Impact of preexisting and induced humoral and cellular immune responses in an adenovirus-based gene therapy phase I clinical trial for localized mesothelioma

Telomeres and telomerase in mesothelioma: Pathophysiology, biomarkers and emerging therapeutic strategies (Review)

Malignant mesothelioma (MM) is a rare but aggressive cancer linked to asbestos exposure and characterized by advanced‑stage disease at presentation. Despite advances in treatment, prognosis remains abysmal, highlighting the imperative for the development of novel biomarkers and treatment approaches. Telomere biology plays a pivotal role in the tumorigenic process and has emerged as a key area in oncology research. Short telomeres have been associated with genomic instability, and substantially shorter telomere length (TL) has been identified in MM, showcasing the potential of TL in risk assessment, early detection, and disease progression monitoring. MM predominantly maintains TL through telomerase activity (TA), which in research has been identified in >90% of MM cases, underscoring the potential of TA as a biomarker in MM. Telomerase reverse transcriptase (TERT) polymorphisms may serve as valuable biomarkers, with research identifying associations between single nucleotide polymorphisms (SNPs) and the risk and prognosis of MM. Additionally, TERT promoter mutations have been associated with poor prognosis and advanced‑stage disease, with the non‑canonical functions of TERT hypothesized to contribute to the development of MM. TERT promoter mutations occur in ~12% of MM cases; C228T, C250T and A161C are the most common, while the distribution and frequency differ depending on histological subtype. Research reveals the promise of the various approaches therapeutically targeting telomerase, with favorable results in pre‑clinical models and inconclusive findings in clinical trials. The present review examines the role of telomere biology in MM and its implications in diagnosis, prognosis, and therapy.

Development of a low-seroprevalence, αvβ6 integrin-selective virotherapy based on human adenovirus type 10

Oncolytic virotherapies (OV) hold immense clinical potential. OV based on human adenoviruses (HAdV) derived from HAdV with naturally low rates of pre-existing immunity will be beneficial for future clinical translation. We generated a low-seroprevalence HAdV-D10 serotype vector incorporating an αvβ6 integrin-selective peptide, A20, to target αvβ6-positive tumor cell types. HAdV-D10 has limited natural tropism. Structural and biological studies of HAdV-D10 knob protein highlighted low-affinity engagement with native adenoviral receptors CAR and sialic acid. HAdV-D10 fails to engage blood coagulation factor X, potentially eliminating "off-target" hepatic sequestration in vivo. We engineered an A20 peptide that selectively binds αvβ6 integrin into the DG loop of HAdV-D10 fiber knob. Assays in αvβ6+ cancer cell lines demonstrated significantly increased transduction mediated by αvβ6-targeted variants compared with controls, confirmed microscopically. HAdV-D10.A20 resisted neutralization by neutralizing HAdV-C5 sera. Systemic delivery of HAdV-D10.A20 resulted in significantly increased GFP expression in BT20 tumors. Replication-competent HAdV-D10.A20 demonstrated αvβ6 integrin-selective cell killing in vitro and in vivo. HAdV-D10 possesses characteristics of a promising virotherapy, combining low seroprevalence, weak receptor interactions, and reduced off-target uptake. Incorporation of an αvβ6 integrin-selective peptide resulted in HAdV-D10.A20, with significant potential for clinical translation.

Bioreducible polymer-mediated delivery of oncolytic adenovirus can attenuate antiviral immune response and concurrently enhance induction of antitumor immune response to effectively prevent metastasis

Oncolytic virotherapy is highly promising and novel treatment modality for cancer. Several clinical trials with oncolytic viruses have illustrated that the potent antitumor efficacy of these viruses may rely on...

Next-Generation Vaccines: Nanoparticle-Mediated DNA and mRNA Delivery

Nucleic acid vaccines are a method of immunization aiming to elicit immune responses akin to live attenuated vaccines. In this method, DNA or messenger RNA (mRNA) sequences are delivered to the body to generate proteins, which mimic disease antigens to stimulate the immune response. Advantages of nucleic acid vaccines include stimulation of both cell-mediated and humoral immunity, ease of design, rapid adaptability to changing pathogen strains, and customizable multiantigen vaccines. To combat the SARS-CoV-2 pandemic, and many other diseases, nucleic acid vaccines appear to be a promising method. However, aid is needed in delivering the fragile DNA/mRNA payload. Many delivery strategies have been developed to elicit effective immune stimulation, yet no nucleic acid vaccine has been FDA-approved for human use. Nanoparticles (NPs) are one of the top candidates to mediate successful DNA/mRNA vaccine delivery due to their unique properties, including unlimited possibilities for formulations, protective capacity, simultaneous loading, and delivery potential of multiple DNA/mRNA vaccines. This review will summarize the many varieties of novel NP formulations for DNA and mRNA vaccine delivery as well as give the reader a brief synopsis of NP vaccine clinical trials. Finally, the future perspectives and challenges for NP-mediated nucleic acid vaccines will be explored.

Oncolytic herpesvirus therapy for mesothelioma - A phase I/IIa trial of intrapleural administration of HSV1716

OBJECTIVES

Malignant Pleural Mesothelioma (MPM) remains a major oncological challenge with limited therapeutic options. HSV1716 is a replication restricted oncolytic herpes simplex virus with anti-tumor effects in multiple cell lines including MPM. Intrapleural treatment appeals because MPM is typically multifocal but confined to the pleura, and distant metastases are uncommon. We assessed the safety and possible efficacy of intrapleural HSV1716 for inoperable MPM.

MATERIALS AND METHODS

Patients with MPM received 1 × 10⁷iu HSV1716 injected via an indwelling intrapleural catheter (IPC) on one, two or four occasions a week apart. The primary endpoint was the safety and tolerability of HSV1716. Secondary endpoints were assessment of HSV1716 replication, detection of immune response and evaluation of tumor response.

RESULTS

Of thirteen patients enrolled, five had received previous pemetrexed-cisplatin chemotherapy, and eight were chemotherapy naïve. Three patients were enrolled to receive one dose, three patients to two doses and seven patients to four doses. The treatment was well-tolerated with few virus-related adverse events and no dose limiting toxicities. Twelve patients were evaluable for response, as one patient withdrew early after a catheter fracture. There was evidence of viral replication/persistence in pleural fluid in seven of the twelve patients. Induction of Th1 cytokine responses to HSV1716 treatment occurred in eight patients and four patients developed novel anti-tumor IgG. No objective responses were observed but disease stabilization was reported in 50 % of patients at 8 weeks.

