IL-15-induced CD8+CD122+ T cells increase antibacterial and anti-tumor immune responses: implications for immune function in aged mice

We previously proposed that mouse CD8(+)CD122(+) T cells and human CD57(+) T cells, which increase with age and exhibit potent IFN-gamma production, represent a double-edged sword as they play critical roles in host defense and the lethal IL-12/LPS-induced generalized Shwartzman reaction (GSR). However, our proposal was based solely on comparisons of young and old mice. In this study, we attempted to increase CD8(+)CD122(+) T cells in young mice with exogenous IL-15 and confirm their countervailing functions in young mice. After young mice (6 weeks) were injected with IL-15, they showed significant increases in CD8(+)CD122(+) T cells in the liver and spleen. Liver CD8(+)CD122(+) T cells from IL-15-pretreated mice had a potent capacity to produce IFN-gamma after IL-12 injection or Escherichia coli infection. IL-15-pretreated mice showed increased survival to E. coli infections and enhanced anti-tumor activities against liver metastatic EL4 cells, as well as an exacerbation of the GSR. Correspondingly, liver CD8(+)CD122(+) T cells produced more perforin than CD8(+)CD122(-) T cells in EL4-inoculated mice. Unexpectedly, comparable IL-15 treatment did not induce further increases in CD8(+)CD122(+) T cells in aged mice and did not enhance their defenses against bacterial infection or tumor growth. Interestingly, however, nontreated, aged mice (50 weeks) showed twofold higher IL-15 levels (but not TNF or IFN-gamma) in liver homogenates compared with young mice. Our results further support that CD8(+)CD122(+) T cells, which are increased physiologically or therapeutically by IL-15, are involved in antibacterial immunity, anti-tumor immunity, and the GSR.     

糖基化磷脂酰肌醇修饰的小鼠IL-21瘤苗抗肿瘤效应及其机制初探

目的 构建糖基化磷脂酰肌醇(glycosyl phosphafidylinositol,GPI)修饰的小鼠IL-21瘤苗,并对此瘤苗的抗肿瘤效应及其机制作初步探讨.方法 通过重叠PCR方法获得IL-21-GPI融合基因并将其插入空载体pcDNA3.1.将鉴定过的重组载体以脂质体法转染B16F10细胞制成瘤苗,细胞间接免疫荧光法及流式细胞仪检测转染瘤细胞膜表面IL-21的表达,通过对小鼠脾细胞的增殖作用鉴定表达的IL-21的生物学活性.将瘤苗接种小鼠后,通过观察小鼠肿瘤体积和生存率分析瘤苗的抗瘤性,并检测了瘤苗免疫鼠的细胞免疫活性.结果 正确构建了pcDNA3.1/IL-21-GPI重组载体,膜表达的IL-21有良好的生物学活性,制备的瘤苗能发挥抗肿瘤效应,其机制与免疫鼠细胞免疫活性增强有关.结论 成功构建了具有抗肿瘤活性的GPI修饰的IL-21瘤苗,为其进一步抗肿瘤免疫治疗研究奠定了基础.     

IFN-gamma-independent synergistic effects of IL-12 and IL-15 induce anti-tumor immune responses in syngeneic mice

IL-15 and IL-12 display anti-tumor activity in different models and IFN-gamma has been reported as a secondary mediator of both IL-12 and IL-15 effects. TS/A murine adenocarcinoma cells were engineered to secrete IL-12, IL-15 or both cytokines. TS/A cells secreting IL-15 (TS/A-IL-15) displayed a reduced tumorigenicity (50%) when implanted subcutaneously in syngeneic mice, while both TS/A-IL-12 and TS/A-IL-12/IL-15 were rejected by 100% of animals. In contrast, TS/A-IL-15 and TS/A-IL-12 were tumorigenic in syngeneic IFN-gamma knockout mice (100% and >90% of take rate, respectively), but TS/A-IL-12/IL-15 were completely rejected by 90% of these mice. All IFN-gamma-deficient mice rejecting TS/A-IL-12/IL-15 developed protective immunity against wild-type TS/A, as indicated by re-challenge experiments. Immunohistochemical analysis of the TS/A-IL-12/IL-15 tumor rejection area in IFN-gamma-deficient mice showed a marked reactive cell infiltration constituted of CD8+ cells, granulocytes, NK cells, macrophages and dendritic cells associated with the expression of IL-1beta, TNF-alpha, GM-CSF, MCP-1 and MIP-2. In vivo depletion experiments showed that rejection of TS/A-IL-12/IL-15 cells required CD8+ T lymphocytes and also involved granulocytes, while CD4+ and NK cells played a minor role. These data show IFN-gamma-independent synergistic anti-tumor effects of IL-12 and IL-15, involving CD8+ cells and secondary chemokines and cytokines, such as TNF-alpha.     

