Distribution of Human Sapovirus Strain Genotypes over the last four Decades in Japan: a Global Perspective

Sapovirus (SaV) infections are a public health problem because they cause acute gastroenteritis in humans of all ages both as outbreaks and in sporadic cases. However, publicly-available SaV sequence information, especially whole genome sequences for all the SaV genotypes, is still limited. Therefore, in this study, we determined the full/near-full-length genomic sequences of 138 SaVs from the 2001-2015 seasons in 13 prefectures across Japan. The GI genogroup was predominant (67%, n = 92), followed by GII (18%, n = 25), GIV (9%, n = 12), and GV (6%, n = 9). Within the GI genogroup, four different genotypes were identified, as follows: GI.1 (n=44), GI.2 (n=40), GI.3 (n=7), and GI.5 (n=1). We then compared these Japanese SaV sequences with a total of 3119 public human SaV sequences from 49 countries over the last 46 years. The results indicated that GI.1 and GI.2 have been the predominant genotypes in Japan as well as in other countries over at least four decades. Together with public SaV sequences, the 138 newly determined Japanese SaV sequences could facilitate a better understanding of the evolutionary patterns of SaV genotypes.

A novel nairovirus associated with acute febrile illness in Hokkaido, Japan

The increasing burden of tick-borne orthonairovirus infections, such as Crimean-Congo hemorrhagic fever, is becoming a global concern for public health. In the present study, we identify a novel orthonairovirus, designated Yezo virus (YEZV), from two patients showing acute febrile illness with thrombocytopenia and leukopenia after tick bite in Hokkaido, Japan, in 2019 and 2020, respectively. YEZV is phylogenetically grouped with Sulina virus detected in Ixodes ricinus ticks in Romania. YEZV infection has been confirmed in seven patients from 2014–2020, four of whom were co-infected with Borrelia spp. Antibodies to YEZV are found in wild deer and raccoons, and YEZV RNAs have been detected in ticks from Hokkaido. In this work, we demonstrate that YEZV is highly likely to be the causative pathogen of febrile illness, representing the first report of an endemic infection associated with an orthonairovirus potentially transmitted by ticks in Japan.

Here, Kodama et al. describe the discovery, isolation and characterization of a novel tick-borne orthonairovirus, designated Yezo virus (YEZV), from patients with an acute febrile illness in Japan. Serological testing of wildlife and molecular screening of ticks suggest an endemic circulation of YEZV in Japan.

Detection of Measles Virus Genotypes B3, D4, D5, D8, and H1 in the Surveillance System in Hokkaido, Japan, 2006-2015, the Last Decade toward the Elimination

Measles is an acute and highly contagious disease caused by measles virus (MeV). The government of Japan, following the last epidemic in 2007 and 2008, which was caused by genotype D5 strains, introduced a catch-up-vaccination program for teenagers during Japan fiscal years 2008-2012 and a mandatory case-based reporting system for the nationwide elimination. Furthermore, laboratory confirmation of measles cases by genotyping of isolates has been performed to clarify the source of infection and support the interruption of measles cases. Owing to these preventive measures, the number of measles cases has been steadily decreasing after the last epidemic. In March 2015, Japan was internationally verified as having achieved measles elimination by the World Health Organization Regional Office for the Western Pacific. The continuous elimination of measles and high levels of vaccination coverage for MeV have been maintained nationally. However, imported or import-associated cases of measles have sporadically occurred during this time. After the last nationwide epidemic, 17 imported or import-associated measles cases (MeV strains identified as genotypes H1, D4, D8, and B3) were reported in Hokkaido, the northern islands of Japan. In this study, we present the occurrence of measles and surveillance activities in Hokkaido during 2006-2015.

Evaluation of sensitivity of TaqMan RT-PCR for rubella virus detection in clinical specimens

BACKGROUND

An easy and reliable assay for detection of the rubella virus is required to strengthen rubella surveillance. Although a TaqMan RT-PCR assay for detection of the rubella virus has been established in Japan, its utility for diagnostic purposes has not been tested.

OBJECTIVES

To allow introduction of the TaqMan RT-PCR into the rubella surveillance system in Japan, the sensitivity of the assay was determined using representative strains for all genotypes and clinical specimens.

STUDY DESIGN

The detection limits of the method for individual genotypes were examined using viral RNA extracted from 13 representative strains. The assay was also tested at 10 prefectural laboratories in Japan, designated as local reference laboratories for measles and rubella, to allow nationwide application of the assay.

