In Vitro and Ex Vivo Methodologies for T-Cell Trafficking Through Blood-Brain Barrier After TLR Activation

This chapter describes ex vivo isolation of human T cells and of naïve splenocytes respectively collected from multiple sclerosis patients and healthy controls and experimental autoimmune encephalomyelitis-affected mice. After the magnetic sorting of naïve and activated T helper lymphocytes, we provide details about the cell cultures to measure the interaction with extracellular matrix proteins using standard cell invasion or hand-made in vitro assays, upon different stimuli, through Toll-like receptor(s) ligands, T-cell activators, and cell adhesion molecules modulators. Finally, we describe the methods to harvest and recover T cells to evaluate the properties associated with their trafficking ability.

GVHD Prophylaxis 2020

Graft-vs. host disease (GVHD), both acute and chronic are among the chief non-relapse complications of allogeneic transplantation which still cause substantial morbidity and mortality despite significant advances in supportive care over the last few decades. The prevention of GVHD therefore remains critical to the success of allogeneic transplantation. In this review we briefly discuss the pathophysiology and immunobiology of GVHD and the current standards in the field which remain centered around calcineurin inhibitors. We then discuss important translational advances in GVHD prophylaxis, approaching these various platforms from a mechanistic standpoint based on the pathophysiology of GVHD including in-vivo and ex-vivo T-cell depletion alongwith methods of selective T-cell depletion, modulation of T-cell co-stimulatory pathways (checkpoints), enhancing regulatory T-cells (Tregs), targeting T-cell trafficking as well as cytokine pathways. Finally we highlight exciting novel pre-clinical research that has the potential to translate to the clinic successfully. We approach these methods from a pathophysiology based perspective as well and touch upon strategies targeting the interaction between tissue damage induced antigens and T-cells, regimen related endothelial toxicity, T-cell co-stimulatory pathways and other T-cell modulatory approaches, T-cell trafficking, and cytokine pathways. We end this review with a critical discussion of existing data and novel therapies that may be transformative in the field in the near future as a comprehensive picture of GVHD prophylaxis in 2020. While calcineurin inhibitors remain the standard, post-transplant eparinsphamide originally developed to facilitate haploidentical transplantation is becoming an attractive alternative to traditional calcinuerin inhibitor based prophylaxis due to its ability to reduce severe forms of acute and chronic GVHD without compromising other outcomes, even in the HLA-matched setting. In addition T-cell modulation, particularly targeting some important T-cell co-stimulatory pathways have resulted in promising outcomes and may be a part of GVHD prophylaxis in the future. Novel approaches including targeting early events in GVHD pathogenesis such as interactions bvetween tissue damage associated antigens and T-cells, endothelial toxicity, and T-cell trafficking are also promising and discussed in this review. GVHD prophylaxis in 2020 continues to evolve with novel exicitng therapies on the horizon based on a more sophisticated understanding of the immunobiology of GVHD.

Hyaluronan synthesis is necessary for autoreactive T-cell trafficking, activation, and Th1 polarization

The extracellular matrix polysaccharide hyaluronan (HA) accumulates at sites of autoimmune inflammation, including white matter lesions in multiple sclerosis (MS), but its functional importance in pathogenesis is unclear. We have evaluated the impact of 4-methylumbelliferone (4-MU), an oral inhibitor of HA synthesis, on disease progression in the experimental autoimmune encephalomyelitis (EAE) mouse model of MS. Treatment with 4-MU decreases the incidence of EAE, delays its onset, and reduces the severity of established disease. 4-MU inhibits the activation of autoreactive T cells and prevents their polarization toward a Th1 phenotype. Instead, 4-MU promotes polarization toward a Th2 phenotpye and induction of Foxp3(+) regulatory T cells. Further, 4-MU hastens trafficking of T cells through secondary lymphoid organs, impairs the infiltration of T cells into the CNS parenchyma, and limits astrogliosis. Together, these data suggest that HA synthesis is necessary for disease progression in EAE and that treatment with 4-MU may be a potential therapeutic strategy in CNS autoimmunity. Considering that 4-MU is already a therapeutic, called hymecromone, that is approved to treat biliary spasm in humans, we propose that it could be repurposed to treat MS.

Control of CD8 T-Cell Infiltration into Tumors by Vasculature and Microenvironment

CD8 T-cells are a critical brake on the initial development of tumors. In established tumors, the presence of CD8 T-cells is correlated with a positive patient prognosis, although immunosuppressive mechanisms limit their effectiveness and they are rarely curative without manipulation. Cancer immunotherapies aim to shift the balance back to dominant antitumor immunity through antibody blockade of immunosuppressive signaling pathways, vaccination, and adoptive transfer of activated or engineered T-cells. These approaches have yielded striking responses in small subsets of patients with solid tumors, most notably those with melanoma. Importantly, the subset of patients who respond to vaccination or immunosuppression blockade therapies are those with CD8 T-cells present in the tumor prior to initiating therapy. While current adoptive cell therapy approaches can be dramatically effective, they require infusion of extremely large numbers of T-cells, but the number that actually infiltrates the tumor is very small. Thus, poor representation of CD8 T-cells in tumors is a fundamental hurdle to successful immunotherapy, over and above the well-established barrier of immunosuppression. In this review, we discuss the factors that determine whether immune cells are present in tumors, with a focus on the representation of cytotoxic CD8 T-cells. We emphasize the critically important role of tumor-associated vasculature as a gateway that enables the active infiltration of both effector and naïve CD8 T-cells that exert antitumor activity. We also discuss strategies to enhance the gateway function and extend the effectiveness of immunotherapies to a broader set of cancer patients.

Intravital microscopy in BLT-humanized mice to study cellular dynamics in HIV infection

Humanized mouse models have, over the past few years, seen dramatic improvements, including the colonization of both lymphoid and nonlymphoid tissues with all major immune cell lineages, the development of T cells with human major histocompatibility complex restriction, and the ability to mount functional adaptive immune responses to human pathogens, as documented in some instances. This has greatly increased the range of questions related to the biology of human immunodeficiency virus (HIV) infection that can be usefully addressed through experimental approaches utilizing small animal models. Among these approaches is in vivo imaging, and specifically multiphoton intravital microscopy (MP-IVM), which allows for the investigation of dynamic biological processes at cellular and subcellular resolution in the tissues of live animals. We have recently begun to use MP-IVM in lymph nodes of humanized mice in order to examine HIV infectious spread in vivo at the tissue and cellular level. Here, we provide a short perspective on the close link between the patterns of immune cell migration and the mechanisms of viral dissemination, and summarize the results of our initial studies.

Peptide-based anticancer vaccines: The making and unmaking of a T-cell graveyard

Poorly biodegradable, incomplete Freund’s adjuvant (IFA)-based anticancer vaccines primed CD8⁺ T cells that did not localize to the tumor site but to the persisting, antigen-rich vaccination site, which became a T-cell graveyard. Short-lived, water-based formulations and the provision of immunostimulatory molecules overcame this issue, resulting in tumor suppression. Here, we discuss the implications of these findings for the development of therapeutic anticancer vaccines.