Evaluation of twenty human adenoviral types and one infectivity-enhanced adenovirus for the therapy of soft tissue sarcoma

Superior infectivity of the fiber chimeric oncolytic adenoviruses Ad5/35 and Ad5/3 over Ad5-delta-24-RGD in primary glioma cultures

Ad5-delta-24-RGD is currently the most clinically advanced recombinant adenovirus (rAd) for glioma therapy. We constructed a panel of fiber-modified rAds (Ad5RGD, Ad5/3, Ad5/35, Ad5/3RGD, and Ad5/35RGD, all harboring the delta-24 modification) and compared their infectivity, replication, reproduction, and cytolytic efficacy in human and rodent glioma cell lines and short-term cultures from primary gliomas. In human cells, both Ad5/35-delta-24 and Ad5/3-delta-24 displayed superior infectivity and cytolytic efficacy over Ad5-delta-24-RGD, while Ad5/3-delta-24-RGD and Ad5/35-delta-24-RGD did not show further improvements in efficacy. The expression of the adenoviral receptors/coreceptors CAR, DSG2, and CD46 and the integrins αVβ3/αVβ5 did not predict the relative cytolytic efficacy of the fiber-modified rAds. The cytotoxicity of the fiber-modified rAds in human primary normal cultures of different origins and in primary glioma cultures was comparable, indicating that the delta-24 modification did not confer tumor cell selectivity. We also revealed that CT-2A and GL261 glioma cells might be used as murine cell models for the fiber chimeric rAds in vitro and in vivo. In GL261 tumor-bearing mice, Ad5/35-delta-24, armed with the immune costimulator OX40L as the E2A/DBP-p2A-mOX40L fusion, produced long-term survivors, which were able to reject tumor cells upon rechallenge. Our data underscore the potential of local Ad5/35-delta-24-based immunovirotherapy for glioblastoma treatment.

ML-AdVInfect: A Machine-Learning Based Adenoviral Infection Predictor

Adenoviruses (AdVs) constitute a diverse family with many pathogenic types that infect a broad range of hosts. Understanding the pathogenesis of adenoviral infections is not only clinically relevant but also important to elucidate the potential use of AdVs as vectors in therapeutic applications. For an adenoviral infection to occur, attachment of the viral ligand to a cellular receptor on the host organism is a prerequisite and, in this sense, it is a criterion to decide whether an adenoviral infection can potentially happen. The interaction between any virus and its corresponding host organism is a specific kind of protein-protein interaction (PPI) and several experimental techniques, including high-throughput methods are being used in exploring such interactions. As a result, there has been accumulating data on virus-host interactions including a significant portion reported at publicly available bioinformatics resources. There is not, however, a computational model to integrate and interpret the existing data to draw out concise decisions, such as whether an infection happens or not. In this study, accepting the cellular entry of AdV as a decisive parameter for infectivity, we have developed a machine learning, more precisely support vector machine (SVM), based methodology to predict whether adenoviral infection can take place in a given host. For this purpose, we used the sequence data of the known receptors of AdVs, we identified sets of adenoviral ligands and their respective host species, and eventually, we have constructed a comprehensive adenovirus–host interaction dataset. Then, we committed interaction predictions through publicly available virus-host PPI tools and constructed an AdV infection predictor model using SVM with RBF kernel, with the overall sensitivity, specificity, and AUC of 0.88 ± 0.011, 0.83 ± 0.064, and 0.86 ± 0.030, respectively. ML-AdVInfect is the first of its kind as an effective predictor to screen the infection capacity along with anticipating any cross-species shifts. We anticipate our approach led to ML-AdVInfect can be adapted in making predictions for other viral infections.

