Enhanced efficiency by centrifugal manipulation of adenovirus-mediated interleukin 12 gene transduction into human monocyte-derived dendritic cells

Preexisting Virus-Specific T Lymphocytes-Mediated Enhancement of Adenovirus Infections to Human Blood CD14+ Cells

Antigen-specific T lymphocytes play a critical role in controlling viral infections. However, we report here that preexisting virus-specific T cell responses also contribute to promoting adenovirus (Ad) infection. Previously, we found that CD14+ monocytes from Ad-seropositive individuals exhibited an increased susceptibility to Ad infection, when compared with that of Ad-seronegative individuals. But the underlying mechanisms for this enhancement of viral infection are not completely clarified. In this study, we found that the efficacy of Ad infection into CD14+ monocytes was significantly decreased after CD3+ T lymphocytes depletion from PBMC samples of Ad-seropositive individuals. In contrast, adding virus-specific CD3+ T lymphocytes into PBMC samples of Ad-seronegative individuals resulted in a significant increase of infection efficacy. CD3+ T lymphocytes in PBMC samples from Ad-seropositive individuals were more sensitive to be activated by adenovirus stimulus, characterized by upregulation of multiple cytokines and activation markers and also enhancement of cell proliferation. Further studies demonstrated that GM-CSF and IL-4 can promote Ad infection by up-regulating the expression of scavenger receptor 1 (SR-A) and integrins αVβ5 receptor of CD14+ cells. And taken together, these results suggest a novel role of virus-specific T cells in mediating enhancement of viral infection, and provide insights to understand the pathogenesis and complicated interactions between viruses and host immune cells.

SLC gene-modified dendritic cells mediate T cell-dependent anti-gastric cancer immune responses in vitro

Dendritic cells (DCs) are potent professional antigen-presenting cells (APCs) with the ability to prime naïve T cells, and play an important role in the initiation and regulation of immune responses. In this study, we constructed a recombinant adenovirus carrying the SLC gene (Ad-SLC), and detected the biological effects of Ad-SLC-modified DCs as an adjuvant for the initiation of gastric cancer immune responses. Human DCs were transfected with Ad-SLC and the recombinant adenovirus carrying the β-galactosidase gene, Ad-LacZ, respectively. Modified DCs were pulsed with the cell lysate antigen of SGC-7901 cells (a type of gastric cancer cell line) and co-cultured with autologous T cells. The T cells were harvested and incubated with SGC-7901 cells and the cytotoxic function of the T cells was detected. Based on the data, the expression of mature DC phenotypes CD83 and CCR7 was upregulated after transfection with Ad-SLC and the chemotaxis function of DCs was augmented after transfection with Ad-SLC. Moreover, the expression of RANTES in DCs was upregulated by Ad-SLC transfection, while expression levels of IL-12p70 and IL-10 were not significantly altered. When co-cultured with autologous T cells, DCs modified with the SLC gene and pulsed with SGC-7901 cell lysates significantly promoted the proliferation of autologous T cells and induced Th1 differentiation, and displayed a strong cytotoxicity to SGC-7901 cells. In conclusion, Ad-SLC promoted DC maturation, enhancing the ability of DCs for T-cell chemotaxis and T-cell stimulation, and induced specific anti-gastric cancer cellular immunity. Recombinant Ad-SLC-modified DCs may be used as an adjuvant to induce an effective anti-gastric cancer immune response.

Bacillus Calmette-Guérin cell-wall skeleton enhances the killing activity of cytotoxic lymphocyte-activated human dendritic cells transduced with the prostate-specific antigen gene

To determine whether dendritic cells (DC) transduced with the prostate-specific antigen (PSA) gene can induce PSA-specific cytotoxic lymphocytes (CTL) against prostate cancer cells, and whether bacillus Calmette-Guérin (BCG) cell-wall skeleton (CWS) can enhance the maturation of DC-PSA and the killing activity of subsequently induced PSA-specific CTL. MATERIALS AND METHODS; We generated an adenovirus encoding the PSA gene (AxCA-PSA) using the cosmid-terminal protein complex method. DC were infected with AxCA-PSA using the centrifugal method. The ability of CTL to lyse target cells expressing PSA, i.e the PSA-positive prostate cancer cell line, LNCap, and PSA-transduced autologous phytohaemagglutinin (PHA) blasts expressing PSA, was assessed using the 51Cr-release assay. The maturation of DC-PSA stimulated by BCG-CWS was assayed by flow cytometry. The cytotoxic activity enhanced by BCG-CWS was assessed by the 51Cr-release assay.

