Rapid accumulation of adoptively transferred CD8+ T cells at the tumor site is associated with long-term control of SV40 T antigen-induced tumors

Protection from tumor recurrence following adoptive immunotherapy varies with host conditioning regimen despite initial regression of autochthonous murine brain tumors

Adoptive T cell transfer (ACT) has achieved clinical success in treating established cancer, particularly in combination with lymphodepleting regimens. Our group previously demonstrated that ACT following whole-body irradiation (WBI) promotes high-level T cell accumulation, regression of established brain tumors, and long-term protection from tumor recurrence in a mouse model of SV40 T antigen-induced choroid plexus tumors. Here we asked whether an approach that can promote strong donor T-cell responses in the absence of WBI might also produce this dramatic and durable tumor elimination following ACT. Agonist anti-CD40 antibody can enhance antigen-specific CD8(+) T-cell responses and has shown clinical efficacy as a monotherapy in the setting of cancer. We show that anti-CD40 conditioning promotes rapid accumulation of tumor-specific donor CD8(+) T cells in the brain and regression of autochthonous T antigen-induced choroid plexus tumors, similar to WBI. Despite a significant increase in the lifespan, tumors eventually recurred in anti-CD40-conditioned mice coincident with loss of T-cell persistence from both the brain and lymphoid organs. Depletion of CD8(+) T cells from the peripheral lymphoid organs of WBI-conditioned recipients failed to promote tumor recurrence, but donor cells persisted in the brains long-term in CD8-depleted mice. These results demonstrate that anti-CD40 conditioning effectively enhances ACT-mediated acute elimination of autochthonous tumors, but suggest that mechanisms associated with WBI conditioning, such as the induction of long-lived T cells, may be critical for protection from tumor recurrence.

Short-term corticosterone treatment decreases the early CD8+ T cell response to simian virus 40 tumor antigen but has no impact on the late CD8+ T cell response

CD8+ T cells (T(CD8)) help control tumor growth in vivo through recognition of distinct tumor antigens and cytolysis of tumor cells. The T(CD8) immune response in C57BL/6 mice to the Simian Virus 40 oncoprotein, large tumor antigen (Tag), targets multiple epitopes and is well-characterized. Epitope IV, an H-2K(b)-restricted epitope, is immunodominant while epitope I, an H-2D(b)-restricted epitope is subdominant. GCs alter many aspects of T cell function. Indeed, the current studies demonstrate that exposure of mice to the immunosuppressive GC, corticosterone (CORT), over the entire course of the primary immune response limits activation of endogenous Tag-specific T(CD8). Even short-term CORT treatment from day -1 to day +2 post-immunization significantly reduced splenic size and the absolute number of Tag-specific T(CD8) on day 6 post-immunization. In vivo killing activity was also reduced. However, by day 10 post-immunization, the peak of the immune response, the absolute number of Tag-specific T(CD8) and their in vivo killing of epitope I or epitope IV-expressing target cells had recovered in CORT treated mice. Adoptive transfer of transgenic T cells post-CORT removal demonstrated that CORT decreased the ability of the endogenous antigen-presenting cells to induce proliferation of the exogenous transgenic T cells. Combined, these studies have implications about the timing of clinical steroid treatment relative to immunization or adoptive transfer for cancer immunotherapy.

Review on the relationship between human polyomaviruses-associated tumors and host immune system

The polyomaviruses are small DNA viruses that can establish latency in the human host. The name polyomavirus is derived from the Greek roots poly-, which means "many," and -oma, which means "tumours." These viruses were originally isolated in mouse (mPyV) and in monkey (SV40). In 1971, the first human polyomaviruses BK and JC were isolated and subsequently demonstrated to be ubiquitous in the human population. To date, at least nine members of the Polyomaviridae family have been identified, some of them playing an etiological role in malignancies in immunosuppressed patients. Here, we describe the biology of human polyomaviruses, their nonmalignant and malignant potentials ability, and their relationship with the host immune response.

Direct presentation regulates the magnitude of the CD8+ T cell response to cell-associated antigen through prolonged T cell proliferation

The magnitude and complexity of Ag-specific CD8(+) T cell responses is determined by intrinsic properties of the immune system and extrinsic factors, such as vaccination. We evaluated mechanisms that regulate the CD8(+) T cell response to two distinct determinants derived from the same protein Ag, SV40 T Ag (T Ag), following immunization of C57BL/6 mice with T Ag-transformed cells. The results show that direct presentation of T cell determinants by T Ag-transformed cells regulates the magnitude of the CD8(+) T cell response in vivo but not the immunodominance hierarchy. The immunodominance hierarchy was reversed in a dose-dependent manner by addition of excess naive T cells targeting the subdominant determinant. However, T cell competition played only a minor role in limiting T cell accumulation under physiological conditions. We found that the magnitude of the T cell response was regulated by the ability of T Ag-transformed cells to directly present the T Ag determinants. The hierarchy of the CD8(+) T cell response was maintained when Ag presentation in vivo was restricted to cross-presentation, but the presence of T Ag-transformed cells capable of direct presentation dramatically enhanced T cell accumulation at the peak of the response. This enhancement was due to a prolonged period of T cell proliferation, resulting in a delay in T cell contraction. Our findings reveal that direct presentation by nonprofessional APCs can dramatically enhance accumulation of CD8(+) T cells during the primary response, revealing a potential strategy to enhance vaccination approaches.

Recurrence of Intracranial Tumors following Adoptive T Cell Therapy Can Be Prevented by Direct and Indirect Killing Aided by High Levels of Tumor Antigen Cross-Presented on Stromal Cells

Elimination of peripheral tumors by adoptively transferred tumor-specific T cells may require killing of cancer cells and tumor stromal cells. Tumor Ags are cross-presented on stromal cells, resulting in direct cytotoxic T cell (CTL) killing of both Ag-expressing cancer cells and stromal cells. Indirect killing of Ag loss variant cells also occurs. We show here that similar processes occur in a brain tumor stromal environment. We used murine cancer cell lines that express high or low levels of a peptide Ag, SIYRYYGL (SIY), recognized by transgenic 2C CD8(+) T cells. The two cell lines are killed with equivalent efficiency by 2C T cells in vitro. Following adoptive transfer of 2C T cells into mice with established SIY-Hi or SIY-Lo brain tumors, tumors of both types regressed, but low-Ag-expressing tumors recurred. High-Ag-expressing tumors contained CD11b(+) cells cross-presenting SIY peptide and were completely eliminated by 2C T cells. To further test the role of cross-presentation, RAG1(-/-) H-2(b) mice were infused with H-2(k) tumor cells expressing high levels of SIY peptide. Adoptively transferred 2C T cells are able to kill cross-presenting H-2(b) stromal cells but not H-2(k) tumor cells. In peripheral models, this paradigm led to a small static tumor. In the brain, activated 2C T cells were able to kill cross-presenting CD11b(+) cells and completely eliminate the H-2(k) tumors in most mice. Targeting brain tumor stroma or increasing Ag shedding from tumor cells to enhance cross-presentation may improve the clinical success of T cell adoptive therapies.

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.