Development of Passive Immunotherapies for Synucleinopathies

Immunotherapy using antibodies targeting alpha-synuclein has proven to be an effective strategy for ameliorating pathological and behavioral deficits induced by excess pathogenic alpha-synuclein in various animal and/or cellular models. However, the process of selecting the anti-alpha-synuclein antibody with the best potential to treat synucleinopathies in humans is not trivial. Critical to this process is a better understanding of the pathological processes involved in the synucleinopathies and how antibodies are able to influence these. We will give an overview of the first proof-of-concept studies in rodent disease models and discuss challenges associated with developing antibodies against alpha-synuclein resulting from the distribution and structural characteristics of the protein. We will also provide a status on the passive immunization approaches targeting alpha-synuclein that have entered, or are expected to enter, clinical evaluation.

Prion-Specific Antibodies Produced in Wild-Type Mice

Peptide-specific antibodies produced against synthetic peptides are of high value in probing protein structure and function, especially when working with challenging proteins, including not readily available, non-immunogenic, toxic, and/or pathogenic proteins. Here, we present a straightforward method for production of mouse monoclonal antibodies (MAbs) against peptides representing two sites of interest in the bovine prion protein (boPrP), the causative agent of bovine spongiform encephalopathy ("mad cow disease") and new variant Creutzfeldt-Jakob's disease (CJD) in humans, as well as a thorough characterization of their reactivity with a range of normal and pathogenic (misfolded) prion proteins. It is demonstrated that immunization of wild-type mice with ovalbumin-conjugated peptides formulated with Freund's adjuvant induces a good immune response, including high levels of specific anti-peptide antibodies, even against peptides very homologous to murine protein sequences. In general, using the strategies described here for selecting, synthesizing, and conjugating peptides and immunizing 4-5 mice with 2-3 different peptides, high-titered antibodies reacting with the target protein are routinely obtained with at least one of the peptides after three to four immunizations with incomplete Freund's adjuvant.

Urea and thiourea modified polypropyleneimine dendrimers clear intracellular α-synuclein aggregates in a human cell line

Synucleinopathies are neurodegenerative pathologies in which disease progression is closely correlated to brain accumulation of insoluble α-synuclein, a small protein abundantly expressed in neural tissue. Here, two types of modified polypropyleneimine (PPI) dendrimers having either urea or methylthiourea (MTU) surface functional groups were investigated in a cellular model of synucleinopathy. Dendrimers are synthetic macromolecules that may be produced in a range of well-defined molecular sizes. Using cellomics array scan high-content screening, we show that both types of dendrimers are able to significantly reduce intracellular levels of α-synuclein aggregates dependent on the concentration, the type and molecular size of the dendrimer with the bigger size MTU-dendrimers having the highest potency. The intracellular clearance of α-synuclein aggregates by dendrimers was achieved at noncytotoxic concentrations.

Tubulin polymerization-promoting protein (TPPP/p25α) promotes unconventional secretion of α-synuclein through exophagy by impairing autophagosome-lysosome fusion

Aggregation of α-synuclein can be promoted by the tubulin polymerization-promoting protein/p25α, which we have used here as a tool to study the role of autophagy in the clearance of α-synuclein. In NGF-differentiated PC12 catecholaminergic nerve cells, we show that de novo expressed p25α co-localizes with α-synuclein and causes its aggregation and distribution into autophagosomes. However, p25α also lowered the mobility of autophagosomes and hindered the final maturation of autophagosomes by preventing their fusion with lysosomes for the final degradation of α-synuclein. Instead, p25α caused a 4-fold increase in the basal level of α-synuclein secreted into the medium. Secretion was strictly dependent on autophagy and could be up-regulated (trehalose and Rab1A) or down-regulated (3-methyladenine and ATG5 shRNA) by enhancers or inhibitors of autophagy or by modulating minus-end-directed (HDAC6 shRNA) or plus-end-directed (Rab8) trafficking of autophagosomes along microtubules. Finally, we show in the absence of tubulin polymerization-promoting protein/p25α that α-synuclein release was modulated by dominant mutants of Rab27A, known to regulate exocytosis of late endosomal (and amphisomal) elements, and that both lysosomal fusion block and secretion of α-synuclein could be replicated by knockdown of the p25α target, HDAC6, the predominant cytosolic deacetylase in neurons. Our data indicate that unconventional secretion of α-synuclein can be mediated through exophagy and that factors, which increase the pool of autophagosomes/amphisomes (e.g. lysosomal disturbance) or alter the polarity of vesicular transport of autophagosomes on microtubules, can result in an increased release of α-synuclein monomer and aggregates to the surroundings.

