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Johannesburg, South Africa

Sixholo J.,Onderstepoort Veterinary Institute | Sixholo J.,University of Pretoria | Van Wyngaardt W.,Onderstepoort Veterinary Institute | Mashau C.,Onderstepoort Veterinary Institute | And 4 more authors.
Biologicals | Year: 2011

Recombinant antibodies can be engineered to improve their binding or other characteristics. A chicken single chain variable fragment (scFv) phage display library was panned against the mycobacterial 16 kDa antigen. Three fusion phages which bound specifically to the antigen were selected, each of which produced low signals in ELISA when secreted as a soluble scFv. One scFv was therefore chosen to be modified in an attempt to improve its binding. Firstly, a mutant sublibrary was created by random mutagenesis. High stringency panning of this sublibrary yielded binders which produced ELISA signals up to eleven times higher than the parent scFv. An increase in the intrinsic affinity was confirmed by surface plasmon resonance. Secondly, the flexible linker between the heavy and light chains of the parent scFv was either shortened to one glycine residue or deleted entirely. No ELISA signal was obtained when the linker was absent, but the glycine-linked scFv showed enhanced binding. Size exclusion chromatography revealed that the enhanced binder had aggregated to form tetramers. This study confirms that the strategies used to improve the binding of human and mouse scFvs can also enhance chicken scFvs. © 2011 The International Association for Biologicals. Source


Lee N.,University of Queensland | Lee N.,University of Sydney | Gatton M.L.,Queensland Institute of Medical Research | Pelecanos A.,Queensland Institute of Medical Research | And 6 more authors.
Journal of Clinical Microbiology | Year: 2012

Rapid diagnostic tests (RDTs) represent important tools to diagnose malaria infection. To improve understanding of the variable performance of RDTs that detect the major target in Plasmodium falciparum, namely, histidine-rich protein 2 (HRP2), and to inform the design of better tests, we undertook detailed mapping of the epitopes recognized by eight HRP-specific monoclonal antibodies (MAbs). To investigate the geographic skewing of this polymorphic protein, we analyzed the distribution of these epitopes in parasites from geographically diverse areas. To identify an ideal amino acid motif for a MAb to target in HRP2 and in the related protein HRP3, we used a purpose-designed script to perform bioinformatic analysis of 448 distinct gene sequences from pfhrp2 and from 99 sequences from the closely related gene pfhrp3. The frequency and distribution of these motifs were also compared to the MAb epitopes. Heat stability testing of MAbs immobilized on nitrocellulose membranes was also performed. Results of these experiments enabled the identification of MAbs with the most desirable characteristics for inclusion in RDTs, including copy number and coverage of target epitopes, geographic skewing, heat stability, and match with the most abundant amino acid motifs identified. This study therefore informs the selection of MAbs to include in malaria RDTs as well as in the generation of improved MAbs that should improve the performance of HRP-detecting malaria RDTs. Copyright © 2012, American Society for Microbiology. All Rights Reserved. Source


Germishuizen W.A.,National Bioproducts Institute | Gyure D.C.,National Bioproducts Institute | Stubbings D.,National Bioproducts Institute | Burnouf T.,Taipei Medical University
Biologicals | Year: 2014

Polyvalent immunoglobulin G (IgG) products obtained by fractionation of human plasma are used to treat a broad range of conditions, including immunodeficiency syndromes and autoimmune, inflammatory, and infectious diseases. Recent incidences of increased thromboembolic events (TEEs) associated with intravenous (IV) IgG (IVIG) led to recalls of some products and increased regulatory oversight of manufacturing processes in order to ensure that products are essentially free of procoagulant/thrombogenic plasma protein contaminants. Laboratory investigations have now identified activated factor XI (FXIa) as the likely causative agent of IVIG-related TEEs. Quantification of the thrombogenic potential is becoming a requirement made to fractionators (a) to validate the capacity of IVIG and subcutaneous IgG manufacturing processes to remove procoagulant contaminants and (b) to establish the safety of the final products. However, in the absence of a recommended test by the main regulatory authorities, several analytical approaches have been evaluated by fractionators, regulators, and university groups. This review focuses on the scientific rationale, merits, and applications of several analytical methods of quantifying the thrombogenic potential of IgG products and intermediates to meet the latest regulatory requirements. © 2014 The International Alliance for Biological Standardization. Source


Gillham A.,National Bioproducts Institute | Greyling B.,University of Witwatersrand | Wessels T.-M.,University of Witwatersrand | Mbele B.,Comprehensive Care | And 3 more authors.
Journal of Genetic Counseling | Year: 2015

In excess of 200 people with hemophilia (PWH) and their families have received genetic counseling (GC) at the Hemophilia Comprehensive Care Centre at Charlotte Maxeke Johannesburg Academic Hospital. However, very few of their at-risk female relatives have attended GC to discuss their reproductive risks and options, or their potential bleeding risks. Limited research has been conducted internationally on factors influencing uptake of GC and testing amongst female relatives of PWH. This prospective study aimed to explore the factors that influence the uptake of GC and testing by female relatives of PWH. An open-ended semi-structured interview schedule was developed. Participants included female relatives of PWH who at least had a family member who had received GC. Seventeen participants were interviewed; 7 who had GC previously and 10 who had not. All participants who had previously received GC found the service helpful and were mothers referred because their sons had hemophilia. Of those who had not had GC, possible deterrents included: being unaware of GC service, focus in clinic on PWH and not potential carriers, misunderstood risks related to hemophilia and carrier status, fear of finding out carrier status, and non-disclosure in families. Most participants were unaware of potential bleeding risks for carriers. The information will be used to provide a better service to female relatives of PWH with a goal being to set up a dedicated hemophilia carrier clinic. © 2015, National Society of Genetic Counselors, Inc. Source

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