Scott K Dessain

Lankenau Institute for Medical Research, Wynnewood, Oklahoma, United States

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Publications (25)176.42 Total impact

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    ABSTRACT: An essential requirement for eradication of poliomyelitis is the elimination of circulating vaccine derived polioviruses (cVDPV) and polioviruses excreted by chronically infected individuals with immunodeficiencies (iVDPV). As part of a post-eradication risk management strategy, a human monoclonal antibody (mAb) therapeutic could play a role in halting excretion in asymptomatic carriers and could be used, in combination with vaccines and antiviral drugs, to protect polio-exposed individuals. Cross-neutralizing mAbs may be particularly useful, as they would reduce the number of mAbs needed to create a comprehensive PV therapeutic. We cloned a panel of IgG mAbs from OPV-vaccinated, IPV-boosted healthy subjects. Many of the mAbs had potent neutralizing activities against PV wild-type (WT) and Sabin strains, and two of the mAbs, 12F8 and 1E4, were significantly cross-reactive against types 1 and 2 and types 1 and 3, respectively. Mapping the binding epitopes using strains resistant to neutralization (escape mutants) suggested that cross-specific PV binding epitopes may primarily reside within the canyon region, which interacts with the cellular receptor molecule CD155 and the cross-neutralizing chimpanzee/human mAb, A12. Despite their close proximity, the epitopes for the 12F8 and 1E4 mAbs on Sabin 1 were not functionally identical to the A12 epitope. When tested together, 12F8 and 1E4 neutralized a diverse panel of clinically relevant PV strains and did not exhibit interference. Virus mutants resistant to the anti-poliovirus drug V-073 were also neutralized by the mAbs. The 12F8 and 1E4 mAbs may suitable for use as anti-PV therapeutics.
    Antiviral research 05/2014; · 3.61 Impact Factor
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    ABSTRACT: Immune complexes formed between monoclonal antibodies (mAbs) and toxins can neutralize toxicity in vivo by multiple mechanisms. Toxin sequestration and clearance by mAbs may be improved by enhancing their ability to bind to red blood cells (RBCs) through immune adherence. This can be achieved by converting the mAbs to heteropolymers (HPs), which are antigen-specific mAbs cross-linked to mAbs targeting the complement receptor (CR1), a protein that is expressed on the surface of RBCs in primates and mediates delivery of complement C3b-containing immune complexes to tissue macrophages. Conversion of mAbs to HPs has been shown to enhance clearance of multivalent antigens from the blood circulation, but the interaction of HPs with monovalent toxins has not been examined. Using botulinum neurotoxin (BoNT) as a model system, we studied the effect of conversion of a pair of BoNT-specific mAbs into HPs on toxin neutralization and handling in vivo. Two HPs given in combination had 166-fold greater potency than un-modified mAbs, neutralizing 5000 LD50 BoNT, when tested in transgenic mice expressing human CR1 on RBC membranes. Improvement required adherence of BoNT to the RBC in vivo and 2 HPs, rather than an HP+mAb pair. The HP pair bound BoNT to RBCs in the circulation for 2h, in comparison to BoNT-neutralizing anti-serum, which induced no detectable RBC binding. HP pairs exhibited enhanced uptake by peritoneal macrophages in vitro, compared to pairs of mAbs or mAb+HP pairs. In a post-exposure therapeutic model, HPs gave complete protection from a lethal BoNT dose up to 3h after toxin exposure. In a pre-exposure prophylaxis model, mice given HP up to 5 days prior to BoNT administration were fully protected from a lethal BoNT dose. These studies elucidate general mechanisms for the neutralization of toxins by HP pairs and demonstrate the potential utility of HPs as BoNT therapeutics.
    Molecular Immunology 10/2013; 57(2):247-254. · 3.00 Impact Factor
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    ABSTRACT: Botulinum neurotoxin (BoNT) is produced by Clostridium botulinum and associates with nontoxic neurotoxin-associated proteins to form high-molecular weight progenitor complexes (PCs). The PCs are required for the oral toxicity of BoNT in the context of food-borne botulism and are thought to protect BoNT from destruction in the gastrointestinal tract and aid in absorption from the gut lumen. The PC can differ in size and protein content depending on the C. botulinum strain. The oral toxicity of the BoNT PC increases as the size of the PC increases, but the molecular architecture of these large complexes and how they contribute to BoNT toxicity have not been elucidated. We have generated 2D images of PCs from strains producing BoNT serotypes A1, B, and E using negative stain electron microscopy and single-particle averaging. The BoNT/A1 and BoNT/B PCs were observed as ovoid-shaped bodies with three appendages, whereas the BoNT/E PC was observed as an ovoid body. Both the BoNT/A1 and BoNT/B PCs showed significant flexibility, and the BoNT/B PC was documented as a heterogeneous population of assembly/disassembly intermediates. We have also determined 3D structures for each serotype using the random conical tilt approach. Crystal structures of the individual proteins were placed into the BoNT/A1 and BoNT/B PC electron density maps to generate unique detailed models of the BoNT PCs. The structures highlight an effective platform that can be engineered for the development of mucosal vaccines and the intestinal absorption of oral biologics.
