Human AB Research Articles

Development of Optimized Protocol for Generation of NK Cells Expressing Chimeric Antigen Receptors from Hematopoietic Stem Cells for Cancer Immunotherapy

Background : Natural Killer (NK) cells are innate immune cells that mediate cytotoxicity against tumor and virus-infected cells, and represent a very promising source for adoptive cellular approaches for cancer immunotherapy. Extensive research has been conducted, including clinical trials, attempting to harness their properties. Gene modification of NK cells can direct their specificity and enhance their function, but the efficiency of gene transfer in mature NK cells is very limited. We have previously published a protocol for generation of human NK cells from gene-modified hematopoietic stem cells (HSC) isolated from umbilical cord blood. Generation of NK cells from HSC provides the opportunity of generation of younger NK cells and expansion of specific gene-modified clones starting from a smaller number of previously isolated and cryopreserved initial cells, with added advantage of generation of multiple batches from the same donor. Chimeric antigen receptors (CAR) are engineered fusion proteins that combine the antigen specificity of antigen-binding moieties of monoclonal antibodies and intracellular activation motifs capable to activate immune cells. Preliminary evidence suggests that NK cells with specificity directed by second-generation CAR may have enhanced cytotoxicity. The goal is to develop a protocol with maximal generation of CAR-expressing NK cells from human HSC for clinical applications. We have evaluated the use of HSC isolated from G-CSF-mobilized apheresed peripheral blood mononuclear cells (PBSC), the elimination of serum in culture media and the elimination of feeder stroma.Significance : Development of a protocol for clinical translation and large-scale good manufacturing practice (GMP) compatibility, maximally generating functional CAR-expressing NK cells. G-CSF mobilized peripheral blood stem cells (PBSC) were used because of availability of larger HSC numbers, increasing safety and efficacy. Changes in culture media based on available literature were evaluated to promote generation of larger number of cells. Human AB serum and serum free media were tested to determine the cell yield for large-scale GMP-compatible protocol.Methods : A third-generation lentiviral vector co-delivering CD19-specific CAR and enhanced green fluorescent protein (EGFP) was used for gene modification of primary human PBSC. Gene-modified cells were then co-cultured with OP9-DL1 stromal cells over 35-40 days in six different culture media conditions for evaluation. Medium "A" was our previously published protocol and consisted of alpha-MEM enriched with 20% of fetal bovine serum and recombinant human cytokines SCF 5ng/mL, Flt3L 5ng/mL, IL-7 5ng/mL, and IL-15 10ng/mL. Medium "B" was AIM V enriched with 10% of human AB serum and cytokines SCF 5ng/mL, Flt3L 5ng/mL, IL-7 20ng/mL, and IL-15 50ng/mL. Medium "C" was similar to medium "B" excluding human AB serum. After 10 days of culture, IL-2 10ng/mL was added to all three media ("plus") creating six different conditions. Flow cytometry was used for detection of EGFP expression and NK cell surface markers. Digital droplet PCR was used for analysis of number of integrated viral copies. Feeder-free culture conditions were developed with the addition of recombinant human IGF-1 100ng/mL to AIM V culture media enriched with SCF, Flt-3 and IL-15.Results : NK cell differentiation was achieved in all conditions. Feeder-free conditions seemed to present mature NK cells earlier (days 25-30) than stromal co-culture (days 35-45), but lower cell yield. As previously reported, PBSC had lower yields of NK differentiation as compared to umbilical cord blood, but higher concentrations of IL-7 and IL-15 rescued the differentiation. Total cell yields were 100-220-fold expansions, with highest counts recovered from conditions with higher IL-7 and IL-15. The removal of serum and addition of IL-2 did not seem to affect differentiation or proliferation. CD56+/CD16+/CD94+ NK cells were present in 10-40% of all CD56+ cells.Conclusions : Large-scale GMP-compatible generation of clinically-relevant numbers of gene-modified NK cells from HSC is feasible. Higher doses of cytokines IL-7 and IL-15 successfully increase the yield of NK cells from PBSC. Absence of serum did not decrease differentiation or proliferation. PBSC showed folds of expansion and NK cell differentiation comparable to those obtained from umbilical cord blood. DisclosuresNo relevant conflicts of interest to declare.

TLR-2 Signal Pathway Is Enhanced in Myeloproliferative Neoplasm - Related to the Increased Infammatory Cytokine and Pathogenesis?