CONCLUSIONS

Intrapleural HSV1716 was well-tolerated and demonstrated an anti-tumor immune response in MPM patients. These results provide a rationale for further studies with this agent in MPM and in combination with other therapies.

Scavenger receptor-mediated Ad5 entry and acLDL accumulation in monocytes/macrophages synergistically trigger innate responses against viral infection

Adenovirus serotype 5 (Ad5) is a common cause of respiratory tract infection, and populations worldwide have high prevalence of anti-Ad5 antibodies, implying extensively prior infection. Ad5 infection potently activates the host innate defense and inflammation, but the molecular mechanisms are not completely clarified. We report here that monocytes from Ad5-seropositive subjects upregulates the expression of scavenger receptor A (SR-A), and the increased SR-A promote the susceptibility of Ad5 entry and subsequent innate signaling activation. SR-A is also known as major receptor for lipid uptake, we therefore observed that monocytes from Ad5-seropositive subjects accumulated the acetylated low-density lipoprotein (acLDL) and had the elevated cellular stress to induce the activation of monocyte/macrophages. These findings demonstrate that SR-A-mediated Ad5 entry, innate signaling activation and acLDL accumulation synergistically trigger the robust antiviral innate and inflammatory responses, which are helpful to our understanding of the pathogenesis of adenovirus infection.

Intracavitary Therapeutics for Pleural Malignancies

Pleural malignancies remain a serious therapeutic challenge, and are frequently refractory to standard treatment; however, they have the advantage of occurring in an enclosed cavity readily accessible for examination, biopsy, and serial sampling. Novel therapeutics can be administered via intracavitary delivery to maximize efficacy by targeting the site of involvement and potentially mitigating the adverse effects of systemic therapies. The easy accessibility of the pleural space lends itself well to repeated sampling and analysis to determine efficacy and toxicity of a given treatment paradigm. These factors support the rationale for delivery of novel therapeutics directly into the pleural space.

Advances in systemic therapy for malignant mesothelioma: future perspectives

Malignant mesothelioma is a rare and aggressive form of cancer affecting the mesothelium. This mainly occupational disease is becoming more common in those countries where asbestos has been used for industrial applications. Notwithstanding the progress made in the field, patients do not survive more than 12 months on average with standard treatment. With the advent of next generation sequencing, it is now possible to study the mutational landscape of each tumor with the aim of identifying the genetic aberrations driving tumorigenesis. This review encompasses the latest research in the field, with particular attention to new chemotherapy combinatorial regimens, molecular targets and immunotherapies, providing a comprehensive picture of the current and future treatment options for malignant mesothelioma patients.

Formulation of the bivalent prostate cancer vaccine with surgifoam elicits antigen-specific effector T cells in PSA-transgenic mice

We previously developed and characterized an adenoviral-based prostate cancer vaccine for simultaneous targeting of prostate-specific antigen (PSA) and prostate stem cell antigen (PSCA). We also demonstrated that immunization of mice with the bivalent vaccine (Ad₅-PSA+PSCA) inhibited the growth of established prostate tumors. However, there are multiple challenges hindering the success of immunological therapies in the clinic. One of the prime concerns has been to overcome the immunological tolerance and maintenance of long-term effector T cells. In this study, we further characterized the use of the bivalent vaccine (Ad₅-PSA+PSCA) in a transgenic mouse model expressing human PSA in the mouse prostate. We demonstrated the expression of PSA analyzed at the mRNA level (by RT-PCR) and protein level (by immunohistochemistry) in the prostate lobes harvested from the PSA-transgenic (PSA-Tg) mice. We established that the administration of the bivalent vaccine in surgifoam to the PSA-Tg mice induces strong PSA-specific effector CD8⁺ T cells as measured by IFN-γ secretion and in vitro cytotoxic T-cell assay. Furthermore, the use of surgifoam with Ad₅-PSA+PSCA vaccine allows multiple boosting vaccinations with a significant increase in antigen-specific CD8⁺ T cells. These observations suggest that the formulation of the bivalent prostate cancer vaccine (Ad₅-PSA+PSCA) with surgifoam bypasses the neutralizing antibody response, thus allowing multiple boosting. This formulation is also helpful for inducing an antigen-specific immune response in the presence of self-antigen, and maintains long-term effector CD8⁺ T cells.

Genetic Modification of the Lung Directed Toward Treatment of Human Disease

Genetic modification therapy is a promising therapeutic strategy for many diseases of the lung intractable to other treatments. Lung gene therapy has been the subject of numerous preclinical animal experiments and human clinical trials, for targets including genetic diseases such as cystic fibrosis and α1-antitrypsin deficiency, complex disorders such as asthma, allergy, and lung cancer, infections such as respiratory syncytial virus (RSV) and Pseudomonas, as well as pulmonary arterial hypertension, transplant rejection, and lung injury. A variety of viral and non-viral vectors have been employed to overcome the many physical barriers to gene transfer imposed by lung anatomy and natural defenses. Beyond the treatment of lung diseases, the lung has the potential to be used as a metabolic factory for generating proteins for delivery to the circulation for treatment of systemic diseases. Although much has been learned through a myriad of experiments about the development of genetic modification of the lung, more work is still needed to improve the delivery vehicles and to overcome challenges such as entry barriers, persistent expression, specific cell targeting, and circumventing host anti-vector responses.

Barriers to systemic application of virus-based vectors in gene therapy: lessons from adenovirus type 5

Currently, virus-based vectors, namely derivatives of the adenovirus, are frequently used in a wide variety of ex vivo or local gene therapeutic applications. However, the efficacy of virus-based vectors in systemic applications is presently still extremely limited. Complex interactions of the various vector types with the patient's organism hinder successful vector deployment. Exemplary, here we summarize barriers to systemic application of Adenovirus-based vectors leading either to acute toxic effects or rapid vector neutralization and discuss strategies to overcome these barriers aiming to develop more efficient vector types.