Spectrum-Wide Exploration of Human Adenoviruses for Breast Cancer Therapy

Oncolytic adenoviruses (Ads) are promising tools for cancer therapeutics. However, most Ad-based therapies utilize Ad type 5 (Ad5), which displays unsatisfying efficiency in clinical trials, partly due to the low expression levels of its primary coxsackievirus and adenovirus receptor (CAR) on tumor cells. Since the efficacy of virotherapy strongly relies on efficient transduction of targeted tumor cells, initial screening of a broad range of viral agents to identify the most effective vehicles is essential. Using a novel Ad library consisting of numerous human Ads representing known Ad species, we evaluated the transduction efficiencies in four breast cancer (BC) cell lines. For each cell line over 20 Ad types were screened in a high-throughput manner based on reporter assays. Ad types featuring high transduction efficiencies were further investigated with respect to the percentage of transgene-positive cells and efficiencies of cellular entry in individual cell lines. Additionally, oncolytic assay was performed to test tumor cell lysis efficacy of selected Ad types. We found that all analyzed BC cell lines show low expression levels of CAR, while alternative receptors such as CD46, DSG-2, and integrins were also detected. We identified Ad3, Ad35, Ad37, and Ad52 as potential candidates for BC virotherapy.

Expanding the Spectrum of Adenoviral Vectors for Cancer Therapy

Adenoviral vectors (AdVs) have attracted much attention in the fields of vaccine development and treatment for diseases such as genetic disorders and cancer. In this review, we discuss the utility of AdVs in cancer therapies. In recent years, AdVs were modified as oncolytic AdVs (OAs) that possess the characteristics of cancer cell-specific replication and killing. Different carriers such as diverse cells and extracellular vesicles are being explored for delivering OAs into cancer sites after systemic administration. In addition, there are also various strategies to improve cancer-specific replication of OAs, mainly through modifying the early region 1 (E1) of the virus genome. It has been documented that oncolytic viruses (OVs) function through stimulating the immune system, resulting in the inhibition of cancer progression and, in combination with classical immune modulators, the anti-cancer effect of OAs can be even further enforced. To enhance the cancer treatment efficacy, OAs are also combined with other standard treatments, including surgery, chemotherapy and radiotherapy. Adenovirus type 5 (Ad5) has mainly been explored to develop vectors for cancer treatment with different modulations. Only a limited number of the more than 100 identified AdV types were converted into OAs and, therefore, the construction of an adenovirus library for the screening of potential novel OA candidates is essential. Here, we provide a state-of-the-art overview of currently performed and completed clinic trials with OAs and an adenovirus library, providing novel possibilities for developing innovative adenoviral vectors for cancer treatment.

Oncolytic adenovirus Ad657 for systemic virotherapy against prostate cancer

Background

Human species C adenovirus serotype 5 (Ad5) is the archetype oncolytic adenovirus and has been used in the vast majority of preclinical and clinical tests. While Ad5 can be robust, species C Ad6 has lower seroprevalence, side effects, and appears to be more potent as a systemic therapy against a number of tumors than Ad5. Historically, there have only been four species C human adenoviruses: serotypes 1, 2, 5, and 6. More recently a new species C adenovirus, Ad57, was identified. Ad57 is most similar to Ad6 with virtually all variation in their capsid proteins occurring in the hypervariable regions (HVRs) of their hexon proteins. Most adenovirus neutralizing antibodies target the HVRs on adenoviruses. This led us to replace the hexon HVRs in Ad6 with those from Ad57 to create a new virus called Ad657 and explore this novel species C platform’s utility as an oncolytic virus.

Methods

The HVR region from Ad57 was synthesized and used to replace the Ad6 HVR region by homologous recombination in bacteria generating a new viral platform that we call Ad657. Replication-competent Ad5, Ad6, and Ad657 were compared in vitro and in vivo for liver damage and oncolytic efficacy against prostate cancers after single intravenous treatment in mice.

Results

Ad5, Ad6, and Ad657 had similar in vitro oncolytic activity against human prostate cancer cells. Ad5 provoked the highest level of liver toxicity after intravenous injection and Ad657 caused the least damage in mice. Previous data demonstrated that Ad6 was superior to Ad5 at killing distant subcutaneous prostate cancer tumors in mouse models after a intravenous injection. Given this, Ad657 was compared to the Ad6 benchmark virus by single intravenous injection into mice bearing subcutaneous human DU145 prostate cancers. Under these conditions, Ad657 first infected the liver and then reached distant tumors. Both Ad6 and Ad657 mediated significant delays in tumor growth and extension of survival with Ad6 mediating higher efficacy.

