T Cells as Vehicles for Cancer Vaccination

The success of cancer vaccines is dependent on the delivery of tumor-associated antigens (TAAs) within lymphoid tissue in the context of costimulatory molecules and immune stimulatory cytokines. Dendritic cells (DCs) are commonly utilized to elicit antitumor immune responses due to their attractive costimulatory molecule and cytokine expression profile. However, the efficacy of DC-based vaccines is limited by the poor viability and lymph-node migration of exogenously generated DCs in vivo. Alternatively, adoptively transferred T cells persist for long periods of time in vivo and readily migrate between the lymphoid and vascular compartments. In addition, T cells may be genetically modified to express both TAA and DC-activating molecules, suggesting that T cells may be ideal candidates to serve as cellular vehicles for antigen delivery to lymph node-resident DCs in vivo. This paper discusses the concept of using T cells to induce tumor-specific immunity for vaccination against cancer

T cells enhance gold nanoparticle delivery to tumors in vivo

Gold nanoparticle-mediated photothermal therapy (PTT) has shown great potential for the treatment of cancer in mouse studies and is now being evaluated in clinical trials. For this therapy, gold nanoparticles (AuNPs) are injected intravenously and are allowed to accumulate within the tumor via the enhanced permeability and retention (EPR) effect. The tumor is then irradiated with a near infrared laser, whose energy is absorbed by the AuNPs and translated into heat. While reliance on the EPR effect for tumor targeting has proven adequate for vascularized tumors in small animal models, the efficiency and specificity of tumor delivery in vivo, particularly in tumors with poor blood supply, has proven challenging. In this study, we examine whether human T cells can be used as cellular delivery vehicles for AuNP transport into tumors. We first demonstrate that T cells can be efficiently loaded with 45 nm gold colloid nanoparticles without affecting viability or function (e.g. migration and cytokine production). Using a human tumor xenograft mouse model, we next demonstrate that AuNP-loaded T cells retain their capacity to migrate to tumor sites in vivo. In addition, the efficiency of AuNP delivery to tumors in vivo is increased by more than four-fold compared to injection of free PEGylated AuNPs and the use of the T cell delivery system also dramatically alters the overall nanoparticle biodistribution. Thus, the use of T cell chaperones for AuNP delivery could enhance the efficacy of nanoparticle-based therapies and imaging applications by increasing AuNP tumor accumulation

Elimination of Metastatic Melanoma Using Gold Nanoshell-Enabled Photothermal Therapy and Adoptive T Cell Transfer

Ablative treatments such as photothermal therapy (PTT) are attractive anticancer strategies because they debulk accessible tumor sites while simultaneously priming antitumor immune responses. However, the immune response following thermal ablation is often insufficient to treat metastatic disease. Here we demonstrate that PTT induces the expression of proinflammatory cytokines and chemokines and promotes the maturation of dendritic cells within tumor-draining lymph nodes, thereby priming antitumor T cell responses. Unexpectedly, however, these immunomodulatory effects were not beneficial to overall antitumor immunity. We found that PTT promoted the infiltration of secondary tumor sites by CD11b+Ly-6G/C+ myeloid-derived suppressor cells, consequently failing to slow the growth of poorly immunogenic B16-F10 tumors and enhancing the growth of distant lung metastases. To exploit the beneficial effects of PTT activity against local tumors and on antitumor immunity whilst avoiding the adverse consequences, we adoptively transferred gp100-specific pmel T cells following PTT. The combination of local control by PTT and systemic antitumor immune reactivity provided by adoptively transferred T cells prevented primary tumor recurrence post-ablation, inhibited tumor growth at distant sites, and abrogated the outgrowth of lung metastases. Hence, the combination of PTT and systemic immunotherapy prevented the adverse effects of PTT on metastatic tumor growth and optimized overall tumor control

Gold Nanoparticle Delivery of Modified CpG Stimulates Macrophages and Inhibits Tumor Growth for Enhanced Immunotherapy

