Adoptive immunotherapy of advanced tumors with CD62 L-selectin(low) tumor-sensitized T lymphocytes following ex vivo hyperexpansion

Requirement of Innate Immunity in Tumor-Bearing Mice Cured by Adoptive Immunotherapy Using Tumor-Draining Lymph Nodes

BACKGROUND

The purpose of this study was to determine the cellular effectors of both the adoptively transferred cells and the tumor-bearing host that participate in the antitumor response to adoptive immunotherapy using culture-activated tumor-draining lymph nodes (TDLNs).

METHODS

TDLNs harvested from mice with 4T1 carcinoma cells were fractionated to derive the L-selectin(low) subpopulation and activated ex vivo prior to in vitro cytokine release assays and adoptive transfer into BALB/c mice bearing 3-day established subcutaneous tumors. Tumor-bearing recipients were SCID (lacking T, B, and NK cells), Rag2 deficient (lacking T and B cells), and wild-type BALB/c mice.

RESULTS

Culture-activated L-selectin(low) 4T1 TDLN from BALB/c mice secreted significant levels of interferon-gamma in response to 4T1 but not control tumor cells in vitro. CD4 cells within the adoptively transferred effector cell population contributed significantly to the antitumor effect in vivo. Culture-activated L-selectin(low) TDLNs from BALB/c wild-type mice were able to cure Rag2 deficient but not SCID mice bearing 4T1 subcutaneous tumors, suggesting a requirement of NK cells within the innate immune system of the tumor-bearing host during the antitumor response.

CONCLUSIONS

These results identify the cellular effectors involved in tumor regression following adoptive transfer and demonstrate the requirement for intact innate immunity within the tumor-bearing host.

Unraveling graft-versus-host disease and graft-versus-leukemia responses using TCR Vβ spectratype analysis in a murine bone marrow transplantation model

The optimum use of allogeneic blood and marrow transplantation (BMT) as a curative therapy for hematological malignancies lies in the successful separation of mature donor T cells that are host reactive and induce graft-versus-host disease (GVHD) from those that are tumor reactive and mediate graft-versus-leukemia (GVL) effects. To study whether this separation was possible in an MHC-matched murine BMT model (B10.BR→CBA) with a CBA-derived myeloid leukemia line, MMC6, we used TCR Vβ CDR3-size spectratype analysis to first show that the Vβ13 family was highly skewed in the B10.BR anti-MMC6 CD8(+) T cell response but not in the alloresponse against recipient cells alone. Transplantation of CD8(+)Vβ13(+) T cells at the dose equivalent of their constituency in 1 × 10(7) CD8(+) T cells, a dose that had been shown to mediate lethal GVHD in recipient mice, induced a slight GVL response with no concomitant GVHD. Increasing doses of CD8(+)Vβ13(+) T cells led to more significant GVL responses but also increased GVHD symptoms and associated mortality. Subsequent spectratype analysis of GVHD target tissues revealed involvement of gut-infiltrating CD8(+)Vβ13(+) T cells accounting for the observed in vivo effects. When BMT recipients were given MMC6-presensitized CD8(+)Vβ13(+) T cells, they displayed a significant GVL response with minimal GVHD. Spectratype analysis of tumor-presensitized, gut-infiltrating CD8(+)Vβ13(+) T cells showed preferential usage of tumor-reactive CDR3-size lengths, and these cells expressed increased effector memory phenotype (CD44(+)CD62L(-/lo)). Thus, Vβ spectratyping can identify T cells involved in antihost and antitumor reactivity and tumor presensitization can aid in the separation of GVHD and GVL responses.

Depletion of radio-resistant regulatory T cells enhances antitumor immunity during recovery from lymphopenia

