Deletion of CD98 heavy chain in T cells results in cardiac allograft acceptance by increasing regulatory T cells

Progress, implications, and challenges in using humanized immune system mice in CAR-T therapy-Application evaluation and improvement

In recent years, humanized immune system (HIS) mice have been gradually used as models for preclinical research in pharmacotherapies and cell therapies with major breakthroughs in tumor and other fields, better mimicking the human immune system and the tumor immune microenvironment, compared to traditional immunodeficient mice. To better promote the application of HIS mice in preclinical research, we selectively summarize the current prevalent and breakthrough research and evaluation of chimeric antigen receptor (CAR) -T cells in various antiviral and antitumor treatments. By exploring its application in preclinical research, we find that it can better reflect the actual clinical patient condition, with the advantages of providing high-efficiency detection indicators, even for progressive research and development. We believe that it has better clinical patient simulation and promotion for the updated design of CAR-T cell therapy than directly transplanted immunodeficient mice. The characteristics of the main models are proposed to improve the use defects of the existing models by reducing the limitation of antihost reaction, combining multiple models, and unifying sources and organoid substitution. Strategy study of relapse and toxicity after CAR-T treatment also provides more possibilities for application and development.

Clinical significance of the CD98hc-CD147 complex in ovarian cancer: a bioinformatics analysis

Ovarian cancer is one of the most common malignant tumours affecting the female reproductive organs. CD147 (BSG) and CD98hc (SLC3A2) are oncogenes that form the CD98hc-CD147 complex, which regulates the proliferation, metastasis, metabolism, and cell cycle of cancer cells. The roles of the CD98hc-CD147 complex in ovarian cancer remain unclear. We analysed the expression and prognostic value of CD147 and CD98hc in ovarian cancer using the TCGA and ICGC databases. The effect of CD147 and CD98hc on the tumour immune response was analysed using the TIMER database. CD98hc was more highly expressed in normal tissues than primary tumour tissues, while CD147 was more highly expressed in primary tumour tissues than normal tissues. CD98hc expression was significantly associated with neutrophil and dendritic cell levels. CD147 and CD98hc were correlated with DNA repair, the cell cycle, and DNA replication. The CD98hc-CD147 complex could serve as a target for ovarian cancer treatment.

CD98 heavy chain as a prognostic biomarker and target for cancer treatment

The SLC3A2 gene encodes for a cell-surface transmembrane protein CD98hc (4F2). CD98hc serves as a chaperone for LAT1 (SLC7A5), LAT2 (SLC7A8), y+LAT1 (SLC7A7), y+LAT2 (SLC7A6), xCT (SLC7A11) and Asc1 (SLC7A10) providing their recruitment to the plasma membrane. Together with the light subunits, it constitutes heterodimeric transmembrane amino acid transporters. CD98hc interacts with other surface molecules, such as extracellular matrix metalloproteinase inducer CD147 (EMMPRIN) and adhesion receptors integrins, and regulates glucose uptake. In this way, CD98hc connects the signaling pathways sustaining cell proliferation and migration, biosynthesis and antioxidant defense, energy production, and stem cell properties. This multifaceted role makes CD98hc one of the critical regulators of tumor growth, therapy resistance, and metastases. Indeed, the high expression levels of CD98hc were confirmed in various tumor tissues, including head and neck squamous cell carcinoma, glioblastoma, colon adenocarcinoma, pancreatic ductal adenocarcinoma, and others. A high expression of CD98hc has been linked to clinical prognosis and response to chemo- and radiotherapy in several types of cancer. In this mini-review, we discuss the physiological functions of CD98hc, its role in regulating tumor stemness, metastases, and therapy resistance, and the clinical significance of CD98hc as a tumor marker and therapeutic target.