IntroductionMyeloproliferative neoplasms (MPNs) are associated with constitutional symptoms and high levels of circulating inflammatory cytokines. The etiology of this increase in inflammatory cytokines could be secondary to Jak2 mutation resulting in enhanced transduction signaling of cytokines. Toll-like receptors (TLRs) represent another activating mechanism by which their expression on antigen presenting cells, such as dendritic cells (DCs) and macrophages, serve as key pattern recognition receptors (PRR) which play a central role in induction of innate and adaptive immune responses resulting in the signaling of inflammatory cytokines. TNFα is one of the inflammatory cytokine which is significantly raised in MPN patients. Recent evidence suggests that TNFα may facilitate clonal expansion of JAK2 V617F mutation positive cells which leads to hypothesis suggesting that chronic inflammation is involved in the pathogenesis and clonal evolution in Philadelphia-negative chronic MPNs. Therefore, we investigated the role of TLRs and related cytokines in MPNs and we found that only TLR-2 was significantly elevated in MPNs. We further used the TLR-2 ligand, Pam3CSK4, to study its effects on the production inflammatory cytokines.Materials & MethodsTLR assay: TLR-2, 4, 7, 9 quantification was performed by TLR staining of 5×105 mononuclear cells which were incubated with 5 μg/mlof conjugated TLR-2, 4, 7, 9 antibody and assayed by flow cytometry.Monocyte-derived dendritic cells (mdDC) and Inflammatory Cytokines.mdDC were generated from isolated monocytes (anti-CD14-coated magnetic beads) then by incubation with IL-4 and GM-CSF for 4 days. Immature mdDC (1×104/well) were either left untreated or stimulated with Pam3CSK4, in 96 well plates. After 48h, cells were incubated with 20% human AB serum in PBS containing 0.1% BSA and 0.1% NaN3 for 20 min at 4¡C. Thereafter, cells were stained with fluorescence-labeled mAb specific to CD80, CD83, (BD Biosciences). Cytokine levels were determined in supernatants harvested after 48h using the MSD (Meso Scale Discovery) System.Results. Levels ofTLR-2 were significantly elevated in patients with MPNs especially in those with polycythemia vera and essential thrombocythemia, but only marginally elevated in myelofibrosis (MF) patients, which likely may be attributable to the relatively lack in number of MF patients (Fig 1). In all patient subsets, TLR 4, 7, 9 levels were not significantly different from controls as shown in Fig 1. Fig 2 shows maturation of mdDC by TLR-2 ligand, Pam3CSK4. Higher numbers of CD83+ cells were generated more from patients with elevated TLR levels, confirming these MPN patients has elevated TLR2 levels to be able to generated more dendric cells by TLR-2 ligand. Fig 3 a and b shows in elevated TLR-2 level MPN patients, Pam3CSK4 stimulated more cytokins of IFNγ, IL12p70, TNFα, IL6, IL8, IL10, IL13. Fig 4 showed in elevated TLR-2 levels MPN patients have more of IL8, TNFα, IL13, IL6, in the plasma, consistent with inflammatory cytokines likely from elevated elevated TLR-2.Therefore TLR-2 likely plays a very important role in the inflammatory cytokine production in MPN diseases.Conclusion. TLR-2 and not TLR-4, 7, 9 were found to be significantly elevated in MPNs. Stimulation of the TLR-2 ligand promoted the generation of more mature DCs in TLR-2 elevated MPN patients, demonstrating TLR-2 were elevated in these patients. Further, the stimulation of mdDC cultures with TLR2 ligand led to greater cytokine production and the level of plasma cytokines correlated with TLR-2 levels. We conclude that TLR-2 is important in the production of inflammatory cytokines in MPNs and it may play a significant role in the pathogenesis of MPNs. [Display omitted] [Display omitted] [Display omitted] DisclosuresWang:Celgene: Research Funding.

ERK1-Based Pathway as a New Selective Mechanism To Modulate CCR5 with Natural Antibodies.

Natural human Abs, recognizing an epitope within the first extramembrane loop of CCR5 (the main HIV coreceptor), induce a long-lasting internalization (48 h) of the protein, whereas all known CCR5 modulating molecules show a short-term kinetics (60-90 min). Despite extensive studies on the regulation of CCR5 signaling cascades, which are the effect of concomitant CCR5 internalization by exogenous stimuli such as Abs, downstream signaling continues to be poorly understood. In this article, we report a hitherto unrecognized mechanism of CCR5 modulation mediated by G protein-dependent ERK1 activity. We further demonstrate that ERK1 is localized mainly in the cytoplasmic compartment and that it interacts directly with the CCR5 protein, thus provoking possible CCR5 degradation with a subsequent de novo synthesis, and that re-expression of CCR5 on the cell membrane required several days. In contrast, the RANTES treatment induces a recovery of the receptor on the cell membrane in short-term kinetics without the involvement of de novo protein synthesis. The said new pathway could be relevant not only to better understand the molecular basis of all pathologic conditions in which CCR5 is involved but also to generate new tools to block viral infections, such as the use of recombinant Abs.

