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S Urasawa

Publications and source records attributed to S Urasawa.

At least 73 records · Page 4Linked to original sources
PubMed1992

Distribution of serotypes of human rotavirus in different populations.

Serotyping is a useful tool to study the epidemiologic characteristics of rotaviruses in large populations and to assess the need for a vaccine to protect against all strains. By using an enzyme immunoassay with serotype-specific monoclonal antibodies to the four most common rotavirus serotypes, we analyzed 1,183 rotavirus-positive specimens from 16 stool collections in eight countries on four continents that were obtained from 1978 to 1989. Of the 926 strains (78%) that could be serotyped, 48% were serotype 1, 8% were serotype 2, 15% were serotype 3, and 7% were serotype 4. Twenty-two percent had insufficient numbers of double-shelled virus particles to react with the monoclonal antibody of the VP4 rotavirus protein and therefore could not be serotyped. Our results indicate that vaccines being developed must provide the greatest coverage against serotype 1 and that the serotype distribution cannot be predicted currently by the geographic area or prevalence in the preceding year.

Antibodies, Monoclonal↗
PubMed1991

Operational overlapping of cross-reactive and serotype-specific neutralization epitopes on VP7 of human rotavirus serotype 3.

VP7-specific neutralizing monoclonal antibodies (N-MAbs) to serotype 3 human rotavirus were produced to analyze serotype 3-specific and cross-reactive neutralization epitopes on VP7. On the basis of the reactivity patterns in neutralization tests with various human and animal strains, a total of 10 N-MAbs could be classified into four groups; five antibodies specific to serotype 3 were divided into two groups, and five antibodies consisted of two groups which are cross-reactive with strain 69 M (serotype 8) or strain WI61 (serotype 9). Seven N-MAbs showed the same reactivity patterns to the virus strains in both neutralization tests and enzyme-linked immunosorbent assay (ELISA), while three N-MAbs specific to serotype 3 in neutralization showed a cross-reactivity with the serotype 8 strain in ELISA. Neutralization-resistant mutants of serotype 3 strains P and YO were selected by the N-MAbs. Cross-neutralization tests between the mutants and the MAbs indicated the presence of two serotype-specific (S1 and S2) and three cross-reactive (C1, C2, and C3) epitope groups. S1, S2, and C3 epitope groups overlapped operationally each other, and the S1 epitope group had an overlapping with the C1 epitope group. However, C2 epitope group identified by the MAbs which neutralized serotypes 3 and 9, had no operational overlapping with any other epitope groups.

Animals↗
PubMed1991

Preparation and characterization of a neutralizing monoclonal antibody directed to VP4 of rotavirus strain K8 which has unique VP4 neutralization epitopes.

For selecting the neutralizing monoclonal antibodies (N-MAbs) directed to VP4 of rotavirus strain K8, which has unique VP4 neutralization epitopes, we prepared several reassortant viruses by mixed infection of two different strains K8 (serotype 1) and P (serotype 3) in vitro: three reassortant clones having VP4 of K8 and VP7 of P and four clones having VP4 of P and VP7 of K8. By using these reassortants in screening hybridomas, a N-MAb (K8-2C12) directed to strain K8-specific VP4 was obtained. The MAb K8-2C12 neutralized only K8 when tested against numerous strains of different serotypes, while in enzyme-linked immunosorbent assay this MAb reacted also with simian rotavirus SA11 (serotype 3), bovine rotavirus NCDV (serotype 6), and human rotavirus (HRV) strain 69M (serotype 8). Neutralization-resistant mutants of K8 were selected by the K8-2C12 antibody and VP4 amino acid sequences of the mutants were determined. Single amino acid substitution was detected in the three mutant clones at position 394, which is included in the major cross-reactive neutralization region identified in other rotaviruses.

Amino Acid Sequence↗
PubMed1991

Analysis of the newly identified neutralization epitopes on VP7 of human rotavirus serotype 1.

Neutralizing monoclonal antibodies (MAbs) directed to the VP7 protein and neutralization-resistant mutants were used to analyse the antigenic structure of VP7 of human rotavirus serotype 1. Cross-neutralization tests using the MAbs and the resistant mutants indicated the existence of two functionally independent neutralization epitope regions (S1 and S2) on VP7. Region S1 corresponds to a single epitope domain of VP7 which has been detected previously. Two MAbs prepared in this study recognized the S1 region, and the resistant mutants they selected had amino acid substitutions at positions 94 or 213. On the other hand, region S2 is considered to be a novel epitope. Single or double amino acid substitutions were detected in the variable regions (amino acid positions 145, 217 and 221) and in the constant regions (positions 104, 201 and 291) of the VP7 protein of mutants selected by MAbs directed to the S2 region. It was suggested that the variable region E (amino acids 208 to 221) includes two independent neutralization sites, and that amino acid substitutions in the constant region of VP7 also affect serotype-specific neutralization epitopes. Neutralization epitopes on VP7 are considered to be highly dependent on the conformation of VP7.

