Engineered expression of the Coxsackie B and adenovirus receptor (CAR) in human dendritic cells enhances recombinant adenovirus-mediated gene transfer

Understanding and improving cellular immunotherapies against cancer: From cell-manufacturing to tumor-immune models

The tumor microenvironment (TME) is shaped by dynamic metabolic and immune interactions between precancerous and cancerous tumor cells and stromal cells like epithelial cells, fibroblasts, endothelial cells, and hematopoietically-derived immune cells. The metabolic states of the TME, including the hypoxic and acidic niches, influence the immunosuppressive phenotypes of the stromal and immune cells, which confers resistance to both host-mediated tumor killing and therapeutics. Numerous in vitro TME platforms for studying immunotherapies, including cell therapies, are being developed. However, we do not yet understand which immune and stromal components are most critical and how much model complexity is needed to answer specific questions. In addition, scalable sourcing and quality-control of appropriate TME cells for reproducibly manufacturing these platforms remain challenging. In this regard, lessons from the manufacturing of immunomodulatory cell therapies could provide helpful guidance. Although immune cell therapies have shown unprecedented results in hematological cancers and hold promise in solid tumors, their manufacture poses significant scale, cost, and quality control challenges. This review first provides an overview of the in vivo TME, discussing the most influential cell populations in the tumor-immune landscape. Next, we summarize current approaches for cell therapies against cancers and the relevant manufacturing platforms. We then evaluate current immune-tumor models of the TME and immunotherapies, highlighting the complexity, architecture, function, and cell sources. Finally, we present the technical and fundamental knowledge gaps in both cell manufacturing systems and immune-TME models that must be addressed to elucidate the interactions between endogenous tumor immunity and exogenous engineered immunity.

Human species D adenovirus hexon capsid protein mediates cell entry through a direct interaction with CD46

Human adenovirus species D (HAdV-D) types are currently being explored as vaccine vectors for coronavirus disease 2019 (COVID-19) and other severe infectious diseases. The efficacy of such vector-based vaccines depends on functional interactions with receptors on host cells. Adenoviruses of different species are assumed to enter host cells mainly by interactions between the knob domain of the protruding fiber capsid protein and cellular receptors. Using a cell-based receptor-screening assay, we identified CD46 as a receptor for HAdV-D56. The function of CD46 was validated in infection experiments using cells lacking and overexpressing CD46, and by competition infection experiments using soluble CD46. Remarkably, unlike HAdV-B types that engage CD46 through interactions with the knob domain of the fiber protein, HAdV-D types infect host cells through a direct interaction between CD46 and the hexon protein. Soluble hexon proteins (but not fiber knob) inhibited HAdV-D56 infection, and surface plasmon analyses demonstrated that CD46 binds to HAdV-D hexon (but not fiber knob) proteins. Cryoelectron microscopy analysis of the HAdV-D56 virion-CD46 complex confirmed the interaction and showed that CD46 binds to the central cavity of hexon trimers. Finally, soluble CD46 inhibited infection by 16 out of 17 investigated HAdV-D types, suggesting that CD46 is an important receptor for a large group of adenoviruses. In conclusion, this study identifies a noncanonical entry mechanism used by human adenoviruses, which adds to the knowledge of adenovirus biology and can also be useful for development of adenovirus-based vaccine vectors.

Dendritic cells transfected with adenoviral vectors as vaccines

Dendritic cells (DCs) are critical to the initiation of a T-cell response. They constitute the most potent antigen-presenting cell (APC) endowed with the unique capacity to stimulate an antigen-specific T-cell responses by naïve T cells. Adenoviruses (Ad) have high transduction efficiency for many cell types including cells of hematopoietic origin independent of their mitotic status, and replication-defective Ad have demonstrated a safety profile clinically. Further, Ad vectors provide a high level of transgene expression, and Ad-transduced DCs can effectively present antigenic proteins. In this chapter, we outline a functionally closed, good manufacturing protocol for the differentiation of monocytes into DCs and transduction by Ad vectors. Basic functional and phenotypic release assays are provided, as well as contrasting research approaches for Ad-transduced DC-based vaccines.

