The Role of T Cells in Alzheimer's Disease Pathogenesis.

Alzheimer's disease (AD) is a progressive neurodegenerative disorder associated with memory decline and cognitive impairment, which is related to hallmark protein aggregates, amyloid-ß (Аß) plaques and neurofibrillary tangles; the latter are accumulated with hyperphosphorylated Tau protein. Immune cells play an important role in AD pathogenesis. Although the role of T cells in AD remains controversial, studies have shown that T cell deficiency is associated with increased AD pathology. In contrast, transplantation of T cells reduces AD pathology. T cells can help B cells generate anti-Ðß antibody to neutralize the toxin of Ðß and hyperphosphorylated Tau. T cells also activate macrophages to phagocytose misfolded proteins including Ðß and Tau. Recent data have also shown that AD animals have a damaged thymic microenvironment, especially thymic epithelial cells (TECs), resulting in decreased T cell numbers, which contribute to AD pathology. Therefore, regulation of T cell regeneration, for example by rejuvenating the thymic microenvironment, has the potential to be used in the treatment of AD.

Comprehensive phenotypic analysis of diverse FOXN1 variants.

BACKGROUND: Thymus hypoplasia due to stromal cell problems has been linked to mutations in several transcription factors, including Forkhead box N1 (FOXN1). FOXN1 supports T-cell development by regulating the formation and expansion of thymic epithelial cells (TECs). While autosomal recessive FOXN1 mutations result in a nude and severe combined immunodeficiency phenotype, the impact of single-allelic or compound heterozygous FOXN1 mutations is less well-defined. OBJECTIVE: With more than 400 FOXN1 mutations reported, their impact on protein function and thymopoiesis remains unclear for most variants. We developed a systematic approach to delineate the functional impact of diverse FOXN1 variants. METHODS: Selected FOXN1 variants were tested with transcriptional reporter assays and imaging studies. Thymopoiesis was assessed in mouse lines genocopying several human FOXN1 variants. Reaggregate thymus organ cultures were used to compare the thymopoietic potential of the FOXN1 variants. RESULTS: FOXN1 variants were categorized into benign, loss- or gain-of-function, and/or dominant-negatives. Dominant negative activities mapped to frameshift variants impacting the transactivation domain. A nuclear localization signal was mapped within the DNA binding domain. Thymopoiesis analyses with mouse models and reaggregate thymus organ cultures revealed distinct consequences of particular Foxn1 variants on T-cell development. CONCLUSIONS: The potential effect of a FOXN1 variant on T-cell output from the thymus may relate to its effects on transcriptional activity, nuclear localization, and/or dominant negative functions. A combination of functional assays and thymopoiesis comparisons enabled a categorization of diverse FOXN1 variants and their potential impact on T-cell output from the thymus.

Administration of recombinant FOXN1 protein attenuates Alzheimer's pathology in mice.

BACKGROUND: Alzheimer's disease (AD) is the most common cause of dementia in older adults and characterized by progressive loss of memory and cognitive functions that are associated with amyloid-beta (Aß) plaques and neurofibrillary tangles. Immune cells play an important role in the clearance of Aß deposits and neurofibrillary tangles. T cells are the major component of the immune system. The thymus is the primary organ for T cell generation. T cell development in the thymus depends on thymic epithelial cells (TECs). However, TECs undergo both qualitative and quantitative loss over time. We have previously reported that a recombinant (r) protein containing FOXN1 and a protein transduction domain can increase the number of TECs and subsequently increases the number of T cells in mice. In this study we determined the ability of rFOXN1 to affect cognitive performance and AD pathology in mice. METHODS: Aged 3xTg-AD and APP/PS1 AD mice were injected with rFOXN1 or control protein. Cognitive performance, AD pathology, the thymic microenvironment and immune cells were then analyzed. RESULTS: Administration of rFOXN1 into AD mice improves cognitive performance and reduces Aß plaque load and phosphorylated tau in the brain. This is related to rejuvenating the aged thymic microenvironment, which results in enhanced T cell generation in the thymus, leading to increased number of T cells, especially IFNγ-producing T cells, in the spleen and the choroid plexus (CP), enhanced expression of immune cell trafficking molecules in the CP, and increased migration of monocyte-derived macrophages into the brain. Furthermore, the production of anti-Aß antibodies in the serum and the brain, and the macrophage phagocytosis of Aß are enhanced in rFOXN1-treated AD mice. CONCLUSIONS: Our results suggest that rFOXN1 protein has the potential to provide a novel approach to treat AD patients.