Vascular endothelial growth factor promoter-based conditionally replicative adenoviruses effectively suppress growth of malignant pleural mesothelioma

Malignant mesothelioma (MM) incidence is increasing drastically worldwide as an occupational disease resulting from asbestos exposure. However, no curative treatment for MM of advanced stage is available. Thus, new therapeutic approaches for MM are required. Because malignant pleural mesothelioma (MPM) cells spread along the pleural surface in most patients, MPM can be targeted using intrapleural therapeutic approaches. In this study, we investigated the effectiveness of the intrapleural instillation of a replication‐competent adenovirus as an oncolytic agent against MPM. We constructed a vascular endothelial growth factor promoter‐based conditionally replicative adenovirus (VEGF‐CRAd) that replicates exclusively in VEGF‐expressing cells. All of the MM cell lines that we tested expressed VEGF mRNA, and VEGF‐CRAd selectively replicated in these MM cells and exerted a direct concentration‐dependent oncolytic effect in vitro. Furthermore, our in vivo studies showed that pre‐infection of MM cells with VEGF‐CRAd potently suppressed MPM tumor formation in nude mice, and that intrapleural instillation of VEGF‐CRAd prolonged the survival time of tumor‐bearing mice. Our results indicate that VEGF‐CRAd exerts an oncolytic effect on MM cells and that intrapleural instillation of VEGF‐CRAd is safe and might represent a promising therapeutic strategy for MPM.

Substitution of blood coagulation factor X-binding to Ad5 by position-specific PEGylation: Preventing vector clearance and preserving infectivity

The biodistribution of adenovirus type 5 (Ad5) vector particles is heavily influenced by interaction of the particles with plasma proteins, including coagulation factor X (FX), which binds specifically to the major Ad5 capsid protein hexon. FX mediates hepatocyte transduction by intravenously-injected Ad5 vectors and shields vector particles from neutralization by natural antibodies and complement. In mice, mutant Ad5 vectors that are ablated for FX-binding become detargeted from hepatocytes, which is desirable for certain applications, but unfortunately such FX-nonbinding vectors also become sensitive to neutralization by mouse plasma proteins. To improve the properties of Ad5 vectors for systemic delivery, we developed a strategy to replace the natural FX shield by a site-specific chemical polyethylene glycol shield. Coupling of polyethylene glycol to a specific site in hexon hypervariable region 1 yielded vector particles that were protected from neutralization by natural antibodies and complement although they were unable to bind FX. These vector particles evaded macrophages in vitro and showed significantly improved pharmacokinetics and hepatocyte transduction in vivo. Thus, site-specific shielding of Ad5 vectors with polyethylene glycol rendered vectors FX-independent and greatly improved their properties for systemic gene therapy.

Bio-inspired polymer envelopes around adenoviral vectors to reduce immunogenicity and improve in vivo kinetics

Adenoviral vectors have attracted substantial interest for systemic tumor gene therapy, but further work is needed to reduce their immunogenicity and alter their biodistribution before they can be used in the clinic. Here we describe a bio-inspired, cleavable PEGylated β-cyclodextrin-polyethyleneimine conjugate (CDPCP) that spontaneously coats adenovirus in solution. This cleavable PEG coating reduces the innate and adaptive immunogenicity of adenovirus particles, as well as improves their biodistribution away from the liver and into the tumor. Insertion of a matrix metalloproteinase substrate sequence into the conjugate allows PEG cleavage at the tumor site, simultaneously reducing liver biodistribution and increasing transgene expression in tumors, thereby avoiding the "PEG dilemma". Cationic β-cyclodextrin-PEI not only provides electrostatic attraction to promote envelope attachment to the viral capsid, but it also improves vector internalization and transduction after PEG cleavage. These results suggest that CDPCP may help expand the use of adenoviral vectors in cancer gene therapy.

STATEMENT OF SIGNIFICANCE

The synthesized β-cyclodextrin-PEI-MMP-cleavable-PEG polymer (CDPCP), held great potential for gene therapy when applied for adenovirus coating. The β-cyclodextrin-PEI provided a powerful electrostatic attraction to attach the whole polymer onto the viral capsid, while the MMPs-cleavable PEG reduced innate and adaptive immunogenicity and improved the biodistribution of adenovirus vectors due to the tumor-specific enzyme triggered PEG cleavage. More importantly, an ingenious cooperation between the two components could solve the PEG dilemma. The CDPCP/Ad complexes exhibited a comprehensive and valued profile to be a candidate vector for future tumor gene therapy, we believe the current investigation on this kind of biomaterial may be of particular interest to the readership of Acta biomaterialia.

Polymeric oncolytic adenovirus for cancer gene therapy

Oncolytic adenovirus (Ad) vectors present a promising modality to treat cancer. Many clinical trials have been done with either naked oncolytic Ad or combination with chemotherapies. However, the systemic injection of oncolytic Ad in clinical applications is restricted due to significant liver toxicity and immunogenicity. To overcome these issues, Ad has been engineered physically or chemically with numerous polymers for shielding the Ad surface, accomplishing extended blood circulation time and reduced immunogenicity as well as hepatotoxicity. In this review, we describe and classify the characteristics of polymer modified oncolytic Ad following each strategy for cancer treatment. Furthermore, this review concludes with the highlights of various polymer-coated Ads and their prospects, and directions for future research.

Tuning Surface Charge and PEGylation of Biocompatible Polymers for Efficient Delivery of Nucleic Acid or Adenoviral Vector

As an effective and safe strategy to overcome the limits of therapeutic nucleic acid or adenovirus (Ad) vectors for in vivo application, various technologies to modify the surface of vectors with nonimmunogenic/biocompatible polymers have been emerging in the field of gene therapy. However, the transfection efficacy of the polymer to transfer genetic materials is still relatively weak. To develop more advanced and effective polymers to deliver not only Ad vectors, but also nucleic acids, 6 biocompatible polymers were newly designed and synthesized to different sizes (2k, 3.4k, or 5k) of poly(ethylene) glycol (PEG) and different numbers of amine groups (2 or 5) based on methoxy poly(ethylene glycol)-b-poly{N-[N-(2-aminoethyl)-2-aminoethyl]-l-glutamate (PNLG). We characterized size distribution and surface charge of 6 PNLGs after complexation with either nucleic acid or Ad. Among all 6 PNLGs, the 5 amine group PNLG showed the strongest efficacy in delivering nucleic acid as well as Ad vectors. Interestingly, cellular uptake results showed higher uptake ability in Ad complexed with 2 amine group PNLG than Ad/5 amine group PNLG, suggesting that the size of Ad/PNLGs is more essential than the surface charge for cellular uptake in polymers with charges greater than 30 mV. Moreover, the endosome escape ability of Ad/PNLGs increased depending on the number of amine groups, but decreased by PEG size. Cancer cell killing efficacy and immune response studies of oncolytic Ad/PNLGs showed 5 amine group PNLG to be a more effective and safe carrier for delivering Ad. Overall, these studies provide new insights into the functional mechanism of polymer-based approaches to either nucleic acid or Ad/nanocomplex. Furthermore, the identified ideal biocompatible PNLG polymer formulation (5 amine/2k PEG for nucleic acid, 5 amine/5k PEG for Ad) demonstrated high transduction efficiency as well as therapeutic value (efficacy and safety) and thus has strong potential for in vivo therapeutic use in the future.

