Rapid recruitment of macrophages in interleukin-12-mediated tumour regression

Interleukin-37 mediates the antitumor activity in hepatocellular carcinoma: role for CD57+ NK cells

The biological role of interleukin-37 (IL-37) in cancer is large unknown. Through immunohistochemical detection using 163 primary hepatocellular carcinoma (HCC) clinical specimens, we found the expression of IL-37 was decreased in tumor tissues, and the expression level was negatively correlated with tumor size. High expression of IL-37 in HCC tumor tissues was associated with better overall survival (OS) and disease-free survival (DFS). IL-37 expression in tumor tissues was positively associated with the density of tumor-infiltrating CD57+ natural killer (NK) cells, but not with the CD3+ and CD8+ T cells. Consistently, in vitro chemotaxis analysis showed that IL-37- overexpressing HCC cells could recruit more NK cells. The in vivo mouse model experiments also revealed that overexpression IL-37 in HCC cells significantly delayed tumor growth and recruited more NK cells into tumors tissues. Our finding suggested that IL-37 might play an important role for the prognosis of HCC patients via regulating innate immune-action.

Intra-arterial interleukin-12 gene delivery combined with chemoembolization: anti-tumor effect in a rabbit hepatocellular carcinoma (HCC) model

BACKGROUND

Interleukin-12 (IL-12), a cytokine naturally secreted by activated dendritic cells and monocytes/macrophages, is known as a key anti-tumor agent in many tumor models, including hepatocellular carcinoma (HCC) models.

PURPOSE

To evaluate the anti-tumor effect of intra-arterial IL-12 gene delivery alone and in combination with transcatheter arterial chemoembolization (TACE) in rabbit VX2 liver cancer model.

MATERIAL AND METHODS

Rabbits with VX2 liver tumors were randomized into four groups, eight in each group. After laparotomy and insertion of a 30-gauge needle into the proper hepatic artery, the following interventional procedure protocols were applied: 0.9% saline solution (group A, control), TACE (group B, TACE alone, lipiodol + mitomycin), intra-arterial interleukin-12 gene infusion (group C, IL-12 alone), and intra-arterial interleukin-12 gene infusion in combination with TACE (group D, IL-12 plus TACE). Growth ratio was estimated by computed tomography. To analyze apoptotic index, tumor tissues were explanted for terminal deoxynucleotidyl transferase mediated dUTP nick end labeling (TUNEL) staining, 14 days after therapy.

RESULTS

Significant differences of the relative tumor growth ratio were observed in TACE alone group and IL-12 plus TACE group in comparison with control (P < 0.05, ANOVA, Tukey's HSD correction) but not between IL-12 alone and control, or IL-12 plus TACE group and TACE alone group (P > 0.05). Significant changes of the apoptotic index were observed in group D in comparison with remaining three groups (P < 0.05). The difference between group C and group A was not significant statistically (P > 0.05).

CONCLUSION

Intra-arterial interleukin-12 gene therapy combined with TACE has a potent anti-tumor effect in rabbit VX2 liver cancer in comparison with TACE alone.

Antitumor mechanism of recombinant murine interleukin-12 vaccine

This study was designed to establish an interleukin-12 (IL-12)-expressing murine Lewis lung carcinoma (LLC) cell vaccine (LLC/murine IL-12 [mIL-12]) and assess its antitumor efficacy and mechanism in vivo. The recombinant IL-12 plasmid was transfected into LLC cells and screened by G418, and positive clones were obtained. C57BL/6 tumor-bearing mouse model was established and tumor-bearing mice were randomly divided into three groups (n = 20), that is, treated with an intratumoral injection of phosphate-buffered solution, blank plasmid, or LLC/mIL-12 vaccine, respectively, at days 0, 7, and 14. Tumor size was measured before and after treatment. Tumor growth curve was plotted, cytolytic T lymphocyte (CTL) activity assay and natural killer (NK) cell activity assay were performed, CD4(+) and CD8(+) T lymphocyte were quantitated using flow cytometry, and the expression of interferon-gamma (IFN-gamma), IL-12, and interferon-inducible protein-10 (IP-10) in serum was detected by ELISA. Microvessel density was determined by immunohistochemistry after all mice were euthanized at day 21. The study revealed suppressed tumor growth, elevated levels of IFN-gamma, IP-10, and IL-12, augmented NK and CTL cell activities, and decreased microvessel density of tumor tissues. There were abundant CD4(+) and CD8(+) T lymphocyte infiltration in the vaccine group. This study demonstrated that the antitumor mechanism of LLC/mIL-12 vaccine was to promote IFN-gamma and IL-12 secretion, augment the NK and CTL cell activities, and decrease the microvessel density of tumors.

