Biomedical subjects

Koki Taniguchi

Publications and source records attributed to Koki Taniguchi.

At least 19 recordsLinked to original sources

PubMed2006

Evolutionary history and global spread of the emerging g12 human rotaviruses.

G12 rotaviruses were first detected in diarrheic children in the Philippines in 1987, but no further cases were reported until 1998. However, G12 rotaviruses have been detected all over the world in recent years. Here, we report the worldwide variations of G12 rotaviruses to investigate the evolutionary mechanisms by which they managed to spread globally in a short period of time. We sequenced the complete genomes (11 segments) of nine G12 rotaviruses isolated in Bangladesh, Belgium, Thailand, and the Philippines and compared them with the genomes of other rotavirus strains. Our genetic analyses revealed that after introduction of the VP7 gene of the rare G12 genotype into more common local strains through reassortment, a vast genetic diversity was generated and several new variants with distinct gene constellations emerged. These reassortment events most likely took place in Southeast Asian countries and spread to other parts of the world. The acquirement of gene segments from human-adapted rotaviruses might allow G12 to better propagate in humans and hence to develop into an important emerging human pathogen.

Evolution, Molecular↗

PubMed2006

Osteopontin is involved in Th1-mediated immunity against Plasmodium falciparum infection in a holoendemic malaria region in Vietnam.

We examined the role of osteopontin (OPN) in immunity against Plasmodium falciparum infection. We measured the mRNA levels for OPN and several cytokines in RNA preparations extracted from dried blood on filter paper obtained from falciparum malaria patients in Vietnam. Expression of OPN mRNA was detected in 134 of 161 patients. The expression of both interleukin-12 p40 and interferon-gamma mRNAs in the group positive for OPN mRNA was significantly higher than that in the group negative for OPN mRNA. The level of parasitemia in the OPN mRNA-positive group was much lower than that in the negative one. These results suggest that OPN might suppress multiplication of the parasites through T helper 1 cells-mediated immune responses.

Adolescent↗

PubMed2006

Reverse genetics system for introduction of site-specific mutations into the double-stranded RNA genome of infectious rotavirus.

We describe here the successful establishment of a reverse genetics system for rotavirus (RV), a member of the Reoviridae family whose genome consists of 10-12 segmented dsRNA. The system is based on the recombinant vaccinia virus T7 RNA polymerase-driven procedure for supplying artificial viral mRNA in the cytoplasm. With the aid of helper virus (human RV strain KU) infection, intracellularly transcribed full-length VP4 mRNA of simian RV strain SA11 resulted in the rescue of the KU-based transfectant virus carrying the SA11 VP4 RNA segment derived from cDNA. In addition to the rescued transfectant virus with the authentic SA11 VP4 gene, three more infectious RV transfectants, into which silent mutation(s) were introduced to destroy both or one of the two restriction enzyme sites as gene markers in the SA11 VP4 genome, were also rescued with this method. The ability to artificially manipulate the RV genome will greatly increase the understanding of the replication and the pathogenicity of RV and will provide a tool for the design of attenuated vaccine vectors.

Animals↗

PubMed2006

Osteopontin participates in Th1-mediated host resistance against nonlethal malaria parasite Plasmodium chabaudi chabaudi infection in mice.

Osteopontin (OPN) knockout mice (OPN-KO mice) died of Plasmodium chabaudi chabaudi infection, although wild-type (WT) mice had self-limiting infections. OPN was detected in the WT mice at 2 days postinfection. OPN-KO mice produced significantly smaller amounts of interleukin-12 and gamma interferon than WT mice produced. These results suggested that OPN is involved in Th1-mediated immunity against malaria infection.

Animals↗

PubMed2006

Molecular epidemiology of G9 rotaviruses in Taiwan between 2000 and 2002.