RESULTS

DC-PSA induced PSA-specific CTL with 85% cytotoxic activity against LNCaP (effector: target ratio, E:T, of 50:1). However, the cytotoxic activity against PSA-negative cells was very low. Anti-CD8 and anti-major histocompatibility (MHC) class I antibodies blocked PSA-specific cytotoxicity. The PSA-specific killing was reproducible against autologous PHA blast cells expressing PSA, independently of human leukocyte antigen haplotype. Furthermore, the combination of DC-PSA with BCG-CWS remarkably enhanced the PSA-specific cytotoxicity against PHA blasts expressing PSA (15-30% at an E:T ratio of 50:1).

CONCLUSION

These findings suggest that DC-PSA can induce MHC class I-restricted PSA-specific CD8+ CTL responses and that DC-PSA matured by BCG-CWS enhance PSA-specific cytotoxicity. The combination of DC-PSA with BCG-CWS might be a useful approach for treating advanced prostate cancer.

Expression of soluble vascular endothelial growth factor receptor-1 in human monocyte-derived mature dendritic cells contributes to their antiangiogenic property

The soluble form of vascular endothelial growth factor receptor-1 (sVEGFR-1) is produced from endothelial cells by alternative splicing of VEGFR-1 mRNA, and can inhibit angiogenesis by blocking the biological effects of VEGF. In this study, we show the expression of a large amount of sVEGFR-1 in human monocyte-derived mature dendritic cells (mDCs). As compared with monocytes and immature DCs, mDCs generated by TNF-alpha or soluble CD40L with IFN-gamma, but not LPS or other stimuli, preferentially produce sVEGFR-1. We also detected the mRNA of sVEGFR-1 generated by alternative splicing of VEGFR-1 mRNA in mDCs induced by TNF-alpha. The production of sVEGFR-1 showed a distinct contrast to those of VEGF in each DC matured with various stimuli. The supernatant of DCs matured with TNF-alpha or soluble CD40L with IFN-gamma showed inhibition of the tube formation of HUVECs, which was neutralized by anti-VEGFR-1 Ab, indicating that sVEGFR-1 secreted from mDCs was biologically active. Interestingly, the supernatant of mDCs generated with LPS increased HUVEC capillary-like formation in vitro. The ratio of sVEGFR-1 to VEGF clearly reflected the net angiogenic property of mDCs. Administration of mDCs induced by TNF-alpha into the s.c. tumor of PC-14 cells implanted in SCID mice demonstrated the inhibition of tumor growth via reduction of the number of CD31-positive vessels, indicating their in vivo antiangiogenic potential. These results suggest that sVEGFR-1 produced by mDCs contribute to their antiangiogenic property, and the ratio of sVEGFR-1 to VEGF might be a useful tool for evaluating their ability to regulate angiogenesis mediated by VEGF.

Dendritic cells modified with 6Ckine/IFNgamma fusion gene induce specific cytotoxic T lymphocytes in vitro

BACKGROUND AND OBJECTIVE

[corrected] Dendritic cells play an important role in initiation and regulation of immune responses. Previous studies demonstrated that intratumoral administration of 6Ckine-modified DCs enhanced local and systemic antitumor effects. Herein we report the investigation of the specific CTL responses elicited by adenoviral 6Ckine/IFNgamma fusion gene-modified DCs in vitro.

METHODS

Human monocyte-derived DCs were modified with an adenoviral vector encoding 6Ckine/IFNgamma fusion protein (Ad-6Ckine/IFNgamma), and then investigated the effect of 6Ckine/IFNgamma fusion protein on the maturation, cytokine and chemokine secretion of DCs, and their activities of recruiting and activating T cells in vitro were investigated.

RESULTS

6Ckine/IFNgamma fusion protein induced DC maturation characterized with the upregulation of CD83 and CCR7. And it up-regulated the expression of RANTES and IL-12p70, down-regulated that of IL-10 in DCs. Additionally, 6Ckine/IFNgamma markedly increased DC's recruiting ability for naive T cells, benefiting from the enhanced expression of chemokines 6Ckine and RANTES in DCs. Fusion gene-modified DCs significantly promoted the proliferation of autologous T cells, induced Th1 differentiation by upregulating the expression of IL-2 and T-bet in T cells, and increased specific cytotoxicity of CTLs against specific tumor cells, HepG2 or LoVo cells, respectively.

CONCLUSION

Combining the effects of 6Ckine and IFNgamma, Ad-6Ckine/IFNgamma modified DCs induced enhanced CTL responses in vitro, which indicated that Ad-6Ckine/IFNgamma modified DCs might be used as an adjuvant to trigger an effective antitumor immune response.

