Augmentation versus inhibition: effects of conjunctional OX-40 receptor monoclonal antibody and IL-2 treatment on adoptive immunotherapy of advanced tumor

Immunotherapy of malignant melanoma

Several areas of immunotherapeutic research may ultimately improve the effectiveness of active specific immunotherapy for melanoma and other malignancies. Identification of the most relevant tumor antigens will continue to be a vital component of vaccine design. Optimizing delivery of these antigens by use of adjuvants, dendritic cells, or heat shock proteins will enhance the immunogenicity of vaccines. The use of DNA vaccines to deliver nucleotides that encode relevant antigens and immunologic molecules, such as costimulatory molecules, and the use of targeted therapy with immunocytokines have yielded promising results in animal studies. Finally, cutting-edge techniques such as quantitative polymerase chain reaction and gene/protein microarrays will be used to monitor the response to a vaccine and thereby guide management decisions. Although IFN-alpha 2b is the only FDA-approved adjuvant treatment for AJCC stage IIB/III melanoma, recent data failed to show a benefit in overall survival. For patients with AJCC stage IV melanoma, chemotherapy with dacarbazine is currently the standard of care, with modest response rates of 15% to 20%. The encouraging response rates and low toxicities that were reported in phase I/III trials suggest that active immunotherapy may prove to be the most effective adjuvant therapy. At present, there are no FDA-approved cancer vaccines for malignant melanoma, and the results of ongoing randomized phase III clinical trials are greatly anticipated.

Tumor-induced L-selectinhigh suppressor T cells mediate potent effector T cell blockade and cause failure of otherwise curative adoptive immunotherapy

Tumor-specific effector T cells (T(E)) are naturally sensitized within the L-selectin(low) (CD62L(low)) fraction of tumor-draining lymph nodes (TDLN). Whether isolated from day 9 (D9) or day 12 (D12) TDLN, 5 million L-selectin(low) T(E) could be culture activated and adoptively transferred to achieve complete rejection of established intradermal, pulmonary, and brain tumors. Surprisingly, although 25 million unfractionated T cells from D9 TDLN were equally effective, even 100 million unfractionated T cells from D12 TDLN seldom prevented lethal intradermal tumor progression, despite a pronounced therapeutic excess of T(E). This highly reproducible treatment failure was due to cotransfer of tumor-induced, L-selectin(high) suppressor T cells (T(S)) which were also present in D12 TDLN. In contrast, D9 TDLN and normal spleens lacked L-selectin(high) T(S). Only those L-selectin(high) D12 TDLN T cells that down-regulated L-selectin during culture activation were suppressive in vivo and in vitro, and, like L-selectin(low) T(E), trafficked promptly into tumors following i.v. administration. This is the first demonstration that adoptive immunotherapy can fail as a direct result of passenger T(S) that share certain phenotypic and trafficking features of T(E), even when otherwise curative doses of T(E) have been administered. Furthermore, in contrast to recently described CD4(+)CD25(+) T(S) and plasmacytoid dendritic cell-activated T(S), tumor-induced L-selectin(high) T(S) prevent tumor rejection via blockade of sensitized, activated T(E) rather than via afferent blockade.

Systemic administration of IL-15 augments the antigen-specific primary CD8+ T cell response following vaccination with peptide-pulsed dendritic cells

The systemic administration of IL-2 can act as a potent adjuvant for T cell-directed vaccine strategies. However, not only is the administration of IL-2 potentially toxic, but recent evidence suggests that it may also paradoxically limit the duration and magnitude of the cytotoxic T cell response. A recently identified cytokine, IL-15, shares many properties with IL-2 and may provide a preferential means of augmenting T cell-directed vaccine responses. Although well characterized in vitro, there are few data on the ability of IL-15 to augment T cell-mediated responses in vivo. We therefore evaluated the ability of systemic IL-15 to function as a T cell adjuvant in a murine vaccine model. To establish a population of easily identifiable Ag-responsive T cells, naive CD8(+) (OT-1) T cells were first adoptively transferred into mice. Vaccination with peptide-pulsed dendritic cells induced a modest expansion of OT-1 T cells. The addition of systemic IL-15 for 7 days following vaccination resulted in a significant increase in the expansion of responding T cells in the PBL, spleen, and lymph nodes. Importantly, the responding T cells were cytotoxic and maintained a Tc1-biased phenotype. We did not observe either enhanced resistance to activation-induced cell death or preferential generation of memory T cells as a result of treatment with IL-15 compared with IL-2. These studies show for the first time that IL-15 is capable of augmenting the primary CD8(+) T cell response to vaccination and contribute to the basis for future experiments exploring the clinical role of IL-15.

