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S Urasawa

Publications and source records attributed to S Urasawa.

At least 37 records · Page 2Linked to original sources
PubMed1998

Survey of human group C rotaviruses in Japan during the winter of 1992 to 1993.

Fecal specimens from patients with acute diarrhea were collected from 10 prefectures in Japan over a 6-month period (November 1992 to April 1993), and the specimens that were negative for human group A rotaviruses were screened for the presence of human group C rotaviruses (CHRVs) by the reverse passive hemagglutination test. Of 784 specimens examined, 53 samples (6.8%) that were collected in 7 of 10 prefectures were positive for CHRV, indicating that CHRVs are widely distributed across Japan. Most of the CHRV isolates were detected in March and April, and CHRVs mainly prevailed in children ages 3 to 8 years. The genome electropherotypes of eight strains isolated in five individual prefectures were surprisingly similar to each other and were different from those of CHRV strains isolated to date. The outer capsid glycoprotein (VP7) gene homologies of the isolates retrieved in 1993 were subsequently analyzed by the dot blot hybridization method. As a result, the VP7 genes of the isolates revealed very high levels of homology not only with each other but also with the VP7 gene of the OK118 strain isolated in 1988. These results suggest that a large-scale outbreak of CHRV occurred during the winter of 1992 and 1993 in Japan.

Adolescent↗
PubMed1998

Detection and characterization of novel rotavirus strains in the United States.

We recently established a rotavirus strain surveillance system in the United States to monitor the prevalent G serotypes before and after the anticipated implementation of a vaccination program against rotavirus and to identify the emergence of uncommon strains. In this study, we examined 348 rotavirus strains obtained in 1996 to 1997 from children with diarrhea in 10 U.S. cities. Strains were characterized for P and G types, subgroups, and electropherotypes by using a combination of monoclonal antibody immunoassay, reverse transcription-PCR, and hybridization. The four strains most commonly found worldwide comprised 83% of the isolates (P[8]G1, 66.4%; P[4]G2, 8.3%; P[8]G3, 6.9%; P[8]G4, 1.4%), but 9.2% were unusual strains (P[6]G9, 5.5%; P[8]G9, 1.7%; P[6]G1, 1.4%; and P[4]G1 and P[8]G2, 0. 3% each). Strains not typeable for P or G type accounted for 5.5% of the total, while 2.3% of the strains had more than one G type (mixed infections). All P[6]G9 strains tested had short electropherotypes and subgroup I specificity and were detected in 4 of 10 cities, while P[8]G9 strains had long electropherotypes and subgroup II VP6 antigens. Both sequence analysis of the VP7 open reading frame (about 94 to 95% amino acid identity with the VP7 gene of G9 prototype strain WI61) and binding to a G9-specific monoclonal antibody strongly suggest that U.S. G9 strains belong to serotype G9. The high detection rates of unusual rotaviruses with G9 (7.2%) or P[6] (6.9%) specificity in multiple U.S. cities suggest the emergence of new strains or inadequate diagnosis in the past. The epidemiologic importance of these strains remains to be determined.

Antibodies, Monoclonal↗
PubMed1996

Sequence analysis of normal and rearranged NSP5 genes from human rotavirus strains isolated in nature: implications for the occurrence of the rearrangement at the step of plus strand synthesis.

We determined the nucleotide sequences of normal and rearranged NSP5 genes from the human rotavirus strains (Mc323 and Mc345, respectively) which had previously been isolated from Thai infants with diarrhea in the same epidemic season. While the two strains shared G serotype 9 specificity and subgroup I specificity and they showed a high level of overall genomic relatedness to each other, they exhibited different RNA profiles; a long pattern for Mc323 and a super-short pattern for Mc345. Their NSP5 sequences were more closely related to those of porcine rotaviruses than to those of human rotaviruses. Mc345 NSP5 gene was shown to have concatemerization. In a head-to-tail orientation resulting in its length being 1182 bp, as compared with the Mc323 NSP5 sequence which was 664 bp in length. Sequence analysis suggested that the rearrangement found in the strain Mc345 occurred at the step of plus strand synthesis.

Base Sequence↗
PubMed1996

Structure and function of rotavirus NSP1.