RESULTS

The detection limits and amplification efficiencies of the assay were similar among all the representative strains of the 13 genotypes. The TaqMan RT-PCR could detect approximately 90% of throat swab and urine samples taken up to 5days of illness. These samples were determined positive by a highly sensitive nested RT-PCR.

CONCLUSIONS

The TaqMan RT-PCR could detect at least 10 pfu of rubella virus. Although the sensitivity was somewhat lower than that of the conventional nested RT-PCR, the TaqMan RT-PCR could be more practical to routine tests for rubella laboratory diagnosis and detection in view of the rapid response and reducing risks of contamination.

Recent progress toward measles elimination in Hokkaido, Japan, during 2011-2012

Laboratory diagnoses for measles were performed in a total of 97 cases in Hokkaido, Japan, during 2011-2012. Two patients were confirmed to be positive for measles virus (MV), both of whom lived in the Iburi district of Hokkaido. Molecular analysis of the nucleotide sequences of the nucleoprotein (N) gene revealed that these 2 strains had high homology with each other and belonged to the genotype D8. The onset interval of these cases and epidemiological data suggested that MV transmission had occurred between them and then terminated. Phylogenetic analysis of the N gene revealed that the strains identified in Hokkaido were classified into a cluster that contained many genotype D8 strains that were detected within a large area of Japan. Eventually, 9 cases were officially reported as measles. However, other than the abovementioned 2 cases, no genetic information regarding MV was obtained. In future, further active surveillance combined with the genetic investigation should be required in all suspected measles cases to verify the elimination status.

Epidemiology and laboratory diagnoses of rubella in Hokkaido district during the Nationwide Outbreak in Japan, 2011-2013

We report the epidemiology and laboratory diagnostic results of rubella cases from 2011 to 2013 in Hokkaido district, Japan. A total of 150 cases were officially reported as rubella; 102 (68%) involved males and 48 (32%) involved females. The highest proportion of cases were notified in 40-49-year-old age group among males and the 20-29-years-old age group among females. Forty-six cases (25 males and 21 females) had not been vaccinated, and 17 had been vaccinated, whereas 87 had the unknown vaccination status. Eighty-three cases (55.3%) showed the 3 typical principal rubella symptoms (fever, rash, and lymphadenopathy). Seven, 11, 92, and 40 cases were identified in the northern, eastern, central, and southern areas of Hokkaido district, respectively. In the central and southern areas of Hokkaido district, endemic rubella transmissions were indicated by both the epidemiological survey and molecular analyses. However, these outbreaks terminated spontaneously and did not expand to other areas of Hokkaido district. Fortunately, no congenital rubella syndrome (CRS) cases were reported during this observation period. However, to control virus transmission, prevent CRS, and maintain the routine vaccination program, the immediate introduction of an immunization strategy is required for susceptible individuals, particularly young adults.

Usefulness of the rapid determination system of viral genome sequences in human stool specimens

The rapid determination system of viral genome sequences (the RDV method) consists of detecting and determining the nucleotide sequences of viral genomes without using specific primers. To evaluate the usefulness of the RDV method, the detection of human norovirus (NV) genomes in stool specimens was investigated. In addition, the effect of nuclease treatment of the process was examined. A total of 23 human stool specimens were used, all of which were collected from patients with acute viral gastroenteritis, and were shown to contain NV genomes and also determined the cDNA copy numbers by the real-time reverse transcriptase-polymerase chain reaction. NV genomes were detected by the RDV method with nuclease treatment in nine specimens containing cDNA copies ranging between 6.2×10(9) and 9.8×10(11)/g stool. In contrast, NV genome was found by the method in 15 specimens without nuclease treatment and the number of NV cDNA copies ranged between 1.2×10(6) and 9.8×10(11)/g stool. These results suggest that the RDV method has potential for detecting viral genomes in stool specimens. The procedure without a step of nuclease treatment appears to be sensitive.

