Memory T Cell Migration

Streptococcal Arginine Deiminase Inhibits T Lymphocyte Differentiation In Vitro

Pathogenic microbes use arginine-metabolizing enzymes as an immune evasion strategy. In this study, the impact of streptococcal arginine deiminase (ADI) on the human peripheral blood T lymphocytes function in vitro was studied. The comparison of the effects of parental strain (Streptococcus pyogenes M49-16) with wild type of ArcA gene and its isogenic mutant with inactivated ArcA gene (Streptococcus pyogenes M49-16delArcA) was carried out. It was found that ADI in parental strain SDSC composition resulted in a fivefold decrease in the arginine concentration in human peripheral blood mononuclear cell (PBMC) supernatants. Only parental strain SDSCs suppressed anti-CD2/CD3/CD28-bead-stimulated mitochondrial dehydrogenase activity and caused a twofold decrease in IL-2 production in PBMC. Flow cytometry analysis revealed that ADI decreased the percentage of CM (central memory) and increased the proportion of TEMRA (terminally differentiated effector memory) of CD4+ and CD8+ T cells subsets. Enzyme activity inhibited the proliferation of all CD8+ T cell subsets as well as CM, EM (effector memory), and TEMRA CD4+ T cells. One of the prominent ADI effects was the inhibition of autophagy processes in CD8+ CM and EM as well as CD4+ CM, EM, and TEMRA T cell subsets. The data obtained confirm arginine's crucial role in controlling immune reactions and suggest that streptococcal ADI may downregulate adaptive immunity and immunological memory.

CRISPR/Cas9: A Powerful Strategy to Improve CAR-T Cell Persistence

As an emerging treatment strategy for malignant tumors, chimeric antigen receptor T (CAR-T) cell therapy has been widely used in clinical practice, and its efficacy has been markedly improved in the past decade. However, the clinical effect of CAR-T therapy is not so satisfying, especially in solid tumors. Even in hematologic malignancies, a proportion of patients eventually relapse after receiving CAR-T cell infusions, owing to the poor expansion and persistence of CAR-T cells. Recently, CRISPR/Cas9 technology has provided an effective approach to promoting the proliferation and persistence of CAR-T cells in the body. This technology has been utilized in CAR-T cells to generate a memory phenotype, reduce exhaustion, and screen new targets to improve the anti-tumor potential. In this review, we aim to describe the major causes limiting the persistence of CAR-T cells in patients and discuss the application of CRISPR/Cas9 in promoting CAR-T cell persistence and its anti-tumor function. Finally, we investigate clinical trials for CRISPR/Cas9-engineered CAR-T cells for the treatment of cancer.

Reduction of CD8 T cell functionality but not inhibitory capacity by integrase inhibitors

Although HIV-specific CD8 T cells are effective in controlling HIV-infection, they fail to clear infection even in the presence of antiretroviral therapy (ART) and cure strategies such as "shock-and-kill". Little is known how ART is contributing to HIV-specific CD8 T cell function and the ability to clear HIV infection. Therefore, we first assessed the cytokine polyfunctionality and proliferation of CD8 T cells from ART-treated HIV+ individuals directly ex vivo and observed a decline in the multifunctional response as well as proliferation indices of these cells in individuals treated with integrase inhibitor (INSTI) based ART regimens compared to both protease inhibitor (PI) and non-nucleoside reverse-transcriptase inhibitor (NNRTI) based regimens. We next co-cultured CD8 T cells with different drugs individually and were able to observe reduced functional properties with significantly decreased ability of CD8 T cells to express IFNγ, MIP1β and TNFα only after treatment with INSTI-based regimens. Furthermore, previously activated and INSTI-treated CD8 T cells demonstrated reduced capacity to express perforin and granzyme B compared to PI and NNRTI treated cells. Unexpectedly, CD8 T cells treated with dolutegravir showed a similar killing ability 7 dpi compared to emtricitabine or rilpivirine treated cells. We next used a live cell imaging assay to determine the migratory capacity of CD8 T cells. Only INSTI-treated cells showed less migratory activity after SDF-1α stimulation compared to NRTI regimens. Our data show that the choice of ART can have a significant impact on CD8 T cell effector functions, but the importance for potential eradication attempts is unknown. Importance Integrase Strand Transfer Inhibitors (INSTI) are recommended by national and international guidelines as a key component of ART in the treatment of HIV-infected patients. In particular, their efficacy, tolerability and low drug-drug interaction profile have made them to the preferred choice as part of the first-line regimen in treatment-naïve individuals. Here, we demonstrate that the choice of ART can have a significant impact on function and metabolism of CD8 T cells. In summary, our study provides first evidence on a significant, negative impact on CD8 T cell effector functions in the presence of two INSTIs, dolutegravir and elvitegravir, which may contribute to the limited success of eradicating HIV-infected cells through "shock-and-kill" strategies. Although our findings are coherent with recent studies highlighting a possible role of dolutegravir in weight gain, further investigations are necessary to fully understand the impact of INSTI-based regimens on the health of the individual during antiretroviral therapy.

