Adenovirus types 11p and 35p show high binding efficiencies for committed hematopoietic cell lines and are infective to these cell lines

Intratumoral Delivery of an Adenoviral Vector Carrying the SOCS-1 Gene Enhances T-Cell-Mediated Antitumor Immunity By Suppressing PD-L1

Ovarian cancer is the leading cause of gynecologic cancer-related deaths and novel therapeutic strategies are required. Programmed cell death 1 and programmed cell death ligand 1 (PD-L1), which are key mediators of host immune tolerance, are associated with ovarian cancer progression. Recent evidence indicates the importance of IFNγ-induced PD-L1 for immune tolerance in ovarian cancer. This study aimed to reveal the therapeutic potential of suppressor of cytokine signaling 1 (SOCS-1), an endogenous inhibitor of the Janus kinase (JAK)-STAT signaling pathway, for the treatment of ovarian cancer. IHC assessment revealed that patients with ovarian cancer with high intratumoral STAT1 activation exhibited poor prognosis compared with patients with low STAT1 activation (P < 0.05). Stimulation of OVISE, OVTOKO, OV2944-HM-1 (HM-1), and CT26 cell lines with IFNγ induced STAT1 phosphorylation and PD-L1 expression. Adenovirus-mediated SOCS-1 gene delivery (AdSOCS-1) in HM-1 and CT26 cells in vitro potently inhibited IFNγ-induced STAT1 phosphorylation and PD-L1 upregulation, similar to the addition of JAK inhibitor I, but failed to inhibit their proliferation. Notably, intratumoral injection of AdSOCS-1, but not AdLacZ, significantly inhibited the tumor growth of HM-1 and CT26 cells subcutaneously transplanted in immunocompetent syngeneic mice. AdSOCS-1 reduced PD-L1 expression on tumors and restored the activation of tumor-infiltrating CD8⁺ T cells. Moreover, the antitumor effect of AdSOCS-1 was significantly attenuated by PD-L1 Fc-fusion protein administration in vivo, suggesting that the effect of AdSOCS-1 is mainly attributable to enhancement of tumor immunity. This study highlights the potential clinical utility of SOCS-1 as an immune checkpoint inhibitor. Mol Cancer Ther; 17(9); 1941-50. ©2018 AACR.

Pancreatic carcinoma-specific immunotherapy using novel tumor specific cytotoxic T cells

Pancreatic cancer represents one of the most lethal human cancers. Investigation of the effective targeting to the tumor cells is essential for both primary tumors and metastases. Tumor specific cytotoxic T lymphocytes (CTLs) have recently been considered to be the attractive vehicles for delivering therapeutic agents toward various tumor diseases. This study was to explore the distribution pattern of CTL carrying the lentiviral vectors with the characteristic of adenoviral E1 gene under the control of the cell activation-dependent CD40 ligand promoter (Lenti/hCD40L/E1AB). Following transduction with adenoviral particles containing chimeric type 5 and type 35 fiber proteins (Ad5/35-TRAIL), these CTLs produced infectious virus when exposed to SW1990 cells. We found that the novel CTL harboring Lenti/hCD40L/E1AB and Ad5/35-TRAIL inhibited pancreatic cancer cell growth and angiogenesis in vitro and in vivo. Furthermore, Ad5/35-TRAIL transduced CTL induced significant apoptosis in pancreatic carcinoma cell lines and upregulated IFN-gamma (IFN-γ) secretion of CTLs. Importantly, Ad5/35-TRAIL transduced CTLs had no inhibitory effect on normal cells. Thus, the novel CTLs may be safe and feasible for the development of gene therapy approaches to pancreatic carcinoma.

Targeting eradication of chronic myeloid leukemia using chimeric oncolytic adenovirus to drive IL-24 expression

Chronic myeloid leukemia (CML) is a clonal disorder in which cells of the myeloid lineage undergo massive clonal expansion as well as resistance to conventional chemotherapy. Gene therapy hold a great promise for treatment of malignancies based on the transfer of genetic material to the tissues. In this study, we explore whether chimeric oncolytic adenovirus-mediated transfer of human interleukin-24 (IL-24) gene induce the enhanced antitumor potency. Our results showed that chimeric oncolytic adenovirus carrying hIL-24 (AdCN205-11-IL-24) could produce high levels of hIL-24 in CML cancer cells, as compared with constructed double-regulated oncolytic adenovirus expressing hIL-24 (AdCN205-IL-24). AdCN205-11-IL-24 could specifically induce cytotoxocity to CML cancer cells, but little or no effect on normal cell lines. AdCN205-11-IL-24 exhibited remarkable anti-tumor activities and induce higher antitumor activity to CML cancer cells by inducing apoptosis in vitro. Our study may provides a potent and safe tool for CML gene therapy.

Potent Antitumor Activity Generated by a Novel Tumor Specific Cytotoxic T Cell

Hepatocellular carcinoma is one of the most common malignant neoplasms in the world and is the main cause of death in patients with liver cirrhosis. Surgical intervention is not suitable for majority of hepatocellular carcinoma. Investigation of the effective targeting to the tumor cells is essential for both primary tumors and metastases. Tumor specific cytotoxic T lymphocytes (CTL) have been considered to be the attractive vehicles for delivering therapeutic agents toward various tumor diseases. This study was to explore the distribution pattern of CTL carrying the lentiviral vectors with the characteristic of adenoviral E1 gene under the control of the cell activation-dependent CD40 ligand promoter (Lenti/hCD40L/E1AB). Following transduction with adenoviral vectors containing chimeric type 5 and type 35 fiber proteins (Ad5/35-TRAIL), these CTLs produced infectious virus when exposed to HepG2 cells. We assessed the therapeutic ability of CTLs using MTT, Western blot and colony formation assay. The novel CTL harboring Lenti/hCD40L/E1AB and Ad5/35-TRAIL caused proliferation inhibition and significant apoptosis in hepatocellular carcinoma cell lines. Thus, the novel CTL may be useful for the development of gene therapy approaches to hepatocellular carcinoma.

Human effector T cells derived from central memory cells rather than CD8(+)T cells modified by tumor-specific TCR gene transfer possess superior traits for adoptive immunotherapy

Adoptive cell therapy provides an attractive treatment of cancer, and our expanding capacity to target tumor antigens is driven by genetically engineered human T lymphocytes that express genes encoding tumor-specific T cell receptors (TCRs). The intrinsic properties of cultured T cells used for therapy were reported to have tremendous influences on their persistence and antitumor efficacy in vivo. In this study, we isolated CD8(+) central memory T cells from peripheral blood lymphocytes of healthy donors, and then transferred with the gene encoding TCR specific for tumor antigen using recombinant adenovirus vector Ad5F35-TRAV-TRBV. We found effector T cells derived from central memory T cells improved cell viability, maintained certain level of CD62L expression, and reacquired the CD62L(+)CD44(high) phenotype of central memory T cells after effector T cells differentiation. We then compared the antitumor reactivity of central memory T cells and CD8(+)T cells after TCR gene transferred. The results indicated that tumor-specific TCR gene being transferred to central memory T cells effectively increased the specific killing of antigen positive tumor cells and the expression of cytolytic granule protein. Furthermore, TCR gene transferred central memory T cells were more effective than TCR gene transferred CD8(+)T cells in CTL activity and effector cytokine secretion. These results implicated that isolating central memory T cells rather than CD8(+)T cells for insertion of gene encoding tumor-specific TCR may provide a superior tumor-reactive T cell population for adoptive transfer.