Administration of Recombinant TAPBPL Protein Ameliorates Collagen-Induced Arthritis in Mice.

Rheumatoid arthritis (RA) is a chronic inflammatory autoimmune disease distinguished by synovial hyperplasia and a progressive destruction of joints. T cells are critical players in the pathogenesis of RA. We have previously identified a novel immune checkpoint molecule, TAPBPL, that inhibits T cell functions in vitro. As a model for human RA, we investigated the ability of the TAPBPL protein to ameliorate collagen type II (CII)-induced arthritis (CIA) in mice that were injected with recombinant TAPBPL or a control protein. The mice were analyzed for CIA development, immune cells, and their responses. We found that TAPBPL protein significantly decreased CIA incidence and reduced clinical and pathological arthritis scores, which were related to a lower number of activated CD4 T cells but a greater number of regulatory T cells (Tregs) in the spleen, and a reduction of Th1/Th17 inflammatory cytokines in the joints and serum. Importantly, TAPBPL protein inhibited CII-specific T cell growth and Th1 and Th17 cytokine expression and reduced the production of CII autoantibodies in the serum. Our results suggest that TAPBPL protein can ameliorate CIA in mice and has the potential to be used in the treatment of patients with RA.

Gingival mesenchymal stem cell-derived exosomes are immunosuppressive in preventing collagen-induced arthritis.

Due to the unsatisfied effects of clinical drugs used in rheumatoid arthritis (RA), investigators shifted their focus on the biotherapy. Although human gingival mesenchymal stem cells (GMSC) have the potential to be used in treating RA, GMSC-based therapy has some inevitable side effects such as immunogenicity and tumorigenicity. As one of the most important paracrine mediators, GMSC-derived exosomes (GMSC-Exo) exhibit therapeutic effects via immunomodulation in a variety of disease models, bypassing potential shortcomings of the direct use of MSCs. Furthermore, exosomes are not sensitive to freezing and thawing, and can be readily available for use. GMSC-Exo has been reported to promote tissue regeneration and wound healing, but have not been reported to be effective against autoimmune diseases. We herein compare the immunomodulatory functions of GMSC-Exo and GMSC in collagen-induced arthritis (CIA) model and in vitro CD4+ T-cell co-culture model. The results show that GMSC-Exo has the same or stronger effects compared with GMSC in inhibiting IL-17A and promoting IL-10, reducing incidences and bone erosion of arthritis, via inhibiting IL-17RA-Act1-TRAF6-NF-κB signal pathway. Our results suggest that GMSC-Exo has many advantages in treating CIA, and may offer a promising new cell-free therapy strategy for RA and other autoimmune diseases.

Recombinant CD300c-Ig fusion protein attenuates collagen-induced arthritis in mice.

OBJECTIVES: RA is a chronic autoimmune disease characterized by joint inflammation and tissue destruction. Immune responses mediated by T cells and autoantibodies are known to play critical roles in RA. Collagen type II (CII)-induced arthritis (CIA) is a commonly used animal model of human RA. We have previously reported the identification of a new T cell inhibitory molecule CD300c. Here we investigate the ability of recombinant CD300c-IgG2a Fc (CD300c-Ig) fusion protein to prevent and treat CIA. METHODS: Mice were induced to develop CIA by CII and injected with CD300c-Ig or control Ig protein before or after CIA symptoms occur. The mice were examined for CIA clinical and pathological scores, and analysed for the expression of proinflammatory cytokines, the percentage and activation of CD4 T cells and regulatory T cells, CII-specific T cell proliferation and cytokine production, and CII-specific autoantibody production. RESULTS: In a prevention model, CD300c-Ig significantly decreases CIA incidence, and reduces clinical and pathological arthritis scores. In the treatment model, CD300c-Ig ameliorates established CIA. The beneficial effects of CD300c-Ig are related to decreased expansion and activation of T cells in the spleen and reduced expression of proinflammatory cytokines in the joints. CD300c-Ig also inhibits CII-specific T cell proliferation and Th1 and Th17 cytokine production. In addition, CD300c-Ig treatment reduced the production of CII autoantibodies in the serum. Furthermore, CD300c-Ig inhibits the proliferation and activation of T cells from RA patients in vitro. CONCLUSION: CD300c-Ig protein has the potential to be used in the treatment of patients with RA.