Successful cancer vaccine therapy for carcinoembryonic antigen (CEA)-expressing colon cancer using genetically modified dendritic cells that express CEA and T helper-type 1 cytokines in CEA transgenic mice

This study was designed to determine whether the vaccination of genetically modified dendritic cells (DCs) simultaneously expressing carcinoembryonic antigen (CEA), granulocyte macrophage colony-stimulating factor (GM-CSF) and interleukin 12 (IL-12) can overcome the peripheral T-cell tolerance to CEA and thereby elicit a therapeutic response in CEA transgenic mice. CEA transgenic mice were immunized once by subcutaneous injection with DCs adenovirally transduced with CEA and T helper-type 1 cytokine genes. The cytotoxic activity of spleen cells against CEA-expressing tumors, MC38-CEA, in the mice immunized with DCs expressing CEA (DC-AxCACEA) was higher than that in those immunized with DCs-AxCALacZ (p < 0.0001), and was augmented by the cotransduction with the GM-CSF/IL-12 gene (p < 0.05). The vaccination with DC-AxCACEA/GM-CSF/IL-12 could elicit a more potent therapeutic immunity than the vaccination with DC-AxCACEA in subcutaneous tumor models (p < 0.0001), and 4 of 5 mice showed a complete eradication of the subcutaneous tumors in these vaccination groups. Even in a large tumor model, this vaccination therapy completely eliminated the subcutaneous tumors in all mice. This antitumor activity mostly vanished with the depletion of CD8(+) T cells and NK cells in vivo and was completely abrogated with the depletion of CD4(+) T cells. A histopathological examination showed no evidence of an autoimmune reaction. No other adverse effects were observed. This vaccination strategy resulted in the generation of highly efficient therapeutic immune responses against MC38-CEA in the absence of autoimmune responses and demonstrated no adverse effects, and may therefore be useful for future clinical applications as a cancer vaccine therapy.

Induction of potent antitumor immunity by intratumoral injection of interleukin 23-transduced dendritic cells

Dendritic cells (DCs) are potent antigen-presenting cells that play a critical role in priming immune responses to tumor. Interleukin (IL)-23 can act directly on DC to promote immunogenic presentation of tumor peptide in vitro. Here, we evaluated the combination of bone marrow-derived DC and IL-23 on the induction of antitumor immunity in a mouse intracranial glioma model. DCs can be transduced by an adenoviral vector coding single-chain mouse IL-23 to express high levels of bioactive IL-23. Intratumoral implantation of IL-23-expressing DCs produced a protective effect on intracranial tumor-bearing mice. The mice consequently gained systemic immunity against the same tumor rechallenge. The protective effect of IL-23-expressing DCs was comparable with or even better than that of IL-12-expressing DCs. IL-23-transduced DC (DC-IL-23) treatment resulted in robust intratumoral CD8(+) and CD4(+) T-cell infiltration and induced a specific TH1-type response to the tumor in regional lymph nodes and spleen at levels greater than those of nontransduced DCs. Moreover, splenocytes from animals treated with DC-IL-23 showed heightened levels of specific CTL activity. In vivo lymphocyte depletion experiments showed that the antitumor immunity induced by DC-IL-23 was mainly dependent on CD8(+) T cells and that CD4(+) T cells and natural killer cells were also involved. In summary, i.t. injection of DC-IL-23 resulted in significant and effective systemic antitumor immunity in intracranial tumor-bearing mice. These findings suggest a new approach to induce potent tumor-specific immunity to intracranial tumors. This approach may have therapeutic potential for treating human glioma.

Current State and Perspectives of Dendritic Cell Vaccination in Cancer Immunotherapy

Recent progress in the approach towards immunotherapy of cancer consists in molecular definition of tumor antigens, new tools for phenotypical and functional characterization of tumor-specific effector cells and clinical use of novel adjuvants for optimal stimulation of a cancer-specific immune response such as dendritic cells. In spite of these advances and immunological as well as clinical responses in selected patients, mechanisms involved in dendritic-cell-based cancer immunotherapy are still poorly understood. Therefore, a standardized study design and small pilot trials are needed to explore open scientific questions in future clinical trials. This review focuses on the different parameters of dendritic cell biology relevant to cancer immunotherapy and on innovative approaches to hopefully enhance the efficacy of dendritic cell vaccination.