Prevalence of soluble peptidylarginine deiminase 4 (PAD4) and anti-PAD4 antibodies in autoimmune diseases.

The objectives of this study are to investigate the prevalence of PAD4 and anti-PAD4 antibodies (Abs) in autoimmune diseases and to clarify their association with anticitrullinated protein antibodies (ACPAs) and shared epitope (SE) in patients with rheumatoid arthritis (RA). Levels of human PAD4 and anti-PAD4 Abs in serum or plasma were measured using sandwich ELISA. Samples were obtained from patients with RA (n = 148), SLE (n = 36), or SS (n = 37) and from healthy controls (HCs; n = 40). Antibodies against cyclic citrullinated glucose-6-phosphate isomerase (GPI) (CCG)-2, CCG-7, anti-CEP-1, and anti-CCP Abs were also measured using ELISA. Patients with RA were genotyped for HLA-DRB1. The human PAD4 and anti-PAD4 Ab levels were compared with the ACPA and SE in patients with RA. The PAD4 levels were 111.9U/ml in the RA, 30.4U/ml in the SLE, 81.9U/ml in the SS patients, and 46.6U/ml in the HCs. The PAD4 levels were significantly higher in the RA than in the SLE patients or the HCs. Anti-PAD4 Abs were detected in 29.7% of the patients with RA, but not in the patients with SLE or SS, nor in the HCs. In the RA patients, the PAD4 levels in the anti-PAD4 Ab-negative group were significantly higher than those in the anti-PAD4 Ab-positive group. Moreover, anti-CCG-2, CCG-7, CEP-1, and anti-CCP Ab levels were significantly higher in the anti-PAD4 Ab-positive group than in the anti-PAD4 Ab-negative group. In the RA patients, the PAD4 levels were not correlated with ACPAs. Neither PAD4 nor anti-PAD4 Abs were significantly correlated with the presence of SE alleles. The PAD4 levels were higher in RA than in SLE or HC. Anti-PAD4 Abs appeared specifically in patients with RA. Moreover, anti-PAD4 Abs were associated with ACPAs.

Lamprey VLRB response to influenza virus supports universal rules of immunogenicity and antigenicity.

Immunoglobulins (Igs) are a crown jewel of jawed vertebrate evolution. Through recombination and mutation of small numbers of genes, Igs can specifically recognize a vast variety of natural and man-made organic molecules. Jawless vertebrates evolved a parallel system of humoral immunity, which recognizes antigens not with Ig, but with a structurally unrelated receptor called the variable lymphocyte receptor B (VLRB). We exploited the convergent evolution of Ig and VLRB antibodies (Abs) to investigate if intrinsic chemical features of foreign proteins determine their antigenicity and immunogenicity. Surprisingly, we find lamprey VLRB and mouse Ig responses to influenza A virus are extremely similar. Each focuses ~80% of the response on hemagglutinin (HA), mainly through recognition of the major antigenic sites in the HA globular head domain. Our findings predict basic conservation of Ab responses to protein antigens, strongly supporting the use of animal models for understanding human Ab responses to viruses and protein immunogens.

Abstract 266: Antitumor activity of REGN2810, a fully human anti-PD-1 monoclonal antibody, against MC38.Ova tumors grown in immune-competent humanized PD-1 mice