Cytotoxic lymphodepletion therapies augment antitumor immune responses. The generation and therapeutic efficacy of antitumor effector T cells (T(E)s) are enhanced during recovery from lymphopenia. Although the effects of lymphodepletion on naive T cells (T(N)s) and T(E)s have been studied extensively, the influence of lymphodepletion on suppressor cells remains poorly understood. In this study, we demonstrate a significant increase of CD4(+)CD25(+)Foxp3(+) regulatory T cells (Tregs) in sublethally irradiated lymphopenic mice. These radio-resistant Tregs inhibited the induction of T(E)s in tumor-draining lymph-nodes (TDLNs) during recovery from lymphopenia. The transfer of T(N)s into lymphopenic tumor-bearing mice resulted in some antitumor effects; however, Treg depletion after whole-body irradiation and reconstitution strongly inhibited tumor progression. Further analyses revealed that tumor-specific T cells were primed from the transferred T(N)s, whereas the Tregs originated from irradiated recipient cells. As in irradiated lymphopenic mice, a high percentage of Tregs was observed in cyclophosphamide-treated lymphopenic mice. The inhibition of Tregs in cyclophosphamide-treated mice significantly reduced tumor growth. These results indicate that the Tregs that survive cytotoxic therapies suppress antitumor immunity during recovery from lymphopenia and suggest that approaches to deplete radio and chemo-resistant Tregs can enhance cancer immunotherapies.

T cells sensitized with breast tumor progenitor cell vaccine have therapeutic activity against spontaneous HER2/neu tumors

Cancer progenitor cells are critical for tumor initiation and recurrence so they are an important therapeutic target. We tested whether T cells could recognize tumor antigens expressed by breast cancer progenitor cells and acquire therapeutic activity against established metastases or delay onset of spontaneous tumors. Breast tumors were derived from HER2/neu transgenic mice and propagated in vitro under conditions that selected progenitor cells which were then used as an irradiated whole cell vaccine. A minor subset of recently sensitized T cells was isolated from vaccine-draining lymph nodes then activated in vitro to achieve numerical expansion. We show that the tumor progenitor cell vaccines reversed tolerance to a known HER2/neu epitope, otherwise inhibited by Treg cells. Additional shared tumor antigens were recognized because a Neuneg subclone also induced a Th1 type immune response against breast tumors. Adoptive transfer of in vitro activated lymph node T cells-mediated regression of established metastases from multiple independently derived breast tumor lines. Moreover, adoptive transfer of effector T cells into Neu-tolerant mice, months before the onset of spontaneous tumors, significantly postponed tumor development. Interestingly, T-cell-mediated lysis of metastases stimulated an IgG response to HER2/neu as well as other shared antigens. In summary, tumor progenitor cells contain shared antigens which can lead to a cross-protective T-cell response. Moreover, antigens acquired during immune-mediated tumor destruction are presented in a manner conducive to reversal of tolerance and Ig class switching. These complementary effector mechanisms might augment therapy by eliminating refractory breast cancer stem cells.

Antitumor activity of T cells generated from lymph nodes draining the SEA-expressing murine B16 melanoma and secondarily activated with dendritic cells

The successful use of tumor-draining lymph nodes (TDLN) as a source of effector cells for cancer immunotherapy depends largely on the immunogenicity of the tumor drained by the lymph nodes as well as the methods for secondary in vitro T cell activation and expansion. We transferred the bacterial superantigen staphylococcal enterotoxin A (SEA) gene into B16 murine melanoma tumor cells, and used them to induce TDLN (SEA TDLN) in syngeneic hosts. Wild-type (wt) TDLN induced by parental B16 tumor was used as a control. In vitro, SEA TDLN cells proliferated more vigorously, produced more IFNγ and demonstrated higher CTL activity than wt TDLN cells when activated with anti-CD3/anti-CD28/IL-2. In vivo, SEA TDLN cells mediated tumor eradication more effectively than similarly activated wt TDLN cells (p<0.01). Furthermore, use of dendritic cells (DC) plus tumor antigen in vitro in addition to anti-CD3/anti-CD28/IL-2 stimulation further amplified the immune function and therapeutic efficacy of SEA TDLN cells. DC-stimulated SEA TDLN cells eliminated nearly 90% of the pulmonary metastasis in mice bearing established B16 melanoma micrometastases. These results indicate that enforced expression of superantigen SEA in poorly immunogenic tumor cells can enhance their immunogenicity as a vaccine in vivo. The combined use of genetically modified tumor cells as vaccine to induce TDLN followed by secondary stimulation using antigen-presenting cells and tumor antigen in a sequential immunization/activation procedure may represent a unique method to generate more potent effector T cells for adoptive immunotherapy of cancer.

