Augmentation of antitumor immunity by genetically engineered fibroblast cells to express both B7.1 and interleukin-7

Interleukin-7 and interleukin-15 for cancer

Interleukin 7 and 15 are considered powerful pro-inflammatory cytokines, they have the ability to destabilize chromosomes and induce tumorigenesis. Additionally, they can control malignancy proliferation by influencing the tumor microenvironment and immune system. Immunotherapy has been proposed as a treatment modality for malignancy for over a decade; the exact mechanisms of action and pathways are still under investigation. Interleukin 7 and 15 have been extensively investigated in hematological malignancies since their mode of action influences the stimulation of the immune system in a more direct way than other malignancies such as lung, melanoma, and breast, renal and colorectal cancer.

Harnessing the biology of IL-7 for therapeutic application

Interleukin-7 (IL-7) is required for T cell development and for maintaining and restoring homeostasis of mature T cells. IL-7 is a limiting resource under normal conditions, but it accumulates during lymphopaenia, leading to increased T cell proliferation. The administration of recombinant human IL-7 to normal or lymphopenic mice, non-human primates and humans results in widespread T cell proliferation, increased T cell numbers, modulation of peripheral T cell subsets and increased T cell receptor repertoire diversity. These effects raise the prospect that IL-7 could mediate therapeutic benefits in several clinical settings. This Review summarizes the biology of IL-7 and the results of its clinical use that are available so far to provide a perspective on the opportunities for clinical application of this cytokine.

Gene transfer of AIMP1 and B7.1 into epitope-loaded, fibroblasts induces tumor-specific CTL immunity, and prolongs the survival period of tumor-bearing mice

T helper type 1 (Th1) cell-mediated immune responses play various roles in cellular immunity, including inducing cytotoxic T lymphocytes (CTLs) and they have been shown to be crucial in cancer immunotherapy. Previously, we found that aminoacyl-tRNA synthetase-interacting multifunctional protein 1 (AIMP1) stimulated antigen-presenting cells to secrete IL-12, leading to enhanced Th1 cell responses. In this study, as a way of enhancing antigen-specific Th1 responses, mouse fibroblasts (H-2(b)) were genetically modified to express an AIMP1 and a costimulatory B7.1 (Fb/AIMP1/B7.1). Fb/AIMP1/B7.1 cells were then loaded with an ovalbumin epitope as a model antigen (Fb/AIMP1/B7.1/OVA), and tested to determine if they induced OVA-specific CTLs in C57BL/6 mice (H-2(b)). Immunization with Fb/AIMP1/B7.1/OVA cells induced strong cytotoxic activities against OVA-expressing EG7 tumor cells, but not against other H-2(b) tumor cells. The levels of the cytotoxic response in the immunized mice with Fb/AIMP1/B7.1/OVA cells were significantly higher than the responses in mice immunized with other cell constructs. CD8(+) T cells were a major cell-type of OVA-specific antitumor immunity induced by Fb/AIMP1/B7.1/OVA cells. Furthermore, treatment with Fb/AIMP1/B7.1/OVA cells significantly prolonged the survival period of EG7 tumor-bearing mice. These results indicate that AIMP1-secreting, epitope-loaded fibroblasts efficiently induce antigen-specific CTL responses in mice.

CD134 Costimulation Couples the CD137 Pathway to Induce Production of Supereffector CD8 T Cells That Become IL-7 Dependent

The TNFR superfamily members 4-1BB (CD137) and OX40 (CD134) are costimulatory molecules that potently boost CD8 and CD4 T cell responses. Concomitant therapeutic administration of agonist anti-CD137 and -CD134 mAbs mediates rejection of established tumors and fosters powerful CD8 T cell responses. To reveal the mechanism, the role of CD137 expression by specific CD8 T cells was determined to be essential for optimal clonal expansion and accumulation of effector cells. Nonetheless, dual costimulation induced production of supereffector CD8 T cells when either the specific T cells or the host alone bore CD137. Perhaps surprisingly, the total absence of CD137 prevented anti-CD134 augmentation of supereffector differentiation demonstrating an unappreciated link between these related pathways. Ultimately, it was reasoned that these powerful dual costimulatory responses involved common gamma family members, and we show substantial increases of CD25 and IL-7Ralpha-chain expression by the specific CD8 T cells. To investigate this further, it was shown that IL-7 mediated T cell accumulation, but importantly, a gradual and preferential effect of survival was directed toward supereffector CD8 T cells. In fact, a clear enhancement of effector differentiation was demonstrated to be proportional to the increasing amount of IL-7Ralpha expression by the specific CD8 T cells. Therefore, dual costimulation through CD137 and CD134 drives production and survival of supereffector CD8 T cells through a distinct IL-7-dependent pathway.

