In vitro affinity optimization of an anti-BDNF monoclonal antibody translates to improved potency in targeting chronic pain states in vivo.

The role of brain-derived neurotrophic factor (BDNF) signaling in chronic pain has been well documented. Given the important central role of BDNF in long term plasticity and memory, we sought to engineer a high affinity, peripherally-restricted monoclonal antibody against BDNF to modulate pain. BDNF shares 100% sequence homology across human and rodents; thus, we selected chickens as an alternative immune host for initial antibody generation. Here, we describe the affinity optimization of complementarity-determining region-grafted, chicken-derived R3bH01, an anti-BDNF antibody specifically blocking the TrkB receptor interaction. Antibody optimization led to the identification of B30, which has a > 300-fold improvement in affinity based on BIAcore, an 800-fold improvement in potency in a cell-based pERK assay and demonstrates exquisite selectivity over related neurotrophins. Affinity improvements measured in vitro translated to in vivo pharmacological activity, with B30 demonstrating a 30-fold improvement in potency over parental R3bH01 in a peripheral nerve injury model. We further demonstrate that peripheral BDNF plays a role in maintaining the plasticity of sensory neurons following nerve damage, with B30 reversing neuron hyperexcitability associated with heat and mechanical stimuli in a dose-dependent fashion. In summary, our data demonstrate that effective sequestration of BDNF via a high affinity neutralizing antibody has potential utility in modulating the pathophysiological mechanisms that drive chronic pain states.

Enhancing recombinant antibody performance by optimally engineering its format.

Antibody-based sensors are now widely used in therapeutics, diagnostics, and in environmental monitoring. Recombinant antibodies are becoming integral parts of such devices due to their reported high affinities, their capacity for engineering to achieve highly defined performance characteristics and the fact that their production can be optimized to a significant degree. To aid as a model for the identification of important analyte binding residues within the antibody sub-structure and elucidate the docking characteristics of small molecules such as metabolites, illicit drugs, biotherapeutics (proteins, peptides and nucleic acids) or toxins towards the antibody, herein we report the binding of the harmful cyanobacterial-toxin, microcystin-leucine-arginine (MC-LR) to a single chain fragment variable (scFv) antibody fragment. Analysis of the binding of MC-LR to this scFv was used to identify key residues of interest and to show how 'freely-available' and 'easily-accessible' computer-based webservers can be utilized to initiate an investigation into the binding characteristics of interacting molecules. In this study, a detailed investigation of the sub-structure of the anti-MC-LR (scFv) was carried out and antibody/small-molecule binding interactions were analyzed. The profile elucidated using computational analysis revealed amino acids of importance in the complementarity determining region light chain region 3 (CDRL3) and framework region 3 (FR3) of the heavy chain. Important amino acid residues within CDRL3 and FR3 were mutated in vitro and sensitivity and binding profiles were examined. It was identified that phenylalanine (F) at position 91 and aspartate (D) at position 92 of the light chain region, and arginine (R) at position 66 in framework region 3 (FR3) of the heavy chain were nvolved in binding. The introduction of an auxiliary antibody domain to the variable heavy and variable light (scFv) to ascertain its influence on stability and binding was also examined. The strategy adopted provided a deeper knowledge of scFv sub-structure and identified the regions and amino acids essential to antibody/small-molecule binding.

Detection of the cyanobacterial toxin, microcystin-LR, using a novel recombinant antibody-based optical-planar waveguide platform.

Microcystins are a major group of cyanobacterial heptapeptide toxins found in freshwater and brackish environments. There is currently an urgent requirement for highly-sensitive, rapid and in-expensive detection methodologies for these toxins. A novel single chain fragment variable (scFv) fragment was generated and is the first known report of a recombinant anti-microcystin avian antibody. In a surface plasmon resonance-based immunoassay, the antibody fragment displayed cross-reactivity with seven microcystin congeners (microcystin-leucine-arginine (MC-LR) 100%, microcystin-tyrosine-arginine (MC-YR) 79.7%, microcystin-leucine-alanine (MC-LA) 74.8%, microcystin-leucine-phenylalanine (MC-LF) 67.5%, microcystin-leucine-tryptophan (MC-LW) 63.7%, microcystin-arginine-arginine (MC-RR) 60.1% and nodularin (Nod) 69.3%, % cross reactivity). Following directed molecular evolution of the parental clone the resultant affinity-enhanced antibody fragment was applied in an optimized fluorescence immunoassay on a planar waveguide detection system. This novel immuno-sensing format can detect free microcystin-LR with a functional limit of detection of 0.19 ng mL(-1)and a detection range of 0.21-5.9 ng mL(-1). The assay is highly reproducible (displaying percentage coefficients of variance below 8% for intra-day assays and below 11% for inter-day assays), utilizes an inexpensive cartridge system with low reagent volumes and can be completed in less than twenty minutes.

Aflatoxins B(1), B(2) and G(1) modulate cytokine secretion and cell surface marker expression in J774A.1 murine macrophages.

Aflatoxins are fungal products which occur in food and feed. They are potent hepatocarcinogens, and are known to cause immunosuppression. We investigated the effect of aflatoxin B(1) (AFB(1)), aflatoxin B(2) (AFB(2)) and aflatoxin G(1) (AFG(1)) exposure, alone and in combination, on the secretion of key pro- and anti-inflammatory cytokines from the murine macrophage cell line, J774A.1. Exposure of macrophages to low doses of aflatoxin (0.01 or 0.1ng/mL) resulted in a statistically significant change in the secretion of a number of cytokines following stimulation with lipopolysaccharide (LPS), a component of Gram-negative bacterial cell walls. Specifically, treatment with AFB(1) or AFB(2) alone significantly decreased (P<0.01) the secretion of the anti-inflammatory cytokine interleukin (IL) 10 (IL-10), while the secretion of the pro-inflammatory cytokine IL-6 was significantly increased (P<0.01). In addition, aflatoxin exposure affected expression levels of key cell surface markers involved in the inflammatory response. Toll-like receptor 2 (TLR2) and Cluster of Differentiation 14 (CD14) expression levels decreased significantly (P<0.01), but Toll-like receptor 4 (TLR4) expression was unaffected. This data provides further insight into the mechanisms by which aflatoxins modulate the host immune response to exert their immunosuppressive activity.

Antibody-based sensors: principles, problems and potential for detection of pathogens and associated toxins.

Antibody-based sensors permit the rapid and sensitive analysis of a range of pathogens and associated toxins. A critical assessment of the implementation of such formats is provided, with reference to their principles, problems and potential for 'on-site' analysis. Particular emphasis is placed on the detection of foodborne bacterial pathogens, such as Escherichia coli and Listeria monocytogenes, and additional examples relating to the monitoring of fungal pathogens, viruses, mycotoxins, marine toxins and parasites are also provided.