逆转录病毒介导的小鼠IL-23基因在小鼠结肠癌细胞中的表达及其抗肿瘤活性

目的：获得表达小鼠IL-23(mIL-23)基因的小鼠结肠癌细胞株。方法：应用逆转录病毒载体，将mIL-23基因导入小鼠结肠癌细胞株Colon26，经G418筛选后获得表达mIL-23的阳性细胞克隆(Colon26／IL-23)。用PCR和RT—PCR检测目的基因的表达，用ELISA法检测mIL-23的产生及mIL-23诱导的小鼠脾细胞IFN-γ的产生，用MTT比色法检测Colon26／IL-23细胞和Colon26细胞的体外增殖，将Colon26／IL-23细胞接种于BALB／c小鼠的右侧背部皮下，观察其致瘤性结果：建立了可表达mIL-23基因的小鼠结肠癌细胞株。分泌至培养上清中的IL-23，可诱导小鼠脾细胞产生IFN-γ在体外Colon26／IL-23细胞的生长与Colon26细胞无明显不同，但其在体内的致瘤性下降，具有抗瘤作用。结论：Colon6／IL-23细胞可分泌IL-23并证明其具有抗瘤活性。     

The CD40/CD40 ligand interaction is required for resistance to toxoplasmic encephalitis

Since the CD40/CD40 ligand (CD40L) interaction is involved in the regulation of macrophage production of interleukin 12 (IL-12) and T-cell production of gamma interferon (IFN-gamma), effector cell functions associated with resistance to Toxoplasma gondii, the role of CD40L in immunity to this parasite was assessed. Infection of C57BL/6 mice with T. gondii results in an upregulation of CD40 expression on accessory cell populations at local sites of infection as well as in lymphoid tissues. Splenocytes from C57BL/6 mice infected with T. gondii for 5 days produced high levels of IL-12 and IFN-gamma when stimulated with toxoplasma lysate antigen, and blocking CD40L did not significantly alter the production of IFN-gamma or IL-12 by these cells. Similar results were observed with splenocytes and mononuclear cells isolated from the brains of chronically infected mice. Interestingly, although CD40L(-/-) mice infected with T. gondii produced less IL-12 than wild-type mice, they produced comparable levels of IFN-gamma but succumbed to toxoplasmic encephalitis 4 to 5 weeks after infection. The inability of CD40L(-/-) mice to control parasite replication in the brain correlated with the ability of soluble CD40L, in combination with IFN-gamma, to activate macrophages in vitro to control replication of T. gondii. Together, these results identify an important role for the CD40/CD40L interaction in resistance to T. gondii. However, this interaction may be more important in the control of parasite replication in the brain rather than the generation of protective T-cell responses during toxoplasmosis.     

Central role of endogenous gamma interferon in protective immunity against blood-stage Plasmodium chabaudi AS infection

The role of endogenous gamma interferon (IFN-gamma) in protective immunity against blood-stage Plasmodium chabaudi AS malaria was studied using IFN-gamma gene knockout (GKO) and wild-type (WT) C57BL/6 mice. Following infection with 10(6) parasitized erythrocytes, GKO mice developed significantly higher parasitemia during acute infection than WT mice and had severe mortality. In infected GKO mice, production of interleukin 12 (IL-12) p70 and tumor necrosis factor alpha in vivo and IL-12 p70 in vitro by splenic macrophages was significantly reduced compared to that in WT mice and the enhanced nitric oxide (NO) production observed in infected WT mice was completely absent. WT and GKO mice had comparable numbers of total nucleated spleen cells and B220(+) and Mac-1(+) spleen cells both before and after infection. Infected WT mice, however, had significantly more F4/80(+), NK1.1(+), and F4/80(+)Ia(+) spleen cells than infected GKO mice; male WT had more CD3(+) cells than male GKO mice. In comparison with those from WT mice, splenocytes from infected GKO mice had significantly higher proliferation in vitro in response to parasite antigen or concanavalin A stimulation and produced significantly higher levels of IL-10 in response to parasite antigen. Infected WT mice produced more parasite-specific immunoglobulin M (IgM), IgG2a, and IgG3 and less IgG1 than GKO mice. Significant gender differences in both GKO and WT mice in peak parasitemia levels, mortality, phenotypes of spleen cells, and proliferation of and cytokine production by splenocytes in vitro were apparent during infection. These results thus provide unequivocal evidence for the central role of endogenous IFN-gamma in the development of protective immunity against blood-stage P. chabaudi AS.     

