Nanoparticle dose and antigen loading attenuate antigen-specific T-cell responses.

Immune-mediated hypersensitivities such as autoimmunity, allergy, and allogeneic graft rejection are treated with therapeutics that suppress the immune system, and the lack of specificity is associated with significant side effects. The delivery of disease-relevant antigens (Ags) by carrier systems such as poly(lactide-co-glycolide) nanoparticles (PLG-Ag) and carbodiimide (ECDI)-fixed splenocytes (SP-Ag) has demonstrated Ag-specific tolerance induction in model systems of these diseases. Despite therapeutic outcomes by both platforms, tolerance is conferred with different efficacy. This investigation evaluated Ag loading and total particle dose of PLG-Ag on Ag presentation in a coculture system of dendritic cells (DCs) and Ag-restricted T cells, with SP-Ag employed as a control. CD25 expression was observed in nearly all T cells even at low concentrations of PLG-Ag, indicating efficient presentation of Ag by dendritic cells. However, the secretion of IL-2, Th1, and Th2 cytokines (IFNγ and IL-4, respectively) varied depending on PLG-Ag concentration and Ag loading. Concentration escalation of soluble Ag resulted in an increase in IL-2 and IFNγ and a decrease in IL-4. Treatment with PLG-Ag followed a similar trend but with lower levels of IL-2 and IFNγ secreted. Transcriptional Activity CEll ARrays (TRACER) were employed to measure the real-time transcription factor (TF) activity in Ag-presenting DCs. The kinetics and magnitude of TF activity was dependent on the Ag delivery method, concentration, and Ag loading. Ag positively regulated IRF1 activity and, as carriers, NPs and ECDI-treated SP negatively regulated this signaling. The effect of Ag loading and dose on tolerance induction were corroborated in vivo using the delayed-type hypersensitivity (DTH) and experimental autoimmune encephalomyelitis (EAE) mouse models where a threshold of 8 µg/mg Ag loading and 0.5 mg PLG-Ag dose were required for tolerance. Together, the effect of Ag loading and dosing on in vitro and in vivo immune regulation provide useful insights for translating Ag-carrier systems for the clinical treatment of immune disorders.

The early life microbiota protects neonatal mice from pathological small intestinal epithelial cell shedding.

The early life gut microbiota plays a crucial role in regulating and maintaining the intestinal barrier, with disturbances in these communities linked to dysregulated renewal and replenishment of intestinal epithelial cells. Here we sought to determine pathological cell shedding outcomes throughout the postnatal developmental period, and which host and microbial factors mediate these responses. Surprisingly, neonatal mice (Day 14 and 21) were highly refractory to induction of cell shedding after intraperitoneal administration of liposaccharide (LPS), with Day 29 mice showing strong pathological responses, more similar to those observed in adult mice. These differential responses were not linked to defects in the cellular mechanisms and pathways known to regulate cell shedding responses. When we profiled microbiota and metabolites, we observed significant alterations. Neonatal mice had high relative abundances of Streptococcus, Escherichia, and Enterococcus and increased primary bile acids. In contrast, older mice were dominated by Candidatus Arthromitus, Alistipes, and Lachnoclostridium, and had increased concentrations of SCFAs and methyamines. Antibiotic treatment of neonates restored LPS-induced small intestinal cell shedding, whereas adult fecal microbiota transplant alone had no effect. Our findings further support the importance of the early life window for microbiota-epithelial interactions in the presence of inflammatory stimuli and highlights areas for further investigation.

Rapid Reconstitution of the Fecal Microbiome after Extended Diet-Induced Changes Indicates a Stable Gut Microbiome in Healthy Adult Dogs.