Studies on the structure and function of the nonstructural proteins (NSP1-NSP5) of rotaviruses are important for dissection of the morphogenesis and replication processes of rotavirus. Above all, NSP1, the product of gene 5, has several interesting features, such as extreme sequence diversity, a highly conserved cysteine-rich region, RNA-binding activity, accumulation on the cytoskeleton, and non-random segregation in reassortment. Recently, comparable NSP1 sequence analysis has been performed on a number of rotavirus strains from various species. Furthermore, characterization of mutants with rearranged NSP1 genes has helped to elucidate the structure-function interaction of NSP1. We isolated and characterized two interesting mutants which have a large deletion including the cysteine-rich region or a nonsense codon at the early portion in the open reading frame (ORF) of the NSP1 gene. In this report, we summarize the structure and function of NSP1.

Amino Acid Sequence↗
PubMed1996

G (VP7) serotype-dependent preferential VP7 gene selection detected in the genetic background of simian rotavirus SA11.

We previously found the preferential selection of VP7 gene from a parent rotavirus strain SA11 with G serotype 3 (G3) in the sequential passages after mixed infection of simian rotavirus SA11 and SA11-human rotavirus single-VP7 gene-substitution reassortants with G1, G2, or G4 specificity. However, it has not been known whether or not VP7 genes derived from other strains with G3 specificity (G3-VP7 gene) are preferentially selected in the genetic background of SA11. To address this question, mixed infections followed by multiple passages were performed with a reassortant SA11-L2/KU-R1 (SKR1) (which possesses VP7 gene derived from G1 human rotavirus KU and other 10 genes of SA11 origin) and one of the five G3-rotaviruses, RRV, K9, YO, AK35, and S3. After the 10th passage, selection rates of SA11-L2/KU-R1 gene 9 (G1-VP7 gene) and gene 5 (NSP1 gene) reduced considerably (0 to 20.4%) in the clones obtained from all the coinfection experiments, while all or some of other segments were preferentially selected from SKR1 depending on the pairs of coinfection. When viral growth kinetics was examined, SKR1 exhibited better growth and reached a higher titer than any G3 viruses. Although the generated reassortants with VP7 gene and NSP1 gene derived from G3 viruses showed almost similar growth kinetics to that of SKR1 during the first 20 h of replication, the titers of these reassortants were higher than that of SKR1 after 36 h postinfection. The results obtained in this study suggested that G3-VP7 gene is functionally more adapted to the genetic background of SA11.

Animals↗
PubMed1996

Outbreaks of nosocomial rotavirus gastro-enteritis in a paediatric ward.

UNLABELLED: Faecal samples were collected from patients with gastro-enteritis during two winter seasons on a paediatric ward. Three outbreaks of nosocomial rotavirus gastro-enteritis were identified by latex agglutination and the virus strains were characterized by polyacrylamide gel electrophoresis of the genome nucleic acid and by subgrouping and serotyping enzyme-linked immunosorbent assays (ELISA). One outbreak was caused by serotype 1 rotavirus, one by serotype 2 and the remaining outbreak was caused by a mixture of serotypes 1 and 4. Identical electrophoretic patterns of the rotavirus genome in each outbreak combined with the ELISA results indicate that these three outbreaks were hospital-acquired cases. The index cases in the three outbreaks were community-acquired and one of two index cases in the second outbreak was hospital-acquired. On each occasion, susceptible roommates were easily infected from the index cases and then cross-infection occurred in the paediatric ward. Possible vehicles were the medical staff, especially doctors, parents of infected patients and infected patients who were moved to other rooms. One patient who had been treated with a series of antitumour therapies excreted rotaviruses in faeces for a long time period and probably played a role as a source of the outbreak. Moreover, some patients still excreted rotaviruses in their normal stool 1 week after recovery from gastro-enteritis. These findings indicate that continual examination of stool samples for rotaviruses until they are negative may be important to prevent the spread of rotavirus infection. CONCLUSION: Nucleic acid analysis and serotyping ELISA are useful tools for analyzing nosocomial rotavirus gastro-enteritis and important to prevent the spread of rotavirus infection in institutions.

