89Zr-ImmunoPET shows therapeutic efficacy of anti-CD20 interferon-α fusion protein in a murine B-cell lymphoma model

Antibody-mediated tumor delivery of cytokines can overcome limitations of systemic administration (toxicity, short half-lives). Previous work showed improved anti-tumor potency of anti-CD20-interferon alpha (IFNα) fusion proteins in preclinical mouse models of B-cell lymphoma. Although tumor targeting is mediated by the antibody part of the fusion protein, the cytokine component might strongly influence biodistribution and pharmacokinetics, as a result of its affinity, size, valency and receptor distribution. Here, we used positron emission tomography (immunoPET) to study the in vivo biodistribution and tumor targeting of the anti-CD20 rituximab-murine IFNα1 fusion protein (Rit-mIFNα) and compared it to the parental mAb (rituximab, Rit). Rit-mIFNα and Rit were radiolabeled with zirconium-89 (89Zr, t1/2 78.4 h) and injected into C3H mice bearing syngeneic B-cell lymphomas (38C13-hCD20). Dynamic (2 h p.i.) and static (4, 24 and 72 h) PET scans were acquired. Ex vivo biodistribution was performed after the final scan. Both 89Zr-Rit-mIFNα and 89Zr-Rit specifically target hCD20-expressing B-cell lymphoma in vivo. 89Zr-Rit-mIFNα showed specific uptake in tumors (7.6 {plus minus} 1.0 %ID/g at 75 h p.i.), which was significantly lower than 89Zr-Rit (38.4 {plus minus} 9.9 %ID/g, p<0.0001). ImmunoPET studies also revealed differences in the biodistribution, 89Zr-Rit-mIFNα showed rapid blood clearance and high accumulation in the liver compared with 89Zr-Rit. Importantly, immunoPET clearly revealed a therapeutic effect of the single 89Zr-Rit-mIFNα dose, resulting in smaller tumors and fewer lymph node metastases compared to mice receiving 89Zr-Rit. Mice receiving 89Zr-Rit-mIFNα had enlarged spleens, suggesting that systemic immune activation contributes to therapeutic efficacy in addition to the direct antitumoral activity of IFNα. In conclusion, immunoPET allows the non-invasive tracking and quantification of the antibody-cytokine fusion protein and helps understand the in vivo behavior and therapeutic efficacy.

Abstract 1726: Preclinical evaluation of a novel tumor selectively targeted and activated immunocytokine platform

Interferon alpha (IFNα) is a potent cytokine with receptors expressed universally on virtually all cells types. Recombinant versions of IFNα have demonstrated efficacy in multiple tumor indications and have been FDA approved for treatment of various cancers. However, the full anti-tumor potential of IFNα is not realized with these therapies due to dose limiting toxicity, primarily represented by severe flu-like symptoms resulting from systemic activation of immune cells. Antibody-cytokine fusion proteins have been evaluated as an approach to enhance tumor delivery of the cytokine and thereby increase the therapeutic window. While this approach has merit and can increase the efficacy of such constructs, it typically does not reduce the systemic toxicity since the cytokine is still free to interact with its receptor in circulation. We have designed a novel fusion protein in which the IFNα is active only after it has entered the tumor environment, thereby preventing toxicity resulting from systemic activation of IFNα receptors. Direct antitumor efficacy of an anti-CD138-IFNα2 fusion protein with a tumor selectively cleaved peptide mask was seen in models of multiple myeloma and ovarian cancer. The mask was also shown to prevent IFN mediated activation of peripheral blood cells.

Citation Format: Kham R. Trinh, Alex Vasuthaswat, George Ayoub, Sherie L. Morrison, David R. Stover. Preclinical evaluation of a novel tumor selectively targeted and activated immunocytokine platform [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2021; 2021 Apr 10-15 and May 17-21. Philadelphia (PA): AACR; Cancer Res 2021;81(13_Suppl):Abstract nr 1726.

Activity of Anti-CD19 Chimeric Antigen Receptor T Cells Against B Cell Lymphoma Is Enhanced by Antibody-Targeted Interferon-Alpha

An important emerging form of immunotherapy targeting B cell malignancies is chimeric antigen receptor (CAR) T cell therapy. Despite encouraging response rates of anti-CD19 CAR T cell therapy in B cell lymphomas, limited durability of response necessitates further study to potentiate CAR T cell efficacy. Antibody-targeted interferon (IFN) therapy is a novel approach in immunotherapy. Given the ability of IFNs to promote T cell activation and survival, target cell recognition, and cytotoxicity, we asked whether antibody-targeted IFN could enhance the antitumor effects of anti-CD19 CAR T cells. We produced an anti-CD20-IFN fusion protein containing the potent type 1 IFN isoform alpha14 (α14), and demonstrated its ability to suppress proliferation and induce apoptosis of human B cell lymphomas. Indeed, with the combination of anti-CD20-hIFNα14 and CAR T cells, we found enhanced cell killing among B cell lymphoma lines. Importantly, for all cell lines pretreated with anti-CD20-hIFNα14, the subsequent cytokine production by CAR T cells was markedly increased regardless of the degree of cell killing. Thus, several activities of CD19 CAR T cells were enhanced in the presence of anti-CD20-hIFNα14. These data suggest that antibody-targeted IFN may be an important novel approach to improving the efficacy of CAR T cell therapy.

Plasma Cells Are Obligate Effectors of Enhanced Myelopoiesis in Aging Bone Marrow

Aging results in increased myelopoiesis, which is linked to the increased incidence of myeloid leukemias and production of myeloid-derived suppressor cells. Here, we examined the contribution of plasma cells (PCs) to age-related increases in myelopoiesis, as PCs exhibit immune regulatory function and sequester in bone marrow (BM). PC number was increased in old BM, and they exhibited high expression of genes encoding inflammatory cytokines and pathogen sensors. Antibody-mediated depletion of PCs from old mice reduced the number of myeloid-biased hematopoietic stem cells and mature myeloid cells to levels in young animals, but lymphopoiesis was not rejuvenated, indicating that redundant mechanisms inhibit that process. PCs also regulated the production of inflammatory factors from BM stromal cells, and disruption of the PC-stromal cell circuitry with inhibitors of the cytokines IL-1 and TNF-α attenuated myelopoiesis in old mice. Thus, the age-related increase in myelopoiesis is driven by an inflammatory network orchestrated by PCs.

Plasma cells are obligate enhancers of age-associated myeloid skewing

In humans and mice, aging results in significantly elevated myelopoiesis and the increased production of inflammatory cytokines with age is thought to underlie this phenomenon. The observation that treatment of young mice with factors such as interleukin (IL)-1 can skew hematopoiesis towards myeloid development is consistent with this hypothesis. However, the cellular source(s) of inflammatory cytokines in the aging bone marrow has not been fully defined. We observed that plasma cells (PCs) accumulate in the bone marrow with age and acquire an inflammatory gene signature. Furthermore, we observed that their depletion in vivo using anti-CD138 antibodies resulted in a significant decline in myelopoiesis as demonstrated by a reduction in the number of myeloid biased hematopoietic stem cells, myeloid progenitors and mature myeloid cells. We also found that anti-CD138 treated mice exhibited reduced expression of genes encoding inflammatory cytokines in bone marrow stromal cells, indicating that plasma cells can regulate inflammatory cytokine production by other microenvironmental components. We tested whether this inflammatory network was necessary to drive age-associated myeloid skewing by treating old mice with Anakinra or Enbrel to abrogate IL-1 and tumor necrosis factor alpha (TNF-α) signaling, respectively. Concurrent blockade of both signaling pathways in old mice resulted in the significant reduction of bone marrow myelopoiesis, which was not observed upon inhibition of either pathway alone. These data demonstrate a previously unappreciated ability of inflammatory PCs to stimulate myelopoiesis and implicate them at the center of an inflammatory regulatory network in the aging bone marrow.

