Isolation of a human rotavirus strain with a super-short RNA pattern and a new P2 subtype

Abstract

Super-short rotavirus strains that have a rearranged gene segment 11 are rarely found in humans, and only five isolates, all from Southeast Asia, have been described in the literature. We report the first isolation in Japan from an infant with severe diarrhea of a rotavirus possessing a super-short RNA pattern. This strain, designated AU19, had a G1 VP7 and is also the first isolate in Japan that possesses a P2[6] VP4. Furthermore, the P2[6] VP4 carried by AU19 was divergent in the hypervariable region of the amino acid sequence from the P2A[6] VP4s carried by asymptomatic neonatal strains or from the P2B[6] VP4 carried by porcine rotavirus strain Gottfried. Thus, AU19 is likely to represent a new VP4 subtype, which we propose to call P2C. Given the recent emergence of the P2[6] VP4s in India, Brazil, and the United States and the role of VP4 in protective immunity, further scrutiny is justified to see whether the emergence of the previously underrepresented P2[6] VP4 serotype is related to this new P2 subtype.

FIG. 1

The electropherotype of AU19 in comparison with reference laboratory strains. SA11 and Wa possess long RNA patterns, KUN possesses a short RNA pattern, and 69M is the prototype super-short strain. Note the lowest migration rates of gene segment 10 of AU19 as well as 69M (indicated by an arrowhead).

FIG. 2

A phylogenetic tree for the hypervariable region of VP4 constructed by the neighbor-joining method. The horizontal distance between two strains is proportional to the genetic distance between these two strains. The distance is expressed as the number of substitutions per 100 sites (percent divergence). Bootstrap probabilities equal to or greater than 850 (of 1,000 trials) are indicated.