Neural-Cadherin Influences the Homing of Terminally Differentiated Memory CD8 T Cells to the Lymph Nodes and Bone Marrow

Memory T (TM) cells play an important role in the long-term defense against pathogen reinvasion. However, it is still unclear how these cells receive the crucial signals necessary for their longevity and homeostatic turnover. To understand how TM cells receive these signals, we infected mice with lymphocytic choriomeningitis virus (LCMV) and examined the expression sites of neural cadherin (N-cadherin) by immunofluorescence microscopy. We found that N-cadherin was expressed in the surroundings of the white pulps of the spleen and medulla of lymph nodes (LNs). Moreover, TM cells expressing high levels of killer cell lectin-like receptor G1 (KLRG1), a ligand of N-cadherin, were co-localized with N-cadherin+ cells in the spleen but not in LNs. We then blocked N-cadherin in vivo to investigate whether it regulates the formation or function of TM cells. The numbers of CD127hiCD62Lhi TM cells in the spleen of memory P14 chimeric mice declined when N-cadherin was blocked during the contraction phase, without functional impairment of these cells. In addition, when CD127loKLRG1hi TM cells were adoptively transferred into anti-N-cadherin-treated mice compared with control mice, the number of these cells was reduced in the bone marrow and LNs, without functional loss. Taken together, our results suggest that N-cadherin participates in the development of CD127hiCD62Lhi TM cells and homing of CD127loKLRG1hi TM cells to lymphoid organs.

CXCR6 by increasing retention of memory CD8+ T cells in the ovarian tumor microenvironment promotes immunosurveillance and control of ovarian cancer

Purpose

Resident memory CD8 T cells, owing to their ability to reside and persist in peripheral tissues, impart adaptive sentinel activity and amplify local immune response, and have beneficial implications for tumor surveillance and control. The current study aimed to clarify the less known chemotactic mechanisms that govern the localization, retention, and residency of memory CD8 T cells in the ovarian tumor microenvironment.

Experimental design

RNA and protein expressions of chemokine receptors in CD8⁺ resident memory T cells in human ovarian tumor-infiltrating CD8⁺ T cells and their association with survival were analyzed. The role of CXCR6 on antitumor T cells was investigated using prophylactic vaccine models in murine ovarian cancer.

Results

Chemokine receptor profiling of CD8⁺CD103⁺ resident memory tumor-infiltrating lymphocytes in patients with ovarian cancer revealed high expression of CXCR6. Analysis of The Cancer Genome Atlas (TCGA) (ovarian cancer database revealed CXCR6 to be associated with CD103 and increased patient survival. Functional studies in mouse models of ovarian cancer revealed that CXCR6 is a marker of resident, but not circulatory, tumor-specific memory CD8⁺ T cells. CXCR6-deficient tumor-specific CD8⁺ T cells showed reduced retention in tumor tissues, leading to diminished resident memory responses and poor control of ovarian cancer.