An HK2 Antisense Oligonucleotide Induces Synthetic Lethality in HK1-HK2+ Multiple Myeloma

Although the majority of adult tissues express only hexokinase 1 (HK1) for glycolysis, most cancers express hexokinase 2 (HK2) and many coexpress HK1 and HK2. In contrast to HK1⁺HK2⁺ cancers, HK1^-HK2⁺ cancer subsets are sensitive to cytostasis induced by HK2^shRNA knockdown and are also sensitive to synthetic lethality in response to the combination of HK2^shRNA knockdown, an oxidative phosphorylation (OXPHOS) inhibitor diphenyleneiodonium (DPI), and a fatty acid oxidation (FAO) inhibitor perhexiline (PER). The majority of human multiple myeloma cell lines are HK1^-HK2⁺. Here we describe an antisense oligonucleotide (ASO) directed against human HK2 (HK2-ASO1), which suppressed HK2 expression in human multiple myeloma cell cultures and human multiple myeloma mouse xenograft models. The HK2-ASO1/DPI/PER triple-combination achieved synthetic lethality in multiple myeloma cells in culture and prevented HK1^-HK2⁺ multiple myeloma tumor xenograft progression. DPI was replaceable by the FDA-approved OXPHOS inhibitor metformin (MET), both for synthetic lethality in culture and for inhibition of tumor xenograft progression. In addition, we used an ASO targeting murine HK2 (mHK2-ASO1) to validate the safety of mHK2-ASO1/MET/PER combination therapy in mice bearing murine multiple myeloma tumors. HK2-ASO1 is the first agent that shows selective HK2 inhibition and therapeutic efficacy in cell culture and in animal models, supporting clinical development of this synthetically lethal combination as a therapy for HK1^-HK2⁺ multiple myeloma. SIGNIFICANCE: A first-in-class HK2 antisense oligonucleotide suppresses HK2 expression in cell culture and in in vivo, presenting an effective, tolerated combination therapy for preventing progression of HK1^-HK2⁺ multiple myeloma tumors. GRAPHICAL ABSTRACT: http://cancerres.aacrjournals.org/content/canres/79/10/2748/F1.large.jpg.

Long-lived plasma cells regulate patterns of hematopoiesis in aging

In both humans and mice, aging results in significant alterations to the patterns of bone marrow hematopoiesis. This is highlighted by a precipitous reduction in B lymphopoiesis while myelopoiesis is enhanced. Treatment of young mice with factors such as GM-CSF or IL-1 can skew hematopoiesis towards myeloid development. This suggests that imbalances in the relative concentrations of various cytokines such as inflammatory mediators, whose production is thought to increase with age, could contribute to suppressed lymphoid and enhanced myeloid development in aging. In this case, the resulting stimulation of myelopoiesis would dominate the limited number of niches in the bone marrow environment at the expense of lymphopoiesis. However, whether the age-related decline in lymphopoiesis and increase in myelopoiesis are linked or represent distinct processes is not known. We observed that long-lived plasma cells from old mice acquire an inflammatory gene signature and accumulate in the bone marrow. Addition of long-lived plasma cells to long-term in vitro cultures demonstrated the ability of these cells to promote granulopoiesis from hematopoietic stem cells as well as myeloid progenitors. However, while depletion of long-lived plasma cells in old mice by injection of anti-CD138 antibodies resulted in a significant reduction in myeloid development, B lymphopoiesis remained suppressed. These data demonstrate a previously unappreciated ability of inflammatory plasma cells to stimulate myelopoiesis and provide evidence that, in the context of aging, enhanced myelopoiesis and depressed lymphopoiesis are distinct, independently regulated processes.

Publisher Correction: Elastomeric sensor surfaces for high-throughput single-cell force cytometry

In the version of this Article originally published, in Fig. 1a, all cells in the top schematic were missing, and in the bottom-left schematic showing multiple pattern shapes, two cells were missing in the bottom-right corner. This figure has now been updated in all versions of the Article.

Elastomeric sensor surfaces for high-throughput single-cell force cytometry

As cells with aberrant force-generating phenotypes can directly lead to disease, cellular force-generation mechanisms are high-value targets for new therapies. Here, we show that single-cell force sensors embedded in elastomers enable single-cell force measurements with ~100-fold improvement in throughput than was previously possible. The microtechnology is scalable and seamlessly integrates with the multi-well plate format, enabling highly parallelized time-course studies. In this regard, we show that airway smooth muscle cells isolated from fatally asthmatic patients have innately greater and faster force-generation capacity in response to stimulation than healthy control cells. By simultaneously tracing agonist-induced calcium flux and contractility in the same cell, we show that the calcium level is ultimately a poor quantitative predictor of cellular force generation. Finally, by quantifying phagocytic forces in thousands of individual human macrophages, we show that force initiation is a digital response (rather than a proportional one) to the proper immunogen. By combining mechanobiology at the single-cell level with high-throughput capabilities, this microtechnology can support drug-discovery efforts for clinical conditions associated with aberrant cellular force generation.

Anti-VEGFR2-interferon-α2 regulates the tumor microenvironment and exhibits potent antitumor efficacy against colorectal cancer

Interferon-α (IFNα) has multiple antitumor effects including direct antitumor toxicity and the ability to potently stimulate both innate and adaptive immunity. However, its clinical applications in the treatment of malignancies have been limited because of short half-life and serious adverse reactions when attempting to deliver therapeutically effective doses. To address these issues, we fused IFNα2a to the anti-vascular endothelial growth factor and receptor 2 (VEGFR2) antibody JZA00 with the goal of targeting it to the tumor microenvironment where it can stimulate the antitumor immune response. The fusion protein, JZA01, is effective against colorectal cancer by inhibiting angiogenesis, exhibiting direct cytotoxicity, and activating the antitumor immune response. Although JZA01 exhibited reduced IFNα2 activity in vitro compared with native IFNα2, VEGFR2 targeting permitted efficient antiproliferative, proapoptotic, antiangiogenesis, and immune-stimulating effects against the colorectal tumors HCT-116 and SW620. JZA01 showed in vivo efficacy in NOD-SCID mice-bearing established HCT-116 tumors. In conclusion, this study describes an antitumor immunotherapy that is highly promising for the treatment of colorectal cancer.

