We investigated the therapeutic effects of two different versions of A 1-15 (16) liposome-based vaccines. Inoculation of APP-V717IxPS-1 (APPxPS-1) double-transgenic mice with tetrapalmitoylated amyloid 1-15 peptide (palmA 1-15), or with amyloid 1-16 peptide (PEG-A 1-16) linked to a polyethyleneglycol spacer at each end, and embedded within a liposome membrane, elicited fast immune responses with identical binding epitopes. PalmA 1-15 liposomal vaccine elicited an immune response that restored the memory defect of the mice, whereas that of PEG-A 1-16 had no such effect. Immunoglobulins that were generated were predominantly of the IgG class with palmA 1-15, whereas those elicited by PEG-A 1-16 were primarily of the IgM class. The IgG subclasses of the antibodies generated by both vaccines were mostly IgG2b indicating noninflammatory Th2 isotype. CD and NMR revealed predominantly -sheet conformation of palmA1-15 and random coil of PEG-A 1-16. We conclude that the association with liposomes induced a variation of the immunogenic structures and thereby different immunogenicities. This finding supports the hypothesis that Alzheimer's disease is a ''conformational'' disease, implying that antibodies against amyloid sequences in the -sheet conformation are preferred as potential therapeutic agents.Alzheimer's disease ͉ -amyloid ͉ vaccine C linical manifestations of Alzheimer's disease (AD) include progressive memory loss, cognitive impairment, confusion, and personality changes. The major neuropathological changes in the brains of AD patients are senile plaques and neurofibrillar tangles causing progressive neuronal dysfunction. These pathological alterations are likely causally involved in eventual neuronal death, particularly in brain regions related to memory and cognition (1-4). Senile plaques are formed predominantly by the -amyloid peptide A 1-42 that is coiled and ␣-helical in its soluble form but, upon conformational transition, aggregates into -sheeted multimers. The monomeric A peptide is a physiological metabolite of the large amyloid precursor protein (APP, 695-770 aa) that undergoes processing by several sequential proteolytic steps (5). The A 1-42 aggregates are proposed to play the key role in the pathogenesis of AD (6). In transgenic animals that overexpress mutant human APP, anti-A-specific antibodies decreased the A burden and improved memory after either passive (7-11) or active (12-18) immunization.We previously demonstrated that i.p. inoculation of tetrapalmitoylated A1-16 reconstituted in liposomes to transgenic NORBA mice elicited significant titers of anti-A antibodies, that solubilized amyloid fibers in vitro and pancreatic A plaques in vivo (19). To circumvent T cell-mediated immune responses known to be causatively involved in the adverse events of meningoencephalitis of AD patients immunized with A1-42 (20-22), the A1-16 and 1-15 sequences were used for immunization of APPxPS1 double-transgenic mice (23) because strong T cell epitopes are located more toward the C-te...
Understanding metabolism in live microalgae is crucial for efficient biomaterial engineering, but conventional methods fail to evaluate heterogeneous populations of motile microalgae due to the labelling requirements and limited imaging speeds. Here, we demonstrate label-free video-rate metabolite imaging of live Euglena gracilis and statistical analysis of intracellular metabolite distributions under different culture conditions. Our approach provides further insights into understanding microalgal heterogeneity, optimizing culture methods and screening mutant microalgae.
The designed alpha-helical amphipathic peptide LAH4 assembles several properties, which makes it an interesting candidate as a gene-delivery vehicle. Besides being short and soluble in aqueous solutions, LAH4 presents cationic residues, which allow for efficient complexation of DNA. In addition, this peptide is poorly hemolytic at neutral pH, while it is able to destabilize biological membranes in acidic conditions. In this study, the structure of the peptide/DNA transfection complex was examined by circular dichroism and solid-state nuclear magnetic resonance spectroscopies and the thermodynamics of its formation and disassembly was monitored in a quantitative manner as a function of pH by isothermal titration calorimetry. Notably, the number of peptides within the complex considerably decreases upon acidification of the medium. This observation has direct and important consequences for the mechanism of action because the acidification of the endosome results in high local concentrations of free peptide in this organelle. Thus, these peptides become available to interact with the endosomal membranes and thereby responsible for the delivery of the transfection complex to the cytoplasm. When these data are taken together, they indicate a dual role of the peptide during the transfection process, namely, DNA complexation and membrane permeabilization.
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