Suppression of viral RNA polymerase activity is necessary for persistent infection during the transformation of measles virus into SSPE virus.

Subacute sclerosing panencephalitis (SSPE) is a fatal neurodegenerative disease caused by measles virus (MV), which typically develops 7 to 10 years after acute measles. During the incubation period, MV establishes a persistent infection in the brain and accumulates mutations that generate neuropathogenic SSPE virus. The neuropathogenicity is closely associated with enhanced propagation mediated by cell-to-cell fusion in the brain, which is principally regulated by hyperfusogenic mutations of the viral F protein. The molecular mechanisms underlying establishment and maintenance of persistent infection are unclear because it is impractical to isolate viruses before the appearance of clinical signs. In this study, we found that the L and P proteins, components of viral RNA-dependent RNA polymerase (RdRp), of an SSPE virus Kobe-1 strain did not promote but rather attenuated viral neuropathogenicity. Viral RdRp activity corresponded to F protein expression; the suppression of RdRp activity in the Kobe-1 strain because of mutations in the L and P proteins led to restriction of the F protein level, thereby reducing cell-to-cell fusion mediated propagation in neuronal cells and decreasing neuropathogenicity. Therefore, the L and P proteins of Kobe-1 did not contribute to progression of SSPE. Three mutations in the L protein strongly suppressed RdRp activity. Recombinant MV harboring the three mutations limited viral spread in neuronal cells while preventing the release of infectious progeny particles; these changes could support persistent infection by enabling host immune escape and preventing host cell lysis. Therefore, the suppression of RdRp activity is necessary for the persistent infection of the parental MV on the way to transform into Kobe-1 SSPE virus. Because mutations in the genome of an SSPE virus reflect the process of SSPE development, mutation analysis will provide insight into the mechanisms underlying persistent infection.

Upregulation of viral RNA polymerase activity promotes adaptation of SSPE virus to neuronal cells.

Subacute sclerosing panencephalitis (SSPE) is a rare progressive neurodegenerative disease caused by measles virus variants (SSPE viruses) that results in eventual death. Amino acid substitution(s) in the viral fusion (F) protein are key for viral propagation in the brain in a cell-to-cell manner, a specific trait of SSPE viruses, leading to neuropathogenicity. In this study, we passaged an SSPE virus in cultured human neuronal cells and isolated an adapted virus that propagated more efficiently in neuronal cells and exhibited increased cell-to-cell fusion. Contrary to our expectation, the virus harbored mutations in the large protein, a viral RNA-dependent RNA polymerase, and in the phosphoprotein, its co-factor, rather than in the F protein. Our results imply that upregulated RNA polymerase activity, which increases F protein expression and cell-to-cell fusion, could be a viral factor that provides a growth advantage and contributes to the adaptation of SSPE viruses to neuronal cells.

M protein of subacute sclerosing panencephalitis virus, synergistically with the F protein, plays a crucial role in viral neuropathogenicity.

Subacute sclerosing panencephalitis (SSPE) is a rare fatal neurodegenerative disease caused by a measles virus (MV) variant, SSPE virus, that accumulates mutations during long-term persistent infection of the central nervous system (CNS). Clusters of mutations identified around the matrix (M) protein in many SSPE viruses suppress productive infectious particle release and accelerate cell-cell fusion, which are features of SSPE viruses. It was reported, however, that these defects of M protein function might not be correlated directly with promotion of neurovirulence, although they might enable establishment of persistent infection. Neuropathogenicity is closely related to the character of the viral fusion (F) protein, and amino acid substitution(s) in the F protein of some SSPE viruses confers F protein hyperfusogenicity, facilitating viral propagation in the CNS through cell-cell fusion and leading to neurovirulence. The F protein of an SSPE virus Kobe-1 strain, however, displayed only moderately enhanced fusion activity and required additional mutations in the M protein for neuropathogenicity in mice. We demonstrated here the mechanism for the M protein of the Kobe-1 strain supporting the fusion activity of the F protein and cooperatively inducing neurovirulence, even though each protein, independently, has no effect on virulence. The occurrence of SSPE has been estimated recently as one in several thousand in children who acquired measles under the age of 5 years, markedly higher than reported previously. The probability of a specific mutation (or mutations) occurring in the F protein conferring hyperfusogenicity and neuropathogenicity might not be sufficient to explain the high frequency of SSPE. The induction of neurovirulence by M protein synergistically with moderately fusogenic F protein could account for the high frequency of SSPE.

Antiviral Effect of Favipiravir (T-705) against Measles and Subacute Sclerosing Panencephalitis Viruses.