Immunohistochemical expression of interleukin-4, -6, -8, and -12 in inflammatory cells in surrounding invasive front of oral squamous cell carcinoma

BACKGROUND

Cytokines play important roles in the diverse interactions between tumor microenvironment and malignant cells. This study evaluated the association of interleukin (IL)-4, -6, -8, and -12 expressions and clinicopathologic parameters of 35 primary oral squamous cell carcinomas (OSCCs).

METHODS

Patients were staged according to the TNM clinical staging. Malignancy grading of invasive front was evaluated in hematoxylin-eosin (H&E)-stained slides. Immunohistochemical technique was performed on frozen tissue sections. Association between clinicopathologic parameters and IL expression were analyzed using nonparametric Kruskal-Wallis (alpha = 0.05) and Mann-Whitney U tests, with Bonferroni correction. Correlations between interleukins were analyzed by the Spearman coefficient.

RESULTS

Expression of ILs was verified in all samples; however, this finding was not related to clinicopathologic parameters. It was not the observed correlation between ILs.

CONCLUSIONS

Expression of IL-4, -6, -8, and -12 in the invasive front of OSCC is not involved with the clinicopathologic parameters of the disease.

Synergistic antitumor effects of 131I-LC-1 IgM and IL-12 vaccine on Lewis lung carcinoma

This study was designed to determine the antitumor effects of iodine-131 labeled monoclonal antibody LC-1 ((131)I-LC-1), interleukin-12 (IL-12) vaccine, or the combination of both on C57BL/6 mice bearing Lewis lung carcinoma (LLC) tumors. Tumor-bearing mice models were randomly divided into 4 groups that were respectively injected intratumorally with phosphate buffered solution (PBS), IL-12 vaccine gene therapy (GT), (131)I-LC-1 radioimmuno-therapy (RIT), or GT+RIT. Tumor volumes were measured before and after treatment. ELISA and RT-PCR determined the expression of IL-l2. LC-1 monoclonal antibody (Mab) was labeled with Na(131)I. Cytolytic T lymphocyte (CTL) activity assay, Natural Killer cell (NK) activity assay and apoptosis analysis were performed. Intratumoral (131)I-LC-1 injection leads to higher delivery of the antibody to the tumor. Tumor apoptosis occurred in the GT, RIT and GT+RIT groups. Tumor growth was inhibited in the GT, RIT and GT+RIT groups. Compared with other groups, the combination of GT+RIT up-regulated the expression of IL-l2 gene and inhibited the tumor growth more effectively than either GT or RIT alone (p<0.05). These results suggest that GT+RIT have the synergistic antitumor effects on tumor-bearing mice.

Differential regulation of antigen-specific CD8+ T cell responses by IL-12p40 in a dose-dependent manner

IL-12p40 is a natural antagonist which inhibits IL-12- and IL-23-mediated biological activity by blocking the binding of IL-12/23 to their receptors. Recently, IL-12p40 was also shown to have immune-enhancing activity through the activation of macrophages or dendritic cells. In this study, we investigated the effects of IL-12p40 as a genetic adjuvant on immune modulation using recombinant adenoviruses expressing IL-12p40 (rAd/IL-12p40) and OVA (rAd/OVA). Coimmunization of rAd/IL-12p40 at a low dose (1 x 10(4) PFU) with rAd/OVA resulted in OVA-specific immune enhancement, while a high dose of rAd/IL-12p40 (1 x 10(8) PFU) caused significant suppression of CD8(+) T cell responses. In addition, the enhancement and suppression of OVA-specific CD8(+) T cell responses correlated with antitumor activity against E.G7-OVA tumor challenge, which subsequently affected the survival rate. Moreover, the differential CD8(+) T cell response by IL-12p40 was still observed in IL-12Rbeta2 knockout (IL-12Rbeta2KO), but not in IL-12Rbeta1 knockout (IL-12Rbeta1KO) mice, indicating that IL-12p40 is a cytokine which can modulate Ag-specific T cell responses depending on IL-12Rbeta1. Our findings provide a novel insight on the physiological role of IL-12p40, which can be informative in the design of vaccine strategies and therapeutic regimens.