Intracardiac injection of a capsid-modified Ad5/35 results in decreased heart toxicity when compared to standard Ad5

BACKGROUND

Clinical gene therapy trials for cardiovascular diseases have demonstrated the crucial role of efficient gene delivery and transfection technologies in achieving clinically relevant results. We hypothesized that the use of tropism-modified adenoviruses would improve transduction efficacy and to this end we analyzed the transduction efficiency and toxicity of standard Ad5 and tropism-modified Ad5/35 in combination with ultrasound-guided intramyocardial gene delivery.

METHODS

Ultrasound-guided intracardiac injections were used to deliver 1 × 10(10) pfu/ml Ad5-lacZ and Ad5/35-lacZ vectors into mouse left ventricle wall. Since Ad5/35 uses human CD46 as its primary receptor, we used transgenic hCD46Ge mice expressing human CD46 at levels comparable to man. Mice were sacrificed 6 or 14 days post-injection and immunohistochemistry and X-gal staining were used to detect transgene and viral receptor expression. Virus-induced cardiac toxicity was evaluated by a pathologist.

RESULTS

The intramyocardial injection was well tolerated and both Ad5-lacZ and Ad5/35-lacZ were able to give robust transgene expression after a single injection. Interestingly, while Ad5-lacZ was able to generate greater transgene expression than Ad5/35-lacZ, it also evoked more severe tissue damage with large areas of interstitial inflammatory cell infiltration and myocyte necrosis.

CONCLUSIONS

Ultrasound-guided intramyocardial injection is an effective and safe way to deliver vectors to the heart. The observed severe tissue damage of Ad5-lacZ greatly undermines the efficient transgene expression and suggests that Ad5/35 capsid modification can result in safer adenoviral vectors for cardiovascular gene therapy, although at the cost of some vector transduction efficacy.

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

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

Adenovirus type 35, but not type 5, stimulates NK cell activation via plasmacytoid dendritic cells and TLR9 signaling

In hematopoietic stem cell transplant (HSCT) recipients, disseminated adenoviral infections during the first two months after HSCT can lead to severe complications and fatal outcome. Since NK cells are usually the first lymphocytes to reconstitute after HSCT and have been implicated in the clearance of adenovirus-infected cells, it was investigated whether NK cells are activated by adenovirus in vitro. Exposure of PBMC to human adenovirus type 5 (HAdV5) or HAdV35 resulted in the up-regulation of the activation marker CD69 on NK cells and enhanced the cytolytic activity of NK cells. HAdV5-induced NK cell activation relied on the contribution of T cells as the depletion of T cells from PBMC abolished NK cell activation. In contrast, NK cell activation in response to HAdV35 occurred in the absence of T cells. Plasmacytoid dendritic cells (pDC) were necessary and sufficient to mediate NK cell activation. HAdV35 induced significantly more interferon-α (IFN-α) production by pDC than HAdV5. The increased IFN-α production and NK cell activation correlated with a higher infection efficiency of viruses with the type 35 fiber. The IFN-α response of pDC was enhanced by the presence of NK cells, suggesting a reciprocal interaction between pDC and NK cells. Incubation with a TLR9 antagonist impaired the IFN-α production by pDC as well as NK cell activation, implying that TLR9 signaling is critically involved in the IFN-α response of pDC and NK cell activation after HAdV35 exposure. In conclusion, two human adenovirus serotypes from two different species differ considerably in their capacity to stimulate pDC and NK cells.

Adenovirus 11p downregulates CD46 early in infection

Adenovirus 11 prototype (Ad11p), belonging to species B, uses CD46 as an attachment receptor. CD46, a complement regulatory molecule, is expressed on all human nucleated cells. We show here that Ad11p virions downregulate CD46 on the surface of K562 cells as early as 5min p.i. Specific binding to CD46 by the Ad11p fiber knob was required to mediate downregulation. The complement regulatory factors CD55 and CD59 were also reduced to a significant extent as a consequence of Ad11p binding to K562 cells. In contrast, binding of Ad7p did not result in downregulation of CD46 early in infection. Thus, the presumed interaction between Ad7p and CD46 did not have the same consequences as the Ad11p-CD46 interaction, the latter virus (Ad11p) being a promising gene therapy vector candidate. These findings may lead to a better understanding of the pathogenesis of species B adenovirus infections.

The prevalence of antibodies to adenovirus serotype 5 in an adult Indian population and implications for adenovirus vector vaccines

In vivo gene delivery using human adenovirus serotype 5 (AdV5) vectors is being explored for vaccination purposes. The presence of anti-AdV5 antibodies in human serum arising from natural exposure to AdV5 can interfere potentially with and compromise the efficacy of rAdV5-based vaccine vectors. In this report, a collection of 114 sera from healthy adult Indian blood donors was analyzed for the presence of anti-AdV5 antibodies, using an AdV5 vector encoding the green fluorescent protein (GFP) to monitor the presence of anti-AdV5 neutralizing antibodies in human sera based on their ability to block virus entry into HeLa cells which express the Coxsackievirus-and-Adenovirus Receptor (CAR). In this assay all samples tested were positive for anti-AdV5 antibodies, with titers varying over a very wide range. It was also observed that these antibodies facilitated the uptake of the reporter AdV5 vector into the monocytic cell line U937 which does not express CAR, but expresses Fc receptors (FcRs) instead. These observations have implications for rAdV5-based vaccine development. J. Med. Virol. 82:407-414, 2010. (c) 2010 Wiley-Liss, Inc.

Dilated cardiomyopathy alters the expression patterns of CAR and other adenoviral receptors in human heart

Gene therapy trials for heart failure have demonstrated the key role of efficient gene transfer in achieving therapeutic efficacy. An attractive approach to improve adenoviral gene transfer is to use alternative virus serotypes with modified tropism. We performed a detailed analysis of cardiac expression of receptors for several adenovirus serotypes with a focus on differential expression of CAR and CD46, as adenoviruses targeting these receptors have been used in various applications. Explanted hearts from patients with DCM and healthy donors were analyzed using Q-RT-PCR, western blot and immunohistochemistry. Q-RT-PCR and Western analyses revealed robust expression of all receptors except CD80 in normal hearts with lower expression levels in DCM. Immunohistochemical analyses demonstrated that CD46 expression was somewhat higher than CAR both in normal and DCM hearts with highest levels of expression in intramyocardial coronary vessels. Total CAR expression was upregulated in DCM. Triple staining on these vessels demonstrated that both CAR and CD46 were confined to the subendothelial layer in normal hearts. The situation was clearly different in DCM, where both CAR and CD46 were expressed by endothelial cells. The induction of expression of CAR and CD46 by endothelial cells in DCM suggests that viruses targeting these receptors could more easily gain entry to heart cells after intravascular administration. This finding thus has potential implications for the development of targeted gene therapy for heart failure.