Dendritic cell based PSMA immunotherapy for prostate cancer using a CD40-targeted adenovirus vector

Human prostate tumor vaccine and gene therapy trials using ex vivo methods to prime dendritic cells (DCs) with prostate specific membrane antigen (PSMA) have been somewhat successful, but to date the lengthy ex vivo manipulation of DCs has limited the widespread clinical utility of this approach. Our goal was to improve upon cancer vaccination with tumor antigens by delivering PSMA via a CD40-targeted adenovirus vector directly to DCs as an efficient means for activation and antigen presentation to T-cells. To test this approach, we developed a mouse model of prostate cancer by generating clonal derivatives of the mouse RM-1 prostate cancer cell line expressing human PSMA (RM-1-PSMA cells). To maximize antigen presentation in target cells, both MHC class I and TAP protein expression was induced in RM-1 cells by transduction with an Ad vector expressing interferon-gamma (Ad5-IFNγ). Administering DCs infected ex vivo with CD40-targeted Ad5-huPSMA, as well as direct intraperitoneal injection of the vector, resulted in high levels of tumor-specific CTL responses against RM-1-PSMA cells pretreated with Ad5-IFNγ as target cells. CD40 targeting significantly improved the therapeutic antitumor efficacy of Ad5-huPSMA encoding PSMA when combined with Ad5-IFNγ in the RM-1-PSMA model. These results suggest that a CD-targeted adenovirus delivering PSMA may be effective clinically for prostate cancer immunotherapy.

Modification of human embryonic stem cell-derived dendritic cells with mRNA for efficient antigen presentation and enhanced potency

AIM

Dendritic cell (DC)-based vaccines are designed to exploit the intrinsic capacity of these highly effective antigen presenting cells to prime and boost antigen-specific T-cell immune responses. Successful development of DC-based vaccines will be dependent on the ability to utilize and harness the full potential of these potent immune stimulatory cells. Recent advances to generate DCs derived from human embryonic stem cells (hESCs) that are suitable for clinical use represent an alternative strategy from conventional approaches of using patient-specific DCs. Although the differentiation of hESC-derived DCs in serum-free defined conditions has been established, the stimulatory potential of these hESC-derived DCs have not been fully evaluated.

METHODS

hESC-derived DCs were differentiated in serum-free defined culture conditions. The delivery of antigen into hESC-derived DCs was investigated using mRNA transfection and replication-deficient adenoviral vector transduction. hESC-derived DCs modified with antigen were evaluated for their capacity to stimulate antigen-specific T-cell responses with known HLA matching. Since IL-12 is a key cytokine that drives T-cell function, further enhancement of DC potency was evaluated by transfecting mRNA encoding the IL-12p70 protein into hESC-derived DCs.

RESULTS

The transfection of mRNA into hESC-derived DCs was effective for heterologous protein expression. The efficiency of adenoviral vector transduction into hESC-derived DCs was poor. These mRNA-transfected DCs were capable of stimulating human telomerase reverse transcriptase antigen-specific T cells composed of varying degrees of HLA matching. In addition, we observed the transfection of mRNA encoding IL-12p70 enhanced the T-cell stimulation potency of hESC-derived DCs.

CONCLUSION

These data provide support for the development and modification of hESC-derived DCs with mRNA as a potential strategy for the induction of T-cell-mediated immunity.