Abstract Programmed Cell Death Protein 1 (PD-1), is an inhibitory checkpoint receptor, expressed in an activation-induced manner on T cells. PD-1 signals upon binding to its ligands PD-L1 and PD-L2, expressed on APCs and some types of cancer cells, and delivers inhibitory signals to T cells, promoting T-cells functional exhaustion in a tumor microenvironment. Clinically, antibodies (Abs) that block the interaction between PD-1 and PD-L1 can release the cytotoxic function of tumor-specific T cells, yielding durable objective responses in multiple cancer types. REGN2810 is a fully human hinge-stabilized IgG4P monoclonal Ab that binds to the extracellular domain of human PD-1 with high affinity and specificity. REGN2810 was selected using a combination of binding studies (Surface Plasmon Resonance [SPR]-Biacore), enzyme-linked immunosorbent assays (ELISA), novel engineered cell-based bioassays, and preclinical studies in mouse models. REGN2810 was investigated in PD-1 humanized mice, an approach that allows direct testing of clinical PD-1 Ab that does not cross-react with mouse PD-1. Humanized PD-1 mice were created by Velocigene technology to express a humanized hybrid PD-1 protein comprising the extracellular portion of human PD-1 and the transmembrane and intracellular portion of mouse PD-1. Humanized PD-1 mice were validated for inducible cell surface expression of hybrid PD-1 protein on activated T-cells, intact PD-1/PD-L1 signaling and immune responses. A weakly immunogenic murine colorectal cancer cell line MC38 was engineered to express ovalbumin (MC38.Ova) in order to increase tumor immunogenicity and allow monitoring of T-cell immune responses to well-defined antigenic ovalbumin peptides. Prophylactic treatment with REGN2810 PD-1 Ab significantly suppressed growth of subcutaneous syngeneic MC38.Ova tumors in humanized PD-1 mice in a dose dependent manner, and improved mouse survival. Therapeutic treatment with REGN2810 also promoted dose dependent regression of established MC38.Ova tumors in humanized PD-1 mice. Treatment with REGN2810 induced CD8 T cells proliferation and cytokine production in spleens of tumor bearing huPD-1 mice. The mechanism of action and robust anti-tumor efficacy of REGN2810 support its clinical development for the treatment of human cancers. Citation Format: Elena Burova, Omaira Allbritton, William Poueymirou, Venus Lai, Janelle White, Dimitris Skokos, Nicholas Papadopoulos, Drew Murphy, Israel Lowy, Ella Ioffe, Gavin Thurston. Antitumor activity of REGN2810, a fully human anti-PD-1 monoclonal antibody, against MC38.Ova tumors grown in immune-competent humanized PD-1 mice. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 266. doi:10.1158/1538-7445.AM2015-266

Effect of TNF-alpha blockade on coagulopathy and endothelial cell activation in xenoperfused porcine kidneys.

Following pig-to-primate kidney transplantation, endothelial cell activation and xenogenic activation of the recipient's coagulation eventually leading to organ dysfunction and microthrombosis can be observed. In this study, we examined the effect of a TNF-receptor fusion protein (TNF-RFP) on endothelial cell activation and coagulopathy utilizing an appropriate ex vivo perfusion system. Using an ex vivo perfusion circuit based on C1-Inhibitor (C1-Inh) and low-dose heparin administration, we have analyzed consumptive coagulopathy following contact of human blood with porcine endothelium. Porcine kidneys were recovered following in situ cold perfusion with Histidine-tryptophan-ketoglutarate (HTK) organ preservation solution and were immediately connected to a perfusion circuit utilizing freshly drawn pooled porcine or human AB blood. The experiments were performed in three individual groups: autologous perfusion (n = 5), xenogenic perfusion without any further pharmacological intervention (n = 10), or with addition of TNF-RFP (n = 5). After perfusion, tissue samples were obtained for real-time PCR and immunohistological analyses. Endothelial cell activation was assessed by measuring the expression levels of E-selectin, ICAM-1, and VCAM-1. Kidney survival during organ perfusion with human blood, C1-Inh, and heparin, but without any further pharmacological intervention was 126 ± 78 min. Coagulopathy was observed with significantly elevated concentrations of D-dimer and thrombin-antithrombin complex (TAT), resulting in the formation of multiple microthrombi. Endothelial cell activation was pronounced, as shown by increased expression of E-selectin and VCAM-1. In contrast, pharmacological intervention with TNF-RFP prolonged organ survival to 240 ± 0 min (max. perfusion time; no difference to autologous control). Formation of microthrombi was slightly reduced, although not significantly, if compared to the xenogenic control. D-dimer and TAT were elevated at similar levels to the xenogenic control experiments. In contrast, endothelial cell activation, as shown by real-time PCR, was significantly reduced in the TNF-RFP group. We conclude that although coagulopathy was not affected, TNF-RFP is able to suppress inflammation occurring after xenoperfusion in this ex vivo perfusion model.

Recovery of a human natural antibody against the noncollagenous-1 domain of type IV collagen using humanized models.

