Redirected T Cell Cytotoxicity in Cancer Therapy.

Bispecific antibodies that recruit and redirect T cells to attack tumor cells have tremendous potential for the treatment of various malignancies. In general, this class of therapeutics, known as CD3 bispecifics, promotes tumor cell killing by cross-linking a CD3 component of the T cell receptor complex with a tumor-associated antigen on the surface of the target cell. Importantly, this mechanism does not rely on a cognate interaction between the T cell receptor and a peptide:HLA complex, thereby circumventing HLA (human leukocyte antigen) restriction. Hence, CD3 bispecifics may find a key role in addressing tumors with low neoantigen content and/or low inflammation, and this class of therapeutics may productively combine with checkpoint blockade. A wide array of formats and optimization approaches has been developed, and a wave of CD3 bispecifics is proceeding into human clinical trials for a range of indications, with promising signs of therapeutic activity.

Mechanisms and Disease Associations of Haplotype-Dependent Allele-Specific DNA Methylation.

Haplotype-dependent allele-specific methylation (hap-ASM) can impact disease susceptibility, but maps of this phenomenon using stringent criteria in disease-relevant tissues remain sparse. Here we apply array-based and Methyl-Seq approaches to multiple human tissues and cell types, including brain, purified neurons and glia, T lymphocytes, and placenta, and identify 795 hap-ASM differentially methylated regions (DMRs) and 3,082 strong methylation quantitative trait loci (mQTLs), most not previously reported. More than half of these DMRs have cell type-restricted ASM, and among them are 188 hap-ASM DMRs and 933 mQTLs located near GWAS signals for immune and neurological disorders. Targeted bis-seq confirmed hap-ASM in 12/13 loci tested, including CCDC155, CD69, FRMD1, IRF1, KBTBD11, and S100A(∗)-ILF2, associated with immune phenotypes, MYT1L, PTPRN2, CMTM8 and CELF2, associated with neurological disorders, NGFR and HLA-DRB6, associated with both immunological and brain disorders, and ZFP57, a trans-acting regulator of genomic imprinting. Polymorphic CTCF and transcription factor (TF) binding sites were over-represented among hap-ASM DMRs and mQTLs, and analysis of the human data, supplemented by cross-species comparisons to macaques, indicated that CTCF and TF binding likelihood predicts the strength and direction of the allelic methylation asymmetry. These results show that hap-ASM is highly tissue specific; an important trans-acting regulator of genomic imprinting is regulated by this phenomenon; and variation in CTCF and TF binding sites is an underlying mechanism, and maps of hap-ASM and mQTLs reveal regulatory sequences underlying supra- and sub-threshold GWAS peaks in immunological and neurological disorders.

Targeting Syk-activated B cells in murine and human chronic graft-versus-host disease.

Novel therapies for chronic graft-versus-host disease (cGVHD) are needed. Aberrant B-cell activation has been demonstrated in mice and humans with cGVHD. Having previously found that human cGVHD B cells are activated and primed for survival, we sought to further evaluate the role of the spleen tyrosine kinase (Syk) in cGVHD in multiple murine models and human peripheral blood cells. In a murine model of multiorgan system, nonsclerodermatous disease with bronchiolitis obliterans where cGVHD is dependent on antibody and germinal center (GC) B cells, we found that activation of Syk was necessary in donor B cells, but not T cells, for disease progression. Bone marrow-specific Syk deletion in vivo was effective in treating established cGVHD, as was a small-molecule inhibitor of Syk, fostamatinib, which normalized GC formation and decreased activated CD80/86(+) dendritic cells. In multiple distinct models of sclerodermatous cGVHD, clinical and pathological disease manifestations were not eliminated when mice were therapeutically treated with fostamatinib, though both clinical and immunologic effects could be observed in one of these scleroderma models. We further demonstrated that Syk inhibition was effective at inducing apoptosis of human cGVHD B cells. Together, these data demonstrate a therapeutic potential of targeting B-cell Syk signaling in cGVHD.

ILT3.Fc inhibits the production of exosomes containing inflammatory microRNA in supernatants of alloactivated T cells.

Immune activation needs to be tightly regulated to control immune-mediated tissue damage. Inhibitory pathways serve to terminate an immune response and resolve inflammation. Persistent exposure to antigens can drive development of adaptive regulatory cells. Similarly exposure of activated T cells to the recombinant ILT3-Fc molecule during priming triggers the differentiation of CD8 T suppressor cells and the induction of CD4 T helper anergy. Ts express high levels of immunoregulatory signature genes together with low levels of microRNA which control their function. Analysis of microRNA contained by exosomes from cultures in which T cells were alloactivated in the presence or absence of ILT3.Fc, demonstrated that this agent inhibits the release of inflammatory microRNA. The source of such inflammatory microRNA was found to reside in alloactivated CD4 T cells, since exosomes from MLC primed CD4 T cells were shown to diminish the suppressive activity of ILT3-Fc-induced CD8(+) Ts at high effector to suppressor T cell ratios. This indicates that inflammatory exosomes can swing the balance between effector and regulatory T cells in favor of immunity. These data suggest that isolation and characterization of micro-RNA containing exosomes in patients' circulation may be of use for treatment, prevention and monitoring of immune activation.

Detection of donor-specific-antibodies by solid phase assay and its relevance to complement-dependent-lymphocytotoxicity cross-matching in kidney transplantation.