The roles of cell surface attachment molecules and coagulation Factor X in adenovirus 5-mediated gene transfer in pancreatic cancer cells

Transduction of 11 pancreatic cancer cell lines with a replication-deficient adenovirus 5 expressing enhanced green fluorescent protein (Ad5EGFP) was analyzed and variable EGFP levels were observed, ranging from <1% to ∼40% of cells transduced, depending on the cell line. Efficient Ad5EGFP transduction was associated mainly with higher levels of cell surface Coxsackie and adenovirus receptor (CAR) but not with expression of α(v)β(3) and α(v)β(5) integrins and was fiber dependent. Reduction of CAR by RNA interference resulted in a corresponding decrease in Ad5EGFP transduction. Pre-treatment of Ad5EGFP with blood coagulation Factor X increased virus entry even in the presence of low CAR levels generated by RNA interference, suggesting a potential alternative route of Ad5 entry into pancreatic cancer cells. Immunohistochemistry carried out on 188 pancreatic ductal adenocarcinomas and 68 matched controls showed that CAR was absent in 102 (54%) of adenocarcinomas, whereas moderate and strong staining was observed in 58 (31%) and 28 (15%) cases, respectively. Weak or absent CAR immunolabeling correlated with poor histological differentiation of pancreatic cancer. In normal tissue, strong immunolabeling was detected in islet cells and in the majority of inter- and intralobular pancreatic ducts.

Dendritic Cell Function After Gene Transfer with Adenovirus-calcium Phosphate Co-precipitates

Dendritic cells (DCs) are essential for initiating and directing antigen-specific T-cell responses. Genetic modification of DC is under study for cancer immunotherapy, vaccine development, and antigen-targeted immunosuppression. Adenovirus (Ad) type 5 (Ad5)-mediated gene transfer to mouse bone marrow DCs and human monocyte-derived DCs is inefficient because neither express the cognate high-affinity Ads receptor. We show that co-precipitating adenoviral vectors with calcium phosphate (CaPi) increased gene expression (2000-fold) and transduction efficiency (50-fold) in mouse DC, primarily owing to receptor-independent viral uptake. Moreover, Ad5:CaPi-treated DCs were activated to express the maturation surface molecules CD40 and CD86, and to secrete proinflammatory cytokines tumor necrosis factor-alpha and interleukin 6. However, neither DC transduction nor maturation was dependent on viral protein interactions with cell surface integrin. Ad5:CaPi also transduced human DC more efficiently than Ad5 alone, similar to a genetically modified vector (Ad5f35) targeted to the CD46 receptor. As such, this approach combines the efficiency of adenoviral-mediated endosomal escape and nuclear trafficking with the receptor independence of nonviral gene delivery. Importantly, CaPi co-precipitation could be used to functionally modify DC to activate and expand cytomegalovirus-specific memory cytotoxic T lymphocytes. This study identifies a simple technique to improve the efficacy of current Ad5 gene transfer, in support of clinical adoptive immunotherapy.

Antisense therapy for restenosis following percutaneous coronary intervention

Recent advances in vascular gene transfer have shown potential new treatment modalities for cardiovascular disease, particularly in the treatment of vascular restenosis. The antisense approach to inhibiting gene expression involves introducing oligonucleotides complementary to mRNA into cells in order to block any one of the following processes: uncoiling of DNA, transcription of DNA, export of RNA, DNA splicing, RNA stability, or RNA translation involved in the synthesis of proteins in cellular proliferation. The approach includes the use of antisense oligonucleotides, antisense mRNA, autocatalytic ribozymes, and the insertion of a section of DNA to form a triple helix. Proof of principle has been established that inhibition of several cellular proto-oncogenes, including DNA binding protein c-myb, non-muscle myosin heavy chain, PCNA proliferating-cell nuclear antigen, platelet-derived growth factor, basic fibroblast growth factor and c-myc, inhibits smooth muscle cell proliferation in vitro and in several animal models. The first clinical study demonstrated the safety and feasibility of local delivery of antisense in the treatment and prevention of restenosis; another randomised clinical trial (AVAIL) with local delivery of c-myc morpholino compound in patients with coronary artery disease demonstrated its long-term effect on reducing neointimal formation, as well as its safety. These preliminary findings from the small cohort of patients require confirmation in a larger trial utilising more sophisticated drug-eluting technologies.