Since the mid-1990s, novel G9 rotaviruses have been detected in many countries, suggesting that G9 is a globally important serotype. The molecular epidemiology of G9 rotaviruses in Taiwan from 2000 to 2002 was investigated in this study. G9 rotavirus first appeared in 2000 with 4 cases and constituted 33.8% and 54.8% of the rotavirus-positive samples in 2001 and 2002, respectively. These G9 strains belonged to P[8]G9, subgroup II, and long electropherotype, except one belonged to P[4]G9, subgroup II, and short electropherotype. Nucleotide sequencing and phylogenetic analysis of 52 Taiwanese G9 rotaviruses showed that the VP7 genes shared a high degree of identity to overseas G9 rotaviruses detected after 1993 and that the VP8* portions of the VP4 genes were more closely related to those of local rotaviruses of other G types. The two P[8]G9 strains with high nucleotide identities in the VP7 and the partial VP4 genes, 01TW591 of Taiwan from 2001 and 95H115 of Japan from 1995, varied in four genes, genes 2, 3, 7, and 8, which was revealed by RNA-RNA hybridization. Representative strains for different RNA patterns were also analyzed in the partial VP2 and VP3 genes; the nucleotide identities were high between Taiwanese G9 strains and local G3 or G2 strains. These results suggested that Taiwanese G9 rotaviruses possibly had evolved through reassortment between overseas G9 strains and circulating rotaviruses of other G types.

Antigens, Viral↗

PubMed2006

High-resolution molecular and antigen structure of the VP8* core of a sialic acid-independent human rotavirus strain.

The most intensively studied rotavirus strains initially attach to cells when the "heads" of their protruding spikes bind cell surface sialic acid. Rotavirus strains that cause disease in humans do not bind this ligand. The structure of the sialic acid binding head (the VP8* core) from the simian rotavirus strain RRV has been reported, and neutralization epitopes have been mapped onto its surface. We report here a 1.6-A resolution crystal structure of the equivalent domain from the sialic acid-independent rotavirus strain DS-1, which causes gastroenteritis in humans. Although the RRV and DS-1 VP8* cores differ functionally, they share the same galectin-like fold. Differences between the RRV and DS-1 VP8* cores in the region that corresponds to the RRV sialic acid binding site make it unlikely that DS-1 VP8* binds an alternative carbohydrate ligand in this location. In the crystals, a surface cleft on each DS-1 VP8* core binds N-terminal residues from a neighboring molecule. This cleft may function as a ligand binding site during rotavirus replication. We also report an escape mutant analysis, which allows the mapping of heterotypic neutralizing epitopes recognized by human monoclonal antibodies onto the surface of the VP8* core. The distribution of escape mutations on the DS-1 VP8* core indicates that neutralizing antibodies that recognize VP8* of human rotavirus strains may bind a conformation of the spike that differs from those observed to date.

Antigens, Viral↗

PubMed2005

Higher frequency of premature stop codon mutations at vpu gene of human immunodeficiency virus type 1 CRF01_AE compared with those of other subtypes.

Our previous study demonstrated the anti-apoptosis function of the human immunodeficiency virus type 1 (HIV-1) vpu gene product in normal CD4+ T lymphocytes. In this study, using sequences obtained from the HIV sequence database, we compared vpu sequences from 184 preparations of various subtypes of HIV-1 from diverse geographical regions. Our analysis revealed that CRF01_AE isolates had premature stop codon mutations at the vpu gene at a much higher rate (36%) than other subtypes (0-9%). The premature stop codon mutations in vpu existed mostly at two amino acid residues: the methionine initiation codon and the boundary between the transmembrane (TM) and cytoplasmic domains. The mutations at the latter site were more often detected in CRF01_AE. The higher mutation rates at vpu in CRF01_AE were confirmed by sequence comparison of polymerase chain reaction products newly obtained directly from the DNA extracted from peripheral blood mononuclear cells (PBMCs), but not from the RNA from the plasma, in CRF01_AE- and subtype B-infected individuals. This finding may indicate the possibility that the more abundant population of HIV-1 CRF01_AE is able to induce apoptosis in CD4+ T lymphocytes than the populations of other subtypes.

Codon↗

PubMed2005

Expression and antigenicity of virus-like particles of norovirus and their application for detection of noroviruses in stool samples.

