CTLA-4 expressing innate lymphoid cells modulate mucosal homeostasis in a microbiota dependent manner.

The maintenance of intestinal homeostasis is a fundamental process critical for organismal integrity. Sitting at the interface of the gut microbiome and mucosal immunity, adaptive and innate lymphoid populations regulate the balance between commensal micro-organisms and pathogens. Checkpoint inhibitors, particularly those targeting the CTLA-4 pathway, disrupt this fine balance and can lead to inflammatory bowel disease and immune checkpoint colitis.

IL-21 shapes germinal center polarization via light zone B cell selection and cyclin D3 upregulation.

Germinal center (GC) dysregulation has been widely reported in the context of autoimmunity. Here, we show that interleukin 21 (IL-21), the archetypal follicular helper T cell (Tfh) cytokine, shapes the scale and polarization of spontaneous chronic autoimmune as well as transient immunization-induced GC. We find that IL-21 receptor deficiency results in smaller GC that are profoundly skewed toward a light zone GC B cell phenotype and that IL-21 plays a key role in selection of light zone GC B cells for entry to the dark zone.

Stratification of PD-1 blockade response in melanoma using pre- and post-treatment immunophenotyping of peripheral blood.

Efficacy of checkpoint inhibitor therapies in cancer varies greatly, with some patients showing complete responses while others do not respond and experience progressive disease. We aimed to identify correlates of response and progression following PD-1-directed therapy by immunophenotyping peripheral blood samples from 20 patients with advanced malignant melanoma before and after treatment with the PD-1 blocking antibody pembrolizumab. Our data reveal that individuals responding to PD-1 blockade were characterised by increased CD8 T cell proliferation following treatment, while progression was associated with an increase in CTLA-4-expressing Treg.

Costimulation blockade in combination with IL-2 permits regulatory T cell sparing immunomodulation that inhibits autoimmunity.

Blockade of CD28 costimulation with CTLA-4-Ig/Abatacept is used to dampen effector T cell responses in autoimmune and transplantation settings. However, a significant drawback of this approach is impaired regulatory T cell homeostasis that requires CD28 signaling. Therefore, strategies that restrict the effects of costimulation blockade to effector T cells would be advantageous.

Direct contact between Plasmodium falciparum and human B-cells in a novel co-culture increases parasite growth and affects B-cell growth.

Background: Plasmodium falciparum parasites cause malaria and co-exist in humans together with B-cells for long periods of time. Immunity is only achieved after repeated exposure. There has been a lack of methods to mimic the in vivo co-occurrence, where cells and parasites can be grown together for many days, and it has been difficult with long time in vitro studies.

Follicular helper T cell profiles predict response to costimulation blockade in type 1 diabetes.

Follicular helper T (T) cells are implicated in type 1 diabetes (T1D), and their development has been linked to CD28 costimulation. We tested whether T cells were decreased by costimulation blockade using the CTLA-4-immunoglobulin (Ig) fusion protein (abatacept) in a mouse model of diabetes and in individuals with new-onset T1D. Unbiased bioinformatics analysis identified that inducible costimulatory molecule (ICOS) T cells and other ICOS populations, including peripheral helper T cells, were highly sensitive to costimulation blockade.

A modified CD34+ hematopoietic stem and progenitor cell isolation strategy from cryopreserved human umbilical cord blood.

Background: Umbilical cord blood (UCB) is a source of hematopoietic stem cells for transplantation, offering an alternative for patients unable to find a matched adult donor. UCB is also a versatile source of hematopoietic stem and progenitor cells (hCD34 + HSPCs) for research into hematologic diseases, in vitro expansion, ex vivo gene therapy, and adoptive immunotherapy. For these studies, there is a need to isolate hCD34 + HSPCs from cryopreserved units, and protocols developed for isolation from fresh cord blood are unsuitable.

CTLA-4-mediated transendocytosis of costimulatory molecules primarily targets migratory dendritic cells.

CTLA-4 is a critical negative regulator of the immune system and a major target for immunotherapy. However, precisely how it functions in vivo to maintain immune homeostasis is not clear. As a highly endocytic molecule, CTLA-4 can capture costimulatory ligands from opposing cells by a process of transendocytosis (TE).

T Cell/B Cell Collaboration and Autoimmunity: An Intimate Relationship.

Co-ordinated interaction between distinct cell types is a hallmark of successful immune function. A striking example of this is the carefully orchestrated cooperation between helper T cells and B cells that occurs during the initiation and fine-tuning of T-cell dependent antibody responses. While these processes have evolved to permit rapid immune defense against infection, it is becoming increasingly clear that such interactions can also underpin the development of autoimmunity.

Mice with Reconstituted Human Immune System Components as a Tool to Study Immune Cell Interactions in EBV Infection.

Recent developments in mouse models that harbor part of a human immune system have proved extremely valuable to study the in vivo immune response to human specific pathogens such as Epstein-Barr virus. Over the last decades, advances in immunodeficient mouse strains that can be used as recipients for human immune cells have greatly enhanced the use of these models. Here, we describe the generation of mice with reconstituted human immune system (HIS mice) using immunocompromised mice transplanted with human CD34 hematopoietic stem cells.

In vivo engineering of mobilized stem cell grafts with the immunomodulatory drug FTY720 for allogeneic transplantation.

The immunological attributes of stem cell grafts play an important role in the outcome of allogeneic stem cell transplants. Currently, ex vivo manipulation techniques such as bulk T-cell depletion or positive selection of CD34(+) cells are utilized to improve the immunological attributes of grafts and minimize the potential for graft-versus-host disease (GvHD). Here, we demonstrate a novel graft engineering technique, which utilizes the immunomodulatory drug FTY720 for in vivo depletion of naïve T (TN ) cells from donor G-CSF-mobilized grafts without ex vivo manipulation.