The gut microbiome has an important role in health, and diet represents a key lever for shaping the gut microbiome across all stages of life. Maternal milk consumption in neonates leads to long-term health effects, indicating that pliability in the infant gut microbiome in response to diet can drive enduring change. The ability of diet to drive lasting changes in the adult gut microbiome is less understood. We studied the effect of an extreme dietary shift on the fecal microbiome of 46 Labrador retriever dogs (mean age, 4.6 years) over 11 months. Dogs were fed a nutritionally complete, commercially available complex diet (CD) for a minimum of 5 weeks, followed by highly purified diets (PDs) for 36 weeks, and the initial CD for at least a further 4 weeks. Fecal samples were collected at regular intervals for DNA extraction. By analyzing 16S rRNA genes and the metagenomes, we observed minor effects on microbial diversity but significant changes in bacterial taxa and genetic potential when a PD was fed. Specifically, metagenomics identified an enrichment of quinone- and GABA-related pathways on PD, providing insights into dietary effects on cross-feeding strategies impacting community structure. When dogs returned to the CD, no significant differences were found with the initial time point. These findings are consistent with the gut microbiome being rapidly adaptable but capable of being reconstituted when provided with similar diets. These data highlight that long-term changes in the adult dog gut microbiome may only be achieved through long-term maintenance on a specified diet, rather than through feeding a transitionary diet.IMPORTANCE Diet can influence the adult gut microbiome (the community of bacteria) and health outcomes, but the ability to make changes persisting beyond feeding of a particular diet is poorly understood. We investigated whether feeding highly purified diets to adult dogs for 36 weeks would alter bacterial populations sufficiently to result in a persistent change following the dogs' return to a commercial diet. As expected, the microbiome changed when the purified diet was fed, but the original microbiome was reconstituted within weeks of the dogs returning to the commercial diet. The significance of these findings is in identifying an intrinsic stability of the host microbiome in healthy dogs, suggesting that dietary changes to support adult dog health through modifying the gut microbiome may be achieved only through maintenance on a specified diet, rather than through feeding transitionary diets.

Conjugation of Transforming Growth Factor Beta to Antigen-Loaded Poly(lactide- co-glycolide) Nanoparticles Enhances Efficiency of Antigen-Specific Tolerance.

Current strategies for treating autoimmunity involve the administration of broad-acting immunosuppressive agents that impair healthy immunity. Intravenous (i.v.) administration of poly(lactide- co-glycolide) nanoparticles (NPs) containing disease-relevant antigens (Ag-NPs) have demonstrated antigen (Ag)-specific immune tolerance in models of autoimmunity. However, subcutaneous (s.c.) delivery of Ag-NPs has not been effective. This investigation tested the hypothesis that codelivery of the immunomodulatory cytokine, transforming growth factor beta 1 (TGF-ß), on Ag-NPs would modulate the immune response to Ag-NPs and improve the efficiency of tolerance induction. TGF-ß was coupled to the surface of Ag-NPs such that the loadings of Ag and TGF-ß were independently tunable. The particles demonstrated bioactive delivery of Ag and TGF-ß in vitro by reducing the inflammatory phenotype of bone marrow-derived dendritic cells and inducing regulatory T cells in a coculture system. Using an in vivo mouse model for multiple sclerosis, experimental autoimmune encephalomyelitis, TGF-ß codelivery on Ag-NPs resulted in improved efficacy at lower doses by i.v. administration and significantly reduced disease severity by s.c. administration. This study demonstrates that the codelivery of immunomodulatory cytokines on Ag-NPs may enhance the efficacy of Ag-specific tolerance therapies by programming Ag presenting cells for more efficient tolerance induction.

Controlled Delivery of Single or Multiple Antigens in Tolerogenic Nanoparticles Using Peptide-Polymer Bioconjugates.

Polymeric nanoparticles (NPs) have demonstrated their potential to induce antigen (Ag)-specific immunological tolerance in multiple immune models and are at various stages of commercial development. Association of Ag with NPs is typically achieved through surface coupling or encapsulation methods. However, these methods have limitations that include high polydispersity, uncontrollable Ag loading and release, and possible immunogenicity. Here, using antigenic peptides conjugated to poly(lactide-co-glycolide), we developed Ag-polymer conjugate NPs (acNPs) with modular loading of single or multiple Ags, negligible burst release, and minimally exposed surface Ag. Tolerogenic responses of acNPs were studied in vitro to decouple the role of NP size, concentration, and Ag loading on regulatory T cell (Treg) induction. CD4+CD25+Foxp3+ Treg induction was dependent on NP size, but CD25 expression of CD4+ T cells was not. NP concentration and Ag loading could be modulated to achieve maximal levels of Treg induction. In relapsing-remitting experimental autoimmune encephalomyelitis (R-EAE), a murine model of multiple sclerosis, acNPs were effective in inhibiting disease induced by a single peptide or multiple peptides. The acNPs provide a simple, modular, and well-defined platform, and the NP physicochemical properties offer potential to design and answer complex mechanistic questions surrounding NP-induced tolerance.