CD8+ T cells targeting a single immunodominant epitope are sufficient for elimination of established SV40 T antigen-induced brain tumors

Immunotherapy of established solid tumors is rarely achieved, and the mechanisms leading to success remain to be elucidated. We previously showed that extended control of advanced-stage autochthonous brain tumors is achieved following adoptive transfer of naive C57BL/6 splenocytes into sublethally irradiated line SV11 mice expressing the SV40 T Ag (T Ag) oncoprotein, and was associated with in vivo priming of CD8(+) T cells (T(CD8)) specific for the dominant epitope IV (T Ag residues 404-411). Using donor lymphocytes derived from mice that are tolerant to epitope IV or a newly characterized transgenic mouse line expressing an epitope IV-specific TCR, we show that epitope IV-specific T(CD8) are a necessary component of the donor pool and that purified naive epitope IV-specific T(CD8) are sufficient to promote complete and rapid regression of established tumors. While transfer of naive TCR-IV cells alone induced some initial tumor regression, increased survival of tumor-bearing mice required prior conditioning of the host with a sublethal dose of gamma irradiation and was associated with complete tumor eradication. Regression of established tumors was associated with rapid accumulation of TCR-IV T cells within the brain following initial priming against the endogenous T Ag in the peripheral lymphoid organs. Additionally, persistence of functional TCR-IV cells in both the brain and peripheral lymphoid organs was associated with long-term tumor-free survival. Finally, we show that production of IFN-gamma, but not perforin or TNF-alpha, by the donor lymphocytes is critical for control of autochthonous brain tumors.

Tumor-induced CD11b+Gr-1+ myeloid cells suppress T cell sensitization in tumor-draining lymph nodes

Suppression of tumor-specific T cell sensitization is a predominant mechanism of tumor escape. To identify tumor-induced suppressor cells, we transferred spleen cells from mice bearing progressive MCA205 sarcoma into sublethally irradiated mice. These mice were then inoculated subdermally with tumor cells to stimulate T cell response in the tumor-draining lymph-node (TDLN). Tumor progression induced splenomegaly with a dramatic increase (22.1%) in CD11b(+)Gr-1(+) myeloid-derived suppressor cells (MDSC) compared with 2.6% of that in normal mice. Analyses of therapeutic effects by the adoptive immunotherapy revealed that the transfer of spleen cells from tumor-bearing mice severely inhibited the generation of tumor-immune T cells in the TDLN. We further identified MDSC to be the dominant suppressor cells. However, cells of identical phenotype from normal spleens lacked the suppressive effects. The suppression was independent of CD4(+)CD25(+) regulatory T cells. Intracellular IFN-gamma staining revealed that the transfer of MDSC resulted in a decrease in numbers of tumor-specific CD4(+) and CD8(+) T cells. Transfer of MDSC from MCA207 tumor-bearing mice also suppressed the MCA205 immune response indicating a lack of immunologic specificity. Further analyses demonstrated that MDSC inhibited T cell activation that was triggered either by anti-CD3 mAb or by tumor cells. However, MDSC did not suppress the function of immune T cells in vivo at the effector phase. Our data provide the first evidence that the systemic transfer of MDSC inhibited and interfered with the sensitization of tumor-specific T cell responses in the TDLN.

Memory T cells in cancer immunotherapy: which CD8 T-cell population provides the best protection against tumours?

Cancer immunotherapy strategies often fail because of immunosuppressive mechanisms present in the tumour-bearing host. Adoptive T-cell transfer therapy circumvents this problem by activating tumour-specific CD8(+) T cells in vitro and transferring them back into the patient. Classically, effector T cells have been used in these studies because of their potent anti-tumour activity. However, it is becoming apparent that highly activated effector cells may become terminally differentiated, display impaired proliferation and survival in vivo, and mediate short-term anti-tumour effects. In contrast to effector cells, memory cells have enhanced proliferative potential and survival, and the potential to provide more robust and enduring protection against tumours. Here, we discuss key studies in the field of adoptive T-cell transfer, along with some of our own results relating to this area. Based on the body of existing research, it is clear that CD8(+) T cells with memory potential are superior to terminally differentiated effectors in mediating successful tumour clearance. Opinions remain divided as to whether the central memory or effector memory T-cell subset is capable of providing the best protection against tumours. We propose that as these cell types have different but complementary benefits for the anti-tumour immune response, the ideal cell population to use for adoptive T-cell transfer should consist of a heterogeneous mixture of memory cells.

