Abstract
Direct interspecies transmissions of group A rotaviruses (RVA) have been reported under natural conditions. However, the pathogenicity of RVA has never been directly compared in homologous and heterologous hosts. The bovine RVA/Cow-tc/KOR/K5/2004/G5P[7] strain, which was shown to possess a typical porcine-like genotype constellation similar to that of the G5P[7] prototype RVA/Pig-tc/USA/OSU/1977/G5P9[7] strain, was examined for its pathogenicity and compared with the porcine G5P[7] RVA/Pig-tc/KOR/K71/2006/G5P[7] strain possessing the same genotype constellation. The bovine K5 strain induced diarrhea and histopathological changes in the small intestine of piglets and calves, whereas the porcine K71 strain caused diarrhea and histopathological changes in the small intestine of piglets, but not in calves. Furthermore, the bovine K5 strain showed extra-intestinal tropisms in both piglets and calves, whereas the porcine K71 strain had extra-intestinal tropisms in piglets, but not in calves. Therefore, we performed comparative genomic analysis of the K71 and K5 RVA strains to determine whether specific mutations could be associated with these distinct clinical and pathological phenotypes. Full-length sequencing analyses for the 11 genomic segments for K71 and K5 revealed that these strains were genetically nearly identical to each other. Two nucleotide mutations were found in the 5′ untranslated region (UTR) of NSP5 and the 3′ UTR of NSP3, and eight amino acid mutations in VP1-VP4 and NSP2. Some of these mutations may be critical molecular determinants for RVA virulence and/or pathogenicity.
Highlights
Group A rotavirus (RVA), a member of the Reoviridae family, is one of the major pathogens that causes severe and acute dehydrating diarrhea in young children and in a wide variety of domestic animals [1,2,3]
A whole genome-based genotyping classification system for RVA has been proposed by the Rotavirus Classification Working Group (RCWG), which is based on nucleotide percentage identity cut-off values for each of the 11 RVA genomic segments [5,6,7]
Virus titers were assessed by cell cultured immunofluorescence (CCIF) assay using a monoclonal antibody against the VP6 protein of the OSU porcine strain, and were expressed as fluorescence focus units per milliliter (FFU/mL)
Summary
Group A rotavirus (RVA), a member of the Reoviridae family, is one of the major pathogens that causes severe and acute dehydrating diarrhea in young children and in a wide variety of domestic animals [1,2,3]. The rotavirus genome is enclosed in three concentric layers and is comprised of 11 segments of double-stranded (ds) RNA, encoding six structural proteins (VP1-4, VP6 and VP7) and five or six nonstructural proteins (NSP1-NSP5/6) [1,2,4]. This unique segmented nature of the RVA genomes. A whole genome-based genotyping classification system for RVA has been proposed by the Rotavirus Classification Working Group (RCWG), which is based on nucleotide percentage identity cut-off values for each of the 11 RVA genomic segments [5,6,7]. The G6, G8, and G10 genotypes are the major types in combination with either the P[1], P[5] or P[11] genotype [13,14]
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