Development of fiber-substituted adenovirus vectors containing foreign peptides in the adenovirus serotype 35 fiber knob

Fiber-substituted adenovirus (Ad) vectors containing fibers of Ad serotype 35 (AdF35) efficiently transduce a variety of human cells because their receptor, human CD46, is ubiquitously expressed on almost all nucleated cells. However, the ubiquitous expression of CD46 might lead to unexpected transduction in untargeted organs. In this study, we developed fiber-modified AdF35 vectors with an integrin-binding Arg-Gly-Asn (RGD) peptide incorporated into the FG, HI or IJ loop, which have been identified as important regions for binding to CD46. Incorporation of foreign peptides into these loops does not inhibit trimerization of the fibers. In CD46-negative cells, fiber-mutant AdF35 vectors containing an RGD peptide in the FG or HI loop showed 6- to 30-fold higher transduction efficiencies in an RGD-peptide-dependent manner than the unmodified AdF35 vectors. In contrast, in CD46-positive cells, insertion of foreign peptides markedly reduced the transduction efficiencies of the AdF35 vectors, indicating that insertion of foreign peptides significantly inhibits binding to CD46. In particular, CD46-mediated transduction was completely diminished by insertion of foreign peptides into the HI loop. Our findings indicate that HI loop is the most suitable domain to mediate a foreign peptide-dependent and CD46-independent transduction by incorporation of foreign peptides into the Ad35 fiber knob.

[Development of a replication-incompetent adenovirus vector derived from subgroup B adenovirus serotype 35]

Properties of gene delivery vehicles, including gene transfer efficiencies and toxicities, are a key parameter for successful gene therapy. Among various types of gene delivery vehicles that have been developed so far, adenovirus (Ad) vectors have promising potentials as a vector for gene therapy because they can easily be grown to high titers and can efficiently deliver genes to both dividing and non-dividing cells. However, recent studies demonstrated some drawbacks of conventional Ad vectors, which are composed of subgroup C Ad serotype 5 (Ad5). First, Ad5 vectors poorly transduce cells lacking the primary receptor for Ad5, coxsackievirus and adenovirus receptor (CAR). Second, majority of adults have neutralizing antibodies to Ad5. In order to overcome these drawbacks, we developed a novel Ad vector which is fully composed of subgroup B Ad serotype 35 (Ad35). Ad35 vectors can infect a variety of human cells because the primary receptor for Ad35, CD46, is ubiquitously expressed in human cells. Furthermore, Ad35 vectors efficiently transduce in the presence of anti-Ad5 antibodies, and seroprevalence of Ad35 in adults is much lower than that of Ad5. In the current review, I introduce our recent work on development and evaluation of Ad35 vectors, and I also discuss the potential of Ad35 vectors as gene delivery vehicles.

Development and evaluation of a novel gene delivery vehicle composed of adenovirus serotype 35

The capacity of gene delivery vehicles is considered to be a critical factor determining the success of gene therapy. To date, various types of gene delivery vehicle have been developed. Among them, recombinant adeno-virus (Ad) vectors have potential that has favored their worldwide use in vitro and in vivo. Conventional Ad vectors are composed of subgroup C Ad serotype 5 (Ad5), although it has been clarified that the drawbacks of Ad5 vectors are a high seroprevalence of Ad5 in adults and low transduction efficiencies in cells lacking the primary receptor for Ad5, coxsackievirus and adenovirus receptor. To overcome these problems, we developed a novel Ad vector fully composed of Ad serotype 35 (Ad35). Ad35 vectors show a wide tropism for human cells because Ad35 binds to human CD46, which is ubiquitously expressed on almost all human cells, as a primary receptor. In addition, anti-Ad5 antibodies do not inhibit Ad35 vector-mediated transduction and the seroprevalence of Ad35 in adults is lower than that of Ad5. This paper reviews our studies on the development and evaluation of Ad35 vectors. Ad vectors derived from other Ad serotypes different from Ad5, including Ad35, are expected to be gene delivery vehicles alternative to conventional Ad5 vectors.

Structural variations in species B adenovirus fibers impact CD46 association

A majority of species B adenoviruses (Ads) use CD46 as their primary receptor; however, the precise mechanisms involved in the binding of different Ad types to CD46 have not been resolved. Although previous studies indicate close similarities between two members of species B2 Ads in their usage of CD46, our current investigations revealed a surprisingly low CD46 binding affinity of the species B1 Ad16 fiber knob (equilibrium dissociation constant of 437 nM). We determined the crystal structure of the Ad16 fiber knob and constructed a model of this protein in complex with CD46. A comparison of this model to that of the CD46-Ad11 complex revealed structural differences in the FG and IJ loops that are part of the CD46 binding site. An analysis of a panel of recombinant fiber knobs with mutations targeting these regions in Ad16 and Ad11 uncovered a major contribution of the FG loop on CD46 binding. Two extra residues in the FG loop of the Ad16 fiber significantly reduce receptor interaction. Although avidity effects permit the use of CD46 on host cells by Ad16, virus binding occurs with lower efficiency than with B2 Ad types. The longer FG loop of the Ad16 fiber knob also is shared by other species B1 Ad fibers and, thus, may contribute to the low CD46 binding efficiencies observed for these Ad types. Our findings provide a better understanding of how different Ad types associate with CD46 and could aid in the selection of specific Ad fibers for more efficient Ad gene delivery vectors.

Conservation of fiber structure and CD46 usage by subgroup B2 adenoviruses

Most subgroup B2 adenoviruses use CD46 as their primary receptor. Recent structural and mutagenesis studies suggested that Ad11 and Ad35 likely engage this receptor in a very similar fashion. However, no comparative studies assessing the cell-associated CD46 binding efficiencies of different Ad fibers have been performed. We solved the crystal structure of Ad35 fiber knob and constructed a model of the fiber knob complexed with CD46. Comparison of our model with that of Ad11-CD46 showed that despite a larger CD46-interacting region in the IJ loop of Ad11, the buried surface area was very similar, suggesting that both fiber knobs might exhibit similar binding. In support of this, cell based competition studies demonstrated almost identical binding efficiencies of Ad11 and Ad35 fibers to cell surface CD46. These findings shed further light on CD46 association by Ad and could impact the selection of novel Ad types for gene transfer.

Interaction of penton base Arg-Gly-Asp motifs with integrins is crucial for adenovirus serotype 35 vector transduction in human hematopoietic cells

Most subgroup B adenoviruses (Ads), including adenovirus (Ad) serotype 35 (Ad35), bind to human CD46 as a receptor; however, the infection processes of subgroup B Ads following attachment to CD46 remain to be elucidated. Subgroup B Ads possess Arg-Gly-Asp (RGD) motifs in the penton base, similarly to subgroup C Ad serotypes 2 and 5. In this study, we examined the role of penton base RGD motifs in Ad35 vector-mediated transduction in human hematopoietic cells. Inhibition of interaction between integrins and the RGD motifs by divalent cation chelation and a synthetic RGD peptide reduced the transduction efficiencies of Ad35 vectors; however, the amounts of cell-associated vector DNA of Ad35 vectors at 4 or 37 degrees C were not decreased by divalent cation chelation or the RGD peptide. Mutation of penton base RGD motifs reduced the transduction efficiencies of Ad35 vectors, although the amounts of cell-associated vector DNA of Ad35 vectors at 4 or 37 degrees C were not altered by mutation of penton base RGD motifs in Ad35 vectors. Furthermore, preincubation with several types of anti-integrin antibodies significantly inhibited Ad35 vector-mediated transduction. These results suggest that interaction between integrins and penton base RGD motifs plays a crucial role in Ad35 vector-mediated transduction in hematopoietic cells, probably in the post-internalization steps.