Conclusions

CXCR6, by promoting retention in tumor tissues, serves a critical role in resident memory T cell-mediated immunosurveillance and control of ovarian cancer. Future studies warrant exploiting CXCR6 to promote resident memory responses in cancers.

PI3K in T Cell Adhesion and Trafficking

PI3K signalling is required for activation, differentiation, and trafficking of T cells. PI3Kδ, the dominant PI3K isoform in T cells, has been extensively characterised using PI3Kδ mutant mouse models and PI3K inhibitors. Furthermore, characterisation of patients with Activated PI3K Delta Syndrome (APDS) and mouse models with hyperactive PI3Kδ have shed light on how increased PI3Kδ activity affects T cell functions. An important function of PI3Kδ is that it acts downstream of TCR stimulation to activate the major T cell integrin, LFA-1, which controls transendothelial migration of T cells as well as their interaction with antigen-presenting cells. PI3Kδ also suppresses the cell surface expression of CD62L and CCR7 which controls the migration of T cells across high endothelial venules in the lymph nodes and S1PR1 which controls lymph node egress. Therefore, PI3Kδ can control both entry and exit of T cells from lymph nodes as well as the recruitment to and retention of T cells within inflamed tissues. This review will focus on the regulation of adhesion receptors by PI3Kδ and how this contributes to T cell trafficking and localisation. These findings are relevant for our understanding of how PI3Kδ inhibitors may affect T cell redistribution and function.

Suppression of the Immune Response by Syngeneic Splenocytes Adoptively Transferred to Sublethally Irradiated Mice

The peripheral T-cell pool consists of several, functionally distinct populations of CD8⁺ T cells. CD44 and CD62L are among the major surface markers that allow us to define T-cell populations. The expression of these molecules depends on the functional status of a T lymphocyte. Under lymphopenic conditions, peripheral T cells undergo homeostatic proliferation and acquire the memory-like surface phenotype CD44hiCD62Lhi. However, the data on the functional activity of these cells remains controversial. In this paper, we analyzed the effects of the adoptive transfer of syngeneic splenocytes on the recovery of CD8⁺ T cells in sublethally irradiated mice. Our data demonstrate that under lymphopenia, donor lymphocytes form a population of memory-like CD8⁺ T cells with the phenotype CD122+CD5+CD49dhiCXCR3+ that shares the phenotypic characteristics of true memory cells and suppressive CD8⁺ T cells. Ex vivo experiments showed that after adoptive transfer in irradiated mice, T cells lacked the functions of true effector or memory cells; the allogeneic immune response and immune response to pathogens were greatly suppressed in these mice.

Allogeneic ADSCs Induce the Production of Alloreactive Memory-CD8 T Cells through HLA-ABC Antigens

We investigated the immunogenicity of allogeneic human adipose-derived mesenchymal stem cells (ADSCs) through the production of alloreactive-CD8 T and -memory CD8 T cells, based on their human leukocyte antigen (HLA) expression. In surface antigen analysis, ADSCs do not express co-stimulatory molecules, but expresses HLA-ABC, which is further increased by exposure to the pro-inflammatory cytokines as well as IFN-γ alone. For immunogenicity analysis, allogeneic ADSCs cultured in xenofree medium (XF-ADSCs) were incubated with the recipient immune cells for allogeneic-antigen stimulation. As a result, XF-ADSCs induced IFN-γ and IL-17A release by alloreactive-CD8 T cells and the production of alloreactive-CD8 T cell through a direct pathway, although they have immunomodulatory activity. In the analysis of alloreactive memory CD8 T cells, XF-ADSCs also significantly induced the production of CFSE-low-CD8 TEM and -CD8 TCM cells. However, HLA-blocking antibodies significantly inhibited the production of CFSE-low memory-CD8 T cells, indicating that HLAs are the main antigens responsible for the development of allogeneic ADSCs' immunogenicity. These results suggested that HLA surface antigens expressed in allogeneic MSCs should be solved in order to address concerns related to the immunogenicity problem.

