratory syncytial viruses.

Coagulopathies after Vaccination against SARS-CoV-2 May Be Derived from a Combined Effect of SARS-CoV-2 Spike Protein and Adenovirus Vector-Triggered Signaling Pathways

Novel coronavirus SARS-CoV-2 has resulted in a global pandemic with worldwide 6-digit infection rates and thousands of death tolls daily. Enormous efforts are undertaken to achieve high coverage of immunization to reach herd immunity in order to stop the spread of SARS-CoV-2 infection. Several SARS-CoV-2 vaccines based on mRNA, viral vectors, or inactivated SARS-CoV-2 virus have been approved and are being applied worldwide. However, the recent increased numbers of normally very rare types of thromboses associated with thrombocytopenia have been reported, particularly in the context of the adenoviral vector vaccine ChAdOx1 nCoV-19 from Astra Zeneca. The statistical prevalence of these side effects seems to correlate with this particular vaccine type, i.e., adenoviral vector-based vaccines, but the exact molecular mechanisms are still not clear. The present review summarizes current data and hypotheses for molecular and cellular mechanisms into one integrated hypothesis indicating that coagulopathies, including thromboses, thrombocytopenia, and other related side effects, are correlated to an interplay of the two components in the vaccine, i.e., the spike antigen and the adenoviral vector, with the innate and immune systems, which under certain circumstances can imitate the picture of a limited COVID-19 pathological picture.

Optimized Adenoviral Vector That Enhances the Assembly of FMDV O1 Virus-Like Particles in situ Increases Its Potential as Vaccine for Serotype O Viruses

Although replication-defective human adenovirus type 5 (Ad5) vectors that express in situ the capsid-encoding region of foot-and-mouth disease virus (FMDV) have been proven to be effective as vaccines in relevant species for several viral strains, the same result was not consistently achieved for the O1/Campos/Brazil/58 strain. In the present study, an optimization of the Ad5 system was explored and was proven to enhance the expression of FMDV capsid proteins and their association into virus-like particles (VLPs). Particularly, we engineered a novel Ad5 vector (Ad5[PVP2]OP) which harbors the foreign transcription unit in a leftward orientation relative to the Ad5 genome, and drives the expression of the FMDV sequences from an optimized cytomegalovirus (CMV) enhancer-promoter as well. The Ad5[PVP2]OP vaccine candidate also contains the amino acid substitutions S93F/Y98F in the VP2 protein coding sequence, predicted to stabilize FMD virus particles. Cells infected with the optimized vector showed an ∼14-fold increase in protein expression as compared to cells infected with an unmodified Ad5 vector tested in previous works. Furthermore, amino acid substitutions in VP2 protein allowed the assembly of FMDV O1/Campos/Brazil/58 VLPs. Evaluation of several serological parameters in inoculated mice with the optimized Ad5[PVP2]OP candidate revealed an enhanced vaccine performance, characterized by significant higher titers of neutralizing antibodies, as compared to our previous unmodified Ad5 vector. Moreover, 94% of the mice vaccinated with the Ad5[PVP2]OP candidate were protected from homologous challenge. These results indicate that both the optimized protein expression and the stabilization of the in situ generated VLPs improved the performance of Ad5-vectored vaccines against the FMDV O1/Campos/Brazil/58 strain and open optimistic expectations to be tested in target animals.

Adenoviral Vector-Based Vaccine Platforms for Developing the Next Generation of Influenza Vaccines

Ever since the discovery of vaccines, many deadly diseases have been contained worldwide, ultimately culminating in the eradication of smallpox and polio, which represented significant medical achievements in human health. However, this does not account for the threat influenza poses on public health. The currently licensed seasonal influenza vaccines primarily confer excellent strain-specific protection. In addition to the seasonal influenza viruses, the emergence and spread of avian influenza pandemic viruses such as H5N1, H7N9, H7N7, and H9N2 to humans have highlighted the urgent need to adopt a new global preparedness for an influenza pandemic. It is vital to explore new strategies for the development of effective vaccines for pandemic and seasonal influenza viruses. The new vaccine approaches should provide durable and broad protection with the capability of large-scale vaccine production within a short time. The adenoviral (Ad) vector-based vaccine platform offers a robust egg-independent production system for manufacturing large numbers of influenza vaccines inexpensively in a short timeframe. In this review, we discuss the progress in the development of Ad vector-based influenza vaccines and their potential in designing a universal influenza vaccine.

Factors Which Contribute to the Immunogenicity of Non-replicating Adenoviral Vectored Vaccines

Adenoviral vectors are a safe and potently immunogenic vaccine delivery platform. Non-replicating Ad vectors possess several attributes which make them attractive vaccines for infectious disease, including their capacity for high titer growth, ease of manipulation, safety, and immunogenicity in clinical studies, as well as their compatibility with clinical manufacturing and thermo-stabilization procedures. In general, Ad vectors are immunogenic vaccines, which elicit robust transgene antigen-specific cellular (namely CD8+ T cells) and/or humoral immune responses. A large number of adenoviruses isolated from humans and non-human primates, which have low seroprevalence in humans, have been vectorized and tested as vaccines in animal models and humans. However, a distinct hierarchy of immunological potency has been identified between diverse Ad vectors, which unfortunately limits the potential use of many vectors which have otherwise desirable manufacturing characteristics. The precise mechanistic factors which underlie the profound disparities in immunogenicity are not clearly defined and are the subject of ongoing, detailed investigation. It has been suggested that a combination of factors contribute to the potent immunogenicity of particular Ad vectors, including the magnitude and duration of vaccine antigen expression following immunization. Furthermore, the excessive induction of Type I interferons by some Ad vectors has been suggested to impair transgene expression levels, dampening subsequent immune responses. Therefore, the induction of balanced, but not excessive stimulation of innate signaling is optimal. Entry factor binding or receptor usage of distinct Ad vectors can also affect their in vivo tropism following administration by different routes. The abundance and accessibility of innate immune cells and/or antigen-presenting cells at the site of injection contributes to early innate immune responses to Ad vaccination, affecting the outcome of the adaptive immune response. Although a significant amount of information exists regarding the tropism determinants of the common human adenovirus type-5 vector, very little is known about the receptor usage and tropism of rare species or non-human Ad vectors. Increased understanding of how different facets of the host response to Ad vectors contribute to their immunological potency will be essential for the development of optimized and customized Ad vaccine platforms for specific diseases.

The transcription factor Foxp1 regulates the differentiation and function of dendritic cells

Dendritic cells (DCs) are the sentinels of the immune system and play a critical role in initiating adaptive immune responses against pathogens. As the most powerful antigen presenting cells, DCs are also important in maintaining immune homeostasis and participating in the development of autoimmune diseases. How the maturation and function of DCs is regulated in these conditions and what is the function of various transcription factors is still unclear. In this study, we found that the expression of the transcription factor Foxp1 gradually increased during the maturation of DCs. Then, we constructed a recombinant adenovirus carrying Foxp1-interfering RNA (Ad-simFoxp1) and transfected murine bone marrow-derived DCs in vitro. DCs transfected with Ad-simFoxp1 exhibited markedly lower costimulatory molecules, and decreased cytokines. And Ad-simFoxp1 greatly inhibited mature DC-induced T cell responses. Moreover, in vivo infusion with Ad-simFoxp1-modified DCs significantly delayed the onset of experimental autoimmune encephalomyelitis (EAE). Therefore, adoptive transfection of Ad-simFoxp1 in DCs may be a potential treatment strategy against autoimmune diseases.