Induction of immunosuppressive molecules and regulatory T cells counteracts the antitumor effect of interleukin-12-based gene therapy in a transgenic mouse model of liver cancer

BACKGROUND/AIMS

Hepatocellular carcinoma (HCC) often lacks curative treatment; therefore new efficient therapies are needed. In this work we aimed at evaluating the antitumor effect of interleukin-12 (IL-12)-based gene therapy on HCC occurring spontaneously in mice.

METHODS

A plasmid-vector expressing IL-12 in a liver-specific and doxycycline (Dox)-inducible manner was transferred by hydrodynamic injection to the liver of L-PK/c-myc mice with HCC. IL-12 expression was induced by administering Dox (3 cycles of 1 month duration separated by 1 month rest).

RESULTS

Dox administration increased serum IL-12 and IFN-gamma and induced tumor lymphocytic infiltration in all treated mice which was accompanied by tumor stabilization or regression in 40% of animals. The antitumor effect did not correlate with levels of IL-12 or IFN-gamma nor with the intensity of tumor mononuclear infiltration. However, tumors from non-responder mice showed more abundance of Foxp3+ regulatory T cells and higher expression of the immunosuppressive molecules PD-1, PD-L1, VEGF, CTLA-4, IDO, and IL-10 than those that responded to therapy.

CONCLUSIONS

Although long-term induction of IL-12 expression in the liver can inhibit HCC growth, the efficacy of the treatment appears to be limited by the activation of immunosuppressive mechanisms.

Mice overexpressing p40 in lungs have reduced leucocyte influx and slightly impaired resistance during tuberculosis

Interleukin (IL)-12 (p70) is a heterodimeric cytokine composed of p40 and p35, that plays a major role in the protective immune response to Mycobacterium tuberculosis. To define the role of p40 in lungs during pulmonary M. tuberculosis infection we generated transgenic (Tg) mice overexpressing p40 under control of the surfactant protein C promoter. Tg mice expressed the transgene in their lungs, yet demonstrated elevated pulmonary p40 protein levels. After infection, Tg mice displayed higher pulmonary p40 and p70 levels than wild type mice. Interferon-gamma concentrations were similar in uninfected and infected Tg and wild type mice, arguing against agonistic effects of p40. Tg mice demonstrated reduced recruitment of macrophages, lymphocytes and neutrophils to the lungs early after infection. This was accompanied by reduced pulmonary tumour necrosis factor-alpha, macrophage inflammatory protein (MIP)-2 and MIP-1alpha levels. This suggests that elevated p40 concentrations inhibited the chemotactic effects of p70 on leucocytes. Furthermore, Tg mice displayed slightly higher pulmonary mycobacterial outgrowth late in the infection than wild type mice. Taken together, we demonstrate that constitutive overexpression of p40 in lungs negatively influences IL-12-mediated leucocyte migration and protection against lung tuberculosis. This suggests a novel antagonistic role for p40 homodimers in regulating the chemotactic bioactivity of IL-12 after pulmonary mycobacterial infection.