Endogenous 2-oxoglutarate levels impact potencies of competitive HIF prolyl hydroxylase inhibitors

The stability and transcriptional activity of the hypoxia-inducible factors (HIFs) are regulated by oxygen-dependent hydroxylation that is catalyzed by three HIF prolyl 4-hydroxylases (HPHs). Use of HPH inhibition as a mean for HIF-upregulation has recently gained interest as a potential treatment paradigm against neurodegenerative diseases like ischemia and Parkinson's disease. In the present investigation we report the development of a new and robust assay to measure HPH activity. The assay is based on capture of hydroxylated peptide product by the von Hippel-Lindau protein which is directly measured in a scintillation proximity assay. In addition we describe the determination of HPH subtype potencies of HPH inhibitors which either directly or indirectly inhibit the HPH enzyme. The potencies of the HPH inhibitors displayed almost identical IC(50) values toward the HPH1 and HPH2 subtype while the potency against the HPH3 subtype was increased for several of the compounds. For the most potent compound, a hydroxyl thiazole derivative, the potency against HPH2 and HPH3 was 7nM and 0.49nM, respectively corresponding to a 14-fold difference. These results suggest that HPH subtype-selective compounds may be developed. In addition we determined the 2-oxoglutarate concentration in brain tissue and neuronal cell lines as 2-oxoglutarate is an important co-factor used by the HPH enzyme during the hydroxylation reaction. The high intracellular 2-oxoglutarate concentration provides an explanation for the diminished cellular HIF activating potency of a competitive HPH inhibitor compared to its orders of magnitude higher HPH inhibiting potency. The present reported data suggest that in the development of specific Hif prolyl hydroxylase inhibitors the high 2-oxoglutarate tissue level should be taken into account as this might affect the cellular potency. Thus to specifically inhibit the intracellular HPH enzymatic reaction a competitive inhibitor with a low Ki should be developed.

α-Synuclein propagates from mouse brain to grafted dopaminergic neurons and seeds aggregation in cultured human cells

Post-mortem analyses of brains from patients with Parkinson disease who received fetal mesencephalic transplants show that α-synuclein-containing (α-syn-containing) Lewy bodies gradually appear in grafted neurons. Here, we explored whether intercellular transfer of α-syn from host to graft, followed by seeding of α-syn aggregation in recipient neurons, can contribute to this phenomenon. We assessed α-syn cell-to-cell transfer using microscopy, flow cytometry, and high-content screening in several coculture model systems. Coculturing cells engineered to express either GFP- or DsRed-tagged α-syn resulted in a gradual increase in double-labeled cells. Importantly, α-syn-GFP derived from 1 neuroblastoma cell line localized to red fluorescent aggregates in other cells expressing DsRed-α-syn, suggesting a seeding effect of transmitted α-syn. Extracellular α-syn was taken up by cells through endocytosis and interacted with intracellular α-syn. Next, following intracortical injection of recombinant α-syn in rats, we found neuronal uptake was attenuated by coinjection of an endocytosis inhibitor. Finally, we demonstrated in vivo transfer of α-syn between host cells and grafted dopaminergic neurons in mice overexpressing human α-syn. In summary, intercellularly transferred α-syn interacts with cytoplasmic α-syn and can propagate α-syn pathology. These results suggest that α-syn propagation is a key element in the progression of Parkinson disease pathology.

Localization of disease-related PrP in Danish patients with different subtypes of prion disease

OBJECTIVE

The transmissible spongiform encephalopathies are characterized by vacuolization, neuronal loss, gliosis and deposition of a misfolded and Proteinase K resistant isoform of the prion protein (PrP(Sc)) in the central nervous system. METHODS MATERIALS AND PATIENTS: Paraffin-embedded tissue blot (PET-blot), immunohistochemistry (IHC) and Western blotting (WB) were combined to study the morphology and localization of disease related PrP in Danish patients with different subtypes of sporadic Creutzfeldt-Jakob disease, familiar Creutzfeldt-Jakob disease and Gerstmann-Sträussler-Scheinker disease.

RESULTS AND CONCLUSION

There was a good morphological and anatomical concordance between what was found with PET-blot and IHC in all patients. In some specific cases, the PET-blot was superior to IHC in sensitivity. To our knowledge, this is the first report where PET-blot analysis is applied to hereditary forms of human transmissible spongiform encephalopathies and compared with sporadic cases of Creutzfeldt-Jakob disease.