Conclusions

These data suggest that Ad657 may have utility as a local or systemic oncolytic virotherapy for prostate cancers. These data also lay the foundation for serotype-switching with oncolytic species C Ads.

The current landscape of early drug development for patients with sarcoma in the immunotherapy era

Immunotherapy has changed the treatment paradigm of melanoma and other malignancies. Recently, trials of checkpoint inhibition in sarcomas have been far from outstanding, although specific sarcoma subtypes appear to benefit from these novel therapies. The next steps involve combining immune checkpoint inhibition with classic cancer therapies in order to increase immunogenicity and also potentially complex immunotherapy techniques such as adoptive cell therapy. Currently, numerous clinical trials are exploring different immunotherapies in the sarcomas. Herein, we describe some of the preclinical and clinical data that have laid the groundwork for the use of immunotherapies in sarcomas, as well as the current and future studies that could make immunotherapy a therapeutic option for patients with sarcoma.

Complete replication-competent adenovirus 11p vectors with E1 or E3 insertions show improved heat stability

Conventional adenovirus vectors harboring E1 or E3 deletions followed by the insertion of an exogenous gene show considerably reduced virion stability. Here, we report strategies to generate complete replication-competent Ad11p(RCAd11p) vectors that overcome the above disadvantage. A GFP cassette was successfully introduced either upstream of E1A or in the E3A region. The resulting vectors showed high expression levels of the hexon and E1genes and also strongly induced the cytopathic effect in targeted cells. When harboring oversized genomes, the RCAd11pE1 and RCAd11pE3 vectors showed significantly improved heat stability in comparison to Ad11pwt;of the three, RCAd11pE3 was the most tolerant to heat treatment. Electron microscopy showed that RCAd11pE3, RCAd11pE1, Ad11pwt, and Ad11pE1 Delmanifested dominant, moderate, minimum, or no full virus particles after heat treatment at 47°C for 5h. Our results demonstrated that both genome size and the insertion site in the viral genome affect virion stability.

Evaluation of polymer shielding for adenovirus serotype 6 (Ad6) for systemic virotherapy against human prostate cancers

Oncolytic viruses hold promise as “self-amplifying” cancer therapies wherein a virally killed cell can produce thousands of new viral “drugs” that can kill more cancer cells. Adenoviruses (Ads) are one family of oncolytic viruses. Most human studies have used human Ad serotype 5 (Ad5). Unfortunately, most patients are already immune to Ad5 increasing the likelihood that the agent will be neutralized if used as a cancer therapy. In this work, lower seroprevalence Ad6 was tested as a systemic therapy for prostate cancer. Ad5 and Ad6 were injected intravenously a single time in nude mice bearing human prostate tumors, and toxicity and efficacy were assessed. Ad6 was chemically shielded with polyethylene glycol (PEG) to test if this would further improve its pharmacology. Ad6 produced 30-fold lower liver damage and less toxicity than Ad5. Ad6 significantly repressed the growth of androgen-resistant human DU145 prostate tumors and androgen-sensitive LNCaP tumors after single intravenous injection. PEGylation did not change virus distribution, but blunted liver damage and cytokine production by Ad6. PEGylated Ad6 eradicated LNCaP tumors and maintained body mass, but lost potency against the more challenging DU145 tumors. These and other data suggest that low seroprevalent Ad6 has better efficacy and safety than the benchmark oncolytic virus Ad5 for systemic therapy of prostate cancer. These data also indicate that PEGylation may improve Ad6 safety, but that this shielding may reduce oncolytic efficacy after intravenous treatment.

Enhanced antitumor efficacy of fiber-modified, midkine promoter-regulated oncolytic adenovirus in human malignant mesothelioma

