Arming Tumor-Reactive T Cells with Costimulator B7-1 Enhances Therapeutic Efficacy of the T Cells

Lipid-Polymer Hybrid Nanoparticles Utilize B Cells and Dendritic Cells to Elicit Distinct Antigen-Specific CD4+ and CD8+ T Cell Responses

Antigen-presenting cells (APCs) are widely studied for treating immune-mediated diseases, and dendritic cells (DCs) are potent APCs that uptake and present antigens (Ags). However, DCs face several challenges that hinder their clinical translation due to their inability to control Ag dosing and low abundance in peripheral blood. B cells are a potential alternative to DCs, but their poor nonspecific Ag uptake capabilities compromise controllable priming of T cells. Here, we developed phospholipid-conjugated Ags (L-Ags) and lipid-polymer hybrid nanoparticles (L/P-Ag NPs) as delivery platforms to expand the range of accessible APCs for use in T cell priming. These delivery platforms were evaluated using DCs, CD40-activated B cells, and resting B cells to understand the impacts of various Ag delivery mechanisms for generation of Ag-specific T cell responses. L-Ag delivery (termed depoting) of MHC class I- and II-restricted Ags successfully loaded all APC types in a tunable manner and primed both Ag-specific CD8+ and CD4+ T cells, respectively. Incorporating L-Ags and polymer-conjugated Ags (P-Ag) into NPs can direct Ags to different uptake pathways to engineer the dynamics of presentation and shape T cell responses. DCs were capable of processing and presenting Ag delivered from both L- and P-Ag NPs, yet B cells could only utilize Ag delivered from L-Ag NPs, which led to differential cytokine secretion profiles in coculture studies. Altogether, we show that L-Ags and P-Ags can be rationally paired within a single NP to leverage distinct delivery mechanisms to access multiple Ag processing pathways in two APC types, offering a modular delivery platform for engineering Ag-specific immunotherapies.

Lipid-Mediated Insertion of Toll-Like Receptor (TLR) Ligands for Facile Immune Cell Engineering

Cell-based immunotherapies have tremendous potential to treat many diseases, such as activating immunity in cancer or suppressing it in autoimmune diseases. Most cell-based cancer immunotherapies in the clinic provide adjuvant signals through genetic engineering to enhance T cell functions. However, genetically encoded signals have minimal control over dosing and persist for the life of a cell lineage. These properties make it difficult to balance increasing therapeutic efficacy with reducing toxicities. Here, we demonstrated the potential of phospholipid-coupled ligands as a non-genetic system for immune cell engineering. This system provides simple, controlled, non-genetic adjuvant delivery to immune cells via lipid-mediated insertion into plasma membranes. Lipid-mediated insertion (termed depoting) successfully delivered Toll-like receptor (TLR) ligands intracellularly and onto cell surfaces of diverse immune cells. These ligands depoted into immune cells in a dose-controlled fashion and did not compete during multiplex pairwise loading. Immune cell activation could be enhanced by autocrine and paracrine mechanisms depending on the biology of the TLR ligand tested. Depoted ligands functionally persisted on plasma membranes for up to 4 days in naïve and activated T cells, enhancing their activation, proliferation, and skewing cytokine secretion. Our data showed that depoted ligands provided a persistent yet non-permanent adjuvant signal to immune cells that may minimize the intensity and duration of toxicities compared to permanent genetic delivery. Altogether, these findings demonstrate potential for lipid-mediated depoting as a universal cell engineering approach with unique, complementary advantages to other cell engineering methods.

Strategies for cell membrane functionalization

The ability to rationally manipulate and augment the cytoplasmic membrane can be used to overcome many of the challenges faced by conventional cellular therapies and provide innovative opportunities when combined with new biotechnologies. The focus of this review is on emerging strategies used in cell functionalization, highlighting both pioneering approaches and recent developments. These will be discussed within the context of future directions in this rapidly evolving field.