Human CD46-transgenic mice in studies involving replication-incompetent adenoviral type 35 vectors

Wild-type strains of mice do not express CD46, a high-affinity receptor for human group B adenoviruses including type 35. Therefore, studies performed to date in mice using replication-incompetent Ad35 (rAd35) vaccine carriers may underestimate potency or result in altered vector distribution. Here, it is reported that CD46 transgenic mice (MYII-strain) express CD46 in all major organs and that it functions as a receptor for rAd35 vectors. Similar to monkeys and humans, MYII mice highly express CD46 in their lungs and kidneys and demonstrate low expression in muscle. Upon intravenous administration, rAd35 vector genomes as well as expression are detected in lungs of MYII mice, in contrast to wild-type littermates. Expression was predominantly detected in lung epithelial cells. Upon intramuscular administration, the initial level of luciferase expression is higher in MYII mice as compared with wild-type littermates, in spite of the fact that CD46 expression is low in muscle of MYII mice. The higher level of expression in muscle of MYII mice results in prolonged gene expression as assessed by CCD camera imaging for luciferase activity. Finally, a significant dose-sparing effect in MYII mice as compared with wild-type littermates on anti-SIVgag CD8+ T-cell induction following intramuscular vaccination with an rA35.SIVgag vaccine was observed. This dose-sparing effect was also observed when reinfusing dendritic cells derived from MYII mice after exposure to rAd35.SIVgag vaccine as compared with rAd35.SIVgag exposed dendritic cells from wild-type littermates. It was concluded that MYII mice represent an interesting preclinical model to evaluate potency and safety of rAd35 vectors.

Susceptibility of B lymphocytes to adenovirus type 5 infection is dependent upon both coxsackie–adenovirus receptor and αvβ5 integrin expression

Human lymphocytes are resistant to genetic modification, particularly from recombinant adenoviruses, thus hampering the analysis of gene function using adenoviral vectors. This study engineered an Epstein–Barr virus-transformed B-lymphoblastoid cell line permissive to adenovirus infection and elucidated key roles for both the coxsackie–adenovirus receptor and αvβ5 integrin in mediating entry of adenoviruses into these cells. The work identified a strategy for engineering B cells to become susceptible to adenovirus infection and showed that such a strategy could be useful for the introduction of genes to alter lymphoblastoid-cell gene expression.

Transient overexpression of κ and μ opioid receptors using recombinant adenovirus vectors

In order to study the trafficking and signal transduction mechanisms of the multiple opioid receptors, these receptors are expressed either transiently or stably in cell lines. Often, it is difficult to express receptors at a sufficiently high density to obtain reproducible results. To achieve a high density of receptors, replication-defective adenovirus (rAd5) vectors encoding the mu (MOR) and kappa (KOR) opioid receptors, both in their native form and as fusion proteins bearing the green fluorescent protein (GFP) at their C-terminus, were constructed. These vectors efficiently and reproducibly infected Chinese hamster ovary (CHO) cells that stably express the human coxsackie-adenovirus receptor (hCAR), with up to 90% of cells becoming infected at a low multiplicity of infection (MOI). Saturation receptor binding studies using mu- and kappa-selective agonists, [3H][D-Ala2, N-Me-Phe4, Gly5-ol]enkephalin (DAMGO) and [3H](5alpha7alpha,8beta)-(-)-N-methyl-N-(7-(1-pyrrolidinyl)-1-oxaspiro(4,5)dec-8-yl)benzeneacetamide (U69,593), respectively, and a nonselective antagonist, [3H]diprenorphine, revealed that rAd5-transduced cells expressed MOR and KOR for at least 3 days, at levels which exceeded those present on widely-used CHO sublines that stably express MOR or KOR. Expression levels were highest for the vectors encoding native MOR or KOR, and slightly reduced for the GFP fusion proteins. These findings demonstrate the feasibility of using rAd5 vectors to express opioid receptors at high densities, which may facilitate opioid receptor studies.