    Proceedings of the National Academy of Sciences 03/2013; · 9.81 Impact Factor
  • Minal Dhamankar, Scott K Dessain
    Clinical advances in hematology & oncology: H&O 04/2012; 10(4):262-5.
  • Alzheimer's and Dementia 07/2011; 7(4). · 17.47 Impact Factor
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    ABSTRACT: Botulinum neurotoxin (BoNT) potently inhibits cholinergic signaling at the neuromuscular junction. The ideal countermeasures for BoNT exposure are monoclonal antibodies or BoNT antisera, which form BoNT-containing immune complexes that are rapidly cleared from the general circulation. Clearance of opsonized toxins may involve complement receptor-mediated immunoadherence to red blood cells (RBC) in primates or to platelets in rodents. Methods of enhancing immunoadherence of BoNT-specific antibodies may increase their potency in vivo. We designed a novel fusion protein (FP) to link biotinylated molecules to glycophorin A (GPA) on the RBC surface. The FP consists of an scFv specific for murine GPA fused to streptavidin. FP:mAb:BoNT complexes bound specifically to the RBC surface in vitro. In a mouse model of BoNT neutralization, the FP increased the potency of single and double antibody combinations in BoNT neutralization. A combination of two antibodies with the FP gave complete neutralization of 5,000 LD50 BoNT in mice. Neutralization in vivo was dependent on biotinylation of both antibodies and correlated with a reduction of plasma BoNT levels. In a post-exposure model of intoxication, FP:mAb complexes gave complete protection from a lethal BoNT/A1 dose when administered within 2 hours of toxin exposure. In a pre-exposure prophylaxis model, mice were fully protected for 72 hours following administration of the FP:mAb complex. These results demonstrate that RBC-targeted immunoadherence through the FP is a potent enhancer of BoNT neutralization by antibodies in vivo.
    PLoS ONE 03/2011; 6(3):e17491. · 3.53 Impact Factor
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    ABSTRACT: The emergence of a novel strain of pandemic influenza (pH1N1) in 2009 presented significant challenges to health care facilities worldwide. In our academic community medical center in suburban Philadelphia, we noted our first pH1N1 diagnosis in September 2009. We sought to assess the impact of pH1N1 disease on our hospitalized patient population. We prospectively collected clinical and epidemiological data on 29 consecutive patients that were admitted to our hospital with a primary or secondary diagnosis of influenza from October 1-November 30, 2009. Data were obtained through care of the patients and chart review. Prominent symptoms on admission included fever, hypoxia, cough, myalgias, and diarrhea, with leukocytosis and neutrophilia. Pre-existing medical conditions included asthma, pregnancy, immunosuppressive therapy, and sickle cell disease. All but 5 of the patients were under 60 years of age. Three patients had culture-documented bacterial or mycoplasma infections. All but two of the patients received oseltamivir. Six required admission to the intensive care unit but only one patient died. Our population of hospitalized patients with novel pH1N1 influenza demonstrated many of the features that have been associated with pH1N1 disease in other populations. Most of the patients were women and none of the patients died directly as a complication of influenza. We observed a cluster of patients with a tetrad of features comprising a history of asthma, obesity, female gender, and African-American race. Individuals with this constellation of factors should be specifically targeted for pH1N1 vaccination.
    The Open Respiratory Medicine Journal 01/2011; 5:19-23.