Intracellular trafficking of a fiber-modified adenovirus using lipid raft/caveolae endocytosis

Most adenoviral vectors (HAdvs) elaborated for gene therapy are derived from serotype 5 viruses that use clathrin-coated vesicle endocytosis for cell entry. However, it appears that adenoviral vectors are able to take advantage of lipid raft/caveolae endocytosis to infect cells. In vivo targeting of a therapeutic gene to specific cells by vector engineering has become a major focus of gene therapy research. Yet, modification of adenoviral tropism, especially fiber gene engineering, can induce deficient intracellular trafficking of the viral particle, with a shift in subcellular localization resulting in extensive exocytosis. In this study we demonstrate that uptake of a fiber-modified adenovirus using lipid raft/caveolae endocytosis leads to non-altered intracellular trafficking without endosomal retention. Moreover, activation of lipid raft structures by this vector leads to the formation of "mega-caveosomes". These results demonstrate that, by forcing adenoviruses to take advantage of a non-clathrin, non-classical endocytic pathway, it is possible to compensate for the deficiency in endosomolysis that is associated with the use of some of the fiber-modified adenoviral constructs. Moreover, it renders such vectors ideal candidates for infecting human coxsackie and adenoviruses receptor (hCAR) negative cells.

Highly efficient gene transfer into mobilized CD34+ hematopoietic cells using serotype-5 adenoviral vectors and BoosterExpress Reagent

OBJECTIVE

To optimize transduction efficiency of mobilized CD34(+) cells with serotype-5 adenoviruses (Ad5s), we investigated the activity of the chemical cocktail BoosterExpress Reagent in enhancing Ad5-mediated gene transfer into CD34(+) cells.

METHODS

Enriched CD34(+) cells were transduced with three different Ad5s at increasing multiplicity of infections (MOIs) in the presence and absence of BoosterExpress Reagent. Percentages of transduced cells and levels of transgene expression were quantified by flow cytometry. Propidium iodide staining and colony growth were used to assess the toxicity of the transduction protocol. Expression of adenovirus receptors was investigated by flow cytometry.

RESULTS

Irrespective of the Ad5 used, transduction with BoosterExpress Reagent using an MOI of 500 resulted in an average six- to seven-fold increase of transduction efficiencies and 1.5- to 2-fold increase of the levels of transgene expression, which could be detected up to 7 days post-transduction. Although BoosterExpress Reagent alone did not affect the plating efficiency of CD34(+) cells, adenovector transduction plus BoosterExpress Reagent significantly reduced the plating efficiency due to the marked increase of transduced cells. However, adenoviral transduction in the presence of BoosterExpress Reagent failed to significantly reduce the recovery of CD34(+) cells as compared with transduction in the absence of the compound. Coxsackievirus and adenovirus receptor as well as alpha(v)beta(3), alpha(v)beta(5), alpha(5), and beta(1) integrins were upregulated by BoosterExpress Reagent.

CONCLUSIONS

BoosterExpress Reagent allows high-levels of durable transgene expression, thus making CD34(+) cells a suitable target for Ad5-mediated gene transfer.

Chimeric adenovirus type 5/35 vector encoding SIV gag and HIV env genes affords protective immunity against the simian/human immunodeficiency virus in monkeys

Replication-defective adenovirus type 5 (Ad5) vector-based vaccines are widely known to induce strong immunity against immunodeficiency viruses. To exploit this immunogenicity while overcoming the potential problem of preexisting immunity against human adenoviruses type 5, we developed a recombinant chimeric adenovirus type 5 with type 35 fiber vector (rAd5/35). We initially produced a simian immunodeficiency virus (SIV) gag DNA plasmid (rDNA-Gag), a human immunodeficiency virus type 1 (HIV-1) 89.6 env DNA plasmid (rDNA-Env) and a recombinant Ad5/35 vector encoding the SIV gag and HIV env gene (rAd5/35-Gag and rAd5/35-Env). Prime-boost vaccination with rDNA-Gag and -Env followed by high doses of rAd5/35-Gag and -Env elicited higher levels of cellular immune responses than did rDNAs or rAd5/35s alone. When challenged with a pathogenic simian human immunodeficiency virus (SHIV), animals receiving a prime-boost regimen or rAd5/35s alone maintained a higher number of CD4(+) T cells and remarkably suppressed plasma viral RNA loads. These findings suggest the clinical promise of an rAd5/35 vector-based vaccine.

Preferential activation of Toll-like receptor nine by CD46-utilizing adenoviruses

Adenoviruses (Ads) are responsible for respiratory, ocular, and gastrointestinal illnesses in humans. While the majority of serotypes utilize coxsackievirus-adenovirus receptor (CAR) as their primary attachment receptor, subgroup B and subgroup D Ad37 serotypes use CD46. Given the propensity of Ad vectors to activate host immune responses, we sought to investigate their potential for type I interferon induction. We found that CD46 Ads were capable of alpha interferon (IFN-alpha) induction by peripheral blood mononuclear cells and that plasmacytoid dendritic cells (pDCs) were the principal producers of this cytokine. IFN-alpha induction correlated with the permissivity of pDCs to CD46- but not CAR-utilizing Ad serotypes. A role for Toll-like receptor 9 (TLR9) recognition of Ad was supported by the requirement for viral DNA and efficient endosomal acidification and by the ability of a TLR9-inhibitory oligonucleotide to attenuate IFN-alpha induction. Cell lines expressing TLR9 that are permissive to infection by both CAR- and CD46-utilizing serotypes showed a preferential induction of TLR9-mediated events by CD46-utilizing Ads. Specifically, the latter virus types induced higher levels of cytokine expression and NF-kappaB activation in HeLa cells than CAR-dependent Ad types, despite equivalent infection rates. Therefore, infectivity alone is not sufficient for TLR9 activation, but this activation instead is regulated by a specific receptor entry pathway. These data reveal a novel mode of host immune recognition of Ad with implications for Ad pathogenesis and for the use of unconventional Ad vectors for gene delivery and vaccine development.

[Characterization of adenovirus serotype 35 vectors using genetically modified animals and non-human primates]

Recombinant Adenovirus (Ad) vectors are considered to be a promising gene delivery vehicle of high utility because they are easy to construct, can be produced at high titers, and efficiently transduce various types of cells. Ad vectors commonly used in the world, including clinical trials, are composed of Ad serotype 5 (Ad5), which belongs to subgroup C. In recent years, however, it has become apparent that Ad5 vectors have some drawbacks, such as high seroprevalence of anti-Ad5 antibodies in adults and low transduction efficiencies of Ad5 vectors in cells lacking a primary receptor for Ad5, coxsackievirus and adenovirus receptor (CAR). To overcome these limitations of Ad5 vectors, we have developed a novel type of Ad vector, which is composed of Ad serotype 35 (Ad35), belonging to subgroup B. Ad35 vectors recognize human CD46, not CAR, as a cellular receptor for infection. Human CD46 is expressed in almost all of human cells, leading to a broad tropism of Ad35 vectors to human cells, in contrast, expression of rodent CD46 is limited to the testis. Therefore, in vivo transduction properties of Ad35 vectors are not appropriately evaluated in normal mice. In order to evaluate the in vivo transduction properties of Ad35 vectors, Ad35 vectors were applied to human CD46-transgenic mice and nonhuman primates, which express CD46 in a similar pattern to humans. The data obtained using CD46-transgenic mice and nonhuman primates would provide valuable information towards clinical applications of Ad35 vectors.

