Antigen-driven long term-cultured T cells proliferate in vivo, distribute widely, mediate specific tumor therapy, and persist long-term as functional memory T cells.

Mice bearing disseminated syngeneic FBL-3 leukemia were treated with cyclophosphamide plus long term-cultured T cells immune to FBL-3. The cultured T cells for therapy had been induced to grow in vitro for 62 d by intermittent stimulation with irradiated FBL-3. At the time of therapy, such antigen-driven long term-cultured T cells were greatly expanded in number, proliferated in vitro in response to FBL-3, and were specifically cytotoxic. Following adoptive transfer, donor T cells persisting in the host were identified and counted using donor and host mice congenic for the T cell marker Thy-1. The results show that antigen-driven long term-cultured T cells proliferated rapidly in vivo, distributed widely in host lymphoid organs, and were effective in tumor therapy. Moreover, the already rapid in vivo growth rate of donor T cells could be augmented by administration of exogenous IL-2. When cured mice were examined 120 d after therapy, donor L3T4+ T cells and donor Lyt-2+ T cells could be found in large numbers in host ascites, spleen, and mesenteric and axillary lymph nodes. The persisting donor T cells proliferated in vitro, and became specifically cytotoxic in response to FBL-3, demonstrating that antigen-driven long term-cultured T cells can persist long term in vivo and provide immunologic memory.

FBL-reactive CD8+ cytotoxic and CD4+ helper T lymphocytes recognize distinct Friend murine leukemia virus-encoded antigens.

Immunization of C57BL/6 (B6) mice with FBL, a Friend murine leukemia virus (F-MuLV), induces both tumor-specific cytolytic CD8+ (CTL) and lymphokine-producing CD4+ Th that are effective in adoptive therapy of B6 mice bearing disseminated FBL leukemia. The current study evaluated the F-MuLV antigenic determinants expressed on FBL that are recognized by FBL-reactive CD8+ and CD4+ T cells. To identify the specificity of the FBL-reactive CD8+ CTL, Fisher rat embryo fibroblast (FRE) cells transfected with plasmids encoding F-MuLV gag or envelope (env) gene products plus the class I-restricting element Db were utilized. FBL-reactive CTL recognized FRE target cells transfected with the F-MuLV gag-encoded gene products, but failed to recognize targets expressing F-MuLV env. Attempts to generate env-specific CD8+ CTL by immunization with a recombinant vaccinia virus containing an inserted F-MuLV env gene were unsuccessful, despite the generation of a cytolytic response to vaccinia epitopes, implying that B6 mice fail to generate CD8+ CTL to env determinants. By contrast, CD4+ Th clones recognized FRE target cells transfected with env and not gag genes, and immunization with the recombinant vaccinia virus induced an env-specific CD4+ T cell response. These data show that in a Friend retrovirus-induced tumor model in which tumor rejection can be mediated by either CTL or Th, antigens derived from discrete retroviral proteins are predominantly responsible for activation of each T cell subset.

The role of B cells for in vivo T cell responses to a Friend virus-induced leukemia.

B cells can function as antigen-presenting cells and accessory cells for T cell responses. This study evaluated the role of B cells in the induction of protective T cell immunity to a Friend murine leukemia virus (F-MuLV)-induced leukemia (FBL). B cell-deficient mice exhibited significantly reduced tumor-specific CD4+ helper and CD8+ cytotoxic T cell responses after priming with FBL or a recombinant vaccinia virus containing F-MuLV antigens. Moreover, these mice had diminished T cell responses to the vaccinia viral antigens. Tumor-primed T cells transferred into B cell-deficient mice effectively eradicated disseminated FBL. Thus, B cells appear necessary for efficient priming but not expression of tumor and viral T cell immunity.

Requirements for the generation of a Lyt-2+ T-cell proliferative response to a syngeneic tumor in the absence of L3T4+ T-cells.

