Adenovirus type-35 vectors block human CD4+ T-cell activation via CD46 ligation

Biosafety Evaluation of a Chimeric Adenoviral Vector in Mini-Pigs: Insights into Immune Tolerance and Gene Therapy Potential

BACKGROUND

The biosafety of gene therapy products remains a major challenge to their introduction into the clinic. In particular, the problem of immunogenicity of viral vectors is the focus of attention. Large animals such as pigs, whose anatomical and physiological characteristics are similar to those of humans, have an advantage in testing vector systems.

METHODS

We performed a comprehensive in vitro and in vivo study to evaluate the biosafety of a chimeric adenoviral vector carrying a green fluorescent protein gene (Ad5/35F-GFP) in a mini-pig model.

RESULTS

Transcriptome and secretome analyses of mini-pig leucocytes transduced with Ad5/35F-GFP revealed changes restraining pro-inflammatory processes and cytokine production. No adverse effects were revealed through the clinical, instrumental, laboratory, and histological examinations conducted within a week after the direct or autologous leucocyte-mediated administration of Ad5/35F-GFP to mini-pigs. The decrease in cytokine levels in the blood of experimental animals is also consistent with the in vitro data and confirms the immune tolerance of mini-pigs to Ad5/35F-GFP.

CONCLUSIONS

Here, we show the safety of Ad5/35F in a mini-pig model and provide evidence that Ad5/35F is a promising vector for gene therapy. These results advance our understanding of vector-host interactions and offer a solid foundation for the clinical application of this vector.

The Immune System-A Double-Edged Sword for Adenovirus-Based Therapies

Pathogenic adenovirus (Ad) infections are widespread but typically mild and transient, except in the immunocompromised. As vectors for gene therapy, vaccine, and oncology applications, Ad-based platforms offer advantages, including ease of genetic manipulation, scale of production, and well-established safety profiles, making them attractive tools for therapeutic development. However, the immune system often poses a significant challenge that must be overcome for adenovirus-based therapies to be truly efficacious. Both pre-existing anti-Ad immunity in the population as well as the rapid development of an immune response against engineered adenoviral vectors can have detrimental effects on the downstream impact of an adenovirus-based therapeutic. This review focuses on the different challenges posed, including pre-existing natural immunity and anti-vector immunity induced by a therapeutic, in the context of innate and adaptive immune responses. We summarise different approaches developed with the aim of tackling these problems, as well as their outcomes and potential future applications.

Construction and application of adenoviral vectors

Adenoviral vectors have been widely used as vaccine candidates or potential vaccine candidates against infectious diseases due to the convenience of genome manipulation, their ability to accommodate large exogenous gene fragments, easy access of obtaining high-titer of virus, and high efficiency of transduction. At the same time, adenoviral vectors have also been used extensively in clinical research for cancer gene therapy and treatment of diseases caused by a single gene defect. However, application of adenovirus also faces a series of challenges such as poor targeting, strong immune response against the vector itself, and they cannot be used repeatedly. It is believed that these problems will be solved gradually with further research and technological development in related fields. Here, we review the construction methods of adenoviral vectors, including "gutless" adenovirus and discuss application of adenoviral vectors as prophylactic vaccines for infectious pathogens and their application prospects as therapeutic vaccines for cancer and other kinds of chronic infectious disease such as human papillomavirus, hepatitis B virus, and hepatitis C virus.

Molecular and cellular changes in the post-traumatic spinal cord remodeling after autoinfusion of a genetically-enriched leucoconcentrate in a mini-pig model

Post-traumatic spinal cord remodeling includes both degenerating and regenerating processes, which affect the potency of the functional recovery after spinal cord injury (SCI). Gene therapy for spinal cord injury is proposed as a promising therapeutic strategy to induce positive changes in remodeling of the affected neural tissue. In our previous studies for delivering the therapeutic genes at the site of spinal cord injury, we developed a new approach using an autologous leucoconcentrate transduced ex vivo with chimeric adenoviruses (Ad5/35) carrying recombinant cDNA. In the present study, the efficacy of the intravenous infusion of an autologous genetically-enriched leucoconcentrate simultaneously producing recombinant vascular endothelial growth factor (VEGF), glial cell line-derived neurotrophic factor (GDNF), and neural cell adhesion molecule (NCAM) was evaluated with regard to the molecular and cellular changes in remodeling of the spinal cord tissue at the site of damage in a model of mini-pigs with moderate spinal cord injury. Experimental animals were randomly divided into two groups of 4 pigs each: the therapeutic (infused with the leucoconcentrate simultaneously transduced with a combination of the three chimeric adenoviral vectors Ad5/35-VEGF165, Ad5/35-GDNF, and Ad5/35-NCAM1) and control groups (infused with intact leucoconcentrate). The morphometric and immunofluorescence analysis of the spinal cord regeneration in the rostral and caudal segments according to the epicenter of the injury in the treated animals compared to the control mini-pigs showed: (1) higher sparing of the grey matter and increased survivability of the spinal cord cells (lower number of Caspase-3-positive cells and decreased expression of Hsp27); (2) recovery of synaptophysin expression; (3) prevention of astrogliosis (lower area of glial fibrillary acidic protein-positive astrocytes and ionized calcium binding adaptor molecule 1-positive microglial cells); (4) higher growth rates of regenerating βIII-tubulin-positive axons accompanied by a higher number of oligodendrocyte transcription factor 2-positive oligodendroglial cells in the lateral corticospinal tract region. These results revealed the efficacy of intravenous infusion of the autologous genetically-enriched leucoconcentrate producing recombinant VEGF, GDNF, and NCAM in the acute phase of spinal cord injury on the positive changes in the post-traumatic remodeling nervous tissue at the site of direct injury. Our data provide a solid platform for a new ex vivo gene therapy for spinal cord injury and will facilitate further translation of regenerative therapies in clinical neurology.