IL-12 deficiency transiently improves viral clearance during the late phase of respiratory tract infection with influenza A virus in mice

T helper 1-driven immune responses have been implicated in protective immunity against viral infections. Interleukin (IL)-12 is a heterodimeric proinflammatory cytokine formed by a p35 and a p40 subunit that can induce differentiation of naïve T cells towards a T helper 1-response. To determine the role of IL-12 in respiratory tract infection with influenza, p35 gene deficient (p35^−/−) and normal wild type mice were intranasally infected with influenza A virus. IL-12 p35^−/− mice displayed a transiently enhanced rather than an impaired viral clearance, as indicated by a 10-fold reduction in viral loads on day 8 after infection. Although interferon-γ levels were significantly lower in the lungs of IL-12 p35^−/− mice, their cellular immune responses were not altered, as reflected by similar T cell CD69 expression and influenza-specific T cell recruitment. Our data indicate that endogenous IL-12 impairs viral clearance during the late phase of influenza A virus infection in mice.

Sustained E2 antibody response correlates with reduced peak viremia after hepatitis C virus infection in the chimpanzee

Immune correlates of protection against hepatitis C virus (HCV) infection are not well understood. Here we investigated 2 naive and 6 immunized chimpanzees before and after intravenous challenge, 12 weeks after the last immunization, with 100 50% chimpanzee infectious doses (CID(50)) of heterologous genotype 1b HCV. Vaccination with recombinant DNA and adenovirus vaccines expressing HCV core, E1E2, and NS3-5 genes induced long-term HCV-specific antibody and T-cell responses and reduced peak viral load about 100 times compared with controls (5.91 +/- 0.38 vs. 3.81 +/- 0.71 logs, respectively). There was a statistically significant inverse correlation between peak viral loads and envelope glycoprotein 2 (E2)-specific antibody responses at the time of challenge. Interestingly, one vaccinee that had sterilizing immunity against slightly heterologous virus generated the highest level of E2-specific total and neutralizing antibody responses as well as strong NS3/NS5-specific T-cell proliferative responses. The other four vaccinees with low levels of E2-specific antibody had about 44-fold reduced peak viral loads but eventually developed persistent infections. In conclusion, vaccine-induced E2-specific antibody plays an important role in prevention from nonhomologous virus infection and may provide new insight into the development of an effective HCV vaccine.

Molecular and immunophenotypical characterization of progressive and regressive leukemia cell lines

The P815 and P198 cell lines are clonally related mouse mastocytoma cell lines. They differ in their biologic behavior in that P815 is a progressive tumor cell line, whereas P198 is a regressive one. These cell lines have been extensively used as models for the study of tumor-host relationships and tumor immunology. Although some of their biological properties have been well documented, the molecular mechanisms underlying tumor progression or regression have not been completely elucidated. In this study, we characterized the growth behavior and immunophenotype of these two cell lines, and analyzed their gene profiles using a complementary deoxynucleic acid (cDNA) microarray composed of 514 immunologically relevant genes. Our data showed that the two cell lines exhibited quite dissimilar and contrasting growth characteristics when inoculated into syngeneic mice. P815 tumors grew unremittingly, while P198 tumors gradually regressed. From a molecular viewpoint, P815 cells showed a higher expression of genes promoting tumor growth, such as IGF-1, IL-8R, FGFR1, VEGF-A, and VEGF-B. On the other hand, P198 tumor cells expressed CD11b and CD80, which favor the recruitment of lymphocytes and antigen-presenting cells (APCs), as well as the elicitation of antitumor immunity. P198 tumor cells also depicted a higher expression of genes inhibiting tumor growth, such as TNF-alpha, SOCS-1, CIS1, 4-1BB, and GDF-10. In conclusion, our results contribute further information in the understanding of the molecular mechanisms associated with the regression and progression of P815 and P198 tumor cells.

Administration route- and immune cell activation-dependent tumor eradication by IL12 electrotransfer