BackgroundAnti-glomerular basement membrane nephritis and Goodpasture syndrome result from autoantibody (Ab)-mediated destruction of kidney and lung. Ab target the noncollagenous 1 (NC1) domain of alpha3(IV) collagen, but little is known about Ab origins or structure. This ignorance is due in part to the inability to recover monoclonal Ab by transformation of patients’ blood cells. The aim of this study was to assess the suitability of two humanized models for this purpose.MethodsNOD-scid-gamma immunodeficient mice were engrafted either with human CD34+ hematopoietic stem cells (HSC) (Hu-HSC mice) and immunized with alpha3(IV)NC1 collagen containing the Goodpasture epitopes or with nephritis patients’ peripheral blood leukocytes (PBL) (Hu-PBL mice). After in vivo immune cell development and/or expansion, recovered human B cells were Epstein Barr virus (EBV)-transformed, screened for antigen (Ag) binding, electrofused with a mouse–human heterohybridoma, subcloned, and human Ab RNA sequenced by PCR after reverse transcription to cDNA. Flow cytometry was used to assess human B cell markers and differentiation in Hu-PBL mice.ResultsSequence analysis of a human Ab derived from an immunized Hu-HSC mouse and reactive with alpha3(IV)NC1 collagen reveals that it is encoded by unmutated heavy and light chain genes. The heavy chain complementarity determining region 3, a major determinant of Ag binding, contains uncommon motifs, including an N-region somatically-introduced highly hydrophobic tetrapeptide and dual cysteines encoded by a uniquely human IGHD2-2 Ab gene segment that lacks a murine counterpart. Comparison of human and mouse autoantibodies suggests that structurally similar murine Ab may arise by convergent selection. In contrast to the Hu-HSC model, transformed human B cells are rarely recovered from Hu-PBL mice, in which human B cells terminally differentiate and lose expression of EBV receptor CD21, thus precluding their transformation and recovery.ConclusionsHu-HSC mice reveal that potentially pathogenic B cells bearing unmutated Ig receptors reactive with the NC1 domain on alpha3(IV) collagen can be generated in, and not purged from, the human preimmune repertoire. Uniquely human gene elements are recruited to generate the antigen binding site in at least a subset of these autoantibodies, indicating that humanized models may provide insights inaccessible using conventional mouse models.Electronic supplementary materialThe online version of this article (doi:10.1186/s12967-015-0539-4) contains supplementary material, which is available to authorized users.

A broad range of mutations in HIV-1 neutralizing human monoclonal antibodies specific for V2, V3, and the CD4 binding site

The HIV vaccine-induced neutralizing antibodies (Abs) display low rates of mutation in their variable regions. To determine the range of neutralization mediated by similar human monoclonal Abs (mAbs) but derived from unselected chronically HIV-1 infected subjects, we tested a panel of 66 mAbs specific to V3, CD4 binding site (CD4bs) and V2 regions. The mAbs were tested against 41 pseudoviruses, including 15 tier 1 and 26 tier 2, 3 viruses, showing that the neutralization potency and breadth of anti-V3 mAbs were significantly higher than those of the anti-CD4bs and anti-V2 mAbs, and only anti-V3 mAbs were able to neutralize some tier 2, 3 viruses. The percentage of mutations in the variable regions of the heavy (VH) and light (VL) chains varied broadly in a range from 2% to 18% and correlated moderately with the neutralization breadth of tier 2, 3 viruses. There was no correlation with neutralization of tier 1 viruses as some mAbs with low and high percentages of mutations neutralized the same number of viruses. The electrostatic interactions between anti-V3 mAbs and the charged V3 region may contribute to their neutralization because the isoelectric points of the VH CDR3 of 48 anti-V3 mAbs were inversely correlated with the neutralization breadth of tier 2, 3 viruses. The results demonstrate that infection-induced antibodies to CD4bs, V3 and V2 regions can mediate cross-clade neutralization despite low levels of mutations which can be achieved by HIV-1 vaccine-induced antibodies.

A unique mouse strain that develops spontaneous, iodine-accelerated, pathogenic antibodies to the human thyrotrophin receptor.

Abs that stimulate the thyrotropin receptor (TSHR), the cause of Graves' hyperthyroidism, only develop in humans. TSHR Abs can be induced in mice by immunization, but studying pathogenesis and therapeutic intervention requires a model without immunization. Spontaneous, iodine-accelerated, thyroid autoimmunity develops in NOD.H2(h4) mice associated with thyroglobulin and thyroid-peroxidase, but not TSHR, Abs. We hypothesized that transferring the human TSHR A-subunit to NOD.H2(h4) mice would result in loss of tolerance to this protein. BALB/c human TSHR A-subunit mice were bred to NOD.H2(h4) mice, and transgenic offspring were repeatedly backcrossed to NOD.H2(h4) mice. All offspring developed Abs to thyroglobulin and thyroid-peroxidase. However, only TSHR-transgenic NOD.H2(h4) mice (TSHR/NOD.H2(h4)) developed pathogenic TSHR Abs as detected using clinical Graves' disease assays. As in humans, TSHR/NOD.H2(h4) female mice were more prone than male mice to developing pathogenic TSHR Abs. Fortunately, in view of the confounding effect of excess thyroid hormone on immune responses, spontaneously arising pathogenic human TSHR Abs cross-react poorly with the mouse TSHR and do not cause thyrotoxicosis. In summary, the TSHR/NOD.H2(h4) mouse strain develops spontaneous, iodine-accelerated, pathogenic TSHR Abs in female mice, providing a unique model to investigate disease pathogenesis and test novel TSHR Ag-specific immunotherapies aimed at curing Graves' disease in humans.