'Off-the-shelf' allogeneic CAR T cells: development and challenges

Autologous chimeric antigen receptor (CAR) T cells have changed the therapeutic landscape in haematological malignancies. Nevertheless, the use of allogeneic CAR T cells from donors has many potential advantages over autologous approaches, such as the immediate availability of cryopreserved batches for patient treatment, possible standardization of the CAR-T cell product, time for multiple cell modifications, redosing or combination of CAR T cells directed against different targets, and decreased cost using an industrialized process. However, allogeneic CAR T cells may cause life-threatening graft-versus-host disease and may be rapidly eliminated by the host immune system. The development of next-generation allogeneic CAR T cells to address these issues is an active area of research. In this Review, we analyse the different sources of T cells for optimal allogeneic CAR-T cell therapy and describe the different technological approaches, mainly based on gene editing, to produce allogeneic CAR T cells with limited potential for graft-versus-host disease. These improved allogeneic CAR-T cell products will pave the way for further breakthroughs in the treatment of cancer.

Potential roles of the CCL17-CCR4 axis in immunopathogenesis of oral lichen planus

BACKGROUND

Oral lichen planus (OLP) is a T cell-mediated chronic inflammatory disease. C-C chemokine receptor type 4 (CCR4) and its cognate C-C motif chemokine ligand 17 (CCL17) play a key role in T-cell activation and trafficking, but their implication in OLP pathogenesis has not been explored. Our study was designed to analyze the expression and function of the CCL17-CCR4 axis in OLP.

METHODS

The mRNA expression levels of CCL17 and CCR4 in the circulating T cells of OLP subjects were examined by quantitative real-time PCR. The protein levels of CCL17 and CCR4 in the peripheral blood of OLP subjects were detected by enzyme-linked immunosorbent assay (ELISA) and Simple Western assay, respectively. The functional relevance of increased expression of CCL17 and CCR4 in OLP was demonstrated in proliferation, apoptosis, and migration assays.

RESULTS

The mRNA and protein expression levels of CCL17 and CCR4 in the peripheral blood of patients with OLP were significantly upregulated compared with those of controls. CCL17 induced the migration of OLP T cells. In addition, blocking CCR4 with a small molecule CCR4 antagonist not only inhibited the proliferation and migration of OLP T cells but also promoted the apoptosis of OLP T cells.

CONCLUSION

Our findings indicate that the CCL17-CCR4 axis might be responsible for the inflammatory infiltration of T cells in OLP.

Immunological memory cells

This article reviews immunological memory cells, currently represented by T and B lymphocytes and natural killer (NK) cells, which determine a rapid and effective response against a second encounter with the same antigen. Among T lymphocytes, functions of memory cells are provided by their subsets: central memory, effector memory, tissue-resident memory, regulatory memory and stem memory T cells. Memory T and B lymphocytes have an essential role in the immunity against microbial pathogens but are also involved in autoimmunity and maternal-fetal tolerance. Furthermore, the evidence of immunological memory has been established for NK cells. NK cells can respond to haptens or viruses, which results in generation of antigen-specific memory cells. T, B and NK cells, which have a role in immunological memory, have been characterized phenotypically and functionally. During the secondary immune response, these cells are involved in the reaction against foreign antigens, including pathogens, and take part in autoimmune diseases, but also are crucial to immunological tolerance and vaccine therapy.

Selective Targeting of High-Affinity LFA-1 Does Not Augment Costimulation Blockade in a Nonhuman Primate Renal Transplantation Model

Costimulation blockade (CoB) via belatacept is a lower-morbidity alternative to calcineurin inhibitor (CNI)-based immunosuppression. However, it has higher rates of early acute rejection. These early rejections are mediated in part by memory T cells, which have reduced dependence on the pathway targeted by belatacept and increased adhesion molecule expression. One such molecule is leukocyte function antigen (LFA)-1. LFA-1 exists in two forms: a commonly expressed, low-affinity form and a transient, high-affinity form, expressed only during activation. We have shown that antibodies reactive with LFA-1 regardless of its configuration are effective in eliminating memory T cells but at the cost of impaired protective immunity. Here we test two novel agents, leukotoxin A and AL-579, each of which targets the high-affinity form of LFA-1, to determine whether this more precise targeting prevents belatacept-resistant rejection. Despite evidence of ex vivo and in vivo ligand-specific activity, neither agent when combined with belatacept proved superior to belatacept monotherapy. Leukotoxin A approached a ceiling of toxicity before efficacy, while AL-579 failed to significantly alter the peripheral immune response. These data, and prior studies, suggest that LFA-1 blockade may not be a suitable adjuvant agent for CoB-resistant rejection.

