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In amyloid-positive individuals at risk for Alzheimer's disease (AD), high soluble 42-amino acid amyloid-β (Aβ42) levels are associated with normal cognition. It is unknown if this relationship applies longitudinally in a genetic cohort.To test the hypothesis that high Aβ42 preserves normal cognition in amyloid-positive individuals with Alzheimer's disease (AD)-causing mutations (APP, PSEN1, or PSEN2) to a greater extent than lower levels of brain amyloid, cerebrospinal fluid (CSF) phosphorylated tau (p-tau), or total tau (t-tau).Cognitive progression was defined as any increase in Clinical Dementia Rating (CDR = 0, normal cognition; 0.5, very mild dementia; 1, mild dementia) over 3 years. Amyloid-positivity was defined as a standard uptake value ratio (SUVR) ≥1.42 by Pittsburgh compound-B positron emission tomography (PiB-PET). We used modified Poisson regression models to estimate relative risk (RR), adjusted for age at onset, sex, education, APOE4 status, and duration of follow-up. The results were confirmed with multiple sensitivity analyses, including Cox regression.Of 232 mutation carriers, 108 were PiB-PET-positive at baseline, with 43 (39.8% ) meeting criteria for progression after 3.3±2.0 years. Soluble Aβ42 levels were higher among CDR non-progressors than CDR progressors. Higher Aβ42 predicted a lower risk of progression (adjusted RR, 0.36; 95% confidence interval [CI], 0.19-0.67; p = 0.002) better than lower SUVR (RR, 0.81; 95% CI, 0.68-0.96; p = 0.018). CSF Aβ42 levels predicting lower risk of progression increased with higher SUVR levels.High CSF Aβ42 levels predict normal cognition in amyloid-positive individuals with AD-causing genetic mutations.

Cell-penetrating peptides (CPPs) uptake mechanism is still in need of more clarification to have a better understanding of their action in the mediation of oligonucleotide transfection. In this study, the effect on early events (1 h treatment) in transfection by PepFect14 (PF14), with or without oligonucleotide cargo on gene expression, in HeLa cells, have been investigated. The RNA expression profile was characterized by RNA sequencing and confirmed by qPCR analysis. The gene regulations were then related to the biological processes by the study of signaling pathways that showed the induction of autophagy-related genes in early transfection. A ligand library interfering with the detected intracellular pathways showed concentration-dependent effects on the transfection efficiency of splice correction oligonucleotide complexed with PepFect14, proving that the autophagy process is induced upon the uptake of complexes. Finally, the autophagy induction and colocalization with autophagosomes have been confirmed by confocal microscopy and transmission electron microscopy. We conclude that autophagy, an inherent cellular response process, is triggered by the cellular uptake of CPP-based transfection system. This finding opens novel possibilities to use autophagy modifiers in future gene therapy.

Gene therapy holds the promise of revolutionizing the way we treat diseases. By using recombinant DNA and oligonucleotides (ONs), gene functions can be restored, altered or silenced according to the therapeutic need. However, gene therapy approaches require the delivery of large and charged nucleic acid-based molecules to their intracellular targets across the plasma membrane, which is inherently impermeable to such molecules. In this thesis, two chemically modified cell-penetrating peptides (CPPs) that have superior delivery properties for several nucleic acid-based therapeutics are developed. These CPPs can spontaneously form nanoparticles upon non-covalent complexation with the nucleic acid cargo, and the formed nanoparticles mediate efficient cellular transfection. In paper I, we show that an N-terminally stearic acid-modified version of transportan-10 (PF3) can efficiently transfect different cell types with plasmid DNA and mediates efficient gene delivery in-vivo when administrated intra muscularly (i.m.) or intradermaly (i.d.). In paper II, a new peptide with ornithine modification, PF14, is shown to efficiently deliver splice-switching oligonucleotides (SSOs) in different cell models including mdx mouse myotubes; a cell culture model of Duchenne’s muscular dystrophy (DMD). Additionally, we describe a method for incorporating the PF14-SSO nanoparticles into a solid formulation that is active and stable even when stored at elevated temperatures for several weeks. In paper III, we demonstrate the involvement of class-A scavenger receptor subtypes (SCARA3 & SCARA5) in the uptake of PF14-SSO nanoparticles, which possess negative surface charge, and suggest for the first time that some CPP-based systems function through scavenger receptors. In paper IV, the ability of PF14 to deliver siRNA to different cell lines is shown and their stability in simulated gastric acidic conditions is highlighted. Taken together, these results demonstrate that certain chemical modifications can drastically enhance the activity and stability of CPPs for delivering nucleic acids after spontaneous nanoparticle formation upon non-covalent complexation. Moreover, we show that CPP-based nanoparticles can be formulated into convenient and stable solid formulations that can be suitable for several therapeutic applications. Importantly, the involvement of scavenger receptors in the uptake of such nanoparticles is presented, which could yield novel possibilities to understand and improve the transfection by CPPs and other gene therapy nanoparticles. At the time of doctoral defence the following paper was unpublished and had a status as follows: Paper nr 4: Submitted

Cell penetrating peptides (CPPs) have been extensively studied and exploited as drug delivery vectors for a wide variety of therapeu-tic cargos. However, several issues remain to be addressed regarding the enhancement of their efficiency and stability. In addition, to be available for patients, CPP-based therapeutics have to be formulated into suitable pharmaceutical forms that can be readily manufactured, transported, stored and conveniently used.In this thesis, three chemically modified CPPs are developed having superior delivery properties for several nucleic acid-based the-rapeutic cargoes including: plasmids, small interfering RNA (siRNA) and splice switching oligonucleutides (SSOs), in different in-vitro and in-vivo models. In Paper I, we show that an N-terminally stearic acid-modified version of transportan-10 (TP10) can form stable nanopar-ticles with plasmids that efficiently transfect different cell types and can mediate efficient gene delivery in-vivo when administrated intra muscularly (i.m.) or intradermaly (i.d.). In paper II, stearyl-TP10 is further modified with pH titratable trifluoromethylquinoline moieties to facilitate endosomal release. The new peptide, denoted PepFect 6 (PF6), elicited robust RNAi responses when complexed with siRNA in several cell models and promoted strong RNAi responses in differ-ent organs following systemic delivery in mice without any associated toxicity. In paper III , a new peptide with ornithine modification, PF14, is shown to efficiently deliver SSOs in different cell models including HeLa pLuc705 and mdx mouse myotubes; a cell culture model of Duchenne‟s muscular dystrophy (DMD). Additionally, we have developed a method for incorporating this delivery system into solid formulation that could be suitable for several therapeutic appli-cations. Solid dispersion technique is utilized and the formed solid formulations are as active as the freshly prepared nanocparticles in solution even when stored at elevated temperatures for several weeks.Taken together, these results demonstrate that certain chemical modifications could drastically enhance the activity and stability of CPPs in-vitro and in-vivo. Moreover, we show that CPP-based thera-peutics could be formulated into convenient and manufacturable do-sage forms.