Characterisation of a canine epithelial cell line for modelling the intestinal barrier.

Little is known about how food interacts with the intestinal epithelium during the digestion process. However, it is known that ingredients in food can modulate the intestinal barrier, and have the potential to disrupt homeostasis of the gut. Here, we characterise a conditionally immortalised canine intestinal epithelial cell (cIEC) line for use in in vitro assays, to assess the effect of food ingredients on intestinal barrier function, permeability, cell health, and inflammation. Microscopy and flow cytometry confirmed that cIECs had a phenotype consistent with those of epithelial origin, and were able to differentiate to mature enterocytes. The cIECs also formed a monolayer when grown on Transwell® inserts, producing functional tight junctions between the cells. In contrast to the human-derived Caco-2 cell line, transepithelial electrical resistance (TEER) was increased in cIECs in response to two different raw ingredients. The exposure of cIECs to known inflammatory stimuli and raw ingredients induced the nuclear translocation of nuclear factor kappa-light-chain-enhancer of activated B-cells (NF-?B). This work demonstrates the value of a unique cIEC in vitro model to study the effects of food ingredients on canine intestinal function and health, and supports continued efforts to reduce and refine the use of animals in scientific research.

PILOT STUDY TO ASSESS MEAL PROGRESSION THROUGH THE GASTROINTESTINAL TRACT OF HABITUATED DOGS DETERMINED BY FLUOROSCOPIC IMAGING WITHOUT SEDATION OR PHYSICAL RESTRAINT.

A limiting factor of radiographic contrast studies is the requirement for restraint of the animal in order to reduce movement artifacts. To demonstrate that gastrointestinal transit can be analyzed by a barium meal in nonsedated and unrestrained dogs, a pilot study of six adult Labrador retriever dogs was undertaken. Study subjects were selected by convenience sampling from an available population of Labrador dogs and were trained to stand motionless during radiographic fluoroscopy. Following a meal containing 7% w/w powdered barium sulfate, radiographic images were generated using a digital fluoroscope C-arm, at intervals of 5, 15, and 30 min, and at 1, 2, 3, 4, 5, 6, 7, and 8 h. A qualitative assessment of fill density using a 5-point scale was made for the stomach, small intestine, and ascending, transverse, and descending regions of the colon at each timepoint. Gastric emptying half-time occurred between 1 and 2 h postmeal. Mean fill density of the small intestine increased from 15 min postmeal and reached a peak at 3 h postmeal. Mean fill density of the proximal large intestine mirrored that of the small intestine. The distal large intestine remained empty for the first 2 h postmeal, then increased between hours 2 and 5 postmeal, and was subsequently at maximum fill density from hour 6 postmeal onwards. Fluoroscopic observation of a barium contrast meal provided an effective indication of the amount and progression of ingested food through the various regions of the gastrointestinal tract in habituated, fully conscious dogs.

Heterogeneity in histone 2B-green fluorescent protein-retaining putative small intestinal stem cells at cell position 4 and their absence in the colon.

Stem cells have been identified in two locations in small intestinal crypts; those intercalated between Paneth cells and another population (which retains DNA label) are located above the Paneth cell zone, at cell position 4. Because of disadvantages associated with the use of DNA label, doxycycline-induced transient transgenic expression of histone 2B (H2B)-green fluorescent protein (GFP) was investigated. H2B-GFP-retaining putative stem cells were consistently seen, with a peak at cell position 4, over chase periods of up to 112 days. After a 28-day chase, a subpopulation of the H2B-GFP-retaining cells was cycling, but the slow cycling status of the majority was illustrated by lack of expression of pHistone H3 and Ki67. Although some H2B-GFP-retaining cells were sensitive to low-dose radiation, the majority was resistant to low- and high-dose radiation-induced cell death, and a proportion of the surviving cells proliferated during subsequent epithelial regeneration. Long-term retention of H2B-GFP in a subpopulation of small intestinal Paneth cells was also seen, implying that they are long lived. In contrast to the small intestine, H2B-GFP-retaining epithelial cells were not seen in the colon from 28-day chase onward. This implies important differences in stem cell function between these two regions of the gastrointestinal tract, which may have implications for region-specific susceptibility to diseases (such as cancer and ulcerative colitis), in which epithelial stem cells and their progeny are involved.