Oncolytic virotherapy using adenoviruses has potential for therapeutic benefits in malignant mesothelioma. However, the downregulation of coxsackie virus/adenovirus receptor (CAR) expression is frequently a critical rate-limiting factor that impedes the effectiveness of adenovirus serotype 5 (Ad5)-based vectors in many cancer types. We evaluated CAR (Ad5 receptor) and CD46 (adenovirus serotype 35 [Ad35] receptor) expression in six human malignant mesothelioma cell lines. Very low CAR expression was observed in MSTO-211H and NCI-H2052 cells, whereas the other cell lines showed strong expression. In contrast, CD46 was highly expressed in all mesothelioma cell lines. On this basis, we replaced the CAR binding sequence of Ad5 with the CD46 binding sequence of Ad35 in the replication-defective adenoviruses and the tumor-specific midkine promoter-regulated oncolytic adenoviruses. By this fiber modification, the infectivity, virus progeny production, and in vitro cytocidal effects of the adenoviruses were significantly enhanced in low CAR-expressing MSTO-211H and NCI-H2052 cells, also resulting in similar or even higher levels in high CAR-expressing mesothelioma cell lines. In MSTO-211H xenograft models, the fiber-modified oncolytic adenovirus significantly enhanced antitumor effect compared to its equivalent Ad5-based vector. Our data demonstrate that Ad35 fiber modification of binding tropism in a midkine promoter-regulated oncolytic Ad5 vector confers transductional targeting to oncolytic adenoviruses, thereby facilitating more effective treatment of malignant mesothelioma.

Progress of oncolytic viruses in sarcomas

Oncolytic virotherapy has shown exciting promise for the treatment of many types of solid tumors. Pediatric sarcomas are an aggressive type of pediatric malignancy known to show limited responsiveness to current therapies, leading to unacceptably high morbidity and mortality. Oncolytic viruses have only recently been used for the treatment of this challenging cancer, and results have been encouraging. Five clinical trials are currently open evaluating the use of oncolytic viruses in pediatric malignancies. Advances in genetic engineering of the viruses include improving the ability of the virus to infect tumor cells, engineering the virus with transgenes which improve the virus' ability to kill tumor cells and manipulating the virus to enhance concomitantly administered therapies. Further understanding of the antiviral immune response and a viral induced anti-tumor immune response will permit a maximization of oncolytic virotherapy.

Mining the adenovirus virome for oncolytics against multiple solid tumor types

Although there are 55 serotypes of adenovirus (Ad) that infect humans, Ad serotype 5 (Ad5) is the most widely studied because of the availability of commercial kits for its genetic manipulation. In fact, engineered Ad 5 is currently being used in all of the 87 global clinical trials utilizing Ad for the treatment of cancer. Unfortunately, Ad5 is one of the most seroprevalent serotypes, meaning that this virus has to confront additional immunological barriers to be effective in Ad5-immune patients. In this work, we compare Ad5 to 13 other adenoviral serotypes from species B, C, D and E for oncolytic potential in both immunodeficient mouse and immunocompetent hamster models. Our results indicate that species D Ads are not effective oncolytics against most solid tumors. Conversely, lower seroprevalent Ad6 and Ad11 had anti-cancer activity comparable to Ad5. This work strongly supports the consideration of Ad6-based oncolytic therapies for the treatment of breast, ovarian, kidney and liver tumors.

Species D adenoviruses as oncolytics against B-cell cancers

PURPOSE

Oncolytic viruses are self-amplifying anticancer agents that make use of the natural ability of viruses to kill cells. Adenovirus serotype 5 (Ad5) has been extensively tested against solid cancers, but less so against B-cell cancers because these cells do not generally express the coxsackie and adenoviral receptor (CAR). To determine whether other adenoviruses might have better potency, we "mined" the adenovirus virome of 55 serotypes for viruses that could kill B-cell cancers.

EXPERIMENTAL DESIGN

Fifteen adenoviruses selected to represent Ad species B, C, D, E, and F were tested in vitro against cell lines and primary patient B-cell cancers for their ability to infect, replicate in, and kill these cells. Select viruses were also tested against B-cell cancer xenografts in immunodeficient mice.

RESULTS

Species D adenoviruses mediated most robust killing against a range of B-cell cancer cell lines, against primary patient marginal zone lymphoma cells, and against primary patient CD138+ myeloma cells in vitro. When injected into xenografts in vivo, single treatment with select species D viruses Ad26 and Ad45 delayed lymphoma growth.

CONCLUSIONS

Relatively unstudied species D adenoviruses have a unique ability to infect and replicate in B-cell cancers as compared with other adenovirus species. These data suggest these viruses have unique biology in B cells and support translation of novel species D adenoviruses as oncolytics against B-cell cancers.