Human noroviruses (NoVs), members of the genus Norovirus in the family Caliciviridae, are the leading agents of nonbacterial acute gastroenteritis worldwide. Human NoVs are currently divided into at least two genogroups, genogroup I (GI) and genogroup II (GII), each of which contains at least 14 and 17 genotypes. To explore the genetic and antigenic relationship among NoVs, we expressed the capsid protein of four genetically distinct NoVs, the GI/3 Kashiwa645 virus, the GII/3 Sanbu809 virus, the GII/5 Ichikawa754 virus, and the GII/7 Osaka10-25 virus in baculovirus expression system. An antigen enzyme-linked immunosorbent assay (ELISA) with hyperimmune serum against the four recombinant capsid proteins and characterized previously three capsid proteins derived from GI/1, GI/4, and GII/12 was developed to detect the NoVs antigen in stools. The antigen ELISA was highly specific to the homotypic strains, allowing assignment of a strain to a Norovirus genetic cluster within a genogroup.

Animals↗

PubMed2005

Complete nucleotide sequences of two RNA segments of human picobirnavirus.

Picobirnaviruses are unclassified, non-enveloped, spherical, small viruses with a genome comprising two double-stranded RNA segments. Only incomplete sequence data on picobirnaviruses are available so far. By cloning involving single primer amplification, full-length cDNAs were prepared corresponding to RNA segments 1 and 2 of a picobirnavirus (strain Hy005102) isolated from a stool specimen from an infant with acute non-bacterial gastroenteritis in Thailand, and the complete nucleotide sequences were determined. RNA segments 1 and 2 are 2,525 and 1,745 base pairs in length, respectively. RNA segment 1 encodes two open reading frames (ORFs) of 224 and 552 amino acids, and RNA segment 2 codes for a single ORF of 534 amino acids. On comparison with a part of the nucleotide sequences of the RNA segment, 2 of the other published picobirnavirus strains, the Thai strain was found to be related most closely to one of the US strains.

Base Sequence↗

PubMed2005

Detection and characterization of human group C rotaviruses in Bangladesh.

Group C rotaviruses were detected by reverse transcription-PCR in 14 (2.3%) of 611 group A rotavirus-negative stool specimens from the patients admitted to the International Centre for Diarrhoeal Disease Research, Bangladesh hospital, Dhaka, Bangladesh, during July to December 2003. The low rate of detection suggested that infection with group C rotaviruses was an uncommon cause of hospitalization due to gastroenteritis. In addition, coinfections with pathogenic enteric bacteria were frequently observed in group C rotavirus-infected patients. Nucleotide sequence comparison of the VP4, VP6, and VP7 genes revealed that the Bangladeshi group C rotaviruses were most similar to Nigerian group C rotavirus strains. Phylogenetic analysis suggested that all human group C rotaviruses, including the strains isolated in our study, clustered in a monophyletic branch, which was distantly related to the branch comprised of animal group C rotaviruses.

Adolescent↗

PubMed2005

The 5'-terminal region of the Aichi virus genome encodes cis-acting replication elements required for positive- and negative-strand RNA synthesis.

Aichi virus is a member of the family Picornaviridae. It has already been shown that three stem-loop structures (SL-A, SL-B, and SL-C, from the 5' end) formed at the 5' end of the genome are critical elements for viral RNA replication. In this study, we further characterized the 5'-terminal cis-acting replication elements. We found that an additional structural element, a pseudoknot structure, is formed through base-pairing interaction between the loop segment of SL-B (nucleotides [nt] 57 to 60) and a sequence downstream of SL-C (nt 112 to 115) and showed that the formation of this pseudoknot is critical for viral RNA replication. Mapping of the 5'-terminal sequence of the Aichi virus genome required for RNA replication using a series of Aichi virus-encephalomyocarditis virus chimera replicons indicated that the 5'-end 115 nucleotides including the pseudoknot structure are the minimum requirement for RNA replication. Using the cell-free translation-replication system, we examined the abilities of viral RNAs with a lethal mutation in the 5'-terminal structural elements to synthesize negative- and positive-strand RNAs. The results showed that the formation of three stem-loops and the pseudoknot structure at the 5' end of the genome is required for negative-strand RNA synthesis. In addition, specific nucleotide sequences in the stem of SL-A or its complementary sequences at the 3' end of the negative-strand were shown to be critical for the initiation of positive-strand RNA synthesis but not for that of negative-strand synthesis. Thus, the 5' end of the Aichi virus genome encodes elements important for not only negative-strand synthesis but also positive-strand synthesis.