Centrifugation enhances integrin-mediated transduction of dendritic cells by conventional and RGD-modified adenoviral vectors

The level of antigen loading can impact on the capacity for dendritic cells (DC) to activate T cell responses. Several different approaches to adenoviral (Ad)-based transduction were therefore assessed for their effect on both transgene expression and T cell activation. While a conventional E1(-)/E3Delta Ad vector (Ad/GFP) produced a concentration-dependent expression of GFP, a modified vector expressing Arginine-Glycine-Aspartic Acid (RGD) sequence on its fiber knob (Ad-RGD/GFP) enhanced transgene expression by 9-20-fold at each MOI. The addition of centrifugal force (2000xg) during DC transduction with Ad/GFP also increased expression up to 20-fold. However, combining centrifugation with the Ad-RGD/GFP vector produced no effect on transduction rate and only a 1.5- to 2-fold increase in GFP expression, suggesting overlapping mechanisms of action. Consistent with this, exogenous RGD peptide blocked transduction regardless of the vector used, or the addition of centrifugal force, and transduction was primarily limited to DC expressing the CD51 integrin receptor. Ad vectors expressing ovalbumin (OVA) were used to assess transduced DC for their capacity to activate OVA-specific T cells. We observed a significant relationship between transgene expression and the capacity for T cell activation regardless of whether transgene expression was increased by using a higher MOI, an RGD-modified vector, or by employing centrifugal force. Furthermore, combining these approaches produced synergistic effects on T cell activation. We conclude that RGD-modified vectors and centrifugation both enhance DC transduction by increasing entry via integrin receptors and that the capacity for T cell activation can be optimized by combining approaches to achieve the highest possible level of transgene expression.

Induction of Tc1 response and enhanced cytotoxic T lymphocyte activity in mice by dendritic cells transduced with adenovirus expressing HBsAg

We evaluated the potential of dendritic cells (DCs) engineered to express antigen of hepatitis B virus (HBV) in priming Th/Tc and HBV-specific CTL responses in mice. Recombinant adenovirus expressing hepatitis B surface antigen (HBsAg) (Ad-S) was constructed, and bone marrow-derived DCs were transduced with Ad-S or pulsed with HBsAg protein. Mice were injected with either Ad-S-transduced DCs or HBsAg-pulsed DCs or plasmid DNA encoding HBsAg twice at 3-week intervals. We showed that adenovirus infection had no further effect on the phenotype, the ability to induce IFN-gamma-producing Th1/Tc1 response or the T cell stimulatory capacity of already mature DCs in vitro. We also showed that immunization with Ad-S-transduced DCs effectively induced Tc1 cells and HBsAg-specific CTLs in vivo and down-regulated the circulating HBsAg and HBV DNA in HBV transgenic mice. Furthermore, these efficacies were stronger than that of HBsAg-pulsed DCs and plasmid DNA. Thus, DCs transduced with recombinant adenovirus may be a promising candidate for an effective CTL-based therapeutic vaccine against HBV.

Langerhans-Type Dendritic Cells Genetically Modified to Express Full-Length Antigen Optimally Stimulate CTLs in a CD4-Dependent Manner

Oncoretroviral vectors encoding either full-length Ag or a corresponding immunodominant peptide were expressed in Langerhans-type dendritic cells (LCs) differentiated from CD34(+) progenitors. We used human CMV as a model Ag restricted by HLA-A*0201 to define parameters for eventual expression of cancer Ags by LCs for active immunization against tumors. Stimulation by CMVpp65(495-503)-pulsed LCs, CMVpp65(495-503)-transduced LCs, and full-length CMVpp65-transduced LCs respectively increased tetramer-reactive T cells with an effector memory phenotype by 10 +/- 11, 34 +/- 21, and 51 +/- 24-fold (p < 0.05) from CMV-seropositive donors. CMV-specific CD8(+) CTLs achieved respective frequencies of 231 +/- 102, 583 +/- 219, and 714 +/- 281 spot-forming cells per 10(5) input cells (p < 0.01) in ELISPOT assays for IFN-gamma secretion. LCs expressing full-length Ag stimulated greater lytic activity than either peptide-transduced or peptide-pulsed LCs (p < 0.05), all in the absence of exogenous cytokines. pp65-transduced LCs presenting class I and II MHC-restricted epitopes expanded IFN-gamma-secreting CD4(+) T cells, whereas pp65(495-503)-transduced LCs did not. CD4(+) T cell numbers even declined after stimulation by pp65(495-503) peptide-pulsed LCs. CD4(+) T cell depletion confirmed their contribution to the more robust CTL responses. LCs, transduced with a retroviral vector encoding full-length Ag, stimulate potent CTLs directed against multiple epitopes in a CD4(+) Th cell-dependent manner.