Targeted immunotherapy using anti-CD138-interferon α fusion proteins and bortezomib results in synergistic protection against multiple myeloma

Although recent advances have substantially improved the management of multiple myeloma, it remains an incurable malignancy. We now demonstrate that anti-CD138 molecules genetically fused to type I interferons (IFN) synergize with the approved therapeutic bortezomib in arresting the proliferation of human multiple myeloma cell lines both in vitro and in vivo. The anti-CD138-IFNα14 fusion protein was active in inducing increased expression of signal transducer and activator of transcription 1 (STAT1) and its phosphorylation while the cell death pathway induced by bortezomib included generation of reactive oxygen species. Interferon regulatory factor 4 (IRF4), an important survival factor for myeloma cells, was down regulated following combination treatment. Induction of cell death appeared to be caspase-independent because treatment with inhibitors of caspase activation did not decrease the level of cell death. The observed caspase-independent synergistic cell death involved mitochondrial membrane depolarization, and poly(ADP-ribose) polymerase-1 (PARP-1) cleavage, and resulted in enhanced induction of apoptosis. Importantly, using 2 different in vivo xenograft models, we found that combination therapy of anti-CD138-IFNα14 and bortezomib was able to cure animals with established tumors (7 of 8 using OCI-My5 or 8 of 8 using NCI-H929). Thus, the combination of anti-CD138-IFNα with bortezomib shows great promise as a novel therapeutic approach for the treatment of multiple myeloma, a malignancy for which there are currently no cures.

Overcoming rituximab drug-resistance by the genetically engineered anti-CD20-hIFN-α fusion protein: Direct cytotoxicity and synergy with chemotherapy

Treatment of patients with B-NHL with rituximab and CHOP has resulted in significant clinical responses. However, a subset of patients develops resistance to further treatments. The mechanism of unresponsiveness in vivo is not known. We have reported the development of rituximab-resistant clones derived from B-NHL cell lines as models to investigate the mechanism of resistance. The resistant clones exhibit hyper-activated survival/anti-apoptotic pathways and no longer respond to a combination of rituximab and drugs. Recent studies reported the therapeutic efficacy in mice bearing B-cell lymphoma xenografts following treatment with the anti-CD20-hIFNα fusion protein. We hypothesized that the fusion protein may bypass rituximab resistance and inhibit survival signaling pathways. Treatment of the rituximab-resistant clones with anti-CD20-hIFNα, but not with rituximab, IFNα, or rituximab+IFNα resulted in significant inhibition of cell proliferation and induction of cell death. Treatment with anti-CD20-hIFNα sensitized the cells to apoptosis by CDDP, doxorubicin and Treanda. Treatment with anti-CD20-hIFNα inhibited the NF-κB and p38 MAPK activities and induced the activation of PKC-δ and Stat-1. These effects were corroborated by the use of the inhibitors SB203580 (p38 MAPK) and Rottlerin (PKC-δ). Treatment with SB203580 enhanced the sensitization of the resistant clone by anti-CD20-hIFNα to CDDP apoptosis. In contrast, treatment with Rotterin inhibited significantly the sensitization induced by anti-CD20-hIFNα. Overall, the findings demonstrate that treatment with anti-CD20-hIFNα reverses resistance of B-NHL. These findings suggest the potential application of anti-CD20-hIFNα in combination with drugs in patients unresponsive to rituximab-containing regimens.

Monocyte recruitment by HLA IgG-activated endothelium: the relationship between IgG subclass and FcγRIIa polymorphisms

It is currently unclear which donor specific HLA antibodies confer the highest risk of antibody-mediated rejection (AMR) and allograft loss. In this study, we hypothesized that two distinct features (HLA IgG subclass and Fcγ receptor [FcγR] polymorphisms) which vary from patient to patient, influence the process of monocyte trafficking to and macrophage accumulation in the allograft during AMR in an interrelated fashion. Here, we investigated the contribution of human IgG subclass and FcγR polymorphisms in monocyte recruitment in vitro by primary human aortic endothelium activated with chimeric anti-HLA I human IgG1 and IgG2. Both subclasses triggered monocyte adhesion to endothelial cells, via a two-step process. First, HLA I crosslinking by antibodies stimulated upregulation of P-selectin on endothelium irrespective of IgG subclass. P-selectin-induced monocyte adhesion was enhanced by secondary interactions of IgG with FcγRs, which was highly dependent upon subclass. IgG1 was more potent than IgG2 through differential engagement of FcγRs. Monocytes homozygous for FcγRIIa-H131 adhered more readily to HLA antibody-activated endothelium compared with FcγRIIa-R131 homozygous. Finally, direct modification of HLA I antibodies with immunomodulatory enzymes EndoS and IdeS dampened recruitment by eliminating antibody-FcγR binding, an approach that may have clinical utility in reducing AMR and other forms of antibody-induced inflammation.

Suppression of Fcγ-receptor-mediated antibody effector function during persistent viral infection

Understanding how viruses subvert host immunity and persist is essential for developing strategies to eliminate infection. T cell exhaustion during chronic viral infection is well described, but effects on antibody-mediated effector activity are unclear. Herein, we show that increased amounts of immune complexes generated in mice persistently infected with lymphocytic choriomeningitis virus (LCMV) suppressed multiple Fcγ-receptor (FcγR) functions. The high amounts of immune complexes suppressed antibody-mediated cell depletion, therapeutic antibody-killing of LCMV infected cells and human CD20-expressing tumors, as well as reduced immune complex-mediated cross-presentation to T cells. Suppression of FcγR activity was not due to inhibitory FcγRs or high concentrations of free antibody, and proper FcγR functions were restored when persistently infected mice specifically lacked immune complexes. Thus, we identify a mechanism of immunosuppression during viral persistence with implications for understanding effective antibody activity aimed at pathogen control.

Anti-CD138-targeted interferon is a potent therapeutic against multiple myeloma

Multiple myeloma (MM), a plasma cell malignancy, is the second most prevalent hematologic malignancy in the US. Although much effort has been made trying to understand the etiology and the complexities of this disease with the hope of developing effective therapies, MM remains incurable at this time. Because of their antiproliferative and proapoptotic activities, interferons (IFNs) have been used to treat various malignancies, including MM. Although some success has been observed, the inherent toxicities of IFNs limit their efficacy. To address this problem, we produced anti-CD138 antibody fusion proteins containing either IFNα2 or a mutant IFNα2 (IFNα2(YNS)) with the goal of targeting IFN to CD138-expressing cells, thereby achieving effective IFN concentrations at the site of the tumor in the absence of toxicity. The fusion proteins inhibited the proliferation and induced apoptosis of U266, ANBL-6, NCI-H929, and MM1-144 MM cell lines. The fusion proteins decreased the expression of IFN regulatory factor 4 (IRF4) in U266. In addition, the fusion proteins were effective against primary cells from MM patients, and treatment with fusion proteins prolonged survival in the U266 murine model of MM. These studies show that IFNα antibody fusion proteins can be effective novel therapeutics for the treatment of MM.

Antibody-cytokine fusion proteins for treatment of cancer: engineering cytokines for improved efficacy and safety

The true potential of cytokine therapies in cancer treatment is limited by the inability to deliver optimal concentrations into tumor sites due to dose-limiting systemic toxicities. To maximize the efficacy of cytokine therapy, recombinant antibody-cytokine fusion proteins have been constructed by a number of groups to harness the tumor-targeting ability of monoclonal antibodies. The aim is to guide cytokines specifically to tumor sites where they might stimulate more optimal anti-tumor immune responses while avoiding the systemic toxicities of free cytokine therapy. Antibody-cytokine fusion proteins containing interleukin (IL)-2, IL-12, IL-21, tumor necrosis factor (TNF)α, and interferons (IFNs) α, β, and γ have been constructed and have shown anti-tumor activity in preclinical and early-phase clinical studies. Future priorities for development of this technology include optimization of tumor targeting, bioactivity of the fused cytokine, and choice of appropriate agents for combination therapies. This review is intended to serve as a framework for engineering an ideal antibody-cytokine fusion protein, focusing on previously developed constructs and their clinical trial results.

