Bhattacharya Rittwika, Sahoo Ganesh C, Nayak Mukti K, Saha Dhira Rani, Sur D, Naik T N, Bhattacharya S K, Krishnan Triveni
Division of Virology, National Institute of Cholera & Enteric Diseases, P33 CIT Road, Scheme XM, Beliaghata, Kolkata 700010, India.
Infect Genet Evol. 2006 Nov;6(6):453-8. doi: 10.1016/j.meegid.2006.02.005. Epub 2006 Apr 17.
Picobirnaviruses are a group of unclassified, non-enveloped, small spherical viruses, 35-41 nm in diameter without any apparent surface morphology. They have characteristic bisegmented double stranded RNA genome of two types namely large profile (2.3-2.6 kbp for the larger and 1.5-1.9 kbp for the smaller segment, respectively) or small profile (1.75 and 1.55 kbp for segments 1 and 2, respectively). Human picobirnaviruses (n=12 positives; 2/56 diarrhoeic children and 10/607 non-diarrhoeic children) with large (n=11) or small (n=1) genome pattern were observed in faecal specimens of children from a slum community by silver stained PAGE gels. Faecal specimen from four asymptomatic cases (P597_02_IND, K135_02_IND, A373_03_IND, A356_03_IND) and one diarrhoeic case (K135_03_IND) had genogroup I picobirnaviruses (1-CHN-97 like) showing amplicons within the 201 bp region, with primers PicoB25-PicoB43, targeting the conserved domain of RNA-dependent RNA polymerase (RdRp) gene. It was interesting to note that only the PBV strain P597_02_IND from Kolkata with large genome was closely related to a reported strain (similarity with 2-GA-91 from USA was 87% at the nucleotide level and 90% at the amino acid level). Sequence analysis showed three conserved amino acid domains as well as a highly conserved D-S-D motif, characteristic of RNA-dependent RNA polymerase gene of bisegmented, double stranded RNA viruses. Sequence data of the picobirnavirus A356_03_IND indicated strong heterogeneity with all other picobirnavirus strains sequenced till date. After nearly a decade a genogroup II picobirnavirus strain (R227_03_IND) was isolated from a diarrhoea case in the community, with small genome profile and amplified with specific primers PicoB23-PicoB24; but the sequence data showed that it was divergent from the hitherto reported prototype strain 4-GA-91 of genogroup II human picobirnaviruses.
微小双股RNA病毒是一组未分类的、无包膜的小型球形病毒，直径35 - 41纳米，表面无明显形态特征。它们具有特征性的双节段双链RNA基因组，有两种类型，即大基因组型（较大片段为2.3 - 2.6千碱基对，较小片段为1.5 - 1.9千碱基对）或小基因组型（片段1和片段2分别为1.75和1.55千碱基对）。通过银染聚丙烯酰胺凝胶电泳在一个贫民窟社区儿童的粪便标本中观察到了具有大基因组型（n = 11）或小基因组型（n = 1）的人类微小双股RNA病毒（n = 12个阳性；56名腹泻儿童中有2名，607名非腹泻儿童中有10名）。来自4例无症状病例（P597_02_IND、K135_02_IND、A373_03_IND、A356_03_IND）和1例腹泻病例（K135_03_IND）的粪便标本含有基因组I型微小双股RNA病毒（1-CHN-97样），使用靶向RNA依赖性RNA聚合酶（RdRp）基因保守结构域的引物PicoB25 - PicoB43在201碱基对区域内显示出扩增产物。有趣的是，仅来自加尔各答的具有大基因组的PBV毒株P597_02_IND与一株已报道毒株密切相关（在核苷酸水平上与来自美国的2-GA-91的相似性为87%，在氨基酸水平上为90%）。序列分析显示有三个保守氨基酸结构域以及一个高度保守的D - S - D基序，这是双节段双链RNA病毒的RNA依赖性RNA聚合酶基因的特征。微小双股RNA病毒A356_03_IND的序列数据表明与迄今测序的所有其他微小双股RNA病毒毒株有很强的异质性。经过近十年，从该社区的一例腹泻病例中分离出一株基因组II型微小双股RNA病毒毒株（R227_03_IND），其具有小基因组型，并用特异性引物PicoB23 - PicoB24进行了扩增；但序列数据表明它与迄今报道的基因组II型人类微小双股RNA病毒的原型毒株4-GA-91不同。