Antitumor effect of intratumoral administration of bone marrow-derived dendritic cells transduced with wild-type p53 gene

PURPOSE

Dendritic cells (DCs) are attractive effectors for cancer immunotherapy because of their potential to function as professional antigen-presenting cells for initiating cellular immune responses. The tumor suppressor gene p53 is pivotal in the regulation of apoptosis, and approximately 50% of human malignancies exhibit mutation and aberrant expression of p53. We investigated the antitumor effect of intratumoral administration of bone marrow-derived dendritic cells transduced with wild-type p53 gene.

EXPERIMENTAL DESIGN

We examined whether intratumoral administration of DCs infected with recombinant adenovirus expressing murine wild-type p53 (Ad-mp53) could induce systemic antitumor responses against mutant p53-expressing tumors, highly immunogenic MethA, or weakly immunogenic MCA-207 implanted in syngeneic mice.

RESULTS

Accumulation of wild-type p53 protein in bone marrow-derived murine DCs could be successfully achieved by Ad-mp53 infection. Treatment with intratumoral injection of Ad-mp53-transduced DCs caused a marked reduction in the in vivo growth of established MethA and MCA-207 tumors with massive cellular infiltrates. Administration of p53-expressing DCs suppressed the growth of both injected MCA-207 tumors and untreated distant MCA-207 tumors, but not unrelated Lewis lung carcinoma tumors, suggesting the augmentation of systemic immunogenicity against MCA-207 tumor cells. Moreover, intratumoral injection of p53-expressing DCs had a greater antitumor effect than did s.c. immunization.

CONCLUSIONS

Our results indicate that intratumoral administration of DCs expressing murine wild-type p53 leads to significant systemic immune responses and potent antitumor effects in mutant p53-expressing murine cancer models. These findings raise the possibility of using this strategy of intratumoral injection of p53-expressing DCs for human cancer treatment.

Route of administration influences the antitumor effects of bone marrow-derived dendritic cells engineered to produce interleukin-12 in a metastatic mouse prostate cancer model

Gene-modified dendritic cells (DC) provide unique therapeutic strategies for prostate cancer; however, the comparative evaluation of specific delivery options using appropriate preclinical models has not been described. In this study, bone marrow-derived DC were genetically engineered to express high levels of interleukin-12 (IL-12) with or without the costimulatory molecule B7-1, by ex vivo infection with recombinant adenoviral vectors. We used an orthotopic metastatic mouse prostate cancer preclinical model (178-2 BMA) to compare two therapeutic protocols for DC delivery, in situ and subcutaneous. DC were generated from bone marrow of syngeneic 129/Sv mice by culturing in the presence of GM-CSF and IL-4. In vitro DC/IL-12 or DC/IL-12/B7 produced high levels of biologically active IL-12. In situ delivery of DC/IL-12 or DC/IL-12/B7 induced a significant suppression of primary tumor growth compared to DC/beta gal controls (P=.0328 and P=.0019, respectively), as well as reduced numbers of spontaneous lung metastatic nodules (P=.1404 and P=.0335, respectively). In survival experiments, in situ DC/IL-12 injection demonstrated a small but statistically significant advantage (P=.0041). Subcutaneous, tumor lysate pulsed DC/IL-12 significantly decreased tumor size (P=.0152) and increased survival (P=0.0433) compared to HBSS controls but the decrease in the number of spontaneous lung metastases did not achieve statistical significance. Both in situ and subcutaneous treatments enhanced cytolytic activities of natural killer (NK) cells and cytotoxic T lymphocytes (CTL). In this preclinical model, gene-modified DC-based intratumoral immunotherapy was shown to be an effective therapeutic strategy for locally advanced prostate cancer based on tumor growth suppression, inhibition of metastasis and survival improvement.

Chemokine gene modification of human dendritic cell-based tumor vaccines using a recombinant adenoviral vector

Previous animal studies conducted in our laboratory have shown that tumor antigen-pulsed dendritic cells (TP-DC) can mediate antitumor effects in vivo. However, durable and complete regression of established tumors has been difficult to achieve through the administration of TP-DC alone. To better augment immune priming to tumors in vivo, we have hypothesized that it is necessary to achieve an increased number of host-derived, naïve T cells at the site of TP-DC vaccine injections. To accomplish this goal, we have embarked on a series of studies that utilize defined chemokines. One of these molecules, secondary lymphoid tissue chemokine (SLC), has been shown to be uniquely chemoattractant for naïve T cells and dendritic cells. We propose that gene modification of DC-based tumor vaccines to produce human SLC will enhance T-cell recruitment and immune priming to tumor-associated antigens, and thereby translate into improved antitumor vaccine efficacy in vivo. Utilizing an E1-, E3-deleted adenoviral vector containing the gene for human SLC, we have been able to transduce human DC to produce biologically active human SLC that chemoattracts human T cells in vitro. SLC production by transduced DC was markedly enhanced upon DC maturation. Additionally, these SLC-secreting DC were found to be viable to a large extent despite the cytopathic effect inherent in adenoviral gene transfer and, most importantly, functional as determined by their ability to prime autologous T cells to a known melanoma-associated antigen, MART-1. Based on these encouraging results, we plan to initiate Phase I clinical studies utilizing DC-SLC to treat patients with advanced solid tumors.