A clinical protocol to inhibit the HGF/c-Met pathway for malignant mesothelioma with an intrapleural injection of adenoviruses expressing the NK4 gene

Background

The hepatocyte growth factor (HGF)/c-Met signal pathway is up-regulated in human mesothelioma and suppression of the HGF/c-Met signaling with a competitive inhibitor, NK4 homologous to HGF in the structure, produced anti-tumor effects to mesothelioma in a preclinical study. Mesothelioma is highly resistant to a number of chemotherapeutic agents but distant metastasis to extra-thoracic organs is relatively infrequent until the late stage.

Methods/design

We planned to conduct a clinical study of gene therapy with adenoviruses expressing the NK4 gene (Ad-NK4) to control the local tumor growth. The study is designed to inject Ad-NK4 into the intrapleural cavity with a dose escalation manner from 10¹⁰ to 10¹² virus particles per patient and to examine safety and possible clinical benefits. The clinical investigation is a first-in-human trial to use the NK4 gene and to block the HGF/c-Met pathway with gene medicine. We conducted in vivo animal experiments to examine the safety level as one of the preclinical studies, and showed that Ad DNA administered in the pleural cavity was detected in many parenchymal organs. Biochemical and pathological analyses showed that liver damages were the major adverse effects with little toxicity to other organs. These studies firstly demonstrated biodistribution and transgene expression after an intrapleural injection of Ad vectors in an animal study, which contrasts with an intravenous injection showing relatively rapid clearance of Ad-NK4.

Discussion

The clinical study can also provide information regarding production of NK4 protein and antibody against NK4, and inhibition levels of the HGF/c-Met pathway by detecting dephosphorylation of c-Met in mesothelioma cells. These data will be crucial to judge whether local production of NK4 molecules can be an anti-cancer strategy.

Trial registration: UMIN clinical trials registry, Japan. Register ID: UMIN15771

Efficient lung orthotopic tumor-growth suppression of oncolytic adenovirus complexed with RGD-targeted bioreducible polymer

Oncolytic adenoviruses (Ad) have been developed for the eradication of tumors. Although they hold much promise as a cancer therapy, they have a short blood circulation time and high liver toxicity. An effective strategy to overcome these problems has been complexing Ad with shielding materials. However, the therapeutic efficacy of the Ad complexes has also been an issue because passive accumulation does not allow for sufficient delivery of Ad to the cancer cells. To enhance the therapeutic efficacy of the polymer-coated Ads, the attachment of a targeting moiety to polymer-coated Ad vectors is inescapable. Our lab has previously reported the potential use of Arg-Gly-Asp (RGD)-targeted bioreducible polymers with a polyethylene glycol (PEG) linker for delivering oncolytic Ads. We have shown the enhanced in vitro transduction efficiency and increased cancer-killing effect with producing progeny oncolytic Ad particles. In addition, we have shown significant tumor-growth inhibition of the polymer-shielded Ad in an in vivo lung orthotopic tumor model. The shielding effect of the Ad surface with the polymers allowed evasion of host immune responses and reduction of liver toxicity. This data demonstrates that the RGD-conjugated bioreducible polymer for delivering the oncolytic Ad vectors could be utilized for cancer therapy via systemic administration.

Intramuscular DNA vaccination protocols mediated by electric fields

Vaccination is historically one of the most important methods for preventing infectious diseases in humans and animals. New insights in the biology of the immune system allow a more rational design of vaccines, and new vaccination strategies are emerging. DNA vaccines have been proposed as a promising approach for introducing foreign antigens into the host for inducing protective immunity against infectious and cancer diseases. Nevertheless, because of their poor immunogenicity, plasmid DNA vaccination strategies need further implementations. Recent data suggest electrotransfer as a useful tool to improve DNA-based vaccination protocols, being able to stimulate both the humoral and cellular immune responses. In preclinical trials, gene electrotransfer is successfully used in prime-boost combination protocols and its tolerability and safety has been demonstrated also in Phase I clinical trials. In this chapter, we report a short comment supporting electrotransfer as an effective strategy to improve DNA-based vaccination protocols and describe the vaccination procedures by plasmid DNA in combination with electrotransfer and hyaluronidase pretreatment in use in our laboratory.

The prevalence of neutralising antibodies to chimpanzee adenovirus type 6 and type 7 in healthy adult volunteers, patients with chronic hepatitis B and patients with primary hepatocellular carcinoma in China

The presence of neutralising antibodies (NAbs) against adenovirus in the population is a major hurdle preventing the effective use of replication-defective adenoviruses (Ads) as candidates for gene therapy and vaccine vectors for many diseases. Only a few studies have described the epidemiology of pre-existing immunity to chimpanzee Ads in China. To assess the prevalence of NAbs to chimpanzee adenovirus serotypes 6 and 7 (AdC6 and AdC7), we enrolled 998 healthy participants from five regions in China as well as 196 chronic hepatitis B virus (HBV) patients and 193 primary hepatocellular carcinoma (HCC) patients from Chongqing, China. The total seroprevalence rates of AdC6 and AdC7 NAbs in the healthy participants were 12.22 % (122/998) (95 % confidence interval [CI], 10.34-14.40 %) and 13.13 % (131/998) (95 % CI, 11.17-15.36 %), respectively. The seroprevalence rates of AdC6 and AdC7 NAbs in the HBV patients were 21.43 % (42/196) (95 % CI, 16.26-27.69 %) and 25.51 % (50/196) (95 % CI, 19.92-32.04 %), respectively. The seroprevalence rates of AdC6 and AdC7 NAbs in the HCC patients were 27.46 % (53/193) (95 % CI, 21.65-34.15 %) and 31.09 % (60/193) (95 % CI, 24.98-37.93 %), respectively. The seroprevalence rates of these Ads were not associated with age and gender. The present study may provide useful insights for developing future AdC-based vaccines and gene therapies.

