Genetic diversity of human and animal rotaviruses from the perspective of genome homology

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Rotaviruses are implicated as a single most important causative agent of acute diarrheal illness in infants and young children. Fundamental to the development of effective vaccines for the prevention of diarrheal diseases caused by rotaviruses is a better understanding of the mechanisms by which rotaviruses undergo extensive genetic diversity. This study was undertaken to elucidate such mechanisms by analyzing with RNA-RNA hybridization tests clinical specimens collected over an eight year period.Twenty four stool rotaviruses that comprised 22 distinct electropherotypes were selected for genome analysis. When the genomic RNAs from these stool rotaviruses were hybridized to the probes prepared from prototypes representing three human rotavirus genogroups, any one of the isolates showed a high degree of homology only with one of the three probes ; these results confirmed and extended our previous observation on the existence of three distinct genogroups among human rotaviruses. Genetic relationships among human and animal rotaviruses were also examined by RNA-RNA hybridization assays in which genomic RNAs from 14 rotavirus strains derived from seven different host species were hybridized with the probes prepared from 11 strains representing rotaviruses from those seven host species. In general, higher level of homology that allowed classification into the same genogroup was shared among rotaviruses recovered from the same animal species but this level of homology was not found among rotaviruses derived from different host species. However, such a high level of homology was observed between a feline rotavirus strain and a canine rotavirus strain as well as between a human rotavirus strain and another feline rotavirus strain. The sharing of genogroup is considered to be resulted from interspecies transmission of rotaviruses from one animal species to ano therunder natural conditions.