Bone marrow megakaryocytes and platelet kinetics in systemic lupus erythematosus. With special reference to corticosteroid and azathioprine therapy

The megakaryocyte number and mean megakaryocyte area were determined in histological sections of sternal bone marrow from 26 patients with systemic lupus erythematosus (SLE). Also 20 platelet survival studies were carried out in these patients. The results were analyzed with respect to corticosteroid (CS) and CS + azathioprine (AT) therapy. The mean bone marrow megakaryocyte number as highest in untreated SLE patients, slightly lower in patients receiving CSs and lowest in those receiving CSs + AT. The difference was, however, not significant. The mean megakaryocyte areas were smallest in untreated SLE patients, slightly larger in those treated with CSs and significantly (p less than 0.05) larger in patients who received CSs + AT than in untreated patients. Platelet production rate was normal in all 3 groups of SLE patients. The results suggest that CS and AT therapy in SLE intervenes with the bone marrow megakaryopoiesis without affecting the production rate of platelets.

Myelofibrosis and rapid thrombocytolysis. A case report

A 69-year-old woman was referred to our department because of moderate anemia and thrombocytopenia. On admission the spleen was slightly enlarged. On the basis of histological examination of biopsy specimens from spinal processes the diagnosis of myelofibrosis was made. The subsequent clinical course was progressively downhill. Although splenomegaly was of only moderate degree, severe anemia and thrombocytopenia supervened. Platelet mean life span was dramatically shortened (1.8 hours) and platelet production rate considerably increased (about 18xnormal). Neither corticosteroid therapy nor splenectomy alleviated the thrombocytopenia. Extremely large platelets, with diameters of up to 10 mum, were seen in the peripheral blood. The mean platelet diameter and percentage of megathrombocytes reached peak values about 2 weeks after splenectomy. It is suggested that the immunologic background of the rapid thrombocytolysis is similar to that which governs platelet destruction in idiopathic thrombocytopenic purpura.

Characterisation of new monoclonal antibodies reacting with prions from both human and animal brain tissues

Post-mortem diagnosis of transmissible spongiform encephalopathies (prion diseases) is primarily based on the detection of a protease resistant, misfolded disease associated isoform (PrP(Sc)) of the prion protein (PrP(C)) on neuronal cells. These methods depend on antibodies directed against PrP(C) and capable of reacting with PrP(Sc)in situ (immunohistochemistry on nervous tissue sections) or with the unfolded form of the protein (western and paraffin embedded tissue (PET) blotting). Here, high-affinity monoclonal antibodies (mAbs 1.5D7, 1.6F4) were produced against synthetic PrP peptides in wild-type mice and used for western blotting and immunohistochemistry to detect several types of human prion-disease associated PrP(Sc), including sporadic Creutzfeldt-Jakob Disease (CJD) (subtypes MM1 and VV2), familial CJD and Gerstmann-Sträussler-Scheinker (GSS) disease PrP(Sc) as well as PrP(Sc) of bovine spongiform encephalopathy (bovine brain), scrapie (ovine brain) and experimental scrapie in hamster and in mice. The antibodies were also used for PET-blotting in which PrP(Sc) blotted from brain tissue sections onto a nitrocellulose membrane is visualized with antibodies after protease and denaturant treatment allowing the detection of protease resistant PrP forms (PrP(RES)) in situ. Monoclonal antibodies 1.5D7 and 1.6F4 were raised against the reported epitope (PrP153-165) of the commercial antibody 6H4. While 1.5D7 and 1.6F4 were completely inhibitable by PrP153-165, 6H4 was not, indicating that the specificity of 6H4 is not defined completely by PrP153-165. The two antibodies performed similarly to 6H4 in western blotting with human samples, but showed less reactivity and enhanced background staining with animal samples in this method. In immunohistochemistry 1.5D7 and 1.6F4 performed better than 6H4 suggesting that the binding affinity of 1.5D7 and 1.6F4 with native (aggregated) PrP(Sc)in situ was higher than that of 6H4. On the other hand in PET-blotting, 6H4 reached the same level of reactivity as 1.5D7 and 1.6F4. This shows that 6H4 needs denatured PrP(RES) to reach maximal reactivity, confirming earlier results. As an exception, human PrP(RES) still reacted relatively poorly with 6H4 in PET-blotting, while 1.5D7 and 1.6F4 reacted well with PrP(RES) from most human CJD types. Taken together this implies that the binding epitope of 1.5D7 and 1.6F4 is accessible in the aggregates of undenatured PrP(Sc) (IHC) while the binding site of 6H4 is at least partly inaccessible. In techniques incorporating a denaturing and/or disaggregating step 6H4 showed good binding indicating increased accessibility of the binding site. An exception to this is human samples in PET-blotting suggesting that huPrP(RES) might not be as easily unfolded by denaturation as BSE and scrapie PrP(RES). Also of interest was the ability of 1.5D7 and 1.6F4 to discriminate between two allelic variants of PrP CJD(Sc) (VV vs. MM) in immunohistochemistry as opposed to the normally used antibody 3F4.