Intracavitary therapeutics for pleural malignancies

Pleural malignancies are ideal for novel therapeutic approaches because they are invariably fatal. Intrapleural (IP) chemotherapy has only marginal benefit in pleural malignancies, but may prove efficacious with hyperthermic chemotherapy administered in combination with maximal tumor debulking. IP immunotherapies may be most effective in those patients with early-stage pleural malignancy, and may prove superior to standard pleurodesis methods in control of effusion and prolongation of survival. Immunogene therapy may be unable to successfully treat bulky tumors on its own, but success may be achieved with combination approaches that combine debulking surgery and chemotherapy with IP genetic immunotherapy.

Therapeutic efficacy of a systemically delivered oncolytic adenovirus - biodegradable polymer complex

Despite great efforts to develop a more effective oncolytic adenovirus (Ad) for eradicating tumors, in vivo application via systemic administration is strictly limited to local injection due to host immune responses by Ad surface proteins and liver accumulation by the inherent nature of the Ad. In the last decade, numerous techniques using synthetic polymers have widely emerged to shield the exterior of therapeutic Ad vectors for systemic delivery. We developed a cationic polymer linked with polyethylene glycol for systemically delivering oncolytic Ad. The increased transduction efficiency and oncolytic effect of the Ad vectors physically coated with the polymer were evaluated, showing the optimal size (130 nm) of the Ad/polymer complex for systemic administration and prolonged stability of the Ad/polymer complex. Marked tumor growth suppression of the oncolytic Ad delivered by the polymer through systemic injection was observed in HT1080 and A549 xenograft models. The masking effect of the Ad surface by the polymer elicited evasion of innate adaptive immune responses and the tumor-to-liver ratio of the complex was significantly elevated 1229-fold greater than that of a naked Ad. These results demonstrate that the potential system of oncolytic Ad complexed with the biodegradable polymer may be useful for developing therapeutic vector systems via systemic delivery.

Gene therapy for malignant mesothelioma: current prospects and challenges

Malignant mesothelioma, developed in the thoracic cavity, is resistant to current treatments. Suppression of the local tumor growth is beneficial to the patients since mesothelioma infrequently metastasizes to extrapleural organs. A majority of the tumors have a homologous genetic deletion at the INK4A/ARF locus that includes the p14ARF and the p16INK4A genes, and the genetic defect results in an inactivation of the p53-mediated pathways and in progression of cell cycle through pRb phosphorylation. Preclinical studies targeting the genetic abnormality with adenoviruses showed that restoration of the p53 pathways induced pRb dephosphorylation and subsequently produced anti-tumor effects. A number of preclinical studies with different genes and vector systems demonstrated the therapeutic efficacy and raised the possibility of gene therapy in clinical settings. An intrapleural administration of vectors has several advantages in transducing pleural mesothelioma but activates rapid antibody production which impedes further gene expression. There have been several clinical studies conducted for mesothelioma and these trials showed the feasibility of intrapleural administrations of adenovirus vectors. In this review we summarize major preclinical and clinical gene therapy for mesothelioma, and discuss the advantages of gene therapy in the context of stimulating host immune systems. Accumulating clinical data suggest that an intrapleural administration of viral vectors has distinct aspects which are not observed in other administration routes.

Deep RNA sequencing reveals complex transcriptional landscape of a bat adenovirus

Bat adenoviruses are a group of recently identified adenoviruses (AdVs) which are highly prevalent in bats yet share low similarity to known AdVs from other species. In this study, deep RNA sequencing was used to analyze the transcriptome at five time points following the infection of a bat AdV in a kidney cell line derived from a myotis bat species. Evidence of AdV replication was observed with the proportion of viral RNAs ranging from 0.01% at 6 h to 1.3% at 18 h. Further analysis of viral temporal gene expression revealed three replication stages, the early-stage genes encoding mainly host interaction proteins, the intermediate-stage genes for the DNA replication and assembly proteins, and the late-stage genes for most structural proteins. Several bat AdV genes were expressed at stages that differed from those of their counterpart genes previously reported for human AdV type 2. In addition, single-base resolution splice sites of several genes and promoter regions of all 30 viral genes were fully determined. Simultaneously, the temporal cellular gene expression profiles were identified. The most overrepresented functional categories of the differentially expressed genes were related to cellular immune response, transcription, translation, and DNA replication and repair. Taken together, the deep RNA sequencing provided a global, transcriptional profile of the novel bat AdV and the virus-host interactions which will be useful for the understanding and investigation of AdV replication, pathogenesis, and specific virus-bat interactions in future research.

Asbestos-related pleuropulmonary diseases: benign and malignant

Asbestos is known for its desirable properties of thermal and heat resistance along with excellent strength and durability. It was widely used in many industries since the late 19th century, until its adverse effects on health were recognized. The occurrence of pleuropulmonary changes from exposure to asbestos often has a latency period of 20 to 30 years. The use of asbestos has been banned, regulated, and minimized in many countries, but in several developing countries, the use of asbestos in industries is still a common practice. In this article, the benign and malignant clinical manifestations of asbestos exposure are discussed.

Delivery of antigens by viral vectors for vaccination

Viral vectors have been developed as vaccine platforms for a number of pathogens and tumors. In particular, adenovirus (Ad)-based vectors expressing genes coding for pathogen or tumor antigens have proven efficacious to induce protective immunity. Major challenges in the use of Ad vectors are the high prevalence of anti-Ad immunity and the recent observation during an Ad-based HIV vaccine trial that led to increased HIV-1 acquisition in the presence of circulating anti-Ad5 neutralizing antibodies. In this review we summarize strategies to address these challenges and focus on modifications of the Ad capsid to enhance the adjuvant effect of anti-Ad immunogenicity and to circumvent pre-existing immunity. In addition, we summarize the current status and potential of other viral vector vaccines based on adeno-associated viruses, lentiviruses and poxviruses.