Anti-CD20-interferon-alpha fusion protein has superior in vivo activity against human B-cell lymphomas compared to rituximab and enhanced complement-dependent cytotoxicity in vitro

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Background: We previously reported an anti-CD20-interferon (IFN)-alpha fusion protein able to induce apoptosis and promote in vivo eradication of a human CD20-expressing mouse B cell lymphoma (Xuan et al, Blood 2010). We now report the activity of a recombinant anti-CD20-human IFNα fusion protein against human non-Hodgkin B cell lymphomas (NHL). Methods: Anti-CD20-hIFNα was evaluated against a panel of human Burkitt, diffuse large B cell (DLBCL), and mantle cell lymphoma cell lines. Proliferation was measured by [3H]-thymidine, complement-dependent cytotoxicity (CDC) by PI flow cytometry, and antibody-dependent cellular cytotoxicity (ADCC) by LDH release using PBMC effectors. NHL xenografts were grown in SCID mice. Results: Anti-CD20-hIFNα induced stronger growth inhibition than rituximab, particularly against Burkitt and germinal center-type DLBCL NHLs. Tumor growth inhibition by anti-CD20-hIFNα was associated with substantial apoptosis in some cell lines. Anti-CD20-hIFNα exhibited potent ADCC activity against Daudi, Ramos, and Raji cells, identical to rituximab. Surprisingly, anti-CD20-hIFNα exhibited superior CDC compared to rituximab against Daudi, Ramos, and Raji cells, that was dependent upon linkage of IFNα to the anti-CD20 antibody, and correlated with improved complement fixation. Importantly, anti-CD20-hIFNα achieved superior efficacy compared to rituximab and control fusion protein against multiple NHL xenografts in SCID mice (Raji: p=0.002 and OCI-Ly19: p<0.0001). At antibody doses at which Raji xenografts progressed through rituximab, anti-CD20-hIFNα eradicated 50-88% of established tumors. Non-targeted control fusion protein had only minor effects on tumor growth. Conclusions: Anti-CD20-hIFNα has stronger direct anti-proliferative and CDC activities than rituximab against human NHL while retaining potent ADCC activity, and also has the ability to eradicate established NHL xenografts in vivo. These results support the further development of anti-CD20-hIFNα for the treatment of B cell NHL, and a phase I first-in-human clinical trial is currently being planned.

The SRC family tyrosine kinase HCK and the ETS family transcription factors SPIB and EHF regulate transcytosis across a human follicle-associated epithelium model

A critical step in the induction of adaptive mucosal immunity is antigen transcytosis, in which luminal antigens are transported to organized lymphoid tissues across the follicle-associated epithelium (FAE) of Peyer's patches. However, virtually nothing is known about intracellular signaling proteins and transcription factors that regulate apical-to-basolateral transcytosis. The FAE can transcytose a variety of luminal contents, including inert particles, in the absence of specific opsonins. Furthermore, it expresses receptors for secretory immunoglobulin A (SIgA), the main antibody in mucosal secretions, and uses them to efficiently transcytose SIgA-opsonized particles present in the lumen. Using a human FAE model, we show that the tyrosine kinase HCK regulates apical-to-basolateral transcytosis of non-opsonized and SIgA-opsonized particles. We also show that, in cultured intestinal epithelial cells, ectopic expression of the transcription factor SPIB or EHF is sufficient to activate HCK-dependent apical-to-basolateral transcytosis of these particles. Our results provide the first molecular insights into the intracellular regulation of antigen sampling at mucosal surfaces.

A CD19/Fc fusion protein for detection of anti-CD19 chimeric antigen receptors

Background

Chimeric Antigen Receptors (CARs) consist of the antigen-recognition portion of a monoclonal antibody fused to an intracellular signaling domain capable of activating T-cells. CARs displayed on the surface of transduced cells perform non-MHC-restricted antigen recognition and activating intracellular signaling pathways for induction of target cytolysis, cytokine secretion and proliferation. Clinical trials are in progress assessing the use of mature T-lymphocytes transduced with CARs targeting CD19 antigen to treat B-lineage malignancies. CD19 is an attractive target for immunotherapy because of its consistent and specific expression in most of the stages of maturation and malignancies of B-lymphocyte origin, but not on hematopoietic stem cells. Antibodies against the extracellular domain of the CAR molecule (anti-Fab, Fc or idiotype) have been used for detection of CAR expression in research and clinical samples by flow cytometry, but may need development for each construct and present significant background in samples from xenograft models.

Methods

A specific reagent for the detection of anti-CD19 CAR expression was developed, a fusion protein consisting of human CD19 extracellular domains and the Fc region of human IgG1 (CD19sIg). Genes encoding CD19sIg fusion proteins were constructed by fusing either exons 1 to 3 (CD19sIg1-3) or exons 1 to 4 (CD19sIg1-4) of the human CD19 cDNA to a human IgG₁Fc fragment. These fusion proteins are intended to work in similar fashion as the MHC Tetramers used for identification of antigen-specific T-cells, and may also have other applications in studies of activation of anti-CD19 CAR bearing cells. The CD19sIg proteins were produced from 293 T cells by stable lentiviral vector transduction and purification from culture medium.

Results

ELISA assays using several different monoclonal antibodies to CD19 demonstrated dose-related specific binding by the fusion molecule CD19sIg1-4, but no binding by CD19sIg1-3. Conjugation of the CD19sIg1-4 fusion protein to Alexa Fluor 488 allowed specific and sensitive staining of anti-CD19 CAR-bearing cells for flow cytometry assays, detecting as low as 0.5% of CAR-modified primary cells with minimal background staining.

Conclusions

This fusion molecule is a sensitive reagent for detection of anti-CD19 CAR derived from any monoclonal antibody present in CAR-modified T-cells.

In vitro C3 deposition on Cryptococcus capsule occurs via multiple complement activation pathways

Complement can be activated via three pathways: classical, alternative, and lectin. Cryptococcus gattii and Cryptococcus neoformans are closely related fungal pathogens possessing a polysaccharide capsule composed mainly of glucuronoxylomannan (GXM), which serves as a site for complement activation and deposition of complement components. We determined C3 deposition on Cryptococcus spp. by flow cytometry and confocal microscopy after incubation with serum from C57BL/6J mice as well as mice deficient in complement components C4, C3, factor B, and mannose binding lectin (MBL). C. gattii and C. neoformans activate complement in EGTA-treated serum indicating that they can activate the alternative pathway. However, complement activation was seen with factor B(-/-) serum suggesting activation could also take place in the absence of a functional alternative pathway. Furthermore, we uncovered a role for C4 in the alternative pathway activation by Cryptococcus spp. We also identified an unexpected and complex role for MBL in complement activation by Cryptococcus spp. No complement activation occurred in the absence of MBL-A and -C proteins although activation took place when the lectin binding activity of MBL was disrupted by calcium chelation. In addition, alternative pathway activation by C. neoformans required both MBL-A and -C, while either MBL-A or -C was sufficient for alternative pathway activation by C. gattii. Thus, complement activation by Cryptococcus spp. can take place through multiple pathways and complement activation via the alternative pathway requires the presence of C4 and MBL proteins.

