Biomedical subjects
Publications and source records attributed to O Nakagomi.
In this paper, evidence for intragenic recombination in the VP7 gene between rotavirus strains bearing different serotypes is demonstrated for the first time. Intragenic recombination may be one of the escaping mechanisms from the host immune system for rotavirus. This process involves exchanging antigenic regions, thus questioning the use of multivalent vaccines for the prevention of rotavirus infection.
Insight into the origin of human rotaviruses carrying the AU-1 VP4 allele was gained by examining their genomic RNA constellation using RNA-RNA hybridization and by sequencing the VP8* portion (nucleotides 1-750) of their gene 4. AU-1 like viruses isolated in Israel from children attending outpatient clinics were classified into three sub-genogroups based on RNA-RNA hybridization analysis: Subgenogroup 1 consists of two strains (Ro-5829 and Ro-5960) which belong to the AU-1 genogroup, since all their 11 segments hybridized to AU-1 segments. Subgenogroup 2 consists of one reassortant virus (Ro-5193) of which seven RNA segments hybridized to AU-1 segments and the remaining four segments hybridized to NCDV (bovine rotavirus). Subgenogroup 3 consists of four reassortant viruses (Ro-6460, Ro-6584, Ro-6784 and Ro-7044) which had a common genome constellation: only four of their RNA segments hybridized to AU-1 and the other seven segments hybridized to NCDV segments. Sequence analysis of the VP8* gene also revealed a three level pattern of homology with the AU-1 prototype and the local AU-1 like strains which was consistent with the overall genomic (RNA-RNA) constellation: Subgenogroup 1 had 98-98.1% homology with the AU-1 prototype; Subgenogroup 2 had 96.8% homology with the AU-1 prototype and 95.6-96.7% homology with Subgenogroup 1; Subgenogroup 3 had 95.3-95.6% homology with the prototype AU-1 and 93.4-94.3% homology with Subgenogroup 1. Possible evolutionary pathways are discussed.
Bovine rotavirus strain 678 is the first G8 strain of bovine origin but the literature is confusing as to its P type. In this study, two-way cross neutralization between 678 and 0510, a prototype G6P7[5] virus, was shown by plaque-reduction neutralization assays, establishing the P type of 678 as being P7[5]. The P7[5] specificity of 678 VP4 was reinforced by the finding that the VP8* portion of 678 VP4 had the highest amino acid identity with those of P7[5] bovine rotaviruses. Apparent contradiction with previous serological studies relates to intricacy of antigenicity and immunogenicity of UK VP4 in reassortants.
The nonstructural glycoprotein NSP4 of group C human rotavirus strain Ehime 9301 was determined to be 150 amino acids in length and 96% identical with the NSP4 of another group C human rotavirus strain Bristol. Both NSP4 sequences were virtually unrelated to group A rotavirus NSP4s. However, the structural features of group A and group C rotavirus NSP4s were similar with hydrophobic domains being in the amino terminus and a coiled coil domain after the membrane-spanning domain, although group C rotavirus NSP4 lacked one amino-terminal hydrophobic domain.
VP7 genes of rotavirus (RV) 993/83 isolated from a German calf with diarrhea and of RV PO-13 isolated from a Japanese pigeon were sequenced. Alignment of the deduced VP7 amino acid sequence showed 98.8% sequence identity, while only 70% and 84% identity was seen with VP7 from chicken RV Ch-2 and turkey RV Ty-1, respectively. Over the antigenic regions A, B, and C mammalian RV 993/83 showed more aa identity with mammalian G3 RVs than with chicken RV Ch-2, which could explain the strong one-way cross-neutralization observed between RV 993/83 and G3 RVs. Despite marked VP7 sequence diversity avian RVs could not be differentiated into distinct G types.
