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MJS201

Prion protein self-peptides modulate prion interactions and conversion

<p>Abstract</p> <p>Background</p> <p>Molecular mechanisms underlying prion agent replication, converting host-encoded cellular prion protein (PrP^C) into the scrapie associated isoform (PrP^Sc), are poorly understood. Selective self-interaction between PrP molecules forms a basis underlying the observed differences of the PrP^Cinto PrP^Scconversion process (agent replication). The importance of previously peptide-scanning mapped ovine PrP self-interaction domains on this conversion was investigated by studying the ability of six of these ovine PrP based peptides to modulate two processes; PrP self-interaction and conversion.</p> <p>Results</p> <p>Three peptides (octarepeat, binding domain 2 -and C-terminal) were capable of inhibiting self-interaction of PrP in a solid-phase PrP peptide array. Three peptides (N-terminal, binding domain 2, and amyloidogenic motif) modulated prion conversion when added before or after initiation of the prion protein misfolding cyclic amplification (PMCA) reaction using brain homogenates. The C-terminal peptides (core region and C-terminal) only affected conversion (increased PrP^resformation) when added before mixing PrP^Cand PrP^Sc, whereas the octarepeat peptide only affected conversion when added after this mixing.</p> <p>Conclusion</p> <p>This study identified the putative PrP core binding domain that facilitates the PrP^C-PrP^Scinteraction (not conversion), corroborating evidence that the region of PrP containing this domain is important in the species-barrier and/or scrapie susceptibility. The octarepeats can be involved in PrP^C-PrP^Scstabilization, whereas the N-terminal glycosaminoglycan binding motif and the amyloidogenic motif indirectly affected conversion. Binding domain 2 and the C-terminal domain are directly implicated in PrP^Cself-interaction during the conversion process and may prove to be prime targets in new therapeutic strategy development, potentially retaining PrP^Cfunction. These results emphasize the importance of probable PrP^C-PrP^Cand required PrP^C-PrP^Scinteractions during PrP conversion. All interactions are probably part of the complex process in which polymorphisms and species barriers affect TSE transmission and susceptibility.</p

Cognitive predictors of longitudinal positive symptom course in clinical high risk for psychosis

Background Clinical High Risk (CHS) for psychosis is a state in which positive symptoms are predominant but do not reach a level of severity that fulfils the criteria for a psychotic episode. The aim of this study has been to investigate whether cognition in subjects with newly detected CHR affects the longitudinal development of positive symptoms. Methods Fifty-three CHR individuals fulfilling the criteria for attenuated positive syndrome in the Structural Interview for Prodromal Syndromes (SIPS) were included. At inclusion, all participants completed a neurocognitive battery consisting of tests measuring attention, verbal memory, verbal fluency, executive functions and general intelligence. Cognitive domain z-scores were defined by contrasting with observed scores of a group of matched healthy controls (n = 40). Associations between cognitive performance at inclusion and longitudinal measures of positive symptoms were assessed by using generalised linear models including non-linear effects of time. All regression models were adjusted for age and gender. Results Overall, SIPS positive symptoms declined over the time period, with a steeper decline during the first six months. Deficits in executive functions were assossiated witn a higher load of positive symptoms at baseline (p=0.006), but also to a faster improvement (p=0.030), wheras those with poor verbal fluency improved more slowly (p=0.018). Conclusion To our knowledge, this is the first study that follows CHR subjects by means of frequent clinical interviews over a sustained period of time. The study provides evidence of an association between executive functions, including verbal fluency, with the evolvement of positive symptoms.publishedVersio

Associations between symptom and neurocognitive dimensions in clinical high risk for psychosis

Introduction Clinical high risk for psychosis (CHR) is associated with mild cognitive impairments. Symptoms are clustered into positive, negative and disorganization symptoms. The association between specific symptom dimensions and cognitive functions remains unclear. The aim of this study was to investigate the associations between cognitive functions and positive, negative, and disorganization symptoms. Method 53 CHR subjects fulfilling criteria for attenuated psychotic syndrome in the Structural Interview for Prodromal Syndromes (SIPS) were assessed for cognitive function. Five cognitive domain z-scores were defined by contrasting with observed scores of a group of healthy controls (n = 40). Principal Components Analyses were performed to construct general cognitive composite scores; one using all subtests and one using the cognitive domains. Associations between cognitive functions and symptoms are presented as Spearman's rank correlations and partial Spearman's rank correlations adjusted for age and gender. Results Positive symptoms were negatively associated with executive functions and verbal memory, and disorganization symptoms with poorer verbal fluency. Negative symptoms were associated with better executive functioning. There were no significant associations between the general cognitive composites and any of the symptom domains, except for a trend for positive symptoms. Conclusion In line with previous research, data indicated associations between positive symptoms and poorer executive functioning. Negative symptoms may not be related to executive functions in CHR the same way as in psychosis. Our results could indicate that attenuated positive symptoms are more related to cognitive deficits in CHR than positive symptoms in schizophrenia and FEP.publishedVersio

