Proline-serine-threonine phosphatase interacting protein 1 (PSTPIP1) controls immune synapse stability in human T cells.

BACKGROUND: Proline-serine-threonine phosphatase interacting protein 1 (PSTPIP1) is a cytosolic adaptor protein involved with T-cell activation, differentiation, and migration. On cognate T-cell contact, PSTPIP1 is recruited to surface-expressed CD2, where it regulates F-actin remodeling. An immune synapse (IS) is thereby rapidly formed, consisting of T-cell receptor clusters surrounded by a ring of adhesion molecules, including CD2. OBJECTIVE: From genetic screening of patients with primary immunodeficiencies, we identified 2 mutations in PSTPIP1, R228C and T274M, which we further characterized in the primary patients' T cells. METHODS: F-actin dynamics were assessed in primary T cells from the patients and control subjects by using fluorescence-activated cell sorting. HEK293T and Jurkat cells were transfected with R228C, T274M, and wild-type PSTPIP1 to visualize F-actin in IS formation. CD2-PSTPIP1 association was quantified through immunoprecipitation assays. RESULTS: The patients presented with immunodeficiency without signs of autoinflammation. The patient with the R228C mutation had expansion of mostly naive phenotype T cells and few memory T cells; the patient with the T274M mutation had 75% reduction in CD4 T cells that were predominantly of the memory subset. We observed F-actin polymerization defects in T cells from both patients with PSTPIP1, most notably the patient with the T274M mutation. Capping of CD2-containing membrane microdomains was disrupted. Analysis of IS formation using Jurkat T-cell transfectants revealed a reduction in F-actin accumulation at the IS, again especially in cells from the patient with the T274M PSTPIP1 mutation. T cells from the patient with the T274M mutation migrated spontaneously at increased speed, as assessed in a 3-dimensional collagen matrix, whereas T-cell receptor cross-linking induced a significantly diminished calcium flux. CONCLUSIONS: We propose that PSTPIP1 T-cell differentiation defects are caused by defective control of F-actin polymerization. A preactivated polymerized F-actin status, as seen in T cells from patients with the PSTPIP1 T274M mutation, appears particularly damaging. PSTPIP1 controls IS formation and cell adhesion through its function as an orchestrator of the F-actin cytoskeleton.

Recent advancements in mechanical reduction methods: particulate systems.

The screening of new active pharmaceutical ingredients (APIs) has become more streamlined and as a result the number of new drugs in the pipeline is steadily increasing. However, a major limiting factor of new API approval and market introduction is the low solubility associated with a large percentage of these new drugs. While many modification strategies have been studied to improve solubility such as salt formation and addition of cosolvents, most provide only marginal success and have severe disadvantages. One of the most successful methods to date is the mechanical reduction of drug particle size, inherently increasing the surface area of the particles and, as described by the Noyes-Whitney equation, the dissolution rate. Drug micronization has been the gold standard to achieve these improvements; however, the extremely low solubility of some new chemical entities is not significantly affected by size reduction in this range. A reduction in size to the nanometric scale is necessary. Bottom-up and top-down techniques are utilized to produce drug crystals in this size range; however, as discussed in this review, top-down approaches have provided greater enhancements in drug usability on the industrial scale. The six FDA approved products that all exploit top-down approaches confirm this. In this review, the advantages and disadvantages of both approaches will be discussed in addition to specific top-down techniques and the improvements they contribute to the pharmaceutical field.

Intratumoral expression of IL-12 from lentiviral or RNA vectors acts synergistically with TLR4 agonist (GLA) to generate anti-tumor immunological memory.

Systemic interleukin-12 (IL12) anti-tumor therapy is highly potent but has had limited utility in the clinic due to severe toxicity. Here, we present two IL12-expressing vector platforms, both of which can overcome the deficiencies of previous systemic IL12 therapies: 1) an integrating lentiviral vector, and 2) a self-replicating messenger RNA formulated with polyethyleneimine. Intratumoral administration of either IL12 vector platform resulted in recruitment of immune cells, including effector T cells and dendritic cells, and the complete remission of established tumors in multiple murine models. Furthermore, concurrent intratumoral administration of the synthetic TLR4 agonist glucopyranosyl lipid A formulated in a stable emulsion (GLA-SE) induced systemic memory T cell responses that mediated complete protection against tumor rechallenge in all survivor mice (8/8 rechallenged mice), whereas only 2/6 total rechallenged mice treated with intratrumoral IL12 monotherapy rejected the rechallenge. Taken together, expression of vectorized IL12 in combination with a TLR4 agonist represents a varied approach to broaden the applicability of intratumoral immune therapies of solid tumors.