Treatment of squamous carcinoma in mice with a vaccine enriched for cells that induce immunity to squamous carcinoma--a new vaccination strategy

We report a new vaccination strategy for squamous cell carcinoma (SCC). The vaccine was prepared by transfer of unfractionated DNA-fragments (25 kb) from squamous carcinoma cells (KLN205, DBA/2 origin (H-2(d))) into LM mouse fibroblasts (C3H/He origin; H-2(k)), a highly immunogenic cell line. To enhance their nonspecific immunogenic properties, the fibroblasts were modified before DNA transfer to secrete IL-2 and to express additional allogeneic MHC class I determinants. As the transferred DNA integrates into the genome of the recipient cells, and is replicated as the cells divide, sufficient DNA to prepare the vaccine could be obtained from as few as 10(7) squamous carcinoma cells (4 mm tumor). Since only a small proportion of the transfected cell-population was expected to have incorporated genes specifying antigens associated with the squamous carcinoma cells (TAA), we devised a novel approach to enrich the vaccine for cells that induce immunity to the SCC. Aliquots of the transfected population were divided into 10 small pools (initial inoculums = 1 x 10(3)). We reasoned that if the starting inoculums were sufficiently small, then the distribution of highly immunogenic and weakly immunogenic cells in each pool would not be the same. Cells from individual pools were allowed to increase in number. A portion of the expanded cell populations were maintained frozen/viable for later recovery. The remaining portions were used to immunize naïve DBA/2 mice. Pools containing greater numbers of immunogenic cells were identified by 2 independent assays. Frozen aliquots of cells from the pool that stimulated immunity to the squamous carcinoma to the greatest extent were recovered and subdivided for additional rounds of immune selection. Enhanced immunity to squamous carcinoma mediated by CD8+ T cells was induced in tumor-bearing mice treated solely by immunization with the enriched cell-population.

The effect of a therapeutic dendritic cell-based cancer vaccination depends on the blockage of CTLA-4 signaling

Dendritic cells (DCs) were pulsed with the H-2K(b) binding OVA(257-264)-peptide (SIINFEKL), and used as one single-injection vaccine in combination with anti-CTLA-4 monoclonal antibody (mAb) to treat mice inoculated 3 days previously with 3x10(5) E.G7-OVA lymphoma cells. Neither DC vaccination nor CTLA-4 blockage alone prevented tumor growth in tumor challenged mice. In contrast, the combination of one vaccination and injection of anti-CTLA-4 mAb lead to rejection or retarded tumor growth in more than 60% of the mice. The OVA-transgene or the SIINFEKL-epitope was not lost in the progressing tumors of vaccinated mice, however, the highest degree of anti-SIINFEKL reactivity of host CTLs in an IFN-gamma ELISPOT assay was found only in mice showing complete tumor rejection. Vaccinated mice having rejected E.G7-OVA tumors were capable of rejecting subsequent challenges with 1x10(6) E.G7-OVA tumor cells, and later on these mice even rejected wild-type EL-4 tumor cells indicating that tumor epitope spreading takes place during the process of vaccination-induced E.G7-OVA rejection. In agreement with these observations, mice having rejected E.G7-OVA tumors showed long lasting CTL memory in spleen and bone marrow towards both the SIINFEKL-peptide and other EL-4-derived tumor rejecting epitopes.

Induction of persistent in vivo resistance to Mycobacterium avium infection in BALB/c mice injected with interleukin-18-secreting fibroblasts

Interferon-gamma (IFN-gamma) is closely associated with the generation of cell-mediated immunity and resistance to intracellular parasites. Interleukin-18 (IL-18) is known to strongly induce IFN-gamma production by T cells and natural killer (NK) cells. To determine whether the paracrine secretion of IL-18 can efficiently stimulate the resistance to Mycobacterium avium complex (MAC) infection, 3T3 fibroblasts were stably transfected to secrete bioactive IL-18 and their effects on MAC infection were investigated in genetically susceptible BALB/c mice, compared with that of free recombinant IL-18. Immunization with IL-18-secreting fibroblasts (3T3/IL-18) during intranasal infection with MAC resulted in a significant decrease in bacterial load of lung during the entire 8-week observation period, while rIL-18 reduced the bacterial load at initial 1 week but not by 8 weeks postinfection. Immunization with the 3T3/IL-18 cells induced and maintained significantly higher levels of cytotoxic activity and nitric oxide production by lung cells than those of rIL-18 immunization. Furthermore, lung cells in mice injected with the 3T3/IL-18 cells showed persistent production of IFN-gamma throughout the 8-week period, suggesting that the 3T3/IL-18 cells induced the resistance to MAC infection via IFN-gamma production. This work suggests that IL-18-secreting fibroblasts may serve as a vehicle for paracrine secretion of IL-18 in immunotherapy of MAC infection.