Subacute sclerosing panencephalitis (SSPE) is a late-onset, intractable, and fatal viral disease caused by persistent infection of the central nervous system with a measles virus mutant (SSPE virus). In Japan, interferon-α and ribavirin are administered intracerebroventricularly to patients with SSPE. However, as the therapeutic effect is insufficient, more effective drugs are needed. Favipiravir, which is clinically used as an anti-influenza drug, demonstrates anti-viral effects against RNA viruses. In this study, the antiviral effect of favipiravir against measles virus (Edmonston strain) and SSPE virus (Yamagata-1 strain) was examined in vitro. The 50% effective concentration (EC50) of favipiravir (inhibiting viral plaque formation by 50%) against Edmonston and Yamagata-1 strains were 108.7 ± 2.0 µM (17.1 ± 0.3 µg/mL) and 38.6 ± 6.0 µM (6.1 ± 0.9 µg/mL), respectively, which were similar to those of ribavirin. The antiviral activity of favipiravir against the SSPE virus was demonstrated for the first time in this study.

Genetic characterization of measles virus genotype D6 subacute sclerosing panencephalitis case, Alberta, Canada.

Subacute sclerosing panencephalitis (SSPE) is a progressive and eventually fatal neurological disease arising from a persistent infection with measles virus (MV) acquired at a young age. SSPE measles virus strains are defective and unable to produce progeny virions, due to multiple and extensive mutations in a number of key genes. We sequenced the full MV genome from our recently reported SSPE case, which typed as genotype D6, and compared it with other genotype D6 wild type and SSPE sequences. The Alberta D6 strain was significantly different from other reported SSPE D6 sequences. Mutations were observed in all the genes of the Alberta strain, with the greatest sequence divergence noted in the M gene with 17.6% nucleotide and 31% amino acid variation. The L gene showed the least variation with 1.3% nucleotide and 0.7% amino acid differences respectively. The nucleotide variability for 15,672 bases of the complete genome compared to the wild type and other SSPE D6 strains was around 3%.

The first genetic characterization of a D4 measles virus strain derived from a patient with subacute sclerosing panencephalitis.

Measles virus (MV) strains derived from patients with subacute sclerosing panencephalitis (SSPE), SSPE strains, possess numerous mutations when compared to viruses belonging to the same genotype and circulating in similar time period. Although many SSPE strains have been extensively characterized, none of them belongs to D4 genotype which currently predominates in Europe where it has caused a number of recent outbreaks/epidemics. We sequenced an MV derived from a patient with long-term SSPE; the virus was named MVs/Zagreb.CRO/30.06[D4] (SSPE). Initial genetic analysis showed that it belongs to D4 genotype. The sequences of genes encoding matrix and fusion proteins indicate premature protein terminations. Putative hemagglutin (H) protein is lengthened for 20 amino acids, which is the longest H protein elongation so far found in SSPE viruses. Nucleotides 1421 A, 1422 G, 1507 C and 1542 C in nucleoprotein gene open reading frame seem to be specific for this D4 strain, differentiating it from other D4 non-SSPE strains. Besides, a unique mutation at position 543 of H protein was found, histidine instead of tyrosine. As persistent MV infections are initially established by "normal" wild-type MV strains, the presented comparative analyses describe alterations that could be involved in the maintenance of persistent infection, disease development and progression.

[Subacute sclerosing panencephalitis cases diagnosed by increased CSF/serum measles antibody indices]. / Yüksek BOS/Serum Kizamik Antikor Indeksi ile Tanimlanan Subakut Sklerozan Panensefalit Olgulari

Subacute sclerosing panencephalitis (SSPE) caused by persistent defective measles virus strains, is a progressive neurological disorder of children and adolescents. The aim of this letter was to share the data from SSPE-suspected cases who were definitely diagnosed by the detection of increased antibody index in serum and cerebrospinal fluid (CSF) samples. A total of 11 patients (mean age: 14.3 years) with suspected SSPE between February 2006 to August 2008, were included in the study. Simultaneously obtained serum and CSF samples from patients were analyzed in terms of albumin, total IgG and measles-specific IgG levels (Measles Virus IgG ELISA for CSF Diagnostics, Euroimmun, Germany). The value of CSQrel (relative CSF/serum quotient) ≥ 1.5 was accepted indicative for intrathecal measles antibody synthesis. Seven (63.6%) of the 11 patients' diagnosis were confirmed with the demonstration of elevated CSF/serum indices (CSQrel range: 2.3-36.9; mean: 12.9). Mean age of those seven cases was 12.3 years (age range: 7-21) and four of them were male. The history of patients with high antibody indices indicated that three of four patients who had measles infection had not been vaccinated against measles. These three unvaccinated patients had measles infection at 3rd, 8th and 30th months of age, respectively, and the period of SSPE development were 15, 6 and 4.5 years, respectively. With this letter we would like to emphasize once more that effective measles vaccination is the only way for the prevention of measles and SSPE and the demonstration of increased measles antibody index in simultaneously obtained serum and CSF samples is crucial for the diagnosis of SSPE.