ZVex™, a dendritic-cell-tropic lentivector, primes protective antitumor T cell responses that are significantly boosted using heterologous vaccine modalities.

Therapeutic cancer vaccines must induce high levels of tumor-specific cytotoxic CD8 T cells to be effective. We show here that tumor-antigen specific effector and memory T cell responses primed with a non-integrating, dendritic-cell targeted lentiviral vector (ZVex™) could be boosted significantly by either adjuvanted recombinant protein, adenoviral vectors, or self-replicating RNA. These heterologous prime-boost regimens also provided significantly better protection in murine tumor models. In contrast, homologous prime-boost regimens, or using the lentiviral vector as a boost, resulted in lower T cell responses with limited therapeutic efficacy. Heterologous prime-boost regimens that utilize ZVex as the prime may be attractive modalities for therapeutic cancer vaccines.

Intratumoral immune activation with TLR4 agonist synergizes with effector T cells to eradicate established murine tumors.

Effective T cell-based immunotherapy of solid malignancies requires intratumoral activity of cytotoxic T cells and induction of protective immune memory. A major obstacle to intratumoral trafficking and activation of vaccine-primed or adoptively transferred tumor-specific T cells is the immunosuppressive tumor microenvironment (TME), which currently limits the efficacy of both anti-tumor vaccines and adoptive cell therapy (ACT). Combination treatments to overcome TME-mediated immunosuppression are therefore urgently needed. We combined intratumoral administration of the synthetic toll-like receptor 4 agonist glucopyranosyl lipid A (oil-in-water formulation, G100) with either active vaccination or adoptive transfer of tumor-specific CD8 T cells to mice bearing established melanomas or orthotopically inoculated glioblastomas. In combination with cancer vaccines or ACT, G100 significantly increased expression of innate immune genes, infiltration and expansion of activated effector T cells, antigen spreading, and durable immune responses. Complete tumor regression of both injected and non-injected tumors was observed only in mice receiving combination immunotherapy. TLR4-based intratumoral immune activation may be a viable approach to enhance the efficacy of therapeutic cancer vaccines and ACT in patients.

A synthetic stroma-free germinal center niche for efficient generation of humoral immunity ex vivo.

B cells play a major role in the adaptive immune response by producing antigen-specific antibodies against pathogens and imparting immunological memory. Following infection or vaccination, antibody-secreting B cells and memory B cells are generated in specialized regions of lymph nodes and spleens, called germinal centers. Here, we report a fully synthetic ex-vivo system that recapitulates the generation of antigen-specific germinal-center (GC) like B cells using material-surface driven polyvalent signaling. This synthetic germinal center (sGC) reaction was effectively induced using biomaterial-based artificial "follicular T helper cells (TFH)" that provided both natural CD40-CD40L ligation as well as crosslinking of CD40 and by mimicking artificial "follicular dendritic cells (FDC)" to provide efficient, polyvalent antigen presentation. The artificial sGC reaction resulted in efficient B cell expansion, immunoglobulin (Ig) class switching, and expression of germinal center phenotypes. Antigen presentation during sGC reaction selectively enhanced the antigen-specific B cell population and induced somatic hyper-mutations for potential affinity maturation. The resulting B cell population consisted primarily of GC-like B cells (centrocytes) as well as some plasma-like B cells expressing CD138. With concurrent cell sorting, we successfully created highly enriched populations of antigen-specific B cells. Adoptive transfer of these GC-like B cells into non-irradiated isogeneic or non-lethally irradiated congenic recipient mice showed successful engraftment and survival of the donor cells for the 4 week test period. We show that this material-surface driven sGC reaction can be successfully applied to not only splenic B cells but also B cells isolated from more therapeutically relevant sources such as peripheral blood mononuclear cells (PBMCs), thus making our current work an exciting prospect in the new era of personalized medicine and custom-immunotherapy.

Biophysical Attributes of CpG Presentation Control TLR9 Signaling to Differentially Polarize Systemic Immune Responses.

