Susumu Shirabe

Ultrasensitive human prion detection in cerebrospinal fluid by real-time quaking-induced conversion

The development of technologies for the in vitro amplification of abnormal conformations of prion protein (PrPSc) has generated the potential for sensitive detection of prions. Here we developed a new PrPSc amplification assay, called real-time quaking-induced conversion (RT-QUIC), which allows the detection of ≥1 fg of PrPSc in diluted Creutzfeldt-Jakob disease (CJD) brain homogenate. Moreover, we assessed the technique first in a series of Japanese subjects and then in a blind study of 30 cerebrospinal fluid specimens from Australia, which achieved greater than 80% sensitivity and 100% specificity. These findings indicate the promising enhanced diagnostic capacity of RT-QUIC in the antemortem evaluation of suspected CJD.

Hot spots in prion protein for pathogenic conversion

Prion proteins are key molecules in transmissible spongiform encephalopathies (TSEs), but the precise mechanism of the conversion from the cellular form (PrPC) to the scrapie form (PrPSc) is still unknown. Here we discovered a chemical chaperone to stabilize the PrPC conformation and identified the hot spots to stop the pathogenic conversion. We conducted in silico screening to find compounds that fitted into a “pocket” created by residues undergoing the conformational rearrangements between the native and the sparsely populated high-energy states (PrP*) and that directly bind to those residues. Forty-four selected compounds were tested in a TSE-infected cell culture model, among which one, 2-pyrrolidin-1-yl-N-[4-[4-(2-pyrrolidin-1-yl-acetylamino)-benzyl]-phenyl]-acetamide, termed GN8, efficiently reduced PrPSc. Subsequently, administration of GN8 was found to prolong the survival of TSE-infected mice. Heteronuclear NMR and computer simulation showed that the specific binding sites are the A-S2 loop (N159) and the region from helix B (V189, T192, and K194) to B-C loop (E196), indicating that the intercalation of these distant regions (hot spots) hampers the pathogenic conversion process. Dynamics-based drug discovery strategy, demonstrated here focusing on the hot spots of PrPC, will open the way to the development of novel anti-prion drugs.

Prospective 10-year surveillance of human prion diseases in Japan

We analysed the epidemiological data and clinical features of patients with prion diseases that had been registered by the Creutzfeldt-Jakob Disease Surveillance Committee, Japan, over the past 10 years, since 1999. We obtained information on 1685 Japanese patients suspected as having prion diseases and judged that 1222 patients had prion diseases, consisting of definite (n=180, 14.7%) and probable (n=1029, 84.2%) cases, except for dura mater graft-associated Creutzfeldt-Jakob disease which also included possible cases (n=13, 1.1%). They were classified into 922 (75.5%) with sporadic Creutzfeldt-Jakob disease, 216 (17.7%) with genetic prion diseases, 81 (6.6%) with acquired prion diseases, including 80 cases of dura mater graft-associated Creutzfeldt-Jakob disease and one case of variant Creutzfeldt-Jakob disease, and three cases of unclassified Creutzfeldt-Jakob disease (0.2%). The annual incidence rate of prion disease ranged from 0.65 in 1999 to 1.10 in 2006, with an average of 0.85, similar to European countries. Although methionine homozygosity at codon 129 polymorphism of the prion protein gene was reported to be very common (93%) in the general Japanese population, sporadic Creutzfeldt-Jakob disease in Japan was significantly associated with codon 129 homozygosity (97.5%), as reported in western countries. In sporadic Creutzfeldt-Jakob disease, MM1 type (Parchis classification) is the most common, as in western countries. Among atypical sporadic Creutzfeldt-Jakob disease cases, the MM2 type appeared most common, probably related to the very high proportion of methionine allele in the Japanese population. As for iatrogenic Creutzfeldt-Jakob disease, only dura mater graft-associated Creutzfeldt-Jakob disease cases were reported in Japan and, combined with the data from previous surveillance systems, the total number of dura mater graft-associated Creutzfeldt-Jakob disease was 138, comprising the majority of worldwide dura mater graft-associated Creutzfeldt-Jakob disease patients. Regarding genetic prion diseases, the most common mutation of prion protein gene was V180I (41.2%), followed by P102L (18.1%), E200K (17.1%) and M232R (15.3%), and this distribution was quite different from that in Europe. In particular, V180I and M232R were quite rare mutations worldwide. Patients with V180I or M232R mutations rarely had a family history of prion diseases, indicating that a genetic test for sporadic cases is necessary to distinguish these from sporadic Creutzfeldt-Jakob disease. In conclusion, our prospective 10-year surveillance revealed a frequent occurrence of dura mater graft-associated Creutzfeldt-Jakob disease, and unique phenotypes of sporadic Creutzfeldt-Jakob disease and genetic prion diseases related to the characteristic distribution of prion protein gene mutations and polymorphisms in Japan, compared with those in western countries.