Members of adenovirus species B utilize CD80 and CD86 as cellular attachment receptors

Alternate serotypes of adenovirus (Ad), including Ads of species B, are being explored to circumvent the disadvantages of Ad serotype 5 gene delivery vectors. Whereas the majority of human Ads utilize the Coxsackievirus and adenovirus receptor (CAR), none of the Ad species B use CAR. Ad species B is further divided into two subspecies, B1 and B2, and utilizes at least two classes of receptors: common Ad species B receptors and B2 specific receptors. CD46 has been implicated as a B2-specific receptor. Ad serotype 3 (Ad3), a member of B1, utilizes CD80 and CD86 as cellular attachment receptors. The receptor-interacting Ad fiber-knob domain is highly homologous among species B Ads. We hypothesized that other members of Ad species B may utilize CD80 and CD86 as cellular attachment receptors. All tested species B members showed specific binding to cells expressing CD80 and CD86, and the Ad fiber-knob domain from both B1 and B2 Ad efficiently blocked CD80- and CD86-mediated infection of Ad3 vectors. Members of both B1 and B2 demonstrated CD80- and CD86-specific infection of CHO cells expressing CD80 and CD86. Therefore, all of the members of Ad species B utilize CD80 and CD86 for infection of cells.

Improved gene delivery to B lymphocytes using a modified adenovirus vector targeting CD21

Gene transfer by adenoviruses, which are widely used for gene therapy, may provide an alternative approach to treatment of several hematopoietic malignancies. However, a major limitation of adenovirus 5-based gene therapy lies in the natural tropism of the virus for the widely expressed hCAR receptor. The efficacy of adenoviral vectors could be improved if viral vectors that exhibit tissue-specific gene delivery were developed. For efficient gene transfer it is essential that every step from binding of virus to target cells to transgene expression is successfully accomplished. We developed a specific vector targeting the CD21 receptor, by inserting a CD21 binding sequence, derived from the EBV GP350/220 protein, into the HI loop of the HAdV5 fiber protein. This vector, HAdV5-CD21HIloop, binds specifically to CD21-positive cells and results in enhanced expression of the transgene in these cells and reduced expression in CD21-negative cells. Viral infection is highly correlated with the presence of CD21 receptors. Taken together, these results demonstrate that HAdV5-CD21HIloop is able to transduce CD21-positive cells specifically with reduced infection of nontarget cells. This is the result of the maintenance of the intracellular trafficking of the genetically modified adenovirus without vesicular retention, leading to enhanced nuclear transfer.

Adenovirus vector-mediated gene transfer into stem cells

Stem cells, including embryonic stem (ES) cells, mesenchymal stem cells (MSCs), and hematopoietic stem cells (HSCs), are defined by their capacity for self-renewal and multilineage differentiation. Efficient gene transfer into stem cells is essential for the basic research in developmental biology and for therapeutic applications in gene-modified regenerative medicine. Adenovirus (Ad) vectors, based on Ad type 5, can efficiently and transiently introduce the exogenous gene into many cell types via the primary receptor, coxsackievirus, and adenovirus receptor (CAR). However, some kinds of stem cells, such as MSCs and HSCs, cannot be efficiently transduced with conventional Ad vectors based on Ad serotype 5 (Ad5), because of the lack of CAR expression. To overcome this problem, fiber-modified Ad vectors and an Ad vector based on another serotype of Ad have been developed. Here, we review the advances in the development of Ad vectors suitable for stem cells and discuss their application in basic biology and clinical medicine.

Adenoviral vectors--how to use them in cancer gene therapy?

Gene therapy is most often described as a technique for introducing the foreign genetic material into cells with a correction of a dysfunctional gene as its final goal. Today, it is well known that cancer is one of the leading causes of mortality in the world. Besides classical methods for cancer treatment new strategies against cancer are needed. Although originally being designed as a treatment for monogenetic illness, soon after, gene therapy appeared as a potential new strategy in cancer therapy. One of the widely used vectors for cancer gene therapy is adenovirus. In this review we have described molecular biology of adenoviruses and basis for construction of adenoviral vectors. We have also described concepts for cancer gene therapy including their in vitro and in vivo application. Special attention is drawn toward retargeting of adenovirus as a new approach in vector design for cancer gene therapy, in order to restrict transgene expression in tumor tissue. This approach uses biophysical as well as genetic characteristics of tumor itself and its supporting tissue, allowing new "bypass" in cancer gene therapy.

Adenovirus types 11p and 35 attach to and infect primary lymphocytes and monocytes, but hexon expression in T-cells requires prior activation

Hematopoietic cells are attractive targets for gene therapy, but the conventional adenovirus (Ad) vectors, based on Ad5, transduce these cells inefficiently. One reason for low permissiveness of hematopoietic cells to infection by species C Ads appears to be inefficient attachment. Vectors pseudotyped with species B fibers are clearly more efficient at transducing hematopoietic cells than Ad5. To evaluate which Ad species B type(s) would be the most efficient vector(s) for primary T-cells, B-cells and monocytes, attachment to and entry of the species B1 serotypes 3p and 7p and the species B2 serotypes 11p and 35 into primary PBMCs was studied. Ad11p and Ad35 were the only serotypes to show efficient binding and for which uptake by PBMCs could be detected. Infection of PBMCs by Ad5, Ad11p and Ad35 was compared. Expression of Ad hexons was detected in stimulated PBMCs, most frequently in T-cells, and in unstimulated monocytes, although B-cells appear to be refractory to productive infection. Replication of Ad DNA was severely restricted in most PBMCs. Neither hexon expression nor genome replication could be detected in unstimulated lymphocytes, but FISH and a real-time PCR-based assay suggested that Ad11p and Ad35 DNA reach the nucleus. Activation thus appears to be required for T-cells to be permissive to Ad gene expression. In summary, there are substantial differences between Ad3p and Ad7p on the one hand and Ad11p and Ad35 on the other, in their ability to interact with PBMCs. Ad11p and Ad35 probably represent vectors of choice for these cell types.

Frequency, proliferation, and activation of human memory T cells induced by a nonhuman adenovirus

Multiple human adenovirus (HAd) infections during childhood generate a memory T-cell (T(M)) response, which is the primary defense against HAd-induced morbidity. This cellular memory creates a conundrum for the potential clinical use of HAd-derived vectors: vector-mediated gene transfer is efficient in immunologically naïve mammals but will be compromised by memory immunity when using vectors derived from ubiquitous human pathogens. The potential lack of cellular and humoral memory is one reason we developed vectors from canine adenovirus serotype 2 (CAV-2). Here, we assayed human peripheral blood mononuclear cells for a T(M) response that could be stimulated by CAV-2 virion and individual capsid proteins. We found that less than half of the donors harbored a proliferating T(M) response directed against the CAV-2 virion (versus >85% against HAd5) in spite of a conserved antigenic Adenoviridae epitope in the CAV-2 hexon. When CAV-2 induced proliferation, it was 2.3- to >10-fold lower than HAd5 depending on the assay. The primary proliferating cells appeared to be memory (CD45RO+) CD4+ lymphocytes, differentiated into Th1 gamma interferon-producing cells, with a frequency that was up to 66-fold lower than that obtained for HAd5. We also compared CAV-2 to prototype HAd from five of the six human species and found that CAV-2-induced cellular proliferation was similar to that found with rare HAd serotypes. Individual CAV-2 capsid proteins also induced less proliferation than their HAd5 homologues. Our data suggest that CAV-2 vectors may be safer (i.e., less immunogenic) for gene transfer but are not without a theoretical risk in a subset of potential patients.

