Carol Vervaert

A phase I clinical trial of immunotherapy with interferon‐γ gene‐modified autologous melanoma cells

Tumor cells transduced with cytokine genes provide immunogenic vaccines for cancer immunotherapy.

Murine dendritic cells transfected with human GP100 elicit both antigen-specific CD8(+) and CD4(+) T-cell responses and are more effective than DNA vaccines at generating anti-tumor immunity.

Dendritic cells (DCs) are potent inducers of cytotoxic T lymphocytes (CTLs) when pulsed with an antigenic peptide or tumor lysate. In this report, we have used liposome‐mediated gene transfer to examine the ability of plasmid DNA encoding the human melanoma‐associated antigen gp100 to elicit CD8+ and CD4+ T‐cell responses. We also compared the efficacy between gp100 gene–modified DCs and naked DNA (pCDNA3/gp100)–based vaccines at inducing anti‐tumor immunity. DCs were generated from murine bone marrow and transfected in vitro with plasmid DNA containing the gp100 gene. These gp100‐modified DCs (DC/gps) were used to stimulate syngeneic naive spleen T cells in vitro or to immunize mice in vivo. Antigen‐specific, MHC‐restricted CTLs were generated when DC/gps were used to prime T cells both in vitro and in vivo. Thus, these CTLs were cytolytic for gp100‐transfected syngeneic (H‐2b) tumor MCA106 (MCA/gp) and vaccinia‐pMel17/gp100‐infected syngeneic B16 and MCA106, but not parental tumor MCA106 and B16, or gp100‐transfected allogeneic tumor P815 (H‐2d). Immunization with DC/gp protected mice from subsequent challenge with MCA/gp but not parental MCA106. Antibody‐mediated T‐cell subset depletion experiments demonstrate that induction of CTLs in vivo is dependent on both CD4+ and CD8+ T cells. Furthermore, DC/gp immunization elicits an antigen‐specific CD4+ T‐cell response, suggesting that DC/gps present MHC class II epitopes to CD4+ T cells. In addition, our data show that gene‐modified, DC‐based vaccines are more effective than the naked DNA‐based vaccines at eliciting anti‐tumor immunity in both prophylactic and therapeutic models. These results suggest that the use of DCs transfected with plasmid DNA containing a gene for TAA may be superior to peptide‐pulsed DCs and naked DNA‐based vaccines for immunotherapy and could provide an alternative strategy for tumor vaccine design. Int. J. Cancer 83:532–540, 1999.

Dendritic Cells Infected with a Vaccinia Vector Carrying the Human gp100 Gene Simultaneously Present Multiple Specificities and Elicit High-Affinity T Cells Reactive to Multiple Epitopes and Restricted by HLA-A2 and -A3

To investigate the ability of human dendritic cells (DC) to process and present multiple epitopes from the gp100 melanoma tumor-associated Ags (TAA), DC from melanoma patients expressing HLA-A2 and HLA-A3 were pulsed with gp100-derived peptides G9154, G9209, or G9280 or were infected with a vaccinia vector (Vac-Pmel/gp100) containing the gene for gp100 and used to elicit CTL from autologous PBL. CTL were also generated after stimulation of PBL with autologous tumor. CTL induced with autologous tumor stimulation demonstrated HLA-A2-restricted, gp100-specific lysis of autologous and allogeneic tumors and no lysis of HLA-A3-expressing, gp100+ target cells. CTL generated by G9154, G9209, or G9280 peptide-pulsed, DC-lysed, HLA-A2-matched EBV transformed B cells pulsed with the corresponding peptide. CTL generated by Vac-Pmel/gp100-infected DC (DC/Pmel) lysed HLA-A2- or HLA-A3-matched B cell lines pulsed with the HLA-A2-restricted G9154, G9209, or G9280 or with the HLA-A3-restricted G917 peptide derived from gp100. Furthermore, these DC/Pmel-induced CTL demonstrated potent cytotoxicity against allogeneic HLA-A2- or HLA-A3-matched gp100+ melanoma cells and autologous tumor. We conclude that DC-expressing TAA present multiple gp100 epitopes in the context of multiple HLA class I-restricting alleles and elicit CTL that recognize multiple gp100-derived peptides in the context of multiple HLA class I alleles. The data suggest that for tumor immunotherapy, genetically modified DC that express an entire TAA may present the full array of possible CTL epitopes in the context of all possible HLA alleles and may be superior to DC pulsed with limited numbers of defined peptides.