Efficient Transduction with Recombinant Adenovirus in EBV-transformed B Lymphoblastoid Cell Lines

The Epstein-Barr-transformed B lymphoblastoid cell lines, LCL, which express antigens, are potential antigen-presenting cells (APCs) for the induction of cytotoxic T lymphocytes in vitro. However, transfecting LCL with subsequent selection by antibiotics is notoriously difficult because the plating efficiencies of LCL are reported to be 1% or less. Therefore, this study investigated the optimal conditions for increasing the transduction efficiency of a recombinant adenovirus to LCL for use as a source of APCs. The transduction efficiencies were < 13% (SD +/- 2.13) at a multiplicity of infection (MOI) of 100, while it was increased to 28% (SD +/- 9.43) at an MOI of 1000. Moreover, its efficiencies to LCL that expressed the coxsackie adenovirus receptor were increased to 60% (SD +/- 6.35) at an MOI of 1000, and were further increased to 70% (SD +/- 4.56) when combined with the centrifugal method. The cationic liposome or anionic polymer had no effect on the transduction efficiency when compared to that of the centrifugal method. These results may be used as a convenient source of target cells for a CTL assay and/or autologous APCs for the induction of the in vitro CTL responses that are specific to viral and tumor antigens.

Targeting of adenovirus via genetic modification of the viral capsid combined with a protein bridge

A potential barrier to the development of genetically targeted adenovirus (Ad) vectors for cell-specific delivery of gene therapeutics lies in the fact that several types of targeting protein ligands require posttranslational modifications, such as the formation of disulfide bonds, which are not available to Ad capsid proteins due to their nuclear localization during assembly of the virion. To overcome this problem, we developed a new targeting strategy, which combines genetic modifications of the Ad capsid with a protein bridge approach, resulting in a vector-ligand targeting complex. The components of the complex associate by virtue of genetic modifications to both the Ad capsid and the targeting ligand. One component of this mechanism of association, the Fc-binding domain of Staphylococcus aureus protein A, is genetically incorporated into the Ad fiber protein. The ligand is comprised of a targeting component fused with the Fc domain of immunoglobulin, which serves as a docking moiety to bind to these genetically modified fibers during the formation of the Ad-ligand complex. The modular design of the ligand solves the problem of structural and biosynthetic compatibility with the Ad and thus facilitates targeting of the vector to a variety of cellular receptors. Our study shows that targeting ligands incorporating the Fc domain and either an anti-CD40 single-chain antibody or CD40L form stable complexes with protein A-modified Ad vectors, resulting in significant augmentation of gene delivery to CD40-positive target cells. Since this gene transfer is independent of the expression of the native Ad5 receptor by the target cells, this strategy results in the derivation of truly targeted Ad vectors suitable for tissue-specific gene therapy.

Viral vectors for dendritic cell-based immunotherapy

Dendritic cells (DCs) constitute a specialised system of antigen-presenting cells with a high capacity to induce and to modulate the immune response against microbial, tumour and self-antigens. New techniques to generate large amounts of DCs together with the molecular identification of human tumour-associated antigens (TAA) have opened new ways for antigen-specific cancer immunotherapies. DCs loaded either with TAA-derived MHC class I-specific synthetic peptides or with whole tumour cell preparations have been used in numerous clinical trials evaluating the efficacy of DCs in patients with cancer. However, the disadvantages of DCs pulsed with synthetic peptides from TAA include the uncertainty regarding the longevity of antigen presentation, the restriction by the patient's haplotype and the relatively low number of known MHC class I and in particular of MHC class II helper cell-related epitopes. Whole tumour cell preparations are difficult to standardise, and they depend on the availability of tumour cells. Thus the utilisation of viral vectors genetically modified to express TAA for the ex vivo transduction of DCs is an attractive alternative to achieve a MHC I- and MHC II-restricted presentation of tumoural antigens. To induce protective anti-tumoural immune response an increasing number of modified viral vectors have been used to transduce DCs. Although high transduction efficacies were reported for several viruses, analysis of the interaction of viral vectors with DCs has revealed several viral mechanisms that interfere with main functions of DCs, dampening somewhat the initial optimism in the field of DC transduction. However, promising results with different vectors have been achieved. In this review we summarise available data and discuss advantages and drawbacks of currently available vectors.