Enhancing antitumor by immunization with fusion of dendritic cells and engineered tumor cells

A novel approach for a dentritic cells (DCs)-based tumor vaccine was developed for the formation of hybrid-engineered J558 after fusion with DCs. To make the hybrid-tumor vaccine generate more efficient specific CTL cytotoxicity against wild-type tumor cells, we genetically engineered tumor cells with mIL-12 gene prior to the cell fusion. mIL-12 was detected at 870 +/- 60 pg/(10(5) cells/ml) in the culture supernatants and the fusion ratio was about 30% by the co-focal microscopic analysis. Vaccination of mice with DCs fused with engineered J558 induced more efficient tumor-specific CTL cytotoxicity against wild-type tumor cells in vitro and with efficient antitumor immunity in vivo. These results suggest that this approach of using DCs fused with engineered tumor cells could be applied in clinical settings of DCs-based cancer vaccines.

Evidence of a role for CD200 in regulation of immune rejection of leukaemic tumour cells in C57BL/6 mice

Increased expression of the molecule CD200 in mice receiving renal allografts is associated with immunosuppression leading to increased graft survival, and altered cytokine production in lymphocytes harvested from the transplanted animals. Preferential production of IL-4, IL-10 and TGFbeta occurs on donor-specific restimulation in vitro, with decreased production of IL-2, IFNgamma and TNFalpha. These effects are enhanced by simultaneous infusion of CD200 immunoadhesin (CD200Fc) and donor CD200 receptor (CD200r) bearing macrophages to transplanted mice. C57BL/6 mice do not normally resist growth of EL4 or C1498 leukaemia tumour cells. Following transplantation of cyclophosphamide-treated C57BL/6 with T-depleted C3H bone marrow cells, or for the EL4 tumour, immunization of C57BL/6 mice with tumour cells transfected with a vector encoding the co-stimulatory molecule CD80 (EL4-CD80), mice resist growth of tumour challenge. Immunization of C57BL/6 mice with EL4 cells overexpressing CD86 (EL4-CD86) is ineffective. Protection from tumour growth in either model is suppressed by infusion of CD200Fc, an effect enhanced by co-infusion of CD200r+ macrophages. CD200Fc acts on both CD4+ and CD8+ cells to produce this suppression. These data are consistent with the hypothesis that immunosuppression following CD200-CD200r interaction can regulate a functionally important tumour growth inhibition response in mice.

Induction of effective antitumor immune responses in a mouse bladder tumor model by using DNA of an alpha antigen from mycobacteria

One of the main objectives of cancer immunotherapy is the activation and increase in number of antitumor effector cells. Recently, genetically modified tumor cell vaccines have been proposed for elicitation of antitumor effector cells. Native alpha antigen (alpha Ag) (also known as MPT59 and antigen 85B) of mycobacteria, which cross-reacts among mycobacteria species, may play an important biological role in host-pathogen interaction because it elicits various helper T-cell type 1 immune responses. To assess the induction of antitumor immune responses by alpha Ag, mouse tumor cell lines transfected with cDNA of alpha Ag from Mycobacterium kansasii were established, and the possibility of producing a tumor cell vaccine for induction of antitumor effects was explored. Transfection of tumor cell lines with an alpha Ag gene lead to primary tumor rejection and the establishment of protective immunity to nontransfected original tumor cell lines in Mycobacterium bovis bacillus Calmette-Gurin (BCG)-primed and unprimed mice. Mice immunized with tumor cell lines transfected with the alpha Ag gene showed delayed-type hypersensitivity responses in vivo and proliferative responses together with induction of interferon-gamma of spleen cells against nontransfected wild-type tumor cell lines in in vitro experiments. Moreover, immunization of mice with alpha Ag-expressing tumor cells elicited tumor-specific and cytotoxic T lymphocyte (CTL) epitope peptide-specific CD8+ CTLs. The results of this study provided evidence of the potential usefulness of alpha Ag in tumor cell vaccines.