Maternal immunization with a recombinant adenovirus-expressing fusion protein protects neonatal cotton rats from respiratory syncytia virus infection by transferring antibodies via breast milk and placenta

We evaluated the efficacy of a recombinant adenovirus that expresses a membrane-truncated respiratory syncytial virus (RSV) fusion protein (Ad-F0ΔTM) in newborns via maternal immunization (MI) of pregnant cotton rats. Intranasal Ad-F0ΔTM immunization was given to pregnant female rats, and MI-newborn rats were then challenged intranasally with RSV. Anti-RSV IgGs were observed in the serum of MI-newborn rats after birth. The pulmonary viral loads in Ad-F0ΔTM vs. control vector, Ad-LacZ, and MI-newborns on day 3 post-challenge were reduced by 4 log₁₀/g lung. The neutralizing antibody remained for up to 3 weeks in the serum of MI-newborns, which is when weaning began. Ad-F0ΔTM protected MI-newborns from RSV challenge for 1 week. Vertical-transferred protective antibodies were examined in the breast milk and placenta as well. Finally, anti-RSV immunity was not boosted but was only primed during the next RSV exposure in Ad-F0ΔTM-MI-newborns. Maternal Ad-F0ΔTM immunization provides acute protection against RSV infection in neonates.

Antitumor efficacy of the Runx2-dendritic cell vaccine in triple-negative breast cancer in vitro

Triple-negative breast cancer (TNBC) is a subtype of breast cancer with a poor prognosis and limited effective treatment. The rise in immunotherapeutic strategies prompted the establishment of a genetic vaccine against TNBC in vitro using a possible biological marker of TNBC. In the present study, different detection methods were used to evaluate the distribution and expression of runt-associated transcription factor 2 (Runx2) in various breast cancer cell lines. Following the development of the Runx2-dendritic cell (DC) vaccine using a lentivirus, the transfection efficacy was recorded. The T lymphocytes co-cultured with the vaccine were collected to assess the antitumor potency. Increased levels of Runx2 were expressed in breast cancer cells; however, different breast cancer cell lines expressed various levels of Runx2. Runx2 demonstrated particularly high expression in TNBC cells, compared with non-TNBC cells. A Runx2 lentivirus transfection system was successfully engineered, and Runx2 was transduced into dendritic cells whilst maintaining stable expression. The sustained and stable cytotoxic T cells induced in the transfected group had higher and more specific antitumor efficacy against TNBC, compared with the other cell lines. Runx2 may be a novel target for TNBC treatment. The Runx2-DC vaccine may induce specific and efficient antitumor effects in TNBC in vitro.

Update on Dendritic Cell-Induced Immunological and Clinical Tolerance

Dendritic cells (DCs) as highly efficient antigen-presenting cells are at the interface of innate and adaptive immunity. As such, they are key mediators of immunity and antigen-specific immune tolerance. Due to their functional specialization, research efforts have focused on the characterization of DCs subsets involved in the initiation of immunogenic responses and in the maintenance of tissue homeostasis. Tolerogenic DCs (tolDCs)-based therapies have been designed as promising strategies to prevent and control autoimmune diseases as well as allograft rejection after solid organ transplantation (SOT). Despite successful experimental studies and ongoing phase I/II clinical trials using autologous tolDCs in patients with type 1 diabetes, rheumatoid arthritis, multiple sclerosis, and in SOT recipients, additional basic research will be required to determine the optimal DC subset(s) and conditioning regimens for tolDCs-based treatments in vivo. In this review, we discuss the characteristics of human DCs and recent advances in their classification, as well as the role of DCs in immune regulation and their susceptibility to in vitro or in vivo manipulation for the development of tolerogenic therapies, with a focus on the potential of tolDCs for the treatment of autoimmune diseases and the prevention of allograft rejection after SOT.

Immunodepletion and Hypoxia Preconditioning of Mouse Compact Bone Cells as a Novel Protocol to Isolate Highly Immunosuppressive Mesenchymal Stem Cells

Compact bones (CB) are major reservoirs of mouse mesenchymal stem cells (mMSC). Here, we established a protocol to isolate MSC from CB and tested their immunosuppressive potential. Collagenase type II digestion of BM-flushed CB from C57B/6 mice was performed to liberate mMSC precursors from bone surfaces to establish nondepleted mMSC. CB cells were also immunodepleted based on the expression of CD45 (leukocytes) and TER119 (erythroid cells) to eliminate hematopoietic cells. CD45^-TER119^- CB cells were subsequently used to generate depleted mMSC. CB nondepleted and depleted mMSC progenitors were cultured under hypoxic conditions to establish primary mMSC cultures. CB depleted mMSC compared to nondepleted mMSC showed greater cell numbers at subculturing and had increased functional ability to differentiate into adipocytes and osteoblasts. CB depleted mMSC had high purity and expressed key mMSC markers (>85% Sca-1, CD29, CD90) with no mature hematopoietic contaminating cells (<5% CD45, CD11b) when subcultured to passage 5 (P5). Nondepleted mMSC cultures, however, were less pure and heterogenous with <72% Sca-1⁺, CD29⁺, and CD90⁺ cells at early passages (P1 or P2), along with high percentages of contaminating CD11b⁺ (35.6%) and CD45⁺ (39.2%) cells that persisted in culture long term. Depleted and nondepleted mMSC nevertheless exhibited similar potency to suppress total (CD3⁺), CD4⁺ and CD8⁺ T cell proliferation, in a dendritic cell allostimulatory one-way mixed lymphocyte reaction. CB depleted mMSC, pretreated with proinflammatory cytokines IFN-γ, TNF-α, and IL-17A, showed superior suppression of CD8⁺ T cell, but not CD4⁺ T cell proliferation, relative to untreated-mMSC. In conclusion, CB depleted mMSC established under hypoxic conditions and treated with selective cytokines represent a novel source of potent immunosuppressive MSC. As these cells have enhanced immune modulatory function, they may represent a superior product for use in clinical allotransplantation.

LPS, dsRNA and the interferon bridge to adaptive immune responses: Trif, Tram, and other TIR adaptor proteins

Toll-like receptors (TLRs) expressed on antigen-presenting cells (APCs), form a critical link between innate and the adaptive immune responses. Activation of TLRs by LPS and dsRNA results in up-regulation of co-stimulatory molecules (UCM) essential for the generation of robust T-cell responses. It is now evident that type I interferons (IFNs) play an important role in UCM and in the subsequent maturation of APCs. The recently identified adaptor molecules Trif and Tram, unlike their counterparts MyD88 and MAL/Tirap, induce type I IFN via the TLR4 signaling pathway, whereas Trif appears to be the sole adaptor molecule involved in TLR3 signaling, resulting in subsequent production of type I IFN. Here, we discuss how Trif and type I IFN are involved in the optimization of APC-T cell interaction in response not only to viral but also bacterial stimuli.

Efficient induction of cross-presentating human B cell by transduction with human adenovirus type 7 vector

Although human autologous B cells represent a promising alternative to dendritic cells (DCs) for easy large-scale preparation, the naive human B cells are always poor at antigen presentation. The safe and effective usage record of human adenovirus type 7 (HAdV7) live vaccines makes it attractive as a promising vaccine vector candidate. To investigate whether HAdV7 vector could be used to induce the human B cells cross-presentation, in the present study, we constructed the E3-defective recombinant HAdV7 vector encoding green fluorescent protein (GFP) and carcinoembryonic antigen (CEA). We demonstrated that naive human B cells can efficiently be transduced, and that the MAPKs/NF-κB pathway can be activated by recombinant HAdV7. We proved that cytokine TNF-α, IL-6 and IL-10, surface molecule MHC class I and the CD86, antigen-processing machinery (APM) compounds ERp57, TAP-1, and TAP-2. were upregulated in HAdV7 transduced human B cells. We also found that CEA-specific IFNγ expression, degranulation, and in vitro and ex vivo cytotoxicities are induced in autologous CD8(+) T cells presensitized by HAd7CEA modified human B cells. Meanwhile, our evidences clearly show that Toll-like receptors 9 (TLR9) antagonist IRS 869 significantly eliminated most of the HAdV7 initiated B cell activation and CD8(+) T cells response, supporting the role and contribution of TLR9 signaling in HAdV7 induced human B cell cross-presentation. Besides a better understanding of the interactions between recombinant HAdV7 and human naive B cells, to our knowledge, the present study provides the first evidence to support the use of HAdV7-modified B cells as a vehicle for vaccines and immunotherapy.