Circumventing antivector immunity by using adenovirus-infected blood cells for repeated application of adenovirus-vectored vaccines: proof of concept in rhesus macaques

Adenovirus has been extensively exploited as a vector platform for delivering vaccines. However, preexisting antiadenovirus immunity is the major stumbling block for application of adenovirus-vectored vaccines. In this study, we found that freshly isolated peripheral blood mononuclear cells (PBMCs), mostly CD14(+) cells, from adenovirus serotype 5 (Ad5)-seropositive primates (humans and rhesus macaques) can be efficiently infected with Ad5 in vitro. On the basis of this observation, a novel strategy based on adenoviral vector-infected PBMC (AVIP) immunization was explored to circumvent antivector immunity. Autologous infusion of Ad5-SIVgag-infected PBMCs elicited a strong Gag-specific cellular immune response but induced weaker Ad5-neutralizing antibody (NAb) in Ad5-seronegative macaques than in macaques intramuscularly injected with Ad5-SIVgag. Moreover, Ad5-seropositive macaques receiving multiple AVIP immunizations with Ad5-SIVenv, Ad5-SIVgag, and Ad5-SIVpol vaccines elicited escalated Env-, Gag-, and Pol-specific immune responses after each immunization that were significantly greater than those in macaques intramuscularly injected with these Ad5-SIV vaccines. After challenged intravenously with a highly pathogenic SIVmac239 virus, macaques receiving AVIP immunization demonstrated a significant reduction in viral load at both the peak time and set-point period compared with macaques without Ad5-SIV vaccines. Our study warranted further research and development of the AVIP immunization as a platform for repeated applications of adenovirus-vectored vaccines.

Linearized oncolytic adenoviral plasmid DNA delivered by bioreducible polymers

As an effort to overcome limits of adenovirus (Ad) as a systemic delivery vector for cancer therapy, we developed a novel system using oncolytic Ad plasmid DNA with two bioreducible polymers: arginine-grafted bioreducible poly(disulfide amine)polymer (ABP) and PEG5k-conjugated ABP (ABP5k) in expectation of oncolytic effect caused by progeny viral production followed by replication. The linearized Ad DNAs for active viral replication polyplexed with each polymer were able to replicate only in human cancer cells and produce progeny viruses. The non-immunogenic polymers delivering the DNAs markedly elicited to evade the innate and adaptive immune response. The biodistribution ratio of the polyplexes administered systemically was approximately 99% decreased in liver when compared with naked Ad. Moreover, tumor-to-liver ratio of the Ad DNA delivered by ABP or ABP5k was significantly elevated at 229- or 419-fold greater than that of naked Ad, respectively. The ABP5k improved the chance of the DNA to localize within tumor versus liver with 1.8-fold increased ratio. In conclusion, the innovative and simple system for delivering oncolytic Ad plasmid DNA with the bioreducible polymers, skipping time-consuming steps such as generation and characterization of oncolytic Ad vectors, can be utilized as an alternative approach for cancer therapy.

Enhancing the therapeutic efficacy of adenovirus in combination with biomaterials

With the reason that systemically administered adenovirus (Ad) is rapidly extinguished by innate/adaptive immune responses and accumulation in liver, in vivo application of the Ad vector is strictly restricted. For achieving to develop successful Ad vector systems for cancer therapy, the chemical or physical modification of Ad vectors with polymers has been generally used as a promising strategy to overcome the obstacles. With polyethylene glycol (PEG) first in order, a variety of polymers have been developed to shield the surface of therapeutic Ad vectors and well accomplished to extend circulation time in blood and reduce liver toxicity. However, although polymer-coated Ads can successfully evacuate from a series of guarding systems in vivo and locate within tumors by enhanced permeability and retention (EPR) effect, the possibility to entering into the target cell is few and far between. To endow targeting moiety to polymer-coated Ad vectors, a diversity of ligands such as tumor-homing peptides, growth factors or antibodies, have been introduced with avoiding unwanted transduction and enhancing therapeutic efficacy. Here, we will describe and classify the characteristics of the published polymers with respect to Ad vectors. Furthermore, we will also compare the properties of variable targeting ligands, which are being utilized for addressing polymer-coated Ad vectors actively.

Chemotherapy and targeted therapies for unresectable malignant mesothelioma

The global burden of mesothelioma is expected to increase in the coming decades. As a result the development of more effective therapies with an emphasis on personalized treatments based on validated prognostic and predictive biomarkers is an essential requirement. Progress has been made in the last decade with the development of newer generation anti-folates leading to the current standard of care of pemetrexed and cisplatin in patients with unresectable disease. However, the median overall survival of patients with this combination treatment is only 12 months. There is no consensus regarding second line therapy for patients who have progressed or not responded to pemetrexed based therapies although gemcitabine in combination with a platinum compound or single agent vinorelbine is a reasonable option. The development of effective targeted agents that are active in mesothelioma has to date been disappointing. Strategies involving the addition of bevacizumab to pemetrexed and cisplatin in the frontline setting, the histone deacetylase inhibitor vorinostat as second line therapy and studies evaluating the utility of maintenance therapy in mesothelioma are all ongoing and appear promising. In addition clinical trials investigating immunotherapy and gene therapy in combination with chemotherapy could potentially improve the prognosis of patients with mesothelioma.

Neoadjuvant in situ gene-mediated cytotoxic immunotherapy improves postoperative outcomes in novel syngeneic esophageal carcinoma models

Esophageal carcinoma is the most rapidly increasing tumor in the United States and has a dismal 15% 5-year survival. Immunotherapy has been proposed to improve patient outcomes; however, no immunocompetent esophageal carcinoma model exists to date to test this approach. We developed two mouse models of esophageal cancer by inoculating immunocompetent mice with syngeneic esophageal cell lines transformed by cyclin-D1 or mutant HRAS^G12V and loss of p53. Similar to humans, surgery and adjuvant chemotherapy (cisplatin and 5-fluorouracil) demonstrated limited efficacy. Gene-mediated cyototoxic immunotherapy (adenoviral vector carrying the herpes simplex virus thymidine kinase gene in combination with the prodrug ganciclovir; AdV-tk/GCV) demonstrated high levels of in vitro transduction and efficacy. Using in vivo syngeneic esophageal carcinoma models, combining surgery, chemotherapy and AdV-tk/GCV improved survival (P=0.007) and decreased disease recurrence (P<0.001). Mechanistic studies suggested that AdV-tk/GCV mediated a direct cytotoxic effect and an increased intra-tumoral trafficking of CD8 T cells (8.15% vs 14.89%, P=0.02). These data provide the first preclinical evidence that augmenting standard of care with immunotherapy may improve outcomes in the management of esophageal carcinoma.