Induction of Angiogenesis by Genetically Modified Human Umbilical Cord Blood Mononuclear Cells

Stimulating the process of angiogenesis in treating ischemia-related diseases is an urgent task for modern medicine, which can be achieved through the use of different cell types. Umbilical cord blood (UCB) continues to be one of the attractive cell sources for transplantation. The goal of this study was to investigate the role and therapeutic potential of gene-engineered umbilical cord blood mononuclear cells (UCB-MC) as a forward-looking strategy for the activation of angiogenesis. Adenovirus constructs Ad-VEGF, Ad-FGF2, Ad-SDF1α, and Ad-EGFP were synthesized and used for cell modification. UCB-MCs were isolated from UCB and transduced with adenoviral vectors. As part of our in vitro experiments, we evaluated the efficiency of transfection, the expression of recombinant genes, and the secretome profile. Later, we applied an in vivo Matrigel plug assay to assess engineered UCB-MC's angiogenic potential. We conclude that hUCB-MCs can be efficiently modified simultaneously with several adenoviral vectors. Modified UCB-MCs overexpress recombinant genes and proteins. Genetic modification of cells with recombinant adenoviruses does not affect the profile of secreted pro- and anti-inflammatory cytokines, chemokines, and growth factors, except for an increase in the synthesis of recombinant proteins. hUCB-MCs genetically modified with therapeutic genes induced the formation of new vessels. An increase in the expression of endothelial cells marker (CD31) was revealed, which correlated with the data of visual examination and histological analysis. The present study demonstrates that gene-engineered UCB-MC can be used to stimulate angiogenesis and possibly treat cardiovascular disease and diabetic cardiomyopathy.

Autologous Genetically Enriched Leucoconcentrate in the Preventive and Acute Phases of Stroke Treatment in a Mini-Pig Model

The natural limitations of regeneration in the CNS are major problems for the treatment of neurological disorders, including ischaemic brain strokes. Among the approaches being actively developed to inhibit post-ischaemic negative consequences is the delivery of therapeutic genes encoding neuroprotective molecules to the brain. Unfortunately, there are currently no proven and available medicines that contain recombinant human genes for the treatment of ischaemic cerebral stroke. Of particular interest is the development of treatments for patients at risk of ischaemic stroke. In the present study, we propose a proof of concept for the use of an autologous, genetically enriched leucoconcentrate temporally secreting recombinant vascular endothelial growth factor (VEGF), glial-cell-line-derived neurotrophic factor (GDNF) and the neural cell adhesion molecule (NCAM) for the treatment of stroke. In a mini-pig ischaemic stroke model, genetically enriched leucoconcentrate was infused 4 h after surgery (gene therapy in acute phase) or 2 days before stroke modelling (preventive gene therapy). On day 21, after the stroke modelling, the post-ischaemic brain recovery was examined by morphologic and immunofluorescence analysis. The benefits of treating a stroke with genetically enriched leucoconcentrate both for preventive purposes and in the acute phase were confirmed by an improved performance in behavioural tests, higher preservation of brain tissue and positive post-ischaemic brain remodelling in the peri-infarct area. These results suggest that the employment of autologous leucocytes enabling the temporary production of the recombinant therapeutic molecules to correct the pathological process in the CNS may be one of the breakthrough approaches in gene therapy.

New Therapy for Spinal Cord Injury: Autologous Genetically-Enriched Leucoconcentrate Integrated with Epidural Electrical Stimulation

The contemporary strategy for spinal cord injury (SCI) therapy aims to combine multiple approaches to control pathogenic mechanisms of neurodegeneration and stimulate neuroregeneration. In this study, a novel regenerative approach using an autologous leucoconcentrate enriched with transgenes encoding vascular endothelial growth factor (VEGF), glial cell line-derived neurotrophic factor (GDNF), and neural cell adhesion molecule (NCAM) combined with supra- and sub-lesional epidural electrical stimulation (EES) was tested on mini-pigs similar in morpho-physiological scale to humans. The complex analysis of the spinal cord recovery after a moderate contusion injury in treated mini-pigs compared to control animals revealed: better performance in behavioural and joint kinematics, restoration of electromyography characteristics, and improvement in selected immunohistology features related to cell survivability, synaptic protein expression, and glial reorganization above and below the injury. These results for the first time demonstrate the positive effect of intravenous infusion of autologous genetically-enriched leucoconcentrate producing recombinant molecules stimulating neuroregeneration combined with neuromodulation by translesional multisite EES on the restoration of the post-traumatic spinal cord in mini-pigs and suggest the high translational potential of this novel regenerative therapy for SCI patients.