Potent in vivo anti-tumor activity of isolated CD62L(low) lymph node cells sensitized in vivo with tumor lysate-pulsed DC-based vaccines

BACKGROUND

DC are potent APC that can activate both CD4 and CD8 T cells in vitro and in vivo. Although the efficacy of DC-based cancer vaccines is currently being evaluated in clinical trials, the systemic immune suppression in cancer patients negatively impacts the clinical benefit of this therapeutic approach. Therefore, in this study we tested the feasibility and anti-tumor effect of adoptive immunotherapy using in vitro-activated CD62L(low) lymph node cells that were isolated from DC-vaccinated draining lymph nodes (VDLN).

METHODS

DC were prepared from BM cells and loaded with tumor lysate for inoculating into naive mice. Subsequently, the VDLN were removed and CD62L(low) cells in the VDLN population isolated, expanded in vitro by 5-day culture with IL-2 and immobilized anti-CD3 stimulation, then injected into mice with established pulmonary tumors. Eighteen days after treatment, mice were killed in order to enumerate pulmonary tumor nodes.

RESULTS

DC phagocytosed the tumor lysate efficiently and induced detectable T-cell responses and significant cell expansion in the draining lymph nodes. After induction of maturation by LPS treatment, DC expressed higher levels of CD40, CD86 and MHC class II molecules. When CD62L(low) VDLN cells that had been isolated and expanded in vitro were transferred into tumor-bearing mice, as few as 3 x 10(6) cells were able to cure metastatic pulmonary tumors in vivo.

DISCUSSION

DC-based VDLN T cells are an important source of anti-tumor effector for adoptive immunotherapy. This study provides a novel and an effective protocol using T-cell adoptive immunotherapy for application in cancer patients; therefore, clinical trials based on this protocol may be warranted.

Anti-tumor activity and trafficking of self, tumor-specific T cells against tumors located in the brain

It is commonly believed that T cells have difficulty reaching tumors located in the brain due to the presumed "immune privilege" of the central nervous system (CNS). Therefore, we studied the biodistribution and anti-tumor activity of adoptively transferred T cells specific for an endogenous tumor-associated antigen (TAA), gp100, expressed by tumors implanted in the brain. Mice with pre-established intracranial (i.c.) tumors underwent total body irradiation (TBI) to induce transient lymphopenia, followed by the adoptive transfer of gp100(25-33)-specific CD8+ T cells (Pmel-1). Pmel-1 cells were transduced to express the bioluminescent imaging (BLI) gene luciferase. Following adoptive transfer, recipient mice were vaccinated with hgp100(25-33) peptide-pulsed dendritic cells (hgp100(25-33)/DC) and systemic interleukin 2 (IL-2). This treatment regimen resulted in significant reduction in tumor size and extended survival. Imaging of T cell trafficking demonstrated early accumulation of transduced T cells in lymph nodes draining the hgp100(25-33)/DC vaccination sites, the spleen and the cervical lymph nodes draining the CNS tumor. Subsequently, transduced T cells accumulated in the bone marrow and brain tumor. BLI could also detect significant differences in the expansion of gp100-specific CD8+ T cells in the treatment group compared with mice that did not receive either DC vaccination or IL-2. These differences in BLI correlated with the differences seen both in survival and tumor infiltrating lymphocytes (TIL). These studies demonstrate that peripheral tolerance to endogenous TAA can be overcome to treat tumors in the brain and suggest a novel trafficking paradigm for the homing of tumor-specific T cells that target CNS tumors.

Tracking the elusive lymphocyte: methods of detection during adoptive immunotherapy

Adoptive immunotherapy is an attractive cancer treatment modality due to its capacity to target primary and metastatic lesions with large numbers of tumor-reactive, cytotoxic lymphocytes. The inability of fully armed lymphocytes to traffic into sites of tumor has been proposed as a causal factor for the minimal success observed clinically with this type of immunotherapy. The study of lymphocyte trafficking during adoptive immunotherapy has been limited, despite the existence of a variety of tracking methods. In murine models that simulate adoptive immunotherapy, the use of congenic mice and cell tracking dyes can be used to elucidate lymphocyte trafficking behavior. The continued development of novel technologies will further contribute to this expanding area of research.