Child↗
PubMed1996

Selection of rotavirus VP7 gene in the genetic background of simian rotavirus SA11: implications for rotavirus reassortant vaccine development.

We previously reported that the VP7 gene from simian rotavirus SA11 with G-serotype 3(G3-VP7 gene) was preferentially selected in the genetic background of SA11 compared with the G1- or G2-VP7 gene. In the present study, selection of the G4-VP7 gene in competition with G1-, G2- or G3-VP7 gene in the SA11 background was analyzed through mixed infection experiments using SA11 and SA11-human rotavirus single-VP7 gene-substitution reassortants with G-serotypes 1, 2, and 4 (G1-, G2- and G4-reassortant). In virus clones from coinfection of SA11 and G4-reassortant, the frequency of G4 virus decreased to 7% at the 3rd passage and the G4 virus disappeared at the 10th passage, whereas the majority of the clones possessed G3 specificity. However, the predominance of either of the viruses coinfected was not observed in the mixed infection with G4-reassortant and G1- or G2-reassortant. Although growth kinetics of SA11 and G4-reassortant was similar, G4-reassortant showed significantly smaller plaque size than SA11, G1- and G2-reassortant did. These results indicated that the G3-VP7 gene from SA11 might be preferentially selected in the SA11 genetic background compared with the G4-VP7 gene, and suggested that the introduction of a single G4-VP7 gene may affect growth characteristics of recipient virus SA11. These results together with our previous findings suggested the significance of genetic compatibility between recipient viral genes and foreign VP7 gene in the development of multivalent reassortant rotavirus vaccines.

Animals↗
PubMed1996

Effect of MDP-Lys(L18) as a mucosal immunoadjuvant on protection of mucosal infections by Sendai virus and rotavirus.

To examine the effect of MDP-Lys(L18), a derivative of muramyl dipeptide (MDP), as a mucosal immunoadjuvant, we investigated its activity to augment host resistance against mucosal infections by Sendai virus and rotavirus in mice. In an experimental infection model using suckling mice (10-day-old) inoculated perorally (p.o.) with 1.5 x 10(6) p.f.u. mouse-1 of rotavirus strain SA11, intrarectal (i.r.) as well as p.o. administration of MDP-Lys(L18) (50 micrograms mouse-1) prior to virus infection markedly reduced rotavirus-induced diarrhea. Furthermore, when MDP-Lys(L18) was administered p.o. (1 mg mouse-1), i.r. (300 micrograms mouse-1) or intranasally (i.n., 100 micrograms mouse-1) various days before Sendai virus infection (2.6 x 10(4) HAD mouse-1), all the mucosal administration of MDP-Lys(L18) significantly protected a lethal infection of Sendai virus, showing a dose-dependent manner. However, the efficacy of MDP-Lys(L18) to induce the prophylactic activity against the viruses somewhat varied according to the administration route and timing. In time course analysis of virus isolation in vivo, the mice administered with MDP-Lys(L18) exhibited a significant reduction of both viruses in the lungs for Sendai virus and in the bowels for rotavirus. These results suggest that MDP-Lys(L18) is a potent mucosal immunoadjuvant to enhance nonspecific host resistance against two mucosal infectious viruses, Sendai virus and rotavirus.

Acetylmuramyl-Alanyl-Isoglutamine↗
PubMed1996

The distribution of G and P types within isolates of bovine rotavirus in Japan.

Various combinations of G type and P type were observed in 76 bovine rotavirus (BRV) strains isolated from 235 diarrheal calves in three prefectures of Japan in 1992-1994. The most prevalent combination was G6:P5 (46/76, 60.5%), followed by G10:P11 (13/76, 17.1%), G6:P11 (7/76, 9.2%) and G10:P5 (5/76, 6.6%). No G6:P1 strain of BRV was recognized from the isolates in the present study, though this type of BRV is well known as a suitable vaccine strain against BRV infection.

Animals↗
PubMed1996

Genomic diversity of mec regulator genes in methicillin-resistant Staphylococcus aureus and Staphylococcus epidermidis.