Animals↗

PubMed2005

[Picobirnavirus].

Picobirnavirus is named after the small birnavirus which contains two double-stranded RNA segments as a genome. However, their properties are quite different to each other. Although the virus has been detected mainly from the stools of gastroenteritis patients and several mammals and birds, the pathogenicity of the virus has not been established. Characterizations of the virus are hampered due to the lack in the system for multiplication of the virus in cultured cells or experimental animals. Recently, complete nucleotide sequences of two RNA segments of a human picobirnavirus detected in Thailand were determined.

Animals↗

PubMed2004

Genetic analysis of group B human rotaviruses detected in Bangladesh in 2000 and 2001.

Group B rotaviruses detected in Bangladesh in 2000 and 2001 were analyzed genetically to clarify relatedness to human group B rotaviruses reported previously in China and India, and to animal group B rotaviruses. VP7 gene sequences of the Bangladeshi group B rotaviruses (Bang373, Bang544, Bang334, and Bang402) were almost identical to each other and also showed high sequence identity to the Indian strain CAL-1 (98%) and Chinese strain adult diarrhea rotavirus (ADRV) (92%), while identities to bovine and murine viruses were considerably low (60-63%). Other genes of Bang373 and Bang544 encoding VP2, VP4, VP6, and NSP1 through NSP5 also showed much higher sequence identities to those of CAL-1 (97.7-99.4%) than to those of ADRV (89.9-93.9%). Characterization of nucleotide substitutions among Bang373, CAL-1, and ADRV suggested that all the gene segments might have evolved neutrally at similar mutation rates, while some of the gene segments (e.g., VP2 gene) were suggested to be more conserved than others. In conclusion, group B rotaviruses detected in Bangladesh represented by Bang373 and the Indian virus CAL-1 were considered as virtually identical viruses which are distinct genetically from ADRV, and it was suggested that Bang373 (CAL-1)-like group B rotavirus (Bengali strains) might be distributed primarily in an area around the Bay of Bengal.

Adult↗

PubMed2004

Characterization of human rotavirus strains with G12 and P[9] detected in Japan.

Two G12 human rotavirus strains, CP727 and CP1030, were isolated from the respective diarrheic stools of an infant and an adult in Japan. VP7 gene sequences of strains CP727 and CP1030 showed high identity with that of the G12 prototype strain L26, and with those of G12 strains reported recently from Thailand, the United States, and India. VP4 gene sequences of strains CP727 and CP1030 showed the highest identity with those of P[9] rotaviruses. In Northern blot hybridization, strains CP727 and CP1030 were found to be closely related to strain AU-1 (G3P[9]); nine RNA segments hybridized to each other. Moreover, all segments each of the two Japanese G12 strains hybridized to those of the Thai G12 strain T152. These results suggest that Japanese G12 strains detected in this study are reassortants between a L26-like strain and a strain in the AU-1 genogroup. A similar reassortant was found in the Thai G12 strain T152.

Adult↗

PubMed2004

Isolation and characterisation of poliovirus mutants resistant to heating at 50 degrees Celsius for 30 min.

Poliovirus is heat-labile; on heating at 50 degrees Celsius for 30 min its infectivity decreases drastically and its antigenicity reverts from N to H. However, mutants resistant to heating at 50 degrees Celsius for 30 min from the Sabin 1 and 2 viruses were isolated by repeating the process of incubation of the virus stock at 50 degrees Celsius for 30 min and multiplication of the remaining virus in a cell culture. The isolated mutants were stable genetically, and maintained the rct and d markers of the parent virus. On electron microscopical examination, the mutants were observed to retain the intact morphology after being heated at 50 degrees Celsius for 30 min, while the parent virus was converted to empty particles devoid of RNA under the same conditions. On determination of the nucleotide sequence of the P1 region, a single nucleotide sequence substitution was detected at nucleotide no. 2741, resulting in an amino acid change from valine to alanine at the 87th position of VP1. This amino acid might be associated with the heat-resistance of the mutants. Furthermore, it was found that the thermostable mutants obtained in this study, which are resistant to "high" temperature (50 degrees Celsius) for a short time (30 min), were not stable against heating at the ambient temperature (37 degrees Celsius) for a long time (5 or 7 days). This suggests that the inactivation at high temperature for a short time and that at ambient temperature for a long time involve different mechanisms.