Increased antitumor capability of fiber-modified adenoviral vector armed with TRAIL against bladder cancers

Adenoviral vectors are widely used for cancer therapy and show a tumor-suppressing effect. However, bladder cancers are found to be resistant against infection of Ad5-derived adenoviral vector, limiting the application of the existing strategy of gene therapy. Therefore, efforts to develop novel types of adenoviral vector aimed for improving the viral infection and enhancing expression level of tumor-inhibiting transgene is urgently required. We constructed a 5/35 fiber-modified E1A-deleted adenoviral vector armed with TRAIL gene. Its ability to express this gene for inhibition of bladder cancer cell growth was investigated in our work. The results showed that this modification in fiber region facilitates adenoviral infection to bladder cancer, perhaps due to high expression of CD46 on target cell surface. Subsequently, we found an enhanced expression level of TRAIL mediated by 5/35 fiber-modified adenoviral vectors in bladder cancer cells, leading to an increased tumor-inhibiting capability of 5/35 adenoviral vector against bladder cancer cells. Consistently, growth of xenograft tumors in mice was also effectively inhibited by 5/35 fiber-modified vector-mediated gene therapy strategy. The 5/35 fiber-modified adenoviral vector-based gene transfer shows an improved efficacy against bladder cancers. The application of this novel gene therapy vector may benefit the patients in clinical bladder cancer treatment.

5/35 fiber-modified conditionally replicative adenovirus armed with p53 shows increased tumor-suppressing capacity to breast cancer cells

Conditionally replicative adenoviruses (CRAds) are widely used for cancer biotherapy and show a significant growth-suppressing effect on many types of cancer. However, it was reported that breast cancer was highly resistant to the infection of traditionally used adenovirus of serotype 5 (Ad5)-based CRAds. Although partial substitution of the fiber protein of replication-deficient Ad5 with that of adenovirus of serotype 35 (Ad35) facilitated infection of breast cancer cells by adenoviral vectors, it is still unknown whether this modification can improve CRAds in their tumor-eliminating capacity. We generated a 5/35 fiber-modified CRAd with a p53 cDNA construct and investigated whether this alteration in fiber region can make CRAds suppress the growth of breast cancer more effectively. Our data reinforced the proposal that 5/35-modified fiber conferred higher adenovirus infectivity for breast cancer cells than natural Ad5 fiber. Interestingly, 5/35 fiber-modified CRAd replicated more efficiently in breast cancer cells than Ad5-based CRAd. We also found 5/35 fiber-modified CRAd mediated higher expression of p53 in breast cancer cells. In vitro, 5/35 fiber-modified CRAd eliminated breast cancer cells more efficiently. Growth of xenograft tumors in nude mice was also significantly retarded by 5/35 fiber-modified CRAd. The 5/35 fiber-modified CRAd suppressed the growth of breast cancer cells more effectively than Ad5-based CRAd, both in vitro and in vivo. Thus CRAd with 5/35 hybrid fiber may be a promising vector for breast cancer treatment.

Current issues and future directions of oncolytic adenoviruses

Oncolytic adenoviruses (Ads) constitute a promising new class of anticancer agent. They are based on the well-studied adenoviral vector system, which lends itself to concept-driven design to generate oncolytic variants. The first oncolytic Ad was approved as a drug in China in 2005, although clinical efficacy observed in human trials has failed to reach the high expectations that were based on studies in animal models. Current obstacles to the full realization of efficacy of this class of anticancer agent include (i) limited efficiency of infection and specific replication in tumor cells, (ii) limited vector spread within the tumor, (iii) imperfect animal models and methods of in vivo imaging, and (iv) an incomplete understanding of the interaction of these agents with the host. In this review, we discuss recent advances in the field of oncolytic Ads and potential ways to overcome current obstacles to their clinical application and efficacy.