  • Alzheimer's and Dementia 07/2010; 6(4). · 17.47 Impact Factor
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    ABSTRACT: We have previously shown that a subpopulation of naturally occurring human IgGs were cross-reactive against conformational epitopes on pathologic aggregates of Abeta, a peptide that forms amyloid fibrils in the brains of patients with Alzheimer disease, inhibited amyloid fibril growth, and dissociated amyloid in vivo. Here, we describe similar anti-amyloidogenic activity that is a general property of free human Ig gamma heavy chains. A gamma(1) heavy chain, F1, had nanomolar binding to an amyloid fibril-related conformational epitope on synthetic oligomers and fibrils as well as on amyloid-laden tissue sections. F1 did not bind to native Abeta monomers, further indicating the conformational nature of its binding site. The inherent anti-amyloidogenic activity of Ig gamma heavy chains was demonstrated by nanomolar amyloid fibril and oligomer binding by polyclonal and monoclonal human heavy chains that were isolated from inert or weakly reactive antibodies. Most importantly, the F1 heavy chain prevented in vitro fibril growth and reduced in vivo soluble Abeta oligomer-induced impairment of rodent hippocampal long term potentiation, a cellular mechanism of learning and memory. These findings demonstrate that free human Ig gamma heavy chains comprise a novel class of molecules for developing potential therapeutics for Alzheimer disease and other amyloid disorders. Moreover, establishing the molecular basis for heavy chain-amyloidogenic conformer interactions should advance understanding on the types of interactions that these pathologic assemblies have with biological molecules.
    Journal of Biological Chemistry 11/2009; 285(2):1066-74. · 4.60 Impact Factor
  • Alzheimer's and Dementia 07/2009; 5(4). · 17.47 Impact Factor
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    ABSTRACT: A severe form of encephalitis associated with antibodies against NR1-NR2 heteromers of the NMDA receptor was recently identified. We aimed to analyse the clinical and immunological features of patients with the disorder and examine the effects of antibodies against NMDA receptors in neuronal cultures. We describe the clinical characteristics of 100 patients with encephalitis and NR1-NR2 antibodies. HEK293 cells ectopically expressing single or assembled NR1-NR2 subunits were used to determine the epitope targeted by the antibodies. Antibody titres were measured with ELISA. The effect of antibodies on neuronal cultures was determined by quantitative analysis of NMDA-receptor clusters. Median age of patients was 23 years (range 5-76 years); 91 were women. All patients presented with psychiatric symptoms or memory problems; 76 had seizures, 88 unresponsiveness (decreased consciousness), 86 dyskinesias, 69 autonomic instability, and 66 hypoventilation. 58 (59%) of 98 patients for whom results of oncological assessments were available had tumours, most commonly ovarian teratoma. Patients who received early tumour treatment (usually with immunotherapy) had better outcome (p=0.004) and fewer neurological relapses (p=0.009) than the rest of the patients. 75 patients recovered or had mild deficits and 25 had severe deficits or died. Improvement was associated with a decrease of serum antibody titres. The main epitope targeted by the antibodies is in the extracellular N-terminal domain of the NR1 subunit. Patients' antibodies decreased the numbers of cell-surface NMDA receptors and NMDA-receptor clusters in postsynaptic dendrites, an effect that could be reversed by antibody removal. A well-defined set of clinical characteristics are associated with anti-NMDA-receptor encephalitis. The pathogenesis of the disorder seems to be mediated by antibodies.
    The Lancet Neurology 11/2008; 7(12):1091-8. · 21.82 Impact Factor
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    ABSTRACT: The affinity-matured human antibody repertoire may be ideal as a source for antibody therapeutics against infectious diseases and bioterror agents. Hybridoma methods for cloning these antibodies have many potential advantages, including convenience, high-yield antibody expression, and the ability to capture the antibodies in their native configurations. However, they have been hindered by hybridoma instability and limited accessibility of antigen-specific, class-switched human B-cells. Here, we describe an efficient, three-step method that uses human peripheral blood B-cells to produce stable hybridoma populations that are highly-enriched for affinity-matured human IgG antibodies. Peripheral blood mononuclear cells (PBMCs) are (a) selected for expression of CD27, a marker of post-germinal center B-cells, (b) cultured in vitro to promote B-cell proliferation and class-switching, and (c) fused to a genetically modified myeloma cell line. Using this strategy, we cloned 5 IgG antibodies that bind botulinum neurotoxins (BoNT), the causes of the food-borne paralytic illness, botulism, and Category A Select Bioterror agents. Two of these antibodies bind BoNT with low picomolar affinities. One (30B) is the first high-affinity human antibody to bind serotype B BoNT, and another (6A) is able to neutralize a lethal dose of serotype A BoNT in vivo in pre- and post-exposure models. This optimized hybridoma method will broadly enable access to the native human antibody repertoire.
    Journal of Immunological Methods 05/2008; 333(1-2):156-66. · 2.01 Impact Factor
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    ABSTRACT: Affinity-matured human antibodies have demonstrated efficacy as countermeasures for exposure to botulinum neurotoxin (BoNT), which is the cause of the disease botulism category A select bioterror agent. Little is known, however, about the potential role of natural (un-mutated) antibodies in the protective immune response to BoNT. Here we describe the cloning of two human IgM antibodies that bind serotype A BoNT. Both are un-mutated IgM antibodies, consistent with an origin in naive B cells. One of the antibodies is able to fully neutralize a lethal dose of serotype A BoNT in vivo. These results suggest that the natural human antibody repertoire may play a role in protection from exposure to biological toxins.
