a fecal specimen was obtained from a piglet experimentally infected with strain ska-1 , which was first isolated from a pig with diarrhea in tottori prefecture , japan .
rna was extracted from a 20% fecal suspension in phosphate - buffered saline by using the isogen - ls kit ( nippon gene ltd . ,
( 13 ) with some modifications ( 14 ) . during single - primer amplification ,
several dna bands were detected that appeared to correspond to rna segments of a rotavirus .
dna was purified by using a wizard sv gel and a pcr clean - up system ( promega , madison , wi , usa ) and cloned into the pcr - topo vector by using a topo ta cloning kit ( invitrogen , carslbad , ca , usa ) .
sequence analysis and comparisons were performed by using genetyx - win software ( genetyx , tokyo , japan ) and mega software ( www.megasoftware.net/ ) .
we selected 4 genes encoding vp4 , vp6 , vp7 , and nsp4 for sequence analysis .
sequence data were obtained for comparative sequence analysis among group a and nongroup a rotaviruses .
there was little identity for any of the 4 genes between ska-1 and group a or c rotaviruses .
in contrast , nucleotide and amino acid sequences of the 4 genes of ska-1 showed relatively high identities with those of a novel group of rotavirus strains ( j19 and b219 ) .
the vp6 gene , which is associated with group specificity , of ska-1 showed highest identities among the 4 genes with those of the novel group human rotaviruses : 72%73% at the nucleotide level and 76%77% at the amino acid level .
vp6 also showed relatively high identities with those of group b rotaviruses : 52%53% at the nucleotide level and 36%40% at the amino acid level ( table ) .
the other 3 genes ( vp4 , vp7 , and nsp4 ) , also showed high identities with those of the novel group of human rotaviruses , although identity values were lower than those for the vp6 gene ( table ) .
* vp , viral protein ; ns , nonstructural protein ; na , not available .
: ska-1 vp4 , ab576625 ; ska-1 vp6 , ab576626 ; ska-1 vp7 ab576627 ; ska-1 nsp4 ; ab576628 . 
lengths and nucleotide sequences of the 5 and 3 noncoding regions of the 4 genes of ska-1 were similar to those of the novel group of rotaviruses . using the vp7 gene as a reference , we identified sequences of the 5 noncoding region of vp7 as 5-ggaactttaaagcc-3 for strain ska-1 , 5-ggcaatttgaagcc-3 for the novel group of human rotaviruses , and 5-ggcaataaa-3 for group b rotaviruses .
phylogenetic analysis of the 4 genes also showed that ska-1 is closely related to the novel group of human rotavirus strains ( j19 and b219 ) ( figure ) .
phylogenetic trees for a ) viral protein ( vp ) 4 , b ) vp6 , c ) vp7 , and d ) nonstructural protein 4 genes of group a , b , and c rotaviruses , a novel group of human rotaviruses , and porcine rotavirus strain ska-1 .
although group a rotaviruses have been extensively studied , nongroup a rotaviruses have not been extensively studied . in particular , there is little information on group d , e , f , and g rotaviruses .
a novel group of human rotaviruses ( j19 and b219 ) are not related to any other groups of rotaviruses .
rotavirus strain ska-1 was detected in a fecal specimen from a piglet with diarrhea in japan , and was isolated in ma-104 cells in 1999 .
its group specificity was suggested to be group b on the basis of reverse transcription pcr results with a group b  specific primer .
however , our sequence analysis showed that the porcine ska-1 strain is different from group b human and porcine rotaviruses .
nucleotide and amino acid sequences of ska-1 did not show identities with those of group a or c rotaviruses , although they showed some relatedness to those of group b rotaviruses .
however , high identities were observed between ska-1 and a novel group of human rotaviruses . in addition
, there are similarities in the 4 genes analyzed in this study between ska-1 and the novel group of human rotaviruses : 1 ) nucleotide sequences and nucleotide numbers of noncoding regions at the 5 and 3 ends are similar to each other ; 2 ) lengths of nucleotide and deduced amino acid sequences are similar to each other ; and 3 ) phylogenetic analysis showed that these viruses are in the same cluster . except for porcine strain ska-1 , there has been no report of animal rotaviruses being classified into a novel group of human rotaviruses .
a survey of the prevalence of antibodies against ska-1 among humans and animals , including pigs , would be useful .
a classification system for nongroup a rotaviruses has not been established because 1 ) information on nucleotide sequences of group d , e , f , and g rotaviruses is lacking ; 2 ) no expressed reference vp6 proteins are available ; 3 ) reference strains of group d 
g rotaviruses have not been adapted to cell culture ; and 4 ) it is not known whether fecal samples or rna or extracted rna of group e 
g strains are available in any laboratories . on the basis of serologic characterization and sequence analysis , a classification system for nongroup
a rotaviruses , which includes the novel group of human and porcine rotaviruses such as j19 , b219 , and ska-1 , should be established .
 we determined nucleotide sequences and inferred amino acid sequences of viral protein ( vp ) 4 , vp6 , vp7 , and nonstructural protein 4 genes of a porcine rotavirus strain ( ska-1 ) from japan . 
 the strain was closely related to a novel group of human rotavirus strains ( b219 and j19 ) . 
The Study
Conclusions