Clostridium difficile is a leading cause of nosocomial infection in North America and a considerable challenge to healthcare professionals in hospitals and nursing homes. The Gram-positive bacterium produces two exotoxins, toxin A (TcdA) and toxin B (TcdB), which are the major virulence factors responsible for C. difficile-associated disease (CDAD) and are targets for CDAD therapy. In this work, recombinant single-domain antibody fragments (VHHs) which target the cell receptor binding domains of TcdA or TcdB were isolated from an immune, llama phage display library and characterized. Four VHHs (A4.2, A5.1, A20.1, and A26.8) were potent neutralizers of the cytopathic effects of TcdA in an in vitro assay and the neutralizing potency was enhanced when VHHs were administered in combinations. Epitope mapping experiments revealed that some synergistic combinations consisted of VHHs recognizing overlapping epitopes, an indication that factors other than mere epitope blocking are responsible for the increased neutralization. Binding assays revealed TcdA-specific VHHs neutralized TcdA by binding to sites other than the carbohydrate binding pocket of the toxin. The TcdB-specific VHHs failed to neutralize TcdB, as did a panel of human VL antibodies isolated from a synthetic library. To enhance the stability of the C. difficile TcdA-specific VHHs for oral therapeutic applications, the VHHs were expressed with an additional disulfide bond by introducing Ala/Gly54Cys and Ile78Cys mutations. The mutant VHHs were found to be well expressed, were non-aggregating monomers, retained low nM affinity for TcdA, and were capable of in vitro TcdA neutralization. Digestion of the VHHs with the major gastrointestinal proteases, at biologically relevant concentrations, revealed a significant increase in pepsin resistance for all mutants and an increase in chymotrypsin resistance for the majority of mutants without compromising inherent VHH trypsin resistance. Collectively, the second disulfide not only increased VHH thermal stability at neutral pH, as previously shown, but also represents a generic strategy to increase VHH stability at low pH and impart protease resistance. These are all desirable characteristics for the design of protein-based oral therapeutics. In conclusion, llama VHHs represent a class of novel, non-antibiotic inhibitors of infectious disease virulence factors such as C. difficile toxins.

Clostridium difficile is a leading cause of nosocomial infection in North America and a considerable challenge to healthcare professionals in hospitals and nursing homes. The Gram-positive bacterium produces two exotoxins, toxin A (TcdA) and toxin B (TcdB), which are the major virulence factors responsible for C. difficile-associated disease (CDAD) and are targets for CDAD therapy. In this work, recombinant single-domain antibody fragments (VHHs) which target the cell receptor binding domains of TcdA or TcdB were isolated from an immune, llama phage display library and characterized. Four VHHs (A4.2, A5.1, A20.1, and A26.8) were potent neutralizers of the cytopathic effects of TcdA in an in vitro assay and the neutralizing potency was enhanced when VHHs were administered in combinations. Epitope mapping experiments revealed that some synergistic combinations consisted of VHHs recognizing overlapping epitopes, an indication that factors other than mere epitope blocking are responsible for the increased neutralization. Binding assays revealed TcdA-specific VHHs neutralized TcdA by binding to sites other than the carbohydrate binding pocket of the toxin. The TcdB-specific VHHs failed to neutralize TcdB, as did a panel of human VL antibodies isolated from a synthetic library. To enhance the stability of the C. difficile TcdA-specific VHHs for oral therapeutic applications, the VHHs were expressed with an additional disulfide bond by introducing Ala/Gly54Cys and Ile78Cys mutations. The mutant VHHs were found to be well expressed, were non-aggregating monomers, retained low nM affinity for TcdA, and were capable of in vitro TcdA neutralization. Digestion of the VHHs with the major gastrointestinal proteases, at biologically relevant concentrations, revealed a significant increase in pepsin resistance for all mutants and an increase in chymotrypsin resistance for the majority of mutants without compromising inherent VHH trypsin resistance. Collectively, the second disulfide not only increased VHH thermal stability at neutral pH, as previously shown, but also represents a generic strategy to increase VHH stability at low pH and impart protease resistance. These are all desirable characteristics for the design of protein-based oral therapeutics. In conclusion, llama VHHs represent a class of novel, non-antibiotic inhibitors of infectious disease virulence factors such as C. difficile toxins.

