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Rotavirus, a member of the family Reoviridae, was identified as the leading etiological agent of severe gastroenteritis in infants and young children in 1973. The rotavirus genome is composed of 11 gene segments of double-stranded (ds)RNA. During the last 40 years, a large amount of basic research on rotavirus structure, genome, antigen, replication, pathogenesis, epidemiology, immune responses, and evolution has been accumulated. This article reviews the fundamental aspects of rotavirology including recent important achievements in research.

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.

ヒトレオウイルス様因子 (HRLA) あるいはウシレオウイルス様因子 (NCDV) を抗原に用いて測定した下痢症患者ならびに非患者の年齢別血清抗体価の比較検討の結果, 次のような成績を得た.1. 患者血清ではHRLA-CF抗体とNCDV-CF, -PT (counter-immunoelectro-osmophoresis による沈降反応), -NT (中和) 抗体との間には高い相関関係が見られ, その強さはNCDV-PT=NCDV-NT>NCDV-CFの順であった. 学童患者血清ではNCDV-CF抗体価に比して-NT抗体価が高い傾向が見られた.2. NCDV-CF, -NT抗体価の年齢分布を検討した結果, 患者の多発する1歳前後よりCF, NTともに高い例が増加し, 中和抗体陽性者は年齢とともに増加し, 成人では96%に達するが, CF抗体は学童期を過ぎるとやや減少して成人で陽性率63%を示した.以上, 患者群でHRLA-CF抗体の上昇にほぼ平行してNCDV-NT, -CF抗体の上昇およびNCDV-PT抗体の出現が検出され, これらのうちNTおよびPT両反応の感度が高く乳幼児の初感染における本症の血清学的診断に適していると考えられた. いっぽう, 過去の感染の累積を知る意味での血清疫学的調査にはHRLAの代用としてNCDV-NT反応が, 現時点ではもっとも有用であることが判明した.