Differences in N-glycan structures found on recombinant IgA1 and IgA2 produced in murine myeloma and CHO cell lines

The development and production of recombinant monoclonal antibodies is well established. Although most of these are IgGs, there is also great interest in producing recombinant IgAs since this isotype plays a critical role in providing immunologic protection at mucosal surfaces. The choice of expression system for production of recombinant antibodies is crucial because they are glycoproteins containing at least one N-linked carbohydrate. These glycans have been shown to contribute to the stability, pharmacokinetics and biologic function of antibodies. We have produced recombinant human IgA1 and all three allotypes of IgA2 in murine myeloma and CHO cell lines to systematically characterize and compare the N-linked glycans. Recombinant IgAs produced in murine myelomas differ significantly from IgA found in humans in that they contain the highly immunogenic Galalpha(1,3)Gal epitope and N-glycolylneuraminic acid residues, indicating that murine myeloma is not the optimal expression system for the production of human IgA. In contrast, IgAs produced in CHO cells contained glycans that were more similar to those found on human IgA. Expression of IgA1 and IgA2 in Lec2 and Lec8 cell lines that are defective in glycan processing resulted in a less complex pool of N-glycans. In addition, the level of sialylation of rIgAs produced in murine and CHO cells was significantly lower than that previously reported for serum IgA1. These data underscore the importance of choosing the appropriate cell line for the production of glycoproteins with therapeutic potential.

Characterization of an engineered human purine nucleoside phosphorylase fused to an anti-her2/neu single chain Fv for use in ADEPT

Background

Antibody Directed Enzyme Prodrug Therapy (ADEPT) can be used to generate cytotoxic agents at the tumor site. To date non-human enzymes have mainly been utilized in ADEPT. However, these non-human enzymes are immunogenic limiting the number of times that ADEPT can be administered. To overcome the problem of immunogenicity, a fully human enzyme, capable of converting a non-toxic prodrug to cytotoxic drug was developed and joined to a human tumor specific scFv yielding a fully human targeting agent.

Methods

A double mutant of human purine nucleoside phosphorylase (hDM) was developed which unlike the human enzyme can cleave adenosine-based prodrugs. For tumor-specific targeting, hDM was fused to the human anti-HER2/neu single chain Fv (scFv), C6 MH3B1. Enzymatic activity of hDM with its natural substrates and prodrugs was determined using spectrophotomeric approaches. A cell proliferation assay was used to assess the cytotoxicity generated following conversion of prodrug to drug as a result of enzymatic activity of hDM. Affinity of the targeting scFv, C6 MH3B1 fused to hDM to Her2/neu was confirmed using affinity chromatography, surface plasmon resonance, and flow-cytometry.

Results

In vitro hDM-C6 MH3B1 binds specifically to HER2/neu expressing tumor cells and localizes hDM to tumor cells, where the enzymatic activity of hDM-C6 MH3B1, but not the wild type enzyme, results in phosphorolysis of the prodrug, 2-fluoro-2'-deoxyadenosine to the cytotoxic drug 2-fluoroadenine (F-Ade) causing inhibition of tumor cell proliferation. Significantly, the toxic small drug diffuses through the cell membrane of HER2/neu expressing cells as well as cells that lack the expression of HER2/neu, causing a bystander effect. F-Ade is toxic to cells irrespective of their growth rate; therefore, both the slowly dividing tumor cells and the non-dividing neighboring stromal cells that support tumor growth should be killed. Analysis of potential novel MHCII binding peptides resulting from fusion of hDM to C6 MH3B1 and the two mutations in hDM, and of the structure of hDM compared to the wild-type enzyme suggests that hDM-C6 MH3B1 should exhibit minimal immunogenicity in humans.

Conclusion

hDM-C6 MH3B1 constitutes a novel human based protein that addresses some of the limitations of ADEPT that currently preclude its successful use in the clinic.

A rapid and economic in-house DNA purification method using glass syringe filters

Background

Purity, yield, speed and cost are important considerations in plasmid purification, but it is difficult to achieve all of these at the same time. Currently, there are many protocols and kits for DNA purification, however none maximize all four considerations.

Methodology/Principal Findings

We now describe a fast, efficient and economic in-house protocol for plasmid preparation using glass syringe filters. Plasmid yield and quality as determined by enzyme digestion and transfection efficiency were equivalent to the expensive commercial kits. Importantly, the time required for purification was much less than that required using a commercial kit.

Conclusions/Significance

This method provides DNA yield and quality similar to that obtained with commercial kits, but is more rapid and less costly.

Structure of a mutant human purine nucleoside phosphorylase with the prodrug, 2-fluoro-2'-deoxyadenosine and the cytotoxic drug, 2-fluoroadenine

A double mutant of human purine nucleoside phosphorylase (hDM) with the amino acid mutations Glu201Gln:Asn243Asp cleaves adenosine-based prodrugs to their corresponding cytotoxic drugs. When fused to an anti-tumor targeting component, hDM is targeted to tumor cells, where it effectively catalyzes phosphorolysis of the prodrug, 2-fluoro-2'-deoxyadenosine (F-dAdo) to the cytotoxic drug, 2-fluoroadenine (F-Ade). This cytotoxicity should be restricted only to the tumor microenvironment, because the endogenously expressed wild type enzyme cannot use adenosine-based prodrugs as substrates. To gain insight into the interaction of hDM with F-dAdo, we have determined the crystal structures of hDM with F-dAdo and F-Ade. The structures reveal that despite the two mutations, the overall fold of hDM is nearly identical to the wild type enzyme. Importantly, the residues Gln201 and Asp243 introduced by the mutation form hydrogen bond contacts with F-dAdo that result in its binding and catalysis. Comparison of substrate and product complexes suggest that the side chains of Gln201 and Asp243 as well as the purine base rotate during catalysis possibly facilitating cleavage of the glycosidic bond. The two structures suggest why hDM, unlike the wild-type enzyme, can utilize F-dAdo as substrate. More importantly, they provide a critical foundation for further optimization of cleavage of adenosine-based prodrugs, such as F-dAdo by mutants of human purine nucleoside phosphorylase.

Humanized ADEPT comprised of an engineered human purine nucleoside phosphorylase and a tumor targeting peptide for treatment of cancer

Immunogenicity caused by the use of nonhuman enzymes in antibody-directed enzyme prodrug therapy has limited its clinical application. To overcome this problem, we have developed a mutant human purine nucleoside phosphorylase, which, unlike the wild-type enzyme, accepts (deoxy)adenosine-based prodrugs as substrates. Among the different mutants of human purine nucleoside phosphorylase tested, a double mutant with amino acid substitutions E201Q:N243D (hDM) is the most efficient in cleaving (deoxy)adenosine-based prodrugs. Although hDM is capable of using multiple prodrugs as substrates, it is most effective at cleaving 2-fluoro-2'-deoxyadenosine to a cytotoxic drug. To target hDM to the tumor site, the enzyme was fused to an anti-HER-2/neu peptide mimetic (AHNP). Treatment of HER-2/neu-expressing tumor cells with hDM-AHNP results in cellular localization of enzyme activity. As a consequence, harmless prodrug is converted to a cytotoxic drug in the vicinity of the tumor cells, resulting in tumor cell apoptosis. Unlike the nonhuman enzymes, the hDM should have minimal immunogenicity when used in antibody-directed enzyme prodrug therapy, thus providing a novel promising therapeutic agent for the treatment of tumors.