Gene-modified leucoconcentrate for personalized ex vivo gene therapy in a mini pig model of moderate spinal cord injury

We previously demonstrated that gene-modified umbilical cord blood mononuclear cells overexpressing a combination of recombinant neurotrophic factors are a promising therapeutic approach for cell-mediated gene therapy for neurodegenerative diseases, neurotrauma, and stroke. In this study, using a mini pig model of spinal cord injury, we proposed for the first time the use of gene-modified leucoconcentrate prepared from peripheral blood in the plastic blood bag for personalized ex vivo gene therapy. Leucoconcentrate obtained from mini pig peripheral blood was transduced with a chimeric adenoviral vector (Ad5/35F) that carried an enhanced green fluorescent protein (EGFP) reporter gene in the plastic blood bag. The day after blood donation, the mini pigs were subjected to moderate SCI and four hours post-surgery they were intravenously autoinfused with gene-modified leucoconcentrate. A week after gene-modified leucoconcentrate therapy, fluorescent microscopy revealed EGFP-expressing leucocytes in spinal cord at the site of contusion injury. In the spleen the groups of EGFP-positive cells located in the lymphoid follicles were observed. In vitro flow cytometry and fluorescent microscopy studies of the gene-modified leucoconcentrate samples also confirmed the production of EGFP by leucocytes. Thus, the efficacy of leucocytes transduction in the plastic blood bag and their migratory potential suggest their use for temporary production of recombinant biologically active molecules to correct certain pathological conditions. This paper presents a proof-of-concept of simple, safe and effective approach for personalized ex vivo gene therapy based on gene-modified leucoconcentrate autoinfusion. The animal protocols were approved by the Kazan State Medical University Animal Care and Use Committee (approval No. 5) on May 27, 2014.

Adenovirus vectors in hematopoietic stem cell genome editing

Genome editing of hematopoietic stem cells (HSCs) represents a therapeutic option for a number of hematological genetic diseases, as HSCs have the potential for self-renewal and differentiation into all blood cell lineages. This review presents advances of genome editing in HSCs utilizing adenovirus vectors as delivery vehicles. We focus on capsid-modified, helper-dependent adenovirus vectors that are devoid of all viral genes and therefore exhibit an improved safety profile. We discuss HSC genome engineering for several inherited disorders and infectious diseases including hemoglobinopathies, Fanconi anemia, hemophilia, and HIV-1 infection by ex vivo and in vivo editing in transgenic mice, nonhuman primates, as well as in human CD34+ cells. Mechanisms of therapeutic gene transfer including episomal expression of designer nucleases and base editors, transposase-mediated random integration, and targeted homology-directed repair triggered integration into selected genomic safe harbor loci are also reviewed.

In vivo hematopoietic stem cell gene therapy ameliorates murine thalassemia intermedia

Current thalassemia gene therapy protocols require the collection of hematopoietic stem/progenitor cells (HSPCs), in vitro culture, lentivirus vector transduction, and retransplantation into myeloablated patients. Because of cost and technical complexity, it is unlikely that such protocols will be applicable in developing countries, where the greatest demand for a β-thalassemia therapy lies. We have developed a simple in vivo HSPC gene therapy approach that involves HSPC mobilization and an intravenous injection of integrating HDAd5/35++ vectors. Transduced HSPCs homed back to the bone marrow, where they persisted long-term. HDAd5/35++ vectors for in vivo gene therapy of thalassemia had a unique capsid that targeted primitive HSPCs through human CD46, a relatively safe SB100X transposase-based integration machinery, a micro-LCR-driven γ-globin gene, and an MGMT(P140K) system that allowed for increasing the therapeutic effect by short-term treatment with low-dose O6-benzylguanine plus bis-chloroethylnitrosourea. We showed in "healthy" human CD46-transgenic mice and in a mouse model of thalassemia intermedia that our in vivo approach resulted in stable γ-globin expression in the majority of circulating red blood cells. The high marking frequency was maintained in secondary recipients. In the thalassemia model, a near-complete phenotypic correction was achieved. The treatment was well tolerated. This cost-efficient and "portable" approach could permit a broader clinical application of thalassemia gene therapy.

Designer Oncolytic Adenovirus: Coming of Age

The licensing of talimogene laherparepvec (T-Vec) represented a landmark moment for oncolytic virotherapy, since it provided unequivocal evidence for the long-touted potential of genetically modified replicating viruses as anti-cancer agents. Whilst T-Vec is promising as a locally delivered virotherapy, especially in combination with immune-checkpoint inhibitors, the quest continues for a virus capable of specific tumour cell killing via systemic administration. One candidate is oncolytic adenovirus (Ad); it’s double stranded DNA genome is easily manipulated and a wide range of strategies and technologies have been employed to empower the vector with improved pharmacokinetics and tumour targeting ability. As well characterised clinical and experimental agents, we have detailed knowledge of adenoviruses’ mechanisms of pathogenicity, supported by detailed virological studies and in vivo interactions. In this review we highlight the strides made in the engineering of bespoke adenoviral vectors to specifically infect, replicate within, and destroy tumour cells. We discuss how mutations in genes regulating adenoviral replication after cell entry can be used to restrict replication to the tumour, and summarise how detailed knowledge of viral capsid interactions enable rational modification to eliminate native tropisms, and simultaneously promote active uptake by cancerous tissues. We argue that these designer-viruses, exploiting the viruses natural mechanisms and regulated at every level of replication, represent the ideal platforms for local overexpression of therapeutic transgenes such as immunomodulatory agents. Where T-Vec has paved the way, Ad-based vectors now follow. The era of designer oncolytic virotherapies looks decidedly as though it will soon become a reality.

