Emergence of G9 P[6] human rotaviruses in Argentina: phylogenetic relationships among G9 strains

Abstract

Because rotavirus diarrhea can be reduced through vaccination and because current vaccine candidates provide protection against only the most common G antigenic types (G1 to G4), detection of uncommon G types is one of the main goals of rotavirus surveillance. After a 2-year nationwide rotavirus surveillance study in Argentina concluded, surveillance was continued and an increase of G9 prevalence in several Argentine cities was detected. During this period G9 strains predominated in the south, and a gradient of decreasing G9 prevalence was observed from south to north (41 to 0%). Sequence analysis of gene 9, encoding the G antigen, showed that Argentine strains cluster with most G9 isolates from other countries, showing less than 2% nucleotide divergence among them, but are distinctive from them in that they present some unique amino acid changes. Our results agree with reports of increased G9 prevalence in other parts of the world, suggesting the need to incorporate G9 into candidate rotavirus vaccines.

FIG. 1

Phylogenetic analysis of the VP7 deduced amino acid sequences of serotype G9 strains. A phylogenetic tree was constructed based on the Kimura method of the PHYLIP package. Percentage bootstrap values above 50% are shown at the branch nodes. Bold letters indicate Argentine strains. IN, India; UK, United Kingdom; BD, Bangladesh; MW, Malawi; US, United States; Men, Mendoza; Ush, Ushuaia; LP, La Plata; BA, Buenos Aires.

FIG. 2

Deduced amino acid sequences of Argentine strains compared to reference strain 116E. Amino acids underlined and in bold letters indicate regions that are highly variable among G types.