The JC virus-like particle overlay assay

JC virus (JCV) belongs to the family of double-stranded DNA polyomaviruses and in humans causes a demyelinating disease of the central nervous system, progressive multifocal leukoencephalopathy (PML). It has been reported that sialic acids play a pivotal role in hemagglutination of red blood cells and entry into host cells of JCV and that JCV can enter a wide variety of cell types and localize to the nuclei. The outer shell of the JCV virion comprises the major capsid protein VP1, and a virus-like particle (VLP) consisting of recombinant VP1 made from Escherichia coli exhibit a virion-like structure and physiological functions (cellular attachment and intracytoplasmic trafficking) similar to those of JCV virions. To examine the mechanism of cell attachment of JCV, an overlay assay using a VLP has been developed, revealing that sialoglycoproteins, including alpha1 acid-glycoprotein, fetuin, and transferrin receptor bind with VLP. In addition, VLPs bind to glycolipids, such as lactosylceramide and gangliosides including GM3, GD2, GD3, GD1b, GT1b, and GQ1b, and VLP weakly bind to GD1a. In this section, detailed procedures for the synthesis of VLP from E. coli and VLP overlay assay are described.

Oligosaccharides as receptors for JC virus

JC virus (JCV) belongs to the polyomavirus family of double-stranded DNA viruses and in humans causes a demyelinating disease of the central nervous system, progressive multifocal leukoencephalopathy. Its hemagglutination activity and entry into host cells have been reported to depend on an N-linked glycoprotein containing sialic acid. In order to identify the receptors of JCV, we generated virus-like particles (VLP) consisting of major viral capsid protein VP1. We then developed an indirect VLP overlay assay to detect VLP binding to glycoproteins and a panel of glycolipids. We found that VLP bound to sialoglycoproteins, including alpha1-acid glycoprotein, fetuin, and transferrin receptor, and that this binding depended on alpha2-3-linked sialic acids and N-linked sugar chains. Neoglycoproteins were synthesized by using ovalbumin and conjugation with oligosaccharides containing the terminal alpha2-3- or alpha2-6-linked sialic acid or the branched alpha2-6-linked sialic acid. We show that the neoglycoprotein containing the terminal alpha2-6-linked sialic acid had the highest affinity for VLP, inhibited the hemagglutination activity of VLP and JCV, and inhibited the attachment of VLP to cells. We also demonstrate that VLP bound to specific glycolipids, such as lactosylceramide, and gangliosides, including GM3, GD2, GD3, GD1b, GT1b, and GQ1b, and that VLP bound weakly to GD1a but did not bind to GM1a, GM2, or galactocerebroside. Furthermore, the neoglycoprotein containing the terminal alpha2-6-linked sialic acid and the ganglioside GT1b inhibited JCV infection in the susceptible cell line IMR-32. These results suggest that the oligosaccharides of glycoproteins and glycolipids work as JCV receptors and may be feasible as anti-JCV agents.

Broad distribution of the JC virus receptor contrasts with a marked cellular restriction of virus replication

To investigate the early events of JC virus (JCV) infection, including attachment, penetration, transport to the nuclei, and replication of the virus, we analyzed the susceptibility of 15 different cell lines to infection using a semiquantitative polymerase chain reaction (PCR) assay, in situ hybridization, laser scanning confocal microscopy, and a viral replication assay. The cell lines examined were human permissive and nonpermissive cells as well as cells of monkey and mouse origin. JCV entry into the nuclei of the all cell lines was observed within 10 min after inoculation, demonstrating that the virus receptor is widely distributed among mammalian cells. Inhibition of viral entry by an anti-JCV VP1 antibody and sialidase treatment to remove sialic acid residues, which are considered a candidate for the JCV receptor, suggested that VP1 may interact with the cellular surface sialic acid. In addition, chlorpromazine, a clathrin-dependent pathway inhibitor, significantly suppressed entry of JCV into nuclei. In spite of the broad spectrum of cells susceptible to JCV entry, replication of the virus occurred exclusively in human neuroblastoma cell lines. These results suggest that whereas JCV can enter a wide variety of cell types and localize to the nuclei, cell-specific intranuclear mechanisms are required for virus replication.

Canine leptin: cDNA cloning, expression and activity of recombinant protein

Leptin, the product of the ob gene, is one of the key molecules for the regulation of appetite and whole-body energy balance, and thereby for the pathogenesis of obesity. In an attempt to clarify the roles of leptin in obesity and/or related diseases in companion animals, canine leptin c DNA was cloned by amplifying reverse-transcriptase products of RNA extracted from the adipose tissue of the beagle. A c DNA clone of about 3 kbp contained a 501 bp open reading frame coding a 167-amino acid protein with a 21-amino acid signal peptide. The sequence of a 146-amino acid mature leptin was more than 79 per cent identical to those of other mammals. Northern blot analysis revealed abundant expression of leptin m RNA in adipose tissue, but not in other tissues, in adult beagles. When Chinese hamster ovary cells expressing the rat leptin receptor were stimulated with recombinant canine leptin produced by E. coli, some intracellular signal transduction proteins were phosphorylated, indicating that the recombinant leptin was biologically active. The data reported herein will be helpful for further studies of leptin of the dog in health and disease.