Chimpanzee adenoviral vectors as vaccines - challenges to move the technology into the fast lane

INTRODUCTION

In recent years, replication-defective chimpanzee-derived adenoviruses have been extensively evaluated as genetic vaccines. These vectors share desirable properties with human adenoviruses like the broad tissue tropism and the ease of large-scale manufacturing. Additionally, chimpanzee adenoviruses have the advantage to overcome the negative impact of pre-existing anti-human adenovirus immunity. Areas covered: Here the authors review current pre-clinical research and clinical trials that utilize chimpanzee-derived adenoviral vectors as vaccines. A wealth of studies are ongoing to evaluate different vector backbones and administration routes with the aim of improving immune responses. The challenges associated with the identification of an optimal chimpanzee vector and immunization strategies for different immunological outcomes will be discussed. Expert commentary: The demonstration that chimpanzee adenoviruses can be safely used in humans has paved the way to the use of a whole new array of vectors of different serotypes. However, so far no predictive signature of vector immunity in humans has been identified. The high magnitude of T cell responses elicited by chimpanzee adenoviruses has allowed dissecting the qualitative aspects that may be important for protective immunity. Ultimately, only the results from the most clinically advanced products will help establish the efficacy of the vaccine vector platform in the field of disease prevention.

Clinical features of community acquired adenovirus pneumonia during the 2011 community outbreak in Southern Taiwan: role of host immune response

Background

Human adenovirus 7 (HAdV-7) was responsible for a significant number of fatalities during the 2011 community outbreak in Taiwan. The mechanisms underlying the pathogenesis of severe adenovirus infections in non-immunocompromised individuals remain unclear. Adenovirus pneumonia was associated with pleural effusion in a number of patients from the 2011 outbreak suggesting that similar to bacterial pneumonia, patients diagnosed with adenovirus pneumonia who have pleural effusion are more severely and systemically infected, and may have a more protracted disease course. We hypothesized that the host immunological response determines the severity of adenoviral infection.

Methods

This retrospective case series study included patients diagnosed with severe lower respiratory tract infections at the National Cheng Kung University Hospital in southern Taiwan between December 2010 and October 2011. The main inclusion criteria were 1) presence of multifocal patchy infiltrates, lobar consolidation or reticular interstitial opacities in chest X-rays, and 2) presence of adenovirus isolated from respiratory specimens. All patients had adenovirus isolated from respiratory specimens, and were negative for other viruses. Pleural effusion was confirmed in all patients using chest echography. Clinical features and laboratory data were compared in patients with (n = 12) and without (n = 15) parapneumonic effusion.

Results

Presence of parapneumonic effusion was significantly associated with a longer febrile duration, more complicated clinical management, and a greater risk of extrapulmonary involvement, notably hepatitis. Patients without pleural effusion had significantly higher numbers of WBCs, platelets, and absolute segment cell counts (ASCs) compared to patients with pleural effusion (all p < 0.05). Patients without pleural effusion had significantly higher counts of CD4+, CD8+, and CD20+ T cells (all p < 0.05) compared to patients with pleural effusion.

Conclusion

Our data indicated that presence of parapneumonic effusion in adenoviral pneumonia was associated with longer febrile duration, more complicated clinical management, a greater risk of hepatitis, and suppression of host cellular immunity. Further prospective, large-scale studies are needed to validate our results.

Recombinant Ad35 adenoviral proteins as potent modulators of human T cell activation

The protein CD46 protects cells from complement attack by regulating cleavage of C3b and C3d. CD46 also regulates the adaptive immune response by controlling T cell activation and differentiation. Co-engagement of the T cell receptor and CD46 notably drives T cell differentiation by switching production of IFNγ to secretion of anti-inflammatory IL-10. This regulatory pathway is altered in several chronic inflammatory diseases highlighting its key role for immune homeostasis. The manipulation of the CD46 pathway may therefore provide a powerful means to regulate immune responses. Herein, we investigated the effect of recombinant proteins derived from the fiber knob of the adenovirus serotype 35 (Ad35) that uses CD46 as its entry receptor, on human T cell activation. We compared the effects of Ad35K++, engineered to exhibit enhanced affinity to CD46, and of Ad35K-, mutated in the binding site for CD46. Ad35K++ profoundly affects T cell activation by decreasing the levels of CD46 at the surface of primary T cells, and impairing T cell co-activation, shown by decreased CD25 expression, reduced proliferation and lower secretion of IL-10 and IFNγ. In contrast, Ad35K- acts a potent coactivator of T cells, enhancing T cell proliferation and cytokine production. These data show that recombinant Ad35 proteins are potent modulators of human T cell activation, and support their further development as potential drugs targeting T cell responses. This article is protected by copyright. All rights reserved.

