== == Problem == Antibodybased immunotherapy might be an efficient way for the treatment of prion diseases, for which no cure exists

== == Problem == Antibodybased immunotherapy might be an efficient way for the treatment of prion diseases, for which no cure exists. repertoires, nextgeneration sequencing, phage display, prion disease Subject Categories:Immunology, Neuroscience This study assessed the antiprion protein (PrP) immunoreactivity in human immunoglobulin repertoires and patient samples. AntiPrP autoimmunity can exist in human communities, appears to be innocuous, and may protect against prion infections. == The paper explained. == == Problem Trofinetide == Antibodybased immunotherapy might be an efficient way for the treatment of prion diseases, for which no cure exists. However, antibodies targeting specific regions of the prion protein (PrP) can either be neurotoxic or neuroprotective. Hence, the identification of antiPrP antibodies specifically targeting neuroprotective epitopes is of high importance for the generation of safe prion immunotherapeutics. == Results == In this study, we used Fab phage display to retrieve antibodies targeting different epitopes of PrP from a synthetic human antibody library. We demonstrated that antibodies targeting the Nterminal part of PrP were neuroprotective in a model Trofinetide of prioninduced neurodegeneration. Interestingly, mining of published human antibody databases confirmed the presence of such antiPrP antibodies in nave repertoires of circulating B cells from healthy humans. We also found hightiter PrP autoantibodies directed against the flexible tail of PrP in the plasma of unselected hospitalized patients without Trofinetide any clinical features of a pathological disease. == Impact == Our data demonstrate the presence of naturally occurring, innocuous antiPrP antibodies in humans which may constitute a potential source for the development of effective and safe immunotherapeutics to combat prion diseases. == Introduction == Many neurodegenerative syndromes, including prion diseases, Alzheimer’s disease, and Parkinson’s disease, go along with the accumulation of misfolded and aggregated proteins in the central nervous system. Antibodies against such proteins may be beneficial (Schenket al,1999), e.g., by opsonizing pathological aggregates and mediating their degradation by phagocytic cells (Heppneret al,2001; Kranichet al,2010). While the clinical effectiveness of antibodybased therapies against neurodegenerative diseases is still being debated (Schillinget al,2018), there is ample evidence that both active immunization and passive antibody transfer can effectively clear pathological aggregates in preclinical animal models and, to some extent, in affected humans. According to the proteinonly hypothesis, the prion is an infectious particle consisting of PrPSc, an aggregated and proteinaseK (PK)resistant isoform, of the cellular prion protein PrPC(Prusiner,1998). PrPCconsists of a Cterminal globular domain (GD) and an Nterminal flexible tail (FT) which includes the octapeptide repeat (OR) region, two cationic charge clusters (CC1 and CC2) and a hydrophobic core (HC; Rieket al,1997). The CC1 domain of PrPCparticipates in Schwann cell maintenance by activating the G proteincoupled receptor Adgrg6 (Bremeret al,2010; Kufferet al,2016). While PrPCdeficient mice are only mildly affected, PrPScnecessitates PrPCfor its propagation (Weissmann,1991) and prion toxicity is transduced by PrPConto target cells (Mallucciet al,2003; Sonatiet al,2013). Therefore, suppression of PrPCby means of antiPrPCantibodies represents a rational strategy against prion diseases. Here, we panned a synthetic human antibody phage display library to explore the presence of PrPbinding antibody fragments (Fabs; Frenzelet al,2016). To identify rare antibodies to poorly antigenic epitopes that may be overlooked by conventional screening technologies, we performed nextgeneration sequencing (NGS) of panning outputs after phage selections (Ravnet al,2010). Several antiPrP binders were identified and found to antagonize prion toxicity. What is more, mining of published human antibody repertoires identified sequences similar to an antiprion phagederived Fab which, when expressed, acted as functional PrP binders. Lastly, the interrogation of a large unselected hospital cohort (n=37,894) highlighted individuals with hightiter antiPrP Trofinetide autoreactivity whose clinical presentation was heterogeneous, yet unrelated to known features of prion diseases. Therefore, antiprion immunity can exist in human communities and is seemingly innocuous. == Results == == Phage display selection strategy for antiPrP Fabs == Rabbit Polyclonal to PDCD4 (phospho-Ser457) We used three rounds of phage display to screen two synthetic human Fab phage display libraries (FigEV1A) with short (810 aa) and long (1220 aa) heavychain complementaritydetermining regions 3 (HCDR3). These libraries were constructed to mimic human antibody repertoires by combining frameworks from human germline sequences with diversified HCDR3 whose design approximated the natural gene sequences in human repertoires as compiled in the IMGT database (Giudicelliet al,2006). The first and second biopanning rounds were performed against fulllength recombinant mouse PrP (recPrP23231) to enrich for Fabs covering a large variety of PrP epitopes. To further select Fabs recognizing specific PrP epitopes, a third panning round was Trofinetide conducted against several different antigens in parallel, including recPrP23231,.