Chitosan gel vaccine protects against tumour growth in an intracaecal mouse model of cancer by modulating systemic immune responses

Background

Vaccination generating a robust memory population of CD8⁺ T cells may provide protection against cancer. However, immune therapies for cancer are influenced by the local tumour immune microenvironment. An infiltrate of T cells into tumours of people with colorectal cancer has proven to be a significant indicator of good prognosis.

Methods

We used an intracaecal mouse model of cancer to determine whether a protective immune response against a mucosal gut tumour could be generated using a systemic intervention. We investigated the generation of murine memory CD8⁺ T cells using a sustained antigen release vaccine vehicle (chitosan gel; Gel + OVA) containing the model antigen ovalbumin, chitosan gel alone (Gel) or conventional dendritic cell vaccination (DC + OVA) using the same protein antigen.

Results

Following vaccination with Gel + OVA, CD8⁺ T cell memory populations specific for ovalbumin protein were detected. Only vaccination with Gel + OVA gave decreased tumour burden compared to unvaccinated or DC + OVA-vaccinated mice in the intracaecal cancer challenge model.

Conclusion

These results indicate that subcutaneous vaccination with Gel + OVA generates a population of functional CD8⁺ memory T cells in lymphoid tissue able to protect against intracaecal tumour challenge. Vaccination with chitosan gel may be valuable in anti-cancer treatment at both peripheral and mucosal sites.

Electronic supplementary material

The online version of this article (doi:10.1186/s12865-016-0178-4) contains supplementary material, which is available to authorized users.

Long-term production of BDNF and NT-3 induced by A91-immunization after spinal cord injury

BACKGROUND

After spinal cord (SC)-injury, a non-modulated immune response contributes to the damage of neural tissue. Protective autoimmunity (PA) is a T cell mediated, neuroprotective response induced after SC-injury. Immunization with neural-derived peptides (INDP), such as A91, has shown to promote-in vitro-the production of neurotrophic factors. However, the production of these molecules has not been studied at the site of injury.

RESULTS

In order to evaluate these issues, we performed four experiments in adult female Sprague-Dawley rats. In the first one, brain derived neurotrophic factor (BDNF) and neurotrophin-3 (NT-3) concentrations were evaluated at the site of lesion 21 days after SC-injury. BDNF and NT-3 were significantly increased in INDP-treated animals. In the second experiment, proliferation of anti-A91 T cells was assessed at chronic stages of injury. In this case, we found a significant proliferation of these cells in animals subjected to SC-injury + INDP. In the third experiment, we explored the amount of BDNF and NT3 at the site of injury in the chronic phase of rats subjected to either SC-contusion (SCC; moderate or severe) or SC-transection (SCT; complete or incomplete). The animals were treated with INDP immediately after injury. Rats subjected to moderate contusion or incomplete SCT showed significantly higher levels of BDNF and NT-3 as compared to PBS-immunized ones. In rats with severe SCC and complete SCT, BDNF and NT-3 concentrations were barely detected. Finally, in the fourth experiment we assessed motor function recovery in INDP-treated rats with moderate SC-injury. Rats immunized with A91 showed a significantly higher motor recovery from the first week and up to 4 months after SC-injury.

CONCLUSIONS

The results of this study suggest that PA boosted by immunization with A91 after moderate SC-injury can exert its benefits even at chronic stages, as shown by long-term production of BDNF and NT-3 and a substantial improvement in motor recovery.