Low-affinity penicillin-binding protein PBP-2a encoded by mecA is closely related to methicillin resistance in staphylococci, and expression of PBP-2a is controlled by regulator elements encoded by mecR1 and mecI which are located adjacent to mecA on the chromosome. Deletion or mutation which occurred in mec regulator gene is considered to be associated with constitutive production of PBP-2a. The distribution of the mec regulator genes in 176 strains of Staphylococcus aureus and 33 strains of S. epidermidis isolated from a single hospital was studied by polymerase chain reaction amplification. Most clinical isolates of methicillin-resistant S. aureus (MRSA) (94.3%) and S. epidermidis (MRSE) (83.9%) possessed both mecI and mecR1 genes (type I), whereas no mec regulator genes were detected in mecA-negative isolates. In contrast, 7 MRSA and 5 MRSE isolates were found to have incomplete regulator genes, and they were classified into three groups; strains which lacked only mecI gene (type II), strains which lacked mecI and 3'-end of mecR1 gene (type III), and strains which lacked both regulator genes (type IV). Analysis of mecI gene from all the strains having mecI by restriction fragment length polymorphism after Mse I digestion indicated that three MRSA strains possessed one of the known point mutations identified previously. These findings indicated the predominance of a single type of MRSA possessing both mecI and mecR1 in the study period and also suggested a high genomic diversity in mec regulator region of staphylococci.

Cross Infection↗
PubMed1996

Serological and genomic characterization of porcine rotaviruses in Thailand: detection of a G10 porcine rotavirus.

A total of 557 fecal specimens collected from piglets with diarrhea in Thailand were examined for rotavirus RNA by polyacrylamide gel electrophoresis. Twenty-three, one, and two samples were positive for group A, group B, and group C rotaviruses, respectively. Two samples exhibited two segments found in picobirnavirus RNA. RNA electropherotyping of 23 group A rotaviruses showed that they were classified into five patterns. By serotyping by enzyme-linked immunosorbent assay and PCR, viruses in 3 and 14 specimens were found to be serotype G3 and serotype G10, respectively. For one specimen, containing a serotype G10 virus (strain P343), virus was isolated in MA-104 cells, and the nucleotide sequences of the VP7 and VP4 genes were determined. Comparative sequence analysis and cross-neutralization tests showed that strain P343 has B223-like G10 and UK-like P7 serotype (or VP4 genotype 5) specificities. Rotaviruses having such antigenic specificities have not been detected in piglets. Thus, the interspecies transmission of rotaviruses between cows and pigs was suggested.

Amino Acid Sequence↗
PubMed1996

Nondefective rotavirus mutants with an NSP1 gene which has a deletion of 500 nucleotides, including a cysteine-rich zinc finger motif-encoding region (nucleotides 156 to 248), or which has a nonsense codon at nucleotides 153-155.

We isolated two nondefective bovine rotavirus mutants (A5-10 and A5-16 clones) which have nonsense mutations in the early portion of the open reading frame of the NSP1 gene. In the NSP1 gene (1,587 bases long) of A5-10, a nonsense codon is present at nucleotides 153 to 155 just upstream of the coding region (nucleotides 156 to 230) of a cysteine-rich Zn finger motif. A5-16 gene 5 (1,087 bases long) was found to have a large deletion of 500 bases corresponding to nucleotides 142 to 641 of a parent A5-10 NSP1 gene and to have a nonsense codon at nucleotides 183 to 185, which resulted from the deletion. Expression of gene 5-specific NSP1 could not be detected in MA-104 cells infected with the A5-10 or A5-16 clone or in an in vitro translation system using the plasmids with gene 5 cDNA from A5-10 or A5-16. Nevertheless, both A5-10 and A5-16 replicated well in cultured cells, although the plaque size of A5-16 was extremely small.

Amino Acid Sequence↗
PubMed1996

Superantigen as a modifying factor in HIV infection.