Tumors may contain immunogenic antigens that are only recognizable in the context of class I, and not of class II, MHC molecules. Therefore, methods were developed to analyze the capacity of Lyt-2+ T-cells to respond to a syngeneic tumor in the absence of a contribution by L3T4+ T-cells. Conditions were defined in which purified Lyt-2+ T-cell populations, as well as L3T4+ T-cell populations, isolated from immune B6 spleen cells, could be induced to proliferate specifically in response to FBL, a retrovirally induced syngeneic tumor, without the addition of exogenous lymphokines. The purity of the subset responses was documented functionally by selective inhibition of the proliferative response of only the appropriate subset following addition of anti-Kb/Db or anti-I-Ab. The antigen and accessory cell (AC) requirements for triggering immune Lyt-2+ and L3T4+ T-cell populations were examined. The response of L3T4+ populations was predominantly specific for retrovirus envelope gp70, whereas Lyt-2+ populations predominantly recognized tumor antigens other than gp70, consistent with the hypothesis that some tumor antigens may be preferentially recognized by only class I- or class II-restricted T-cells. The FBL-stimulated proliferative response of each T-cell subset was dependent upon the presence of syngeneic AC. However, exogenous interleukin 1 was able to replace AC during the response of Lyt-2+ populations, whereas L3T4+ populations required AC also to biochemically process tumor-derived antigen and present it in the context of class II MHC molecules. The results suggest that under some conditions only the presence of AC or interleukin 1 may be limiting for the induction of antitumor responses by Lyt-2+ populations. These studies analyzed the ability to trigger purified Lyt-2+ T-cells in vitro following in vivo priming to tumor, and it remained possible that L3T4+ T-cells made an essential contribution during in vivo priming. Therefore, L3T4(+)-deficient mice were primed with FBL in vivo, and the Lyt-2+ T-cell response was assessed. Although priming was clearly less efficient in the absence of L3T4+ T-cells, Lyt-2+ T-cells from L3T4(+)-deficient mice proliferated and became cytolytically active following stimulation with FBL. Thus, under appropriate conditions, Lyt-2+ T-cells can generate an effective antitumor response in the absence of L3T4+ T-cells or exogenous lymphokines.

Monoclonal antibody therapy of murine lymphoma: enhanced efficacy by concurrent administration of interleukin 2 or lymphokine-activated killer cells.

Lymphokine-activated killer (LAK) cells have recently been shown to be very efficient effector cells for antibody-dependent cellular cytotoxicity. Thus, we explored, in a murine lymphoma model, administration of LAK-inducing doses of interleukin 2 (IL-2) or adoptive transfer of LAK cells as a means of enhancing therapy with tumor-specific monoclonal antibody (mAb). AKR/Cum (Thy-1.2+) hosts were inoculated on day 1 s.c. with the SL-2 thymoma of AKR/J origin (Thy-1.1+) and developed palpable tumor on day 4. Tumor-specific anti-Thy-1.1 IgG2a mAb, 1A14, was given on days 4 and 8 with 50,000 units/day IL-2 i.p. divided in two doses on days 4-12. Therapy with IL-2 or mAb alone had minimal activity, prolonging control median survival of 22 days to 25 and 29 days, respectively, whereas therapy with IL-2 plus mAb significantly prolonged median survival to 40 days. However, combined therapy did not result in cures and long term survival. The efficacy of combined therapy did not result from alterations in the biodistribution of mAb by concurrent IL-2 infusions, as determined by studies with radiolabeled mAb. The combined effect of in vitro generated LAK (10(8) cells) adoptively transferred i.v. with 1A14 on days 4 and 8 following SL-2 inoculation was also evaluated. This regimen had no detectable toxicity, and treatment of mice with LAK and mAb resulted in 60% long term survival compared with 17% or 0% for mice treated with mAb or LAK alone. Thus, the therapeutic effects of tumor-specific mAb was enhanced by in vivo administration of IL-2 or by adoptively transferred LAK, which may represent means to provide the host with increased antibody-dependent cellular cytotoxicity effector cells. Adoptively transferred LAK has the additional benefit of augmenting mAb therapy of tumor without the toxicity associated with the induction of such cells in vivo with high dose IL-2.

High-dose busulfan, melphalan, thiotepa and peripheral blood stem cell infusion for the treatment of metastatic breast cancer.