Pulsing of Dendritic cells with cell lysates from either B16 melanoma or MCA-106 fibrosarcoma yields equally effective vaccines against B16 tumors in mice

Background and Objectives: Dendritic cells (DC) pulsed in vitro with a variety of antigens have proved effective in producing specific antitumor effects in vivo. Experimental evidence from other laboratories has confirmed that shared antigens can be encountered in histologically distinct tumors. In our experiments, we set out to evaluate the immunotherapeutic potential of vaccines consisting of DC pulsed with MCA‐106 fibrosarcoma or B16 melanoma cell lysates and to determine whether a cross‐reactivity exists between the two tumors.

Retrovirus‐Mediated Gene Transfer of the Human γ‐IFN Gene: A Therapy for Cancer

A retroviral vector-mediated gene transfer system was used to introduce m gamma-IFN and h gamma-IFN genes into mouse and human tumor cells, respectively. Murine tumor cell lines and primary human melanoma tumor cells were successfully transduced with gamma-IFN vector, and these transduced cells secreted measurable levels of biologically active m gamma-IFN and h gamma-IFN, respectively. Both murine and human tumor cell lines that expressed gamma-IFN exhibited increased surface expression of HLA class I antigens when tested by Western blot and FACS analysis. gamma-IFN--transduced human melanoma cells were more active in stimulating tumor-specific cytolytic activity of CTLs from melanoma patients in vitro. m gamma-IFN--transduced tumor cells were substantially less tumorigenic than the corresponding parent tumor cell lines in immune-competent mice. In addition, injection of m gamma-IFN--transduced tumor cells resulted in activation of tumor-specific CTL in vivo. We plan to use gamma-IFN--transduced autologous tumor cells to boost host immune responses as a potential therapy for human melanoma.

In vivo tumor localization using tumor-specific monkey xenoantibody, alloantibody, and murine monoclonal xenoantibody.

Specific in vivo localization of antibodies reactive with human melanoma cell membrane tumor associated antigens (TAA) has been attempted using congenitally athymic nude mice bearing subcutaneous human melanoma tumor xenografts as the experimental model. IgG fractions were prepared from each of several immune and control sera. Antimelanoma antibody sources included human alloantibody obtained from melanoma patients immunized against allogeneic melanoma cells, a monkey antiserum raised by immunization against a single human melanoma cell line, and a murine monoclonal antimelanoma antibody-secreting hybridoma cell line. Localization of these radiolabeled antibodies and of control IgG preparations to tumor tissue was determined by whole body scintigraphy and by differential tissue counting. Compared with the different control IgG preparations, each of the antimelanoma IgG preparations exhibited significant specific accumulation within the melanoma tissue. However, variation existed in the ability of each antimelanoma IgG to tumor preparation to localize despite attempts to control model parameters such as tumor source, vivo passage number and mass. This variation appears to reflect basic biologic differences between tumors in different animals and possibly differences in the antigen-binding capacities of each IgG preparation following radioiodination. This technique for tumor localization is very promising and has obvious potential for clinical application

