Scientific Resources

Chronic lymphocytic leukemia/small lymphocytic lymphoma (CLL/SLL) is a low-grade B-cell neoplasm and ∼2{\%} to 9{\%} patients develop an aggressive lymphoma,most commonly diffuse large B-cell lymphoma (Richter transformation,DLBCL-RT). Programmed death-1 (PD-1) pathway plays a crucial role in tumor host immunity evasion and its blockade has emerged as an effective anti-cancer immunotherapy. PD-L1 and PD-1 expression has shown predictive value in anti-PD cancer immunotherapy; however,it has not been well documented in CLL/SLL and DLBCL-RT. We evaluated PD-1 and PD-L1 expression by immunohistochemistry in 39 CLL/SLL,15 DLBCL-RT,and 26 other DLBCL. In CLL/SLL,neoplastic B-cell PD-1 expression was weak and restricted to prolymphocytes/paraimmunoblasts within proliferation centers (PCs) and accentuated PCs of all sizes. Neoplastic B-cell PD-1 expression was highly prevalent and demonstrated increased intensity in DLBCL-RT,but in contrast was only rarely seen in other DLBCL (12/15 vs. 1/26; P{\textless}0.0001). An excellent correlation (90{\%} concordance) was observed between neoplastic B-cell PD-1 immunohistochemistry positivity and molecularly defined CLL/SLL clonal relatedness in DLBCL-RT. PD-L1 expression was observed on the neoplastic B cells in rare DLBCL-RT and other DLBCL cases (1/15 vs. 1/26; P{\textgreater}0.05) as well as background histiocytes and dendritic cells. Overall survival of DLBCL-RT was significantly inferior to that of the other DLBCL (median,16.9 vs. 106.1 mo; P=0.002). Our findings suggest a biological continuum from prolymphocytes/paraimmunoblasts in CLL/SLL PCs to the neoplastic B-cells in DLBCL-RT. The characteristic PD-1 expression in DLBCL-RT makes it a potential surrogate marker for determining clonal relatedness to CLL/SLL,which may have important prognostic and therapeutic implications. View Publication

Recently,deficiency in the cytosolic DNA sensor RNA Polymerase III was described in children with severe primary varicella-zoster virus (VZV) infection in the CNS and lungs. In the present study we examined adult patients with VZV CNS infection caused by viral reactivation. By whole exome sequencing we identified mutations in POL III genes in two of eight patients. These mutations were located in the coding regions of the subunits POLR3A and POLR3E. In functional assays,we found impaired expression of antiviral and inflammatory cytokines in response to the POL III agonist Poly(dA:dT) as well as increased viral replication in patient cells compared to controls. Altogether,this study provides significant extension on the current knowledge on susceptibility to VZV infection by demonstrating mutations in POL III genes associated with impaired immunological sensing of AT-rich DNA in adult patients with VZV CNS infection. View Publication

Human induced pluripotent stem cells (iPSC) have the potential to radically reduce the number of animals used in both toxicological science and disease elucidation. One initial obstacle culturing iPSC is that they require daily medium exchange. This study attempts to clarify why and propose some practical solutions. Two iPSC lineages were fed at different intervals in a full growth area (FGA) or a restricted growth area (RGA). The FGA consisted of a well coated with Matrigel™ and the RGA consisted of a coated coverslip placed in a well. Glucose,lactate,extracellular pH and cell cycle phases were quantified. Without daily feeding,FGA cultured iPSC had significantly reduced growth rates by day 2 and began to die by day 3. In contrast,RGA cultured cells grew to confluence over 3 days. Surprisingly,glucose was not exhausted under any condition. However,extracellular pH reached 6.8 after 72 h in FGA cultures. Artificially reducing medium pH to 6.8 also inhibited glycolysis and initiated an increase in G0/G1 phase of the cell cycle,while adding an additional 10 mM bicarbonate to the medium increased glycolysis rates. This study demonstrates that iPSC are highly sensitive to extracellular acidification,a likely limiting factor in maintenance of proliferative and pluripotent status. Culturing iPSC in RGA prevents rapid extracellular acidification,while still maintaining pluripotency and allowing longer feeding cycles.

Monocytes are key cells of the innate immune system. Their phenotypic and functional roles have been investigated in humans,mice and other animals,such as the rat,pig and cow. To date,detailed phenotypic analysis of monocytes has not been undertaken in dogs. Two important surface markers in human monocytes are CD14 and MHC class II (MHC II). By flow cytometry,we demonstrated that canine monocytes can be subdivided into three separate populations: CD14posMHC IIneg,CD14posMHC IIpos and CD14negMHC IIpos. Both light and transmission electron microscopy confirmed the monocytic identity of all three populations. The CD14posMHC IIneg population could be distinguished on an ultrastructural level by their smaller size,the presence of more numerous,larger granules,and more pseudopodia than both of the other populations. View Publication