Multiple sclerosis is a neurodegenerative disorder affecting the central nervous system (CNS). Currently, the disease is incurable and immunomodulating drugs are the only option to control the disease. CD49d is an adhesion receptor expressed on most immune cells. Antibodies that bind to CD49d and block immune cells from trafficking toward the CNS are being pursued as one class of therapeutics. In this work, by combining recombinant antibody and phage display technologies we isolated 10 anti-CD49d single domain antibodies from a synthetic antibody light chain variable domain (VL) phage display library. Isolated VLs (~ 12 kDa) were expressed in Escherichia coli, purified and analysed for biophysical characteristics. The majority were expressed in good yields and were non-aggregating. All 10 VLs bound recombinant CD49d by ELISA, and 7 bound to CD49d-expressing cells in flow cytometry experiments. To empower the VLs for better therapeutic efficacy (thru increasing avidity and half-life), three of the lead VLs were re-engineered as fusions to fragment crystallisable (Fc) of human immunoglobulin gamma (IgG). The engineered hFc-VL fragments (~ 70 – 90 kDa) retained their specificity for CD49d by flow cytometry. With (i) being less immunogenic due to their human nature, (ii) their efficient access to cryptic epitopes (iii) having half-lives comparable to IgGs’ and (iv) being more cost effective compared to IgGs, these novel antibody fragments (monovalent VLs and bivalent hFc-VLs) provide a promising therapeutic platform against multiple sclerosis.

Gender of animal offspring is of great interest to farmers where gender selection is achieved via the separation of male-bearing from female-bearing sperms prior to performing artificial insemination. A start-up company (Ab Biotech Inc.) has developed a technique for gender selection based on the production of an intracellular single-domain antibody (sdAb) using the bacterium Escherichia coli capable of sexing bovine sperm. The purpose of this research was to provide a recommendation to Ab Biotech Inc. for the lysis of E. coli. An efficient lysis technique was required in order to release the intracellular sdAb. In the dairy industry, sexing for female calves is preferred since male calves are not useful for the purpose of milk production. Multiple lysis techniques were tested in order to provide a feasible recommendation for Ab Biotech Inc. These techniques included high pressure homogenization, sonication, bead milling and enzymatic/chemical lysis using lysozymes and Triton X-100. Required lysis time, extent of lysis and potential operating costs were contributing factors for determining an optimal technique. The extent of lysis was determined by quantifying the total amount of released protein using SDS-PAGE densitometry. It was recommended to choose bead milling for potential process upscaling since a large amount of fractional lysis (0.70) was obtained over a short amount of lysis time (3 min) with an inexpensive ($9.50/kg) 0.3 mm mixture of glass beads.

No description available.

