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Antibody light chain (LC) aggregation in vivo leads to the systemic deposition of Ig light chain domains in the form of either amyloid fibrils (AL-amyloidosis) or amorphous deposits, light-chain deposition disease (LCDD), in mainly cardiac or renal tissue and is a pathological condition that is often fatal. Molecular factors that may contribute to the propensity of LCs to aggregate in vivo, such as the protein primary structure or local environment, are intensive areas of study. Herein, we show that the aggregation of a human antibody kappa-(kappa-MJM) and lambda-(lambda-L155) light chain (1 mg/mL) can be accelerated in vitro when they are incubated under physiologically relevant conditions, PBS, pH 7.4 and 37 degrees C, in the presence of a panel of biologically relevant lipid-derived aldehydes, 4-hydroxynonenal (4-HNE), malondialdehyde (MDA), glyoxal (GLY), atheronal-A (KA), and atheronal-B (ALD). Thioflavin-T (ThT) and Congo Red (CR) binding assays coupled with turbidity studies reveal that this aldehyde-induced aggregation can be associated with alteration of protein secondary structure to an increased beta-sheet conformation. We observed that the nature of the conformational change is primarily dependent upon the lipidic aldehyde studied, not the protein sequence. Thus, the cholesterol 5,6-secosterols, KA and ALD, cause an amorphous-type aggregation which is ThT and CR negative for both the kappa-MJM and lambda-L155 light chains, whereas 4-HNE, MDA, and GLY induce aggregates that bind both ThT and CR. TEM analysis revealed that amyloid fibrils were formed during the 4-HNE-mediated aggregation of kappa-MJM and lambda-L155 light chains, whereas ALD-induced aggregates of these LCs where amorphous in nature. Kinetic profiles of LC aggregation reveal clear differences between the aldehydes, KA and ALD, causing a classic nucleated polymerization-type aggregation, with a lag phase (of approximately 150 h) followed by a growth phase that plateaus, whereas 4-HNE, MDA, and GLY trigger a seeded-type aggregation process that has no lag phase. In-depth studies of the 4-HNE-accelerated aggregation of kappa-MJM and lambda-L155 reveal a clear aldehyde concentration dependence and a process that can be inhibited by the naturally occurring osmolyte trimethylamine N-oxide (TMAO). Given these data, we feel our recently discovered paradigm of inflammatory aldehyde-induced protein misfolding may now extend to LC aggregation.

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The protective antigen (PA(83)) of Bacillus anthracis is the dominant antigen in natural and vaccine-induced immunity to anthrax infection. Three human single-chain variable fragments (scFvs) against cell bound PA were isolated from an antibody phage display library. Specifically, the antibodies were evaluated for their ability to bind to cell bound heptameric PA and ultimately protect against the cytotoxicity of lethal toxin. In total, all three scFvs possessed neutralizing activity against the cytotoxic effects of lethal toxin in a macrophage lysis assay. The K(d) values of the Fabs were determined, interestingly their protective effects did not parallel their affinities; hence, a simple binding argument alone to PA(63) cannot be used as the distinguishing feature for the prediction of their neutralization abilities. Immunofluorescent microscopy experiments were conducted and provided strong evidence for Fab binding to oligomeric PA on the cell surface and thus a plausible mechanism for the toxin neutralization activity that was observed. The results of this study presented herein suggest that our antibodies compete with LF-PA cell surface interactions, and thus may provide potential application of human antibodies as passive immunization prophylactics in cases of B. anthracis exposure and infection.

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Many bacterial pathogens coordinate their virulence factor expression in a cell density-dependent manner. This population-dependent coordination of gene expression in bacteria has been termed "quorum sensing" (QS). N-Acyl homoserine lactones (AHLs) are used by over 70 Gram-negative bacterial species as autoinducers. Inhibition of QS signaling might represent a new target for antimicrobial therapy. Here we report the hapten design, synthesis, generation of monoclonal antibodies (mAbs) against AHLs, and the evaluation of these mAbs for their ability to blunt QS signaling and inhibit virulence factor expression in P. aeruginosa. The mAbs can be envisioned as a tool for future investigations into AHL-based QS, which may aid in gaining new insights into the pathogenesis of P. aeruginosa and may ultimately lead to the development of new strategies to combat bacterial diseases.

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Immunopharmacotherapy as an approach to combat drugs of abuse has become an active area of investigation. Marijuana is the most commonly used illicit drug in the U.S. The main active chemical in marijuana is delta9-tetrahydrocannabinol (delta9-THC); hence, monoclonal antibodies with high affinity and specificity for delta9-tetrahydrocannabinol could be valuable immunopharmacotherapeutic intervention and diagnostic tools. We have synthesized immunoconjugates that induce an effective immune response to delta9-THC and describe a convenient synthesis of radiolabeled delta9-THC. We demonstrate the value and use of this probe to select anti-delta9-THC antibodies that bind delta9-THC with good affinity. The synthetic route to radiolabeled delta9-THC has enabled the correct assessment of the affinity of these antibodies to their ligand and may facilitate future binding studies between delta9-THC and its analogues and the cannabinoid receptors.

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Constrained nicotine analogues were synthesized and coupled to the carrier protein KLH. The immunogenic effects were compared to those using our previously designed flexible nicotine hapten. Immunization of mice with the constrained hapten conjugates resulted in highly increased antibody titers and affinity for nicotine.

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