Phylogeny and primary structure analysis of fiber shafts of all human adenovirus types for rational design of adenoviral gene-therapy vectors

The fiber shaft of human adenoviruses (HAdVs) is essential for bringing the penton base into proximity to the secondary cellular receptor. Fiber shaft sequences of all 53 HAdV types were studied. Phylogeny of the fiber shaft revealed clustering corresponding to the HAdV species concept. An intraspecies recombination hot spot was found at the shaft/knob boundary, a highly conserved sequence stretch. For example, HAdV-D20 clustered with HAdV-D23 in the fiber shaft, but with HAdV-D47 in the fiber knob. Although all shafts exhibited the typical pseudorepeats, amino acid sequence identity was found to be as high as 92 % (interspecies) and 54 % (intraspecies). In contrast to a previous study, a flexibility motif (KXGGLXFD/N) was found in eight HAdV-D types, whereas the putative heparan sulfate-binding site (KKTK) was only found in species HAdV-C. Our results suggest that pseudotyping of gene-therapy vectors at the shaft/knob boundary is feasible, but that flexibility data of shafts should be considered.

Vector therapies for malignant glioma: shifting the clinical paradigm

BACKGROUND

Malignant glioma represents one of the most aggressive and devastating forms of human cancer. At present, there exists no successful treatment for this disease. Gene therapy, or vector therapy, has emerged as a viable experimental treatment method for intracranial malignancies.

OBJECTIVE

Vector therapy paradigms that have entered the clinical arena have shown adequate safety; however, the majority of the studies failed to observe significant clinical benefits. As such, researchers have refocused their efforts on developing novel vectors as well as new delivery methods to enhance the therapeutic effect of a particular vector. In this review, we discuss common vector therapy approaches used in clinical trials, their drawbacks and potential ways of overcoming these challenges.

METHODS

We focus on the experimental evaluation of cell-based vector therapies and adenoviral and herpes simplex virus type 1 vectors in the treatment of malignant glioma.

CONCLUSION

Vector therapy remains a promising treatment strategy for malignant glioma. Although significant questions remain to be answered, early clinical data suggest safety of this approach and future studies will likely address the efficacy of the proposed therapy.

Improved glioblastoma treatment with Ad5/35 fiber chimeric conditionally replicating adenoviruses

Adenovirus type 5 (Ad5)-based vectors have been used in clinical trials for glioblastoma treatment, but the capacity of Ad5 to infect human glioma cells was questioned. Seeking to improve the adenovirus transduction, we tested four Ad5-based vectors differing only in their fiber gene on permanent and short-term cultures of glioblastoma cells. A wild-type fiber Ad5 vector (Ad5.Luc) was compared to an RGD integrin-binding motif-containing fiber adenovirus (AdlucRGD) and the two fiber chimeras Ad5/3 and Ad5/35, with vector binding redirected to the Ad3 or Ad35 receptor, respectively. Compared to Ad5, the transduction of the tested short-term glioblastoma cultures with the vector Ad5/35.Luc, AdlucRGD and Ad5/3.Luc was enhanced by approximately 72%, approximately 13% and approximately 2%, respectively. To limit adenovirus spread, we aimed to develop conditionally replicative Ad5/35 vectors by targeting the expression of the essential E1 and E4 genes; in addition, some vectors had the E1Delta24 deletion. We analyzed eleven promoters for their activity in glioblastoma cells and determined the specificity of eight replicative adenovirus vectors in vitro. We evaluated the most promising vectors with E1/E4 under the control of the GFAP/Ki67 or E2F-1/COX-2 promoters, and the native Ad5 or the chimeric Ad5/35 fiber for their antineoplastic activity in a subcutaneous and intracranial glioblastoma xenograft model. Animals treated with the Ad5/35-based vectors showed significantly smaller tumors and longer survival than those treated with the homologous Ad5 vectors; no significant toxicity was observed in the intracranial model. Our data suggest that Ad5/35-based vectors are promising tools for glioblastoma treatment.