Au cours de sa vie, 1 femme sur 9 sera atteinte du cancer du sein, 1 sur 27 sera emportée par cette maladie et 10 à 15 % des patientes développeront des métastases dans les trois années suivant le diagnostic. Le diagnostic précis et personnalisé du cancer du sein ainsi que l'évaluation de son potentiel métastatique est donc un enjeu majeur. Une analyse plus précise des caractéristiques moléculaires d'une tumeur primaire devrait conduire à une médecine personnalisée, un traitement et un suivi plus efficace. La détection de biomarqueurs sériques serait un moyen de diagnostiquer un cancer métastatique. Dans le but de découvrir de nouveaux marqueurs, l'analyse protéomique d'échantillons de patient a un fort potentiel mais souffre de limitations techniques, incluant le manque d'anticorps stables reconnaissant des marqueurs tumoraux d'intérêt. Par l'utilisation de fragments d'anticorps aux propriétés remarquables nommé single domain antibody (sdAb), et grâce à la mise au point d'une stratégie innovante de phages display, ce travail apporte d'importantes réponses en termes de disponibilité d'anticorps, d'analyse spécifique d'échantillon et de découverte de nouvelles cibles. Nous avons élaboré une stratégie permettant la découverte de biomarqueurs et l'isolement des anticorps correspondants. Après la construction de banques de sdAb à partir de lamas immunisés par des biopsies, une nouvelles stratégie de sélection in vitro par phage display, la sélection masquée, nous a permis d'isoler des anticorps spécifiques du cancer du sein. / In a lifetime, 1 in 9 women will develop breast cancer, 1 of 27 will be swept away by the disease and from 10 to 15% of patients will develop metastases within three years of diagnosis. Accurate and personalized diagnosis of breast cancer and the detection of its metastatic potential is a major challenge. It is essential to develop new analytical methods allowing an effective monitoring of breast cancer. A closer analysis of the molecular characteristics of a primary tumor should lead to more effective personalized medicine, treatment and monitoring. The efficient detection of serum biomarkers would be a way to diagnose metastatic cancer and to modify treatment based on these results. Toward this goal, the proteomic analysis of patient samples has great potential but suffers from technical limitations, including the lack of a wide variety of antibodies and tumor marker. By the use of innovative antibody fragments with remarkable properties named single domain antibody (sdAb), and through the development of a new innovative strategy of phage display, this work provides important answers in terms of availability of antibody, specific proteomic analysis of sample and new target discovery. We have developed a strategy allowing the simultaneous discovery of new biomarkers and the isolation of corresponding antibodies. After the construction of sdAb libraries from llamas immunized with biopsies, and using a new in vitro selection strategy by phage display named masked selection, we have isolated breast cancer-specific antibodies.

In the present study, two insulin-like growth factor-binding protein 7 (IGFBP7) C-terminal-peptides were expressed as fusion proteins to bacterial verotoxin pentamerization domain as shown by Western blotting, ELISA and mass spectroscopy. Both in vivo-biotinylated recombinant products were purified from bacterial lysates by IMAC and used directly for panning along with the recombinant IGFBP7 protein using the LAC-M Camelidae naïve single domain antibody (sdAb) library. Target-specific sdAbs to both parental protein and peptide fusions were identified by phage ELISA. Twelve different clones were isolated by phage-ELISA screening and their sdAb genes were sequenced. Soluble sdAbs and their pentameric formats were expressed in TG1 E. coli, purified by IMAC and characterized by ELISA and SPR. Several sdAbs are currently under study, however anti-IGFBP7 (P12/M12) was extensively characterized and exhibited promising anti-tumorigenic effect on PANC-1 cell lines by blocking IGFBP7 promoting activity. This study provides the basis for developing a novel imaging/therapeutic reagent for targeting and treating brain tumor angiogenesis in early stages of tumorogenesis and can also be used as a molecular tool to monitor the degree of angiogenesis in gliomas which may help to improve the clinical management of brain tumors.

In the present study, two insulin-like growth factor-binding protein 7 (IGFBP7) C-terminal-peptides were expressed as fusion proteins to bacterial verotoxin pentamerization domain as shown by Western blotting, ELISA and mass spectroscopy. Both in vivo-biotinylated recombinant products were purified from bacterial lysates by IMAC and used directly for panning along with the recombinant IGFBP7 protein using the LAC-M Camelidae naïve single domain antibody (sdAb) library. Target-specific sdAbs to both parental protein and peptide fusions were identified by phage ELISA. Twelve different clones were isolated by phage-ELISA screening and their sdAb genes were sequenced. Soluble sdAbs and their pentameric formats were expressed in TG1 E. coli, purified by IMAC and characterized by ELISA and SPR. Several sdAbs are currently under study, however anti-IGFBP7 (P12/M12) was extensively characterized and exhibited promising anti-tumorigenic effect on PANC-1 cell lines by blocking IGFBP7 promoting activity. This study provides the basis for developing a novel imaging/therapeutic reagent for targeting and treating brain tumor angiogenesis in early stages of tumorogenesis and can also be used as a molecular tool to monitor the degree of angiogenesis in gliomas which may help to improve the clinical management of brain tumors.