Optimized PEGylated adenovirus vector reduces the anti-vector humoral immune response against adenovirus and induces a therapeutic effect against metastatic lung cancer

Application of adenovirus vectors (Adv) in metastatic cancer treatment is limited. We previously demonstrated that covalent conjugation of polyethleneglycol (PEG) to Adv enhances therapeutic effects and decreases toxic side-effects after systemic administration, but the level of immune response to PEGylated Adv (PEG-Ad) was not examined. Here, we examined the effect of PEGylation of Adv on the production of anti-Adv antibodies and antitumor response. We constructed a set of PEG-Ad using 5-kDa PEG, with modification rates of 30%, 45% and 90%. After systemic administration of Advs to rats, we examined the level of anti-Adv immunoglobulin (Ig)G and IgM in serum. The levels of anti-Adv IgG and anti-Adv IgM in rats treated with unmodified Adv were higher than those in control group. Rats treated with PEG-Ad that had a 90% modification rate showed lower level of anti-Adv IgG and anti-Adv IgM than those treated with unmodified Adv, whereas rats treated with PEG-Ad that had a 30% or 45% modification rate showed a similar level of anti-Adv IgG and IgM to those treated with unmodified Adv. Systemic administration of PEG-Ad that had a 90% modification rate, and expressed tumor necrosis factor-alpha, significantly reduced the number of metastatic colonies in the lung compared to unmodified Adv, with negligible side effects. These results suggest that systemic administration of PEG-Ad with an appropriate PEG modification rate has the potential to reduce the production of antibodies against Adv and increase the therapeutic response against metastatic cancer.

Short communication: enhancement of immunogenicity of replication-defective adenovirus-based human immunodeficiency virus vaccines in rhesus monkeys

Adenovirus (Ad) is still under extensive investigation as a vector for HIV vaccination; however, one possible explanation for the failure of Merck's STEP trial is the relatively weak immunogenicity of replication-defective Ad vectors. In this study, a novel strategy to enhance the immunogenicity of replication-defective Ad-based HIV vaccines was developed. First, a recombinant plasmid expressing adenoviral E1 protein (pVAX-E1) was constructed to complement the E1-deleted replication-defective Ad vectors in trans. Then, the immunogenicity of the vaccine regimen of Ad5-HIV gag plus pVAX-E1 plasmid was assessed in rhesus macaques. Compared with traditional administration of Ad-based vectors alone, the results showed that our strategy elicited a more sustained and robust HIV gag-specific cellular response and enhanced long-term proliferation of CD4(+) and CD8(+) T lymphocytes. This strategy represents a proof-of-concept that enhances the immunogenicity of replication-defective Ad-based vectors, and it exemplifies the useful implications for Ad-based HIV vaccines and other vaccines.

Epidemiology of adenovirus type 5 neutralizing antibodies in healthy people and AIDS patients in Guangzhou, southern China

Recombinant adenovirus serotype 5 (Ad5) viruses have been extensively explored as vectors for vaccination or gene therapy. However, one major obstacle to their clinical application is the high prevalence of preexisting anti-Ad5 immunity resulting from natural infection. It has been reported that there are geographic variations in the prevalence of natural adenovirus infection. In the present study, we investigated the seroprevalence of Ad5 in Guangzhou, southern China by measuring the Ad5 neutralizing antibodies in blood samples collected from several sites. The seroprevalence was 77.34% in the general healthy population. The seroprevalence and antibody titers increased with age, with the older population (41-72 years old) having the highest seropositivity (84.8%) and percentage (54.4%) of high Ad5 neutralizing antibody titers (>1000). The dynamics of Ad5 neutralizing antibodies were stable and persistent over the course of eight months. Furthermore, the seroprevalence of Ad5 in the HIV-infected AIDS patients was investigated and there was no significant difference from the general healthy population. Our survey provides useful insights for the future development of Ad5-based vaccination and gene therapy.

Protective anti-Pseudomonas aeruginosa humoral and cellular mucosal immunity by AdC7-mediated expression of the P. aeruginosa protein OprF

Replication-deficient adenoviral (Ad) vectors are an attractive platform for a vaccine against lung infections caused by Pseudomonas aeruginosa. Ad vectors based on non-human serotypes have been developed to circumvent the problem of pre-existing anti-Ad immunity in humans. The present study analyzes the anti-P. aeruginosa systemic and lung mucosal immunity elicited by a non-human primate-based AdC7 vector expressing the outer membrane protein F (AdC7OprF) of P. aeruginosa. Intramuscular immunization of mice with AdC7OprF induced similar levels of serum and mucosal anti-OprF IgG and increased levels of anti-OprF IgA in lung epithelial lining fluid (ELF) compared to immunization with a human serotype Ad5OprF vector (p>0.05). OprF-specific INF-γ in splenic T cells stimulated with OprF-pulsed syngeneic splenic dendritic cells (DC) was similar following immunization with AdC7OprF compared to Ad5OprF (p>0.05). In contrast, OprF-specific INF-γ responses in lung T cells stimulated with either spleen or lung DC were increased following immunization with AdC7OprF compared to Ad5OprF (p<0.05). Interestingly, direct administration of AdC7OprF to the respiratory tract resulted in an increase of OprF-specific IgG in serum, OprF-specific IgG and IgA in lung ELF, and OprF-specific INF-γ in lung T-cells compared to immunization with Ad5OprF, and survival following challenge with a lethal dose of P. aeruginosa. These data demonstrate that systemic or lung mucosal immunization with an AdC7-based vaccine vector induces superior pulmonary humoral and cellular anti-transgene immunity compared to immunization with an Ad5-based vector and favors AdC7-based vectors as vaccines to induce lung mucosal immunity.

Lentiviral vectors for immunization: an inflammatory field

Lentiviruses are retroviruses that are able to transduce both dividing and nondividing cells. Dendritic cells are key players in the innate and adaptive immune responses, and are natural targets for lentiviruses. Lentiviral vectors (LVs) have recently reached the clinical gene therapy arena, prompting their use as clinical vaccines. In recent years, LVs have emerged as a robust and practical experimental platform for gene delivery and rational genetic reprogramming of dendritic cells. Here, we present the status quo of the LV system for protective or therapeutic vaccine development. This vector system has been extensively evaluated for ex vivo and in vivo (immuno)gene delivery. Improvements of the LV design in order to further grant a higher biosafety profile for vaccine development are presented.