Identification of CD98 as a Novel Biomarker for HIV-1 Permissiveness and Latent Infection

Human immunodeficiency virus type 1 (HIV-1) can integrate viral DNA into host cell chromosomes to establish a long-term stable latent reservoir, which is a major obstacle to cure HIV-1 infection. The characteristics of the HIV-1 latent reservoir have not been fully understood. Here, we identified 126 upregulated plasma membrane proteins in HIV-1 latently infected cells by a label-free liquid chromatography-tandem mass spectrometry analysis. The higher levels of CD98 expression in multiple HIV-1 latently infected cell lines and primary CD4+ T cells compared to uninfected cells were further confirmed by quantitative reverse transcription PCR (RT-qPCR) and flow cytometry analyses. In addition, CD98high CD4+ T cells displayed hyper-permissiveness to HIV-1 infection and possessed distinct immune phenotypic profiles associated with Th17 and peripheral follicular T helper (pTFH) characteristics. Notably, the CD98high resting memory CD4+ T cells harbored significantly higher cell-associated viral RNA and intact provirus than CD98low counterparts in HIV-1-infected individuals receiving combined antiretroviral therapy. Furthermore, CD98high CD4+ T cells exhibited a robust proliferative capacity and significantly contributed to the clonal expansion of the HIV-1 latent reservoir. Our study demonstrates that CD98 can be used as a novel biomarker of HIV-1 latently infected cells to indicate the effect of various strategies to reduce the viral reservoir. IMPORTANCE Identification of cellular biomarkers is the crucial challenge to eradicate the HIV-1 latent reservoir. In our study, we identified CD98 as a novel plasma membrane biomarker for HIV-1 permissiveness and latent infection. Importantly, CD98high CD4+ T cells exhibited a hyper-permissiveness to HIV-1 infection and significantly contributed to the clonal expansion of the HIV-1 latent reservoir. CD98 could be targeted to develop therapeutic strategies to reduce the HIV-1 latent reservoir in further research.

T-cell Immunometabolism: Therapeutic Implications in Organ Transplantation

Although solid-organ transplantation has evolved steadily with many breakthroughs in the past 110 y, many problems remain to be addressed, and advanced therapeutic strategies need to be considered. T-cell immunometabolism is a rapidly advancing field that has gathered much attention recently, providing ample mechanistic insight from which many novel therapeutic approaches have been developed. Applications from the field include antitumor and antimicrobial therapies, as well as for reversing graft-versus-host disease and autoimmune diseases. However, the immunometabolism of T cells remains underexplored in solid-organ transplantation. In this review, we will highlight key findings from hallmark studies centered around various metabolic modes preferred by different T-cell subtypes (categorized into naive, effector, regulatory, and memory T cells), including glycolysis, glutaminolysis, oxidative phosphorylation, fatty acid synthesis, and oxidation. This review will discuss the underlying cellular signaling components that affect these processes, including the transcription factors myelocytomatosis oncogene, hypoxia-inducible factor 1-alpha, estrogen-related receptor alpha, and sterol regulatory element-binding proteins, along with the mechanistic target of rapamycin and adenosine monophosphate-activated protein kinase signaling. We will also explore potential therapeutic strategies targeting these pathways, as applied to the potential for tolerance induction in solid-organ transplantation.

Monotherapy With Anti-CD70 Antibody Causes Long-Term Mouse Cardiac Allograft Acceptance With Induction of Tolerogenic Dendritic Cells

Allograft rejection has been an obstacle for the long-term survival of patients. CD70, a tumor necrosis factor (TNF) family member critically expressed on antigen-presenting cells and strongly but transiently up-regulated during lymphocyte activation, represents an important co-stimulatory molecule that induces effective T cell responses. We used a mouse heterotopic cardiac transplantation model to evaluate the effects of monotherapy with the antibody targeting mouse CD70 (FR70) on transplantation tolerance and its immunoregulatory activity. FR70-treated C3H recipient mice permanently accepted B6 fully mismatched cardiac allografts. Consistent with the graft survival, the infiltration of CD8⁺ T cells in the graft was reduced, dendritic cells were differentiated into a tolerogenic status, and the number of regulatory T cells was elevated both in the graft and the recipient’s spleen. In addition, naïve C3H given an adoptive transfer of spleen cells from the primary recipients with FR70 treatment accepted a heart graft from a matching B6 donor but not third-party BALB/c mice.　Our findings show that treatment with FR70 induced regulatory cells and inhibited cytotoxic T cell proliferation, which led to long-term acceptance of mouse cardiac allografts. These findings highlight the potential role of anti-CD70 antibodies as a clinically effective treatment for allograft rejection.

iPSC-Derived Regulatory Dendritic Cells Inhibit Allograft Rejection by Generating Alloantigen-Specific Regulatory T Cells