Mechanistic contributions of Kupffer cells and liver sinusoidal endothelial cells in nanoparticle-induced antigen-specific immune tolerance.

The intravenous delivery of disease-relevant antigens (Ag) by polymeric nanoparticles (NP-Ags) has demonstrated Ag-specific immune tolerance in autoimmune and allergic disorders as well as allogeneic transplant rejection. NP-Ags are observed to distribute to the spleen, which has an established role in the induction of immune tolerance. However, studies have shown that the spleen is dispensable for NP-Ag-induced tolerance, suggesting significant contributions from other immunological sites. Here, we investigated the tolerogenic contributions of Kupffer cells (KCs) and liver sinusoidal endothelial cells (LSECs) to NP-Ag-induced tolerance in a mouse model of multiple sclerosis, experimental autoimmune encephalomyelitis (EAE). Intravenously delivered Ag-conjugated poly(lactide-co-glycolide) NPs (PLG-Ag) distributed largely to the liver, where they associated with both KCs and LSECs. This distribution was accompanied by CD4 T cell accumulation, clonal deletion, and PD-L1 expression by KCs and LSECs. Ex vivo co-cultures of PLG-Ag-treated KCs or LSECs with Ag-specific CD4 T cells resulted in PGE2 and IL-10 or PGE2 secretion, respectively. KC depletion and adoptive transfer experiments demonstrated that KCs were sufficient, but not necessary, to mediate PLG-Ag-induced tolerance in EAE. The durability of PLG-Ag-induced tolerance in the absence of KCs may be attributed to the distribution of PLG-Ags to LSECs, which demonstrated similar levels of PD-L1, PGE2, and T cell stimulatory ability. Collectively, these studies provide mechanistic support for the role of liver KCs and LSECs in Ag-specific tolerance for a biomaterial platform that is currently being evaluated in clinical trials.

Masked Delivery of Allergen in Nanoparticles Safely Attenuates Anaphylactic Response in Murine Models of Peanut Allergy.

Food allergy is a growing health concern worldwide. Current allergen-specific immunotherapy (AIT) approaches require frequent dosing over extended periods of time and may induce anaphylaxis due to allergen-effector cell interactions. A critical need remains to develop novel approaches that refine AIT for the treatment of food allergies. Previous studies show that poly(lactide-co-glycolide) (PLG) nanoscale particles (NP) effectively suppress Th1- and Th17-driven immune pathologies. However, their ability to suppress the distinct Th2-polarized immune responses driving food allergy are unknown. Herein, we describe the safety and efficacy of NPs containing encapsulated peanut allergen in desensitizing murine models of peanut allergy. Peanut extract encapsulation allowed for the safe intravenous delivery of allergen relative to non-encapsulated approaches. Application of 2-3 doses, without the need for dose escalation, was sufficient to achieve prophylactic and therapeutic efficacy, which correlated with suppression of Th2-mediated disease and reduced mast cell degranulation. Efficacy was associated with strong reductions in a broad panel of Th1, Th2, and Th17 cytokines. These results demonstrate the ability of PLG NPs to suppress allergen-specific immune responses to induce a more tolerogenic phenotype, conferring protection from intragastric allergen challenge. These promising studies represent a step forward in the development of improved immunotherapies for food allergy.

Comparisons of In Vitro and In Vivo Digestibility Assays for Phosphorus in Feline Diets and Associations with Dietary Nutrient Content.