低免疫原性肿瘤可诱导调节性T细胞增生

目的以小鼠低免疫原性瘤细胞和高免疫原性瘤细胞与同系脾细胞混合培养为肿瘤免疫体外模型,研究培养后的脾细胞中CIM（＋）CD25（＋）调节性T细胞（TR）的分布,揭示肿瘤免疫逃逸的机制。方法3种不同高低免疫原性瘤细胞与同系脾细胞混合培养,建立模拟肿瘤免疫的体外模型,以放射性核素掺入法检测混合培养后的脾细胞的增殖,流式细胞术分析TR、CIM（＋）干扰素（IFN）γ（＋）以及CIM（＋）白细胞介素（IL）-10（＋）T细胞分布状况,ELISA法检测混合脾细胞和肿瘤细胞培养卜清液中IFN-1和IL-10水平。结果高免疫原性瘤细胞FBL3或H22刺激的同系脾细胞增殖指数较低免疫原性瘤细胞D5刺激的旧系脾细胞要高,分别高3倍（D5：FBL3=4．94：12．20）和10倍（D5：H22=4．94：44．60）,而3种瘤细胞刺激的同种脾细胞其增殖指数均较相应的肿瘤免疫组要高（D5 1．9倍,FBL3 2．1倍,H22 1．1倍）。在与低免疫原性瘤细胞D,混合培养的同系脾细胞中,与高免疫原性瘤细胞FBL3或H22相比,含更多的TR（D5：H22P〈0．05）和CD4^＋IL-10^＋细胞（D5：FBL3P〈0．01,D5：H22P〈0．01）,上清液中含更高水平的IL-10（P〈0．01,P〈0．01）,而IFN-γ水平很低（P〈0．01,P〈0．01）。结论低免疫原性肿瘤可诱导TR细胞的增生,TR细胞在肿瘤免疫逃逸中有重要作用。     

Differential requirement of perforin and IFN-gamma in CD8 T cell-mediated immune responses against B16.F10 melanoma cells expressing a viral antigen

Perforin-mediated lysis and secretion of IFN-gamma belong to the key effector functions of CD8 T cells. To compare the anti-tumor activity of these two mechanisms, we used B16.F10 melanoma cells (B16GP33) expressing the cytotoxic T cell epitope GP33 and T cell receptor transgenic (TCR-tg) mice specific for GP33 and deficient in perforin or IFN-gamma. B16GP33 tumor cells, injected either i.v. to induce experimental metastases or s.c., were similarly controlled in both wild-type and perforin-deficient, but not in IFN-gamma-deficient TCR-tg mice. A similar result was obtained when the therapeutic efficacy of adoptively transferred TCR-tg effector cells from these mice was examined in the corresponding perforin- or IFN-gamma-deficient C57BL/6 hosts. Criss-cross experiments further revealed that IFN-gamma production by the host strongly influenced the efficiency of the adoptively transferred effector cells. In contrast to the potent ability of GP33-specific effector cells to mediate B16GP33 tumor regression without perforin, GP33-specific memory cells, induced with recombinant vaccinia virus expressing GP33, failed to control B16GP33 tumor growth in the absence of perforin. In conclusion, our data demonstrate a crucial role for IFN-gamma in B16GP33 tumor cell elimination in vivo and indicate a differential requirement of perforin by effector versus memory CD8 T cells in anti-tumor immunity.     