N-terminal domain-deleted mu transposase exhibits increased transposition activity with low target site preference in modified buffers

BACKGROUND

Transposition using MuA and the Mu-transposon is frequently used for insertional and deletional mutagenesis and to introduce primer sequences into DNA of unknown sequence. However, mutagenesis studies are often limited by the number of transposition events taking place within a small target sequence. Although the intrinsic target site preference of MuA is low, it nevertheless may limit the recovery of desired events.

METHODS

In the current study, we have compared the transposition activity of wild-type, C-terminally deleted, N-terminally deleted and both C- and N-terminally deleted MuA.

RESULTS

We found that N-terminally deleted MuA was most active with an about sevenfold increase in transposition efficiency compared to wild-type. In addition, we identified a novel reaction condition in which the transposition activity of N-terminally deleted MuA was increased about 45-fold.

CONCLUSION

The use of the N-terminally deleted MuA with the newly established condition enhanced the relative transposition activity about 280-fold compared to that of wild-type MuA with the conventional buffer. In addition, the optimized buffer decreased the target site preference of N-terminally deleted MuA resulting in a more even distribution of integration events throughout the target gene.

Transformation of E. coli by electroporation

Using electroporation to transform Escherichia coli results in transformation efficiencies greater than can be obtained using the best chemical methods. It is easy to obtain transformation efficiencies 10(8) per milligram DNA and efficiencies of 10(10) have been reported. This appendix describes a procedure for electroporation that can be used to transform many different types of bacteria.

Cloning, expression, and modification of antibody V regions

Cloned variable (V) regions of antibodies can be expressed joined to any constant (C) region, from either the same or a different species. The resulting antibodies will have the desired associated effector functions. Chimeric antibodies obtained by joining murine V regions to human C regions should have decreased immunogenicity in humans. The process of complementarity determining region (CDR) grafting, in which the CDRs from an antibody of one species are transferred to the framework regions of another species, constitutes a further modification of this approach. The protocols presented in this unit are designed to permit PCR-based cloning of heavy and light chain V regions. This is an advanced molecular biology protocol and should be employed only by investigators who are sufficiently skilled and experienced.

Proteases from Schistosoma mansoni cercariae cleave IgE at solvent exposed interdomain regions

Parasitic infections, including schistosomiasis, are associated with high titres of specific and non-specific IgE antibody, and many reports show an in vitro role for IgE in parasite killing. Despite an active immune response, schistosomes survive for long periods in the human bloodstream, implying that the parasite is able to overcome or evade the IgE response mounted against it. One such mechanism is through cleavage of IgE into non-functional fragments by potent parasite derived enzymes. Using domain swap antibodies, recombinant Fcepsilon, and C-terminally tagged Cepsilon4 domains, we have narrowed down the principal cleavage sites to the Cepsilon2/Cepsilon3 and Cepsilon3/Cepsilon4 interdomain region of the IgE-Fc. Two serine proteases, one chymotrypsin-like and the second trypsin-like, have been proposed to be involved. Inhibition assays using selective inhibitors confirmed that both proteases contribute to Fc cleavage, although the chymotrypsin-like enzyme makes the greater contribution. Protein sequencing of IgE fragments cleaved by highly pure preparations of the chymotrypsin-like enzyme revealed that cleavage also occurred post Lys residues within kappa light chain dimers (LELK/GA). Related sequences are found in myosin, thrombospondin, collagen and actin-related proteins; macromolecules present in the skin and through which cercariae must penetrate to initiate an infection. Chemical knockout experiments using specific inhibitors and chromogenic substrates allowed us to show that the trypsin-like enzyme was responsible for light chain cleavage. The finding that pathogenic proteases can cleave the Fc of IgE may provide a useful biochemical tool for the further analysis of IgE structure. Indeed, the finding may raise new possibilities for treatment of IgE-mediated allergic reactions mediated through Fcepsilon-receptors.

Targeting IFN-alpha to B cell lymphoma by a tumor-specific antibody elicits potent antitumor activities

IFN-alpha, a cytokine crucial for the innate immune response, also demonstrates antitumor activity. However, use of IFN-alpha as an anticancer drug is hampered by its short half-life and toxicity. One approach to improving IFN-alpha's therapeutic index is to increase its half-life and tumor localization by fusing it to a tumor-specific Ab. In the present study, we constructed a fusion protein consisting of anti-HER2/neu-IgG3 and IFN-alpha (anti-HER2/neu-IgG3-IFN-alpha) and investigated its effect on a murine B cell lymphoma, 38C13, expressing human HER2/neu. Anti-HER2/neu-IgG3-IFN-alpha exhibited potent inhibition of 38C13/HER2 tumor growth in vivo. Administration of three daily 1-microg doses of anti-HER2/neu-IgG3-IFN-alpha beginning 1 day after tumor challenge resulted in 88% of the mice remaining tumor free. Remarkably, anti-HER2/neu-IgG3-IFN-alpha demonstrated potent activity against established 38C13/HER2 tumors, with complete tumor remission observed in 38% of the mice treated with three daily doses of 5 microg of the fusion protein (p = 0.0001). Ab-mediated targeting of IFN-alpha induced growth arrest and apoptosis of lymphoma cells contributing to the antitumor effect. The fusion protein also had a longer in vivo half-life than rIFN-alpha. These results suggest that IFN-alpha Ab fusion proteins may be effective in the treatment of B cell lymphoma.

Incomplete assembly of IgA2m(2) in Chinese hamster ovary cells

Myeloma and Chinese hamster ovary (CHO) cells are frequently used for the production of recombinant antibodies. With increasing interest in producing recombinant IgA for protection against infectious agents, it is essential to characterize the IgA produced in these cells. Here we show that while myeloma cells secrete IgA2m(2) predominantly as H(2)L(2), CHO cells secrete H(2)L and H(2) in addition to fully assembled H(2)L(2). When the CHO cells also synthesize J chain and secretory component (SC), polymeric IgA and secretory IgA in which SC is disulfide bonded to the polymeric IgA are produced. Blocking cysteines on purified IgA2m(2) protein by alkylating with iodoacetamide stabilizes the disulfide bonds between the H and L chains suggesting that the disulfide bonds between H and L chains are unstable. Taken together our results suggest that the covalent assembly of IgA2m(2) is different in myeloma and CHO cells.