Human antibody specificities that confer protective immunity to poxvirus infections (VAC11P.1109)

Abstract Immunization with vaccinia virus (VACV) induces cross-protective immunity to variola, the causative agent of smallpox, and other clinically important poxviral species, such as cowpox and monkeypox viruses. Vaccine-mediated protection has been correlated with elicitation of broad neutralizing antibodies (Abs). However, the specificity and breadth of protective human Abs to poxviruses are largely unknown. We used a highly-optimized human hybridoma technology to generate a panel of 90 anti-VACV monoclonal Abs from vaccinia-immunized subjects or from subjects who had a history of naturally-acquired monkeypox infection. Then, we assessed the neutralizing and protective capabilities of the Abs in vitro and in a lethal respiratory VACV challenge in a mouse model. A large fraction of Abs from the panel (>40%) possessed neutralizing activity against VACV, cowpox and/or monkeypox viruses. Antibodies to a variety of envelope proteins in VACV extracellular virions (A33, B5) or mature virions (L1, A27, D8, H3) contributed substantially to neutralizing activity in vitro. For protective immunity in vivo, L1, A27, A33 and B5 antibodies conferred levels of protection that were comparable to those induced by live viral vaccination, especially when used in combination. Such antibody cocktails have promise for use in as immunotherapeutics in humans.

Promiscuous T-cell responses to drugs and drug-haptens

Promiscuous T-cell responses to drugs and drug-haptens

Predominant development of mature and functional human NK cells in a novel human IL-2-producing transgenic NOG mouse.

We generated a severe immunodeficient NOD/Shi-scid-IL-2Rγ(null) (NOG) mouse substrain expressing the transgenic human IL-2 gene (NOG-IL-2 Tg). Upon transfer of human cord blood-derived hematopoietic stem cells (HSCs), CD3(-)CD56(high)CD16(+/-) cells developed unexpectedly, predominantly in the NOG-IL-2 Tg (hu-HSC NOG-IL-2 Tg). These cells expressed various NK receptors, including NKp30, NKp44, NKp46, NKG2D, and CD94, as well as a diverse set of killer cell Ig-like receptor molecules at levels comparable to normal human NK cells from the peripheral blood, which is evidence of their maturity. They produced levels of granzyme A as high as in human peripheral blood-derived NK cells, and a considerable amount of perforin protein was detected in the plasma. Human NK cells in hu-HSC NOG-IL-2 Tg produced IFN-γ upon stimulation, and IL-2, IL-15, or IL-12 treatment augmented the in vitro cytotoxicity. Inoculation of K562 leukemia cells into hu-HSC NOG-IL-2 Tg caused complete rejection of the tumor cells, whereas inoculation into hu-HSC NOG fully reconstituted with human B, T, and some NK cells did not. Moreover, when a CCR4(+) Hodgkin's lymphoma cell line was inoculated s.c. into hu-HSC NOG-IL-2 Tg, the tumor growth was significantly suppressed by treatment with a therapeutic humanized anti-CCR4 Ab (mogamulizumab), suggesting that the human NK cells in the mice exerted active Ab-dependent cellular cytotoxicity in vivo. Taken together, these data suggest that the new NOG-IL-2 Tg strain is a unique model that can be used to investigate the biological and pathological functions of human NK cells in vivo.

Engineering more efficient multipotent mesenchymal stromal (stem) cells for systemic delivery as cellular therapy