An immunomodulatory arabinomannan extracted from Mycobacterium tuberculosis, Z-100, restores the balance of Th1/Th2 cell responses in tumor bearing mice

The regulatory effect of Z-100 on the balance of Th1/Th2 cell responses in BALB/c mice bearing Meth-A fibrosarcoma was investigated. In tumor bearing mice, Th1 cytokine production (IL-2, IFN-gamma) are suppressed and Th2 cytokine production (IL-4, IL-10) are increased, as compared with those of normal mice. The administration of Z-100 (10 mg/kg) to tumor bearing mice restored the balance of Th1/Th2 cell responses from Th2 dominant state to the normal state. This regulatory effect of Z-100 was eliminated by depletion of adherent cells from splenocytes derived from tumor bearing mice, and by the treatment with 2-ClAdo (a macrophage inhibitor). Similarly, this regulatory effect was diminished by the treatment with anti-IL-12 mAb and anti-IFN-gamma mAb. In addition, the IL-12 p40 mRNA expression in splenic adherent cells and IFN-gamma mRNA expression in CD4+ T cells were increased by the administration of Z-100 to tumor bearing mice. These results suggested that Z-100 restored the balance of Th1/Th2 cell responses to the normal one in tumor bearing mice through the activation of macrophages and up-regulation of IL-12 production from macrophages and IFN-gamma production from CD4+ T cells.     

IL-12基因联合CD40L基因治疗小鼠黑色素瘤的实验研究

目的：观察腺病毒介导的小鼠白细胞介素12基因（AdmIL-12）和CD40配体基因（AdmCD40L）对小鼠黑色素瘤的抗肿瘤效果。方法：利用B16细胞皮下注射C57BL/6小鼠建立小鼠黑色素瘤模型，单独或联合应用分别携带小鼠IL-12基因和CD40L基因的重组腺病毒进行直接瘤内注射治疗，观察小鼠皮下肿瘤生长及成活情况。采用乳酸脱氢酶释放法检测荷瘤小鼠脾细胞CTL活性变化。结果：AdmIL-12和AdmCD40L在体内外均能有效表达；AdmIL-12能显著抑制荷瘤小鼠皮下肿瘤的生长并明显延长其生存时间，能显著增强荷瘤小鼠的脾细胞CTL杀伤活性。AdmCD40L的抗瘤效果不明显，但与Ad-mIL-12联合应用可明显提高抗肿瘤效果。结论：腺病毒介导的mIL-12基因对小鼠黑色素瘤有显著的治疗效果，且与CD40L基因联合应用能进一步提高抗肿瘤效果。     

Improving recombinant MVA immune responses: potentiation of the immune responses to HIV-1 with MVA and DNA vectors expressing Env and the cytokines IL-12 and IFN-gamma

Recombinants based on vaccinia virus vectors, especially on the highly attenuated modified vaccinia virus Ankara (MVA) strain, are now being tested in clinical trials for safety and immunogenicity, using prime/boost heterologous regimes of vaccination. Due to the limited replication capacity of MVA, it is necessary to develop procedures that can enhance the specific cellular immune responses to the recombinant antigen delivered by the MVA vector. In this investigation, we have characterized the systemic immune responses in BALB/c mice using interferon-gamma (IFN-gamma) or interleukin-12 (IL-12) in an adjuvant-like manner elicited by MVA recombinants or naked DNA vectors expressing one of those cytokines in combination with the human immunodeficiency virus type 1 (HIV-1) envelope (Env) as antigen. In infected mice, virus gene expression in splenocytes and levels of cytokines IFN-gamma and IL-12 in serum were maximal by 6h post-infection (hpi) with MVA recombinants expressing IFN-gamma (MVAIFN-gamma) or IL-12 (MVAIL-12). In the infected animals, co-expression of HIV-1 env (MVAENV) and either IFN-gamma or IL-12 from MVA recombinants produced a two and three-fold increase of anti-env CD8+ T cell response, respectively. When priming was carried out with DNA vectors expressing HIV-1 env and either IFN-gamma or IL-12, the magnitude of the specific anti-env CD8+ T cell stimulation after MVAENV booster was further enhanced. Our findings revealed that IFN-gamma or IL-12 can be used to potentiate the cellular immune response to HIV-1 env, when delivered either from a single MVA recombinant or from a DNA vector. The increment of the CD8+ T cell response was higher in a DNA/MVA prime/boost protocol. Thus, the immune response of MVA vectors can be improved with the co-delivery of the cytokines IFN-gamma or IL-12.     