Targeting, imaging, and therapy using a humanized antiprostate stem cell antigen (PSCA) antibody

The murine 1G8 (micro1G8) monoclonal antibody directed against prostate stem cell antigen (PSCA) prevents prostate tumor establishment, growth, and metastasis in murine models. To further delineate in vivo targeting properties, micro1G8 was radiolabeled with In-111 and evaluated in nude mice bearing PC3-PSCA xenografts. Tumor activity ranged from 11.8% to 17.1% injected dose per gram (ID/g) at 24 to 96 hours postinjection. To extend the clinical applicability of micro1G8, a chimeric 1G8 antibody was produced that exhibited specific binding to PSCA and significant antitumor effect over micro1G8 in established LAPC-9 prostate cancer xenografts (P=0.0014). However, low expression yields and instability prompted us to humanize 1G8 by grafting the complementary determining regions onto the stable, human Fv framework of anti-p185 4D5v8 (trastuzumab). Two humanized 1G8 (hu1G8) versions (A and B) that differed in the number of murine residues present in the C-terminal half of CDR-H2, were produced. Biacore binding studies demonstrated affinities of 1.47 nM for micro1G8 and 3.74 nM for hu2B3-B, representing a 2.5-fold reduction. Tumor targeting of version B radioiodinated with I was evaluated by serial microPET imaging. Specific tumor targeting of I-hu1G8-B to PC3-PSCA [12.7 (+/-1.6)% ID/g at 94 h] and LAPC-9 [6.6 (+/-0.9)% ID/g at 168 h) xenografts was observed. Inhibition of tumor growth by hu1G8-B was demonstrated in mice bearing low-expressing SW-780-PSCA bladder carcinoma xenografts. In this model, the micro1G8 was ineffective, whereas the hu1G8-B exhibited approximately 50% inhibitory effect. These data support further development of hu1G8 anti-PSCA antibody for targeted imaging and therapy for tumors of urogenital origin.

Human immunoglobulin G2 (IgG2) and IgG4, but not IgG1 or IgG3, protect mice against Cryptococcus neoformans infection

The encapsulated yeast Cryptococcus neoformans is a significant cause of meningitis and death in patients with AIDS. Some murine monoclonal antibodies (MAbs) against the glucuronoxylomannan (GXM) component of the C. neoformans capsular polysaccharide can prolong the lives of infected mice, while others have no effect or can even shorten survival. To date, no one has systematically compared the efficacies of antibodies with the same variable regions and different human constant regions with their unique combination of effector functions in providing protection against murine C. neoformans infection. In the present study, we examined the efficacies of anti-GXM MAbs of the four human immunoglobulin G (IgG) subclasses, which have identical variable regions but differ in their capacities to bind the three types of Fc receptors for IgG (FcgammaR), their abilities to activate complement, and their half-lives. IgG2 and IgG4 anti-GXM prolonged the lives of infected BALB/c mice, IgG3 anti-GXM did not affect animal survival, while mice treated with IgG1 anti-GXM died earlier than mice treated with phosphate-buffered saline or irrelevant isotype-matched MAbs. All MAbs decreased serum GXM in infected animals. Effector pathways traditionally believed to be important in defense against microbes, such as opsonophagocytosis and complement binding, negatively correlated with antibody efficacy. It is generally accepted that human IgG1 has the most favorable combination of effector functions for therapeutic use against infections. Therefore, our findings have significant implications for humanization of the mouse IgG1 currently in clinical trials for cryptococcal meningitis and for the design of antibody therapeutics to treat other infectious diseases as well.

Recombinant IgA Antibodies

The production of monoclonal antibodies and the development of recombinant antibody technology have made antibodies one of the largest classes of drugs in development for prophylactic, therapeutic and diagnostic purposes. Currently, all of the Food and Drug Administration (FDA)- approved antibodies are immunoglobulin Gs (IgGs). However, more than 95%of the infections are initiated at the mucosal surfaces, where IgA is the primary immune effector antibody.

The IgD CH1 region contains the binding site for the human respiratory pathogenMoraxella catarrhalis IgD-binding protein MID

The Moraxella catarrhalis IgD-binding protein (MID) has a unique specificity for human IgD, and the sequence with maximal IgD binding is located within the amino acids MID962-1200. In the present paper, we examined the MID binding site on IgD using a series of recombinant Ig. Full-length IgD, IgD F(ab')2, and an IgD F(ab') C290R mutant lacking the inter-heavy-chain cysteine 290 were manufactured. Furthermore, a series of IgD/IgG chimeras were constructed. ELISA, dot blot and flow cytometry were used to study the binding of purified Ig to native MID, recombinant MID962-1200 or to Moraxella with or without MID. MID962-1200 bound both the IgD F(ab')2 and F(ab') C290R, indicating that the binding occurred independently of antibody structure. When amino acids 157-224 of the IgD CH1 region were substituted with IgG sequences, binding by M. catarrhalis or recombinant MID962-1200 was abolished. Subsequent smaller substitutions of IgD CH1 157-224 with IgG sequences led us to conclude that IgD CH1 amino acids 198-206 were crucial for the interaction between MID and IgD.

Molecular events contributing to cell death in malignant human hematopoietic cells elicited by an IgG3-avidin fusion protein targeting the transferrin receptor

We have previously reported that an anti-human transferrin receptor IgG3-avidin fusion protein (anti-hTfR IgG3-Av) inhibits the proliferation of an erythroleukemia-cell line. We have now found that anti-hTfR IgG3-Av also inhibits the proliferation of additional human malignant B and plasma cells. Anti-hTfR IgG3-Av induces internalization and rapid degradation of the TfR. These events can be reproduced in cells treated with anti-hTfR IgG3 cross-linked with a secondary Ab, suggesting that they result from increased TfR cross-linking. Confocal microscopy of cells treated with anti-hTfR IgG3-Av shows that the TfR is directed to an intracellular compartment expressing the lysosomal marker LAMP-1. The degradation of TfR is partially blocked by cysteine protease inhibitors. Furthermore, cells treated with anti-hTfR IgG3-Av exhibit mitochondrial depolarization and activation of caspases 9, 8, and 3. The mitochondrial damage and cell death can be prevented by iron supplementation, but cannot be fully blocked by a pan-caspase inhibitor. These results suggest that anti-hTfR IgG3-Av induces lethal iron deprivation, but the resulting cell death does not solely depend on caspase activation. This report provides insights into the mechanism of cell death induced by anti-TfR Abs such as anti-hTfR IgG3-Av, a molecule that may be useful in the treatment of B-cell malignancies such as multiple myeloma.

Development of new models for the analysis of Fc–FcRn interactions

An important question remains as to which FcRn binding parameters, if any, correlate with the serum half-life of antibodies. In the present study, we used a BIACore surface plasmon resonance (SPR) device to study kinetic properties of antibody binding to FcRn at different pHs and under different binding reaction conditions. The ability of many different models to fit the data was tested. The previous models could not adequately explain all of the data collected. We now present models that have intuitive appeal and fit a broader range of data than previous models. Specifically, the model assumes that there are two forms of FcRn on the BIAcore chip and that, in addition to monomeric IgG, there is some aggregated IgG that can function as ligand. Although this model represents an improvement over previous models, it is still not globally valid for the entire range of data that was collected. Even with these limitations, the model provides a powerful new tool to analyze not only FcRn-IgG interactions but also other complex protein-protein interactions.