It is currently unknown whether and how mammalian pathogen recognition receptors (PRRs) respond to biophysical patterns of pathogen-associated molecular danger signals. Using synthetic pathogen-like particles (PLPs) that mimic physical properties of bacteria or large viruses, we have discovered that the quality and quantity of Toll-like receptor 9 (TLR9) signaling by CpG in mouse dendritic cells (mDCs) are uniquely dependent on biophysical attributes; specifically, the surface density of CpG and size of the presenting PLP. These physical patterns control DC programming by regulating the kinetics and magnitude of MyD88-IRAK4 signaling, NF-κB-driven responses, and STAT3 phosphorylation, which, in turn, controls differential T cell responses and in vivo immune polarization, especially T helper 1 (Th1) versus T helper 2 (Th2) antibody responses. Our findings suggest that innate immune cells can sense and respond not only to molecular but also pathogen-associated physical patterns (PAPPs), broadening the tools for modulating immunity and helping to better understand innate response mechanisms to pathogens and develop improved vaccines.

A simple, clinically relevant therapeutic vaccine shows long-term protection in an aggressive, delayed-treatment B lymphoma model.

Despite initial remission after successful treatments, B lymphoma patients often encounter relapses and resistance causing high mortality. Thus, there is a need to develop therapies that prevent relapse by providing long-term protection and, ultimately, lead to functional cure. In this study, our goal was to develop a simple, clinically relevant, and easily translatable therapeutic vaccine that provides durable immune protection against aggressive B cell lymphoma and identify critical immune biomarkers that are predictive of long-term survival. In a delayed-treatment, aggressive, murine model of A20 B lymphoma that mimics human diffuse large B cell lymphoma, we show that therapeutic A20 lysate vaccine adjuvanted with an NKT cell agonist, α-galactosylceramide (α-GalCer), provides long-term immune protection against lethal tumor challenges and the antitumor immunity is primarily CD8 T cell dependent. Using experimental and computational methods, we demonstrate that the initial strength of germinal center reaction and the magnitude of class-switching into a Th1 type humoral response are the best predictors for the long-term immunity of B lymphoma lysate vaccine. Our results not only provide fundamentally insights for successful immunotherapy and long-term protection against B lymphomas, but also present a simple, therapeutic vaccine that can be translated easily due to the facile and inexpensive method of preparation.

Surface-Presentation of CpG and Protein-Antigen on Pathogen-Like Polymer Particles Generate Strong Prophylactic and Therapeutic Antitumor Protection.

Despite significant efforts, development of clinically relevant prophylactic and therapeutic cancer vaccines has proven challenging. Cancer-associated antigens, which are often self-antigens, do not activate innate immune cells sufficiently, underscoring the need for codelivery of appropriate immune-stimulatory adjuvants. Recent research has underscored the need for biomaterial-based carriers for vaccine delivery, not only to target antigens and adjuvants to antigen-presenting cells or to create "depot" like systems but also to avoid acute systemic toxicity of molecular adjuvants that occurs when adjuvants are delivered in their "naked" form. The work presented here focuses on surface-presentation of both antigens and adjuvants on a pathogen-like particle (PLP) platform and understanding how PLP-induced antitumor responses differ when protein antigens and adjuvants, specifically the TLR9 agonist CpG, are delivered on the surface of the same particle (dual-loaded) versus being codelivered on separate particles. Surface-presentation allows easier access of antigens and adjuvants to intracellular targets (e.g., to TLR9 in the phagosomal compartments) and also allows controlled multivalent presentation. Our results show that, surface presentation, as opposed to soluble molecules, was more efficient in activating dendritic cells (DCs) and polarizing them toward generating a stronger cytotoxic T cell response. Signaling and DC polarization between separate and dual-loaded particles were similar, although NF-kB signaling at higher doses was stronger in dual-loaded PLPs. In vivo, dual loaded PLPs performed better than separately loaded PLPs in a prophylactic tumor model of melanoma and were comparable to immunization using incomplete Freud's adjuvant (IFA). In contrast both PLP-based delivery modalities performed similarly in a therapeutic melanoma-vaccine model and significantly outperformed IFA-based vaccination. These results indicate that surface-presentation of antigens and adjuvants on polymer-particles is a promising modality for efficient anticancer vaccines.

Engineering immunity: Modulating dendritic cell subsets and lymph node response to direct immune-polarization and vaccine efficacy.

While successful vaccines have been developed against many pathogens, there are still many diseases and pathogenic infections that are highly evasive to current vaccination strategies. Thus, more sophisticated approaches to control the type and quality of vaccine-induced immune response must be developed. Dendritic cells (DCs) are the sentinels of the body and play a critical role in immune response generation and direction by bridging innate and adaptive immunity. It is now well recognized that DCs can be separated into many subgroups, each of which has a unique function. Better understanding of how various DC subsets, in lymphoid organs and in the periphery, can be targeted through controlled delivery; and how these subsets modulate and control the resulting immune response could greatly enhance our ability to develop new, effective vaccines against complex diseases. In this review, we provide an overview of DC subset biology and discuss current immunotherapeutic strategies that utilize DC targeting to modulate and control immune responses.