The purpose of this study was to determine the outcome of patients with metastatic breast cancer treated with high-dose busulfan (Bu), melphalan (Mel) and thiotepa (TT) followed by peripheral blood stem cell (PBSC) infusion. Fifty-one patients with chemotherapy refractory (n = 32) or responsive (n = 19) metastatic breast cancer received Bu (12 mg/kg), Mel (100 mg/m2) and TT (500 mg/m2) followed by PBSC collected after chemotherapy and growth factor (n = 43) or growth factor alone (n = 8). The 100 day treatment-related mortality was 8% including one death from cytomegalovirus pneumonia, one from aspiration pneumonia and two from regimen-related toxicity (RRT). Seven of 28 refractory (25%) and 5/7 (71%) responsive patients with evaluable disease achieved a complete response of all measurable disease or all soft tissue disease with at least improvement in bone lesions (PR*). Fifteen of 51 patients (29%) are alive and progression-free a median of 423 days (range 353-934) after treatment, 5/32 (16%) with refractory disease and 10/19 (53%) with responsive disease. The probabilities of progression-free survival (PFS) at 1.5 years for the patients with refractory (n = 32) and responsive (n = 19) disease were 0.24 and 0.53, respectively. These preliminary data suggest that high-dose Bu/Mel/TT has significant activity in patients with advanced breast cancer and may be superior to some previously published regimens.

Phase II study of high-dose busulfan, melphalan and thiotepa with autologous peripheral blood stem cell support in patients with malignant disease.

The purpose of this study was to determine the toxicities and potential effectiveness of high-dose busulfan, melphalan and thiotepa (Bu/Mel/TT) followed by autologous peripheral blood stem cell (PBSC) infusion in patients with a variety of diseases. A phase II clinical trial of Bu (12 mg/kg), Mel (100 mg/m2) and TT (500 mg/m2) followed by PBSC infusion in 104 patients with breast cancer (n = 48), malignant lymphoma (n = 25), ovarian cancer (n = 13), multiple myeloma (n = 7) and other malignancies (n = 11) was performed. Sixty-two patients were treated in an academic medical center and 42 in a community cancer center. Grade 3-4 regimen-related toxicities occurred in 14% of patients, causing regimen-related mortality in six (6%) patients with an overall transplant-related mortality of 9%. Transplant-related deaths occurred in 6/62 patients (10%) treated in an academic medical center and in 3/42 (7%) treated in a community cancer center. Complete remissions (CR) were achieved in 1/17 (6%) patients with refractory stage IV breast cancer, 4/4 patients with responsive stage IV breast cancer, 6/13 (46%) with more-advanced lymphoma and 4/4 with less-advanced lymphoma. These patients are alive and disease-free a median of 712, 279, 461 and 404 days after transplant, respectively. Nineteen of 22 patients with stage II-III breast cancer remain alive and disease-free a median of 365 days after transplant. Complete remissions were also seen in 4/9 patients with ovarian cancer and 3/7 with multiple myeloma. The Bu/Mel/TT regimen followed by autologous PBSC infusion is associated with acceptable morbidity and mortality, appears to have significant activity in patients with breast cancer and is well tolerated in the adjuvant setting of stage II-III breast cancer. Bu/Mel/TT also appears to have significant activity in patients with lymphoma, multiple myeloma and possibly ovarian cancer. Further phase II-III studies are warranted in patients with these and other malignancies.

Requirement for recognition of class II molecules and processed tumor antigen for optimal generation of syngeneic tumor-specific class I-restricted CTL.

The roles of Class II-restricted L3T4+ T cells and of accessory cells (AC) during the in vitro generation of Class I-restricted Lyt-2+ cytotoxic T cells (CTL) specific for a Class II-negative syngeneic tumor cell line, FBL, was examined. Treatment of responder FBL-immune spleen cells with alpha L3T4 plus complement before culture, as well as the direct addition of alpha L3T4 to cultures, diminished the generation of FBL-specific CTL. The contribution of L3T4+ cells could be completely replaced by the addition of exogenous cytokines. The data demonstrate that the optimal generation of FBL-specific Lyt-2+ CTL requires the presence of L3T4+ cells, presumably to provide necessary lymphokines. FBL-specific CTL could not be generated from purified FBL-immune T cells in the absence of AC. Syngeneic Ia+ macrophages (M phi), added at the initiation of culture, restored the response of purified T cells. Pretreatment of M phi with ammonium chloride or chloroquine, or the addition of monoclonal alpha I-Ab antibody at the initiation of culture, inhibited the ability of M phi to reconstitute the CTL response. Finally, the addition of exogenous helper factors could replace M phi and reconstitute the FBL-specific response of AC-depleted immune T cells. These results suggest that during the generation of Lyt-2+ CTL to a syngeneic tumor expressing only Class I MHC antigens, Ia+ AC are required to biochemically process antigen released from the tumor cells and present this modified antigen to Class II-restricted T helper cells.