Evaluation of biodistribution and safety of adenovirus vectors containing group B fibers after intravenous injection into baboons

Vectors containing group B adenovirus (Ad) fibers are able to efficiently transduce gene therapy targets that are refractory to infection with standard Ad serotype 5 (Ad5) vectors, including malignant tumor cells, hematopoietic stem cells, and dendritic cells. Preliminary studies in mice indicate that, after intravenous injection, B-group fiber-containing Ads do not efficiently transduce most organs and cause less acute toxicity than Ad5 vectors. However, biodistribution and safety studies in mice are of limited value because the mouse analog of the B-group Ad receptor, CD46, is expressed only in the testis, whereas in humans, CD46 is expressed on all nucleated cells. Unlike mice, baboons have CD46 expression patterns and levels that closely mimic those in humans. We conducted a biodistribution and toxicity study of group B Ad fiber-containing vectors in baboons. Animals received phosphate-buffered saline, Ad5-bGal (a first-generation Ad5 vector), or B-group fiber-containing Ads (Ad5/35-bGal and Ad5/11-bGal) at a dose of 2 x 10(12) VP/kg, and vector biodistribution and safety was analyzed over 3 days. The amount of Ad5/35-bGal and Ad5/11-bGal vector genomes was in most tissues one to three orders of magnitude below that of Ad5. Significant Ad5/35- and Ad5/11-mediated transgene (beta-galactosidase) expression was seen only in the marginal zone of splenic follicles. Compared with the animal that received Ad5-bGal, all animals injected with B-group fiber-containing Ad vectors had lower elevations in serum proinflammatory cytokine levels. Gross and histopathology were normal in animals that received B-group Ad fiber-containing Ads, in contrast to the Ad5-infused animal, which showed widespread endothelial damage and inflammation. In a further study, a chimeric Ad5/35 vector carrying proapoptotic TRAIL and Ad E1A genes under tumor-specific regulation was well tolerated in a 30-day toxicity study. No major clinical, serologic, or pathologic abnormalities were noticed in this animal.

Optimization of adenovirus serotype 35 vectors for efficient transduction in human hematopoietic progenitors: comparison of promoter activities

Adenoviral gene transfer to hematopoietic stem cells (HSCs)/progenitors would provide a new approach to the treatment of hematopoietic diseases and study of the hematopoietic system. We have previously reported that an adenovirus (Ad) vector composed of whole Ad serotype 35 (Ad35), which belongs to subgroup B, shows efficient gene transfer into human bone marrow CD34+ cells. However, Ad35 vector-mediated transduction into human HSCs/progenitors has not yet been fully optimized. In the present study, we have systematically examined promoter activity in the context of Ad35 vectors in human bone marrow CD34+ cells and primitive CD34+ subsets to optimize the transduction efficiency in human hematopoietic stem/progenitor cells. In the first of the transduction experiments, the improved in vitro ligation method was applied to Ad35 vector construction to allow for simple and efficient production of an E1/E3-deleted Ad35 vector. Using this method, we constructed a series of Ad35 vectors encoding the enhanced green fluorescence protein (GFP) under the control of a variety of strong viral and cellular promoters. Of the six types of promoters tested, significantly higher transduction efficiencies were achieved with the human elongation factor 1alpha promoter (EF1alpha promoter), the human cytomegalovirus (CMV) immediate-early 1 gene enhancer/beta-actin promoter with beta-actin intron (CA promoter), and the CMV promoter/enhancer with the largest intron of CMV (intron A) (CMVi promoter) in the human CD34+ cells and the immature subsets (CD34+ CD38(low/-) and CD34+ AC133+ subsets). In particular, the CA promoter was found to allow for the highest transduction efficiencies in both the whole human CD34+ cells and the immature hematopoietic subsets. Furthermore, the CA promoter-mediated GFP-expressing cells differentiated into progenitor cells of all lineages. These results indicate the construction of an optimized Ad35 vector backbone for efficient transduction into HSCs/progenitors.

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.

In vitro dendritic cell infection by pseudotyped adenoviral vectors does not correlate with their in vivo immunogenicity

Expression of antigens in dendritic cells (DC) can stimulate protective immunity against both viral infection and tumor growth, making them important targets for gene therapy. In-vitro-generated DC are commonly used in gene delivery studies with the assumption that the results will correlate with in vivo activity. Adenovirus Type 5 (Ad5) vectors have been widely used with DC, but these cells lack the primary receptor (CAR) used by Ad5 and are poorly infected. We investigated the use of Ad5 vector particles pseudotyped with fibers from other Ad serotypes in DC targeting. Several fiber proteins, including those from Ad16 (Subgroup B) and Ad37 (Subgroup D), conferred dramatically increased in vitro infection. Surprisingly, neither dendritic cell infection nor the immune response to an Ad-delivered antigen was improved when the modified viruses were tested in vivo. These results underscore the importance of using appropriate animal models in gene delivery studies.

Comparison of the efficiency of transduction of leukemic cells by fiber-modified adenoviruses

Efficient gene transfer with adenoviral type 5 (Ad5) vectors depends on the initial attachment of their fiber, which binds the coxsackie-adenovirus receptor (CAR), and their subsequent internalization, mediated by the interaction of viral penton base with target cell alphav integrins. We previously demonstrated that human leukemic cells lack these receptors and are therefore resistant to Ad5 transduction, limiting efforts to genetically modify these cells. Human leukemic blasts are, however, susceptible to transduction with an adenovector made CAR independent by substitution of a chimeric Ad5/35 fiber [Yotnda et al. (2001). Gene Ther. 8, 930-937]. Other receptors can also be targeted with recombinant ligand moieties incorporated into adenovirus fiber. We have determined which of these fiber-modified adenovectors is most effective at modifying human primary leukemia cells, and lines. We used a replication-incompetent Ad5-beta-gal vector, in which the Ad5 fiber was replaced with fiber from various adenovirus serotypes (Ad35 and Ad11), or modified either with variable length polylysine (K4, K7, K21) or RGD-4C peptide. All the modified fiber vectors transduced primary leukemia cells and cell lines more efficiently than Ad5. Polylysine-substituted Ad5F/K21 and peptide-modified Ad5F/RGD vectors were most effective overall (up to 100% efficiency), whereas Ad5F/RGD was the most effective at transducing B cell acute lymphoblastic leukemia cells (90% efficiency). Ad5F/K21 and Ad5F/RGD should be of value for the genetic modification of human primary leukemia cells.

Adenovirus infections in stem cell transplant recipients: recent developments in understanding of pathogenesis, diagnosis and management

Adenovirus is increasingly recognized as an important pathogen in stem cell transplant recipients, reflecting increased awareness about the virus, together with changes in transplant practice such as the performance of more high-risk transplants, and improvements in diagnostic methods. In retrospective studies, the reported incidence of adenovirus infections ranged between 4-20% with a similar variation in the proportion of patients developing invasive disease. In contrast, the incidence of adenovirus infection varies between 20-30% in recent prospective studies on T-cell depleted or mismatched allografts and about 30-40% of these patients develop invasive disease. These prospective studies have established a relationship between the risk of invasive adenovirus disease and a number of factors such as the extent of T-cell depletion, the intensity of immunosuppressive therapy and the kinetics of lymphocyte recovery post-transplant. Polymerase chain reaction (PCR) assays to detect adenovirus DNA in peripheral blood have shown a strong correlation between viremia and the risk of disseminated adenovirus disease. These developments have led to the possibility of a preemptive antiviral treatment strategy for asymptomatic adenovirus infections. In addition, a better understanding of the interactions between adenovirus and host immune system in the post-transplant setting might enable development of effective immunotherapeutic strategies against adenovirus infections.