Regulatory dendritic cell (DCregs)-based immunotherapy is a potential therapeutic tool for transplant rejection. We generated DCregs from murine induced pluripotent stem cells (iPSCs), which could remain in a “stable immature stage” even under strong stimulation. Harnessing this characteristic, we hypothesized that iPS-DCregs worked as a negative vaccine to generate regulatory T cells (Tregs), and induced donor-specific allograft acceptance. We immunized naive CBA (H-2K^k) mice with B6 (H-2K^b) iPS-DCregs and found that Tregs (CD4⁺CD25⁺FOXP3⁺) significantly increased in CBA splenocytes. Moreover, immunized CBA recipients permanently accepted B6 cardiac grafts in a donor-specific pattern. We demonstrated mechanistically that donor-type iPS-DCregs triggered transforming growth factor β1 secretion, under which the donor-antigen peptides directed naive CD4⁺ T cells to differentiate into donor-specific FOXP3⁺ Tregs instead of into effector T cells in vivo. These findings highlight the potential of iPS-DCregs as a key cell therapy resource in clinical transplantation.

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iPS-DCregs keep in stable immature stage that makes them a powerful cellular vaccine

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Donor-type iPS-DCregs lead to permanent acceptance of allogeneic cardiac grafts

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iPS-DCregs reduce CTL and downregulate proinflammatory cytokine

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iPS-DCregs enhance Tregs transmigration capability in a TGF-β1-dependent manner

Amino-acid transporters in T-cell activation and differentiation

T-cell-mediated immune responses aim to protect mammals against cancers and infections, and are also involved in the pathogenesis of various inflammatory or autoimmune diseases. Cellular uptake and the utilization of nutrients is closely related to the T-cell fate decision and function. Research in this area has yielded surprising findings in the importance of amino-acid transporters for T-cell development, homeostasis, activation, differentiation and memory. In this review, we present current information on amino-acid transporters, such as LAT1 (l-leucine transporter), ASCT2 (l-glutamine transporter) and GAT-1 (γ-aminobutyric acid transporter-1), which are critically important for mediating peripheral naive T-cell homeostasis, activation and differentiation, especially for Th1 and Th17 cells, and even memory T cells. Mechanically, the influence of amino-acid transporters on T-cell fate decision may largely depend on the mechanistic target of rapamycin complex 1 (mTORC1) signaling. These discoveries remarkably demonstrate the role of amino-acid transporters in T-cell fate determination, and strongly indicate that manipulation of the amino-acid transporter-mTORC1 axis could ameliorate many inflammatory or autoimmune diseases associated with T-cell-based immune responses.

MicroRNAs Involved in Acute Rejection and Tolerance in Murine Cardiac Allografts

OBJECTIVES

Induction of immunologic tolerance is the ultimate goal of organ transplant. To investigate the involvement of microRNA in tolerance induction after organ transplant, murine cardiac allografts were performed and the expression of microRNA in the grafts was analyzed.

MATERIALS AND METHODS

Cardiac allografts were performed using C57BL/10 (H2-Kb) to CBA/N (H2-Kk) fully mismatched combination with or without eicosapentaenoic acid for tolerance induction. Ten microRNA, mir-146a, 15b, 223, 23a, 27a, 34a, 451, 101a, 101b, 148a, discovered in hepatic grafts were examined by quantitative reverse transcription polymerase chain reaction using RNA from the cardiac allografts.

RESULTS

The administration of eicosapentaenoic acid markedly prolonged the cardiac allograft survival (median survival time > 100 days) and decreased the pathological score. Quantitative reverse transcription polymerase chain reaction revealed that mir-223 was up-regulated in accordance with pathological deterioration as compared with the expression observed in the syngeneic grafts. In contrast, the other microRNA was down-regulated. Pearson product moment correlation analysis demonstrated that the expression patterns of mir-223 and mir-146a had high or moderate positive associations between the cardiac and haptic allografts in mice.

CONCLUSIONS

The change in the microRNA expression in the allografts suggests that microRNA plays a role in the induction and/or maintenance of tolerance after allograft transplant. Our findings suggest that mir-223 may be associated with rejection while mir-146a, -15b, -23a, -27a, -34a, -451, -101a, -101b, -148a may be involved in tolerance. A superior grasp of the mechanism for rejection and tolerance observed in the murine heart allotransplant model may provide a better curative treatment strategy to mitigate allograft rejection.