Comparison of nonstructural glycoprotein NSP4 gene sequences from 22 rotavirus strains originating from six host species and of 14 different combinations of G and P types revealed the presence of three distinct NSP4 alleles, represented by strains Wa, KUN and AU-1. Genetic distances between any of these alleles (18.0%) were significantly greater than those within each allele (5.5%) and phylogenetic analysis suggested that divergence into three distinct alleles had occurred at about the same time during evolution. While amino acid variation among strains was minimal in the amino-terminal two-thirds of the protein (aa 1-130), variability increased toward the carboxy terminus of the enterotoxic peptide region (aa 114-135) and was greatest between residues 135 and 141. Comparison of the amino acid sequences corresponding to the enterotoxic peptide region between strains isolated from asymptomatic neonates and those from children with diarrhoea failed to identify any conserved changes that correlated with the capacity of the virus to cause disease. Amino acids were relatively conserved in the domains important for viral morphogenesis.
The distribution of the nonstructural protein 1 (NSP1) alleles from human strain AU-1 and canine strain K9 among rotaviruses of human, feline, canine, bovine, and simian origin was studied by a dot blot hybridization assay. Human and feline strains belonging to the AU-1 genogroup had the same NSP1 allele, while canine and feline strains belonging to the canine-feline genogroup shared another NSP1 allele. This canine-feline NSP1 allele had a significant level of homology with the NSP1 of rhesus rotavirus strain MMU18006.
Two electrophoretically identical strains of group A rotavirus were isolated from diarrheic cows aged 3, 4, and 7 years on a dairy farm in Japan. They had a rare serotype combination of G8 and P6[1] and were shown by RNA-RNA hybridization to be most closely related to bovine strain NCDV-Lincoln (G6P6[1]).
A survey of 143 stool specimens collected during a 17-month period in Japan from diarrheal and asymptomatic kittens identified three rotavirus strains that were similar in their genomic RNA constellation to human rotavirus AU-1 (G3P3[9]), lending strong support to the view that rotaviruses belonging to the same genogroup are circulating in both the human and the feline population.
Inactivation of a range of viruses, such as adeno-, mumps, rota-, polio- (types 1 and 3), coxsackie-, rhino-, herpes simplex, rubella, measles, influenza and human immunodeficiency viruses, by povidone-iodine (PVP-I) and other commercially available antiseptics in Japan was studied in accordance with the standardized protocol in vitro. In these experiments, antiseptics such as PVP-I solution, PVP-I gargle, PVP-I cream, chlorhexidine gluconate, alkyldiaminoethyl-glycine hydrochloride, benzalkonium chloride (BAC) and benzethonium chloride (BEC) were used. PVP-I was effective against all the virus species tested. PVP-I drug products, which were examined in these experiments, inactivated all the viruses within a short period of time. Rubella, measles, mumps viruses and HIV were sensitive to all of the antiseptics, and rotavirus was inactivated by BAC and BEC, while adeno-, polio- and rhinoviruses did not respond to the other antiseptics. PVP-I had a wider virucidal spectrum, covering both enveloped and nonenveloped viruses, than the other commercially available antiseptics.
Sequence analysis of the VP7 gene was performed on twenty-one human isolates of serotype 3 related-rotavirus in China and Japan. The five Chinese isolates were found to be not similar to the 16 Japanese isolates and to SA11 (simian rotavirus). The Chinese isolates, especially CHW2 and CH-32, were different from the major serotype 3 human isolates. AU-1 and 02/92 which previously showed a wider spacing between RNA segments 10 and 11 by RNA polyacrylamide gel electrophoretic analysis, were more closely related to each other and could be differentiated from the other Chinese and Japanese isolates. For these reasons, serotype 3 viruses were considered to be intraserotypically more heterologous than serotype 1, 2 and 4 viruses.
RNA-RNA hybridization performed under high stringency conditions allows rotavirus isolates to be grouped together based on the overall similarity of their genomic RNA constellation. Classification by this scheme has been termed "genogrouping". Genogrouping has advanced molecular epidemiology of human rotaviruses. Major observations include (i) Interspecies transmission occurs in nature and (ii) Intergenogroup reassortment occurs in nature with or without exchange of serotype-determining genes. Genogrouping is a particularly valuable asset for determining the gene constellation of unusual rotavirus isolates.