Antigen-specific cultured T cells can mediate tumor therapy and provide long-term immunologic memory in vivo.

One goal of our research has been to define the principles necessary to utilize cultured T cells as reagents in vivo in order to augment specific T cell immunity and to utilize the augmented immunity as a form of cancer therapy. A potential barrier for the use of cultured T cells in vivo has been the previously demonstrated inability of cultured T cells to survive in vivo. As an example, studies to be reviewed below showed that a small precursor population of tumor-specific T cells could be grown to large numbers in vitro by repeated supplementation of media with exogenous Interleukin 2 (IL 2) and that the resultant long-term cultured T cells could mediate specific tumor therapy in vivo. However, T cells grown with IL 2 lost the ability to proliferate in response to immune stimulation by tumor antigen, became dependent upon exogenous IL 2 for survival, and thus died rapidly in vivo without repeated administration of exogenous IL 2. By contrast, T cells grown long-term in vitro in response to antigen-stimulation, as opposed to exogenous IL 2, were able to proliferate in vivo in response to stimulation by tumor antigen, mediate tumor therapy and persist long-term in vivo as functional memory T cells. Thus, the previously demonstrated inability of cultured T cells to survive and persist in vivo apparently resulted from the culture conditions utilized and did not reflect an intrinsic defect of all cultured T cells.

Il-4 is an endogenous T cell growth factor during the immune response to a syngeneic retrovirus-induced tumor.

The relative contributions of IL-2 and IL-4 during the immune response to the retrovirus-induced tumor, FBL, were examined. Both proliferative and cytolytic responses to FBL were measured and compared to similar responses to minor histocompatibility Ag. The addition of alpha IL-2 partially inhibited FBL-stimulated proliferation of purified L3T4+ T cells and nearly completely inhibited the response of Lyt-2+ T cells, whereas alpha IL-4 partially inhibited the proliferative response of the L3T4+ subset but had no effect on the response of the Lyt-2+ subset. The addition of exogenous IL-4 augmented the proliferative response of both subsets. Therefore, IL-4 is an endogenous growth factor for FBL-induced specific proliferation of the L3T4+ and not the Lyt-2+ population, but both subpopulations can respond to IL-4. Similar examination of anti-FBL CTL responses revealed that alpha IL-2, but not alpha IL-4, inhibited FBL-specific Lyt-2+ CTL generation. However, exogenous IL-4 partially replaced the L3T4+ Th cell activity necessary for optimal Lyt-2+ FBL-specific CTL generation. Therefore, IL-4 is not required but can participate in the CTL response. The role of IL-4 during the immune response of B6 mice to minor histocompatibility Ag disparate BALB.B cells was analyzed. alpha IL-4 had no detectable effect on the proliferative or cytolytic response to BALB.B cells, suggesting that endogenous IL-4 does not have a significant role in these responses. The extent of involvement of endogenous IL-4 in the T cell responses to retrovirus-induced tumor Ag and minor histocompatibility Ag presumably reflects the nature of the stimulating Ag, and detection of an IL-4 response may correlate with induction of an antibody response. Thus, the immunizing Ag and/or host B cell repetoire may influence which subsets of L3T4+ Th cells are activated during priming in vivo.

Helper-independent CD8+ cytotoxic T lymphocytes express IL-1 receptors and require IL-1 for secretion of IL-2.

