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1.  Macrophage and NK-mediated Killing of Precursor-B Acute Lymphoblastic Leukemia Cells Targeted with a-Fucosylated Anti-CD19 Humanized Antibodies 
Leukemia  2013;27(6):1263-1274.
This work reports the tumoricidal effects of a novel investigational humanized anti-CD19 monoclonal antibody (Medi-551). An a-fucosylated antibody with increased affinity for human FcγRIIIA, Medi-551 is shown to mediate both antibody-dependent cellular cytotoxicity (ADCC) and phagocytosis (ADCP). Medi-551/CD19 complexes internalize slowly (>5 hrs) and thus remain accessible to effector cells for prolonged periods. We evaluated in vitro ADCC and ADCP activities of primary human natural killer (NK) cells and macrophages against pre-B ALL cell lines and pediatric patient blasts. Fluorescent imaging studies document immunological synapses formed between anti-CD19-bound target leukemia cells and effector cells and capture the kinetics of both NK-mediated killing and macrophage phagocytosis. Genetic polymorphisms in FcγRIIIA-158F/V modulate in vitro activities of effector cells, with FcγRIIIA-158V homo- or heterozygotes showing the strongest activity. Medi-551 treatment of SCID mice engrafted with human pre-B cells led to prolonged animal survival and markedly reduced disease burden in blood, liver and bone marrow. These data show that anti-CD19 antibodies effectively recruit immune cells to pre-B ALL cells and support a move forward to early phase trials in this disease.
PMCID: PMC4249624  PMID: 23307031
leukemia; pre-B ALL; ADCC; ADCP; targeted therapies; monoclonal antibodies
2.  Mycophenolic Acid Differentially Impacts B Cell Function Depending on the Stage of Differentiation 
Production of pathogenic Abs contributes to disease progression in many autoimmune disorders. The immunosuppressant agent mycophenolic acid (MPA) has shown clinical efficacy for patients with autoimmunity. The goal of these studies was to elucidate the mechanisms of action of MPA on B cells isolated from healthy individuals and autoimmune patients. In this study, we show that MPA significantly inhibited both proliferation and differentiation of primary human B cells stimulated under various conditions. Importantly, MPA did not globally suppress B cell responsiveness or simply induce cell death, but rather selectively inhibited early activation events and arrested cells in the G0/G1 phase of the cell cycle. Furthermore, MPA blocked expansion of both naive and memory B cells and prevented plasma cell (PC) differentiation and Ab production from healthy controls and individuals with rheumatoid arthritis. Finally, whereas MPA potently suppressed Ig secretion from activated primary B cells, terminally differentiated PCs were not susceptible to inhibition by MPA. The target of MPA, IMPDH2, was found to be downregulated in PCs, likely explaining the resistance of these cells to MPA. These results suggest that MPA provides benefit in settings of autoimmunity by directly preventing activation and PC differentiation of B cells; however, MPA is unlikely to impact autoantibody production by preexisting, long-lived PCs.
PMCID: PMC4180087  PMID: 21873529
3.  Cell Distance Mapping identifies functional T follicular helper cells in inflamed human renal tissue 
Science translational medicine  2014;6(230):230ra46.
T follicular helper (TFH) cells are critical for B cell activation in germinal centers and are often observed in human inflamed tissue. However, it is difficult to know if they contribute in situ to inflammation. Expressed markers define TFH subsets associated with distinct functions in vitro. However, such markers may not reflect in situ function. The delivery of T cell help to B cells requires direct cognate recognition. We hypothesized that by visualizing and quantifying such interactions we could directly assess TFH cell competency in situ. Therefore, we developed computational tools to quantify spatial relationships between different cell subtypes in tissue (Cell Distance Mapping, CDM). Analysis of inflamed human tissues indicated that measurement of internuclear distances between TFH and B cells could be used to discriminate between cognate and non-cognate interactions. Furthermore, only cognate-competent TFH cell populations expressed high levels of Bcl-6 and IL-21. These data suggest that CDM can be used to identify adaptive immune cell networks driving in situ inflammation. Such knowledge should help identify diseases, and disease subsets, that may benefit from therapeutics targeting of specific T cell:antigen presenting cell interactions.
PMCID: PMC4129446  PMID: 24695686
Lupus; nephritis; renal transplant; cell distance mapping; adaptive autoimmunity; T follicular helper cell
4.  Germinal Center B Cell Depletion Diminishes CD4+ Follicular T Helper Cells in Autoimmune Mice 
PLoS ONE  2014;9(8):e102791.
Continuous support from follicular CD4+ T helper (Tfh) cells drives germinal center (GC) responses, which last for several weeks to produce high affinity memory B cells and plasma cells. In autoimmune Sle1 and NZB/W F1 mice, elevated numbers of Tfh cells persist, promoting the expansion of self-reactive B cells. Expansion of circulating Tfh like cells have also been described in several autoimmune diseases. Although, the signals required for Tfh differentiation have now been well described, the mechanisms that sustain the maintenance of fully differentiated Tfh are less understood. Recent data demonstrate a role for GC B cells for Tfh maintenance after protein immunization.