The Woodchuck, a Nonprimate Model for Immunopathogenesis and Therapeutic Immunomodulation in Chronic Hepatitis B Virus Infection

The woodchuck hepatitis virus (WHV) and its host, the eastern woodchuck, is a very valuable model system for hepatitis B virus infection. Many aspects of WHV replication and pathogenesis resemble acute and chronic hepatitis B infection in patients. Since the establishment of immunological tools, woodchucks were used to develop new therapeutic vaccines and immunomodulatory approaches to treat chronic hepadnaviral infections. Combination therapy of nucleos(t)ide analogs, with prime-boost vaccination and triple therapy, including immunomodulatory strategies by blocking the interaction of the programmed death-1 (PD-1) receptor with its ligand inducing a potent T-cell response in chronic WHV carrier woodchucks, suppression of viral replication, and complete elimination of the virus in 30% of the animals. Both strategies may be used for future therapies in patients with chronic hepatitis B.

Immunotherapy for Lewis lung carcinoma utilizing dendritic cells infected with CK19 gene recombinant adenoviral vectors

Dendritic cells (DCs) as 'professional' antigen-presenting cells (APCs) initiate and regulate immune responses to various antigens. DC-based vaccines have become a promising modality in cancer immunotherapy. Cytokeratin 19 (CK19) protein is expressed at high levels in lung cancer and many other tumor cells, suggesting CK19 as a potential tumor-specific target for cancer immune therapy. We constructed a recombinant adenoviral vector containing the CK19 gene (rAd-CK19). DCs transfected with rAd-CK19 were used to vaccinate C57BL/6 mice bearing xenografts derived from Lewis lung carcinoma (LLC) cells. The transfected DCs gave rise to potent CK19-specific cytotoxic T lymphocytes (CTLs) capable of lysing LLC cells. Mice immunized with the rAd-CK19-DCs exhibited significantly attenuated tumor growth (including tumor volume and weight) when compared to the tumor growth of mice immunized with rAd-c DCs or DCs during the 24-day observation period (P<0.05). The results revealed that the mice vaccinated with the rAd-CK19-DCs exhibited a potent protective and therapeutic antitumor immunity to LLC cells in the subcutaneous model along with an inhibitive effect on tumor growth compared to the mice vaccinated with the rAd-c DCs or DCs alone. The present study proposes a meaningful mode of action utilizing rAd-CK19 DCs in lung cancer immunotherapy.

Viral vaccines and their manufacturing cell substrates: New trends and designs in modern vaccinology

Vaccination is one of the most effective interventions in global health. The worldwide vaccination programs significantly reduced the number of deaths caused by infectious agents. A successful example was the eradication of smallpox in 1979 after two centuries of vaccination campaigns. Since the first variolation administrations until today, the knowledge on immunology has increased substantially. This knowledge combined with the introduction of cell culture and DNA recombinant technologies revolutionized vaccine design. This review will focus on vaccines against human viral pathogens, recent developments on vaccine design and cell substrates used for their manufacture. While the production of attenuated and inactivated vaccines requires the use of the respective permissible cell substrates, the production of recombinant antigens, virus‐like particles, vectored vaccines and chimeric vaccines requires the use – and often the development – of specific cell lines. Indeed, the development of novel modern viral vaccine designs combined with, the stringent safety requirements for manufacture, and the better understanding on animal cell metabolism and physiology are increasing the awareness on the importance of cell line development and engineering areas. A new era of modern vaccinology is arriving, offering an extensive toolbox to materialize novel and creative ideas in vaccine design and its manufacture.

Human coagulation factor X-adenovirus type 5 complexes poorly stimulate an innate immune response in human mononuclear phagocytes

One of the first lines of host defense against many viruses in vertebrates is the innate immune system, which detects pathogen-associated molecular patterns (PAMPs) using pathogen recognition receptors (PRR). The dynamic interactions between pathogens and hosts create, in some cases, species-specific relationships. Recently, it was shown that murine factor X (mFX)-armored human adenovirus (HAd) stimulated a mFX-Toll-like receptor 4 (TLR4)-associated response in mouse macrophages in vitro and in vivo. Given the importance of studies using animals to better understand host-pathogen interactions, we asked if human FX (hFX)-armored HAd type 5 (HAd5) was capable of activating innate immune sensors in primary human mononuclear phagocytes. To this end, we assayed human mononuclear phagocytes for their ability to be stimulated by hFX-armored HAd5 via a TLR/NF-κB pathway, in particular, a TLR4 pathway. In our hands, we found no significant interaction, activation, or maturation of human mononuclear phagocytes caused by the presence of hFX-armored HAd5.

IMPORTANCE

Animals, and mice in particular, are often used as informative and powerful surrogates for how pathogens interact with natural host systems. When possible, extended and targeted studies in the natural host can then be performed. Our data will help us understand the differences in preclinical testing in mice and clinical use in humans in order to improve treatment for HAd diseases and Ad vector effectiveness.

Therapeutic vaccination and immunomodulation in the treatment of chronic hepatitis B: preclinical studies in the woodchuck

Infection with hepatitis B virus (HBV) may lead to subclinical, acute or chronic hepatitis. In the prevaccination era, HBV infections were endemic due to frequent mother to child transmission in large regions of the world. However, there are still estimated 240 million chronic HBV carriers today and ca. 620,000 patients die per year due to HBV-related liver diseases. Recommended treatment of chronic hepatitis B with interferon-α and/or nucleos(t)ide analogues does not lead to satisfactory results. Induction of HBV-specific T cells by therapeutic vaccination or immunomodulation may be an innovative strategy to overcome virus persistence. Vaccination with commercially available HBV vaccines in patients with or without therapeutic reduction of viral load did not result in effective immune control of HBV infection, suggesting that combination of antiviral treatment with new formulations of therapeutic vaccines is needed. The woodchuck (Marmota monax) and its HBV-like woodchuck hepatitis virus are a useful preclinical animal model for developing new therapeutic approaches in chronic hepadnaviral infections. Several innovative approaches combining antiviral treatments using nucleos(t)ide analogues, with prime-boost vaccination using DNA vaccines, new hepadnaviral antigens or recombinant adenoviral vectors were tested in the woodchuck model. In this review, we summarize these encouraging results obtained with these therapeutic vaccines. In addition, we present potential innovations in immunostimulatory strategies by blocking the interaction of the inhibitory programmed death receptor 1 with its ligand in this animal model.