Phosphorus (P) is an essential nutrient; however, potential health impacts of high dietary levels of added soluble, highly bioavailable P salts especially are a concern. P sources with lower bioavailability are considered safer. Yet, speciation of different P sources to assess diets' risk to health is challenging. This investigation tested the value of in vitro water extraction and digestion assays to predict in vivo P apparent bioavailability/digestibility in feline diets. Thirty wet (n = 18) and dry (n = 12) format experimental and commercial cat foods were analyzed for nutrient content. Triplicate samples were subjected to in vitro water extraction, single-phase acidic (gastric; G) digestion, and dual-phase gastric and small intestinal (G-SI) digestion assays. Soluble and insoluble P were determined in the supernatant and pellet, respectively. A subset of the diets (seven wet, nine dry diets) was fed to healthy, adult cats (n = 7-24) to determine in vivo apparent P digestibility. Information on the soluble P salt sources and their contribution to total dietary P was available for some diets. Associations between data from the different in vitro assays and in vivo digestibility trials and the influence of different diet parameters were obtained using Pearson correlation and linear regression modeling. The % soluble P obtained from G-SI digestion assay correlated well with in vivo apparent P digestibility for wet (Pearson coefficient 0.926, p = 0.003), but not for dry diets (Pearson coefficient -0.074, p = 0.849). In contrast, the % soluble P determined by water extraction correlated well with the % soluble P salt contribution to total P for dry (Pearson coefficient 0.901, p < 0.001), but not for wet diets (Pearson coefficient -0.407, p = 0.365). Thus, 20 min water extraction can be used to predict soluble P salt content in dry diets; however, differing Ca:P ratios and water solubility of the P sources may affect the outcome and false-positive results can occur. The G-SI digestion assay employed can also be used to predict in vivo P digestibility. However, again, diet format, Ca:P ratios in diets, and possibly other factors can impact the results. Thus, data from in vitro assays to assess P sources and bioavailability need to be interpreted with care.

Cargo-free immunomodulatory nanoparticles combined with anti-PD-1 antibody for treating metastatic breast cancer.

The presence of immunosuppressive innate immune cells such as myeloid derived suppressor cells (MDSCs), Ly6C-high monocytes, and tumor-associated macrophages (TAMs) at a tumor can inhibit effector T cell and NK cell function. Immune checkpoint blockade using anti-PD-1 antibody aims to overcome the immune suppressive environment, yet only a fraction of patients responds. Herein, we test the hypothesis that cargo-free PLG nanoparticles administered intravenously can divert circulating immune cells from the tumor microenvironment to enhance the efficacy of anti-PD-1 immunotherapy in the 4T1 mouse model of metastatic triple-negative breast cancer. In vitro studies demonstrate that these nanoparticles decrease the expression of MCP-1 by 5-fold and increase the expression of TNF-α by more than 2-fold upon uptake by innate immune cells. Intravenous administration of particles results in internalization by MDSCs and monocytes, with particles detected in the liver, lung, spleen, and primary tumor. Nanoparticle delivery decreased the abundance of MDSCs in circulation and in the lung, the latter being the primary metastatic site. Combined with anti-PD-1 antibody, nanoparticles significantly slowed tumor growth and resulted in a survival benefit. Gene expression analysis by GSEA indicated inflammatory myeloid cell pathways were downregulated in the lung and upregulated in the spleen and tumor. Upregulation of extrinsic apoptotic pathways was also observed in the primary tumor. Collectively, these results demonstrate that cargo-free PLG nanoparticles can reprogram immune cell responses and alter the tumor microenvironment in vivo to overcome the local immune suppression attributed to myeloid cells and enhance the efficacy of anti-PD-1 therapy.

Slow cycling intestinal stem cell and Paneth cell responses to Trichinella spiralis infection.