Downregulation of CD4+CD25+ regulatory T cells may underlie enhanced Th1 immunity caused by immunization with activated autologous T cells

Regulatory T cells (Treg) play important roles in immune system homeostasis, and may also be involved in tumor immunotolerance by suppressing Th1 immune response which is involved in anti-tumor immunity. We have previously reported that immunization with attenuated activated autologous T cells leads to enhanced anti-tumor immunity and upregulated Th1 responses in vivo. However, the underlying molecular mechanisms are not well understood. Here we show that Treg function was significantly downregulated in mice that received immunization of attenuated activated autologous T cells. We found that Foxp3 expression decreased in CD4+CD25+ T cells from the immunized mice. Moreover, CD4+CD25+Foxp3+ Treg obtained from immunized mice exhibited diminished immunosuppression ability compared to those from naïve mice. Further analysis showed that the serum of immunized mice contains a high level of anti-CD25 antibody (about 30 ng/ml, p<0.01 vs controls). Consistent with a role of anti-CD25 response in the downregulation of Treg, adoptive transfer of serum from immunized mice to naïve mice led to a significant decrease in Treg population and function in recipient mice. The triggering of anti-CD25 response in immunized mice can be explained by the fact that CD25 was induced to a high level in the ConA activated autologous T cells used for immunization. Our results demonstrate for the first time that immunization with attenuated activated autologous T cells evokes anti-CD25 antibody production, which leads to impeded CD4+CD25+Foxp3+ Treg expansion and function in vivo. We suggest that dampened Treg function likely contributes to enhanced Th1 response in immunized mice and is at least part of the mechanism underlying the boosted anti-tumor immunity.

Clinical model: interferons activate human monocytes to an eradicative tumor cell level in vitro

Eradicative levels of antitumor activity by cytokines and leukocytes have not yet been reached experimentally and are needed clinically. Only a limited number of human cancers respond to therapy with interferon (IFN), other cytokines, or mononuclear leukocytes despite significant antitumor activity in vitro. We studied the IFN and monocytic cell conditions that would lead to an eradicative effect using human cells in vitro. Targets of the IFN-activated monocytic cells were either four human tumor cell lines (human osteosarcoma [HOS], LOX melanoma, A549 lung tumor, and SNB-19 glioblastoma) or two diploid cell lines (WI38 and MRC5). An average of 30-90 colony-forming tumor target cells were cultured overnight in 96-well tissue culture plates prior to treatment with serially diluted IFN with or without activated elutriation-purified monocytes or lymphocytes. The target cell colonies were treated for 3 days. The colonies were then stained with crystal violet to determine the levels of antitumor activity. IFN-activated human monocytes reached an eradicative level (95%-100%) against three of four tumor cell lines. The eradicative level (1) was induced best in human monocytes activated by combined type I and II IFNs, (2) was effective against tumor cells that were growing for 24 h, (3) was specific for human tumors, as diploid human cells were not inhibited, and (4) required contact between the macrophage and the tumor cells. Also, for the first time, the minimal effective concentration (MEC) of IFNs to activate monocytes can approach those needed for antiviral activity. To our knowledge, this is the first report of near total eradication of many tumor cells, but not diploid cells, by IFN-activated monocytes. Because of its potency and specificity, the IFN-activated monocyte arm of the innate immune system may be a candidate for therapy of established tumors.

Adoptive transfer of tumor-primed, in vitro-activated, CD4+ T effector cells (TEs) combined with CD8+ TEs provides intratumoral TE proliferation and synergistic antitumor response