Administration of anti-ERMAP antibody ameliorates Alzheimer's disease in mice.

BACKGROUND: Alzheimer's disease (AD) is a devastating age-related neurodegenerative disorder and characterized by progressive loss of memory and cognitive functions, which are associated with amyloid-beta (Aß) plaques. Immune cells play an important role in the clearance of Aß deposits. Immune responses are regulated by immune regulators in which the B7 family members play a crucial role. We have recently identified erythroid membrane-associated protein (ERMAP) as a novel B7 family-related immune regulator and shown that ERMAP protein affects T cell and macrophage functions. METHODS: We produced a monoclonal antibody (mAb) against ERMAP protein and then determined the ability of the mAb to affect cognitive performance and AD pathology in mice. RESULTS:  We have shown that the anti-ERMAP mAb neutralizes the T cell inhibitory activity of ERMAP and enhances macrophages to phagocytose Aß in vitro. Administration of the mAb into AD mice improves cognitive performance and reduces Aß plaque load in the brain. This is related to increased proportion of T cells, especially IFNγ-producing T cells, in the spleen and the choroid plexus (CP), enhanced expression of immune cell trafficking molecules in the CP, and increased migration of monocyte-derived macrophages into the brain. Furthermore, the production of anti-Aß antibodies in the serum and the macrophage phagocytosis of Aß are enhanced in the anti-ERMAP mAb-treated AD mice. CONCLUSIONS: Our results suggest that manipulating the ERMAP pathway has the potential to provide a novel approach to treat AD patients.

Skint8, a Novel B7 Family-Related Molecule, Negatively Regulates T Cell Responses.

Immune responses are tightly controlled by T cell costimulatory and coinhibitory molecules. In this study, we identify Skint8 as a new member of the T cell coinhibitory group, whose extracellular domains share significant homology with existing B7 family members. Skint8 mRNA is expressed in resting and activated B cells, monocytes, and CD4 T cells. The Skint8 putative receptor is expressed on activated CD4 and CD8 T cells, B cells, monocytes and dendritic cells. Recombinant Skint8-IgG Fc fusion protein inhibits T cell proliferation, activation, and cytokine production in vitro. In vivo administration of Skint8-IgG Fc reduces T cell activation and alleviates experimental autoimmune encephalomyelitis in mice. The findings broaden our understanding of the regulation of immune responses and may have implications for treating immune-related diseases.

In vivo administration of recombinant BTNL2-Fc fusion protein ameliorates graft-versus-host disease in mice.

Although hematopoietic stem cell transplantation (HSCT) has been widely used in the treatment of many diseases, graft-versus-host disease (GVHD) remains a major complication after allogeneic HSCT. Butyrophilin-like 2 (BTNL2) protein has been reported to have the ability to inhibit T cell proliferation in vitro; its ability to inhibit T cell responses in vivo has not been determined. We show here that in vivo administration of recombinant BTNL2-IgG2a Fc (rBTNL2-Ig) fusion protein ameliorates GVHD in mice. This is related to the ability of rBTNL2-Ig to inhibit T cell proliferation, activation and Th1/Th17 cytokine production in vivo. Furthermore, rBTNL2-Ig treatment increases the generation of regulatory T cells. Our results suggest that rBTNL2-Ig has the potential to be used in the prevention and treatment of patients with GVHD.

Targeted deletion of c-Met in thymic epithelial cells leads to an autoimmune phenotype.

Hepatocyte growth factor (HGF) and its receptor c-Met signaling have been implicated in regulating various types of cells including epithelial cells. We have previously reported that c-Met is expressed by thymic epithelial cells (TECs), and that in vivo administration of hybrid cytokines containing IL-7 and the beta- or alpha-chain of HGF significantly increase the number of TECs. In order to study the role of c-Met signaling in TECs, we generated conditional knockout (cKO) mice in which c-Met was specifically deleted in TECs using a Foxn1-Cre transgene. We show here that c-Met deficiency in TECs results in age-progressive reduction in TEC number and reduced number of regulatory T cells. Consequently, c-Met TEC cKO mice displayed an autoimmune phenotype. Thus, c-Met signaling in TECs is important for the maintenance of TECs and immune self-tolerance.