Loss of the innate immunity negative regulator IRAK-M leads to enhanced host immune defense against tumor growth

IRAK-M is a negative regulator of innate immunity signaling processes. Although attenuation of innate immunity may help to prevent excessive inflammation, it may also lead to compromised immune surveillance of tumor cells and contribute to tumor formation and growth. Here, we demonstrate that IRAK-M(-/-) mice are resistant to tumor growth upon inoculation with transplantable tumor cells. Immune cells from IRAK-M(-/-) mice are responsible for the anti-tumor effect, since adoptive transfer of splenocytes from IRAK-M(-/-) mice to wild type mice can transfer the tumor-resistant phenotype. Upon tumor cell challenge, there are elevated populations of CD4(+) and CD8(+) T cells and a decreased population of CD4(+) CD25(+)Foxp3(+) regulatory T cells in IRAK-M(-/-) splenocytes. Furthermore, we observe that IRAK-M deficiency leads to elevated proliferation and activation of T cells and B cells. Enhanced NFkappaB activation directly caused by IRAK-M deficiency may explain elevated activation of T and B cells. In addition, macrophages from IRAK-M(-/-) mice exhibit enhanced phagocytic function toward acetylated LDL and apoptotic thymocytes. Collectively, we demonstrate that IRAK-M is directly involved in the regulation of both innate and adaptive immune signaling processes, and deletion of IRAK-M enhances host anti-tumor immune response.     

Interleukin-12 and B7.1 co-stimulation cooperate in the induction of effective antitumor immunity and therapy of established tumors

Interleukin-12 (IL-12) promotes specific and long-lasting anti-tumor immunity mediated by T cells in a variety of murine tumor models. IL-12 also synergizes with B7.1 (CD80) co-stimulation to induce proliferation and cytokine production by both human and murine T cells in vitro. We evaluated the combined antitumor efficacy of IL-12 and B7.1 gene delivery in two apparently poorly immunogenic tumor models (TS/A and MCA207). In both of these models, expression of B7.1 and production of IL-12 in the inoculum led to improved anti-tumor immunity, with up to 80% long-term tumor-free animals (vs 0– 20% of mice remaining tumor free when inoculated with either B7.1- or IL-12-transfected tumors alone). Tumor-free mice were capable of rejecting a subsequent rechallenge with the wild-type tumor in 66% of the cases. Cooperativity was dependent upon the level of IL-12 secreted by engineered cells. IL-12 delivery required B7 expression of therapeutic effects to be observed in these models. Vaccines provided at a site distal to a control, non-transfected tumor slowed (TS/A) or abrogated (MCA207) the progression of wild-type tumors. The synergistic anti-tumor effects associated with combined application of B7.1- and IL-12-transfected tumors were partially negated by systemic administration of the CD28-B7.1/B7.2 antagonist CTLA4-Ig or by inoculation with neutralizing antibodies directed against murine interferon-γ or tumor necrosis factor-α, two cytokines elicited in response to IL-12 stimulation. These data support the potential clinical utility of combined gene therapy using IL-12- and B7.1-engineered autologous cells (tumor or fibroblasts) as a vaccine to elicit specific anti-tumor immunity.     

抗CD4单抗增强抗CD3单抗／IL—2活化的肿瘤特异性T细胞的抗瘤活性

目的探讨抗CD4mAb增强抗CD3mAb刺激的肿瘤特异性T细胞增殖和杀瘤活性的作用。方法将肿瘤细胞免疫的小鼠脾细胞,采用4种不同的方案培养1单独加2×104U/LrIL2IL2组2单独加抗CD3mAb抗CD3组3加抗CD3mAb48h后,再加入抗CD3mAb和2×104U/LrIL2抗CD3 IL2组4同时加抗CD3mAb和抗CD4mAb48h后,再加入抗CD3mAb、抗CD4mAb和2×104U/LrIL2抗CD3 IL2 抗CD4组。然后分别检测4组效应细胞的增殖水平、杀瘤活性及表型。结果抗CD3 IL2组细胞的3HTdR掺入量在第6,12和20d分别为:22045、13986和1931;抗CD3 IL2 抗CD4组细胞的3HTdR掺入量在第6、12和20d,分别为46193、31047和7443,后者明显高于前者P0.05。在培养12d时,抗CD3 IL2组的细胞对FBL3细胞株的最大杀伤率为83.6%;抗CD3 IL2 抗CD4组细胞的最大杀伤率为91.7%。细胞表型:FACS分析表明,抗CD3 IL2 抗CD4组培养12d的细胞,99%以上为Thy1.2 细胞,且CD4 、CD25 细胞的百分率均高于抗CD3 IL2组。结论抗CD4mAb对抗CD3mAb刺激、IL2诱导的肿瘤特异性T细胞的增殖和杀瘤活性具有增强作用。     