[Anti SSPE drugs].

Subacute sclerosing panencephalitis (SSPE) is a progressive and fatal central nervous system disorder that results from a persistent SSPE virus infection. Compound which inhibits the replication of SSPE virus might be a candidate for the specific drug for SSPE. Out of several compounds which had been tried for the treatment of SSPE, two drugs, i.e., inosiplex and interferon-alpha, were reported to be effective. Those drugs, however, could not cure the disease. Recently, ribavirin therapy has been proposed as novel antiviral chemotherapy for SSPE. By intraventricular administration, ribavirin level in CSF reaches a concentration at which ribavirin could completely inhibit the replication of SSPE virus. Thus, intraventricular ribavirin therapy might eradicate SSPE virus from the CNS and stop the progression of SSPE syndrome. The therapeutic efficacy should be evaluated in the patients who are treated with the therapy at an early stage of SSPE.

Forma de presentación atípica de panencefalitis esclerosante subaguda del sarampión en el adulto / Atypical presentation of adult-age onset subacute sclerosing panencephalitis

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RNA editing enzyme adenosine deaminase is a restriction factor for controlling measles virus replication that also is required for embryogenesis.

Measles virus (MV), a member of the family Paramyxoviridae and an exclusively human pathogen, is among the most infectious viruses. A progressive fatal neurodegenerative complication, subacute sclerosing panencephalitis (SSPE), occurs during persistent MV infection of the CNS and is associated with biased hypermutations of the viral genome. The observed hypermutations of A-to-G are consistent with conversions catalyzed by the adenosine deaminase acting on RNA (ADAR1). To evaluate the role of ADAR1 in MV infection, we selectively disrupted expression of the IFN-inducible p150 ADAR1 isoform and found it caused embryonic lethality at embryo day (E) 11-E12. We therefore generated p150-deficient and WT mouse embryo fibroblast (MEF) cells stably expressing the MV receptor signaling lymphocyte activation molecule (SLAM or CD150). The p150(-/-) but not WT MEF cells displayed extensive syncytium formation and cytopathic effect (CPE) following infection with MV, consistent with an anti-MV role of the p150 isoform of ADAR1. MV titers were 3 to 4 log higher in p150(-/-) cells compared with WT cells at 21 h postinfection, and restoration of ADAR1 in p150(-/-) cells prevented MV cytopathology. In contrast to infection with MV, p150 disruption had no effect on vesicular stomatitis virus, reovirus, or lymphocytic choriomeningitis virus replication but protected against CPE resulting from infection with Newcastle disease virus, Sendai virus, canine distemper virus, and influenza A virus. Thus, ADAR1 is a restriction factor in the replication of paramyxoviruses and orthomyxoviruses.

Synthesis, tautomerism, and antimicrobial, anti-HCV, anti-SSPE, antioxidant, and antitumor activities of arylazobenzosuberones.

2-Dimethylaminomethylene-1-benzosuberone 1 was coupled with diazotized aniline derivatives to afford a series of the hitherto unreported 2-arylazo-1-benzosuberones 3a-i. The tautomeric structure and the effect of substituents on the tautomeric form (s) of the products 3a-i were discussed. Similar coupling of the enaminone 1 with diazonium salts of heterocyclic amines gave the respective fused azolotriazino-benzosuberones. Some of the newly synthesized compounds showed potent antimicrobial, anti-HCV, antioxidant, antitumor (as topoisomerase I inhibitors), and antimicrobial activities.

Adult fulminant subacute sclerosing panencephalitis: pathological and molecular studies--a case report.

Subacute sclerosing panencephalitis is an uncommon progressive neurological disorder caused by a persistent defective measles virus, typically affecting children. We describe a case of fulminant subacute sclerosing panencephalitis in a 25-year-old male. Brain tissue biopsy showed histologic evidence of encephalitis with eosinophilic intranuclear inclusion bodies (Cowdry Type A and B), intracytoplasmic inclusion bodies, perivascular lymphoplasmacytic infiltration and gliosis. Immunohistochemical studies were positive using an anti-measles antibody. Reverse transcriptase-PCR detected measles virus RNA and phylogenetic analysis indicated a C2 genotype. The rare adult-onset form is often atypical and difficult to diagnose and should be included in the differential diagnosis of subacute "unexplained" neurological diseases and uncommon infectious disorders.

Bilateral macular retinitis as the presenting feature of subacute sclerosing panencephalitis.

Two patients presented with retinitis as the initial clinical manifestation of subacute sclerosing panencephalitis (SSPE), a delayed neurologic complication of measles. In one patient, the ocular involvement preceded the neurologic symptoms by 4 weeks and in the other patient by 4 years. The diagnosis of SSPE was suspected when neuropsychiatric manifestations appeared and was confirmed by the typical panencephalitic electroencephalography changes, neuroimaging features of panencephalitis, and high titers of measles antibodies in serum and cerebrospinal fluid. Although SSPE is an untreatable illness, recognition of this unusual presentation is valuable to allow earlier diagnosis and institution of palliative measures.