Baboons naturally infected with simian T lymphotropic virus (STLV) are a potentially useful model system for the study of vaccination against human T lymphotropic virus (HTLV). Here we expanded the number of available full-length baboon STLV-1 sequences from one to three and related the T cell responses that recognize the immunodominant Tax protein to the tax sequences present in two individual baboons. Continuously growing T cell lines were established from two baboons,animals 12141 and 12752. Next-generation sequencing (NGS) of complete STLV genome sequences from these T cell lines revealed them to be closely related but distinct from each other and from the baboon STLV-1 sequence in the NCBI sequence database. Overlapping peptides corresponding to each unique Tax sequence and to the reference baboon Tax sequence were used to analyze recognition by T cells from each baboon using intracellular cytokine staining (ICS). Individual baboons expressed more gamma interferon and tumor necrosis factor alpha in response to Tax peptides corresponding to their own STLV-1 sequence than in response to Tax peptides corresponding to the reference baboon STLV-1 sequence. Thus,our analyses revealed distinct but closely related STLV-1 genome sequences in two baboons,extremely low heterogeneity of STLV sequences within each baboon,no evidence for superinfection within each baboon,and a ready ability of T cells in each baboon to recognize circulating Tax sequences. While amino acid substitutions that result in escape from CD8+ T cell recognition were not observed,premature stop codons were observed in 7{\%} and 56{\%} of tax sequences from peripheral blood mononuclear cells from animals 12141 and 12752,respectively.IMPORTANCE It has been estimated that approximately 100,000 people suffer serious morbidity and 10,000 people die each year from the consequences associated with human T lymphotropic virus (HTLV) infection. There are no antiviral drugs and no preventive vaccine. A preventive vaccine would significantly impact the global burden associated with HTLV infections. Here we provide fundamental information on the simian T lymphotropic virus (STLV) naturally transmitted in a colony of captive baboons. The limited viral sequence heterogeneity in individual baboons,the identity of the viral gene product that is the major target of cellular immune responses,the persistence of viral amino acid sequences that are the major targets of cellular immune responses,and the emergence in vivo of truncated variants in the major target of cellular immune responses all parallel what are seen with HTLV infection of humans. These results justify the use of STLV-infected baboons as a model system for vaccine development efforts. View Publication

A small subset of human cord blood CD34+ cells express endothelial protein C receptor (EPCR/CD201/PROCR) when exposed to the hematopoietic stem cell (HSC) self-renewal agonist UM171. In this article,we show that EPCR-positive UM171-treated cells,as opposed to EPCR-negative cells,exhibit robust multilineage repopulation and serial reconstitution ability in immunocompromised mice. In contrast to other stem cell markers,such as CD38,EPCR expression is maintained when cells are introduced in culture,irrespective of UM171 treatment. Although engineered overexpression of EPCR fails to reproduce the effects of UM171 on HSC activity,its expression is required for the repopulating activity of human HSCs. Altogether,our results indicate that EPCR is a reliable and cell culture-compatible marker of UM171-expanded human cord blood HSCs. View Publication

Background: Local ischemia is the main pathological performance in osteonecrosis of the femoral head (ONFH). There is currently no effective therapy to promote angiogenesis in the femoral head. Recent studies revealed that exosomes secreted by induced pluripotent stem cell-derived mesenchymal stem cells (iPS-MSC-Exos) have great therapeutic potential in ischemic tissues,but whether they could promote angiogenesis in ONFH has not been reported,and little is known regarding the underlying mechanism. Methods: iPS-MSC-Exos were intravenously injected to a steroid-induced rat osteonecrosis model. Samples of the femoral head were obtained 3 weeks after all the injections. The effects were assessed by measuring local angiogenesis and bone loss through histological and immunohistochemical (IHC) staining,micro-CT and three-dimensional microangiography. The effects of exosomes on endothelial cells were studied through evaluations of proliferation,migration and tube-forming analyses. The expression levels of angiogenic related PI3K/Akt signaling pathway of endothelial cells were evaluated following stimulation of iPS-MSC-Exos. The promoting effects of exosomes were re-evaluated following blockade of PI3K/Akt. Results: The in vivo study revealed that administration of iPS-MSC-Exos significantly prevented bone loss,and increased microvessel density in the femoral head compared with control group. We found that iPS-MSC-Exos significantly enhanced the proliferation,migration and tube-forming capacities of endothelial cells in vitro. iPS-MSC-Exos could activate PI3K/Akt signaling pathway in endothelial cells. Moreover,the promoting effects of iPS-MSC-Exos were abolished after blockade of PI3K/Akt on endothelial cells. Conclusions: Our findings suggest that transplantation of iPS-MSC-Exos exerts a preventative effect on ONFH by promoting local angiogenesis and preventing bone loss. The promoting effect might be attributed to activation of the PI3K/Akt signaling pathway on endothelial cells. The data provide the first evidence for the potential of iPS-MSC-Exos in treating ONFH. View Publication