There is limited information regarding responses by slow cycling stem cells during T. spiralis-induced T-cell mediated intestinal inflammation and how such responses may relate to those of Paneth cells. Transgenic mice, in which doxycycline induces expression of histone 2B (H2B)-green fluorescent protein (GFP), were used. Following discontinuation of doxycycline ("chase" period), retention of H2B-GFP enabled the identification of slow cycling stem cells and long-lived Paneth cells. Inflammation in the small intestine (SI) was induced by oral administration of T. spiralis muscle larvae. Epithelial retention of H2B-GFP per crypt cell position (cp) was studied following immunohistochemistry and using the Score and Wincrypts program. Compared to non-infected controls, there was significant reduction in the number of H2B-GFP-retaining stem cells in T. spiralis-infected small intestines. H2B-GFP-retaining stem cells peaked at around cp 4 in control sections, but smaller peaks at higher cell positions (>10) were seen in sections of inflamed small intestines. In the latter, there was a significant increase in the total number of Paneth cells, with significant reduction in H2B-GFP-retaining Paneth cells, but a marked increase in unlabelled (H2B-GFP-negative) Paneth cells. In conclusion, following T. spiralis-infection, putative slow cycling stem cell numbers were reduced. A marked increase in newly generated Paneth cells at the crypt base led to higher cell positions of the remaining slow cycling stem cells.

Engineered immunological niches to monitor disease activity and treatment efficacy in relapsing multiple sclerosis.

Relapses in multiple sclerosis can result in irreversible nervous system tissue injury. If these events could be detected early, targeted immunotherapy could potentially slow disease progression. We describe the use of engineered biomaterial-based immunological niches amenable to biopsy to provide insights into the phenotype of innate immune cells that control disease activity in a mouse model of multiple sclerosis. Differential gene expression in cells from these niches allow monitoring of disease dynamics and gauging the effectiveness of treatment. A proactive treatment regimen, given in response to signal within the niche but before symptoms appeared, substantially reduced disease. This technology offers a new approach to monitor organ-specific autoimmunity, and represents a platform to analyze immune dysfunction within otherwise inaccessible target tissues.

High-throughput glycomic analyses reveal unique oligosaccharide profiles of canine and feline milk samples.

Oligosaccharides are important components of milk, serving as substrates for the intestinal microbiota, acting as antimicrobials that prevent pathogen colonization, and supporting the developing gastrointestinal immune system of neonates. Nutrient composition of canine and feline milk samples has been described previously, but little is known about the oligosaccharide content. Therefore, the objective of this study was to characterize canine and feline milk samples using a high-throughput glycomics approach. 23 dogs (9 Labrador retriever and 14 Labrador retriever x golden retriever crossbreed) and 6 domestic shorthair cats were recruited to the study. Milk samples were collected by manual expression at time points after parturition. Samples were collected across 2 phases per species, differentiated by maternal diet. Following extraction, oligosaccharide content was determined by liquid chromatography-mass spectrometry (LC-MS). In canine milk samples, 3 structures accounted for over 90% of all oligosaccharides detected across two diet groups. These were 3'-sialyllactose, 6'-sialyllactose, and 2'-fucosyllactose. In feline samples, a more diverse range of oligosaccharides was detected, with up to 16 structures present at relative abundance >1% of the total. Difucosyllactose-N-hexaose b, 3'-sialyllactose and lacto-N-neohexaose were all detected at abundances >10% in feline milk samples. Statistically significant differences (p<0.05) in oligosaccharide abundances were observed between collection time points and between diet groups within species. These data explore the oligosaccharide content of canine and feline maternal milk, representing an opportunity to generate a fundamental understanding of the nutritional needs of new-born puppies and kittens.

Optimizing PLG nanoparticle-peptide delivery platforms for transplantation tolerance using an allogeneic skin transplant model.

A robust regimen for inducing allogeneic transplantation tolerance involves pre-emptive recipient treatment with donor splenocytes (SP) rendered apoptotic by 1-ethyl-3-(3'-dimethylaminopropyl)-carbodiimide(ECDI) treatment. However, such a regimen is limited by availability of donor cells, cost of cell procurement, and regulatory hurdles associated with cell-based therapies. Nanoparticles (NP) delivering donor antigens are a promising alternative for promoting transplantation tolerance. Here, we used a B6.C-H-2bm12(bm12) to C57BL/6(B6) skin transplant model involving a defined major histocompatibility antigen mismatch to investigate design parameters of poly(lactide-co-glycolide) (PLG) NPs delivering peptides containing the donor antigen for optimizing skin allograft survival. We showed that an epitope-containing short peptide (P1) was more effective than a longer peptide (P2) at providing graft protection. Importantly, the NP and P1 complex (NP-ECDI-P1) resulted in a significant expansion of graft-infiltrating Tregs. Interestingly, in comparison to donor ECDI-SP that provided indefinite graft protection, NP-ECDI-P1 targeted different splenic phagocytes and skin allografts in these recipients harbored significantly more graft-infiltrating CD8+IFN-γ+ cells. Collectively, the current study provides initial engineering parameters for a cell-free and biocompatible NP-peptide platform for transplant immunoregulation. Moreover, it also provides guidance to future NP engineering endeavors to recapitulate the effects of donor ECDI-SP as a goal for maximizing tolerance efficacy of NP formulations.