Gene transduction efficiency and maturation status in mouse bone marrow-derived dendritic cells infected with conventional or RGD fiber-mutant adenovirus vectors

Since dendritic cells (DCs) play a critical role in establishing antigen-specific adaptive immune responses, in the past several years, therapeutic strategies using genetically modified DCs against cancer and infectious diseases have attracted increasing attention. In the present study, we demonstrated that RGD fiber-mutant adenovirus vector (AdRGD) exhibited markedly superior gene transduction efficiency in mouse bone marrow-derived DCs (mBM-DCs) compared to conventional adenovirus vector (Ad). Likewise, this vector exhibited superior major histocompatibility complex class I-restricted presentation of antigen derived from the delivered gene in mBM-DCs. In order to investigate the effect of Ad-infection on the DC-differentiation process (maturation), we used three types of AdRGD and three conventional Ad to transduce mBM-DCs. These vectors carried either no transgene, LacZ gene, or gp100 gene. Infection by any of the Ad vectors enhanced the expression of MHC class II molecules in mBM-DCs. CD80, CD86, and CD40 expression and IL-12 production were more efficient in AdRGD-infected mBM-DCs than in conventional Ad-infected cells. Contrary to our expectations, endocytotic activity of mBM-DCs decreased only slightly upon Ad-infection, whereas antigen uptake by lipopolysaccharide (LPS)-driven mature mBM-DCs was significantly impaired. However, our reverse transcription-polymerase chain reaction analysis revealed that Ad-infection resulted in the upregulation of the chemokine receptor CCR7 and downregulation of CCR6 in mBM-DCs and LPS-stimulated cells. We, therefore, concluded that Ad-infection directly influenced DC-maturation, although the effects were milder than under LPS-stimulation. In addition, this change in the immunologic properties of DCs resulted primarily from an increase in the number of Ad-particles capable of invading the cells rather than from the expression of foreign genes. AdRGD-infection caused greater induction of maturation than conventional Ad-infection, irrespective of the type of transgene inserted.

Efficient adenovirus transduction of 3T3-L1 adipocytes stably expressing coxsackie-adenovirus receptor

3T3-L1 adipocytes have proven difficult to transfect with plasmid-encoded cDNAs or even infect with virally-derived cDNAs. We have developed and characterized a 3T3-L1 adipocyte cell line stably expressing the truncated receptor for coxsackievirus and adenovirus receptor (CAR) for its ability to be infected with adenoviruses at a low multiplicity of infection (m.o.i.). Using green fluorescent protein driven by the cytomegalovirus promoter in adenovirus fiber type 5 we compared infection efficiencies of CAR adipocytes versus the parental 3T3-L1 adipocytes. As assessed by immunofluorescence, CAR adipocytes were infected at approximately 100-fold greater efficiency than regular 3T3-L1 adipocytes. The efficiency of transduction for the CAR adipocytes was >90% at multiplicities of infection of 50 whereas standard adipocytes were poorly transduced even at an m.o.i. of 2000. Since many investigators studying insulin action use 3T3-L1 adipocytes, we compared CAR adipocytes versus regular adipocytes and showed that the two cell lines were similar with respect to insulin stimulation of insulin receptor, MAPK, and Akt phosphorylation and basal- and insulin-stimulated glucose transport. In addition, CAR adipocytes accumulated GLUT4 and SCD1 proteins during the adipogenesis program with the same time course as regular 3T3-L1 adipocytes. Lastly, CAR adipocytes produced and secreted the adipose-specific hormone Acrp30. These data suggest 3T3-L1CARDelta1 adipocytes are virtually indistinguishable from their parental cells, but demonstrate a significant advantage with improved efficiency of adenoviral transduction for gain or deletion of function studies.