The effect of combined IL10 siRNA and CpG ODN as pathogen-mimicking microparticles on Th1/Th2 cytokine balance in dendritic cells and protective immunity against B cell lymphoma.

Success of an immunotherapy for cancer often depends on the critical balance of T helper 1 (Th1) and T helper 2 (Th2) responses driven by antigen presenting cells, specifically dendritic cells (DCs). Th1-driven cytotoxic T cell (CTL) responses are key to eliminating tumor cells. It is well established that CpG oligonucleotides (ODN), a widely studied Toll-like receptor 9 (TLR9) agonist, used to enhance Th1 response, also induces high levels of the anti-inflammatory, Th2-promoting cytokine IL10, which could dampen the resulting Th1 response. Biomaterials-based immunomodulatory strategies that can reduce IL10 production while maintaining IL12 levels during CpG delivery could further enhance the Th1/Th2 cytokine balance and improve anti-tumor immune response. Here we report that dual-delivery of IL10-silencing siRNA along with CpG ODN to the same DCs using pathogen-mimicking microparticles (PMPs), significantly enhances their Th1/Th2 cytokine ratio through concurrent inhibition of CpG-induced IL10 production. Co-delivery of poly(I:C), a TLR3 agonist had only minor effects on IL10 levels. Further, simultaneous immunotherapy with CpG ODN and IL10 siRNA enhanced immune protection of an idiotype DNA vaccine in a prophylactic murine model of B cell lymphoma whereas co-delivery of poly(I:C) and CpG did not enhance protection. These results suggest that PMPs can be used to precisely modulate TLR ligand-mediated immune-stimulation in DCs, through co-delivery of cytokine-silencing siRNAs and thereby boost antitumor immunity.

Micro and nanoparticle-based delivery systems for vaccine immunotherapy: an immunological and materials perspective.

The development and widespread application of vaccines has been one of the most significant achievements of modern medicine. Vaccines have not only been instrumental in controlling and even eliminating life-threatening diseases like polio, measles, diphtheria, etc., but have also been immensely powerful in enhancing the worldwide outlook of public health over the past century. Despite these successes, there are still many complex disorders (e.g., cancer, HIV, and other emerging infectious diseases) for which effective preventative or therapeutic vaccines have been difficult to develop. This failure can be attributed primarily to our inability to precisely control and modulate the highly complex immune memory response, specifically the cellular response. Dominated by B and T cell maturation and function, the cellular response is primarily initiated by potent immunostimulators and antigens. Efficient and targeted delivery of these immunomodulatory and immunostimulatory molecules to appropriate cells is key to successful development of next generation vaccine formulations. Over the past decade, particulate carriers have emerged as an attractive means for enhancing the delivery efficacy and potency of vaccines and associated immunomodulatory molecules. Specifically, polymer-based micro and nanoparticles are being extensively studied for a wide variety of applications. In this review, we discuss the immunological fundamentals for developing effective vaccines and how materials and material properties can be exploited to improve these therapies. Particular emphasis is given to polymer-based particles and how the route of administration of particulate systems affects the phenotype and robustness of an immune response. Comparison of various strategies and recent advancements in the field are discussed along with insights into current limitations and future directions.

Effects of shear stress on germ lineage specification of embryonic stem cells.

Mechanobiology to date has focused on differentiated cells or progenitors, yet the effects of mechanical forces on early differentiation of pluripotent stem cells are still largely unknown. To study the effects of cellular deformation, we utilize a fluid flow bioreactor to apply steady laminar shear stress to mouse embryonic stem cells (ESCs) cultured on a two dimensional surface. Shear stress was found to affect pluripotency, as well as germ specification to the mesodermal, endodermal, and ectodermal lineages, as indicated by gene expression of OCT4, T-BRACHY, AFP, and NES, respectively. The ectodermal and mesodermal response to shear stress was dependent on stress magnitude (ranging from 1.5 to 15 dynes cm(-2)). Furthermore, increasing the duration from one to four days resulted in a sustained increase in T-BRACHY and a marked suppression of AFP. These changes in differentiation occurred concurrently with the activation of Wnt and estrogen pathways, as determined by PCR arrays for signalling molecules. Together these studies show that the mechanical microenvironment may be an important regulator during early differentiation events, including gastrulation. This insight furthers understanding of normal and pathological events during development, as well as facilitates strategies for scale up production of stem cells for clinical therapies.