FOXN1 recombinant protein enhances T-cell regeneration after hematopoietic stem cell transplantation in mice.

A prolonged period of T-cell recovery is the major challenge in hematopoietic stem cell transplantation (HSCT). Thymic epithelial cells (TECs) are the major component of the thymic microenvironment for T-cell generation. However, TECs undergo degeneration over time. FOXN1 plays a critical role in TEC development and is required to maintain adult TECs for thymopoiesis. To investigate the potential application of FOXN1, we have cloned and expressed recombinant FOXN1 protein (rFOXN1) that was fused with cell-penetrating peptides. We show here that the rFOXN1 protein can translocate from the cell surface into the cytoplasm and nucleus. Administration of rFOXN1 into both congenic and allogeneic HSCT recipient mice increased the number of TECs, resulting in enhanced thymopoiesis that led to an increased number of functional T cells in the periphery. The increased number of TECs is due to the enhanced survival and proliferation of TECs. Our results suggest that rFOXN1 has the potential to be used in enhancing T-cell regeneration in patients following HSCT.

ESC-derived thymic epithelial cells expressing MOG prevents EAE by central and peripheral tolerance mechanisms.

Experimental autoimmune encephalomyelitis (EAE) is an animal model for multiple sclerosis (MS), and is induced by immunization with disease-causative self-antigens such as myelin oligodendrocyte glycoprotein (MOG). We have previously reported that transplantation of MOG expressing thymic epithelial progenitors (TEPs) derived from 129S6SvEv Tac mouse embryonic stem cells (mESCs) prevented the development of EAE. In this study, we expand our previous studies to show that transplantation of MOG expressing mESC-TEPs derived from C57BL/6 mice also prevents EAE development. Furthermore, by using a MOG-specific T cell receptor (TCR) transgenic mouse model, we demonstrate that both central and peripheral tolerances are involved in the prevention of EAE induced by MOG expressing mESC-TEPs. Our results suggest that transplantation of human ESC-TEPs expressing MOG may provide an effective approach for the induction of MOG-specific immune tolerance, thereby the prevention and treatment of MS.

Recombinant IL-7/HGFß hybrid cytokine separates acute graft-versus-host-disease from graft-versus-tumour activity by altering donor T cell trafficking.

Given that donor T cells from a transplant contribute both the desired graft-versus-tumour (GVT) effect and detrimental graft-versus-host disease (GVHD), strategies to separate GVHD and GVT activity are a major clinical goal. We have previously demonstrated that in vivo administration of a recombinant (r)IL-7/HGFß hybrid cytokine, consisting of interleukin-7 (IL-7, IL7) and the ß-chain of hepatocyte growth factor (HGFß), significantly inhibits the growth of cancer cells in murine tumour models. The antit-umour effect of rIL-7/HGFß is related to a marked infiltration T cells in the tumour tissues. We have also shown that GVHD was not induced in rIL-7/HGFß-treated T cell-depleted allogeneic haematopoietic stem cell transplantation (HSCT) recipients. We show here that, in T cell-replete allogeneic HSCT murine models, rIL-7/HGFß attenuated acute GVHD (aGVHD), while promoting GVT activity. This was related to an alteration of donor T cell trafficking, with an increased infiltration of donor T cells into tumour tissues and the lympho-haematopoietic system but decreased number of the T cells in the GVHD target organs. Therefore, rIL-7/HGFß may offer a new tool to alleviate aGVHD while prompting GVT, and to study the molecular regulation of T cell trafficking.

c-Met signalling is required for efficient postnatal thymic regeneration and repair.