Adenovirus serotype 26 and 35 vectors induce simian immunodeficiency virus-specific T lymphocyte responses in foreskin in rhesus monkeys

Foreskin is the principal site of heterosexual HIV-1 infection in men. However, little is known about HIV-1-specific immune responses or inflammation in foreskin. To the best of our knowledge, no previous studies have assessed immune responses to candidate HIV-1 vaccines in foreskin. Using the rhesus monkey model, we show that intramuscular immunization with adenovirus serotype 26 and 35 vectors expressing SIV antigens elicited durable SIV Gag-specific CD4(+) and CD8(+) T cell responses in foreskin that were detectable for more than 1 year following vaccination. Gag-specific CD4(+) and CD8(+) T cells were also detectable in foreskin of SIV- and SHIV-infected animals and were at least comparable in magnitude to those in peripheral blood. However, unlike peripheral blood T cells, the majority of foreskin T cells exhibited transitional memory or effector memory phenotype and expressed higher levels of the activation markers CD69, HLA-DR, and CCR5, although vaccination did not further enhance foreskin CD4(+) T cell activation. These findings suggest that systemic vaccination strategies can elicit potentially important SIV-specific cellular immunity in foreskin. Further characterization of vaccine-elicited immune responses and inflammation in foreskin is warranted.

IMPORTANCE

We demonstrate here the induction of SIV-specific cellular immune responses in foreskin by adenovirus serotype 26 and 35 vaccine vectors. Foreskin T cells were more activated than peripheral blood T cells, but foreskin T cells were not further activated by vaccination. These findings suggest that alternative serotype adenovirus vectors induce potentially important immune responses in foreskin.

Enhanced antitumor immunotherapeutic effect of B-cell-based vaccine transduced with modified adenoviral vector containing type 35 fiber structures

For successful clinical tumor immunotherapy outcomes, strong immune responses against tumor antigens must be generated. Cell-based vaccines compromise one strategy with which to induce appropriate strong immune responses. Previously, we established a natural killer T-cell (NKT) ligand-loaded, adenoviral vector-transduced B-cell-based anticancer cellular vaccine. To enhance tumor antigen delivery to B cells, we established a modified adenoviral vector (Ad-k35) that encoded a truncated form of the breast cancer antigen Her2/neu (Ad-k35HM) in which fiber structure was substituted with adenovirus serotype 35. We observed increased tumor antigen expression with Ad-k35HM in both human and murine B cells. In addition, an Ad-k35HM-transduced B-cell vaccine elicited strong antigen-specific cellular and humoral immune responses that were further enhanced with the additional loading of soluble NKT ligand KBC009. An Ad-k35HM-transduced, KBC009-loaded B-cell vaccine efficiently suppressed the in vivo growth of established tumors in a mouse model. Moreover, the vaccine elicited human leukocyte antigen (HLA)-A2 epitope-specific cytotoxic T-cell responses in B6.Cg (CB)-Tg (HLA-A/H2-D) 2Enge/Jat mice. These findings indicated that the Ad-k35 could be appropriate for the preclinical and clinical development of B-cell-based anticancer immunotherapies.

CD46: the 'multitasker' of complement proteins

Complement is undeniably quintessential for innate immunity by detecting and eliminating infectious microorganisms. Recent work, however, highlights an equally profound impact of complement on the induction and regulation of a wide range of immune cells. In particular, the complement regulator CD46 emerges as a key sensor of immune activation and a vital modulator of adaptive immunity. In this review, we summarize the current knowledge of CD46-mediated signalling events and their functional consequences on immune-competent cells with a specific focus on those in CD4(+) T cells. We will also discuss the promises and challenges that potential therapeutic modulation of CD46 may hold and pose.

The lack of maturation of Ebola virus-infected dendritic cells results from the cooperative effect of at least two viral domains

Ebola virus (EBOV) infections are characterized by deficient T lymphocyte responses, T lymphocyte apoptosis, and lymphopenia in the absence of direct infection of T lymphocytes. In contrast, dendritic cells (DC) are infected but fail to mature appropriately, thereby impairing the T cell response. We investigated the contributions of EBOV proteins in modulating DC maturation by generating recombinant viruses expressing enhanced green fluorescent protein and carrying mutations affecting several potentially immunomodulating domains. They included envelope glycoprotein (GP) domains, as well as innate response antagonist domains (IRADs) previously identified in the VP24 and VP35 proteins. GP expressed by an unrelated vector, but not the wild-type EBOV, was found to strongly induce DC maturation, and infections with recombinant EBOV carrying mutations disabling GP functional domains did not restore DC maturation. In contrast, each of the viruses carrying mutations disabling any IRAD in VP35 induced a dramatic upregulation of DC maturation markers. This was dependent on infection, but not interaction with GP. Disabling of IRADs also resulted in up to a several hundredfold increase in secretion of cytokines and chemokines. Furthermore, these mutations induced formation of homotypic DC clusters, which represent close correlates of their maturation and presumably facilitate transfer of antigen from migratory DC to lymph node DC. Thus, an individual IRAD is insufficient to suppress DC maturation; rather, the suppression of DC maturation and the "immune paralysis" observed during EBOV infections results from a cooperative effect of two or more individual IRADs.