Methods and Finding
Given the pathogenic role Tfh play in autoimmune disease, we explored whether B cells are required for maintenance of autoreactive Tfh. Our data suggest that the number of mature autoreactive Tfh cells is controlled by GC B cells. Depletion of B cells in Sle1 autoimmune mice leads to a dramatic reduction in Tfh cells. In NZB/W F1 autoimmune mice, similar to the SRBC immunization model, GC B cells support the maintenance of mature Tfh, which is dependent mainly on ICOS. The CD28-associated pathway is dispensable for Tfh maintenance in SRBC immunized mice, but is required in the spontaneous NZB/W F1 model.
These data suggest that mature Tfh cells require signals from GC B cells to sustain their optimal numbers and function in both autoimmune and immunization models. Thus, immunotherapies targeting B cells in autoimmune disease may affect pathogenic Tfh cells.
PMCID: PMC4125140  PMID: 25101629
5.  CD19 and CD32b Differentially Regulate Human B Cell Responsiveness 
B cell activation is regulated by a variety of signals. CD19 positively regulates B cell activation, augmenting signals delivered through the BCR complex. In contrast, CD32b contains an ITIM and negatively regulates BCR signaling. Importantly, there are drugs currently in clinical trials and preclinical development that cross-link CD32b to molecules within the BCR complex. We wanted to address how single engagement versus cotargeting these molecules affects human B cell function. When B cells from healthy individuals were activated by signals that mimic a T cell response (IL-21 costimulation), ligation of CD32b, but not CD19, inhibited B cell expansion and plasma cell (PC) differentiation. In contrast, when B cells were activated through TLR, anti-CD19, but not anti-CD32b, blunted the response. However, when both CD19 and CD32b were coengaged by a bispecific anti-CD19×CD32b Ab, both types of stimuli were potently inhibited. Cross-linking CD19 with CD32b also inhibited Ab-independent functions of B cells, such as HLA upregulation, cytokine production, and the ability of B cells to prime CD4+ T cells. Finally, although cross-linking CD19 and CD32b inhibited PC differentiation of primary B cells, it did not alter Ig production from pre-established PCs. These data elucidate the mechanism by which a complex set of signals determines the fate of B cell responsiveness. Although signals through CD19 influence TLR-driven activation, CD32b impacts the magnitude of the response following IL-21 costimulation. Therefore, simultaneous targeting of multiple surface molecules may be a necessary approach to comprehensively modulate B cell activation in vivo.
PMCID: PMC3918864  PMID: 24442430
7.  B-cell targeted therapeutics in clinical development 
Arthritis Research & Therapy  2013;15(Suppl 1):S4.
B lymphocytes are the source of humoral immunity and are thus a critical component of the adaptive immune system. However, B cells can also be pathogenic and the origin of disease. Deregulated B-cell function has been implicated in several autoimmune diseases, including systemic lupus erythematosus, rheumatoid arthritis, and multiple sclerosis. B cells contribute to pathological immune responses through the secretion of cytokines, costimulation of T cells, antigen presentation, and the production of autoantibodies. DNA-and RNA-containing immune complexes can also induce the production of type I interferons, which further promotes the inflammatory response. B-cell depletion with the CD20 antibody rituximab has provided clinical proof of concept that targeting B cells and the humoral response can result in significant benefit to patients. Consequently, the interest in B-cell targeted therapies has greatly increased in recent years and a number of new biologics exploiting various mechanisms are now in clinical development. This review provides an overview on current developments in the area of B-cell targeted therapies by describing molecules and subpopulations that currently offer themselves as therapeutic targets, the different strategies to target B cells currently under investigation as well as an update on the status of novel therapeutics in clinical development. Emerging data from clinical trials are providing critical insight regarding the role of B cells and autoantibodies in various autoimmune conditions and will guide the development of more efficacious therapeutics and better patient selection.
PMCID: PMC3624127  PMID: 23566679
8.  RAGE inhibits human respiratory syncytial virus syncytium formation by interfering with F-protein function 
The Journal of General Virology  2013;94(Pt 8):1691-1700.
Human respiratory syncytial virus (RSV) is a major cause of severe lower respiratory tract infection. Infection is critically dependent on the RSV fusion (F) protein, which mediates fusion between the viral envelope and airway epithelial cells. The F protein is also expressed on infected cells and is responsible for fusion of infected cells with adjacent cells, resulting in the formation of multinucleate syncytia. The receptor for advanced glycation end products (RAGE) is a pattern-recognition receptor that is constitutively highly expressed by type I alveolar epithelial cells. Here, we report that RAGE protected HEK cells from RSV-induced cell death and reduced viral titres in vitro. RAGE appeared to interact directly with the F protein, but, rather than inhibiting RSV entry into host cells, virus replication and budding, membrane-expressed RAGE or soluble RAGE blocked F-protein-mediated syncytium formation and sloughing. These data indicate that RAGE may contribute to protecting the lower airways from RSV by inhibiting the formation of syncytia, viral spread, epithelial damage and airway obstruction.