Evaluation of twenty-one human adenovirus types and one infectivity-enhanced adenovirus for the treatment of malignant melanoma

Advanced melanoma is associated with poor prognosis warranting the development of new therapeutics, such as oncolytic adenoviruses for immunovirotherapy. Since this approach critically depends on efficient transduction of targeted tumor cells, we screened a panel of 22 different adenovirus types for their internalization efficiency in melanoma cells. We demonstrated that the virions of Ad35, Ad38, and Ad3 have significantly higher internalization efficiency in melanoma cells than Ad5, so far the only adenovirus type used in clinical trials for melanoma. Therefore, we developed a conditionally replication-competent Ad5-based vector with the Ad35 fiber shaft and knob domains (Ad5/35) and compared its therapeutic efficacy with the homologous vector carrying the native Ad5 fiber. To further enhance virotherapy, we combined the oncolytic adenovirus vectors with intratumoral expression of measles virus fusogenic membrane glycoproteins H and F (MV-H/F) and dacarbazine chemotherapy. In a human melanoma xenograft model, established from a short-term culture of primary melanoma cells, we demonstrated that the Ad5/35-based therapy had a significantly greater anti-neoplastic effect than the homologous Ad5-based therapy. Furthermore, the combination of virotherapy, intratumoral expression of MV-H/F, and chemotherapy was clearly superior to single- or double-agent therapy. In conclusion, Ad35-based vectors are promising for the treatment of melanoma.

Local and distant immune-mediated control of colon cancer growth with fusogenic membrane glycoproteins in combination with viral oncolysis

We evaluated whether the expression of measles virus fusogenic membrane glycoproteins H and F (MV-FMG), encoded by a herpes simplex virus type 1 (HSV-1) amplicon vector, can serve with or without viral oncolysis (G47Delta) and facultative irinotecan chemotherapy, alone or in combination with the monoclonal epidermal growth factor receptor (EGFR) inhibitory antibody cetuximab, as a platform for inducing tumor-specific immune responses against colon cancer. We demonstrated in vitro that MV-FMG expression in murine cells resulted in cell-cell fusion and synergistically enhanced the cytotoxicity of irinotecan alone or in combination with cetuximab. In a bilateral syngeneic subcutaneous MC38 and Colon26 tumor model in C57BL/6 and BALB/c mice we assessed both the effect on directly vector-treated tumors and the effect on contralateral, not directly vector-treated tumors. We demonstrated that the combination of three treatment components with or without cetuximab resulted in the best volume reduction of both directly vector-treated and not directly vector-treated tumors as well as pronounced infiltration of both tumor types with natural killer cells, macrophages, and T cells. T cells of these animals exhibited strong ex vivo cytotoxic activity against the tumor cells, indicating that the antineoplastic effect on untreated tumors was mediated by an antitumor immune response. Preexisting immunity against HSV-1 or measles virus had no detrimental effect on overall treatment efficacy. Our data indicate that MV-FMG expression in combination with viral oncolysis with or without clinically relevant chemotherapy for colon cancer treatment warrants further investigation.

Phylogenetic analysis and structural predictions of human adenovirus penton proteins as a basis for tissue-specific adenovirus vector design

The penton base is a major capsid protein of human adenoviruses (HAdV) which forms the vertices of the capsid and interacts with hexon and fiber protein. Two hypervariable loops of the penton are exposed on the capsid surface. Sequences of these and 300 adjacent amino acid residues of all 51 HAdV and closely related simian adenoviruses were studied. Adjacent sequences and predicted overall secondary structure were conserved. Phylogenetic analysis revealed clustering corresponding to the HAdV species and recombination events in the origin of HAdV prototypes. All HAdV except serotypes 40 and 41 of species F exhibited an integrin binding RGD motif in the second loop. The lengths of the loops (HVR1 and RGD loops) varied significantly between HAdV species with the longest RGD loop observed in species C and the longest HVR1 in species B. Long loops may permit the insertion of motifs that modify tissue tropism. Genetic analysis of HAdV prime strain p17'H30, a neutralization variant of HAdV-D17, indicated the significance of nonhexon neutralization epitopes for HAdV immune escape. Fourteen highly conserved motifs of the penton base were analyzed by site-directed mutagenesis of HAdV-D8 and tested for sustained induction of early cytopathic effects. Thus, three new motifs essential for penton base function were identified additionally to the RGD site, which interacts with a secondary cellular receptor responsible for internalization. Therefore, our penton primary structure data and secondary structure modeling in combination with the recently published fiber knob sequences may permit the rational design of tissue-specific adenoviral vectors.