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.

Human dendritic cell maturation by adenovirus transduction enhances tumor antigen-specific T-cell responses

Dendritic cells (DCs) have been shown to require a degree of maturation to stimulate antigen-specific, type 1 cytotoxic T lymphocytes in numerous murine models. Limited data in humans suggest that immature DCs (DC) can induce tolerance, yet a variety of nonmatured DC used clinically have induced antigen-specific type 1 T cells in vivo to various tumor-associated antigens. Use of adenovirus to engineer DCs is an efficient method for delivery of entire genes to DC, but the data on the biologic effects of viral transduction are contradictory. The authors demonstrate that DCs transduced with adenovirus (AdV) clearly become more mature by the phenotypic criterion of upregulation of CD83 and downregulation of CD14. Transduced DCs also decrease production of IL-10, and a subset of transduced DCs produce increased levels of IL-12 p70. This level of maturation is superior to that achieved by treatment of these cells with tumor necrosis factor-alpha or interferon-alpha but less pronounced than with CD40L trimer or CD40L + interferon-gamma. Maturation by AdV transduction alone leads to efficient stimulation of antigen-specific T cells from both healthy donors and patients with advanced cancer using two defined human tumor-associated antigens, MART-1 and AFP. Given the pivotal role of DCs in immune activation, it is important to understand the direct biologic effects of AdV on DCs, as well as the impact these biologic changes have on the stimulation of antigen-specific T cells. This study has important implications for the design of DC-based clinical trials.

Overexpression of CCL-21/secondary lymphoid tissue chemokine in human dendritic cells augments chemotactic activities for lymphocytes and antigen presenting cells

BACKGROUND

Ex vivo generated dendritic cells (DC) genetically modified to express secondary lymphoid tissue chemokine (CCL-21/SLC) have been shown to stimulate potent antitumor responses in murine models. When injected intratumorally, CCL-21 colocalizes DC and lymphocyte effector cells at the tumor site. This may improve tumor antigen presentation and T cell activation by utilizing the tumor as an in vivo source of antigen for DC. In order to develop DC-based cancer therapies for intratumoral injection that could promote tumor antigen uptake and presentation in situ, we constructed and characterized an adenoviral vector that expresses human CCL-21 (AdCCL-21).

RESULTS

Human monocyte derived DC were cultured in GM-CSF and IL-4 for 6 days. Following AdCCL-21 transduction, CCL-21 protein production was assessed by ELISA on day 8. DC transduced with AdCCL-21 at multiplicities of infection (MOIs) of 50:1 or 100:1 produced up to 210 +/- 9 ng/ml and 278 +/- 6.5 ng/ml /106 cells/48 hours, respectively. Following transduction, an immature DC phenotype was maintained and an upregulation of the costimulatory molecule, CD86 was noted. In addition, supernatant from AdCCL-21-DC caused significant chemotaxis of peripheral blood lymphocytes and mature DC.

CONCLUSIONS

These studies demonstrate that AdCCL-21-DC generate functional levels of CCL-21 without adversely altering DC phenotype. These findings strengthen the rationale for further investigation of AdCCL-21-DC as a DC-based therapy in cancer treatment.

Centrifugation facilitates transduction of green fluorescent protein in human monocytes and macrophages by adenovirus at low multiplicity of infection

Due to their phagocytic and poorly proliferative nature, it has been difficult to transfect human monocytes and macrophages. Adenoviral vectors have recently allowed transduction of a high percentage of human macrophages, but only after CSF upregulation of the integrins, alphavbeta3 or alphavbeta5, during culture for 48 h, a time allowing significant monocyte to macrophage differentiation. In our hands, after 24-h incubation with M-CSF (20 ng/ml) and a further 24-h incubation with an adenoviral vector encoding green fluorescent protein (AdV-GFP) [multiplicity of infection (MOI)=50:1], only 35% of CD14-positive cells express GFP. We report that centrifugation of these cells with AdV-GFP at 2000 x g for 1 h at 37 degrees C significantly enhanced the number of cells expressing GFP (to 65%) and the level of GFP expression per transduced cell (fivefold). The viability of the cells was not compromised (<5 % CD14-positive cells were 7-aminoactinomycin D (7AAD)-positive after 24 h AdV-GFP exposure at MOI=50:1). Centrifugation allowed efficient transduction of monocytes and macrophages with an MOI at least tenfold lower than otherwise required and did not activate the transduced cells or affect their ability to produce TNFalpha or IL-1beta in response to lipopolysaccharide (LPS). This methodology was also suitable for transducing large numbers of in vitro monocyte-derived macrophages (MDMac) and macrophages isolated from synovial fluids with up to 75-80% of CD14-positive cells transduced after 24-h exposure to AdV-GFP (50:1) and centrifugation (2000 x g). This methodology should provide significant expression of transgenes in human monocytes and macrophages.