Despite the progress made in cancer research, cancer remains one of the leading causes of death worldwide. Although the development of new cancer treatments has improved cancer patients' survival rate, a significant number of patients experience refractory and recurrence events with serious side effects. It is known that the immune system actively participates in eliminating cancer. However, cancer cells can develop mechanisms to evade the immune system resulting in immunotolerance. Immunotherapy aids the patient's immune system's ability to recognize and eliminate cancer cells. During the last three decades, immunotherapy has gradually emerged as an effective and more specific approach to treat cancer. Particularly monoclonal antibodies and adoptive cell therapies such as chimeric antigen receptor (CAR) T-cells have proven highly effective. Nevertheless, the success of these novel therapies depends on discovering suitable tumor targets. Recently, we reported localization of Thymidine Kinase 1 (TK1) to the plasma membrane of certain cancer cells but have not found such localization on normal cells. Similarly, another nucleotide salvage pathway enzyme Hypoxanthine Guanine Phosphoribosyltransferase (HPRT), has also been reported to be localized to the plasma membrane of certain cancer cells. Thus, TK1 and HPRT membrane-associated forms can be potential tumor targets for cancer immunotherapy. This dissertation describes the immunotargeting of TK1 for the selective elimination of tumor cells and the surface localization of HPRT on the plasma membrane of cancer cells. Using hybridoma and phage display technologies, we developed monoclonal antibodies (mAb) and isolated human single domain antibodies (sdAb) specific to human TK1. We confirmed that antibodies and sdAbs could target TK1 on the plasma membrane of lung, breast and colon cancer cells, but not on healthy cells. In addition, we demonstrated that cancer cells expressing membrane-associated TK1 (mTK1) co-cultured with human mononuclear cells (MNC) were selectively eliminated through antibody-dependent cell-mediated cytotoxicity (ADCC) when anti-TK1 mAbs were added. Furthermore, we designed novel TK1 specific tumor targeting receptors and expressed them in human T cells and human macrophages. Finally, we proposed using both TK1 and HPRT as biomarkers for the early detection and monitoring of follicular lymphoma (FL), a disease that is usually detected at advanced stages. The knowledge generated from the data presented in this dissertation indicates that TK1 and HPRT may be suitable immunotherapeutic targets for antibody-based and adoptive cell-based therapies against both liquid and solid malignancies. It also proposes the incorporation of TK1 and HPRT as molecular biomarkers for the early detection and monitoring of FL.

A steady-state computational model for a proton exchange membrane fuel cell (PEMFC) is presented. The model accounts for species transport, electrochemical kinetics, energy transport, current distribution, water uptake and release within the polymer portion of the catalyst layers, and liquid water production and transport. Both two-dimensional and three-dimensional geometries are modeled. For a given geometry, the governing differential equations are solved over a single computational domain. For the two-dimensional model, the solution domain includes a gas channel, gas diffusion layer, and catalyst layer for both the anode and cathode sides of the cell as well as the solid polymer membrane. For the three-dimensional model the current collectors are also modeled on both the anode and cathode sides of the fuel cell. The model for the catalyst layers is based on an agglomerate geometry, which requires water species to exist in dissolved, gaseous, and liquid forms simultaneously. Data related to catalyst layer morphology that was required by the model was obtained via a physical analysis of both commercially available and in-house membrane electrode assemblies (MEA). Analysis techniques including cyclic voltammetry and electron microscopy were used. The coupled set of partial differential equations is solved sequentially over a single solution domain with the commercial computational fluid dynamics (CFD) solver, CFDesign™ and is readily adaptable with respect to geometry and material property definitions. A fuel cell test stand was designed and built to facilitate experimental validation of the model. The test stand is capable of testing cells up to 50 cm2 under a variety of controlled conditions. Model results for both two and three-dimensional fuel cell geometries are presented. Parametric studies performed with the model are also presented and illustrate how fuel cell performance varies due to changes in parameters associated with the transport of reactants and liquid water produced in the cell. In particular, the transport of oxygen, water within the polymer portions of the catalyst layers and membrane, and liquid water within the porous regions of the cell are shown to have significant impact on cell performance, especially at low cell voltage. Parametric studies also address the sensitivity of the model results to certain physical properties, which illustrates the importance of accurately determining the physical properties of the fuel cell components on which the model is based. The results from the three-dimensional model illustrate the impact of the collector plate shoulders (for a conventional flowfield) on oxygen transport and the distribution of current production within the cell. / Ph. D.