Sequencing and phylogenetic analysis of human genotype P[6] rotavirus strains detected in Hungary provides evidence for genetic heterogeneity within the P[6] VP4 gene

Abstract

Although rotavirus genotype P[6] is one of the three most common VP4 specificities associated with human infection, the relatively few sequence data available in public databases suggest that the genetic variability within P[6] might be presently unexplored. Thus far, two human P[6] lineages (M37-like and AU19-like) and a single porcine P[6] lineage (Gottfried-like) have been identified by phylogenetic analysis. Serologic studies demonstrated that these three lineages are antigenically distinct from each other, a finding based on which they were classified into three subtypes, P2A[6] (M37-like), P2B[6] (Gottfried-like), and P2C[6] (AU19-like). To study heterogeneity within this genotype, we selected for molecular characterization a total of six P[6] strains detected during an ongoing surveillance in Hungary. The variable region of the VP4 gene was subjected to sequencing and phylogenetic analysis. Our data indicated that these six strains fell into two phylogenetic lineages distinguishable from the human lineages M37-like and AU19-like and from the porcine lineage Gottfried-like. Further studies are needed to understand whether these two novel lineages are genuine human strains or might have originated from animal strains and to evaluate the antigenic relationship of the novel Hungarian P[6] strains to the three established subtypes.

FIG. 1.

Phylogenetic tree for the VP8* fragment of VP4 gene (nt 200 to 700) of strains with P[6] specificity by using the neighbor-joining algorithm. Bootstrap values greater than 60% are indicated at the branch nodes. The scale bar is proportional to the genetic distance. An outgroup sequence (P[19]) was included to better understand the phylogenetic relationships among P[6] strains. Data about the associated G serotype, the country of isolation, and whether the strain was identified from symptomatic (S) or asymptomatic (AS) infections are displayed where information was available. Unknown data are indicated with a question mark.

FIG. 2.

An alignment for the partial amino acid sequences of genotype P[6] specificity. The amino acid sites addressed to be involved in attenuation are highlighted (white letters on black background) (5, 28). The residues conserved across the minor lineages of human P[6] strains and the porcine strain Gottfried are also shaded (gray). The line separates the asymptomatic strains (above) and symptomatic strains (below). Only substitutions distinct from the consensus (Gottfried) are shown.