Transgene IL-6 enhances DC-stimulated CTL responses by counteracting CD4+25+Foxp3+ regulatory T cell suppression via IL-6-induced Foxp3 downregulation

Dendritic cells (DCs), the most potent antigen-presenting cells have been extensively applied in clinical trials for evaluation of antitumor immunity. However, the efficacy of DC-mediated cancer vaccines is still limited as they are unable to sufficiently break the immune tolerance. In this study, we constructed a recombinant adenoviral vector (AdVIL-6) expressing IL-6, and generated IL-6 transgene-engineered DC vaccine (DCOVA/IL-6) by transfection of murine bone marrow-derived ovalbumin (OVA)-pulsed DCs (DCOVA) with AdVIL-6. We then assessed DCOVA/IL-6-stimulated cytotoxic T-lymphocyte (CTL) responses and antitumor immunity in OVA-specific animal tumor model. We demonstrate that DCOVA/IL-6 vaccine up-regulates expression of DC maturation markers, secretes transgene-encoded IL-6, and more efficiently stimulates OVA-specific CTL responses and therapeutic immunity against OVA-expressing B16 melanoma BL6-10OVA in vivo than the control DCOVA/Null vaccine. Moreover, DCOVA/IL-6-stimulated CTL responses were relatively maintained in mice with transfer of CD4+25+Foxp3+ Tr-cells, but significantly reduced when treated with anti-IL-6 antibody. In addition, we demonstrate that IL-6 down-regulates Foxp3-expression of CD4+25+Foxp3+ Tr-cells in vitro. Taken together, our results demonstrate that AdV-mediated IL-6 transgene-engineered DC vaccine stimulates potent CTL responses and antitumor immunity by counteracting CD4+25+ Tr immunosuppression via IL-6-induced Foxp3 down-regulation. Thus, IL-6 may be a good candidate for engineering DCs for cancer immunotherapy.

Dendritic cell-based approaches for therapeutic immune regulation in solid-organ transplantation

To avoid immune rejection, allograft recipients require drug-based immunosuppression, which has significant toxicity. An emerging approach is adoptive transfer of immunoregulatory cells. While mature dendritic cells (DCs) present donor antigen to the immune system, triggering rejection, regulatory DCs interact with regulatory T cells to promote immune tolerance. Intravenous injection of immature DCs of either donor or host origin at the time of transplantation have prolonged allograft survival in solid-organ transplant models. DCs can be treated with pharmacological agents before injection, which may attenuate their maturation in vivo. Recent data suggest that injected immunosuppressive DCs may inhibit allograft rejection, not by themselves, but through conventional DCs of the host. Genetically engineered DCs have also been tested. Two clinical trials in type-1 diabetes and rheumatoid arthritis have been carried out, and other trials, including one trial in kidney transplantation, are in progress or are imminent.

Rapamycin augments human DC IL-12p70 and IL-27 secretion to promote allogeneic Type 1 polarization modulated by NK cells

Mammalian target of rapamycin kinase inhibitor (mTORi) rapamycin (RAPA) use in transplantation can lead to inflammatory complications in some patients. Our goal was to better understand how mTORi-exposed human monocyte-derived dendritic cells (DC) stimulated with pro-inflammatory cytokines shape T cell allo-immunity. RAPA-conditioned-DC (RAPA-DC) displayed a more immature phenotype than untreated, control (CTRL)-DC. However, subsequent exposure of RAPA-DC to an inflammatory cytokine cocktail (ICC) plus IFN-γ induced a mature Type-1 promoting phenotype, consisting of elevated HLA-DR and co-stimulatory molecules, augmented IL-12p70 and IL-27 production, but decreased IL-10 secretion compared to CTRL-DC. Co-culture of mature (m)RAPA-DC with allogeneic peripheral blood mononuclear cells resulted in significantly increased Type-1 (IFN-γ) responses by T cells. Moreover, NK cells acted as innate modulators that conveyed activating cell-to-cell contact signals in addition to helper (IFN-γ) and/or regulatory (IL-10) soluble cytokines. We conclude that production of IL12-p70, IL-27 and low IL-10 by RAPA-DC allowed us to elucidate how these cytokines as well as NK-DC interaction shapes T cell allo-immunity. Thus, lack of inhibitory NK cell function during allo-specific T cell activation by human ICC + IFN-γ-stimulated RAPA-DC may represent an unwanted effector mechanism that may underlie RAPA-induced inflammatory events in transplant patients undergoing microbial infection or allograft rejection.

Recombinant adenovirus expressing ICP47 gene suppresses the ability of dendritic cells by restricting specific T cell responses

Adenoviral vectors have been demonstrated to be one of the most effective vehicles to deliver foreign DNA into dendritic cells (DCs). However, the response of host immune systems against foreign gene products is a major obstacle to successful gene therapy. Infected cell protein 47 (ICP47) inhibits MHC Ⅰ antigen presentation pathway by binding to host transporter associated with antigen presentation (TAP), and thereby attenuates of specific cytotoxic T lymphocytes (CTLs) responses and evades the host immune clearance. This subject was designed to construct a recombinant adenovirus expressing His-tag-ICP47 fusion protein to investigate further the role of ICP47 in the elimination of transgene expression. Consequently, a recombinant adenovirus expressing the His-tag-ICP47 fusion protein was successfully constructed and it had the abilities of attenuating the stimulatory capacity of DCs by reducing the proliferation of lymphocytes and cytokine production of perforin compared with those of the r-track group and the control group. Our observations provide the first evidence of the regulation mechanism of ICP47 on DC-based immunotherapy for long-term persistence.

Recombinant mammaglobin A adenovirus-infected dendritic cells induce mammaglobin A-specific CD8+ cytotoxic T lymphocytes against breast cancer cells in vitro

Mammaglobin A (MGBA) is a novel breast cancer-associated antigen almost exclusively over-expressed in primary and metastatic human breast cancers, making it a potential therapeutic target for breast cancer. The development of dendritic cell (DC)-induced tumor antigen specific CD8⁺ cytotoxic T lymphocytes (CTLs) may hold promise in cancer immunotherapy. In this study we constructed recombinant replication-defective adenoviral (Ad) vectors encoding MGBA and evaluated their ability to trigger anti-tumor immunity in vitro. DCs were isolated from the human peripheral blood monocyte cells (PBMCs) of two HLA-A33⁺ healthy female volunteers, and infected with adenovirus carrying MGBA cDNA (Ad-MGBA). After that, the Ad-MGBA-infected DCs were used to stimulate CD8⁺ CTLs in vitro and the latter was used for co-culture with breast cancer cell lines. The data revealed that infection with Ad-MGBA improved DC maturation and up-regulated the expression of co-stimulatory molecules and the secretion of interleukin-12 (IL-12), but down-regulated interleukin-10 (IL-10) secretion from DCs. Ad-MGBA-infected DC-stimulated CD8⁺CTLs displayed the highest cytotoxicity towards HLA-A33⁺/MGBA⁺ breast cancer MDA-MB-415 cells compared with other CD8⁺CTL populations, and compared with the cytotoxicity towards HLA-A33⁻/MGBA⁺ breast cancer HBL-100 cells and HLA-A33⁻/MGBA⁻ breast cancer MDA-MB 231 cells. In addition, Ad-MGBA-infected DC-stimulated CD8⁺ CTLs showed a high level of IFNγ secretion when stimulated with HLA-A33⁺/MGBA⁺ breast cancer MDA-MB-415 cells, but not when stimulated with HLA-A33⁻/MGBA⁺ HBL-100 and HLA-A33⁻/MGBA⁻MDA-MB-231 cells. In addition, killing of CD8⁺CTLs against breast cancer was in a major histocompability complex (MHC)-limited pattern. Finally, the data also determined the importance of TNF-α in activating DCs and T cells. These data together suggest that MGBA recombinant adenovirus-infected DCs could induce specific anti-tumor immunity against MGBA⁺ breast cancers, which could provide a novel strategy in the immunotherapy of breast cancer.