Human hematopoietic (CD34+) stem cells possess high-affinity receptors for adenovirus type 11p

Gene transfer into human hematopoietic stem cells using Ad5 is inefficient due to lack of the primary receptor CAR and the secondary receptors alphavbeta3 integrin and alphavbeta5 integrin, and due to the high seroprevalence of Ad5 antibodies in most adults, resulting in diminished gene transduction. In the present study, we screened six species (species A-F) of adenovirus, displaying different tropisms for interaction with CD34+ cells, at the level of virus attachment and expression. Virus particles were biotinylated and their binding capacity was determined by FACS analysis using streptavidin-FITC. Ad11p, Ad35, and Ad3 (species B) showed high binding affinity, while Ad7, Ad11a (species B), and Ad37 (species D) displayed intermediate affinity. Virions of Ad4 (species E), Ad5 (species C), Ad31 (species A), and Ad41 (species F) hardly bound to hematopoietic progenitor cells. Using a double-labeling system, we demonstrated that adenoviruses bind to quiescent CD34+ cells. Ad11p virions showed the highest affinity among the adenoviruses detected. We further confirmed that virus fiber-specific receptors were present on the hematopoietic progenitor cell surface, because both recombinant fiber of Ad11p and specific antiserum against rfiber could block virus attachment. The ability of the adenoviruses to infect hematopoietic cells was studied by immunofluorescence staining. The adenoviruses from species B and Ad37 showed higher infectivity than Ad31, Ad5, Ad4, and Ad41. Among the studied species B adenoviruses, Ad11p manifested a superior infectivity. Thus, we have confirmed that these cells have high-affinity receptors for species B:2 human adenovirus, Ad11p, and this virus may be used as candidate vector to target therapeutic genes to hematopoietic stem cells.

Gene transfer into human T lymphocytes and natural killer cells by Ad5/F35 chimeric adenoviral vectors

OBJECTIVE

Genetic modification of effector lymphocytes, such as T cells and natural killer (NK) cells, is essential for many approaches to gene-based immunotherapy of cancer. However, transduction of lymphocytes has proven difficult by currently available gene transfer methods. Previous studies have shown that chimeric fiber-modified Ad5/F35 adenoviral vectors are able to efficiently transduce hematopoietic cells including immature progenitors. In this study, we examined the gene transfer into T lymphocytes and NK cells using Ad5/F35 compared with conventional Ad5 adenovectors.

METHODS

Primary T and NK cells were isolated from healthy donors' peripheral blood leukocytes by immunomagnetic selection. Cell lines and primary lymphocytes were transduced with replication-defective Ad5/F35 and Ad5, both containing a GFP reporter gene under the control of a CMV promoter. Transduction efficiencies were monitored by flow cytometry. The function of transduced lymphocytes was assessed by analysis of proliferative responses to mitogenic agents and in mixed leukocyte reactions.

RESULTS

Transgene expression was detected in up to 45% of primary CD3+ T lymphocytes and in up to 60% of primary NK cells using Ad5/F35. In contrast, conventional Ad5 transduced less than 8% and 5% of primary T cells and NK cells, respectively. Transduction efficiencies were similar in CD4+ and CD8+ T lymphocytes, and transgene expression could be detected for up to seven days. Activation of T cells significantly enhanced the efficiency of Ad5/F35-mediated gene transfer. Adenoviral transduction of lymphocytes did not result in any impairment of proliferative functions.

CONCLUSION

The results of this study demonstrate that both T lymphocytes and NK cells can be transduced by chimeric Ad5/F35 adenoviral vectors.

Targeted delivery of adenoviral vectors by cytotoxic T cells

Effective targeting of vectors to tumor cells that have metastasized to multiple different tissue sites remains a major challenge for gene therapy. Tumor-specific cytotoxic T lymphocytes (CTLs) have been shown in animal models and in humans to be able to cross tissue barriers and traffic to tumor cells. However, their capacity to eliminate malignancy has been limited by tumor immune evasion strategies. We now use a model of Epstein-Barr virus-mediated malignancy to show that human CTLs themselves may be modified to release therapeutic vectors following engagement of their antigen-specific receptors and that these vectors will effectively transduce and destroy tumor targets. We generated EBV-specific CTLs that were transgenic for the adenoviral E1 gene under the control of the cell activation-dependent CD40 ligand (CD40L) promoter. Following transduction with E1-deficient adenoviral vectors, these CTLs produced infectious virus when exposed to HLA-matched EBV-expressing targets, but not on exposure to major histocompatibility complex (MHC)-mismatched or otherwise irrelevant cells. This approach provides a means of delivering oncolytic/therapeutic vectors not only to locally accessible macroscopic tumors as is presently the case, but also to disseminated metastatic disease, while avoiding the risks associated with systemic administration of large doses of adenoviral vectors.

Adenovirus serotype 3 utilizes CD80 (B7.1) and CD86 (B7.2) as cellular attachment receptors

Most viruses exploit a variety of host cellular proteins as primary cellular attachment receptors in the context of successful execution of infection. Furthermore, many viral agents have evolved precise mechanisms to subvert host immune recognition to achieve persistence. Herein we present data indicating that adenovirus (Ad) serotype 3 utilizes CD80 (B7.1) and CD86 (B7.2) as cellular attachment receptors. CD80 and CD86 are co-stimulatory molecules that are present on mature dendritic cells and B lymphocytes and are involved in stimulating T-lymphocyte activation. To our knowledge, this is one of the first demonstrations of a virus utilizing immunologic accessory molecules as a primary means of cellular entry. This finding suggests a mechanism whereby viral exploitation of these proteins as receptors may achieve both goals of cellular entry and evading the immune system.

Approaches to utilize mesenchymal progenitor cells as cellular vehicles

Mammalian cells represent a novel vector approach for gene delivery that overcomes major drawbacks of viral and nonviral vectors and couples cell therapy with gene delivery. A variety of cell types have been tested in this regard, confirming that the ideal cellular vector system for ex vivo gene therapy has to comply with stringent criteria and is yet to be found. Several properties of mesenchymal progenitor cells (MPCs), such as easy access and simple isolation and propagation procedures, make these cells attractive candidates as cellular vehicles. In the current work, we evaluated the potential utility of MPCs as cellular vectors with the intent to use them in the cancer therapy context. When conventional adenoviral (Ad) vectors were used for MPC transduction, the highest transduction efficiency of MPCs was 40%. We demonstrated that Ad primary-binding receptors were poorly expressed on MPCs, while the secondary Ad receptors and integrins presented in sufficient amounts. By employing Ad vectors with incorporated integrin-binding motifs (Ad5lucRGD), MPC transduction was augmented tenfold, achieving efficient genetic loading of MPCs with reporter and anticancer genes. MPCs expressing thymidine kinase were able to exert a bystander killing effect on the cancer cell line SKOV3ip1 in vitro. In addition, we found that MPCs were able to support Ad replication, and thus can be used as cell vectors to deliver oncolytic viruses. Our results show that MPCs can foster expression of suicide genes or support replication of adenoviruses as potential anticancer therapeutic payloads. These findings are consistent with the concept that MPCs possess key properties that ensure their employment as cellular vehicles and can be used to deliver either therapeutic genes or viruses to tumor sites.