Oxidation reduces the fibrillation but not the neurotoxicity of the prion peptide PrP106-126

There is increasing evidence that soluble oligomers of misfolded protein may play a role in the pathogenesis of protein misfolding diseases including the transmissible spongiform encephalopathies (TSE) where the protein involved is the prion protein, PrP. The effect of oxidation on fibrillation tendency and neurotoxicity of different molecular variants of the prion peptide PrP106-126 was investigated. It was found that methionine oxidation significantly reduced amyloid fibril formation and proteinase K resistance, but it did not reduce (but rather increase slightly) the neurotoxicity of the peptides in vivo (electroretinography after intraocular injections in mice) and in vitro (in primary neuronal cultures). We furthermore found that the bovine variant of PrP106-126, containing only one methionine residue, showed both reduced fibril forming capacity and in vivo and in vitro neurotoxicity. The findings imply (I) that there is not a simple relation between the formation of amyloid fibrils and neurotoxicity of PrP106-126 derived peptides, (II) that putative, soluble, non-amyloid protofibrils, presumed to be present in increased proportions in oxidized PrP106-126, could play a role in the pathogenesis of TSE and III) that the number of methionine residues in the PrP106-126 peptide seems to have a pivotal role in determining the physical and biological properties of PrP106-126.

Amidation and structure relaxation abolish the neurotoxicity of the prion peptide PrP106-126 in vivo and in vitro

One of the major pathological hallmarks of transmissible spongiform encephalopathies (TSEs) is the accumulation of a pathogenic (scrapie) isoform (PrP(Sc)) of the cellular prion protein (PrP(C)) primarily in the central nervous system. The synthetic prion peptide PrP106-126 shares many characteristics with PrP(Sc) in that it shows PrP(C)-dependent neurotoxicity both in vivo and in vitro. Moreover, PrP106-126 in vitro neurotoxicity has been closely associated with the ability to form fibrils. Here, we studied the in vivo neurotoxicity of molecular variants of PrP106-126 toward retinal neurons using electroretinographic recordings in mice after intraocular injections of the peptides. We found that amidation and structure relaxation of PrP106-126 significantly reduced the neurotoxicity in vivo. This was also found in vitro in primary neuronal cultures from mouse and rat brain. Thioflavin T binding studies showed that amidation and structure relaxation significantly reduced the ability of PrP106-126 to attain fibrillar structures in physiological salt solutions. This study hence supports the assumption that the neurotoxic potential of PrP106-126 is closely related to its ability to attain secondary structure.

Light-induced phase shift in the Syrian hamster (Mesocricetus auratus) is attenuated by the PACAP receptor antagonist PACAP6-38 or PACAP immunoneutralization

Circadian rhythms generated by the suprachiasmatic nucleus (SCN) are daily adjusted (entrained) by light via the retinohypothalamic tract (RHT). The RHT contains two neurotransmitters, glutamate and pituitary adenylate cyclase-activating polypeptide (PACAP), which are believed to mediate the phase-shifting effects of light on the clock. In the present study we have elucidated the role of PACAP in light-induced phase shifting at early night in hamsters and shown that (i) light-induced phase delay of running-wheel activity was significantly attenuated by a specific PAC1 receptor antagonist (PACAP6-38) or by immunoblockade with a specific anti-PACAP antibody injected intracerebroventricularly before light stimulation; (ii) PACAP administered close to the SCN was able to phase-delay the circadian rhythm of running-wheel activity in a similar way to light; (iii) PACAP was present in the hamster RHT, colocalized with melanopsin, a recently identified opsin which has been suggested to be a circadian photopigment. The findings indicate that PACAP is a neurotransmitter of the RHT mediating photic information to the clock, possibly via melanopsin located exclusively on the PACAP-expressing cells of the RHT.