We have reported that in vivo administration of the hybrid cytokine rIL-7/HGFß or rIL-7/HGFα, which contains interleukin-7 (IL-7) and the ß- or α-chain of hepatocyte growth factor (HGF), significantly enhances thymopoiesis in mice after bone marrow transplantation. We have shown that the HGF receptor, c-Met, is involved in the effect of the hybrid cytokines. To address the role of c-Met signalling in thymocyte development and recovery, we generated conditional knockout (cKO) mice in which c-Met was specifically deleted in T cells by crossing c-Met(ft/ft) mice with CD4-Cre transgenic mice. We show here that although the number of total thymocytes and thymocyte subsets in young c-Met cKO mice is comparable to age-matched control (Ctrl) mice, the cKO mice were more susceptible to sub-lethal irradiation and dexamethasone treatment. This was demonstrated by low recovery in thymic cellularity in c-Met cKO mice after insult. Furthermore, the number of total thymocytes and thymocyte subsets was markedly reduced in 6- to 12-month-old cKO mice compared with age-matched Ctrl mice, and the thymic architecture of 12-month-old cKO mice was similar to that of 20-month-old wild-type mice. In addition, c-Met deficiency reduced cell survival and the expression of Bcl-xL in double-positive thymocytes, and decreased cell proliferation and the expression of cyclin E and cyclin-dependent kinase 5 in single-positive thymocytes. Our data indicate that c-Met signalling plays an important role in thymic regeneration after thymic insult. In addition, T-cell-specific inactivation of c-Met accelerates age-related thymic involution.

Administration of embryonic stem cell-derived thymic epithelial progenitors expressing MOG induces antigen-specific tolerance and ameliorates experimental autoimmune encephalomyelitis.

Tolerance induction, and thus prevention or treatment of autoimmune disease, is not only associated with the persistent presence of self-antigen in the thymus, but also relies on a functional thymus; however, the thymus undergoes profound age-dependent involution. Thymic epithelial cells (TECs) are the major component of the thymic microenvironment for T cell development. We have reported that mouse embryonic stem cells (mESCs) can be induced in vitro to generate thymic epithelial progenitors (TEPs) that further develop into functional TECs in vivo. We show here that transplantation of mESC-TEPs expressing self-antigen myelin oligodendrocyte glycoprotein (MOG) in mice results in enhanced T cell regeneration, long-term expression of MOG in the thymus, prevention of experimental autoimmune encephalomyelitis (EAE) development, and remission of established EAE. Our findings indicate that transplantation of ESC-TEPs expressing disease-causative self-antigen(s) may provide an effective approach for the prevention and treatment of autoimmune disease.

Long circulating self-assembled nanoparticles from cholesterol-containing brush-like block copolymers for improved drug delivery to tumors.

Amphiphilic brush-like block copolymers composed of polynorbonene-cholesterol/poly(ethylene glycol) (P(NBCh9-b-NBPEG)) self-assembled to form a long circulating nanostructure capable of encapsulating the anticancer drug doxorubicin (DOX) with high drug loading (22.1% w/w). The release of DOX from the DOX-loaded P(NBCh9-b-NBPEG) nanoparticles (DOX-NPs) was steady at less than 2% per day in PBS. DOX-NPs were effectively internalized by human cervical cancer cells (HeLa) and showed dose-dependent cytotoxicity, whereas blank nanoparticles were noncytotoxic. The DOX-NPs demonstrated a superior in vivo circulation time relative to that of free DOX. Tissue distribution and in vivo imaging studies showed that DOX-NPs preferentially accumulated in tumor tissue with markedly reduced accumulation in the heart and other vital organs. The DOX-NPs greatly improved survival and significantly inhibited tumor growth in tumor-bearing SCID mice compared to that for the untreated and free DOX-treated groups. The results indicated that self-assembled P(NBCh9-b-NBPEG) may be a useful carrier for improving tumor delivery of hydrophobic anticancer drugs.

Recombinant FOXN1 fusion protein increases T cell generation in old mice.

T cell development in the thymus is dependent on the thymic microenvironment, in which thymic epithelial cells (TECs) are the major component. However, TECs undergo both a qualitative and quantitative loss during aging, which is believed to be the major factor responsible for age-dependent thymic atrophy. FOXN1 plays a critical role in TEC development and adult TECs maintenance. We have previously reported that intrathymic injection of a recombinant (r) protein containing murine FOXN1 and a protein transduction domain increases the number of TECs in mice, leading to enhanced thymopoiesis. However, intrathymic injection may not be an ideal choice for clinical applications. In this study, we produced a rFOXN1 fusion protein containing the N-terminal of CCR9, human FOXN1 and a protein transduction domain. When injected intravenously into 14-month-old mice, the rFOXN1 fusion protein enters the thymus and TECs, and enhances thymopoiesis, resulting in increased T cell generation in the thymus and increased number of T cells in peripheral lymphoid organ. Our results suggest that the rFOXN1 fusion protein has the potential to be used in preventing and treating T cell immunodeficiency in older adults.