Localized immune tolerance from FasL-functionalized PLG scaffolds.

Intraportal allogeneic islet transplantation has been demonstrated as a potential therapy for type 1 diabetes (T1D). The placement of islets into the liver and chronic immunosuppression to control rejection are two major limitations of islet transplantation. We hypothesize that localized immunomodulation with a novel form of FasL chimeric with streptavidin, SA-FasL, can provide protection and long-term function of islets at an extrahepatic site in the absence of chronic immunosuppression. Allogeneic islets modified with biotin and engineered to transiently display SA-FasL on their surface showed sustained survival following transplantation on microporous scaffolds into the peritoneal fat in combination with a short course (15 days) of rapamycin treatment. The challenges with modifying islets for clinical translation motivated the modification of scaffolds with SA-FasL as an off-the-shelf product. Poly (lactide-co-glycolide) (PLG) was conjugated with biotin and fabricated into particles and subsequently formed into microporous scaffolds to allow for rapid and efficient conjugation with SA-FasL. Biotinylated particles and scaffolds efficiently bound SA-FasL and induced apoptosis in cells expressing Fas receptor (FasR). Scaffolds functionalized with SA-FasL were subsequently seeded with allogeneic islets and transplanted into the peritoneal fat under the short-course of rapamycin treatment. Scaffolds modified with SA-FasL had robust engraftment of the transplanted islets that restored normoglycemia for 200 days. Transplantation without rapamycin or without SA-FasL did not support long-term survival and function. This work demonstrates that scaffolds functionalized with SA-FasL support allogeneic islet engraftment and long-term survival and function in an extrahepatic site in the absence of chronic immunosuppression with significant potential for clinical translation.

Determination of Histone 2B-Green Fluorescent Protein (GFP) Retention in Intestinal Stem Cells.

The epithelium of the gastrointestinal tract represents the interface between the luminal contents of the gut and that of the host tissues and plays a central role not only in regulating absorption of dietary nutrients but also in providing a barrier to prevent the entry of bacteria and other pathogens. Repair and replacement of damaged aging cells within the epithelium is modulated by stem cells, which are located in the intestinal crypts of the small intestine.Two distinct populations of intestinal stem cells have been described in the literature, one population at the very base of the crypt and a second population of long-lived stem cells located just above the Paneth cell zone. Herein, we describe a method to label this population of long-lived GFP label retaining cells. This method is free from confounding factors of previous methodologies based on radioactive tracers and also enables functional studies not previously possible using the radioactive tracer techniques described in the literature.

In vivo reprogramming of immune cells: Technologies for induction of antigen-specific tolerance.

Technologies that induce antigen-specific immune tolerance by mimicking naturally occurring mechanisms have the potential to revolutionize the treatment of many immune-mediated pathologies such as autoimmunity, allograft rejection, and allergy. The immune system intrinsically has central and peripheral tolerance pathways for eliminating or modulating antigen-specific responses, which are being exploited through emerging technologies. Antigen-specific tolerogenic responses have been achieved through the functional reprogramming of antigen-presenting cells or lymphocytes. Alternatively, immune privileged sites have been mimicked using biomaterial scaffolds to locally suppress immune responses and promote long-term allograft survival. This review describes natural mechanisms of peripheral tolerance induction and the various technologies being developed to achieve antigen-specific immune tolerance in vivo. As currently approved therapies are non-specific and carry significant associated risks, these therapies offer significant progress towards replacing systemic immune suppression with antigen-specific therapies to curb aberrant immune responses.