Postnatal changes in Rho and Rho-related proteins in the mouse brain

To provide information on the role of Rho, a GTP-binding protein, in postnatal development of the brain cells, the change in the levels of Rho protein and Rho-related proteins was examined in the brain of mice for two weeks after birth, in parallel with the changes in the activity of marker enzymes for neuronal and glial cells. The activities of acetylcholine esterase and choline acetyltransferase of whole brain homogenate, both of which are neuronal marker enzymes, were progressively increased in an age-dependent manner. The activity of 2',3'-cyclic nucleotide 3'-phosphohydrolase, a glial marker enzyme, increased markedly between one and two weeks after birth. In contrast, the levels of RhoA and RhoB in the membrane fraction were decreased during the postnatal period. The amount of Rho GDP dissociation inhibitor, a regulatory protein for Rho, was unchanged, while those of Rho target proteins, Rock-2 and citron, were gradually increased. Since the inactivation of Rho is known to induce neurite extension and neuronal and glial differentiation in vitro, our results suggest that the Rho signalling pathway plays a regulatory role in the postnatal differentiation of neuronal and glial cells in vivo.

Sandwich enzyme-linked immunosorbent assay of canine leptin

Leptin is the ob gene product secreted from adipocytes in mammals, and thereby its plasma level reflects body fat content. To establish an assay method for leptin in the dog, rabbit anti-canine leptin antibody was obtained using canine recombinant leptin as an antigen. This antibody reacted to canine leptin much stronger than mouse, rat and human leptins. Sandwich enzyme-linked immunosorbent assay (ELISA) using this antibody was developed. The serum leptin levels of 13 healthy dogs were in a range from 1.4 to 5.6 ng/ml with the mean +/- SEM of 3.0 +/- 0.3 ng/ml.

rho-Mediated protein tyrosine phosphorylation in lysophosphatidic-acid-induced tumor-cell invasion

Rat ascites hepatoma cell (MM1) invade a mesothelial cell monolayer in vitro in assay medium containing serum, but not in serum-free medium. Serum could be completely replaced by 1-oleoyl lysophosphatidic acid (LPA) in inducing invasion. LPA-induced invasion was inhibited by genistein, a tyrosine-kinase inhibitor. Protein tyrosine phosphorylation in response to LPA was thus analyzed in order to determine the molecular mechanism of invasion. LPA of invasion-inducible concentrations evoked a transient increase in tyrosine phosphorylation, mainly of 110- to 130-kDa proteins in MM1 cells but not in mesothelial cells. These concentrations of LPA were over 10 times higher (10 to 25 micron) than those necessary to produce a variety of biological actions, such as tyrosine phosphorylation in fibroblasts, neurite retraction and platelet aggregation. Protein tyrosine phosphorylation and invasion by MM1 cells induced by LPA are largely regulated by rho p21, because both were inhibited by Clostridium botulinum C3 exo-enzyme, which is known to specifically inactivate rho p21. Invasion of MCL by MM1 cells induced by serum and that by B16FE7 cells induced by LPA were inhibited by genistein or C3 as well. By immunoprecipitation, we detected p 125 focal adhesion kinase (FAK) as a major protein of 110- to 130-kDa tyrosine phosphorylated in response to LPA. Tyrosine phosphorylation of paxillin by LPA was also detected.

Participation of rhop21 in serum-dependent invasion by rat ascites hepatoma cells

Rat ascites hepatoma cells (MM1 cells) penetrate through a cultured mesothelial cell monolayer (MCL) in the presence of fetal calf serum (FCS), but scarcely do so in its absence. Inactivation of rhop21 of MM1 cells by ADP-ribosyltransferase C3 resulted in the suppression of this serum effect on the penetration, suggesting that the serum effect was mediated by rhop21. To ascertain this assumption MM1 cells were transfected with an activated (Val14) human rhoA cDNA (Neo/RhoA 1-7). The transfectants penetrated MCL extensively even in the absence of FCS and became largely independent of serum for the penetration. These results suggest that serum-induced invasion by MM1 cells is mainly mediated by rhop21.