Injection of DNA via electric pulses into targeted tissues is referred to as electrotransfer. Intratumoral electrotransfer of the IL12 gene is more effective than intramuscular electrotransfer of the same gene in the eradication of established tumors. To understand the underlying immunological mechanisms, T cell infiltration, CTL activity, inhibition of angiogenesis, and transgene expression were analyzed using immunohistochemistry, fluorescence-based CTL analysis, Northern blot, and ELISA. In addition, the therapeutic effects of IL12 gene therapy were determined in immunocompetent, immune-cell-depleted, and immunodeficient mice. We found that intratumoral, but not intramuscular, electrotransfer of the IL12 gene induces CD8+ T cell infiltration, CTL activity, and tumor eradication. Tumor eradication by intratumoral IL12 gene electrotransfer requires both NK and T cells. The absence of either cell type will abrogate the intratumoral IL12 gene therapy-induced tumor eradication. Such a requirement explains why tumors cannot be eradicated by intramuscular electrotransfer of the IL12 gene. Only NK-cell-dependent, and not T-cell-dependent, anti-tumor effects are induced by intramuscular administration. Together, these results suggest that NK cells play an important role in both administration routes, mediating tumor growth inhibition, but T cells are specifically activated by intratumoral IL12 gene electrotransfer and not by the intramuscular route.

Tumor-infiltrating dendritic cell subsets of progressive or regressive tumors induce suppressive or protective immune responses

Tumor-infiltrating dendritic cells (TID) have an ambivalent role in regulation of tumor regression or growth. However, their precise natures and molecular mechanisms have not been elucidated. In this study, we studied TIDs recruited in progressive P815 and regressive P198 tumors of the same origin. Our data showed that P815 tumors contained CD4+ 8+ and CD4- 8- TID815 subsets, whereas P198 tumors contained CD4+ 8+ and CD4+ 8- TID198 subsets. They similarly stimulate allogeneic T cell proliferation and have nitric oxide-mediated cytotoxicity to tumor cells with an exception of CD4- 8- TID815 with less efficiency. The newly identified fourth CD4+ 8+ TID815 or TID198 subset and the CD4+ 8- TID198 all express high levels of IFN-gamma and interleukin (IL)-6, whereas CD4- 8- TID815 secrete a marked level of transforming growth factor-beta. Vaccination of mice with P815 tumor lysate-pulsed CD4+ 8+ TID815 or TID198 and CD4+ 8- TID198 induced IFN-gamma-secreting Th1 and effective CTL responses leading to protective immunity against P815 tumor, whereas CD4- 8- TID815 stimulated IL-10-expressing Tr1 responses leading to immune suppression. Transfer of CD4+ Tr1 cells obtained from CD4- 8- TID815-immunized wild-type, but not IL-10(-/-) mice, into CD4+ 8+ TID815 immunized mice abolished otherwise inevitable development of antitumor immunity. Taken together, our findings provide an important insight into immunologic alterations in progressive and regressive tumors and an implication for dendritic cell-based approaches in the design of cancer vaccines.

Efficient delivery of small interfering RNA for inhibition of IL-12p40 expression in vivo

Background

RNA interference is an evolutionary conserved immune response mechanism that can be used as a tool to provide novel insights into gene function and structure. The ability to efficiently deliver small interfering RNA to modulate gene expression in vivo may provide new therapeutic approaches to currently intractable diseases.

Methods

In vitro, siRNA targeting IL-12p40 was delivered to the murine macrophage cell line (J774A.1) encapsulated in a liposome with an IL-12 inducing agent (LPS/IFN-γ) over a number of time points. Controls included a variety of non-target specific siRNA reagents. Supernatants were analyzed for cytokine production while the cells were removed for mRNA profiling.

In vivo, siRNA-targeting IL-12p40 was delivered to the murine peritoneal cavity in a therapeutic fashion, after endotoxin (LPS) challenge. Cells from the peritoneal cavity were removed by lavage and analyzed by flow cytometry. Levels of IL-12 present in lavage and in serum were also examined by ELISA.

Results

In this report, we show that IL-12p40 siRNA can specifically silence macrophage expression of IL-12p40 mRNA and IL-12p70 protein in vitro. We extend this finding to demonstrate that delivery of liposome encapsulated siRNA targeting IL-12p40 to the murine peritoneal cavity can modulate an inflammatory stimulus in vivo. Furthermore, specific siRNA can be used therapeutically after endotoxin challenge to reduce both the local and systemic inflammatory response. Thus, the delivery of siRNA can be used to elicit specific non-permanent inhibition of endogenous protein expression.