Neurokinin-1 receptor agonists bias therapeutic dendritic cells to induce type 1 immunity by licensing host dendritic cells to produce IL-12

Substance-P and hemokinin-1 are proinflammatory neuropeptides with potential to promote type 1 immunity through agonistic binding to neurokinin-1 receptor (NK1R). Dendritic cells (DCs) are professional antigen-presenting cells that initiate and regulate the outcome of innate and adaptive immune responses. Immunostimulatory DCs are highly desired for the development of positive immunization techniques. DCs express functional NK1R; however, regardless of their potential DC-stimulatory function, the ability of NK1R agonists to promote immunostimulatory DCs remains unexplored. Here, we demonstrate that NK1R signaling activates therapeutic DCs capable of biasing type 1 immunity by inhibition of interleukin-10 (IL-10) synthesis and secretion, without affecting their low levels of IL-12 production. The potent type 1 effector immune response observed following cutaneous administration of NK1R-signaled DCs required their homing in skin-draining lymph nodes (sDLNs) where they induced inflammation and licensed endogenous-conventional sDLN-resident and -recruited inflammatory DCs to secrete IL-12. Our data demonstrate that NK1R signaling promotes immunostimulatory DCs, and provide relevant insight into the mechanisms used by neuromediators to regulate innate and adaptive immune responses.

Induction of CC-chemokines with antiviral function in macrophages by the human T lymphotropic virus type 2 transactivating protein, Tax2

Recent data provide evidence that co-infection with human immunodeficiency virus type 1 (HIV-1) and human T lymphotropic virus type 2 (HTLV-2) delays progression to AIDS compared to isolated HIV-1 infection. These results were linked to expression of the HTLV-2 transcriptional activating gene known as Tax2. Preliminary studies in lymphocytic systems suggest that Tax2 is responsible for induction of CC-chemokines, which play a major role in innate immune responses against HIV-1. In this study, the effect of Tax2 on CC-chemokines (MIP-1α/CCL3, MIP-1β/CCL4, and RANTES/CCL5) in monocyte-derived macrophages (MDMs) was evaluated. An immortalized human monocytic cell line (U937) and donor-derived MDMs were used to evaluate these interactions. These cells were cultured in vitro, allowed to mature into macrophages for 14 d, and treated with Tax2 or Tax1 (the transcriptional activator of HTLV-1) at three concentrations (1, 10, and 100 pM) daily thereafter. Extracellular bacterial extract (EBE) lacking the vector and untreated samples served as controls. An additional group of donor-derived MDMs were transduced with an adenovirus vector that expressed either Tax2 or green fluorescent protein (GFP). Liposomal transfection agents alone were used as controls. Supernatants were collected from each sample on multiple days post-maturation and evaluated for MIP-1α, MIP-1β, and RANTES, by enzyme-linked immunosorbent assay. Analysis of variance and Tukey's Honestly Significant Difference tests were used to analyze the results. In all systems, cells exposed to either Tax2 or Tax1 expressed significantly (p<0.01) higher concentrations of CC-chemokines than controls. There was no significant difference in chemokine expression between Tax1-treated and Tax2-treated samples, between EBE-treated and EBE-untreated samples, or between GFP-transduced MDMs and controls. This suggests that HTLV-2 could alter innate immune responses in macrophagic reservoirs of HIV-1 in HIV-1/HTLV-2 co-infected individuals, and could guide the development of HIV-1 treatments.

Canine recombinant adenovirus vector induces an immunogenicity-related gene expression profile in skin-migrated CD11b⁺ -type DCs

Gene expression profiling of the blood cell response induced early after vaccination has previously been demonstrated to predict the immunogenicity of vaccines. In this study, we evaluated whether the analysis of the gene expression profile of skin-migrated dendritic cells (DCs) could be informative for the in vitro prediction of immunogenicity of vaccine, using canine adenovirus serotype 2 (CAV2) as vaccine vector. CAV2 has been shown to induce immunity to transgenes in several species including sheep and is an interesting alternative to human adenovirus-based vectors, based on the safety records of the parental strain in dogs and the lack of pre-existing immunity in non-host species. Skin-migrated DCs were collected from pseudo-afferent lymph in sheep. Both the CD11b(+) -type and CD103(+) -type skin-migrated DCs were transduced by CAV2. An analysis of the global gene response to CAV2 in the two skin DC subsets showed that the gene response in CD11b(+) -type DCs was far higher and broader than in the CD103(+) -type DCs. A newly released integrative analytic tool from Ingenuity systems revealed that the CAV2-modulated genes in the CD11b(+) -type DCs clustered in several activated immunogenicity-related functions, such as immune response, immune cell trafficking and inflammation. Thus gene profiling in skin-migrated DC in vitro indicates that the CD11b(+) DC type is more responsive to CAV2 than the CD103(+) DC type, and provides valuable information to help in evaluating and possibly improving viral vector vaccine effectiveness.

Further reduction in adenovirus vector-mediated liver transduction without largely affecting transgene expression in target organ by exploiting microrna-mediated regulation and the Cre-loxP recombination system

In order to detarget undesirable transduction in the liver by an adenovirus (Ad) vector, we previously demonstrated that insertion of sequences perfectly complementary to liver-specific miR-122a into the 3'-untranslated region (UTR) of transgene specifically reduced the transgene expression in the liver by approximately 100-fold; however, a certain level of residual transgene expression was still found in the liver. In order to further suppress the hepatic transduction, we developed a two-Ad vector system that uses the microRNA (miRNA)-regulated transgene expression system and the Cre-loxP recombination system, i.e., insertion of miR-122a target sequences and loxP sites into the transgene expression cassette and coadministration of a Cre recombinase-expressing Ad vector. In addition, to maintain as much as possible the transgene expression in the spleen, which is the target organ of this study, spleen-specific miR-142-3p target sequences were inserted into the 3'-UTR of the Cre recombinase gene to suppress Cre recombinase expression in the spleen. The spleen is an attractive target for immunotherapy because the spleen plays important roles in the immune system. Coadministration of Ad vector possessing CMV promoter-driven Cre recombinase expression cassette with miR-142-3p target sequences resulted in a further 24-fold reduction in the hepatic transgene expression by the Ad vector containing miR-122a target sequences and loxP sites, compared with coadministration of control Ad vector. On the other hand, there was no significant reduction of transgene expression in the spleen.

A20 controls macrophage to elicit potent cytotoxic CD4(+) T cell response

Emerging evidence indicates that CD4(+) T cells possess cytotoxic potential for tumor eradication and perforin/granzyme-mediated cytotoxicity functions as one of the important mechanisms for CD4(+) T cell-triggered cell killing. However, the critical issue is how the cytotoxic CD4(+) T cells are developed. During the course of our work that aims at promoting immunostimulation of APCs by inhibition of negative regulators, we found that A20-silenced Mф drastically induced granzyme B expression in CD4(+) T cells. As a consequence, the granzyme-highly expressing CD4(+) T cells exhibited a strong cytotoxic activity that restricted tumor development. We found that A20-silenced Mф activated cytotoxic CD4(+) T cells by MHC class-II restricted mechanism and the activation was largely dependent on enhanced production of IFN-γ.

Human dendritic cells expressing hepatitis C virus core protein display transcriptional and functional changes consistent with maturation

Hepatitis C virus (HCV) causes a chronic liver infection, which may result in cirrhosis and hepatocellular carcinoma. Impairment of the maturation process in dendritic cells (DCs) may be one of the mechanisms responsible for immune evasion of HCV. The core and NS3 proteins are among the most conserved HCV proteins and play a key role in viral clearance. To evaluate the effects of these proteins on DCs, monocyte-derived immature DCs (iDCs) were transfected with in vitro transcribed (IVT) HCV core or NS3 RNA and treated with maturation factors. Neither core nor NS3 had an inhibitory effect on DC maturation; however, transfection of iDCs with IVT core RNA appeared to result in changes compatible with maturation. To investigate this in more detail, the transcriptional profiles of iDCs transfected with IVT core, NS3 or green fluorescent protein (GFP) RNA were examined using a DC-specific membrane array. Of the 288 genes on the array, 46 genes were distinctively up- or down-regulated by transfection with IVT core RNA in comparison with NS3 or GFP RNA treatments. Forty-two of these genes are involved in DC maturation. The effects of core on maturation of iDCs were confirmed with a significant increase in surface expression of CD83 and HLA-DR, a reduction of phagocytosis, as well as an increase in proliferation and IFN-γ secretion by T cells in a mixed lymphocyte reaction assay. These results show that HCV core does not have an inhibitory effect on human DC maturation, but could be a target for the immune system.