Reduced Expression of Emotion: A Red Flag Signalling Conversion to Psychosis in Clinical High Risk for Psychosis (CHR-P) Populations

Objective: In this hypothesis-testing study, which is based on findings from a previous atheoretical machine-learning study, we test the predictive power of baseline “reduced expression of emotion” for psychosis. Method: Study participants (N = 96, mean age 16.55 years) were recruited from the Prevention of Psychosis Study in Rogaland, Norway. The Structured Interview for Prodromal Syndromes (SIPS) was conducted 13 times over two years. Reduced expression of emotion was added to positive symptoms at baseline (P1–P5) as a predictor of psychosis onset over a two-year period using logistic regression. Results: Participants with a score above zero on expression of emotion had over eight times the odds of conversion (OR = 8.69, p < .001). Data indicated a significant dose–response association. A model including reduced expression of emotion at baseline together with the positive symptoms of the SIPS rendered the latter statistically insignificant. Conclusions: The study findings confirm findings from the previous machine-learning study, indicating that observing reduced expression of emotion may serve two purposes: first, it may add predictive value to psychosis conversion, and second, it is readily observable. This may facilitate detection of those most at risk within the clinical high risk of psychosis population, as well as those at clinical high risk. A next step could be including this symptom within current high-risk criteria. Future research should consolidate these findings.publishedVersio

Early detection of ultra high risk for psychosis in a Norwegian catchment area: The two year follow-up of the prevention of psychosis study

Objectives: Most individuals experience a relatively long period of sub-clinical psychotic like symptoms, known as the ultra high risk (UHR) or at risk mental states (ARMS), prior to a first episode of psychosis. Approximately 95% of individuals who will later develop psychosis are not referred to specialized clinical services and assessed during the UHR phase. The study aimed to investigate whether a systematic early detection program, modeled after the successful early detection of psychosis program TIPS, would improve the detection of help-seeking UHR individuals. The secondary aim was to examine the rates and predictors of conversion to psychosis after 2 years. Method: The overall study design was a prospective (2012–2018), follow- up study of individuals fulfilling UHR inclusion criteria as assessed by the structural interview for prodromal syndromes (SIPS). Help-seeking UHR individuals were recruited through systematic early detection strategies in a Norwegian catchment area and treated in the public mental health services. Results: In the study period 141 UHR help-seeking individuals were identified. This averages an incidence of 7 per 100,000 people per year. The baseline assessment was completed by 99 of these and the 2 year psychosis conversion rate was 20%. A linear mixed-model regression analysis found that the significant predictors of conversion were the course of positive (0.038) and negative symptoms (0.017). Age was also a significant predictor and showed an interaction with female gender ( \u3c 0.000). Conclusion: We managed to detect a proportion of UHR individuals in the upper range of the expected prediction by the population statistics and further case enrichment would improve this rate. Negative symptoms were significant predictors. As a risk factor for adverse functional outcomes and social marginalization, this could offer opportunities for earlier psychosocial intervention

Rapid and discriminatory diagnosis of scrapie and BSE in retro-pharyngeal lymph nodes of sheep