Adenovirus serotype 5 vectors with Tat-PTD modified hexon and serotype 35 fiber show greatly enhanced transduction capacity of primary cell cultures

Recombinant adenovirus serotype 5 (Ad5) vectors represent one of the most efficient gene delivery vectors in life sciences. However, Ad5 is dependent on expression of the coxsackievirus-adenovirus-receptor (CAR) on the surface of target cell for efficient transduction, which limits it’s utility for certain cell types. Herein we present a new vector, Ad5PTDf35, which is an Ad5 vector having serotype 35 fiber-specificity and Tat-PTD hexon-modification. This vector shows dramatically increased transduction capacity of primary human cell cultures including T cells, monocytes, macrophages, dendritic cells, pancreatic islets and exocrine cells, mesenchymal stem cells and tumor initiating cells. Biodistribution in mice following systemic administration (tail-vein injection) show significantly reduced uptake in the liver and spleen of Ad5PTDf35 compared to unmodified Ad5. Therefore, replication-competent viruses with these modifications may be further developed as oncolytic agents for cancer therapy. User-friendly backbone plasmids containing these modifications were developed for compatibility to the AdEasy-system to facilitate the development of surface-modified adenoviruses for gene delivery to difficult-to-transduce cells in basic, pre-clinical and clinical research.

The CD46-Jagged1 interaction is critical for human TH1 immunity

CD46 is a complement regulator with important roles related to the immune response. CD46 functions as a pathogen receptor and is a potent costimulator for the induction of interferon-γ (IFN-γ)-secreting effector T helper type 1 (T(H)1) cells and their subsequent switch into interleukin 10 (IL-10)-producing regulatory T cells. Here we identified the Notch family member Jagged1 as a physiological ligand for CD46. Furthermore, we found that CD46 regulated the expression of Notch receptors and ligands during T cell activation and that disturbance of the CD46-Notch crosstalk impeded induction of IFN-γ and switching to IL-10. Notably, CD4(+) T cells from CD46-deficient patients and patients with hypomorphic mutations in the gene encoding Jagged1 (Alagille syndrome) failed to mount appropriate T(H)1 responses in vitro and in vivo, which suggested that CD46-Jagged1 crosstalk is responsible for the recurrent infections in subpopulations of these patients.

Transient removal of CD46 is safe and increases B-cell depletion by rituximab in CD46 transgenic mice and macaques

We have developed a technology that depletes the complement regulatory protein (CRP) CD46 from the cell surface, and thereby sensitizes tumor cells to complement-dependent cytotoxicity triggered by therapeutic monoclonal antibodies (mAbs). This technology is based on a small recombinant protein, Ad35K++, which induces the internalization and subsequent degradation of CD46. In preliminary studies, we had demonstrated the utility of the combination of Ad35K++ and several commercially available mAbs such as rituximab, alemtuzumab, and trastuzumab in enhancing cell killing in vitro as well as in vivo in murine xenograft and syngeneic tumor models. We have completed scaled manufacturing of Ad35K++ protein in Escherichia coli for studies in nonhuman primates (NHPs). In macaques, we first defined a dose of the CD20-targeting mAb rituximab that did not deplete CD20-positive peripheral blood cells. Using this dose of rituximab, we then demonstrated that pretreatment with Ad35K++ reconstituted near complete elimination of B cells. Further studies demonstrated that the treatment was well tolerated and safe. These findings in a relevant large animal model provide the rationale for moving this therapy forward into clinical trials in patients with CD20-positive B-cell malignancies.

Vaccination with adenovirus serotypes 35, 26, and 48 elicits higher levels of innate cytokine responses than adenovirus serotype 5 in rhesus monkeys

Adenovirus (Ad) vaccine vectors have proven highly immunogenic in multiple experimental models, but the innate immune responses induced by these vectors remain poorly characterized. Here we report innate cytokine responses to 5 different Ad vectors in 26 rhesus monkeys. Vaccination with adenovirus serotype 35 (Ad35), Ad26, and Ad48 induced substantially higher levels of antiviral (gamma interferon [IFN-γ], 10-kDa gamma interferon-induced protein [IP-10]) and proinflammatory (interleukin 1 receptor antagonist [IL-1RA], IL-6) cytokines than vaccination with Ad5 on day 1 following immunization. In vitro studies with capsid chimeric vectors and receptor-blocking monoclonal antibodies suggested that fiber-receptor interactions, as well as other capsid components, were critical for triggering these innate responses. Moreover, multiple cell populations, including dendritic cells, monocytes/macrophages, and T lymphocytes, contributed to these innate cytokine profiles. These data demonstrate that Ad35, Ad26, and Ad48, which utilize CD46 as their primary cellular receptor, induce significantly greater innate cytokine responses than Ad5, which uses the coxsackievirus and adenovirus receptor (CAR). These differences in innate triggering result in markedly different immunologic milieus for the subsequent generation of adaptive immune responses by these vaccine vectors.