Conclusion

In vitro silencing of IL-12p40 using siRNA at selected doses leads to specific knockdown of IL-12p70 protein production without inducing type I interferons. Furthermore, siRNA targeting murine IL-12p40 can be used therapeutically to counter an inflammatory response in vivo.

Paracrine release of IL-12 stimulates IFN-gamma production and dramatically enhances the antigen-specific T cell response after vaccination with a novel peptide-based cancer vaccine

Interleukin-12 can act as a potent adjuvant for T cell vaccines, but its clinical use is limited by toxicity. Paracrine administration of IL-12 could significantly enhance the response to such vaccines without the toxicity associated with systemic administration. We have developed a novel vaccine delivery system (designated F2 gel matrix) composed of poly-N-acetyl glucosamine that has the dual properties of a sustained-release delivery system and a potent adjuvant. To test the efficacy of paracrine IL-12, we incorporated this cytokine into F2 gel matrix and monitored the response of OT-1 T cells in an adoptive transfer model. Recipient mice were vaccinated with F2 gel/SIINFEKL, F2 gel/SIINFEKL/IL-12 (paracrine IL-12), or F2 gel/SIINFEKL plus systemic IL-12 (systemic IL-12). Systemic levels of IL-12 were lower in paracrine IL-12-treated mice, suggesting that paracrine administration of IL-12 may be associated with less toxicity. However, paracrine administration of IL-12 was associated with an enhanced Ag-specific T cell proliferative and functional response. Furthermore, paracrine IL-12 promoted the generation of a stable, functional memory T cell population and was associated with protection from tumor challenge. To study the mechanisms underlying this enhanced response, wild-type and gene-deficient mice were used. The enhanced immune response was significantly reduced in IFN-gamma(-/-) and IL-12R beta 2(-/-) recipient mice suggesting that the role of IL-12 is mediated, at least in part, by host cells. Collectively, the results support the potential of F2 gel matrix as a vaccine delivery system and suggest that sustained paracrine release of IL-12 has potential clinical application.

Mechanisms of macrophage cytotoxicity in IL-2 and IL-12 mediated tumour regression

IL-2 and IL-12 are promising anti-tumour agents. However, little attention has been paid to the role of macrophages during IL-2/IL-12 mediated tumour rejection. We studied the role of macrophages during IL-2/IL-12 mediated tumour rejection in DBA/2 mice bearing syngeneic SL2 lymphoma. Local treatment with IL-2 and IL-12 cured 85% of mice with severe metastasised tumour load. In vivo depletion studies showed that macrophages were required for the anti-tumour effect of IL-2 and IL-12. Macrophages could kill tumour cells both non-specifically and by antibody-dependent cellular cytotoxicity (ADCC). Treatment with IL-2, IL-12 or IL-2/IL-12 enhanced production of specific IgG1 immunoglobulins, while treatment with IL-12 and IL-2/IL-12 additionally induced IgG2a production. FcgammaRII and/or III were essential for ADCC expression after treatment with IL-2 and IL-12. These data show for the first time the essential role of macrophages during IL-2/IL-12 mediated tumour rejection and also suggest that IL-2 and IL-12 act via different mechanisms.

Dendritic cells: making progress with tumour regression?

Due to their potent ability to activate the immune system, dendritic cells (DC) are showing promise as potential adjuvants for tumour immunotherapy of cancer patients. However, little is known about the effect tumour cells can have on DC function. Indeed, the discovery of different DC subsets with different immunological functions indicates that the relationship between tumour cells and tumour-infiltrating DC subtypes is likely to be complex. There remains a lot to be understood about the effects of tumours on DC before we can expect to benefit from DC-based tumour immunotherapy of cancer patients. Here we review the recent advances being made in understanding DC phenotype and function in relation to interactions with different types of tumours.