BACKGROUND: Diagnosis based on prion detection in lymph nodes of sheep and goats can improve active surveillance for scrapie and, if it were circulating, for bovine spongiform encephalopathy (BSE). With sizes that allow repetitive testing and a location that is easily accessible at slaughter, retropharyngeal lymph nodes (RLN) are considered suitable organs for testing. Western blotting (WB) of brain homogenates is, in principle, a technique well suited to both detect and discriminate between scrapie and BSE. In this report, WB is developed for rapid diagnosis in RLN and to study biochemical characteristics of PrP(res). RESULTS: Optimal PrP(res )detection in RLN by WB was achieved by proper tissue processing, antibody choice and inclusion of a step for PrP(res)concentration. The analyses were performed on three different sheep sources. Firstly, in a study with preclinical scrapie cases, WB of RLN from infected sheep of VRQ/VRQ genotype – VRQ represents, respectively, polymorphic PrP amino acids 136, 154, and 171 – allowed a diagnosis 14 mo earlier compared to WB of brain stem. Secondly, samples collected from sheep with confirmed scrapie in the course of passive and active surveillance programmes in the period 2002–2003 yielded positive results depending on genotype: all sheep with genotypes ARH/VRQ, VRQ/VRQ, and ARQ/VRQ scored positive for PrP(res), but ARQ/ARQ and ARR/VRQ were not all positive. Thirdly, in an experimental BSE study, detection of PrP(res )in all 11 ARQ/ARQ sheep, including 7 preclinical cases, was possible. In all instances, WB and IHC were almost as sensitive. Moreover, BSE infection could be discriminated from scrapie infection by faster electrophoretic migration of the PrP(res )bands. Using dual antibody staining with selected monoclonal antibodies like 12B2 and L42, these differences in migration could be employed for an unequivocal differentiation between BSE and scrapie. With respect to glycosylation of PrP(res), BSE cases exhibited a greater diglycosylated fraction than scrapie cases. Furthermore, a slight time dependent increase of diglycosylated PrP(res )was noted between individual sheep, which was remarkable in that it occurred in both scrapie and BSE study. CONCLUSION: The present data indicate that, used in conjunction with testing in brain, WB of RLN can be a sensitive tool for improving surveillance of scrapie and BSE, allowing early detection of BSE and scrapie and thereby ensuring safer sheep and goat products

Detection of Type 1 Prion Protein in Variant Creutzfeldt-Jakob Disease

Molecular typing of the abnormal form of the prion protein (PrP(Sc)) has come to be regarded as a powerful tool in the investigation of the prion diseases. All evidence thus far presented indicates a single PrP(Sc) molecular type in variant Creutzfeldt-Jakob disease (termed type 2B), presumably resulting from infection with a single strain of the agent (bovine spongiform encephalopathy). Here we show for the first time that the PrP(Sc) that accumulates in the brain in variant Creutzfeldt-Jakob disease also contains a minority type 1 component. This minority type 1 PrP(Sc) was found in all 21 cases of variant Creutzfeldt-Jakob disease tested, irrespective of brain region examined, and was also present in the variant Creutzfeldt-Jakob disease tonsil. The quantitative balance between PrP(Sc) types was maintained when variant Creutzfeldt-Jakob disease was transmitted to wild-type mice and was also found in bovine spongiform encephalopathy cattle brain, indicating that the agent rather than the host specifies their relative representation. These results indicate that PrP(Sc) molecular typing is based on quantitative rather than qualitative phenomena and point to a complex relationship between prion protein biochemistry, disease phenotype and agent strain

Antigenic Profile of African Horse Sickness Virus Serotype 4 VP5 and Identification of a Neutralizing Epitope Shared with Bluetongue Virus and Epizootic Hemorrhagic Disease Virus

AbstractAfrican horse sickness virus (AHSV) causes a fatal disease in horses. The virus capsid is composed of a double protein layer, the outermost of which is formed by two proteins: VP2 and VP5. VP2 is known to determine the serotype of the virus and to contain the neutralizing epitopes. The biological function of VP5, the other component of the capsid, is unknown. In this report, AHSV VP5, expressed in insect cells alone or together with VP2, was able to induce AHSV-specific neutralizing antibodies. Moreover, two VP5-specific monoclonal antibodies (MAbs) that were able to neutralize the virus in a plaque reduction assay were generated. To dissect the antigenic structure of AHSV VP5, the protein was cloned inEscherichia coliusing the pET3 system. The immunoreactivity of both MAbs, and horse and rabbit polyclonal antisera, with 17 overlapping fragments from VP5 was analyzed. The most immunodominant region was found in the N-terminal 330 residues of VP5, defining two antigenic regions, I (residues 151–200) and II (residues 83–120). The epitopes were further defined by PEPSCAN analysis with 12mer peptides, which determined eight antigenic sites in the N-terminal half of the molecule. Neutralizing epitopes were defined at positions 85–92 (PDPLSPGE) for MAb 10AE12 and at 179–185 (EEDLRTR) for MAb 10AC6. Epitope 10AE12 is highly conserved between the different orbiviruses. MAb 10AE12 was able to recognize bluetongue virus VP5 and epizootic hemorrhagic disease virus VP5 by several techniques. These data will be especially useful for vaccine development and diagnostic purposes