Emi Takashita

Reactivation of Herpes Simplex Virus Type 1 and Varicella‐Zoster Virus and Therapeutic Effects of Combination Therapy With Prednisolone and Valacyclovir in Patients With Bell's Palsy

Objectives: To determine whether reactivation of herpes simplex virus (HSV) type 1 or varicella‐zoster virus (VZV) is the main cause of Bells palsy and whether antiviral drugs bring about recovery from Bells palsy.

Detection of ion channel activity in Xenopus laevis oocytes expressing Influenza C virus CM2 protein

Summary.To demonstrate the ion channel activity of Influenza C virus CM2, we expressed this protein in oocytes of Xenopus laevis and measured whole cell currents by a two-electrode voltage-clamp method. It was found that the inward currents were induced upon hyperpolarizing the oocyte membranes. The amplitude of the currents increased slowly with time during the hyperpolarizing pulse, and the current-voltage relationship was nonlinear, having a slope that increased with the level of hyperpolarization. These results suggest strongly that CM2 forms a voltage-activated ion channel. The current amplitude was increased to a small extent by lowering the external pH. We also found that the anti-influenza A virus drug amantadine hydrochloride failed to attenuate the inward currents of CM2-expressing oocytes induced by hyperpolarization. The reversal voltage of tail currents was affected by the reduction of [Cl−], but neither by the change of [Na+] nor by that of [K+]. Furthermore, the amplitude of the inward currents was decreased by an anion channel blocker. The data presented here suggest that CM2 protein forms a voltage-activated ion channel permeable to chloride ion.

Characterization of antigenically and genetically similar influenza C viruses isolated in Japan during the 1999-2000 season.

Between October 1999 and May 2000, a total of 28 strains of influenza C virus were isolated in four Japanese prefectures: Yamagata, Miyagi, Saitama and Hiroshima. Antigenic analysis showed that the 28 isolates were divided into three distinct antigenic groups, and viruses belonging to different antigenic groups were co-circulating in each of the four prefectures. Phylogenetic analysis of the seven protein genes demonstrated that the viruses having a similar genome composition spread in various areas of Japan during the same period. Furthermore, phylogenetic analysis showed that most of the influenza C viruses isolated in various areas of the world between the 1970s and 1980s were closely related to the contemporary Japanese viruses in all gene segments. These observations suggest that the influenza C viruses cause epidemics in some communities during the same season and that antigenically and genetically similar influenza C viruses spread throughout Japan and may be circulating worldwide.

Intracellular localization of influenza C virus NS2 protein (NEP) in infected cells and its incorporation into virions

RNA segment 7 of influenza C virus encodes two non-structural (NS) proteins, NS1 and NS2. The influenza C virus NS2 protein has been proposed to possess nuclear export activity like that of influenza A and B virus NS2 proteins (NEP). In the present study, we investigated the kinetics and localization of the NS2 protein in influenza C virus-infected cells, and analysed whether NS2 is present in virions. Immunofluorescent staining analysis of the infected cells indicated that NS2 was localized in the nucleus immediately after synthesis and predominantly in the cytoplasm in the later stages of infection. Confocal microscopy revealed that a part of the NS2 protein was colocalized with nucleoprotein NP/vRNP in the cytoplasm and on the cell membrane in the late stages of infection. The NS2 protein was detected in influenza C virions purified by gradient centrifugations and/or affinity chromatography. Trypsin treatment demonstrated that the NS2 protein was present inside the viral envelope. Furthermore, glycerol gradient analysis of detergent-solubilized virions revealed that the NS2 protein cosedimented with vRNPs. These data suggest that the influenza C virus NS2 protein is incorporated into virions, where it associates with vRNP.

Location of a linear epitope recognized by monoclonal antibody S16 on the hemagglutinin-esterase glycoprotein of influenza C virus.

We reported previously that monoclonal antibody S16, which had been raised against the hemagglutinin-esterase (HE) glycoprotein of influenza C/Ann Arbor/1/50 (AA/50) virus, recognizes a linear epitope present on the HE molecules of all influenza C viruses examined except for viruses belonging to a lineage represented by Aichi/1/81 (AI/81). Comparison of the deduced amino acid sequence of HE between viruses on the AI/81-related lineage and those on the others suggests that the epitope recognized by S16 is located in a region containing amino acid residue 403 and that a change from Glu to Lys at this position causes the loss of reactivity with the antibody. To prove it, the wild type (WT) HEs of AA/50 and AI/81 as well as their mutants with an amino acid substitution at residue 403 were expressed in CV-1 cells from the recombinant simian virus 40 (SV40) and tested for reactivity with S16 by immunoprecipitation. The results showed that the AA/50 virus WT and AI/81 virus mutant HEs (both having Glu at residue 403) were reactive with S16 whereas the AI/81 virus WT and AA/50 virus mutant HEs (both having Lys at residue 403) were not. Furthermore, we examined the reactivity of S16 with two synthetic peptides (corresponding to residues 397-409) that possess Glu and Lys at position 403, respectively, by enzyme-linked immunosorbent assays. The results demonstrated that the former peptide but not the latter was reactive with S16. These observations support strongly the notion described above. During this study it was also found that S16 cross-reacts with large T antigen of SV40.

Biochemical properties of the P42 protein encoded by RNA segment 6 of Influenza C virus

Summary.P42, encoded by a colinear transcript of Influenza C virus RNA segment 6 (M gene), is an integral membrane protein which is cleaved by signal peptidase to generate M1′ and CM2 composed of N-terminal 259 amino acids and C-terminal 115 amino acids, respectively. Herein, the biochemical features of P42 were investigated. N-glycosylated form of P42, designated P44, forms disulphide-linked dimers and tetramers. P44 is transported to the Golgi apparatus, but not to the trans-Golgi, since P44 is completely sensitive to endoglycosidase H. P44 and P42 are unstable irrespective of N-glycosylation or oligomerization. 26S proteasome inhibitor, lactacystin prevented the degradation of P42 as well as M1′, but not that of P44 efficiently, suggesting that P44 is degraded by another protease besides the 26S proteasome.