Multipotent mesenchymal stromal (stem) cells (MSCs) harbour great potential for regenerative and immunomodulatory therapies. A major drawback in MSC therapy appears to be the incomplete understanding of cell fate and function following systemic administration. We here summarize our knowledge on MSC interaction with human blood. Analysis of tissues following MSC therapy indicated limited long‐term engraftment. MSCs and other stromal cells trigger an innate immune attack, termed instant blood‐mediated inflammatory reaction (IBMIR), which has been shown to compromise the survival, engraftment and function of cellular therapeutics. MSCs express hemostatic regulators similar to those produced by endothelial cells, but display higher amounts of prothrombotic tissue factor on their surface, which triggers the IBMIR after blood exposure. This process is dependent on the cell dose, the choice of MSC donor, the cell passage number and cell handling before infusion. Freshly harvested, short‐term expanded bone marrow MSCs trigger only weak blood responses, while extended culture, freeze‐thawing, washing and resupsension in human AB plasma, and co‐culture with activated lymphocytes increases their prothrombotic profile. After MSC infusion to patients, we found increased formation of blood activation markers, but no formation of hyperfibrinolysis marker D‐dimer or acute phase reactants with the currently applied dose of 1–3 × 106 cells/kg, demonstrating product safety. We conclude, that currently applied doses of low‐passage clinical grade MSCs are safe and elicit only minor systemic effects, but higher cell doses, and particularly higher passage cells, should be handled with care. This deleterious reaction can compromise the survival, engraftment and function of these therapeutic cells.

High-density IgE recognition of the major grass pollen allergen Phl p 1 revealed with single-chain IgE antibody fragments obtained by combinatorial cloning.

The timothy grass pollen allergen Phl p 1 belongs to the group 1 of highly cross-reactive grass pollen allergens with a molecular mass of ∼25-30 kDa. Group 1 allergens are recognized by >95% of grass pollen allergic patients. We investigated the IgE recognition of Phl p 1 using allergen-specific IgE-derived single-chain variable Ab fragments (IgE-ScFvs) isolated from a combinatorial library constructed from PBMCs of a grass pollen-allergic patient. IgE-ScFvs reacted with recombinant Phl p 1 and natural group 1 grass pollen allergens. Using synthetic Phl p 1-derived peptides, the binding sites of two ScFvs were mapped to the N terminus of the allergen. In surface plasmon resonance experiments they showed comparable high-affinity binding to Phl p 1 as a complete human IgE-derived Ab recognizing the allergens' C terminus. In a set of surface plasmon resonance experiments simultaneous allergen recognition of all three binders was demonstrated. Even in the presence of the three binders, allergic patients' polyclonal IgE reacted with Phl p 1, indicating high-density IgE recognition of the Phl p 1 allergen. Our results show that multiple IgE Abs can bind with high density to Phl p 1, which may explain the high allergenic activity and sensitizing capacity of this allergen.

Co-transplantation of human fetal thymus, bone and CD34+ cells into young adult immunodeficient NOD/SCID IL2Rγnull mice optimizes humanized mice that mount adaptive antibody responses

Both the thymus (T) and bone (B) are necessary hematopoietic niches in adult humans. We previously showed that co-transplantation of human fetal T and B tissues into neonatal immunodeficient NOD/SCID IL2Rγnull (NSG, N) mice facilitated hematopoiesis. However, transplantation into neonatal mice resulted in high frequency of early death, making it unrealistic for repetitive experiments. In this study, young adult N mice were pre-engrafted with T and B, T alone, B alone or no tissues. The animals were irradiated and injected with autologous fetal liver (FL)-derived CD34+ cells (34). The resultant mice were TB34N, T34N, B34N and 34N, respectively, and challenged with T cell dependent antigens (Ags). The humanized TB34N mice showed best performance of these mouse models in many aspects resembling the adult human Ag-experienced spleen. The TB34N mice exhibited better hematopoietic reconstitution; balanced development of T- and B-cell, and common progenitor cells; follicular lymphoid structures with a functional germinal center (GC) enriched with follicular dendritic cells (FDCs) and plasma cells (PCs); secretion of hIgG in the sera in response to Ags at comparable levels to those of human; derivations of hIgG mAb-secreting hybridoma clones. Collectively, the humanized TB34N mice could develop an adaptive immunity that was capable of producing Ag-specific hIgG at a significant level via class switching. This unprecedented TB34N platform in humanized mice would be useful in dissecting human immunity, for generating human Abs and clinical applications.

The S228P Mutation Prevents in Vivo and in Vitro IgG4 Fab-arm Exchange as Demonstrated using a Combination of Novel Quantitative Immunoassays and Physiological Matrix Preparation