14-3-3 Protein, Total Tau and Phosphorylated Tau in Cerebrospinal Fluid of Patients with Creutzfeldt-Jakob Disease and Neurodegenerative Disease in Japan

Summary1.Sporadic Creutzfeldt-Jakob disease (CJD) is a rapidly progressive and fatal disease. Patients with CJD usually become akinetic mutism within approximately 6 months. In addition, clinical signs and symptoms at early stage of sporadic CJD may not be easy to distinguish from other neurodegenerative diseases by neurological findings. However, diagnostic biochemical parameters including 14-3-3 protein, S100, neuron-specific enorase in cerebrospinal fluid (CSF) have been used as diagnostic markers, elevated titers of these markers can also be observed in CSF in other neurodegenerative diseases. Therefore, we examined other biochemical markers to discriminate CJD from other neurodegenerative diseases in CSF.2.We analyzed CSF samples derived from 100 patients with various neurodegenerative disorders by Western blot of 14-3-3 protein, quantification of total tau (t-tau) protein, and phosphorylated tau (p-tau) protein. All patients with CJD in this study showed positive 14-3-3 protein and elevated t-tau protein (>1000 pg/mL) in CSF. We also detected positive 14-3-3 protein bands in two patients in non-CJD group (patients with dementia of Alzheimers type; DAT) and also detected elevated t-tau protein in three patients in non-CJD group. Elevated t-tau protein levels were observed in two patients with DAT and in one patient with cerevrovascular disease in acute phase.3.To distinguish patients with CJD from non-CJD patients with elevated t-tau protein in CSF, we compared the ratio of p-tau and t-tau proteins. The p-/t-tau ratio was dramatically and significantly higher in DAT patients rather than in CJD patients.4.Therefore, we concluded that the assay of t-tau protein may be useful as 1st screening and the ratio of p-tau protein/t-tau protein would be useful as 2nd screening to discriminate CJD from other neurodegenerative diseases.

Apoptosis Induction In Human Peripheral Blood T Lymphocytes By High-dose Steroid Therapy

High-dose steroid pulse therapy is effective in transplant rejection and severe autoimmune diseases. Our goal was to identify the mechanism by which high-dose steroid exerts specific immunosuppressive actions. In this study, we investigated the in vivo effects of high-dose (1 g) methylprednisolone infusion on peripheral blood T lymphocyte apoptosis induction in 15 patients with severe autoimmune diseases. DNA fragmentation was detected in peripheral blood T cells isolated from these patients after 2 and 4 hr of steroid infusion. In contrast, T cells isolated from the same patients before or 8 or more hours after infusion did not show DNA fragmentation. DNA fragmentation was more significant in CD4+ than CD8+ T cells. The susceptibility of CD4+ T cells to apoptosis was associated with a lower expression of Bcl-2 in these cells compared with that on CD8+ T cells. To support the T-cell apoptosis induction by pulse therapy, peripheral blood T cells from normal subjects underwent DNA fragmentation after in vitro exposure to 2.5-10 microg/ml of methylprednisolone for 30 min. Our results indicate that induction of peripheral blood T-cell apoptosis is an important mechanism contributing to the immunosuppression observed after high-dose steroid therapy.

Plasmapheresis in treatment of human T-lymphotropic virus type-I associated myelopathy.

In 11 of 18 patients with human T-lymphotropic virus type-I (HTLV-I) associated myelopathy (HAM) gait, sensory, and/or sphincter disturbance improved with plasmapheresis (4 to 6 sessions in 2 weeks), and the effects were maintained for 2 to 4 weeks. Plasmapheresis lowered the titre of HTLV-I antibody in serum but not in cerebrospinal fluid, and change of HTLV-I antibody titres did not correlate with the effects of plasmapheresis. These results suggest that plasmapheresis is useful treatment, at least in producing a temporary improvement, in patients with HAM, and that some humoral factor(s), but not HTLV-I antibody, may be important in the pathogenesis of HAM.

Apoptosis in labial salivary glands from Sjögren's syndrome (SS) patients: comparison with human T lymphotropic virus-I (HTLV-I)-seronegative and -seropositive SS patients

Apoptosis is a type of cell death that occurs during morphogenesis and development of the immune system. One of the mechanisms is mediated through the Fas and Fas ligand (FasL) pathway. To determine the possible involvement of Fas and its ligand in salivary gland destruction, we analysed the appearance of nuclei with DNA fragmentation by using nick end labelling (TUNEL) and the expression of Fas and FasL by immunohistochemistry in labial salivary glands. Furthermore, we compared the features of apoptosis in labial salivary glands between HTLV‐I− and HTLV‐I+ SS. When the frozen sections of 10 primary SS patients in the absence of anti‐HTLV‐I antibody were examined, several apoptotic cells were found in the acinar and ductal epithelial cells as well as infiltrated mononuclear cells. Both Fas and FasL were detected in the infiltrated mononuclear cells. Acinar epithelial cells, which are surrounded by FasL+ mononuclear cells, were also double‐positive with Fas and FasL, although the expression of FasL was localized at their apical border, suggesting that apoptosis of mononuclear cells was achieved by activation‐induced mechanisms through Fas/FasL pathways, and that of acinar epithelial cells was mediated by FasL derived from either acinar epithelial cells themselves or infiltrated mononuclear cells. Interestingly, Fas expression in ductal epithelial cells was localized around the lumen side of the ducts, indicating that FasL secreted from acinar epithelial cells may induce Fas‐mediated apoptosis of ductal epithelial cells. We also studied the labial salivary glands from nine SS patients with anti‐HTLV‐I antibodies. There was no significant difference in the occurrence of apoptotic cells or in the expression of Fas and FasL between HTLV‐I+ and HTLV‐I− SS patients. It was of note that neither the expression of Fas and FasL nor the presence of apoptotic cells were determined in labial salivary glands from subjects without SS. These findings indicate that Fas‐mediated apoptosis in salivary glands could be involved in the pathological manifestations of SS, irrespective of HTLV‐I seropositivity.