Animals↗
PubMed1991

Molecular and antigenic analyses of serotypes 8 and 10 of bovine rotaviruses in Thailand.

Antigenic and genomic properties of non-serotype 6 bovine rotaviruses isolated in Thailand and Japan were studied by cross-neutralization tests, nucleotide sequence determination of the VP7 gene, and RNA-RNA hybridization. Two Thai strains (61A and A44) were serologically related to a Japanese isolate KK3 which has been assigned to serotype 10. In contrast, strain A5 was found to be antigenically similar to human strain 69M with serotype 8 specificity, although strain A5 showed a one-way cross-reaction with serotype 6 strain NCDV. VP7 sequence analysis confirmed these results. High degrees of similarity in nucleotide and amino acid sequences (92.5 to 98.2% and 96.3 to 97.9%, respectively) were found among the VP7 genes of the four serotype 10 bovine strains (61A, A44, KK3 and B223). The VP7 amino acid sequence of strain A5 was similar to those of serotype 8 human strains (91.7% and 94.8% for strains B37 and 69M, respectively). In RNA-RNA hybridization experiments, a high level of overall relatedness was found among the three serotype 10 bovine strains (61A, A44 and KK3), and strains A5 and NCDV were also moderately related to the three serotype 10 viruses. All the bovine rotaviruses tested in this study, regardless of their serotype specificity, exhibited a moderate genetic-relatedness to strain 69M of serotype 8, and, to a lesser extent, to serotype 2 human rotavirus strains.

Amino Acid Sequence↗
PubMed1991

Analysis of the neutralization epitopes on human rotavirus VP7 recognized by monotype-specific monoclonal antibodies.

Three anti-VP7 monoclonal antibodies (MAbs) which neutralized only two strains (K8 and S12) of five serotype 1 human rotaviruses (HRVs) were obtained, and neutralization epitopes recognized by these 'monotype-specific' MAbs were analysed by epitope mapping and sequencing of the VP7 genes. Neutralization-resistant mutants of K8 and S12 were selected by the monotype-specific MAbs and serotype 1-specific MAbs prepared previously. Cross-neutralization tests between MAbs and neutralization-resistant mutants of K8 and S12 indicated that epitopes of monotype-specific MAbs operationally overlap with those of serotype 1-specific and cross-reactive MAbs recognizing the S1 region. Sequence analyses of the VP7 genes indicated that VP7s of strains K8 and S12, which belong to a monotype of serotype 1 viruses, possessed amino acids at positions 42 and 87 different from other serotype 1 HRVs. Furthermore, amino acid substitution sites of representative mutants of K8, selected by the monotype-specific MAbs, were identified at positions 96, 97 and 100. These results imply that amino acids in variable region B (amino acids 87 to 101) are involved in the monotype-specific neutralization epitope as well as serotype-specific neutralization epitopes.

Amino Acid Sequence↗
PubMed1991

Analysis of human rotavirus strains prevailing in Bangladesh in relation to nationwide floods brought by the 1988 monsoon.

The virologic character of human rotavirus strains prevailing in Bangladesh was investigated in relation to the devastating nationwide floods brought by the 1988 monsoon. Human rotaviruses contained in stool specimens that were collected from inpatients with infantile and adult diarrhea in two hospitals in Mymensingh over a 13-month period (January 1988 to January 1989) and in one hospital in Dhaka over a 3-month period (February to April 1988) were examined for their subgroup, VP7 serotype, and RNA electropherotype. In concurrence with the spread of the flood (from the middle of August 1988), the number of infantile and adult diarrhea patients increased greatly. At the same time, the proportion of rotavirus-positive specimens in all diarrhea cases also increased remarkably, reaching 54 and 45% in September and October, respectively. An electrophoretic analysis of viral RNA revealed 17 distinct patterns of viral RNA (14 long and 3 short electropherotypes) and a considerable number of mixed electropherotypes, suggesting the simultaneous infection of some patients with more than two rotavirus strains. It was noteworthy that electropherotypes of rotavirus strains prevailing in the community changed considerably after the spreading of the flood and that the frequency of virus specimens showing mixed electropherotypes increased significantly during the flood period. These results suggest that sudden environmental change caused by the devastating floods seriously affected the epidemiology of rotavirus infections by increasing the opportunity of transmission of the virus and by reducing the resistance of the host to infection. In both pediatric and adult patient groups, serotypes 1 and 2 were the most frequent ones detected, followed by serotype 4.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1991

Antibody response to serotype-specific and cross-reactive neutralization epitopes on VP4 and VP7 after rotavirus infection or vaccination.