Superantigen is characterized as a potent stimulator of T cells through its unique interaction with major histocompatibility complex class II molecule and the V beta chain of T cell receptor. It has been reported that symptoms in several infectious diseases are associated with superantigen activity, i.e., abnormal reaction due to excess activation of T cells. However, the implications of superantigen in human immunodeficiency virus (HIV) infections have not been well elucidated. In this article, we review the possible mechanisms by which superantigens may modify HIV infections. In conclusion, superantigen is considered to be a factor that aggravates the immunodeficient state in HIV-infected patients through activation of HIV expression in infected T cells and monocytes, and facilitation of CD4 T cell depletion. Since exogenous superantigen is most likely to be provided by microbial infections such as Staphylococcus aureus infection, countermeasures against these complicating infections may be important to avert the detrimental impact of superantigens.

CD4 Antigens↗
PubMed1995

Preferential selection of VP7 gene from a parent rotavirus strain (SA11) in sequential passages after mixed infection with SA11 and SA11-human rotavirus single-VP7 gene-substitution reassortants.

We studied the competitive growth among SA11-L2(G3) and its single-human VP7 gene-substitution reassortants SA11-L2/KU-R1(G1) and SA11-L2/DS1-R1(G2), which have the genetic background of SA11-L2, during sequential passages after mixed infection. When the same infectious units (m.o.i. of 5 p.f.u./cell) of SA11-L2 and a reassortant SA11-L2/KU-R1 were inoculated onto and passaged in MA104 cells, 88% of the virus clones isolated from the culture fluid at the 3rd passage belonged to G3, and all the clones from the 10th passage had G3 specificity. Even when SA11-L2/KU-R1 with titer 10 times higher than that of SA11-L2 was used in the coinfection, the predominance of clones with G3-VP7 was observed. Although G2 clones slightly surpassed G1 clones in number in the mixed culture of SA11-L2/KU-R1 and SA11-L2/DS1-R1, G3 clones predominated in the virus progeny from a mixed culture infected with the same titers of SA11-L2, SA11-L2/KU-R1, and SA11-L2/DS1-R1. However, no significant difference in viral growth was detected among SA11-L2 and the two reassortants.

Antigens, Viral↗
PubMed1995

Analysis of methicillin-resistant and methicillin-susceptible Staphylococcus aureus by a molecular typing method based on coagulase gene polymorphisms.

A molecular typing method for Staphylococcus aureus based on coagulase gene polymorphisms (coagulase gene typing) was evaluated by examining a total of 240 isolates which comprised 210 methicillin-resistant S. aureus (MRSA) and 30 methicillin-susceptible S. aureus (MSSA) collected from a single hospital. By AluI restriction enzyme digestion of the PCR-amplified 3'-end region of the coagulase gene including 81-bp repeated units, the MRSA and MSSA isolates examined were divided into 6 and 12 restriction fragment length polymorphism (RFLP) patterns, respectively, whereas five patterns were commonly detected in MRSA and MSSA. MRSA isolates that showed a particular RFLP pattern were considered to be predominant in the hospital. Coagulase typing with type-specific antisera was also performed for all S. aureus isolates for comparison. Coagulase types II and VII were most frequently detected and included isolates with four and five different AluI RFLP patterns, respectively, whereas each of the other coagulase types corresponded to a single RFLP pattern. These results indicated that RFLP typing was more discriminatory than serological typing, for typing S. aureus and demonstrated its utility in epidemiologic investigation of S. aureus infection in hospitals.

Bacterial Typing Techniques↗
PubMed1995

Persistence of a single electropherotype and serotype (G6P5) of bovine rotavirus in calves on a closed dairy farm from 1990 to 1993.

A virologic survey was conducted on calves with diarrhea associated with bovine rotavirus (BRV) on a closed dairy farm. The BRV was detected from 32 of 219 (14.6%) fecal specimens repeatedly collected from 56 calves born during the years 1992-1993, regardless of whether they had diarrhea. Most of the 32 strains were isolated from fecal specimens obtained from 2- to 6-week-old calves. After electrophoresis of double-stranded viral RNA from the 32 strains, genomic RNA migration patterns were similar to those of the predominant BRV strains isolated at the same farm during the years 1990-1991. All representative strains were identified as G serotype 6 (G6) and P type 5 (P5) by results of the virus-neutralization test and polymerase chain reaction procedure. Thus, BRV had no change in genomic RNA electropherotypes and serologic antigenicities in a closed dairy herd over a period of several years.

Animals↗