Impaired CD98 signaling protects against graft-versus-host disease by increasing regulatory T cells

Graft-versus-host disease (GvHD) is a major barrier to the broader use of allogenic hematopoietic stem cell transplantation for non-malignant clinical applications. A murine model of C57BL/6 to B6D2F1 acute GvHD was employed with T lymphocytes harboring a deletion of the CD98 heavy chain (CD98hc(-/-)) as donor cells. The CD98hc(-/-) resulted in lower responses to alloantigen stimulation in a mixed leukocyte reaction assay, and prevented the mortality associated with disease progression. The percentage of donor CD8 T lymphocytes was significantly decreased, while the percentage of Foxp3-positive regulatory T cells (Tregs) in recipients was increased by CD98hc(-/-). Decreased expression of FAS, FASL, ICOS, ICOSL, PD-1 and PD-L1 by donor CD8 T cells, and mRNA expression of cytotoxic T cell-related cytokines in the recipients were shown in those with CD98hc(-/-). Fewer infiltrated cells are found in the lungs, liver, tongue and skin of recipients with CD98hc(-/-) compared with the wild type recipients. Taken together, our data indicate that T cell-specific deletion of CD98hc can contribute to the prevention of GvHD development due to the attenuation of lymphocyte migration and by increasing the generation of Treg cells. These findings are expected to make it possible to develop novel approaches for the prevention of GvHD.

Conditional deletion of CD98hc inhibits osteoclast development

The CD98 heavy chain (CD98hc) regulates virus-induced cell fusion and monocyte fusion, and is involved in amino acid transportation. Here, we examined the role that CD98hc plays in the formation of osteoclasts using CD98hc^flox/floxLysM-cre peritoneal macrophages (CD98hc-defect macrophages). Peritoneal macrophages were stimulated with co-cultured with osteoblasts in the presence of 1,25(OH)² vitamin D₃, and thereafter stained with tartrate-resistant acid phosphatase staining solution. The multinucleated osteoclast formation was severely impaired in the peritoneal macrophages isolated from the CD98hc^-defect mice compared with those from wild-type mice. CD98hc mediates integrin signaling and amino acid transport through the CD98 light chain (CD98lc). In integrin signaling, suppression of the M-CSF-RANKL-induced phosphorylation of ERK, Akt, JNK and p130Cas were observed at the triggering phase in the CD98h-defect peritoneal macrophages. Moreover, we showed that the general control non-derepressible (GCN) pathway, which was activated by amino acid starvation, was induced by the CD98hc-defect peritoneal macrophages stimulated with RANKL. These results indicate that CD98 plays two important roles in osteoclast formation through integrin signaling and amino acid transport.

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The osteoclastogenesis was severely impaired in the CD98hc-defect macrophages.

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CD98hc-defect peritoneal macrophages fall into amino acid starvation, resulting in inducing the general control non-derepressible (GCN) pathway in the osteoclastogenesis.

CD98 Heavy Chain Is a Potent Positive Regulator of CD4+ T Cell Proliferation and Interferon-γ Production In Vivo

Upon their recognition of antigens presented by the MHC, T cell proliferation is vital for clonal expansion and the acquisition of effector functions, which are essential for mounting adaptive immune responses. The CD98 heavy chain (CD98hc, Slc3a2) plays a crucial role in the proliferation of both CD4⁺ and CD8⁺ T cells, although it is unclear if CD98hc directly regulates the T cell effector functions that are not linked with T cell proliferation in vivo. Here, we demonstrate that CD98hc is required for both CD4⁺ T cell proliferation and Th1 functional differentiation. T cell-specific deletion of CD98hc did not affect T cell development in the thymus. CD98hc-deficient CD4⁺ T cells proliferated in vivo more slowly as compared with control T cells. C57BL/6 mice lacking CD98hc in their CD4⁺ T cells could not control Leishmania major infections due to lowered IFN-γ production, even with massive CD4⁺ T cell proliferation. CD98hc-deficient CD4⁺ T cells exhibited lower IFN-γ production compared with wild-type T cells, even when comparing IFN-γ expression in cells that underwent the same number of cell divisions. Therefore, these data indicate that CD98hc is required for CD4⁺ T cell expansion and functional Th1 differentiation in vivo, and suggest that CD98hc might be a good target for treating Th1-mediated immune disorders.