By using a competitive solid-phase immunoassay with serotype-specific and cross-reactive neutralizing monoclonal antibodies directed at VP4 and VP7, we tested the antibody responses to some neutralization epitopes on VP4 and VP7 in individuals infected or vaccinated with rotavirus. Antibody responses to VP7 epitopes of the infecting serotype of virus were found at a high frequency in both infants and children. In contrast, antibody responses to VP4 and heterotypic VP7 were observed only when the individuals possessed antibodies to any serotype of rotavirus in their acute-phase or prevaccination sera.

Antibodies, Viral↗
PubMed1991

Preparation of a neutralizing monoclonal antibody specific to serotype 8 rotavirus strains with a super-short RNA pattern.

Extensive cross-neutralization tests have identified seven serotypes of rotavirus. Recently, it has been reported that several human strains (69M, B37 and B38) with a super-short RNA pattern carry new serotype specificity (serotype 8). By using the strain 69M as an immunizing antigen, we prepared a neutralizing monoclonal antibody (designated 69M-2D). In neutralization tests using 18 human and two animal rotavirus strains with different serotype specificities, the 69M-2D antibody was found to neutralize only serotype 8 strains. Also, in an enzyme-linked immunosorbent assay (ELISA), the antibody reacted exclusively with the serotype 8 strains. Thus, the reactivity pattern of the 69M-2D antibody was serotype 8-specific. This antibody should be useful as another reagent for serotyping rotaviruses by ELISA.

Animals↗
PubMed1990

Presumptive seventh serotype of human rotavirus.

Four group A human rotaviruses having antigenic specificity of subgroup I and 'long' RNA electropherotype were isolated in MA104 cell cultures. Cross-neutralization tests with hyperimmune antisera suggested that they are serologically distinct from the six previously recognized human rotavirus serotypes.

Animals↗
PubMed1990

Serotype variation of human group A rotaviruses in two regions of the USA.

The first longitudinal study of group A rotavirus serotype distribution in the USA is reported. ELISAs incorporating neutralizing monoclonal antibodies specific for the VP7 protein of serotypes 1, 2, 3, and 4 were used to determine the antigenic variation of group A rotaviruses in two collections of stool specimens. Stool samples were collected from children hospitalized during 1979-1989 at Texas Children's Hospital, Houston, and from children from a more rural population hospitalized during 1981-1989 in the north-central USA. The predominant serotype varied from year to year in Houston, with serotypes 1, 3, and 4 each predominant in 1 or more years. In the north-central population only serotype 1 was predominant each year. Within a single rotavirus season in the Houston area, serotypes were not equally distributed by week of the season or county of residence. These differences in the distribution of serotypes have broad implications for the design and interpretation of vaccine programs.

Age Factors↗
PubMed1990

Identification of operationally overlapping and independent cross-reactive neutralization regions on human rotavirus VP4.

Cross-reactive neutralization epitopes on VP4 of human rotavirus (HRV) were analyzed by the use of VP4-specific neutralizing monoclonal antibodies (N-MAbs) and MAb-resistant mutants. Seven anti-VP4 N-MAbs obtained in this study by using HRV serotypes 1 and 3 as immunizing antigens showed a variety of cross-reactivity patterns to 20 HRV strains with different serotype specificity in neutralization tests and a broader cross-reactivity to them was found for four N-MAbs in an enzyme-linked immunosorbent assay. On the basis of the reactivity patterns against rotaviruses in neutralization tests, these seven N-MAbs were classified into four groups. Cross-neutralization tests using a total of 12 pairs of MAbs and resistant mutants, including five pairs which had been prepared previously, showed that VP4 of HRV (strain KU) contained two independent antigenic regions. One, region C1, was recognized by a single MAb (YO-2C2) and the other was made up of two antigenic regions (C2 and C3) which overlapped operationally. Identification of amino acid substitution sites on VP4 of representative mutants of HRV strain KU indicated that amino acid positions 385 or 392 and 428 or 433 were critical for the C2 and C3 regions, respectively. These results suggested that regions C2 and C3 exist as conformational antigenic sites.

Animals↗