Mouse embryonic stem cell-derived thymic epithelial cell progenitors enhance T-cell reconstitution after allogeneic bone marrow transplantation.

We have reported that mouse embryonic stem cells (mESCs) can be selectively induced in vitro to differentiate into thymic epithelial cell progenitors (TEPs). When placed in vivo, these mESC-derived TEPs differentiate into cortical and medullary thymic epithelial cells, reconstitute the normal thymic architecture, and enhance thymocyte regeneration after syngeneic BM transplantation (BMT). Here, we show that transplantation of mESC-derived TEPs results in the efficient establishment of thymocyte chimerism and subsequent generation of naive T cells in both young and old recipients of allo-geneic BM transplant. GVHD was not induced, whereas graft-versus-tumor activity was significantly enhanced. Importantly, the reconstituted immune system was tolerant to host, mESC, and BM transplant donor antigens. Therefore, ESC-derived TEPs may offer a new approach for the rapid and durable correction of T-cell immune deficiency after BMT, and the induction of tolerance to ESC-derived tissue and organ transplants. In addition, ESC-derived TEPs may also have use as a means to reverse age-dependent thymic involution, thereby enhancing immune function and decreasing infection rates in the elderly.

In vivo administration of the recombinant IL-7/hepatocyte growth factor ß hybrid cytokine efficiently restores thymopoiesis and naive T cell generation in lethally irradiated mice after syngeneic bone marrow transplantation.

Bone marrow transplantation (BMT) is often followed by a prolonged period of T cell deficiency. Therefore, the enhancement of T cell reconstitution is an important clinical goal. We have identified a novel hybrid cytokine containing IL-7 and the ß-chain of hepatocyte growth factor (HGF) in the supernatant of cultured mouse BM stromal cells. We have cloned and expressed the IL-7/HGFß gene to produce a single-chain rIL-7/HGFß protein that stimulates the in vitro proliferation of thymocytes, early B-lineage cell, and day 12 spleen CFUs. In this study, we show that, following syngenic BMT, the in vivo administration of rIL-7/HGFß supports the rapid and complete regeneration of the thymus and efficiently reconstitutes the pool of naive T cells having a normally diverse TCR repertoire. The rIL-7/HGFß hybrid cytokine was significantly more effective quantitatively than was rIL-7 and differed qualitatively in its ability to cross-link c-Met and IL-7Rα and to stimulate the expansion of early thymocyte progenitors and thymic epithelial cells. It also supports the maturation and homeostatic expansion of peripheral T cells. Consequently, the in vivo administration of rIL-7/HGFß may offer a new approach to preventing and/or correcting post-BMT T cell immune deficiency.

Recombinant FOXN1 fusion protein increases T cell generation in aged mice.

Background: Although the thymus continues to export T cells throughout life, it undergoes a profound involution/atrophy with age, resulting in decreased numbers of T cells in the older adult, which has direct etiological linkages with many diseases. T cell development in the thymus is dependent on the thymic microenvironment, in which thymic epithelial cells (TECs) are the major component. However, TECs undergo both a qualitative and quantitative loss during aging, which is believed to be the major factor responsible for age-dependent thymic atrophy. FOXN1 plays a critical role in TEC development and adult TECs maintenance. We have previously reported that intrathymic injection of a recombinant (r) protein containing FOXN1 and a protein transduction domain increases the number of TECs in mice, leading to enhanced thymopoiesis. However, intrathymic injection may not be an ideal choice for clinical applications. In this study, we produce a rFOXN1 fusion protein containing the N-terminal of CCR9, FOXN1 and a protein transduction domain. Results: We show here that, when injected intravenously into aged mice, the rFOXN1 fusion protein migrates into the thymus and enhances thymopoiesis, resulting in increased T cell generation in the thymus and increased number of T cells in peripheral lymphoid organ. Conclusions: Our results suggest that the rFOXN1 fusion protein has the potential to be used in preventing and treating T cell immunodeficiency in the older adult.