    Hybridoma (2005) 04/2008; 27(2):65-9. · 0.24 Impact Factor
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    ABSTRACT: Monoclonal antibodies have demonstrated significant potential as therapeutics for botulinum neurotoxin exposures. We previously described a hybridoma method for cloning native human antibodies that uses a murine myeloma cell line that ectopically expresses the human telomerase catalytic subunit gene (hTERT) and the murine interleukin-6 gene (mIL-6). Here we describe a heterohybridoma cell line that ectopically expresses mIL-6 and hTERT and has improved stability of hTERT expression. We fused this cell line to human peripheral blood B cells from a subject who had received the botulinum toxoid vaccine, cloning a high-affinity antibody (13A) specific for serotype A botulinum neurotoxin (BoNT/A). The 13A antibody is an affinity-matured, post-germinal center IgG(1) lambda antibody that has partial neutralization activity in vivo. 13A binds an epitope on BoNT/A that overlaps the binding epitope of an IgG antibody previously shown to fully neutralize a lethal dose of BoNT/A in vivo. The 13A antibody may be useful for diagnostic testing or for incorporation into an oligoclonal therapeutic to counteract BoNT/A exposure.
    Hybridoma (2005) 03/2008; 27(1):11-7. · 0.24 Impact Factor
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    ABSTRACT: Botulinum neurotoxins (BoNT) are a family of category A select bioterror agents and the most potent biological toxins known. Cloned antibody therapeutics hold considerable promise as BoNT therapeutics, but the therapeutic utility of antibodies that bind the BoNT light chain domain (LC), a metalloprotease that functions in the cytosol of cholinergic neurons, has not been thoroughly explored. We used an optimized hybridoma method to clone a fully human antibody specific for the LC of serotype A BoNT (BoNT/A). The 4LCA antibody demonstrated potent in vivo neutralization when administered alone and collaborated with an antibody specific for the HC. In Neuro-2a neuroblastoma cells, the 4LCA antibody prevented the cleavage of the BoNT/A proteolytic target, SNAP-25. Unlike an antibody specific for the HC, the 4LCA antibody did not block entry of BoNT/A into cultured cells. Instead, it was taken up into synaptic vesicles along with BoNT/A. The 4LCA antibody also directly inhibited BoNT/A catalytic activity in vitro. An antibody specific for the BoNT/A LC can potently inhibit BoNT/A in vivo and in vitro, using mechanisms not previously associated with BoNT-neutralizing antibodies. Antibodies specific for BoNT LC may be valuable components of an antibody antidote for BoNT exposure.
    PLoS ONE 02/2008; 3(8):e3023. · 3.53 Impact Factor
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    ABSTRACT: Rabies, being a major zoonotic disease, significantly impacts global public health. It is invariably fatal once clinical signs are apparent. The majority of human rabies deaths occur in developing countries. India alone reports more than 50% of the global rabies deaths. Although it is a vaccine-preventable disease, effective rabies prevention in humans with category III bites requires the combined administration of rabies immunoglobulin (RIG) and vaccine. Cell culture rabies vaccines have become widely available in developing countries, virtually replacing the inferior and unsafe nerve tissue vaccines. Limitations inherent to the conventional RIG of either equine or human origin have prompted scientists to look for monoclonal antibody-based human RIG as an alternative. Fully human monoclonal antibodies have been found to be safer and equally efficacious than conventional RIG when tested in mice and hamsters. In this chapter, rabies epidemiology, reservoir control measures, post-exposure prophylaxis of human rabies, and combination therapy for rabies are discussed. Novel human monoclonal antibodies, their production, and the significance of plants as expression platforms are emphasized.
    Current topics in microbiology and immunology 02/2008; 317:67-101. · 3.47 Impact Factor
  • S K Dessain, S P Adekar, J D Berry
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    ABSTRACT: Native human antibodies are defined as those that arise naturally as the result of the functioning of an intact human immune system. The utility of native antibodies for the treatment of human viral diseases has been established through experience with hyperimmune human globulins. Native antibodies, as a class, differ in some respects from those obtained by recombinant library methods (phage or transgenic mouse) and possess distinct properties that may make them ideal therapeutics for human viral diseases. Methods for cloning native human antibodies have been beset by technical problems, yet many antibodies specific for viral antigens have been cloned. In the present review, we discuss native human antibodies and ongoing improvements in cloning methods that should facilitate the creation of novel, potent antiviral therapeutics obtained from the native human antibody repertoire.