A novel alphavirus replicon-vectored vaccine delivered by adenovirus induces sterile immunity against classical swine fever

Low efficacy of gene-based vaccines due to inefficient gene delivery and expression has been major bottleneck of their applications. Efforts have been made to improve the efficacy, such as gene gun and electroporation, but the strategies are difficult to put into practical use. In this study, we developed and evaluated an adenovirus-delivered, alphavirus replicon-vectored vaccine (chimeric vector-based vaccine) expressing the E2 gene of classical swine fever virus (CSFV) (rAdV-SFV-E2). Rabbits immunized with rAdV-SFV-E2 developed CSFV-specific antibodies as early as 9 days and as long as 189 days and completely protected from challenge with C-strain. Pigs immunized with rAdV-SFV-E2 (n=5) developed robust humoral and cell-mediated responses to CSFV and were completely protected from subsequent lethal CSFV infection clinically and virologically. The level of immunity and protection induced by rAdV-SFV-E2 was comparable to that provided by the currently used live attenuated vaccine, C-strain. In contrast, both the conventional alphavirus replicon-vectored vaccine pSFV1CS-E2 and conventional adenovirus-vectored vaccine rAdV-E2 provided incomplete protection. The chimeric vector-based vaccine represents the first gene-based vaccine that is able to confer sterile immunity and complete protection against CSFV. The new-concept vaccination strategy may also be valuable in vaccine development against other pathogens.

Chitosan is a surprising negative modulator of cytotoxic CD8+ T cell responses elicited by adenovirus cancer vaccines

Adjuvants modulate protective CD8(+) T cell responses generated by cancer vaccines. We have previously shown that immunostimulatory cytosine-phosphodiester-guanine (CpG) oligodeoxynucleotide (ODN) significantly augments tumor protection in mice given adenovirus cancer vaccines. Here, we examined the impact of chitosan, another candidate vaccine adjuvant, on protection conferred by adenovirus cancer vaccines. Unexpectedly, immunization of mice with adenovirus cancer vaccines in combination with chitosan provided little protection against tumor challenge. This directly correlated with the reduced detection of Ag-specific CD8(+) T cells, interferon-γ (IFN-γ) production, and cytotoxic T cell activity. We ruled out immunosuppressive regulatory T cells since the frequency did not change regardless of whether chitosan was delivered. In mammalian cell lines, chitosan did not interfere with adenovirus transgene expression. However, infection of primary murine bone marrow-derived dendritic cells with adenovirus complexed with chitosan significantly reduced viability, transgene expression, and upregulation of major histocompatability (MHC) class I and CD86. Our in vitro observations indicate that chitosan dramatically inhibits adenovirus-mediated transgene expression and antigen presenting cell activation, which could prevent CD8(+) T cell activation from occurring in vivo. These surprising data demonstrate for the first time that chitosan vaccine formulations can negatively impact the induction of CD8(+) T cell responses via its effect on dendritic cells, which is clinically important since consideration of chitosan as an adjuvant for vaccine formulations is growing.

Differential immune responses mediated by adenovirus- and lentivirus-transduced DCs in a HER-2/neu overexpressing tumor model

Recent investigations have demonstrated that adenoviral and lentiviral vectors encoding HER-2 can be utilized in cancer immunotherapy. However, it is not known whether both viral systems elicit a similar immune response. Here, we compare the immune response in mice induced by dendritic cells (DCs) infected with either recombinant adenovirus or lentivirus encoding rat HER-2 (rHER-2). Both vaccine types yielded similar control of tumor growth, but we found clear differences in their immune responses 10 days after DC immunization. Adenovirus rHER-2-transduced DCs elicited locally and systemically high frequencies of CD4+ and CD8+ T cells, while lentivirus rHER-2-transduced DCs predominantly led to CD4+ T-cell infiltration at the tumor site. Splenocytes from mice immunized with lentivirus rHER-2-transduced DCs secreted higher levels of interferon (IFN)-γ, mainly by CD4+ T cells, following stimulation by RM-1-mHER-2 tumors. In contrast, the adenovirus vaccinated group exhibited CD4+ and CD8+ T cells that both contributed to IFN-γ production. Besides an established cellular immune response, the rHER-2/DC vaccine elicited a significant humoral response that was highest in the adenovirus group. DC subsets and regulatory T cells in the spleen were also differentially modulated in the two vaccine systems. Finally, adoptive transfer of splenocytes from both groups of immunized mice strongly inhibited in vivo tumor growth. Our results suggest that not only the target antigen but also the virus system may determine the nature and magnitude of antitumor immunity by DC vaccination.

Implications of the innate immune response to adenovirus and adenoviral vectors

Adenovirus (AdV) is a common cause of respiratory illness in both children and adults. Respiratory symptoms can range from those of the common cold to severe pneumonia. Infection can also cause significant disease in the immunocompromised and among immunocompetent subjects in close quarters. Fortunately, infection with AdV in the normal host is generally mild. This is one reason why its initial use as a gene-therapy vector appeared to be so promising. Unfortunately, both innate and adaptive responses to the virus have limited the development of AdV vectors as a tool of gene therapy by increasing toxicity and limiting duration of transgene expression. This article will focus on the innate immune response to infection with wild-type AdV and exposure to AdV gene-therapy vectors. As much of the known information relates to the pulmonary inflammatory response, this organ system will be emphasized. This article will also discuss how that understanding has led to the creation of new vectors for use in gene therapy.

An Ad5[E1-, E2b-]-HER2/neu vector induces immune responses and inhibits HER2/neu expressing tumor progression in Ad5 immune mice

Immunotherapy is a promising approach for the treatment of cancers. Modified adenovirus 5 (Ad5) vectors have been used as a platform to deliver genes encoding tumor associated antigens (TAA). A major obstacle to Ad5 vector immunotherapy has been the induction of vector immunity following administration or the presence of pre-existing Ad5 immunity, which results in vector mitigation. It has been reported by us that the Ad5[E1-, E2b-] platform with unique deletions in the E1, E2b and E3 regions can induce potent cell mediated immunity (CMI) against delivered transgene products in the presence of pre-existing Ad5 immunity. Here we report the use of an Ad5[E1-, E2b-] vector platform expressing the TAA HER2/neu as a breast cancer immunotherapeutic agent. Ad5[E1-, E2b-]-HER2/neu induced potent CMI against HER2/neu in Ad5 naïve and Ad5 immune mice. Humoral responses were also induced and antibodies could lyse HER2/neu expressing tumor cells in the presence of complement in vitro. Ad5[E1-, E2b-]-HER2/neu prevented establishment of HER2/neu-expressing tumors and significantly inhibited progression of established tumors in Ad5 naïve and Ad5 immune murine models. These data demonstrate that in vivo delivery of Ad5[E1-, E2b-]-HER2/neu can induce anti-TAA immunity and inhibit progression of HER2/neu expressing cancers.