Anti-tumor T cell response and protective immunity in mice that received sublethal irradiation and immune reconstitution

To test whether homeostasis-driven T cell proliferation in reconstituted lymphodepleted hosts would improve the therapeutic efficacy of tumor vaccines, normal mice and reconstituted lymphopenic mice (RLM; C57BL/6 mice rendered lymphopenic with sublethal total-body irradiation and reconstituted with naive splenocytes) were used in the vaccination and challenge experiments with weakly immunogenic F10 melanoma cells. Only limited protection was observed in vaccinated normal mice (16.7%), whereas significantly greater protection was induced in vaccinated RLM (63.2%). Protective immunity in RLM depended on CD8 T cells. Following vaccination, a significant increase in the percentage of CD44(hi)CD62L(lo) T cells was detected in the tumor vaccine-draining lymph node (TVDLN) of vaccinated RLM compared to that of vaccinated normal mice. After in vitro stimulation, effector T cells generated from TVDLN of vaccinated RLM produced more IFN-gamma than T cells from vaccinated normal mice, and contained more melanoma-specific T cells, as assessed by ELISA and intracellular cytokine staining. This study suggests that vaccination of reconstituted lymphopenic hosts could elicit superior anti-tumor immunity compared to normal hosts, highlighting the potential clinical benefit of performing tumor vaccination during immune reconstitution.     

CD154 inhibits tumor-induced apoptosis in dendritic cells and tumor growth.

We have recently demonstrated that murine and human tumors induce apoptosis of dendritic cells (DC). Here, we evaluated the effect of CD40 ligation on the survival of tumor-associated DC and tumor growth. Retroviral transduction of MC38 colon carcinoma cells with the CD154 gene resulted in inhibition of tumor growth. This effect was abrogated in IL-12 knockout mice. Immunohistochemical analysis revealed an increase in CD11c+ (N418) and CD8+ but not NLDC-145+ cells in CD154-transfected tumors in wild-type mice. This increase was less pronounced in IL-12-deficient mice. In vitro, overexpression of CD154 on tumor cells significantly decreased the level of tumor-induced DC apoptosis. Surprisingly, the CD154-induced protection of DC from tumor-induced apoptosis was IL-12 independent in vitro, suggesting an IL-12-dependent and an IL-12-independent mechanism of CD154-induced anti-tumor immunity. Thus, our data suggest a new strategy to improve immunotherapy of cancer by protecting DC from tumor-induced apoptosis.     

Evaluating strategies to enhance the anti-tumor immune response to a carbohydrate mimetic peptide vaccine

Carbohydrate mimetic peptides of tumor associated carbohydrate antigens (TACA) are T-cell-dependent antigens and, therefore, immunization with these surrogates is predicted to overcome the low immunogenicity of carbohydrate antigens. Consistent with this hypothesis, we show that among the potential immune cells involved, peptide immunization led to an increase in T-cell populations. While peptide mimetics may also function as TLR binding ligands, we did not observe evidence of involvement of NK cells. Examining tumor challenged animals, we observed that peptide immunization and not tumor cells rendered IL-12 responsiveness to T-cells, as T-cells from peptide-immunized mice produced IFN-gamma upon stimulation with IL-12. Cyclophosphamide administration enhanced the anti-tumor efficacy of the vaccine, which was achieved by enhancing T-cell responses with no effect on NK cell population. Prophylactic immunization of mice with a DNA construct encoding carbohydrate mimetic peptides indicated a specific role for the mimotope vaccine in anti-tumor immune responses. These data suggest a role for both CD4(+) and CD8(+) T-cells induced by mimotopes of TACA in protective immunity against tumor cells.     

Coadministration of an interleukin-12 gene and a Trypanosoma cruzi gene improves vaccine efficacy

We tested the immunogenicity of two Trypanosoma cruzi antigens injected into mice in the form of DNA vaccine. Immunization with DNA encoding dihydroorotate dehydrogenase did not confer protective immunity in all mouse strains tested. Immunization with DNA encoding trans-sialidase surface antigen (TSSA) protected C57BL/6 (H-2(b)) mice but not BALB/c (H-2(d)) or C3H/Hej (H-2(k)) mice against lethal T. cruzi infection. In vivo depletion of CD4(+) or CD8(+) T cells abolished the protective immunity elicited by TSSA gene in C57BL/6 mice. Enzyme-linked immunospot assay with splenocytes from T. cruzi-infected mice or TSSA gene-vaccinated mice identified an H-2K(b)-restricted antigenic peptide, ANYNFTLV. The CD8(+)-T-cell line specific for this peptide could recognize T. cruzi-infected cells in vitro and could protect naive mice from lethal infection when adoptively transferred. Coadministration of the interleukin-12 (IL-12) gene with the TSSA gene facilitated the induction of ANYNFTLV-specific CD8(+) T cells and improved the vaccine efficacy against lethal T. cruzi infection. These results reinforced the utility of immunomodulatory adjuvants such as IL-12 gene for eliciting protective immunity against intracellular parasites by DNA vaccination.     