Anti-HER2/neu IgG3–(IL-2) and anti-HER2/neu IgG3–(GM-CSF) promote HER2/neu processing and presentation by dendritic cells: Implications in immunotherapy and vaccination strategies

HER2/neu, a transmembrane glycoprotein overexpressed in several types of human cancers, is a potential target for active immunotherapy. However, this protein and especially its extracellular domain (ECD(HER2)), is weakly immunogenic and is poorly processed by dendritic cells (DCs). Previously, we showed that anti-HER2/neu IgG3-(IL-2) and anti-HER2/neu IgG3-(GM-CSF) fusion proteins can enhance the immunogenicity of ECD(HER2) in mice, and that the non-covalent physical association between each antibody fusion proteins and ECD(HER2) was critical to elicit optimal protective immunity against HER2/neu expressing tumors. We now use the professional antigen-presenting DCs to investigate the effect of the antibody fusion protein binding to ECD(HER2) on its trafficking and presentation. We found that when the extracellular domain of HER2/neu fused to ovalbumin (OVA-ECD(HER2)) is bound by HER2/neu-specific antibody-(IL-2) or antibody-(GM-CSF) fusion proteins, the bound antigen is more efficiently processed by murine bone-marrow-derived dendritic cells (BMDCs) and presented to OVA-specific T-cells than the unbound OVA-ECD(HER2). We also found that ECD(HER2) bound by anti-HER2/neu IgG3-(IL-2) is very efficiently internalized and that the internalized ECD(HER2) is not retained in the early endosomal compartments but traffics to the antigen-processing compartments. These results are consistent with our earlier in vivo studies and suggest that both antibody-(IL-2) and antibody-(GM-CSF) fusion proteins can be used to enhance the immune response to poorly immunogenic antigens including tumor-associated antigens (TAAs).

A Trimeric Anti-HER2/neuScFv and Tumor Necrosis Factor-α Fusion Protein Induces HER2/neuSignaling and Facilitates Repair of Injured Epithelia

Tumor necrosis factor (TNF)-alpha genetically fused to the carboxyl terminus of a single-chain Fv (ScFv) antibody specific for the human HER2/neu (anti-HER2/neu ScFv-TNF-alpha) forms a homotrimeric structure that retains both TNF-alpha activity and the ability to bind HER2/neu. In contrast to anti-HER2/neu IgG3, anti-HER2/neu ScFv-TNF-alpha induces potent HER2/neu signaling, activating the downstream mitogen-activated protein kinase (MAPK) and Akt pathways in SKBR3 cells. Activation of MAPK and Akt by anti-HER2/neu ScFv-TNF-alpha inhibited the apoptosis of SKBR3 cells induced by actinomycin D. Remarkably, anti-HER2/neu ScFv-TNF-alpha facilitated the repair of injured epithelia. Accelerated wound healing required binding to HER2/neu but not TNF-alpha activity since anti-HER2/neu ScFv-TNF-alpha (S147Y), containing a mutant TNF-alpha with significantly decreased biological activity, demonstrated equivalent ability to facilitate wound healing and soluble HER2/neu inhibited the effect. These results suggest that trimeric anti-HER2/neu ScFv has the potential to facilitate wound healing. In addition, fusion with TNF-alpha provides a novel approach to producing polymeric antibodies.

Enhanced inhibition of murine tumor and human breast tumor xenografts using targeted delivery of an antibody-endostatin fusion protein

Endostatin can inhibit angiogenesis and tumor growth in mice. A potential limitation of endostatin as an antitumor agent in humans is the short serum half-life of the protein that may decrease effective concentration at the site of tumor and necessitate frequent dosing. In an effort to improve antitumor activity, endostatin was fused to an antibody specific for the tumor-selective HER2 antigen to create an antibody-endostatin fusion protein (anti-HER2 IgG3-endostatin). Normal endostatin rapidly cleared from serum in mice (T(1/2)(2), = 0.6-3.8 hours), whereas anti-HER2 IgG3-endostatin had a prolonged half-life (90% intact; T(1/2)(2), 40.2-44.0 hours). Antigen-specific targeting of anti-HER2 IgG3-endostatin was evaluated in BALB/c mice implanted with CT26 tumors or CT26 tumors engineered to express the HER2 antigen (CT26-HER2). Radio-iodinated anti-HER2 IgG3-endostatin preferentially localized to CT26-HER2 tumors relative to CT26 tumors. Administration of anti-HER2 IgG3-endostatin to mice showed preferential inhibition of CT26-HER2 tumor growth compared with CT26. Anti-HER2 IgG3-endostatin also markedly inhibited the growth of human breast cancer SK-BR-3 xenografts in severe combined immunodeficient mice. Anti-HER2 IgG3-endostatin inhibited tumor growth significantly more effectively than endostatin, anti-HER2 IgG3 antibody, or the combination of antibody and endostatin. CT26-HER2 tumors treated with the endostatin fusion protein had decreased blood vessel density and branching compared with untreated CT26-HER2 or CT26 treated with the fusion protein. The enhanced effectiveness of anti-HER2 IgG3-endostatin may be due to a longer half-life, improved serum stability, and selective targeting of endostatin to tumors, resulting in decreased angiogenesis. Linking of an antiangiogenic protein, such as endostatin, to a targeting antibody represents a promising and versatile approach to antitumor therapy.

Insights into the mechanism of anti-tumor immunity in mice vaccinated with the human HER2/neu extracellular domain plus anti-HER2/neu IgG3-(IL-2) or anti-HER2/neu IgG3-(GM-CSF) fusion protein

In the present study, we demonstrate that a physical association between the extracellular domain of human HER2/neu receptor (ECDHER2) plus anti-HER2/neu IgG3-(IL-2) or anti-HER2/neu IgG3-(GM-CSF) was required to elicit the most effective anti-tumor immune response against a syngeneic tumor expressing rat HER2/neu. Immune effectors including CD4+, CD8+, and NK cells contributed to protection against tumor growth. Vaccinated B-cell deficient mice did not elicit tumor protection, suggesting a critical role for B-cells in a protective immune response. These results provide insights into the mechanisms responsible for the protective tumor immunity elicited when antibody-(IL-2 or GM-CSF) are used as enhancers of vaccines targeting tumor antigens.

Analysis of a family of antibodies with different half-lives in mice fails to find a correlation between affinity for FcRn and serum half-life

In this study we analyzed mouse FcRn binding to different recombinant chimeric antibodies with human constant regions. This system has the advantage that in vivo half-life in animals expressing the receptor can be directly correlated with receptor binding kinetics. The goal was to determine which FcRn binding parameters, if any, correlate with the serum half-life of antibodies. We used a BIAcore surface plasmon resonance (SPR) device to study kinetic properties at different pHs and concentrations. The data were analyzed using a new model, the dual bivalent analyte model (DBVA), which postulates that there are two types of FcRn bound to the chip, one low affinity and one high affinity. In addition, it takes into consideration the possibility that the ligand, immunoglobulin G (IgG), can exist as both monomer and as higher molecular forms. While some antibodies bind to FcRn with different kinetics, including antibodies that differ only by containing the kappa or lambda light chain--a result which itself is unexpected--we cannot identify a single FcRn binding parameter that directly correlates with Ab half-life. Importantly, we demonstrate that some IgGs with higher affinity for FcRn do not have extended in vivo half-lives.

Production of human monoclonal antibody in eggs of chimeric chickens

The tubular gland of the chicken oviduct is an attractive system for protein expression as large quantities of proteins are deposited in the egg, the production of eggs is easily scalable and good manufacturing practices for therapeutics from eggs have been established. Here we examined the ability of upstream and downstream DNA sequences of ovalbumin, a protein produced exclusively in very high quantities in chicken egg white, to drive tissue-specific expression of human mAb in chicken eggs. To accommodate these large regulatory regions, we established and transfected lines of chicken embryonic stem (cES) cells and formed chimeras that express mAb from cES cell-derived tubular gland cells. Eggs from high-grade chimeras contained up to 3 mg of mAb that possesses enhanced antibody-dependent cellular cytotoxicity (ADCC), nonantigenic glycosylation, acceptable half-life, excellent antigen recognition and good rates of internalization.