The importance of CD4+ Th1 cells during the effector phase of the antitumor response has been overshadowed by emphasis on CD8+ cytotoxic T lymphocytes (CTLs). To determine their respective functions, we purified antigen-primed T cells from tumor-draining lymph nodes and separately activated CD4+ and CD8+ subsets in vitro. Adoptive transfer of CD4+ T effector cells (T(E)s) combined with CD8+ T(E)s provided synergistic therapy for mice bearing subcutaneous, intracranial, or advanced pulmonary metastases. CD4+ T(E)s augmented IFN-gamma production by CD8+ T(E)s when cells were stimulated by tumor digest-containing antigen-presenting cells (APCs). CD4+ T(E)s infiltrated and proliferated extensively in pulmonary tumors, while also stimulating tumor antigen-specific CD8+ T cells. By contrast, CD8+ T(E)s showed minimal intratumoral proliferation in the absence of CD4+ cells or when systemically transferred CD4+ cells were prevented from infiltrating pulmonary tumors by pretreatment with pertussis toxin. Irradiation of CD4+ T cells immediately prior to adoptive transfer abrogated their intratumoral proliferation and direct antitumor efficacy but did not block their capacity to stimulate intratumoral CD8+ T(E) proliferation or tumor regression. These results highlight the importance of cross-presentation of tumor antigens during the effector phase of immunotherapy and suggest that approaches to stimulate CD4+ T(E) function and boost APC cross-presentation within tumors will augment cancer immunotherapy.

Host lymphodepletion augments T cell adoptive immunotherapy through enhanced intratumoral proliferation of effector cells

T-cell adoptive immunotherapy for stringent murine tumor models, such as intracranial, s.c., or advanced pulmonary metastases, routinely uses lymphodepletive conditioning regimens before T-cell transfer, like recent clinical protocols. In this study, we examined whether host lymphodepletion is an obligatory component of curative T-cell therapy; we also examined the mechanism by which it augments therapy. Mice bearing intracranial, s.c., or 10-day pulmonary metastases of MCA 205 received total body irradiation conditioning or were nonirradiated before i.v. transfer of tumor-reactive T cells. Total body irradiation was not required for immunologically specific curative therapy and induction of memory provided that a 3- to 12-fold higher T-cell dose was administered. The mechanism involved enhanced intratumoral proliferation of T-effector cells in total body irradiation-conditioned recipients. In this tumor model, intratumoral T(reg) cells were not detected; consequently, intratumoral T-effector cells produced identical amounts of IFN-gamma upon ex vivo antigen stimulation irrespective of total body irradiation conditioning. Thus, host lymphodepletion augments T-cell immunotherapy through enhanced antigen-driven proliferation of T-effector cells, but curative therapy can be achieved in nonconditioned hosts by escalation of T-cell dose. These data provide a rationale for dose escalation of T-effector cells in situations where single or repeated lymphodepletion regimens are contraindicated.

Vaccines with enhanced costimulation maintain high avidity memory CTL

The avidity of Ag-specific CTL is a critical determinant for clearing viral infection and eliminating tumor. Although previous studies have demonstrated that vaccines using enhanced costimulation will enhance the level and avidity of Ag-specific T cells from naive mice, there are conflicting data about the effects of vaccines using enhanced costimulation (vector or dendritic cell based) on the survival of memory T cells. In this study we have first extended previous observations that primary vaccination with a recombinant vaccinia virus (rV-) expressing a model Ag (LacZ) and a triad of T cell costimulatory molecules (B7-1, ICAM-1, and LFA-3 (designated TRICOM)) enhances the level and avidity of T cells from naive vaccinated C57BL/6 (Thy1.2) mice. Adoptive transfer of Thy1.1 memory CD8(+) T cells into naive Thy1.2 C57BL/6 mice was followed by booster vaccinations with a recombinant fowlpox (rF-)-expressing LacZ (rF-LacZ) or booster vaccinations with rF-LacZ/TRICOM. Analysis of levels of beta-galactosidase tetramer-positive T cells and functional assays (IFN-gamma expression and lytic activity) determined that booster vaccinations with rF-LacZ/TRICOM were superior to booster vaccinations with rF-LacZ in terms of both maintenance and enhanced avidity of memory CD8(+) T cells. Antitumor experiments using a self-Ag (carcinoembryonic Ag (CEA) vaccines in CEA transgenic mice bearing CEA-expressing tumors) also demonstrated that the use of booster vaccinations with vaccines bearing enhanced costimulatory capacity had superior antitumor effects. These studies thus have implications in the design of more effective vaccine strategies.