5-Aminolevulinic acid with ferrous iron induces permanent cardiac allograft acceptance in mice via induction of regulatory cells

BACKGROUND

5-Aminolevulinic acid (5-ALA), a precursor of heme biosynthesis, plays a fundamentally important role in aerobic energy metabolism. Heme oxygenase (HO)-1 cleaves heme to form biliverdin, carbon monoxide (CO) and iron (Fe(2+)). The anti-inflammatory properties of biliverdin and CO help to alleviate ischemia/reperfusion injury as well as acute and/or chronic allograft rejection. We investigated whether 5-ALA and Fe(2+) exerts salutary effects in the setting of organ transplantation.

METHODS

An in vitro mixed-lymphocyte reaction (MLR) assay and cardiac allotransplantation model (CBA to C57BL/10) were used to evaluate the effects of 5-ALA and Fe(2+) on transplantation tolerance.

RESULTS

Treatment with 5-ALA and sodium ferrous citrate (SFC) resulted in permanent acceptance in the murine cardiac allografts in a dose-, SFC- and HO-1-dependent manner. The number of graft-infiltrating CD8 T cells was lower and the survival response of recipient spleen T cells to donor-type alloantigens was less compared with control recipients; however, numbers of both regulatory T cells and dendritic cells were significantly increased in 5-ALA/SFC-treated recipients.

CONCLUSIONS

Our findings show that 5-ALA/SFC inhibits T-cell proliferation in response to alloantigens and an increased number of regulatory cells, resulting in permanent cardiac allograft acceptance in mice. These findings highlight the major roles of CO and/or HO-1 in inducing tolerance and suggest that 5-ALA/SFC may be a clinically effective treatment for allograft rejection.

CD98hc regulates the development of experimental colitis by controlling effector and regulatory CD4(+) T cells

CD4(+) T cell activation is controlled by signaling through the T cell receptor in addition to various co-receptors, and is also affected by their interactions with effector and regulatory T cells in the microenvironment. Inflammatory bowel diseases (IBD) are caused by the persistent activation and expansion of auto-aggressive CD4(+) T cells that attack intestinal epithelial cells. However, the molecular basis for the persistent activation of CD4(+) T cells in IBD remains unclear. In this study, we investigated how the CD98 heavy chain (CD98hc, Slc3a2) affected the development of colitis in an experimental animal model. Transferring CD98hc-deficient CD4(+)CD25(-) T cells into Rag2(-/-) mice did not cause colitis accompanied by increasing Foxp3(+) inducible regulatory T cells. By comparison, CD98hc-deficient naturally occurring regulatory T cells (nTregs) had a decreased capability to suppress colitis induced by CD4(+)CD25(-) T cells, although CD98hc-deficient mice did not have a defect in the development of nTregs. Blocking CD98hc with an anti-CD98 blocking antibody prevented the development of colitis. Our results indicate that CD98hc regulates the expansion of autoimmune CD4(+) T cells in addition to controlling nTregs functions, which suggests the CD98hc as an important target molecule for establishing strategies for treating colitis.

Control of amino-acid transport by antigen receptors coordinates the metabolic reprogramming essential for T cell differentiation

T lymphocytes must regulate nutrient uptake to meet the metabolic demands of an immune response. Here we show that the intracellular supply of large neutral amino acids (LNAAs) in T cells was regulated by pathogens and the T cell antigen receptor (TCR). T cells responded to antigen by upregulating expression of many amino-acid transporters, but a single System L ('leucine-preferring system') transporter, Slc7a5, mediated uptake of LNAAs in activated T cells. Slc7a5-null T cells were unable to metabolically reprogram in response to antigen and did not undergo clonal expansion or effector differentiation. The metabolic catastrophe caused by loss of Slc7a5 reflected the requirement for sustained uptake of the LNAA leucine for activation of the serine-threonine kinase complex mTORC1 and for expression of the transcription factor c-Myc. Control of expression of the System L transporter by pathogens is thus a critical metabolic checkpoint for T cells.