    Current topics in microbiology and immunology 02/2008; 317:155-83. · 3.47 Impact Factor
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    ABSTRACT: Currently, an in vivo model of human breast cancer metastasizing from the orthotopic site to bone does not exist, making it difficult to study the many steps of skeletal metastasis. Moreover, models used to identify the mechanisms by which breast cancer metastasizes to bone are limited to intracardiac injection, which seeds the cancer cells directly into the circulation, thus bypassing the early steps in the metastatic process. Such models do not reflect the full process of metastasis occurring in patients. We have developed an animal model of breast cancer metastasis in which the breast cancer cells and the bone target of osteotropic metastasis are both of human origin. The engrafted human bone is functional, based on finding human IgG in the mouse bloodstream, human B cells in the mouse spleen, and normal bone histology. Furthermore, orthotopic injection of a specific human breast cancer cell line, SUM1315 (derived from a metastatic nodule in a patient), later resulted in both bone and lung metastases. In the case of bone, metastasis was to the human implant and not the mouse skeleton, indicating a species-specific osteotropism. This model replicates the events observed in patients with breast cancer skeletal metastases and serves as a useful and relevant model for studying the disease.
    Cancer Research 08/2005; 65(14):6130-8. · 9.28 Impact Factor
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    ABSTRACT: The native human antibody repertoire holds unexplored potential for the development of novel monoclonal antibody therapeutics. Current techniques that fuse immortal cells and primary B-lymphocytes are sub-optimal for the routine production of hybridomas that secrete human monoclonal antibodies. We have found that a murine cell line that ectopically expresses murine interleukin-6 (mIL-6) and human telomerase (hTERT) efficiently forms stable human antibody-secreting heterohybridomas through cell fusion with primary human B-lymphocytes. The hybrid cells maintain secretion of human antibodies derived from the primary B-lymphocytes through multiple rounds of cloning. Using splenic B-lymphocytes from a patient immunized with a Streptococcus pneumoniae capsular polysaccharide vaccine, we have succeeded in creating hybridomas that secrete human monoclonal antibodies specific for S. pneumoniae antigens. Using peripheral blood lymphocytes, we have similarly cloned a human antibody that binds a viral antigen. These experiments establish that SP2/0-derived cell lines ectopically expressing mIL-6 and hTERT will enable the rapid cloning of native human monoclonal antibodies.
    Journal of Immunological Methods 09/2004; 291(1-2):109-22. · 2.01 Impact Factor
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    ABSTRACT: While it is clear that cancer arises from the accumulation of genetic mutations that endow the malignant cell with the properties of uncontrolled growth and proliferation, the precise combinations of mutations that program human tumor cell growth remain unknown. The study of the transforming proteins derived from DNA tumor viruses in experimental models of transformation has provided fundamental insights into the process of cell transformation. We recently reported that coexpression of the simian virus 40 (SV40) early region (ER), the gene encoding the telomerase catalytic subunit (hTERT), and an oncogenic allele of the H-ras gene in normal human fibroblast, kidney epithelial, and mammary epithelial cells converted these cells to a tumorigenic state. Here we show that the SV40 ER contributes to tumorigenic transformation in the presence of hTERT and oncogenic H-ras by perturbing three intracellular pathways through the actions of the SV40 large T antigen (LT) and the SV40 small t antigen (ST). LT simultaneously disables the retinoblastoma (pRB) and p53 tumor suppressor pathways; however, complete transformation of human cells requires the additional perturbation of protein phosphatase 2A by ST. Expression of ST in this setting stimulates cell proliferation, permits anchorage-independent growth, and confers increased resistance to nutrient deprivation. Taken together, these observations define the elements of the SV40 ER required for the transformation of human cells and begin to delineate a set of intracellular pathways whose disruption, in aggregate, appears to be necessary to generate tumorigenic human cells.
    Molecular and Cellular Biology 05/2002; 22(7):2111-23. · 5.04 Impact Factor

Publication Stats

2k Citations
176.42 Total Impact Points


  • 2008–2014
    • Lankenau Institute for Medical Research
      Wynnewood, Oklahoma, United States
    • Thomas Jefferson University
      • Cardeza Foundation for Hematologic Research
      Philadelphia, Pennsylvania, United States
  • 2000–2004
    • Whitehead Institute for Biomedical Research
      Cambridge, Massachusetts, United States
  • 2002
    • Harvard Medical School
      Boston, Massachusetts, United States