Inducing long-term survival with lasting anti-tumor immunity in treating B cell lymphoma by a combined dendritic cell-based and hydrodynamic plasmid-encoding IL-12 gene therapy

In a previous study we showed that immunization with dendritic cells (DC) pulsed with idiotype (Id) fused with CD40 ligand (CD40L) could break the tolerance to Id which is expressed on B lymphoma cells and restored the responsiveness of T(h) cells, and, subsequently, induced IgG antibody response. However, this treatment had no therapeutic effect. In the present study, we found that using a hydrodynamic transfection-based technique, a high level of IL-12 production was noticed as early as 7 h after administering plasmid encoding IL-12 (pIL-12) and persisted at a detectable level for at least 9 days. In evaluating the efficacy of DC-based and/or IL-12 gene-based therapy in the treatment of 38C13 B cell lymphoma, it was found that either treatment alone was ineffective. However, a combined treatment induced 100% long-term survival. Furthermore, a long-lasting anti-tumor immunity was induced in these mice which resisted further tumor challenge at 58 days after initial inoculation. The surviving mice showed a strong IFN-gamma-producing T(h) cell response and humoral antibody response, but there were no detectable cytotoxic T lymphocytes. The antibody from the immune sera mediated a complement-dependent lysis of tumor cells that was tumor specific. Furthermore, immunization of mice with DC-based vaccine and pIL-12 treatment elicited higher levels of anti-Id IgG titer and an enhanced IgG2a response which increased the efficacy in mediating 38C13 tumor lysis. On examining the mechanism for this isotype change, we found that IFN-gamma production by CD4(+) T cells is not the only determining factor for achieving a successful therapy. DC-based treatment alone could induce the increase of IFN-gamma production, but lacked any therapeutic effect. The deciding factor appears to be the abrogation of IL-4 production that was achieved by combing with IL-12 gene therapy. Our study provides a basis for exploring the combined use of cytokines or cytokine genes in DC-based treatment for achieving effective cancer immunotherapy.     

Cytokine gene therapy of mesothelioma. Immune and antitumor effects of transfected interleukin-12.

Malignant mesothelioma (MM) is a solid tumor of the mesothelium for which there is no curative treatment. MM appears to be sensitive to immunotherapeutic approaches, and one of the most powerful immunomodulatory cytokines with antitumor effects is interleukin (IL)-12. We have previously shown in a murine model of MM that systemic administration of recombinant IL-12 induces a potent anti-MM immune response. The nature and accessibility of MM tumors means that they are suitable candidates for direct cytokine and gene-transfer therapeutic approaches. Therefore, we undertook a study to assess the antitumor effects induced by the local production of IL-12 within MM tumors by transfecting a murine MM line with the genes for IL-12. The IL-12 transfectant (AB1-IL-12) did not produce tumors in normal mice, but did so in athymic nude mice, implicating T cells in the prevention of MM tumor growth. In mixing experiments, paracrine IL-12 production inhibited growth of untransfected MM cells provided that cells producing IL-12 represented more than 50-80% of the inoculum. Furthermore, BALB/c mice previously challenged with AB1-IL-12 were protected against rechallenge with parental AB1 tumor, indicating that the transfectant induced long-term immunity. AB1-IL-12 induced systemic immunity that was effective at reducing the incidence of parental AB1 tumor at a distal site, but its effects were dose-dependent. Though both CD4(+) and CD8(+) cells infiltrated the rejecting tumor, CD8(+) effector cells were essential for protection against development of parental AB1 tumor. This study shows that paracrine secretion of IL-12, generated by gene transfer, can induce immunity against MM that can act locally and also at a distant site. In addition, there was no evidence of toxicity, which has been associated with the systemic administration of IL-12, indicating that this cytokine is a good candidate for experimental gene therapy in MM.