Gold nanoparticle accumulation in immune cells has commonly been viewed as a side effect for cancer therapeutic delivery; however, this phenomenon can be utilized for developing gold nanoparticle mediated immunotherapy. Here, we conjugated a modified CpG oligodeoxynucleotide immune stimulant to gold nanoparticles using a simple and scalable selfassembled monolayer scheme that enhanced the functionality of CpG in vitro and in vivo. Nanoparticles can attenuate systemic side effects by enhancing CpG delivery passively to innate effector cells. The use of a triethylene glycol (TEG) spacer on top of the traditional poly-thymidine spacer increased CpG macrophage stimulatory effects without sacrificing DNA content on the nanoparticle, which directly correlates to particle uptake. In addition, the immune effects of modified CpGAuNPs were altered by the core particle size, with smaller 15 nm AuNPs generating maximum immune response. These TEG modified CpG-AuNP complexes induced macrophage and dendritic cell tumor infiltration, significantly inhibited tumor growth, and promoted survival in mice when compared to treatments with free CpG

PTT promotes the expansion of adoptively transferred pmel T cells.

<p>Primary B16-F10 tumors were established on day 0, and contralateral tumors were established on day 6. Primary tumors were ablated by PTT on day 10 followed by pmel ATCT on day 11. On day 20, mice were euthanized and tissues were harvested for analysis. IFN-γ secretion in response to hgp100 by cells isolated from the (<b>A</b>) spleen and (<b>B</b>) TDLN. Treatment groups consisted of untreated tumor bearing mice (n = 5), PTT alone (n = 4), ATCT alone (n = 5), and dual PTT/ATCT (n = 5). The data is representative of two or more experiments. *p<0.05, **p<0.01; ANOVA followed by Student's t-test with multiple comparison adjustment.</p

PTT induces systemic effects that influence T cell and MDSC tumor infiltration.

<p>B16-OVA tumors were established on opposing flanks on days 0 and 7, respectively. Primary tumors were ablated by PTT on day 14. Mice were euthanized on day 23 for analysis of contralateral tumors. The control group consisted of untreated tumor-bearing mice (Ctrl: n = 4, PTT: n = 5). (<b>A</b>) IFN-γ ELISpot assay using CD8⁺ splenocytes stimulated using LPS-matured DC pulsed with tumor-lysate. (<b>B</b>) Representative FACS plots and corresponding quantitative data demonstrating (<b>C</b>) CD8⁺ and (<b>D</b>) CD4⁺ T cells infiltrating contralateral tumor sites. (<b>E</b>) Representative FACS plots and corresponding quantitative data demonstrating (<b>F</b>) CD4⁺FoxP3⁺ Treg cells and (<b>G</b>) CD4⁺FoxP3⁻ Thelper cells within contralateral tumor sites. (<b>H</b>) Teffector:Treg and (<b>I</b>) Thelper:Treg ratios within contralateral tumors. (<b>J</b>) Representative FACS plots and corresponding quantitative data measuring (<b>K</b>) CD11b⁺Ly-6G/C⁻ macrophages and (<b>L</b>) CD11b⁺Ly-6G/C⁺ MDSC within contralateral tumor sites. Red line represents the mean. The data is representative of two or more experiments. *p<0.05; z-test.</p

PTT induces the maturation of DC within TDLN.

<p>. B16-F10 tumor bearing mice were treated with PTT. 48 hours post-PTT, TDLN were isolated and stained with antibodies to CD11c, CD80, CD86, CD40 and I-A/I-E and analyzed by flow cytometry. DC maturation was assessed by gating on viable CD11c⁺ cells. Untreated tumor-bearing mice were used as controls (n = 3 per group). (<b>A</b>) Representative FACS plots of CD80, CD86, CD40 and I-A/I-E expression. (<b>B</b>) Corresponding mean fluorescent intensity (MFI) quantification of CD80 and I-A/I-E expression. Data represent the mean +/− SD. *p<0.05; Student's t-test.</p