Type I IFN induced by adenovirus serotypes 28 and 35 has multiple effects on T cell immunogenicity

Recombinant adenovirus (rAd) vectors are being investigated as vaccine delivery vehicles in preclinical and clinical studies. rAds constructed from different serotypes differ in receptor usage, tropism, and ability to activate cells, aspects of which likely contribute to their different immunogenicity profiles. In this study, we compared the infectivity and cell stimulatory capacity of recombinant adenovirus serotype 5 (rAd5), recombinant adenovirus serotype 28 (rAd28), and recombinant adenovirus serotype 35 (rAd35) in association with their respective immunogenicity profiles. We found that rAd28 and rAd35 infected and led to the in vitro maturation and activation of both human and mouse dendritic cells more efficiently compared with rAd5. In stark contrast to rAd5, rAd28 and rAd35 induced production of IFN-α and stimulated IFN-related intracellular pathways. However, the in vivo immunogenicity of rAd28 and rAd35 was significantly lower than that of rAd5. Deletion of IFN-α signaling during vaccination with rAd28 and rAd35 vectors increased the magnitude of the insert-specific T cell response to levels induced by vaccination with rAd5 vector. The negative impact of IFN-α signaling on the magnitude of the T cell response could be overcome by increasing the vaccine dose, which was also associated with greater polyfunctionality and a more favorable long-term memory phenotype of the CD8 T cell response in the presence of IFN-α signaling. Taken together, our results demonstrate that rAd-induced IFN-α production has multiple effects on T cell immunogenicity, the understanding of which should be considered in the design of rAd vaccine vectors.

The number of Toll-like receptor 9-agonist motifs in the adenovirus genome correlates with induction of dendritic cell maturation by adenovirus immune complexes

Adenovirus serotype 5 (Ad5) vectors and specific neutralizing antibodies (NAbs) generate immune complexes (ICs) which are potent inducers of dendritic cell (DC) maturation. Here we show that ICs generated with rare Ad vector serotypes, such as Ad26 and Ad35, which are lead candidates in HIV vaccine development, are poor inducers of DC maturation and that their potency in inducing DC maturation strongly correlated with the number of Toll-like receptor 9 (TLR9)-agonist motifs present in the Ad vector's genome. In addition, we showed that antihexon but not antifiber antibodies are responsible for the induction of Ad IC-mediated DC maturation.

Attenuation of CD4+ T-cell function by human adenovirus type 35 is mediated by the knob protein

The complement-regulatory protein CD46 is the primary receptor for human adenovirus type 35 (HAdV-35) and can regulate human immune-cell activation. CD4(+) T-cells are critical for initiating and maintaining adaptive immunity elicited by infection or vaccination. It was reported previously that HAdV-35 can bind these cells and suppress their activation. The data reported here demonstrate that recombinant trimeric HAdV-35 knob proteins alone can induce CD46 receptor downregulation and inhibit interleukin-2 production and proliferation of human CD4(+) T-cells in vitro similarly to mAbs specific to the CD46 region bound by HAdV-35 knobs. A mutant knob protein with increased affinity for CD46 compared with the wild-type knob caused equivalent effects. In contrast, a CD46-binding-deficient mutant knob protein did not inhibit T-cell activation. Thus, the capacity of HAdV-35 to attenuate human CD4(+) T-cell activation depends predominantly on knob interactions with CD46 and can occur independently of infection.

CEA promoter-regulated oncolytic adenovirus-mediated Hsp70 expression in immune gene therapy for pancreatic cancer

Gene therapy is an important means for the comprehensive treatment of pancreatic cancer. Challenges associated with gene therapy include control of vector security and effective genetic screening. In this paper, a CEA promoter-regulated oncolytic adenovirus vector was constructed. The reporter gene assay demonstrated that the viral vector was confirmed to have tumor-specific replication features. In vitro cytology studies showed that the CEA promoter regulated the proliferation of the adenovirus vector carrying the Hsp70 gene (AdCEAp-Hsp70), which significantly increased the expression levels of Hsp70 in the CEA-positive pancreatic cancer cells, resulting in an overall reduction in the survival of cancer cells. In the human pancreatic cancer Panc-1 xenograft model in immune deficient nude mice, the CEA promoter-regulated adenovirus AdCEAp-Hsp70 significantly inhibited tumor growth. In the rat pancreatic cancer DSL-6A/C1 xenograft model in rats, the viral proliferation and high expression levels of Hsp70 promoted the interstitial infiltration of CD4+, CD8+ and gamma/delta T cells into tumors, induced host secretion of the cytokines TGF-β, INF-γ, and IL-6 and had a dual anti-tumor effects that completely inhibited the growth of pancreatic cancer. The results demonstrated that the oncolytic adenovirus under the control of CEA promoter provides additional assurances regarding the safety and efficiency of cancer gene therapy. This gene therapy model improves anti-cancer efficiency and has broad applications and developmental prospects.

Vaccine vectors derived from a large collection of simian adenoviruses induce potent cellular immunity across multiple species

Replication-defective adenovirus vectors based on human serotype 5 (Ad5) induce protective immune responses against diverse pathogens and cancer in animal models, as well as elicit robust and sustained cellular immunity in humans. However, most humans have neutralizing antibodies to Ad5, which can impair the immunological potency of such vaccines. Here, we show that rare serotypes of human adenoviruses, which should not be neutralized in most humans, are far less potent as vaccine vectors than Ad5 in mice and nonhuman primates, casting doubt on their potential efficacy in humans. To identify novel vaccine carriers suitable for vaccine delivery in humans, we isolated and sequenced more than 1000 adenovirus strains from chimpanzees (ChAd). Replication-defective vectors were generated from a subset of these ChAd serotypes and screened to determine whether they were neutralized by human sera and able to grow in human cell lines. We then ranked these ChAd vectors by immunological potency and found up to a thousandfold variation in potency for CD8+ T cell induction in mice. These ChAd vectors were safe and immunologically potent in phase 1 clinical trials, thereby validating our screening approach. These data suggest that the ChAd vectors developed here represent a large collection of non-cross-reactive, potent vectors that may be exploited for the development of new vaccines.