Production of adenovirus vectors and their use as a delivery system for influenza vaccines

IMPORTANCE OF THE FIELD

With the emergence of highly pathogenic avian influenza H5N1 viruses that have crossed species barriers and are responsible for lethal infections in humans in many countries, there is an urgent need for the development of effective vaccines which can be produced in large quantities at a short notice and confer broad protection against these H5N1 variants. In order to meet the potential global vaccine demand in a pandemic scenario, new vaccine-production strategies must be explored in addition to the currently used egg-based technology for seasonal influenza.

AREAS COVERED IN THIS REVIEW

Adenovirus (Ad) based influenza vaccines represent an attractive alternative/supplement to the currently licensed egg-based influenza vaccines. Ad-based vaccines are relatively inexpensive to manufacture, and their production process does not require either chicken eggs or labor-intensive and time-consuming processes necessitating enhanced biosafety facilities. Most importantly, in a pandemic situation, this vaccine strategy could offer a stockpiling option to reduce the response time before a strain-matched vaccine could be developed.

WHAT THE READER WILL GAIN

This review discusses Ad-vector technology and the current progress in the development of Ad-based influenza vaccines.

TAKE HOME MESSAGE

Ad vector-based influenza vaccines for pandemic preparedness are under development to meet global vaccine demand.

Induction of pathogenic cytotoxic T lymphocyte tolerance by dendritic cells: a novel therapeutic target

IMPORTANCE OF THE FIELD

Dendritic cells (DCs) have an important role, both direct and indirect, in controlling the expansion and function of T cells. Of the different subsets of T cells, cytotoxic T lymphocytes (CTLs/CD8(+) T cells) have been implicated in the pathogenesis and development of many diseases, including various forms of autoimmunity and transplant rejection. It may therefore be of therapeutic benefit to control the function of CTL in order to modulate disease processes and to ameliorate disease symptoms. Currently, pharmacological approaches have been employed to either directly or indirectly modulate the function of T cells. However, these treatment strategies have many limitations. Many experimental data have suggested that it is possible to alter CTL activity through manipulation of DC.

AREAS COVERED IN THIS REVIEW

Novel strategies that condition DCs to influence disease outcome through manipulation of CTL activity, both directly and indirectly. This includes the modulation of co-stimulation, negative co-stimulation, as well as manipulation of the cytokine milieu during CTL generation. Furthermore, DCs may also impact CTL activity through effects on effector and regulatory cells, along with manipulation of bioenergetic regulation, apoptotic-cell mediated tolerance and through the generation of exosomes. The implications of related interventions in the clinical arena are in turn considered.

WHAT THE READER WILL GAIN

Insight into such indirect methods of controlling CTL activity allows for an understanding of how disease-specific T cells may be regulated, while also sparing other aspects of adaptive immunity for normal physiological function. Such an approach towards the treatment of disease represents an innovative therapeutic target in the clinical arena.

TAKE HOME MESSAGE

There are numerous innovative methods for using DCs to control CTL responses. Manipulation of this interaction is thus an attractive avenue for the treatment of disease, particularly those of immune dysregulation, such as seen in autoimmunity and transplantation. With the number of studies moving into clinical stages constantly increasing, further advances and successes in this area are inevitable.

Protective immunity against a lethal respiratory Yersinia pestis challenge induced by V antigen or the F1 capsular antigen incorporated into adenovirus capsid

The aerosol form of the bacterium Yersinia pestis causes pneumonic plague, a rapidly fatal disease that is a biothreat if deliberately released. At present, no plague vaccines are available for use in the United States, but subunit vaccines based on the Y. pestis V antigen and F1 capsular protein show promise when administered with adjuvants. In the context that adenovirus (Ad) gene transfer vectors have a strong adjuvant potential related to the ability to directly infect dendritic cells, we hypothesized that modification of the Ad5 capsid to display either the Y. pestis V antigen or the F1 capsular antigen on the virion surface would elicit high V antigen- or F1-specific antibody titers, permit boosting with the same Ad serotype, and provide better protection against a lethal Y. pestis challenge than immunization with equivalent amounts of V or F1 recombinant protein plus conventional adjuvant. We constructed AdYFP-pIX/V and AdLacZ-pIX/F1, E1(-), E3(-) serotype 5 Ad gene transfer vectors containing a fusion of the sequence for either the Y. pestis V antigen or the F1 capsular antigen to the carboxy-terminal sequence of pIX, a capsid protein that can accommodate the entire V antigen (37 kDa) or F1 protein (15 kDa) without disturbing Ad function. Immunization with AdYFP-pIX/V followed by a single repeat administration of the same vector at the same dose resulted in significantly better protection of immunized animals compared with immunization with a molar equivalent amount of purified recombinant V antigen plus Alhydrogel adjuvant. Similarly, immunization with AdLacZ-pIX/F1 in a prime-boost regimen resulted in significantly enhanced protection of immunized animals compared with immunization with a molar-equivalent amount of purified recombinant F1 protein plus adjuvant. These observations demonstrate that Ad vaccine vectors containing pathogen-specific antigens fused to the pIX capsid protein have strong adjuvant properties and stimulate more robust protective immune responses than equivalent recombinant protein-based subunit vaccines administered with conventional adjuvant, suggesting that F1-and/or V-modified capsid Ad-based recombinant vaccines should be considered for development as anti-plague vaccines.

Therapeutic vaccination in chronic hepatitis B: preclinical studies in the woodchuck

Recommended treatment of chronic hepatitis B with interferon-α and/or nucleos(t)ide analogues does not lead to a satisfactory result. Induction of HBV-specific T cells by therapeutic vaccination or immunotherapies may be an innovative strategy to overcome virus persistence. Vaccination with commercially available HBV vaccines in patients did not result in effective control of HBV infection, suggesting that new formulations of therapeutic vaccines are needed. The woodchuck (Marmota monax) is a useful preclinical model for developing the new therapeutic approaches in chronic hepadnaviral infections. Several innovative approaches combining antiviral treatments with nucleos(t)ide analogues, DNA vaccines, and protein vaccines were tested in the woodchuck model. In this paper we summarize the available data concerning therapeutic immunization and gene therapy using recombinant viral vectors approaches in woodchucks, which show encouraging results. In addition, we present potential innovations in immunomodulatory strategies to be evaluated in this animal model.

Dendritic cells transduced to express interleukin 4 reduce diabetes onset in both normoglycemic and prediabetic nonobese diabetic mice

Background

We and others have previously demonstrated that treatment with bone marrow derived DC genetically modified to express IL-4 reduce disease pathology in mouse models of collagen-induced arthritis and delayed-type hypersensitivity. Moreover, treatment of normoglycemic NOD mice with bone marrow derived DC, genetically modified to express interleukin 4 (IL-4), reduces the onset of hyperglycemia in a significant number of animals. However, the mechanism(s) through which DC expressing IL-4 function to prevent autoimmune diabetes and whether this treatment can reverse disease in pre-diabetic NOD mice are unknown.

Methodology/Principal Findings

DC were generated from the bone marrow of NOD mice and transduced with adenoviral vectors encoding soluble murine IL-4 (DC/sIL-4), a membrane-bound IL-4 construct, or empty vector control. Female NOD mice were segregated into normoglycemic (<150mg/dL) and prediabetic groups (between 150 and 250 mg/dL) on the basis of blood glucose measurements, and randomized for adoptive transfer of 10⁶ DC via a single i.v. injection. A single injection of DC/sIL-4, when administered to normoglycemic 12-week old NOD mice, significantly reduced the number of mice that developed diabetes. Furthermore, DC/sIL-4, but not control DC, decreased the number of mice progressing to diabetes when given to prediabetic NOD mice 12–16 weeks of age. DC/sIL-4 treatment also significantly reduced islet mononuclear infiltration and increased the expression of FoxP3 in the pancreatic lymph nodes of a subset of treated animals. Furthermore, DC/sIL-4 treatment altered the antigen-specific Th2:Th1 cytokine profiles as determined by ELISPOT of splenocytes in treated animals.