Adenoviral interleukin-12 gene transduction into human bronchial epithelial cells: up-regulation of pro-inflammatory cytokines and its prevention by corticosteroids

BACKGROUND

One of the potential effects of IL-12 is to restore Th1/Th2 balance. Therefore, we investigated the possibility of developing a system for local delivery of IL-12 into the airways by examining protein expression in a human bronchial epithelial cell line (BEAS-2B) after adenoviral IL-12 gene transduction. The effects of dexamethasone on the gene-modified cells were also examined.

METHODS

Adenoviral vectors AxCAegfp and Ax1CIhp40ip35 were used to transduce enhanced green fluorescence protein and IL-12 genes, respectively, into BEAS-2B cells. Wild-type and IL-12 gene-transduced BEAS-2B cells were then incubated with or without dexamethasone, and concentrations of IL-12, IFN-gamma, IL-6, IL-8, granulocyte macrophage-colony stimulating factor and chemokines (TARC and RANTES) in the supernatant were measured by ELISA. IL-12 receptor expression was analysed by flow cytometry and RT-PCR.

RESULTS

The efficiency of transgene expression in BEAS-2B cells at a multiplicity of infection of 30 was approximately 80%. Gene-modified BEAS-2B cells produced biologically active IL-12, regardless of dexamethasone treatment. While IL-12 gene transduction led to increased production of IL-6 and IL-8 by BEAS-2B cells, expressions of these proteins were suppressed by dexamethasone. Addition of exogenous IL-12 failed to augment BEAS-2B cell IL-6 and IL-8 production, and IL-12 receptor expression by BEAS-2B cells was not detected.

CONCLUSIONS

Our findings suggest that adenoviral IL-12 gene transduction may be effective in inducing IL-12 expression in the airways, and could be a potential approach in the management of bronchial asthma.

Differential effects of IL-12 on the generation of alloreactive CTL mediated by murine and human dendritic cells: a critical role for nitric oxide

We examined the mechanisms involved in interleukin (IL)-12-mediated suppression of cellular immunity in mice using allogeneic mixed leukocyte reaction (MLR) stimulated by dendritic cells (DCs) in vitro and compared the effect of IL-12 on MLR in mice and humans. Although IL-12 stimulated human MLR, the addition of IL-12 or interferon-gamma (IFN-gamma) resulted in a dose-dependent suppression of MLR in mice. The treatment with N(G)-monomethyl-L-arginine (L-NMMA) completely abrogated IL-12- and IFN-gamma-mediated suppression of MLR in mice. Furthermore, IL-12 enhanced the alloreactive cytolytic T lymphocyte (CTL) induction in human MLR, whereas the addition of L-NMMA was required to generate alloreactive CTLs in the presence of IL-12 in mice. Nitric oxide (NO) was detected only in mouse MLR. Murine DCs could produce NO, but neither human CD34(+) cell- nor monocyte-derived DCs produced a detectable amount of NO. These results suggest that NO produced by DCs might play an important role in IL-12-mediated immune suppression in mice but not in humans.

Soluble Fas in malignant pleural effusion and its expression in lung cancer cells

Soluble Fas (sFas) has the ability to block Fas-mediated apoptosis, suggesting that sFas at tumor sites might inhibit tumor cell-killing by immune effector cells. We examined the sFas level in pleural effusion associated with lung cancer. The level of sFas in malignant pleural effusion was significantly higher than those in transudate and tuberculous pleural effusion. There was no significant difference in the sFas concentration among various histological types of lung cancer. The cytotoxicity mediated by anti-Fas agonistic antibody against Jurkat cells was inhibited by the addition of malignant pleural effusion, being inversely correlated with the sFas concentration. When Fas expression was examined using flow cytometry, eight of ten (80%) lung cancer cell lines expressed cell surface Fas. On the other hand, sFas protein and mRNA were detected in six of ten (60%) lung cancer cell lines, but there was no correlation between Fas and sFas expression. Furthermore, although the expressions of Fas and sFas were clearly detected in tumor cells derived from malignant effusion, the sFas expression was down-regulated in an in vitro culture. These results suggest that sFas in malignant pleural effusion is at least in part produced by lung cancer cells, and might play a role in local immunosuppression by tumor cells.