Enhancement of T cell localization in mammary tumors through transient inhibition of T cell myosin function

Adoptive immunotherapy is hampered by poor lymphocyte localization in tumors. The polarized, adhesive phenotype of activated lymphocytes may contribute to this problem by making the cells prone to trapping and damage in pulmonary microvasculature. We found that transient inhibition of T cell polarization prior to i.v. infusion reduces trapping and improves tumor localization. Activated T cells were rendered nonpolar and nonadhesive by treatment with myosin light-chain kinase inhibitor ML-7. Polarity, adhesiveness, and motility recovered by 6 h after treatment, cytotoxicity, and proliferation by 24 h. ErbB2-specific T cells were infused i.v. into mice bearing ErbB2-expressing mammary tumors. ML-7 pre-treatment reduced T cell arrest in lungs by a factor of eight, improved tumor localization by 4-fold, and increased lymph node homing. Although this improvement alone proved insufficient to alter outcome in an immunotherapy experiment, this study indicates that cytoskeletal modification is a promising strategy for altering the trafficking of infused lymphocytes.

Adoptive immunotherapy of cancer with polyclonal, 108-fold hyperexpanded, CD4+ and CD8+ T cells

T cell-mediated cancer immunotherapy is dose dependent and optimally requires participation of antigen-specific CD4+ and CD8+ T cells. Here, we isolated tumor-sensitized T cells and activated them in vitro using conditions that led to greater than 108-fold numerical hyperexpansion of either the CD4+ or CD8+ subset while retaining their capacity for in vivo therapeutic efficacy. Murine tumor-draining lymph node (TDLN) cells were segregated to purify the CD62Llow subset, or the CD4+ subset thereof. Cells were then propagated through multiple cycles of anti-CD3 activation with IL-2 + IL-7 for the CD8+ subset, or IL-7 + IL-23 for the CD4+ subset. A broad repertoire of TCR Vbeta families was maintained throughout hyperexpansion, which was similar to the starting population. Adoptive transfer of hyper-expanded CD8+ T cells eliminated established pulmonary metastases, in an immunologically specific fashion without the requirement for adjunct IL-2. Hyper-expanded CD4+ T cells cured established tumors in intracranial or subcutaneous sites that were not susceptible to CD8+ T cells alone. Because accessibility and antigen presentation within metastases varies according to anatomic site, maintenance of a broad repertoire of both CD4+ and CD8+ T effector cells will augment the overall systemic efficacy of adoptive immunotherapy.

A novel system for simultaneous in vivo tracking and biological assessment of leukemia cells and ex vivo generated leukemia-reactive cytotoxic T cells

To determine the mechanisms by which adoptive immunotherapy could reduce lethality to acute myelogenous leukemia (AML), a novel technique was developed to track both leukemic blasts and adoptively transferred cytotoxic T cells (CTLs) independently and simultaneously in mice. To follow the fate of ex vivo generated anti-AML-reactive CTLs, splenocytes obtained from enhanced green fluorescent protein transgenic mice were cocultured with AML lysate-pulsed dendritic cells, which subsequently were expanded by exposure to anti-CD3/CD28 monoclonal antibody-coated magnetic microspheres. To track AML cells, stable transfectants of C1498 expressing DsRed2, a red fluorescent protein, were generated. Three factors related to CTLs correlated with disease-free survival: (a). CTL L-selectin expression. L-Selectin high fractions resulted in 70% disease-free survival, whereas L-selectin low-expressing CTLs resulted in only 30% disease-free survival. (b). Duration of ex vivo expansion (9 versus 16 days). Short-term expanded CTLs could be found at high frequency in lymphoid organs for longer than 4 weeks after transfer, whereas long-term expanded CTLs were cleared from the system after 2 weeks. Duration of expansion correlated inversely with L-selectin expression. (c). CTL dose. A higher dose (40 versus 5 x 10(6)) resulted in superior disease-free survival. This survival advantage was achieved with short-term expanded CTLs only. The site of treatment failure was mainly the central nervous system where no CTLs could be identified at AML sites.