Bovine-human reassortant strains containing ten human rotavirus gene segments and segment 4, encoding VP4, of a bovine rotavirus were isolated from the stool of an infected Bangladeshi infant during cell culture adaptation. Two plaque purified variants of this reassortant, one making very large (429-L4) and the other tiny (429-S4) plaques, were further analyzed. The electropherotypes of these variants were identical except for slight mobility differences in segment 4. The predicted sequence of amino acids (aa) 16-280 in VP4 proteins revealed four differences between variants even in this limited region, so no single difference could be linked to plaque size. The small plaque variant S4 was phenotypically unstable and mutated to a large plaque-former within a single cell culture passage. The predicted sequence of aa 16-280 of a large plaque variant derived from S4 revealed six changes, only one of which was common to that of the L4 strain, thus suggesting that multiple amino acid changes in VP4 may affect plaque size. Although the large plaque variant L4 grew faster and was released from cells more rapidly than S4, its replication and that of other rotaviruses tested (i.e. RRV, NCDV and Wa) was suppressed by S4 in coinfected cells. Using an RRV x S4 reassortant containing only RRV segment 4, it was established that suppression was linked to the S4 VP4 protein. This suppression could not be associated with inhibition of viral adsorption and, therefore, appeared to occur following internalization. Thus, a new property of the rotavirus VP4 protein has been identified in a bovine-human rotavirus reas-sortant.
We report the molecular characterization of rotavirus genotype P[8]G5 strains found in fecal specimens collected in four different regions of Brazil, using digoxigenin(dig)-labeled oligonucleotide probes, sequence analysis, and RNA-RNA hybridization. The closest sequence relationships of the neutralization antigens of these strains were to the VP4 protein of P1A[8]G1 strain KU (93.3% identity in amino acids 11 to 282) and to the VP7 protein of G serotype 5 strain OSU (87.6% identity in amino acids 8 to 232). Based on VP7 sequence differences, we designed dig-probes that allowed us to discriminate porcine OSU-like strains from G5 strains isolated from Brazilian infants. The genetic relationships of two P[8]G5 isolates to other rotavirus genogroups were analyzed by RNA-RNA hybridization with [32P]-GTP probes representative of serotypes P1A[8]G1 (Wa), P[8]G3 (AU17), and P9[7]G5 (OSU). The Brazilian P[8]G5 strains showed sequence homology with genes of Wa-like and OSU-like strains, suggesting that these two strains were naturally occurring reassortants between members of the Wa and porcine rotavirus genogroups. The identification of these strains in diverse geographic areas of Brazil underscores their stability and demonstrates the emergence of clinically important rotavirus diarrhea strains by reassortment.
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An anonymous unlinked HIV antibody test was conducted on 1632 Chlamydia trachomatis (C. trachomatis) antibody positive women from 10 institutes of 7 prefectures in Japan. All the sera were negative for both HIV-1 and HIV-2 antibodies. The result may support the suggestion that HIV prevalence is low among general population in Japan. Such a test as this study will be useful not only for developing a reliable HIV surveillance system but also for the study of sexual behavior of general population, since C. trachomatis infection is sensitive to reflect sexual contact.
In order to control the nosocomial infections by methicillin-resistant Staphylococcus aureus (MRSA) in the Akita University Hospital, the systematic surveillance for MRSA-infection has been done since October in 1991. We reviewed MRSA-isolation numbers, MRSA-detected patient numbers, risk factors of nosocomial infection and patient's basic diseases with the data of a total 336 cases, and then examined the microbiological characteristics of MRSA strains which had been isolated in our hospital in 1986 approximately 1994. The results obtained are as follows; 1) MRSAs were isolated at 13 per month on the average and the detection rate was 0.81 to 1,000 inpatients per day. 2) MRSAs were isolated more in the surgical ward. 3) Patients with 0 year old and more than 60 years old were more infected. 4) MRSA was isolated more from the immunocompromised patients with underlying diseases such as malignant tumors but half of the diseases were not affected by MRSA. 5) Seventy percent of patients had the risk factors of MRSA-transmission such as surgical operation and IVH-cathetering. 6) All isolates of MRSA strains in our hospital showed type II in coagulase type analysis and resistance to minocycline and ofloxacin. 7) It was suggested that one strain expanded throughout the hospital by several DNA analysis with the mecA gene in MRSA. These surveillance and microbiology data will be useful for our nosocomial mecA gene in MRSA. These surveillance and microbiology data will be useful for our nosocomial infection control.