Genetic modification of cell lines and primary cells is an expensive and cumbersome approach,often involving the use of viral vectors. Electroporation using square-wave generating devices,like Lonza's Nucleofector,is a widely used option,but the costs associated with the acquisition of electroporation kits and the transient transgene expression might hamper the utility of this methodology. In the present work,we show that our in-house developed buffers,termed Chicabuffers,can be efficiently used to electroporate cell lines and primary cells from murine and human origin. Using the Nucleofector II device,we electroporated 14 different cell lines and also primary cells,like mesenchymal stem cells and cord blood CD34+,providing optimized protocols for each of them. Moreover,when combined with sleeping beauty-based transposon system,long-term transgene expression could be achieved in all types of cells tested. Transgene expression was stable and did not interfere with CD34+ differentiation to committed progenitors. We also show that these buffers can be used in CRISPR-mediated editing of PDCD1 gene locus in 293T and human peripheral blood mononuclear cells. The optimized protocols reported in this study provide a suitable and cost-effective platform for the genetic modification of cells,facilitating the widespread adoption of this technology. View Publication

Age-related macular degeneration (AMD) affects the retinal pigment epithelium (RPE),a cell monolayer essential for photoreceptor survival,and is the leading cause of vision loss in the elderly. There are no disease-altering therapies for dry AMD,which is characterized by accumulation of subretinal drusen deposits and complement-driven inflammation. We report the derivation of human-induced pluripotent stem cells (hiPSCs) from patients with diagnosed AMD,including two donors with the rare ARMS2/HTRA1 homozygous genotype. The hiPSC-derived RPE cells produce several AMD/drusen-related proteins,and those from the AMD donors show significantly increased complement and inflammatory factors,which are most exaggerated in the ARMS2/HTRA1 lines. Using a panel of AMD biomarkers and candidate drug screening,combined with transcriptome analysis,we discover that nicotinamide (NAM) ameliorated disease-related phenotypes by inhibiting drusen proteins and inflammatory and complement factors while upregulating nucleosome,ribosome,and chromatin-modifying genes. Thus,targeting NAM-regulated pathways is a promising avenue for developing therapeutics to combat AMD. View Publication

Haematopoietic stem cell (HSC) gene therapy has demonstrated potential to treat many diseases. However,current state of the art requires sophisticated ex vivo gene transfer in a dedicated Good Manufacturing Practices facility,limiting availability. An automated process would improve the availability and standardized manufacture of HSC gene therapy. Here,we develop a novel program for semi-automated cell isolation and culture equipment to permit complete benchtop generation of gene-modified CD34+ blood cell products for transplantation. These cell products meet current manufacturing quality standards for both mobilized leukapheresis and bone marrow,and reconstitute human haematopoiesis in immunocompromised mice. Importantly,nonhuman primate autologous gene-modified CD34+ cell products are capable of stable,polyclonal multilineage reconstitution with follow-up of more than 1 year. These data demonstrate proof of concept for point-of-care delivery of HSC gene therapy. Given the many target diseases for gene therapy,there is enormous potential for this approach to treat patients on a global scale. View Publication

Acute myeloid leukemia (AML) is a heterogeneous group of aggressive bone marrow cancers arising from transformed hematopoietic stem and progenitor cells (HSPC). Therapy-related AML and MDS (t-AML/MDS) comprise a subset of AML cases occurring after exposure to alkylating chemotherapy and/or radiation and are associated with a very poor prognosis. Less is known about the pathogenesis and disease-initiating/leukemia stem cell (LSC) subpopulations of t-AML/MDS compared to their de novo counterparts. Here,we report the development of mouse models of t-AML/MDS. First,we modeled alkylator-induced t-AML/MDS by exposing wild type adult mice to N-ethyl-N-nitrosurea (ENU),resulting in several models of AML and MDS that have clinical and pathologic characteristics consistent with human t-AML/MDS including cytopenia,myelodysplasia,and shortened overall survival. These models were limited by their inability to transplant clinically aggressive disease. Second,we established three patient-derived xenograft models of human t-AML. These models led to rapidly fatal disease in recipient immunodeficient xenografted mice. LSC activity was identified in multiple HSPC subpopulations suggesting there is no canonical LSC immunophenotype in human t-AML. Overall,we report several new t-AML/MDS mouse models that could potentially be used to further define disease pathogenesis and test novel therapeutics. View Publication

Gene therapy with genetically modified human CD34(+) hematopoietic stem and progenitor cells (HSPCs) may be safer using targeted integration (TI) of transgenes into a genomic 'safe harbor' site rather than random viral integration. We demonstrate that temporally optimized delivery of zinc finger nuclease mRNA via electroporation and adeno-associated virus (AAV) 6 delivery of donor constructs in human HSPCs approaches clinically relevant levels of TI into the AAVS1 safe harbor locus. Up to 58{\%} Venus(+) HSPCs with 6-16{\%} human cell marking were observed following engraftment into mice. In HSPCs from patients with X-linked chronic granulomatous disease (X-CGD),caused by mutations in the gp91phox subunit of the NADPH oxidase,TI of a gp91phox transgene into AAVS1 resulted in ∼15{\%} gp91phox expression and increased NADPH oxidase activity in ex vivo-derived neutrophils. In mice transplanted with corrected HSPCs,4-11{\%} of human cells in the bone marrow expressed gp91phox. This method for TI into AAVS1 may be broadly applicable to correction of other monogenic diseases. View Publication