Human immunoglobulin G isotype 4 (IgG4) antibodies (Abs) are potential candidates for immunotherapy when reduced effector functions are desirable. IgG4 Abs are dynamic molecules able to undergo a process known as Fab arm exchange (FAE). This results in functionally monovalent, bispecific antibodies (bsAbs) with unknown specificity and hence, potentially, reduced therapeutic efficacy. IgG4 FAE is suggested to be an important biological mechanism that provides the basis for the anti-inflammatory activity attributed to IgG4 Abs. To date, the mechanism of FAE is not entirely understood and studies measuring FAE in ex vivo matrices have been hampered by the presence and abundance of endogenous IgG4 wild-type (WT) Abs. Using representative humanized WT IgG4 monoclonal Abs, namely, anti-IL-6 and anti-TNF, and a core-hinge stabilized serine 228 to proline (S228P) anti-IL-6 IgG4 mutant, it is demonstrated for the first time how anti-IgG4 affinity chromatography can be used to prepare physiologically relevant matrices for assessing and quantifying FAE. A novel method for quantifying FAE using a single MSD immunoassay is also reported and confirms previous findings that, dependent on the redox conditions, the S228P mutation can prevent IgG4 FAE to undetectable levels both in vitro and in vivo. Together, the findings and novel methodologies will allow researchers to monitor and quantify FAE of their own IgG4 molecules in physiologically relevant matrices.

A second stimulus required for enhanced antifungal activity of human neutrophils in blood is provided by anaphylatoxin C5a.

Polymorphonuclear neutrophilic granulocytes (PMN) as cellular components of innate immunity play a crucial role in the defense against systemic Candida albicans infection. To analyze stimuli that are required for PMN activity during C. albicans infection in a situation similar to in vivo, we used a human whole-blood infection model. In this model, PMN activation 10 min after C. albicans infection was largely dependent on the anaphylatoxin C5a. Most importantly, C5a enabled blood PMN to overcome filament-restricted recognition of C. albicans and allowed efficient elimination of nonfilamentous C. albicans cph1Δ/efg1Δ from blood. Major PMN effector mechanisms, including oxidative burst, release of secondary granule contents and initial fungal phagocytosis could be prevented by blocking C5a receptor signaling. Identical effects were achieved using a humanized Ab specifically targeting human C5a. Phagocytosis of C. albicans 10 min postinfection was mediated by C5a-dependent enhancement of CD11b surface expression on PMN, thus establishing the C5a-C5aR-CD11b axis as a major modulator of early anti-Candida immune responses in human blood. In contrast, phagocytosis of C. albicans by PMN 60 min postinfection occurred almost independently of C5a and mainly contributed to activation of phagocytically active PMN at later time points. Our results show that C5a is a critical mediator in human blood during C. albicans infection.

Sialylation of N-linked glycans influences the immunomodulatory effects of IgM on T cells.

Human serum IgM Abs are composed of heavily glycosylated polymers with five glycosylation sites on the μ (heavy) chain and one glycosylation site on the J chain. In contrast to IgG glycans, which are vital for a number of biological functions, virtually nothing is known about structure-function relationships of IgM glycans. Natural IgM is the earliest Ig produced and recognizes multiple Ags with low affinity, whereas immune IgM is induced by Ag exposure and is characterized by a higher Ag specificity. Natural anti-lymphocyte IgM is present in the serum of healthy individuals and increases in inflammatory conditions. It is able to inhibit T cell activation, but the underlying molecular mechanism is not understood. In this study, to our knowledge, we show for the first time that sialylated N-linked glycans induce the internalization of IgM by T cells, which in turn causes severe inhibition of T cell responses. The absence of sialic acid residues abolishes these inhibitory activities, showing a key role of sialylated N-glycans in inducing the IgM-mediated immune suppression.

The Role of Hepatitis B Core Antibody Testing in Improving Blood Safety in Resource-Limited Countries Study on Voluntary Blood Donors Fayoum, Egypt

Background: Transmission of hepatitis B virus (HBV) via hepatitis B surface antigen (HBsAg) negative blood donors has been reported. HBsAg is still the only mandatory HBV screening test of blood donors in Egypt due to high cost of DNA testing of all collected blood. Many resource- limited countries have implemented screening antibodies to hepatitis B core antigen (anti-HBc) to further improve transfusion safety. The objective of study was to evaluate the significance of screening to reduce the risk of transfusion transmitted HBV infection in Egypt. Study Design and Methods: The study was conducted on 800 voluntary blood donors negative for HBsAg, hepatitis C antibody (HCVAb) and human immunodeficiency virus Ab. They were subjected to screening for anti- HBV core antibodies (total). Anti-HBc-positive samples were further tested for the antibodies to HBsAg (anti-HBs), and anti-HBc alone sera were tested for HBV DNA. Results: Among 800 healthy voluntary donors, 99 (12.37%) were anti-HBc-positive including 78 anti-HBs positive. The remaining 21 donors were alone, 2 of which (9.52%) were HBV DNA-positive. Conclusion: Greater consideration should be given to the implementation of as an additional screening test for blood donors in Egypt as the most cost-effective measure for further improvement of transfusion safety.