Presensitization against a broad array of HLA is associated with prolonged waiting times and inferior kidney allogaft survival. Although the use of solid phase assay (SPA) for the detection and characterization of anti-HLA antibodies provides greater sensitivity than complement-dependent lymphocytotoxicity (CDC) assay, it often detects donor specific antibodies (DSA) which turn out to be clinically irrelevant. Our data reinforce the concept that these two types of assays should be used in parallel for pre-and post-transplantation monitoring of anti-HLA antibodies in recipients of solid organ allografts.

Allospecific CD8 T suppressor cells induced by multiple MLC stimulation or priming in the presence of ILT3.Fc have similar gene expression profiles.

Alloantigen specific CD8 T suppressor cells can be generated in vitro either by multiple stimulations of CD3 T cells with allogeneic APC or by single stimulation in primary MLC containing recombinant ILT3.Fc protein. The aim of the present study was to determine whether multiple MLC stimulation induced in CD8(+) CD28(-) T suppressor cells molecular changes that are similar to those observed in CD8 T suppressor cells from primary MLC containing ILT3.Fc protein. Our study demonstrates that the characteristic signatures of CD8 T suppressor cells, generated by either of these methods are the same consisting of up-regulation of the BCL6 transcriptional repressor and down-regulation of inflammatory microRNAs, miR-21, miR-30b, miR-146a, and miR-155 expression. In conclusion microRNAs which are increased under inflammatory conditions in activated CD4 and CD8 T cells with helper or cytotoxic function show low levels of expression in CD8 T cells which have acquired antigen-specific suppressor activity.

Downregulation of inflammatory microRNAs by Ig-like transcript 3 is essential for the differentiation of human CD8(+) T suppressor cells.

We have investigated the mechanism underlying the immunoregulatory function of membrane Ig-like transcript 3 (ILT3) and soluble ILT3Fc. microRNA (miRNA) expression profile identified genes that were downregulated in ILT3-induced human CD8(+) T suppressor cells (Ts) while upregulated in T cells primed in the absence of ILT3. We found that miR-21, miR-30b, and miR-155 target the 3'-untranslated region of genes whose expression was strongly increased in ILT3Fc-induced Ts, such as dual specificity phosphatase 10, B cell CLL/lymphoma 6, and suppressor of cytokine signaling 1, respectively. Transfection of miRNA mimics or inhibitors and site-specific mutagenesis of their 3'-untranslated region binding sites indicated that B cell CLL/lymphoma 6, dual specificity phosphatase 10, and suppressor of cytokine signaling 1 are direct targets of miR-30b, miR-21, and miR-155. Primed CD8(+) T cells transfected with miR-21&30b, miR-21&155, or miR-21&30b&155 inhibitors displayed suppressor activity when added to autologous CD3-triggered CD4 T cells. Luciferase reporter assays of miR-21 and miR-155 indicated that their transcription is highly dependent on AP-1. Analysis of activated T cells showed that ILT3Fc inhibited the translocation to the nucleus of the AP-1 subunits, FOSB and c-FOS, and the phosphorylation of ZAP70 and phospholipase C-γ 1. In conclusion, ILT3Fc inhibits T cell activation and induces the generation of Ts targeting multiple inflammatory miRNA pathways.

Mouse models of IgG- and IgM-mediated hemolysis.

Well-characterized mouse models of allo-immune antibody-mediated hemolysis would provide a valuable approach for gaining greater insight into the pathophysiology of hemolytic transfusion reactions. To this end, mouse red blood cells (mRBCs) from human glycophorin A transgenic (hGPA-Tg) donor mice were transfused into non-Tg recipients that had been passively immunized with IgG or IgM hGPA-specific monoclonal antibodies (mAbs). In this novel murine "blood group system," mRBCs from hGPA-Tg mice are "antigen positive" and mRBCs from non-Tg mice are "antigen negative." Passive immunization of non-Tg mice with the IgG1 10F7 and IgG3 NaM10-2H12 anti-hGPA mAbs each induced rapid clearance of incompatible transfused hGPA-Tg-mRBCs in a dose-response manner. Using various knockout mice as transfusion recipients, both the complement system and activating Fcgamma receptors were found to be important in the clearance of incompatible mRBCs by each of these IgG mAbs. In addition, the IgM E4 anti-hGPA mAb induced complement-dependent intravascular hemolysis of transfused incompatible hGPA-Tg-mRBCs accompanied by gross hemoglobinuria. These initial studies validate the relevance of these new mouse models for addressing important questions in the field of transfusion medicine.

Redundant and alternative roles for activating Fc receptors and complement in an antibody-dependent model of autoimmune vitiligo.

Complement and Fc receptor (FcR)-positive cells mediate effector functions of antibodies. Antibody-dependent immunity against the melanosome membrane glycoprotein gp75/tyrosinase-related protein-1 (TYRP-1) of melanocytes leads to autoimmune hypopigmentation (vitiligo) in mice. Hypopigmentation occurred in mice deficient in activating FcR containing the common gamma subunit (Fc gamma R gamma(-/-)) and in mice deficient in the C3 complement component. Mice doubly deficient in both Fc gamma R gamma and C3 did not develop hypopigmentation, suggesting that complement and Fc gamma R formed redundant mechanisms. Following passive immunization with antibody, no further adaptive immune responses were required. Chimeric Fc gamma R gamma(-/-),C3(-/-) mice reconstituted with bone marrow from either Fc gamma R gamma(-/-) or C3(-/-) mice or adoptively transferred with Fc gamma R gamma(+/-) macrophages did develop antibody-mediated hypopigmentation. Thus, either complement or macrophages expressing activating Fc gamma R can independently and alternatively mediate disease in a model of autoimmune vitiligo.