Biodegradable polymer-based interleukin-12 gene delivery: role of induced cytokines, tumor infiltrating cells and nitric oxide in anti-tumor activity

The objective of this study was to investigate the role of induced cytokines, tumor infiltrating cells and nitric oxide (NO) in anti-tumor activity upon intratumoral injection of free and condensed plasmid DNA encoding murine interleukin-12 (pmIL-12) into BALB/c mice bearing subcutaneous tumors. Poly[alpha-(4-aminobutyl)-L-glycolic acid] (PAGA) was used for complex formation with pmIL-12 in presence of 5% (w/v) glucose. Upon characterization, PAGA/pmIL-12 (3/1, +/-) complexes were found to be most effective in gene transfer and were used consistently throughout this study. The levels of mIL-12 p70 and induced cytokines were determined by ELISA in the supernatant of the cultured tumors of the CT-26 subcutaneous tumor bearing BALB/c female mice 48 h after intratumoral injection of PAGA/pmIL-12 complexes and naked pmIL-12. The levels of IL-12, IFN-gamma, TNF-alpha and NO were higher for the PAGA/pmIL-12 complexes than those for the naked pmIL-12, PAGA alone and 5% glucose injected groups. The relative presence of natural killer (NK) cells, CD4(+) T cells, and antigen presenting cells, such as macrophages and dendritic cells determined using immunohistochemistry was higher for PAGA/pmIL-12 complexes compared with naked pmIL-12. The presence of CMV promoter in plasmid encoding IL-12 cDNAs did not induce any type I interferon response. There was a significant improvement in the survival rate and the inhibition of tumor growth after repeated injections of PAGA/pmIL-12 complexes.

Engineering N-glycosylation mutations in IL-12 enhances sustained cytotoxic T lymphocyte responses for DNA immunization

Interleukin-12 (IL-12), consisting of p40 and p35 subunits, produces both p70 heterodimer and free p40. p70 is essential for the induction of T-helper 1 (Th1) and cytotoxic T-cell (CTL) immunity, whereas p40 inhibits p70-mediated function. Here, we found that mutations introduced into N-glycosylation sites (N220 of murine p40 and N222 of human p40) reduced secretion of p40 but not p70. Co-immunization of N220 mutant mIL-12 gene with hepatitis C virus (HCV) E2 DNA significantly enhanced long-term E2-specific CD8+ T-cell response and protection against tumor challenge compared with that of wild type. Our results indicate that the ratio of p70 to p40 is important for generating sustained long-term cell-mediated immunity. Thus, the mutant IL-12 could be utilized for the development of DNA vaccines as an adjuvant for the generation of long-term memory T-cell responses.

Independent contributions of GR-1+ leukocytes and Fas/FasL interactions to induce apoptosis following interleukin-12 gene therapy in a metastatic model of prostate cancer

In a mouse model of prostate cancer, adenovirus-mediated interleukin-12 (Ad.mIL-12) gene therapy resulted in significant growth inhibition of both the injected primary tumor and synchronous metastases. Within 2 days of vector injection, two distinct patterns of apoptosis were detected within the primary tumor, the inhibition of which with a caspase inhibitor substantially negated growth suppression. The dominant pattern displayed localized sheets of apoptotic cells in close association with necrosis containing polymorphic neutrophils (PMNs). Depletion of PMNs resulted in the loss of this pattern of apoptosis and reduced growth suppression. A second major wave of growth suppression within the primary tumor was mediated by an immune response. Natural killer (NK) cell activity was detected within tumor-infiltrating lymphocytes (TIL) by the eighth day post-vector injection, the depletion of which resulted in a significant loss of survival enhancement. A more modest role for T cells was identified, which in the absence of documented cytotoxic T lymphocyte (CTL) activity may be related to a significant reduction in interferon-gamma (IFN-gamma) levels found in mice depleted of T cells, thereby reducing the secondary influences of IFN-gamma. However, depletion of NK cells or T cells had no discernible negative effect on IL-12-mediated anti-metastatic activity. Attention focused on the role of IFN-gamma, observed following Ad.mIL-12 therapy, to mediate the diffuse pattern of apoptosis seen in the primary and metastatic lesions. In vitro studies noted the ability of IFN-gamma to up-regulate tumor cell expression of Fas and FasL to mediate apoptosis, whereas in vivo blockage of Fas/FasL interactions with soluble Fas resulted in a modest reduction in primary tumor growth suppression but complete abrogation within metastatic lesions.