Immunological memory induced by genetically transduced tumor cells

AbstractBackground: Recent studies have demonstrated the usefulness of gene-modified tumor cells for immunotherapy. Using the tumorigenic murine fibrosarcoma, MCA 106, we investigated the effects of localized interferon-γ (IFNg) secretion on tumorigenicity and on long-term memory. Methods: The murine IFNg (MuIFNg) gene was introduced into tumor cells. High and low IFNg-secreting clones were isolated. C57BL/6 mice were injected subcutaneously (s.c.) with either parental (P), high or low IFNg-secreting (H- or L-IFNg) cells, and tumor growth was assessed weekly. Spleens were harvested on different days postinjection (p.i.) to assess in vitro cytolytic activity. In parallel, tissues from injection sites were stained with macrophage-, CD4-, and CD8-detecting antibodies. Mice were injected s.c. with H-IFNg MCA106 tumor. After 150 days the animals were rechallenged s.c. with MCA106P in one leg and with irrelevant syngeneic tumor in the other. Results: Both P- and L-IFNg cells had similar growth, whereas the H-IFNg cells never grew. Only splenocytes from the H-IFNg animals showed in vitro CTL activity persisting until day 30 p.i. Histological data revealed a macrophage and CD4+ infiltrate much earlier in the H-IFNg group compared with the P group. Only the irrelevant, syngeneic tumor grew in animals previously injected with H-IFNg cells, whereas both P and irrelevant syngeneic tumors grew in controls. Conclusions: Transduction of MCA106 cells with the MuIFNg gene diminished in vivo tumorigenicity in proportion to the amount of IFNg secreted. Immunization with H-IFNg cells elicited a host response characterized by macrophages and CD4+ cells. Long-term tumor-specific memory was seen after immunization with H-IFNg cells.

Modulation of specific active immunization against murine melanoma using recombinant cytokines

Specific active immunization with tumour cells and IL-1beta or IL-2 was examined in a murine model. Mice were treated with irradiated B16 melanoma, IL-1beta or IL-2 only, or with B16 plus cytokines prior to i.v. challenge with viable B16. Lung metastases were recorded after 28 days. Treatment with cytokine alone was not protective. Treatment with B16 alone afforded moderate protection. Treatment with B16 in combination with either cytokine resulted in a significant level of B16 specific protection which was dependent on the dose of cytokine used. Multiple immunizations with B16 provided limited protection which was significantly improved with IL-2. Immunization with B16 in combination with both cytokines at doses that alone failed to enhance immunity resulted in significant protection, suggesting that the two cytokines act at least additively. These studies demonstrate the significant benefit of specific active immunization with tumour cells in combination with low doses of IL-1beta or IL2.

IMMUNOLOGICAL CONSEQUENCES OF TRANSPLANTING RAT INSULINOMAS

We investigated the genetics of transplanting a NEDH rat insulinoma in various donor-recipient combinations. The insulinoma survived indefinitely when it was transplanted in the NEDH strain. Mean survival times of 8.6 ± 1.2 and 3.3 ± 1.0 days were recorded in allogeneic and xenogeneic combinations, respectively. No prolongation of mean survival time was found when the rat insulinoma was first passed through the athymic nude mouse and then transplanted as either an allograft or xenograft. The findings of the major histocompatibility antigen (Ag-B7) on the original insulinoma and the tumor that had been passed through the nude mouse demonstrates no demonstrable loss of transplantation antigens during passage.

Transplantation of Insulinoma into the Diabetic Syrian Hamster

Syrian hamsters were rendered diabetic with intraperitoneal streptozotocin and were maintained in the diabetic state for a minimum of 14 days. A hamster islet cell tumor was transplanted subcutaneously with a prompt return of water intake (38 +/- 9.1 ml/day to 7.1 +/- 2.2 ml/day, mean +/- SD), urine glucose (4.8 +/- 0.84 g/day to less than 250 mg/day), urine output (37.4 +/- 10.9 ml/day to 7.6 +/- 2.1 ml/day), blood glucose (297 +/- 31.9 mg/dl to 87.6 +/- 28 mg/dl), and weight gain (1.0 to 0.8 g/day) to normal control levels. Histologic examination of the engrafted tumors revealed a well encapsulated tumor with no evidence of metastatic disease. The transplanted insulinomas maintained well differentiated histologic features without evidence of necrosis. Immunopathologic studies failed to reveal any evidence of either humoral or cell mediated immunity directed toward the allograft. Each animal was successfully transplanted with a 1 mm tumor explant. A single rodent tumor donor provided adequate material for engraftment for five recipients. The transplanted insulinomas maintained full functional and enzymatic capabilities. Similar studies utilizing the hamster insulinoma engrafted into the athymic nude mouse showed amelioration of the same diabetic symptomatology. Many of the technical difficulties encountered with whole organ and isolated islet transplantation encourages development of a more practical model. These experimental results suggest an alternative method for supplying the diabetic with an endogenous insulin source.