Presence of serum anti-human T-lymphotropic virus type I (HTLV-I) IgM antibodies means persistent active replication of HTLV-I in HTLV-I-associated myelopathy

We investigated serum IgM antibodies against human T-lymphotropic virus type I (HTLV-I) in 29 HTLV-I associated myelopathy (HAM) patients and 34 HTLV-I carriers, using western blot analysis. Anti-HTLV-I IgM was detected in all 6 post-transfusional HAM patients and in 19 of 23 (83%) HAM patients with no history of blood transfusion, but in only 4 of 21 (19%) HTLV-I carriers. In HAM patients, HTLV-I proviral DNA integrated into peripheral blood lymphocyte (PBL) was detected by Southern blot analysis in all of the 6 (100%) and 18 of the 23 (78%). In contrast, it was detected in only 2 of 25 (8%) HTLV-I carriers. For the serum anti-HTLV-I IgM and HTLV-I provirus in PBL, the differences between the HAM and HTLV-I carriers were statistically significant (P less than 0.01). Our data indicate that the increased HTLV-I proviral DNA in PBL is produced by the persistent active replication of HTLV-I in HAM. Furthermore, Southern blot analysis showed intense bands in HAM patients with histories of blood transfusion, in whom the progression of the disease had been rapid. We conclude that the persistent active replication of HTLV-I is an important factor in the pathogenesis of HAM.

Total Tau Protein in Cerebrospinal Fluid and Diffusion-Weighted MRI as an Early Diagnostic Marker for Creutzfeldt-Jakob Disease

Background: We have recently begun to doubt the effectiveness of periodic sharp wave complexes observed on electroencephalographs and the detection of 14-3-3 protein in cerebrospinal fluid (CSF) as diagnostic criteria for Creutzfeldt-Jakob disease (CJD). Diffusion-weighted magnetic resonance imaging (DWI) and the detection of total tau (t-tau) protein in CSF may be more sensitive diagnostic criteria. Methods: Among 44 CJD patients, we selected 21 subjects that suffered from early-stage CJD, which was defined as cases in the 6 weeks following the onset of the disease. The sensitivities of DWI and electroencephalographs, as well as those of t-tau protein, 14-3-3 protein, neuron-specific enolase (NSE), and S-100b protein in CSF were compared as diagnostic markers for early-stage CJD. Results: NSE, S-100b protein, t-tau protein, and 14-3-3 protein were detected in the samples from 57.1, 4.8, 95.2, and 76.2% of the 21 early-stage CJD patients, respectively. Additionally, DWI was used to positively identify 90.5% of these cases. Conclusion: We concluded that t-tau protein was the most sensitive of the diagnostic markers for CJD. Moreover, the data in this study showed that detection of t-tau protein combined with DWI identified 98% of the early-stage cases, and these tests should be included as diagnostic criteria for CJD.

Establishment of a standard 14-3-3 protein assay of cerebrospinal fluid as a diagnostic tool for Creutzfeldt–Jakob disease

Periodic sharp wave complexes observed on an electroencephalographic recording and the presence of a 14-3-3 protein in the cerebrospinal fluid (CSF) are both included in the diagnostic criteria for the Creutzfeldt–Jakob disease (CJD) supplied by the World Health Organization; however, the presence or absence of the 14-3-3 protein in the CSF is sometimes difficult to discern on a western blot because of equivocal bands. The goal of this study was to establish a standard 14-3-3 protein assay and to determine the threshold level of a 14-3-3 protein that can be assayed by western blot. We searched for the most suitable isoform of the 14-3-3 protein to test for in protein assays, and the most sensitive antibody among four antibodies with an affinity for 14-3-3. We measured the levels of all 14-3-3 isoforms in 112 patients with CJD and in 100 patients with other diseases. We compared the performances of four different antibodies. We carried out a semi-quantitative analysis of γ-isoform levels using the LAS 3000 system, which was capable of producing a digital image from the luminescence on a western blot. We determined that the most suitable isoform of the 14-3-3 protein for conducting a standardized assay was the γ-isoform. Among the four commercially available antibodies for this protein, the most sensitive and specific was 18647 (IBL, Japan). We report the high repeatability of the detection of the 14-3-3 protein by this antibody to the γ-isoform, showing that western blot can be used for semi-quantitative analysis.