Conclusions

Adoptive transfer of DC transduced to express IL-4 into both normoglycemic and prediabetic NOD mice is an effective treatment for T1D.

Antitumor effects of murine bone marrow-derived dendritic cells infected with xenogeneic livin alpha recombinant adenoviral vectors against Lewis lung carcinoma

Transduction with recombinant, replication-defective adenoviral (rAd) vectors encoding a transgene is an efficient method for gene transfer into dendritic cells (DCs). Livin is a member of the inhibitor of apoptosis protein family. Lung cancer and many other tumors express livin at high levels; whereas, normal fully differentiated cells generally do not. Therefore, livin represents a tumor-specific target for cancer vaccine therapy. Self proteins like livin may not stimulate potent antitumor immune responses due to central immunologic tolerance. Small variations in protein sequence that may exist between homologous proteins of different species can break tolerance to the native antigen. To study immunogenicity of a xenogeneic livin protein, we constructed an recombinant adenoviral vectors containing the human livin alpha genes (rAd-hlivin alpha) and vaccinated C57BL/6 mice with mouse bone marrow dendritic cells (BMDCs) transfected with rAd-hlivin alpha gave rise to potent livin-specific cytotoxic T lymphocyte (CTL) capable of lysing Lewis lung carcinoma (LLC) cells. Moreover, vaccination of mice with rAd-hlivin alpha-transduced DCs (rAd-hlivin alpha DCs) induced a potent protective and therapeutic anti-tumor immunity to LLC in a subcutaneous model along with prolonged survival compared to mice vaccinated with control recombinant adenovirus-transduced DCs(rAd-c DCs) or DCs alone. Therefore, xenogeneic differences between human and murine sequences might be exploited to develop immunogenic tumor vaccines.

Dendritic cells transduced with lentiviral vectors expressing VIP differentiate into VIP-secreting tolerogenic-like DCs

Dendritic cells (DCs) initiate immune responses as well as tolerance. We showed previously that the neuropeptide vasoactive intestinal peptide (VIP) suppresses innate immune responses, modulates adaptive responses by generating regulatory T cells (Treg) through the induction of tolerogenic DCs (tDCs), and has therapeutic effects in models of autoimmune/inflammatory disorders. Systemic VIP administration is limited by its short biological half-life and by its pleiotropic effects on the cardiovascular system and gastrointestinal tract. Therefore, we used lentiviral vectors to genetically engineer VIP-expressing bone marrow-derived DC (BMDC) and characterized the transduced LentiVIP-DC in terms of phenotype and therapeutic effects in models of experimental autoimmune encephalomyelitis (EAE) and cecal ligation and puncture (CLP) sepsis. LentiVIP-DCs secrete VIP, and resemble tDCs through lack of co-stimulatory molecule upregulation, lack of proinflammatory cytokine secretion, increased interleukin (IL)-10 production, and poor stimulation of allogeneic T cells. A single inoculation of LentiVIP-DC in EAE or CLP mice had therapeutic effects, which correlated with reduced expression of proinflammatory cytokines and increased IL-10 production in spinal cord and peritoneal fluid, respectively. In contrast to systemic VIP administration that requires repeated, high-dose inoculations, local delivery of VIP by LentiVIP-DC may represent a promising therapeutic tool for the treatment of autoimmune diseases and inflammatory disorders.

Recombinant murine cytomegalovirus vector activates human monocyte-derived dendritic cells in a NF-kappaB dependent pathway

To evaluate the potential use of recombinant murine cytomegalovirus (MCMV) as an antigen delivery vector, we examined the cytokine and CD80 and CD86 expression profiles of MCMV encoding either enhanced green fluorescent protein gene (MCMV-EGFP) or human immunodeficiency virus-1 glycoprotein gp120 gene (MCMV-gp120) infected monocyte-derived dendritic cells (Mo-DC) and investigated the role of nuclear factor kappa B (NF-kappaB) in Mo-DC activation. Results showed that MCMV triggered the induction of inflammatory cytokines and/or CD80 and CD86 up-regulation in Mo-DC. UV-inactivated MCMV exhibited a reduced production of inflammatory cytokines and a lowered expression of CD80 and CD86 compared with live MCMV infection. Treatment of cells with a NF-kappaB peptide inhibitor prior to MCMV infection reduced the induction of cytokines and CD80 and CD86 up-regulation. Overall, the results suggest that recombinant MCMV vectors activate human Mo-DC in a NF-kappaB dependent pathway. The abortive infection or de novo gene expression greatly enhances the activation of Mo-DC by MCMV vectors.

Targeting the porcine immune system--particulate vaccines in the 21st century

During the last decade, the propagation of immunological knowledge describing the critical role of dendritic cells (DC) in the induction of efficacious immune responses has promoted research and development of vaccines systematically targeting DC. Based on the promise for the rational design of vaccine platforms, the current review will provide an update on particle-based vaccines of both viral and synthetic origin, giving examples of recombinant virus carriers such as adenoviruses and biodegradable particulate carriers. The viral carriers carry pathogen-associated molecular patterns (PAMP), used by the original virus for targeting DC, and are particularly efficient and versatile gene delivery vectors. Efforts in the field of synthetic vaccine carriers are focussing on decorating the particle surface with ligands for DC receptors such as heparan sulphate glycosaminoglycan structures, integrins, Siglecs, galectins, C-type lectins and toll-like receptors. The emphasis of this review will be placed on targeting the porcine immune system, but reference will be made to advances with murine and human vaccine delivery systems where information on DC targeting is available.

The expression of exogenous genes in macrophages: obstacles and opportunities

Over the past three decades many techniques for expressing exogenous genes in a variety of cells and cell lines have been developed. Exogenous gene expression in macrophages has lagged behind that of other nonhematopioetic cells. There are many reasons for this, but most are due to technical difficulties associated with transfecting macrophages. As professional phagocytes, macrophages are endowed with many potent degradative enzymes that can disrupt nucleic acid integrity and make gene transfer into these cells an inefficient process. This is especially true of activated macrophages which undergo a dramatic change in their physiology following exposure to immune or inflammatory stimuli. Viral transduction of these cells has been hampered because macrophages are end-stage cells that generally do not divide; therefore, some of the vectors that depend on integration into a replicative genome have met with limited success. Furthermore, macrophages are quite responsive to "danger signals," and therefore several of the original viral vectors that were used for gene transfer induced potent anti-viral responses in these cells making these vectors inappropriate for gene delivery. Many of these difficulties have been largely overcome, and relatively high efficiency gene expression in primary human or murine macrophages is becoming more routine. In the present chapter we discuss some of the gene expression techniques that have met with success and review the advantages and disadvantages of each.

Use of adenovirus in vaccines for HIV

The best hope of controlling the HIV pandemic is the development of an effective vaccine. In addition to the stimulation of virus neutralising antibodies, a vaccine will need an effective T-cell response against the virus. Vaccines based on recombinant adenoviruses (rAd) are promising candidates to stimulate anti-HIV T-cell responses. This review discusses the different rAd vector types, problems raised by host immune responses against them and strategies that are being adopted to overcome this problem. Vaccines need to target and stimulate dendritic cells and thus the tropism and interaction of rAd-based vaccines with these cells is covered. Different rAd vaccination regimes and the need to stimulate mucosal responses are discussed together with data from animal studies on immunogenicity and virus challenge experiments. The review ends with a discussion of the recent disappointing Merck HIV vaccine trial.