Generation of recombinant adenovirus expressing siRNA against the L mRNA of measles virus and subacute sclerosing panencephalitis virus.

Subacute sclerosing panencephalitis (SSPE) is a fatal neurodegenerative disease caused by prolonged persistent infection of the central nervous system with a measles virus (MV) mutant called SSPE virus. At present, there is no effective treatment to completely cure SSPE and development of a new therapeutic measure(s) against this fatal slow virus infection is needed. We previously reported that replication of MV and SSPE virus was effectively inhibited by small interfering RNA (siRNA), either chemically synthetic or plasmid-driven ones, that were targeted against different sequences of the mRNA for the L protein of MV. In this study, we have generated recombinant adenovirus expressing the siRNAs (rAd-siRNA-MV-L2, -L4 and -L5) and demonstrated that these rAd-siRNAs efficiently inhibited replication of MV and SSPE virus in a dose-dependent manner. Due to their high capacity for gene delivery to nerve cells and the potential to inhibit SSPE virus replication, the rAd-siRNAs could be a good candidate for a novel therapeutic measure against SSPE.

[SSPE virus and pathogenesis].

Subacute sclerosing panencephalitis (SSPE) is caused by particular mutants of measles virus, which are often referred to as SSPE virus. SSPE virus is characterized by (i) the inability to produce infectious viral particles, (ii) the neuropathogenicity in animal models as well as in humans, and (iii) the prolonged persistence in vivo over many years. The viral genome exhibits particular mutations, called biased hypermutation, most notably in the M gene, followed by the F and H genes. Consequently, the M, F and H proteins are mutated, which is thought to account for the characteristic features of SSPE virus. The possible mechanism of long-term persistence of the virus after the recovery of measles is also discussed.

[Development of animal model for understanding of pathogenesis of subacute sclerosing panencephalitis using non-human primates].

Many animal models using experimental small animals for subacute sclerosing panencephalitis (SSPE) had been reported. But these models were not enough for understanding of pathogenesis of SSPE. After pathogenic measles virus was isolated with highly susceptible B95a cells, mimic infection of measles in human beings became easily produced in non-human primates. In this article, our attempt to develop SSPE model using cynomolgus monkeys will be introduced.

Full-length sequence analysis of subacute sclerosing panencephalitis (SSPE) virus, a mutant of measles virus, isolated from brain tissues of a patient shortly after onset of SSPE.

Subacute sclerosing panencephalitis (SSPE) virus, a measles virus (MeV) mutant, was isolated from brain tissues of a patient shortly after the clinical onset, and the entire viral genome was sequenced. The virus, named SSPE-Kobe-1, formed syncytia on B95a and Vero/SLAM cells without producing cell-free infectious virus particles, which is characteristic of SSPE virus. Phylogenetic analysis classified SSPE-Kobe-1 into genotype D3. When compared with an MeV field isolate of the same genotype (Ich-B strain), SSPE-Kobe-1 exhibited mutation rates of 0.8-1.6% at the nucleotide level in each of the proteincoding regions of the viral genome. It is noteworthy that the mutation rate of the M gene (1.2%) of SSPE-Kobe-1 was considerably lower than for other SSPE virus strains reported so far, but that the majority of the mutations (75%) were the uridine-to-cytidine biased hypermutation characteristic of the SSPE virus M gene. At the amino acid level, the viral proteins, such as N, P, C, V, M, F, H and L proteins, had point-mutations on 3, 7, 1, 4, 3, 9, 8 and 14 residues, respectively, compared with the Ich-B strain. In addition, the F and H proteins had mutated C-termini due to single-point mutations near or at the stop codons. Two of the three mutations in the M protein were Leu-to-Pro mutations, which are likely to affect the conformation and, therefore, the function of the protein. Because of the relatively small number of mutations, SSPE-Kobe-1 would be a useful tool to study genetic evolution of SSPE virus.

Measles viral load may reflect SSPE disease progression.

Subacute sclerosing panencephalitis (SSPE) is a rare, slowly progressive neurological disorder caused by the persistent infection with measles virus (MV). Despite much research into SSPE, its pathology remains obscure. We examined autopsy tissues of eight SSPE patients by real time quantitative PCR, immunohistochemistry and immunoblotting to determine viral load. MV N, M and H gene RNA could be detected in the central nervous system (CNS) of all patients and in two non-CNS tissues of one patient. The viral burden between patients differed up to four-fold by quantitative PCR and corresponded with detection of MV protein. The level of both viral RNA and antigen in the brain may correlate with disease progression.