A DNA vaccine encoding mutated HPV58 mE6E7-Fc-GPI fusion antigen and GM-CSF and B7.1

BACKGROUND

Persistent infection with high-risk human papillomavirus (HPV) is a predominant cause of cervical cancer, and HPV58 is the third most common virus detected in the patients with cervical cancer in Asia. E6 and E7 are the viral oncogenes which are constitutively expressed in HPV-associated tumor cells and can be used as target antigens for related immunotherapy. In this study, we modified the HPV58 E6 and E7 oncogenes to eliminate their oncogenic potential and constructed a recombinant DNA vaccine that coexpresses the sig-HPV58 mE6E7-Fc-GPI fusion antigen in addition to granulocyte-macrophage colony-stimulating factor (GM-CSF) and B7.1 as molecular adjuvants (PVAX1-HPV58 mE6E7FcGB) for the treatment of HPV58 (+) cancer.

METHODS

PVAX1-HPV58 mE6E7FcGB recombinant DNA vaccine was constructed to express a fusion protein containing a signal peptide, a modified HPV58 mE6E7 gene, and human IgG Fc and glycosylphosphatidylinositol (GPI)-anchoring sequences using the modified DNA vaccine vector PVAX1-IRES-GM/B7.1 that coexpresses GM-CSF, and B7.1. C57BL/6 mice were challenged by HPV58 E6E7-expressing B16-HPV58 E6E7 cells, followed by immunization by PVAX1-HPV58 mE6E7FcGB vaccine on days 7, 14, 21 after tumor challenge. The cellular immune responses in immunized mice were assessed by measuring IFN-γ production in splenocytes upon stimulation by HPV58 E6E7-GST protein and the lysis of B16-HPV58 E6E7 target cells by splenocytes after restimulation with HPV58 E6E7-GST protein. The antitumor efficacy was evaluated by monitoring the growth of the tumor.

RESULTS

PVAX1-HPV58 mE6E7FcGB elicited varying levels of IFN-lsgdB58onn T-cell immune responses and lysis of target cell in mice in response to the recombinant antigen HPV58 E6E7-GST. Furthermore, the vaccine also induced antitumor responses in the HPV58 (+) B16-HPV58 E6E7 tumor challenge model as evidenced by delayed tumor development.

CONCLUSION

The recombinant DNA vaccine PVAX1-HPV58 mE6E7FcGB efficiently generates cellular immunity and antitumor efficacy in immunized mice. These data provide a basis for the further study of this recombinant vaccine as a potential candidate vaccine.

Palmitate-derivatized human IL-2: a potential anticancer immunotherapeutic of low systemic toxicity

PURPOSE AND EXPERIMENTAL DESIGN

Recombinant human IL-2 (rhIL-2) is a potent cytokine and FDA-approved anticancer drug. However, its clinical use has been limited by severe toxicity, associated primarily with systemic administration with excess protein distributing freely throughout the body. We hypothesized that rhIL-2 in alternate forms permitting more restricted localization may exert stronger antitumor efficacy and less toxicity. Here, we have tested the utility of palmitate-derivatized rhIL-2. rhIL-2 was reacted with N-hydroxysuccinimide palmitate ester. The resultant lipidated rhIL-2 (pIL-2), when mixed with cells, could spontaneously transfer from solution to cell surfaces. Next, anticancer efficacy of pIL-2 was assessed in two modalities. For adoptive T cell therapy, antitumor cytotoxic T cells (CTLs) were protein transferred ("painted") with pIL-2 and injected into mice bearing lymphoma. For in situ therapy, pIL-2 was injected intratumorally into mice bearing melanoma. Tumor growth and IL-2-associated toxicity were determined.

RESULTS

In the lymphoma model, painting of the antitumor CTLs with pIL-2 markedly increased their viability and titer. In the melanoma model, intratumoral injection of pIL-2, but not rhIL-2, increased the number of activated CD8(+) T cells (IFN-γ(+)) in the spleen, reduced lung metastasis and prolonged the survival of treated mice. Moreover, while repeated intratumoral injection of rhIL-2 at an excessively high dose (10 injections of 10,000 IU/mouse) caused marked vascular leakage syndrome, the same regimen using pIL-2 caused no detectable toxicity.

CONCLUSIONS

Transferring spontaneously from solution to cell surfaces, pIL-2 may bypass the current limitations of rhIL-2 and, thus, serve as a more effective and tolerable anticancer drug.

