Evolutionary history and global spread of the emerging g12 human rotaviruses

Abstract

G12 rotaviruses were first detected in diarrheic children in the Philippines in 1987, but no further cases were reported until 1998. However, G12 rotaviruses have been detected all over the world in recent years. Here, we report the worldwide variations of G12 rotaviruses to investigate the evolutionary mechanisms by which they managed to spread globally in a short period of time. We sequenced the complete genomes (11 segments) of nine G12 rotaviruses isolated in Bangladesh, Belgium, Thailand, and the Philippines and compared them with the genomes of other rotavirus strains. Our genetic analyses revealed that after introduction of the VP7 gene of the rare G12 genotype into more common local strains through reassortment, a vast genetic diversity was generated and several new variants with distinct gene constellations emerged. These reassortment events most likely took place in Southeast Asian countries and spread to other parts of the world. The acquirement of gene segments from human-adapted rotaviruses might allow G12 to better propagate in humans and hence to develop into an important emerging human pathogen.

FIG. 1.

Phylogenetic dendrograms based on the complete amino acid (aa) sequences of the structural proteins VP1, VP2, VP3, and VP6. Accession numbers can be found in the supplemental material. The numbers adjacent to the nodes represent the percentages of bootstrap support (of 1,000 replicates) for the clusters to the right of the nodes. Bootstrap values lower than 75% are not shown. Hu, human; La, lapine; Bo, bovine; Po, porcine; Si, simian; Eq, equine; Fe, feline; Rh, rhesus; Mu, murine; Av, avian. G12 strains analyzed in this study are in bold.

FIG. 2.

Phylogenetic dendrograms based on the complete amino acid (aa) sequences of the outer capsid proteins VP4 and VP7. Accession numbers can be found in the supplemental material. The sizes of the triangles are indications of the numbers of sequences that they represent. The numbers adjacent to the nodes represent the percentages of bootstrap support (of 1,000 replicates) for the clusters to the right of the nodes. Bootstrap values lower than 75% are not shown. Hu, human; Po, porcine; Fe, feline. G12 strains analyzed in this study are in bold.

FIG. 3.

Phylogenetic dendrograms based on the complete amino acid (aa) sequences of the nonstructural proteins NSP1, NSP2, and NSP3. Accession numbers can be found in the supplemental material. The numbers adjacent to the nodes represent the percentages of bootstrap support (of 1,000 replicates) for the clusters to the right of the nodes. Bootstrap values lower than 75% are not shown. Hu, human; La, lapine; Bo, bovine; Po, porcine; Si, simian; Eq, equine; Fe, feline; Rh, rhesus; Mu, murine; Av, avian. G12 strains analyzed in this study are in bold.

FIG. 4.

Phylogenetic dendrograms based on the complete amino acid (aa) sequences of the nonstructural proteins NSP4 and NSP5. Accession numbers can be found in the supplemental material. For NSP4, the three established genogroups are shown. The numbers adjacent to the nodes represent the percentages of bootstrap support (of 1,000 replicates) for the clusters to the right of the nodes. Bootstrap values lower than 75% are not shown. Hu, human; La, lapine; Bo, bovine; Po, porcine; Si, simian; Eq, equine; Fe, feline; Rh, rhesus; Mu, murine; Av, avian. G12 strains analyzed in this study are in bold.

FIG. 5.

Percentages of amino acid identity among different proteins (VP1, VP2, VP3, VP4, VP6, NSP1, NSP2, NSP3, NSP4, and NSP5) of G12 rotavirus strains and three reference strains from the major human rotavirus genogroups.

FIG. 6.

Percentages of amino acid identity among VP7 proteins of G12 rotavirus strains and other reference strains from 15 G genotypes. ARG, Argentina; BAN, Bangladesh; BEL, Belgium; BRA, Brazil; IND, India; JAP, Japan; PHI, Philippines; THA, Thailand.