Induction of CAMEL/NY-ESO-ORF2-specific CD8+ T cells upon stimulation with dendritic cells infected with a modified Ad5 vector expressing a chimeric Ad5/35 fiber

Delivery of the full-length tumor antigen might be more successful in immunotherapy than single peptides and has the advantage that patients no longer need to be selected for their HLA type. In this study, we tested the in vitro induction of CAMEL/NY-ESO-ORF2-specific T cells by dendritic cells infected with an adenovirus (Ad) type 5 vector containing the fiber shaft and knob of human serotype Ad35 (Ad5F35 vector). Our data show induction of CD8(+) T cells specific for the known HLA-A(*)0201-binding CAMEL/NY-ESO-ORF2(1-11) epitope by DC infected with Ad5F35-CAMEL, but not by DC pulsed with the recombinant CAMEL protein. In one healthy donor, even CD8(+) T cells specific for a new HLA-B7-binding CAMEL/NY-ESO-ORF2(46-54) epitope were raised. In conclusion, the in vitro induction of CAMEL/NY-ESO-ORF2-specific CD8(+) T cells in healthy donors by DC infected with Ad5F35-CAMEL strongly supports further investigation of the Ad5F35 vector as a vehicle for gene transfer into DC for the generation of tumor antigen-specific CD8(+) T cell responses in vivo.

Characterization of in vitro and in vivo gene transfer properties of adenovirus serotype 35 vector

We have recently developed a replication-defective, recombinant adenovirus (Ad) vector composed of the whole Ad serotype 35 (Ad35), a member of subgroup B. We describe herein the in vitro and in vivo gene transfer properties of Ad35 vector in comparison with Ad serotype 5 (Ad5) and the Ad5F35 vector, which is a fiber-substituted Ad5 vector containing Ad35 fiber proteins. In vitro, Ad35 vector efficiently transduced not only human CAR-positive cells but also CAR-negative cells. Following intravenous administration into mice, both Ad5 and Ad35 vectors were rapidly cleared from the bloodstream with a half-life of approximately 3 min. Ad5 vector-mediated transgene expression predominantly occurred in liver parenchymal cells, although the Ad5 vector was delivered to both liver parenchymal and nonparenchymal cells. In contrast, Ad35 vector was efficiently taken up by liver nonparenchymal cells and mediated transduction efficiency in the liver on a level 4 log orders lower than the Ad5 vector. These findings demonstrate that Ad35 vector is an attractive vehicle for gene transfer into human cells, while the biodistribution profile of Ad35 vector in mice is much different from that of the Ad5 vector.

General strategy for broadening adenovirus tropism

In spite of its broad host range, adenovirus type 5 (Ad5) transduces a number of clinically relevant tissues and cell types inefficiently, mostly because of low expression of the coxsackievirus-adenovirus receptor (CAR). To improve gene transfer to such cells, we modified the Ad5 fiber knob to recognize novel receptors. We expressed a functional Ad5 fiber knob domain on the capsid of phage lambda and employed this display system to construct a large collection of ligands in the HI loop of the Ad5 knob. Panning this library on the CAR-negative mouse fibroblast cell line NIH 3T3 resulted in the identification of three clones with increased binding to these cells. Adenoviruses incorporating these ligands in the fiber gene transduced NIH 3T3 cells 2 or 3 orders of magnitude better than the parent vector. The same nonnative tropism was revealed in other cell types, independently of CAR expression. These Ad5 derivatives proved capable of transducing mouse and human primary immature dendritic cells with up to 100-fold increased efficiency.

Adenovirus type 11 uses CD46 as a cellular receptor

The 51 human adenovirus serotypes are divided into six species (A to F). Many adenoviruses use the coxsackie-adenovirus receptor (CAR) for attachment to host cells in vitro. Species B adenoviruses do not compete with CAR-binding serotypes for binding to host cells, and it has been suggested that species B adenoviruses use a receptor other than CAR. Species B adenoviruses mainly cause disease in the respiratory tract, the eyes, and in the urinary tract. Here we demonstrate that adenovirus type 11 (Ad11; of species B) binds to Chinese hamster ovary (CHO) cells transfected with CD46 (membrane cofactor protein)-cDNA at least 10 times more strongly than to CHO cells transfected with cDNAs encoding CAR or CD55 (decay accelerating factor). Nonpermissive CHO cells were rendered permissive to Ad11 infection upon transfection with CD46-cDNA. Soluble Ad11 fiber knob but not Ad7 or Ad5 knob inhibited binding of Ad11 virions to CD46-transfected cells, and anti-CD46 antibodies inhibited both binding of and infection by Ad11. From these results we conclude that CD46 is a cellular receptor for Ad11.

Purging of leukemia-contaminated bone marrow grafts using suicide adenoviral vectors: an in vivo murine experimental model

Autologous bone marrow transplantation is an alternative therapeutic option for acute myeloid leukemia patients lacking a compatible donor. However, bone marrow from these patients may contain residual leukemic cells that should be ideally eliminated prior to the infusion of the graft. With the aim of developing more efficient protocols of graft purging, adenoviral-mediated gene transfer protocols have been conducted. We studied whether suicide adenoviral vectors expressing the cytosine deaminase gene (AdCD) could be used for selectively killing leukemic WEHI-3B cells. The AdCD transduction followed by the 5-fluorocytosine exposure abrogated the growth of WEHI-3B cells in vitro, with a minimal effect on normal hematopietic progenitors. To test the efficacy of the purging protocol in vivo, bone marrow cells were mixed with syngenic WEHI-3B cells and this chimeric cell population was transduced with AdCD vectors. Infected cells were injected into myeloablated Balb-c mice, which then received a 5-fluorocytosine treatment for 4 days. All mice transplanted with unpurged bone marrow developed leukemia and died. However, 90% of recipients receiving the purging treatment were healthy up to 9 months post-transplantation and had a perfectly re-established hematopoietic system, without any signal of leukemic cell presence. In conclusion, suicide adenoviral vectors are proposed as a tool for the purging of Adenoviral-susceptible myeloid leukemia cells contaminating autologous bone marrow grafts.

Comparative analysis of the genome organization of human adenovirus 11, a member of the human adenovirus species B, and the commonly used human adenovirus 5 vector, a member of species C

Adenovirus type 11 (Ad11), a member of the human adenovirus species B (HAdV-B), has a tropism for the urinary tract. The genome of Ad11 was found to comprise 34 794 bp and is 1141 bp shorter than the Ad5 genome of species HAdV-C. The G+C content of the Ad11 genome is 48.9 %, whereas that of Ad5 is 55.2 %. Ad11 and Ad5 share 57 % nucleotide identity and possess the same four early regions, but the E3 region of Ad11 could not be divided into E3A and E3B. The late genes of Ad11 and Ad5 are organized into six and five regions, respectively. Thirty-eight putative ORFs were identified in the Ad11 genome. The ORFs in the late regions, the E2B region and IVa2 show high amino acid identity between Ad11 and Ad5, whereas the ORFs in E1, E2A, E3 and E4, protein IX and the fibre protein show low amino acid identity. The highest and lowest identities were noted in the pre-terminal protein and fibre proteins: 85 % and 24.6 %, respectively. The E3 20.3K and 20.6K ORFs and the L6 agnoprotein were present in the Ad11 genome only, whereas the E3 11.6K cell death protein was identified only in Ad5. All ORFs but the E3 10.3K and L4 pVIII protein vary not only in composition but also in size. Ad11 may have a higher vector capacity than Ad5, since it has a shorter genome and a shorter fibre. Furthermore, in the E3 region, two additional ORFs can be deleted to give extra capacity for foreign DNA.