PMCID: PMC3749528  PMID: 23559480
9.  Opposing Roles of Membrane and Soluble Forms of the Receptor for Advanced Glycation End Products in Primary Respiratory Syncytial Virus Infection 
The Journal of Infectious Diseases  2012;205(8):1311-1320.
Respiratory syncytial virus (RSV), a common respiratory pathogen in infants and the older population, causes pulmonary inflammation and airway occlusion that leads to impairment of lung function. Here, we have established a role for receptor for advanced glycation end products (RAGE) in RSV infection. RAGE-deficient (ager−/−) mice were protected from RSV-induced weight loss and inflammation. This protection correlated with an early increase in type I interferons, later decreases in proinflammatory cytokines, and a reduction in viral load. To assess the contribution of soluble RAGE (sRAGE) to RSV-induced disease, wild-type and ager−/− mice were given doses of sRAGE following RSV infection. Of interest, sRAGE treatment prevented RSV-induced weight loss and neutrophilic inflammation to a degree similar to that observed in ager−/− mice. Our work further elucidates the roles of RAGE in the pathogenesis of respiratory infections and highlights the opposing roles of membrane and sRAGE in modulating the host response to RSV infection.
PMCID: PMC3308901  PMID: 22262795
10.  CAT-8015: A Second-generation Pseudomonas Exotoxin A-Based Immunotherapy Targeting CD22 -Expressing Hematological Malignancies 
To compare the in vitro and in vivo efficacy of CAT-8015, a second-generation recombinant immunotoxin composed of disulfide linked affinity matured VH and VL chains of the mouse anti-CD22 monoclonal antibody RFB4 fused to PE38, to the parental compound CAT-3888.
Experimental Design
The biological activity of CAT-8015 was examined in vitro using B cell tumor lines and in vivo in a JD38-based subcutaneous tumor model in NCr athymic mice. Pharmacokinetics and interspecies scaling of CAT-8015 were evaluated in mice, rats, and Cynomologus monkeys. The potential toxicity of CAT-8015 was assessed in monkeys in a toxicological study and compared to CAT-3888.
The IC50s of CAT-8015 in vitro using the EHEB, MEC1, Daudi, CA46, and JD38 cell lines ranged from 0.3 - 8.6 ng/mL. Pharmacokinetic studies with CAT-8015 were conducted in mouse, rat and Cynomolgus monkey. The T1/2 was calculated to be 0.42, 0.61, and 0.79 hr and the Vss was 1.37, 5.57, and 140.3 mL in mouse, rat, and monkey, respectively. In vivo, when JD38 tumor-bearing animals were treated with CAT-8015 at doses ≥ 75 μg/kg at 48 hr intervals for a total of 3 doses, a rapid reduction in tumor volume and in some cases complete remission in tumor growth was observed. The comparative toxicological study showed comparable clinical and anatomical pathology changes for CAT-8015 and CAT-3888.
CAT-8015 is a CD22-targeting immunotoxin that, in preclinical studies, has greatly improved efficacy as compared to CAT-3888.
PMCID: PMC2742326  PMID: 19188153
immunotoxin; CLL; NHL; PE-38; apoptosis
11.  Genomic-Based High Throughput Screening Identifies Small Molecules That Differentially Inhibit the Antiviral and Immunomodulatory Effects of IFN-α 
Molecular Medicine  2008;14(7-8):374-382.
Multiple lines of evidence suggest that inhibition of Type I Interferons, including IFN-α, may provide a therapeutic benefit for autoimmune diseases. Using a chemical genomics approach integrated with cellular and in vivo assays, we screened a small compound library to identify modulators of IFN-α biological effects. A genomic fingerprint was developed from both ex vivo patient genomic information and in vitro gene modulation from IFN-α cell-based stimulation. A high throughput genomic-based screen then was applied to prioritize 268 small molecule inhibitors targeting 41 different intracellular signaling pathways. Active compounds were profiled further for their ability to inhibit the activation and differentiation of human monocytes using disease-related stimuli. Inhibitors targeting NF-κB or Janus Kinase/Signal Transducer and Activator of Transcription (JAK/STAT) signaling emerged as “dissociated inhibitors” because they did not modulate IFN-α anti-viral effects against HSV-1 but potently inhibited other immune-related functions. This work describes a novel strategy to identify small molecule inhibitors for the treatment of autoimmune disorders.
PMCID: PMC2376640  PMID: 18475307

Results 1-11 (11)