Positive regulatory role of IL-12 in macrophages and modulation by IFN-gamma

Similar to myeloid dendritic cells, murine macrophages and macrophage cell lines were found to express a surface receptor for IL-12. As a result, peritoneal macrophages could be primed by IL-12 to present an otherwise poorly immunogenic tumor peptide in vivo. Using binding analysis and RNase protection assay, we detected a single class of high affinity IL-12 binding sites (K(d) of approximately 35 pM) whose number per cell was increased by IFN-gamma via up-regulation of receptor subunit expression. Autocrine production of IL-12 was suggested to be a major effect of IL-12 on macrophages when the cytokine was tested alone or after priming with IFN-gamma in vitro. In vivo, combined treatment of macrophages with IFN-gamma and IL-12 resulted in synergistic effects on tumor peptide presentation. Therefore, our findings suggest a general and critical role of IL-12 in potentiating the accessory function of myeloid APC.

IL-12 Drives IFN-γ-Dependent Autoimmune Kidney Disease in MRL-Fas lpr Mice

IL-12 is secreted by kidney tubular epithelial cells in autoimmune MRL-Faslpr mice before renal injury and increases with advancing disease. Because IL-12 is a potent inducer of IFN-γ, the purpose of this study was to determine whether local provision of IL-12 elicits IFN-γ-secreting T cells within the kidney, which, in turn, incites injury in MRL-Faslpr mice. We used an ex vivo retroviral gene transfer strategy to construct IL-12-secreting MRL-Faslpr tubular epithelial cells (IL-12 “carrier cells”), which were implanted under the kidney capsule of MRL-Faslpr mice before renal disease for a sustained period (28 days). IL-12 “carrier cells” generated intrarenal and systemic IL-12. IL-12 fostered a marked, well-demarcated accumulation of CD4, CD8, and double negative (CD4−CD8− B220+) T cells adjacent to the implant site. We detected more IFN-γ-producing T cells (CD4 &gt; CD8 &gt; CD4−CD8− B220+) at 28 days (73 ± 14%) as compared with 7 days (20 ± 8%) after implanting the IL-12 “carrier cells;” the majority of these cells were proliferating (60–70%). By comparison, an increase in systemic IL-12 resulted in a diffuse acceleration of pathology in the contralateral (unimplanted) kidney. IFN-γ was required for IL-12-incited renal injury, because IL-12 “carrier cells” failed to elicit injury in MRL-Faslpr kidneys genetically deficient in IFN-γ receptors. Furthermore, IFN-γ “carrier cells” elicited kidney injury in wild-type MRL-Faslpr mice. Taken together, IL-12 elicits autoimmune injury by fostering the accumulation of IFN-γ-secreting CD4, CD8, and CD4−CD8− B220+ T cells within the kidney, which, in turn, promote a cascade of events culminating in autoimmune kidney disease in MRL-Faslpr mice.

A Novel Function of IL-12p40 as a Chemotactic Molecule for Macrophages

IL-12p70 plays a pivotal role in regulating the Th1/Th2 balance in the initial stage of immune responses. In contrast, IL-12p40, which is produced excess over IL-12p70, has been known to down-regulate IL-12p70-mediated responses by acting as an antagonist. To investigate in vivo function of IL-12p40, RH7777 rat hepatoma cells were engineered to inducibly express mouse IL-12p40 under the tight control of doxycycline (dox). In the absence of dox, s.c. injection of these cells into syngeneic rat was shown to generate tumors. However, the induction of IL-12p40 by dox was sufficient for inhibiting tumor formation, as well as for tumor regression. Immunohistochemical analysis showed that macrophages, but not CD4+ T, CD8+ T, and NK cells, were predominantly recruited into tumor sites as early as 3 days after IL-12p40 induction. These results were further supported by the observation that IL-12p40, but not C-terminal deletion mutants by more than 5 amino acids, was able to chemoattract peritoneal macrophages in vitro, suggesting that IL-12p40, when produced in a large excess over IL-12p70 in vivo, can initially amplify the immune responses against tumors by directly recruiting macrophages. Our findings indicate that IL-12p40 may function as an effector molecule as well as an antagonist of IL-12p70.