Integrating individual functional moieties of CXCL10 and CXCL11 into a novel chimeric chemokine leads to synergistic antitumor effects: a strategy for chemokine-based multi-target-directed cancer therapy

The complexity of tumor biology necessitates a multimodality approach that targets different aspects of tumor environment in order to generate the greatest benefit. IFN-inducible T cell alpha chemoattractant (ITAC)/CXCL11 and IFN-inducible protein 10 (IP10)/CXCL10 could exert antitumor effects with functional specificity and thus emerge as attractive candidates for combinatorial strategy. Disappointedly, a synergistic antitumor effect could not be observed when CXCL10 and CXCL11 were pooled together. In this regard, we seek to improve antitumor efficacy by integrating their individual functional moieties into a chemokine chimeric molecule, designated ITIP, which was engineered by substituting the N-terminal and N-loop region of CXCL10 with those of CXCL11. The functional properties of ITIP were determined by chemotaxis and angiogenesis assays. The antitumor efficacy was tested in murine CT26 colon carcinoma, 4T1 mammary carcinoma and 3LL lung carcinoma. Here we showed that ITIP not only exhibited respective functional superiority but strikingly promoted regression of established tumors and remarkably prolonged survival of mice compared with its parent chemokines, either alone or in combination. The chemokine chimera induced an augmented anti-tumor immunity and a marked decrease in tumor vasculature. Antibody neutralization studies indicated that CXCL10 and CXCL11 moieties of ITIP were responsible for anti-angiogenesis and chemotaxis in antitumor response, respectively. These results indicated that integrating individual functional moieties of CXCL10 and CXCL11 into a chimeric chemokine could lead to a synergistic antitumor effect. Thus, this integration strategy holds promise for chemokine-based multiple targeted therapy of cancer.

Protein transfer enhances cellular immune responses to DNA vaccination against SARS-CoV

The current DNA vaccine formulations are not optimal for stimulation of CD8(+) T cells, which are required for clearing virally-infected cells. Here we show that CD8(+) T cell-stimulating activity can be effectively augmented by combining DNA vaccination with protein transfer. C57BL/6 mice were injected intramuscularly with an anti-SARS-CoV DNA vaccine admixed with a lipid-derived conjugate of 4-1BBL, a potential CD8(+) T-cell co-stimulator. The inclusion of the lipidated co-stimulator greatly enhanced cellular immune responses, especially the CTL response, induced by the DNA vaccine. The adjuvant effect of 4-1BBL was lipidation-dependent, indicating that it functions as a cell membrane-anchored co-stimulator. Results of our study suggest, for the first time, that muscle cells may be modified in situ, at the DNA injection site, into APC-like cells to allow direct priming of CD8(+) T cells and thereby improve the efficacy of DNA vaccines.

Enhanced antitumor responses elicited by combinatorial protein transfer of chemotactic and costimulatory molecules

Thus far, immunotherapies based on one or a few immunostimulatory molecules have shown limited antitumor efficacy. This highlights the need to use multiple immunostimulatory molecules, to target different immune cells, including immunosuppressive cells, simultaneously. Consequently, in this study, we delivered intratumorally via protein transfer four molecules, including the chemotactic molecules secondary lymphoid tissue chemokine and Fas ligand and the costimulatory molecules 4-1BBL and TNF-related activation-induced cytokine. Secondary lymphoid tissue chemokine and Fas ligand together can attract an array of immune cells and induce apoptosis in CD4(+)CD25(+) regulatory T cells (Treg), whereas 4-1BBL and TRANCE together can stimulate T cells and dendritic cells (DCs). We show that the transfer of all four molecules increases tumor-infiltrating neutrophils, DCs, and CD4(+) and CD8(+) T cells and decreases intratumoral Treg. We show that the treatment favors the generation of a Th1 cytokine milieu at the tumor site, which is attributed not only to an increase in IL-12-producting DCs and IFN-gamma-producing CD8(+) T cells, but also to a decrease in IL-10-producing Treg. Importantly, in the L5178Y lymphoma model, we show that compared with transfer of the chemotactic molecules alone or the costimulatory molecules alone, transfer of all four molecules demonstrates stronger antitumor responses against established tumors. Furthermore, we show that the antitumor responses elicited by transfer of all four molecules are mediated by long-term, systemic antitumor immunity. Hence, this study demonstrates for the first time that combinatorial use of chemotactic and costimulatory molecules provides a useful strategy for enhancing antitumor responses.