Memory T cells originate from adoptively transferred effectors and reconstituting host cells after sequential lymphodepletion and adoptive immunotherapy

Adoptive transfer of tumor-specific effector T cells induces regression of advanced tumors and induces a long term memory response; however, the origin of this response has not been clearly defined. In this study Thy1.2+ mice bearing advanced MCA-205 tumors were treated with sublethal total body irradiation, followed by adoptive transfer of congenic Thy1.1+ T cells that had been sensitized to tumor in vivo and then activated ex vivo with anti-CD3, IL-2, and IL-7. Splenocytes were recovered >140 days after the initial therapy, and the L-selectinlow memory cell subset was separated into host Thy1.2+ and transferred Thy1.1+ cells and restimulated ex vivo. Both adoptively transferred Thy1.1+ cells as well as reconstituted host Thy1.2+ cells could specifically eliminate MCA-205 pulmonary metastases. Interestingly, hosts with partial responses followed by tumor recurrence nevertheless harbored memory cells that could be isolated and numerically amplified ex vivo to regenerate potent effector function. Memory cells were recovered after adoptive transfer into lymphodepleted nontumor-bearing hosts, indicating that they were not dependent on continued Ag exposure. These experiments establish that rapid ex vivo expansion of tumor Ag-primed T cells does not abrogate their capacity to become long-lived memory cells. Moreover, immune-mediated tumor regression coincident with lymphoid reconstitution produces another wave of host memory cells. These data suggest an approach to rescuing antitumor immune function even in hosts with long-standing progressive tumor through restorative ex vivo activation.

Donor cell cycling, trafficking, and accumulation during adoptive immunotherapy for murine lung metastases

Adoptive cellular immunotherapy treats metastatic cancer by infusing cultured T cells derived from resected tumors or primed lymph nodes. The infused cells must accumulate in metastatic lesions to suppress growth; however, this process and the resulting clinical response are dynamic and evolve during the days and weeks following cell infusion. This study used novel experimental techniques to determine the fate of infused, cultured tumor-draining lymph node (TDLN) cells during the treatment of murine pulmonary micrometastases. After infusion, the cultured TDLN cells accumulated in the pulmonary vasculature, systemic lymph nodes, and spleen. Donor cells were initially confined to alveolar capillaries with no movement into metastases. Within 4 h, TDLN cells began migrating across pulmonary postcapillary venules and first appeared within metastases. After 24 h, most donor cells in the lung were associated with tumor nodules. Donor cell proliferation within the lung and lymphoid organs was detected within 24 h of infusion and continued throughout the 5-day period of observation. Furthermore, those proliferating in lymphoid organs trafficked back to the tumor-bearing lungs, accounting for approximately 50% of the donor cells recovered from these sites after 5 days. Finally, donor T cells entering metastases both early (within 1-2 days) and late (after 2 days) suppressed tumor growth, but the early recruits accounted for most of the therapeutic response. Thus, cultured TDLN cells migrate directly into tumor-bearing organs and seed the recirculating pool of lymphocytes after infusion. Small fractions of the later differentiate in lymphoid organs and migrate into the lungs but appear less effective than effector cells in the initial bolus.

New tools for quantifying and visualizing adoptively transferred cells in recipient mice

Adoptive transfer of donor cells in mice is widely used in research on the function and metabolism of lymphocytes. We have evaluated new approaches for quantifying and visualizing adopted cells in recipient mouse tissue. We injected spleen cells from male beta-galactosidase (LacZ) transgenic mice into female wild type mice and assessed the robustness of real-time PCR for quantifying the accumulation of the donor cells in blood and tissues of the recipient mice. The clearance of donor cells from the blood and their recruitment in lung, spleen, liver, and kidney was almost identical when obtained with amplification of the donor cell-specific LacZ or sex-determining region on the Y-chromosome (SRY) gene. We found, however, a marked difference in the PCR amplification efficiency of genomic DNA of different tissues, which should be taken into account when comparing recruitment of donor cells in different tissues. To visualize adoptively transferred cells, we used either spleen cells from transgenic mice, which express a Green Fluorescent Protein (GFP) transgene or spleen cells that had been fluorescence labeled ex vivo with CellTracker Orange. Whereas ex vivo and in vivo labeled donor cells could easily be detected in recipient mouse tissue by laser scanning confocal microscopy, only CellTracker Orange-labeled cells could be detected by conventional fluorescence microscopy due to autofluorescence in the examined tissues. Importantly, CellTracker Orange labeling did not appear to affect the blood clearance or the tissue accumulation of the donor cells. Together, the results demonstrate the usefulness of new protocols for quantifying and visualizing adoptively transferred cells by genetic tracing or fluorescence labeling.