The purpose of this study was to examine the role of IL-1 on the activation of CD8+/CD4- class I-restricted helper cell-independent cytolytic T cell (HITc) clones known to produce IL-2 and proliferate in vitro after Ag stimulation with a Friend retrovirus-induced leukemia (FBL). The functional role of IL-1 in Ag-specific proliferation and IL-2 secretion was assessed by stimulating the T cell clones with FBL either in the presence or absence of macrophages (M phi), rIL-1, or rIL-2. Resting cloned HITc cells, purified from residual accessory cells, failed to proliferate in response to FBL alone, but proliferated in response to FBL plus M phi, rIL-1 or rIL-2. Stimulation with FBL alone in the absence of M phi or IL-1 was sufficient for induction of IL-2R expression, and rendered cells responsive to IL-2, but M phi or IL-1 were also required to induce production of IL-2. The activity of IL-1 was further examined by measuring the binding of [125I]rIL-1 alpha, which demonstrated that resting cloned HITc cells expressed IL-1R that increased in number after activation with Ag. This expression of IL-1R and requirement for IL-1 by CD8+ HITc was surprising because previous studies examining T cell populations after mitogen stimulation have not detected IL-1R on the CD8+ population. Therefore, the role of IL-1 in the activation of CD8+ CTL that do not secrete IL-2 after activation was assessed. By contrast to HITc, CD8+ CTL required exogenous IL-2 to proliferate in vitro and did not express IL-1R. These data demonstrate that the subset of CD8+ T cells responsible for IL-2 production express IL-1R and that triggering this receptor with IL-1 after Ag stimulation results in the production of IL-2 and subsequent proliferation.

Eradication of disseminated murine leukemia by treatment with high-dose interleukin 2.

Interleukin 2 (IL 2) in high concentration induces lymphocytes to become nonspecifically cytolytic to a wide variety of tumor targets. We evaluated the therapeutic potential of such lymphokine-activated killer (LAK) cells in vivo and high-dose II 2 in vivo against disseminated murine leukemia. To quantitate the potential anti-leukemia effect of LAK cells in vivo, B6 mice were injected i.p. with graded doses of FBL-3 leukemia cells followed by LAK cells. In this Winn-type assay, 1 X 10(7) LAK cells were able to prevent the outgrowth of 1 X 10(2) FBL-3 cells in only 50% of mice and did not prevent the outgrowth of 1 X 10(6) tumor cells. Thus LAK cells, highly cytolytic to FBL-3 in vitro, mediated only a limited anti-tumor effect when applied directly to leukemia cells in vivo. LAK cells used as an adjunct to chemotherapy induced a small but non-curative effect against FBL-3, however. In this circumstance, LAK cells were markedly less effective than were immune spleen cells from mice previously sensitized to FBL-3. To test the anti-leukemia effect of high-dose IL 2 in vivo, B6 mice were inoculated with 5 X 10(6) FBL-3 cells followed by repeated doses of IL 2 at dose levels shown to induce LAK in vivo. "LAK-inducing" IL 2 doses on days 5 to 9 after FBL-3 inoculation, when tumor was disseminated, cured 50% of the mice. Treatment on days 5 to 9 was far more effective than on days 0 to 4, implying that the evolution of a host-tumor interaction was essential for the therapeutic effect of IL 2. Mice cured of FBL-3 by high-dose IL 2 were found to be immune to FBL-3, suggesting that tumor eradication resulted from a collaboration between LAK activity and tumor-specific immunity.

Antigen-driven T cell clones can proliferate in vivo, eradicate disseminated leukemia, and provide specific immunologic memory.

The aim of the current study was to determine the ability of antigen-driven cloned helper cell independent cytotoxic T lymphocytes (HITc) to proliferate and to survive in vivo and to mediate tumor therapy. The HITc clone utilized (denoted 1.B6) was specifically cytolytic to FBL-3, a syngeneic Friend virus-induced murine leukemia. Activation in vitro (48 hr) with FBL-3 induced secretion of interleukin 2 (IL 2), expression of IL 2 receptors (IL 2R), and in vitro proliferation. These cells could be "rested" for several weeks without stimulation, which resulted in reduced expression of IL 2R; however, restimulation with antigen resulted in reinduction of IL 2R and proliferation. The ability of cloned HITc to proliferate and to survive in vivo was examined in cyclophosphamide (CY) pretreated donor mice congenic for the Thy-1 gene. Adoptively transferred cloned HITc could be found in large numbers, and were widely distributed in vivo 1 wk after transfer. In tumor therapy, 1.B6 cells when injected into a site of tumor (i.p.) and used as an adjunct to CY were effective against disseminated FBL-3. In this circumstance, cloned 1.B6 cells could be recovered from cured mice 125 days after transfer and were shown to specifically lyse tumor and proliferate in vitro in response to FBL-3. Thus as an adjunct to CY, tumor-specific cloned HITc are capable of eradicating disseminated leukemia, persisting long-term in vivo, and providing specific immunologic memory.