Dendritic cells infected with adenovirus expressing the thyrotrophin receptor induce Graves' hyperthyroidism in BALB/c mice

Dendritic cells (DCs) are the most potent antigen-presenting cells and a prerequisite for the initiation of primary immune response. This study was performed to investigate the contribution of DCs to the initiation of Graves' hyperthyroidism, an organ-specific autoimmune disease in which the thyrotrophin receptor (TSHR) is the major autoantigen. DCs were prepared from bone marrow precursor cells of BALB/c mice by culturing with granulocyte macrophage-colony stimulating factor and interleukin-4. Subcutaneous injections of DCs infected with recombinant adenovirus expressing the TSHR (but not beta-galactosidase) in syngeneic female mice induced Graves'-like hyperthyroidism (8 and 35% of mice after two and three injections, respectively) characterized by stimulating TSHR antibodies, elevated serum thyroxine levels and diffuse hyperplasitc goiter. TSHR antibodies determined by ELISA were of both IgG1 (Th2-type) and IgG2a (Th1-type) subclasses, and splenocytes from immunized mice secreted interferon-gamma (a Th1 cytokine), not interleukin-4 (a Th2 cytokine), in response to TSHR antigen. Surprisingly, IFN-gamma secretion, and induction of antibodies and disease were almost completely suppressed by co-administration of alum/pertussis toxin, a Th2-dominant adjuvant, whereas polyriboinosinic polyribocytidylic acid, a Th1-inducer, enhanced splenocyte secretion of IFN-gamma without changing disease incidence. These observations demonstrate that DCs efficiently present the TSHR to naive T cells to induce TSHR antibodies and Graves'-like hyperthyroidism in mice. In addition, our results challenge the previous concept of Th2 dominance in Graves' hyperthyroidism and provide support for the role of Th1 immune response in disease pathogenesis.

DNA-based immunotherapy: potential for treatment of chronic viral hepatitis?

Persistent HBV and HCV infection represent major causes of chronic liver disease with a high risk of progression to liver cirrhosis and hepatocellular carcinoma (HCC). Conventional protein-based vaccines are highly efficacious in preventing HBV infection; whereas in therapeutic settings with chronically infected patients, results have been disappointing. Prophylactic vaccination against HCV infection has not yet been achieved due to many impediments including frequent spontaneous mutations of the virus with escape from immune system control. Using animal models it has been demonstrated that DNA-based immunisation strategies may overcome this problem because of their potential to induce immunity against multiple viral epitopes. DNA-based vaccines mimic the effect of live attenuated viral vaccines, eliciting cell mediated immunity in addition to inducing humoral responses. Efficacy may further be improved by addition of DNA encoding immunomodulatory cytokines and more recently, direct genetic modulation of antigen-presenting cells, such as dendritic cells (DC), has been shown to increase antigen-specific immune responses. This review focuses on immunological aspects of chronic HBV and HCV infection and on the potential of DNA- and DC-based vaccines for the treatment of chronic viral hepatitis.

Human monocyte-derived and CD83(+) blood dendritic cells enhance NK cell-mediated cytotoxicity

Dendritic cells (DC) are known to be the most potent APC and to stimulate antigen-specific T cell responses. Recently it was reported that murine DC were also capable of modulating the innate immunity by stimulating NK cells through cell-to-cell contact. In the present study, we examined whether human DC could affect NK activity. Both monocyte-derived and CD83(+) blood DC were tested. The addition of DC to cultures of CD56(+) cells resulted in the significant dose-dependent enhancement of the killing activity against various NK-sensitive targets. The resultant activity was comparable to that induced by optimal concentrations of various cytokines, including IL-2, IL-12, IL-15 and IFN-gamma. Interestingly, DC enhanced the cytotoxicity of CD3(-)CD56(+) NK cells, but not that of CD3(+)CD56(+) T cells. Experiments using transwells clearly demonstrated that the enhancement of NK activity by DC was mediated by soluble factors produced by DC. The culture supernatants of DC also stimulated NK activity. The treatment of both DC and their supernatants with anti-human IL-12 or IL-18 antibodies did not block the enhancement of NK cell-mediated cytolysis by DC, indicating that other factor(s) produced by DC were responsible for the enhancement of NK activity. These results suggest that human myeloid DC can modulate innate immunity by enhancing NK activity.