Depleting intratumoral CD4+CD25+ regulatory T cells via FasL protein transfer enhances the therapeutic efficacy of adoptive T cell transfer

One strategy for improving adoptive therapy is preconditioning the host immune environment by depleting CD4(+)CD25(+) regulatory T cells (Treg) suppressive to antitumor responses. Given that Treg increase, or selectively accumulate, within tumors and are sensitive to FasL-mediated apoptosis, we test here the hypothesis that inducing apoptosis of intratumoral Treg using FasL may improve adoptive T cell therapy. We show that FasL applied intratumorally via protein transfer decreases intratumoral Treg via inducing apoptosis in these cells. Significantly, we show that the use of FasL prior to the infusion of tumor-reactive CD8(+) T cells enhances the therapeutic efficacy of adoptive T cell transfer against established tumors, which is mediated by persistent, systemic antitumor immunity. Intratumoral FasL protein transfer also results in neutrophil infiltration of tumor. However, we show that intratumoral immunodepletion of neutrophils does not abolish the effect of FasL on adoptive transfer. Rather, the effect of FasL is completely abolished by cotransfer of Treg, isolated from the tumor-draining lymph nodes. Hence, our study shows for the first time that using FasL to predeplete intratumoral Treg provides a useful means for optimizing adoptive therapy.

Modifying Dendritic Cells via Protein Transfer for Antitumor Therapeutics

PURPOSE

The modification of therapeutic dendritic cells (DC) with various immunostimulatory molecules represents a useful means for improving the antitumor efficacy of DC transfer-based immunotherapy. We have evaluated the feasibility of modifying therapeutic DCs with multiple immunostimulatory molecules using a time-efficient, protein transfer (or protein "painting")-based method.

EXPERIMENTAL DESIGN

Bone marrow-derived DCs were painted with either control protein human IgG (hIgG) or three immunostimulatory molecules, SLC, 4-1BBL, and TRANCE (the triad protein). Painted DCs were injected intratumorally into mice bearing established tumors. Subsequently, the capacities of painted DCs to migrate to the draining lymph nodes, recruit the host T cells, promote Th1 cytokine responses, and elicit therapeutic antitumor responses were evaluated.

RESULTS

The triad protein transfer yields a uniform population of DCs that coexpress all three of the proteins. Compared with the hIgG-painted DCs, the triad protein-painted DCs migrate more efficiently to the draining lymph nodes and show enhanced capabilities to induce T cell infiltration of tumors and to promote Th1 cytokine responses in vivo. Furthermore, in both the EG.7 and TRAMP-C2 tumor models, compared with the DCs painted with hIgG or only one of the three proteins, the triad protein-painted DCs, upon adoptive transfer, elicit stronger therapeutic responses against established tumors. Importantly, the antitumor responses of the triad protein-painted DCs are mediated by systemic antitumor immunity.

CONCLUSIONS

This study establishes, for the first time, the feasibility of optimizing DC transfer-based immunotherapy via combinatorial protein transfer of therapeutic DCs with an array of immunostimulatory molecules.

T Cell Tolerance to Tumors and Cancer Immunotherapy

It is widely recognized that the immune system plays a role in cancer progression and that some tumors are inherently immunogenic. The identification of tumor-associated antigens (TAAs) has stimulated research focused on immunotherapies to mediate the regression of established tumors. Cancer-specific immunity has traditionally been aimed at activating CD8+ cytotoxic T lymphocytes (CTLs) directed against major histocompatibility complex (MHC) class I-binding peptide epitopes. Other approaches utilize T cell adoptive therapy where autologous, tumor-specific T cells propagated in vitro are transferred back into recipients. However, these strategies have met with limited success in part due to the regulatory mechanisms of T cell tolerance, which poses a considerable challenge to cancer immunotherapy. Our laboratory utilizes the TRansgenic Adenocarcinoma of the Mouse Prostate (TRAMP) model, a murine model of prostate cancer, to study mechanisms of T cell tolerization to tumor antigens. We previously demonstrated that upon encounter with their cognate antigen in the tumor microenvironment, naive T cell become tolerized. Our ongoing studies are testing whether provision of CD4+ T cells can enhance tumor immunity by preventing CD8+ T cell tolerance. A greater understanding of the interaction between various tumor-specific T cell subsets will facilitate the design of novel approaches to stimulate a more potent antitumor immune response.