CTLA-4 controls follicular helper T-cell differentiation by regulating the strength of CD28 engagement.

Cytotoxic T-lymphocyte-associated antigen-4 (CTLA-4) is an essential regulator of T-cell responses, and its absence precipitates lethal T-cell hyperactivity. However, whether CTLA-4 acts simply to veto the activation of certain clones or plays a more nuanced role in shaping the quality of T-cell responses is not clear. Here we report that T cells in CTLA-4-deficient mice show spontaneous T-follicular helper (T(FH)) differentiation in vivo, and this is accompanied by the appearance of large germinal centers (GCs).

Follicular helper T cell signature in type 1 diabetes.

The strong genetic association between particular HLA alleles and type 1 diabetes (T1D) indicates a key role for CD4+ T cells in disease; however, the differentiation state of the responsible T cells is unclear. T cell differentiation originally was considered a dichotomy between Th1 and Th2 cells, with Th1 cells deemed culpable for autoimmune islet destruction. Now, multiple additional T cell differentiation fates are recognized with distinct roles.

T cells modulate Epstein-Barr virus latency phenotypes during infection of humanized mice.

Unlabelled: Human B cells, the main target of Epstein-Barr virus (EBV), can display several types of latent viral protein expression, denoted 0, I, IIa, IIb, or III. Of these, only type III expression induces proliferation of cells in vitro. These latency types are present at specific stages of infection and are also characteristic of different tumor types, but their generation is not fully understood.

Evaluation of immunogen delivery by DNA immunization using non-invasive bioluminescence imaging.

The efficacy of DNA vaccines is highly dependent on the methods used for their delivery and the choice of delivery sites/targets for gene injection, pointing at the necessity of a strict control over the gene delivery process. Here, we have investigated the effect of the injection site on gene expression and immunogenicity in BALB/c mice, using as a model a weak gene immunogen, DNA encoding firefly luciferase (Luc) delivered by superficial or deep injection with subsequent electroporation (EP). Immunization was assessed by monitoring the in vivo expression of luciferase by 2D- and 3D-bioluminescence imaging (BLI) and by the end-point immunoassays.

CD4+ cell-dependent granuloma formation in humanized mice infected with mycobacteria.

We have used humanized mice, in which human immune cells differentiate de novo from transplanted cord blood progenitor cells, to study the human immune responses to infection with Mycobacterium bovis bacillus Calmette-Guérin and Mycobacterium tuberculosis. Granulomas with a core containing giant cells, human CD68(+) macrophages, and high bacilli numbers surrounded by a layer of CD3(+) T cells and a fibrotic response encapsulating the lesions were observed in livers and lungs from bacillus Calmette-Guérin-infected humanized mice but not in nonhumanized infected controls. Paradoxically, humanized mice contained higher mycobacterial numbers in organs than nonhumanized controls.

Soluble factors produced by activated CD4+ T cells modulate EBV latency.

Following infection with Epstein-Barr virus (EBV), the virus is carried for life in the memory B-cell compartment in a silent state (latency I/0). These cells do not resemble the proliferating lymphoblastoid cells (LCLs) (latency III) that are generated after infection. It is of fundamental significance to identify how the different EBV expression patterns are established in the latently infected cell.

Expression patterns of NKG2A, KIR, and CD57 define a process of CD56dim NK-cell differentiation uncoupled from NK-cell education.

Natural killer (NK) cells are lymphocytes of the innate immune system that, following differentiation from CD56(bright) to CD56(dim) cells, have been thought to retain fixed functional and phenotypic properties throughout their lifespan. In contrast to this notion, we here show that CD56(dim) NK cells continue to differentiate. During this process, they lose expression of NKG2A, sequentially acquire inhibitory killer cell inhibitory immunoglobulin-like receptors and CD57, change their expression patterns of homing molecules, and display a gradual decline in proliferative capacity.

Use of non-invasive bioluminescent imaging to assess mycobacterial dissemination in mice, treatment with bactericidal drugs and protective immunity.

Monitoring the spread of mycobacterium in vivo using biophotonic imaging provides a fast, reliable and sensitive method to evaluate the distribution of the infection. Moreover, this technique allows for a significant reduction in the number of animals required in comparison to conventional anatomopathological studies. Here, we describe for the first time and validate the use of a luciferase-tagged recombinant Mycobacterium bovis BCG for non-invasive bioluminescent imaging of 1) bacterial dissemination in tissues, 2) the efficacy of treatment with anti-mycobacterial drugs and 3) the role of adaptive immune responses in controlling mycobacterial infection in vivo.

Nonhematopoietic cells control the outcome of infection with Listeria monocytogenes in a nucleotide oligomerization domain 1-dependent manner.

We analyzed the defensive role of the cytosolic innate recognition receptor nucleotide oligomerization domain 1 (NOD1) during infection with Listeria monocytogenes. Mice lacking NOD1 showed increased susceptibility to systemic intraperitoneal and intravenous infection with high or low doses of L. monocytogenes, as measured by the bacterial load and survival.

Coronaviruses as vectors: stability of foreign gene expression.

Coronaviruses are enveloped, positive-stranded RNA viruses considered to be promising vectors for vaccine development, as (i) genes can be deleted, resulting in attenuated viruses; (ii) their tropism can be modified by manipulation of their spike protein; and (iii) heterologous genes can be expressed by simply inserting them with appropriate coronaviral transcription signals into the genome. For any live vector, genetic stability is an essential requirement. However, little is known about the genetic stability of recombinant coronaviruses expressing foreign genes.