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A rare human G10P rotavirus with a reassortment between bovine and human viruses was detected from a patient with acute gastroenteritis in Vietnam. Genetic analysis using complete coding sequences of all segments showed a genomic constellation of this virus of G10-P-I1-R1-C1-M1-A1-N1-T1-E1-H1. Its VP7 region was genetically related to that of a bovine rotavirus derived from Australia (strain VICG10.01), whereas all other genes were identical to those of a human rotavirus derived from Australia (strain Victoria/CK00047). These results indicate a possibility that the reassortment of the rotavirus was caused by immune escape in Australia and the rotavirus was carried to Vietnam. Additionally, this finding will help further understanding the evolution of rotaviruses circulating in Vietnam.
Rotavirus, which belongs to the family Reoviridae, is a common pathogen in causing acute gastroenteritis in humans, especially children (2). Annually, rotavirus causes 611,000 deaths worldwide (9). Rotavirus is composed of double-stranded RNA including 11 segments: the structural proteins of VP1 to VP4, VP6, and VP7 and the nonstructural proteins of NSP1 to NSP6. Since VP7 and VP4 are related to the binding to specific receptors in hosts and they contain neutralizing epitopes, a rotavirus classification is based on a combination of G type for VP7 and P type for VP4 (2, 5, 11). Recent reports suggest characterization of all rotavirus segments in order to correctly identify the genetic diversity and infectious source of the virus (7, 8).
In an epidemiological study of rotavirus in feces collected from children with acute gastroenteritis during January 2008 to July 2008 in Vietnam, a rare G10P rotavirus (strain 163/Vietnam) was detected from a child. The complete coding regions of all 11 segments of this virus were sequenced by primer walking. Cycle sequencing was conducted with a Genome Lab DTCS Quick Start kit (Beckman Coulter Inc., Fullerton, CA), and then sequences were analyzed on the CEQ 2000XL DNA analysis system (Beckman Coulter Inc.). The DNA sequences were assembled with CEQ 2000XL DNA analysis system software (version 4.3.9; Beckman Coulter Inc.). Our genetic analysis demonstrated that the genomic constellation of G10P rotavirus was G10-P-I1-R1-C1-M1-A1-N1-T1-E1-H1. Interestingly, this G10P rotavirus was closely related to bovine rotavirus (strain VICG10.01) in the VP7 gene, sharing 98% identity at the nucleotide level. Other segments encoding 5 structural proteins and 6 nonstructural proteins of this virus were highly identical to those of human G1P rotavirus (strain Victoria/CK00047), sharing at least 99% identity at the nucleotide level. Therefore, the 163/Vietnam strain had reassortment between bovine and human rotaviruses.
In this study, we characterized an unusual G10P rotavirus that was composed of a VP7 gene derived from bovine rotavirus and other genes derived from human rotavirus. The G10 rotavirus primarily causes acute gastroenteritis in cows, buffalo calves, and foals (3, 4, 6). The detection of G10 rotavirus from human feces recently was reported mainly in Africa and India (1, 10). However, the VP7 gene of the 163/Vietnam strain was genetically closer to that of bovine G10 rotavirus (98% nucleotide identity) than to that of any human G10 rotaviruses (<89% nucleotide identity). The finding suggested that the 163/Vietnam strain is a newly divergent human G10P rotavirus. The rotavirus virion is composed of the outer (consisting of VP7 and VP4), middle (consisting of VP6), and inner (consisting of VP2) layers (2). The VP7 is associated with interaction with neutralizing antibody (2). In this study, the 163/Vietnam strain contained the VP7 sequence derived from bovine rotavirus, which led us to hypothesize that this virus might escape from potential immunity in the infected patient.
In conclusion, we report the presence of a new human rotavirus containing a sequence of bovine rotavirus. Continuous surveillance is needed to understand the prevalence of this new virus in causing acute gastroenteritis in Vietnam.
The GenBank accession numbers for the complete coding regions of all 11 segments of the new human G10P rotavirus strain 163/Vietnam are AB714258 to AB714268.
This study was supported by grants-in-aid from the Ministry of Education and Sciences and the Ministry of Health, Labor and Welfare, Japan.