Chapter six--Adenovirus-based immunotherapy of cancer: promises to keep

Progress in vector design and an increased knowledge of mechanisms underlying tumor-induced immune suppression have led to a new and promising generation of Adenovirus (Ad)-based immunotherapies, which are discussed in this review. As vaccine vehicles Ad vectors (AdVs) have been clinically evaluated and proven safe, but a major limitation of the commonly used Ad5 serotype is neutralization by preexistent or rapidly induced immune responses. Genetic modifications in the Ad capsid can reduce intrinsic immunogenicity and facilitate escape from antibody-mediated neutralization. Further modification of the Ad hexon and fiber allows for liver and scavenger detargeting and selective targeting of, for example, dendritic cells. These next-generation Ad vaccines with enhanced efficacy are now becoming available for testing as tumor vaccines. In addition, AdVs encoding immune-modulating products may be used to convert the tumor microenvironment from immune-suppressive and proinvasive to proinflammatory, thus facilitating cell-mediated effector functions that can keep tumor growth and invasion in check. Oncolytic AdVs, that selectively replicate in tumor cells and induce an immunogenic form of cell death, can also be armed with immune-activating transgenes to amplify primed antitumor immune responses. These novel immunotherapy strategies, employing highly efficacious AdVs in optimized configurations, show great promise and warrant clinical exploration.

Synergism/complementarity of recombinant adenoviral vectors and other vaccination platforms during induction of protective immunity against malaria

The lack of immunogenicity of most malaria antigens and the complex immune responses required for achieving protective immunity against this infectious disease have traditionally hampered the development of an efficient human malaria vaccine. The current boom in development of recombinant viral vectors and their use in prime-boost protocols that result in enhanced immune outcomes have increased the number of malaria vaccine candidates that access pre-clinical and clinical trials. In the frontline, adenoviruses and poxviruses seem to be giving the best immunization results in experimental animals and their mutual combination, or their combination with recombinant proteins (formulated in adjuvants and given in sequence or being given as protein/virus admixtures), has been shown to reach unprecedented levels of anti-malaria immunity that predictably will be somehow reproduced in the human setting. However, all this optimism was previously seen in the malaria vaccine development field without many real applicable results to date. We describe here the current state-of-the-art in the field of recombinant adenovirus research for malaria vaccine development, in particular referring to their use in combination with other immunogens in heterologous prime-boost protocols, while trying to simultaneously show our contributions and point of view on this subject.

Long-term humoral and cellular immune responses elicited by a heterologous Plasmodium vivax apical membrane antigen 1 protein prime/adenovirus boost immunization protocol

Apical membrane antigen 1 (AMA-1) is an invasion-related Plasmodium antigen that is expressed during both intracellular and extracellular asexual stages of the parasite's life cycle, making it an ideal target for induction of humoral and cellular immune responses that can protect against malaria. We show here that when it is administered as a recombinant protein (P) in Montanide ISA720 adjuvant, followed by a recombinant human type 5 adenovirus (Ad), intense and long-lasting Plasmodium vivax AMA-1-specific antibody responses (including both IgG1 and IgG2a), as well as proliferative memory T cell responses, can be detected in immunized mice. Memory T cells displayed both central (CD44(hi) CD62L(hi)) and effector (CD44(hi) CD62L(lo)) phenotypes, with the central memory phenotype prevailing (56% of AMA-1-specific proliferating cells). Considering the main traits of the memory immune responses induced against AMA-1, this particular sequence of immunogens (P followed by Ad), but no others (Ad/Ad, Ad/P, or P/P), displayed an optimal synergistic effect. These results give further support to the need for preclinical studies of P. vivax vaccine candidate AMA-1 administered in prime/boost protocols that include recombinant proteins and adenoviral vectors.

Plasmacytoid dendritic cells infiltrate the skin in positive tuberculin skin test indurations

Plasmacytoid dendritic cells (pDCs) are rarely present in normal skin but have been shown to infiltrate lesions of infections or autoimmune disorders. Here, we report that several DC subsets including CD123(+) BDCA-2/CD303(+) pDCs accumulate in the dermis in indurations induced by the tuberculin skin test (TST), used to screen immune sensitization by Mycobacterium tuberculosis. Although the purified protein derivate (PPD) used in the TST did not itself induce pDC recruitment or IFN-α production, the positive skin reactions showed high expression of the IFN-α-inducible protein MxA. In contrast, the local immune response to PPD was associated with substantial cell death and high expression of the cationic antimicrobial peptide LL37, which together can provide a means for pDC activation and IFN-α production. In vitro, pDCs showed low uptake of PPD compared with CD11c(+) and BDCA-3/CD141(+) myeloid DC subsets. Furthermore, supernatants from pDCs activated with LL37-DNA complexes reduced the high PPD uptake in myeloid DCs, as well as decreased their capacity to activate T-cell proliferation. Infiltrating pDCs in the TST reaction site may thus have a regulatory effect upon the antigen processing and presentation functions of surrounding potent myeloid DC subsets to limit potentially detrimental and excessive immune stimulation.