Urinary tract infection in children with type I diabetes

The prevalence and incidence of bacteriuria in 304 girls and 337 boys with type I diabetes was studied by screening for bacteriuria at their regular outpatient controls. In 90 girls and 108 boys a urine specimen was sampled every third month during a year. The prevalence of bacteriuria was 3/304 in girls and 0/337 in boys. During the one year follow-up one of the 90 girls had pyelonephritis and two cystitis while none of the boys had bacteriuria. It is concluded that the rate of urinary tract infection in young diabetic persons does not differ from that present in healthy young people.

Platelet kinetics in systemic lupus erythematosus (SLE), with special reference to corticosteroid and azathioprine therapy

Duplicate platelet survival studies were carried out on 10 patients with SLE. At the time of the first study 5 of them (group I) were untreated and the remaining 5 (group II) were receiving corticosteroid (CS) therapy. The second study was performed while group I patients received CS and group II patients CS + azathioprine (AT) treatment. Untreated SLE patients were shown to have normal values for platelet mean life-span (MLS) and platelet production rate. CS and AT treatment did not affect either platelet MLS or platelet production rate. The present study also provides further evidence that a state of compensated thrombocytolysis is not present in SLE.

Platelet survival and platelet production in systemic lupus erythematosus (SLE)

Platelet survival studies were carried out on 36 patients suffering from SLE. Twelve of them received no therapy, 17 were on corticosteroids (CS), and the remaining 7 received CS and azathioprin (AT). Ten healthy hospital employees served as controls. Only 1 of our SLE patients had thrombocytopenia (platelet count 42 x 10(9)/l). All the remaining 35 patients had venous platelet counts greater than or equal to 120 x 10(9)l. In the control group the average platelet mean life-span (MLS) was 5.8 +/- 0.3 (range 4.0-6.8) days. In the group of untreated SLE patients 3 out of 12 subjects (25%) had a platelet MLS below the lower range for the controls. The mean platelet MLS in the control group did not differ statistically from any of the means of the three groups of SLE patients studied. The lowest mean for platelet MLS (5.2 +/- 0.6 days) was encountered in the group of patients who received no therapy. The means for platelet MLS in the two groups of SLE patients who received immunosuppressive therapy were higher (6.5 +/- 0.4 and 6.6 +/- 0.4 days, respectively) but did not differ statistically from the mean of untreated patients (0.10 > p > 0.05). The mean platelet production rate in the control group (23 +/- 10(10) platelets per day) did not differ from any of the three groups of SLE patients investigated. In the literature it has been proposed that a state of compensated thrombocytolysis is present in most cases of SLE. The results of the present study do not support this hypothesis, however.

Thrombokinetics in giant cell arteritis, with special reference to corticosteroid therapy

Duplicate platelet survival studies were carried out on 8 patients with giant cell arteritis (GCA), once before the institution of any therapy, and the second time when they were in a completely asymptomatic phase after having received corticosteroid treatment. The time interval between the studies ranged between 5 and 14 months. In the first study the mean peripheral platelet count was 486 +/- 25 X 10(9)/l and in the second 326 +/- 25 X 10(9)/l. The difference between the means was highly significant (P less than 0.001). The mean life-span of the platelets was normal in the duplicate experiments (6.7 +/- 0.3 and 7.3 +/- 0.4 days, respectively). Platelet production rate was significantly (P less than 0.001) raised in the first experiment but became normal in response to corticosteroid therapy. It is concluded that the thrombocytosis seen in GCA is reactive to the inflammation present in this disease, and it seems reasonable to assume that the reduction in the peripheral platelet count which occurs in response to corticosteroid therapy accurately reflects the clinical improvement of the patient.

Metoprolol and the peripheral platelet count

An acute oral administration of 50 mg metoprolol (a selective beta-1-receptor antagonist) to 18 healthy volunteers induced a significant increase in the peripheral platelet concentration lasting more than 4 h. It is suggested that this increment in the platelet count originates from the exchangeable splenic platelet pool. The mechanism by which metoprolol exerts its effect remains to be established.

Thrombokinetics in systemic lupus erythematosus A preliminary report

Twelve non-thrombocytopenic patients ( 3 males and 9 females) with systemic lupus erythematosus (SLE) were investigated with respect to platelet size, percentage of megathrombocytes, platelet survival and platelet production. The values for platelet size and percentage of megathrombocytes did not differ from those of a control group. In the SLE group the mean platelet MLS was identical to the control mean, and all patients with SLE had values for platelet MLS within the range of the control subjects. All SLE patients but one had values for platelet turnover within the control range. For unclear reason one single SLE patient had a moderately elevated platelet turnover value. The results of the present investigation do not support the theory that a state of compensated thrombocytolysis is present in SLE.