Amino Acid Substitution↗

PubMed2004

Isolation of human monoclonal antibodies that neutralize human rotavirus.

A human antibody library constructed by utilizing a phage display system was used for the isolation of human antibodies with neutralizing activity specific for human rotavirus. In the library, the Fab form of an antibody fused to truncated cp3 is expressed on the phage surface. Purified virions of strain KU (G1 serotype and P[8] genotype) were used as antigen. Twelve different clones were isolated. Based on their amino acid sequences, they were classified into three groups. Three representative clones-1-2H, 2-3E, and 2-11G-were characterized. Enzyme-linked immunosorbent assay with virus-like particles (VLP-VP2/6 and VLP-VP2/6/7) and recombinant VP4 protein produced from baculovirus recombinants indicated that 1-2H and 2-3E bind to VP4 and that 2-11G binds to VP7. The neutralization epitope recognized by each of the three human antibodies might be human specific, since all of the antigenic mutants resistant to mouse monoclonal neutralizing antibodies previously prepared were neutralized by the human antibodies obtained here. After conversion from the Fab form of an antibody into immunoglobulin G1, the neutralizing activities of these three clones toward various human rotavirus strains were examined. The 1-2H antibody exhibited neutralizing activity toward human rotaviruses with either the P[4] or P[8] genotype. Similarly, the 2-3E antibody showed cross-reactivity against HRVs with the P[6], as well as the P[8] genotype. In contrast, the 2-11G antibody neutralized only human rotaviruses with the G1 serotype. The concentration of antibodies required for 50% neutralization ranged from 0.8 to 20 micro g/ml.

Amino Acid Sequence↗

PubMed2003

Functional analysis of the stem-loop structures at the 5' end of the Aichi virus genome.

Aichi virus is a member of the family Picornaviridae. Computer-assisted secondary structure prediction suggested the formation of three stem-loop structures (SL-A, SL-B, and SL-C from the 5' end) within the 5'-end 120 nucleotides of the genome. We have already shown that the most 5'-end stem-loop, SL-A, is critical for viral RNA replication. Here, using an infectious cDNA clone and a replicon harboring a luciferase gene, we revealed that formation of SL-B and SL-C on the positive strand is essential for viral RNA replication. In addition, the specific nucleotide sequence of the loop segment of SL-B was also shown to be critical for viral RNA replication. Mutations of the upper and lower stems of SL-C that do not disrupt the base-pairings hardly affected RNA replication, but decreased the yields of viable viruses significantly compared with for the wild-type. This suggests that SL-C plays a role at some step besides RNA replication during virus infection.

5' Untranslated Regions↗

PubMed2003

Utility of the dried blood on filter paper as a source of cytokine mRNA for the analysis of immunoreactions in Plasmodium yoelii infection.

We examined the utility of dried blood on filter paper for the source of cytokine messenger RNA (mRNA). Total RNA was isolated from the dried blood of mice infected with Plasmodium yoelii, and cDNA was amplified by reverse transcription-polymerase chain reaction (RT-PCR). As a reference, we extracted total RNA from peripheral blood collected at the same time as the preparation for dried blood. There was no difference in cytokine mRNA expression between the two sources; the dried blood on filter paper and the peripheral blood. Th1 cells, Th2 cells, and monocytes/macrophages derived cytokine mRNAs in the dried blood from infected mice were detected, and the increase of some of the cytokines mRNAs after infection was also observed. These results suggested that the dried blood on filter paper is satisfactory RNA source for immunological examination in field-based studies.

Animals↗