A phase I trial of repeated intrapleural adenoviral-mediated interferon-beta gene transfer for mesothelioma and metastatic pleural effusions

We previously showed that a single intrapleural dose of an adenoviral vector expressing interferon-beta (Ad.IFN-beta) in patients with malignant pleural mesothelioma (MPM) or malignant pleural effusions (MPE) resulted in gene transfer, humoral antitumor immune responses, and anecdotal clinical responses manifested by modified Response Evaluation Criteria in Solid Tumors (RECIST) disease stability in 3 of 10 patients at 2 months and an additional patient with significant metabolic response on positron emission tomography (PET) imaging. This phase I trial was conducted to determine whether using two doses of Ad.IFN-beta vector would be superior. Ten patients with MPM and seven with MPE received two doses of Ad.IFN-beta through an indwelling pleural catheter. Repeated doses were generally well tolerated. High levels of IFN-beta were detected in pleural fluid after the first dose; however, only minimal levels were seen after the second dose of vector. Lack of expression correlated with the rapid induction of neutralizing Ad antibodies (Nabs). Antibody responses against tumor antigens were induced in most patients. At 2 months, modified RECIST responses were as follows: one partial response, two stable disease, nine progressive disease, and two nonmeasurable disease. One patient died after 1 month. By PET scanning, 2 patients had mixed responses and 11 had stable disease. There were seven patients with survival times longer than 18 months. This approach was safe, induced immune responses and disease stability. However, rapid development of Nabs prevented effective gene transfer after the second dose, even with a dose interval as short as 7 days.

Pre-existing immunity and passive immunity to adenovirus 5 prevents toxicity caused by an oncolytic adenovirus vector in the Syrian hamster model

We have used Syrian hamsters to examine the role of pre-existing immunity to adenovirus (Ad) 5 in the toxicity of the oncolytic Ad vector INGN 007. Groups of hamsters were or were not immunized with Ad5. Half the hamsters were immunosuppressed using cyclophosphamide (CP), then injected intravenously (i.v.) with 3x the maximum tolerated dose (MTD) of INGN 007 (in immunocompetent hamsters), and toxicity and vector replication in the liver were quantitated. In nonimmunized immunocompetent hamsters, toxicity was observed early but the hamsters recovered by day 6 after vector injection. In nonimmunized immunosuppressed hamsters, the vector was lethal by 3 days. Pre-existing neutralizing antibody (NAb) prevented liver infection and hepatotoxicity in both immunocompetent and immunosuppressed hamsters. In another study, passive immunization of immunosuppressed hamsters 1 day before a lethal dose (1x MTD) of INGN 007 prevented liver infection and replication, but immunization 1 day after vector administration was barely effective. When immunosuppressed hamsters were passively immunized 1 day after injection of 1/3rd the MTD of INGN 007, then significant protection was observed against liver infection and toxicity. Therefore, serum NAb are sufficient to prevent oncolytic Ad vector liver infection and toxicity. We saw no evidence that pre-existing immunity was associated with increased vector toxicity.

Malignant pleural mesothelioma

Malignant pleural mesothelioma (MPM) is a deadly disease that occurs in 2,000 to 3,000 people each year in the United States. Although MPM is an extremely difficult disease to treat, with the median overall survival ranging between 9 and 17 months regardless of stage, there has been significant progress over the last few years that has reshaped the clinical landscape. This article will provide a comprehensive discussion of the latest developments in the treatment of MPM. We will provide an update of the major clinical trials that impact mesothelioma treatment in the resectable and unresectable settings, discuss the impact of novel therapeutics, and provide perspective on where the clinical research in mesothelioma is moving. In addition, there are controversial issues, such as the role of extrapleural pneumonectomy, adjuvant radiotherapy, and use of intensity-modulated radiotherapy versus hemithoracic therapy that will also be addressed in this manuscript.

Neoadjuvant and intrapleural therapies for malignant pleural mesothelioma

Historically, malignant pleural mesothelioma patients with potentially resectable disease have been treated with surgery and radiation alone. With improvements in systemic and intrapleural treatment options, a movement toward multi-modality therapy has become more common. Systemic treatment options largely consist of neoadjuvant chemotherapy with platinum doublets and most recently novel targeted agents, such as dasatinib. Intrapleural strategies have included injecting chemotherapy, chemotherapy with hyper thermic per fusion, gene therapy, and immunotherapy. The following review discusses the latest results in neoadjuvant and intrapleural therapies in malignant pleural mesothelioma.

Effect of preexisting immunity on oncolytic adenovirus vector INGN 007 antitumor efficacy in immunocompetent and immunosuppressed Syrian hamsters

Immune responses against adenovirus (Ad) vectors pose a possible concern for the outcome of treatment efficacy. To address the role of preexisting immunity in oncolytic Ad vector antitumor efficacy following intratumoral injection of vector as well as tumor-to-tissue spread of the vector, we employed the Syrian hamster model. These animals are immunocompetent, and their tumors and tissues are permissive for replication of Ad type 5 (Ad5). We used the adenovirus death protein-overexpressing Ad5-based vector INGN 007. Subcutaneous tumors were established in groups of hamsters that were or were not immunized with Ad5. Half of the hamsters in these groups were immunosuppressed with cyclophosphamide. For all groups, tumors injected with INGN 007 grew significantly more slowly than those injected with buffer. Under immunocompetent conditions, there was no significant effect of preexisting immunity on vector antitumor efficacy. Soon after the tumors in naïve animals were injected with vector, the hamsters developed neutralizing antibody (NAb) and the difference in NAb titers between the naïve and immunized groups diminished. Under immunosuppressed conditions, preexisting NAb did significantly reduce vector efficacy. Thus, NAb do reduce vector efficacy to some extent, but immunosuppression is required to observe the effect. Regarding vector toxicity, there was spillover of vector from the tumor to the liver and lungs in naïve immunocompetent hamsters, and this was nearly eliminated in the immunized hamsters. Thus, preexisting immunity to Ad5 does not affect INGN 007 antitumor efficacy following intratumoral injection, but immunity prevents vector spillover from the tumor to the liver and lungs.