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

Tumor-draining lymph nodes (TDLN) contain sensitized T cells with the phenotype CD62 L-selectin(low) (CD62L(low)) that can be activated ex vivo with anti-CD3 mAb and IL-2 to acquire potent dose-dependent effector function manifested upon adoptive transfer to secondary tumor-bearing hosts. In this study advanced tumor models were used as a stringent comparison of efficacy for the CD62L(low) subset, comprising 5-7% of the TDLN cells, vs the total population of TDLN cells following culture in high dose IL-2 (100 U/ml). During the 9-day activation period the total number of CD8+ T cells increased 1500-fold, with equivalent proliferation in the CD62L(low) vs the total TDLN cell cultures. Adoptive transfer of activated CD62L(low) cells eliminated 14-day pulmonary metastases and cured 10-day s.c. tumors, whereas transfer of maximally tolerated numbers of total TDLN cells was not therapeutic. Despite their propagation in a high concentration of IL-2, the hyperexpanded CD62L(low) subset of TDLN cells functioned in vivo without exogenous IL-2, and CD8+ T cells demonstrated relative helper independence. Moreover, the anti-tumor response was specific for the sensitizing tumor, and long term memory was established. The facile enrichment of tumor-reactive TDLN T cells, based on the CD62L(low) phenotype, circumvents the need for prior knowledge of the relevant tumor Ags. Coupling the isolation of pre-effector T cells with rapid ex vivo expansion to >3 logs could overcome some of the shortcomings of active immunotherapy or in vivo cytokine treatment, where selective robust expansion of effector cells has been difficult to achieve.

Immunogenicity and therapeutic efficacy of dendritic-tumor hybrid cells generated by electrofusion

Dendritic cells (DCs) are potent antigen-presenting cells capable of inducing strong immune responses to weak tumor-associated antigens. Among various DC-based approaches, cancer immunotherapy with DC-tumor fusion hybrids offers advantages of polyclonal stimulation of a diverse array of tumor antigens. However, prevalent fusion methods using chemical fusogens such as polyethylene glycol often result in toxicity and low fusion efficiency. In this article, we describe an electrofusion technique, applicable to processing large numbers of cells with consistent and high fusion efficiency. Generation of fusion hybrids was verified by unequivocal experimental evidence. In animal models, fusion hybrids expressed the mature DC-like phenotype. They stimulated both CD4 and CD8 tumor-specific T cells to secrete interferon-gamma in vitro. In immunotherapy, a single vaccination with DC-tumor fusion cells along with interleukin-12 as an adjuvant eradicated tumors established in the skin nd lung. These results provide an impetus for treating cancer patients with similarly generated cells.

OX40: targeted immunotherapy--implications for tempering autoimmunity and enhancing vaccines

OX40 (CD134), a membrane-bound member of the tumor-necrosis-factor-receptor superfamily, is expressed primarily on activated CD4+ T cells. Recently, several groups have reduced clinical signs of autoimmunity in animal models by blocking the OX40-OX40-ligand interaction or depleting OX40+ T cells. By contrast, engagement of OX40 in the setting of active immunization has potent adjuvant properties, leading to enhanced cytokine production and increased numbers of antigen-specific memory T cells. These potent adjuvant effects lead to an enhancement of anti-tumor responses. OX40 has several unique features that make it a clinically relevant target. They include: (1) T cells isolated from a site of inflammation that express OX40 are T cells that have been stimulated recentlythrough the T-cell receptor in vivo; (2) OX40 is only expressed on T cells found at the site of inflammation, therefore, targeting this receptor does not interfere with the peripheral T-cell repertoire; and (3) the biological function of OX40 is limited primarily to effector CD4+ T cells, which are a major source of cytokines to induce and maintain ongoing immune responses.