Molecular characterization of G11P[25] and G3P[3] human rotavirus strains associated with asymptomatic infection in South India

Abstract

Rotaviruses are the major etiological agents of diarrhea in children less than 5 years of age. Two unusual rotavirus strains not previously reported in India, G11P[25] (CRI 10795) and G3P[3] (CRI 33594) were isolated from faecal samples of asymptomatic children in India. The strains were characterized by sequence analysis of the genes encoding the VP7, VP4, VP6, and NSP4. The G11P[25] strain was closely related to the human G11P[25] strains from Bangladesh (with 98% identity at the nucleotide [nt] level and the amino acid [aa] level for the VP7 gene and 96% identity at the nt and 98% at the aa level for the VP4 gene). The G3P[3] strain was found to be related to a G3P[3] strain isolated in Thailand (CMH222; 88% identity at the nt level and 97% at aa level for the VP7 gene and 84% identity at the nt level and 90% at the aa level for the VP4 gene). Phylogenetic analysis of the VP6 and the NSP4 genes revealed that the Vellore G11P[25] strain was of VP6 subgroup II and NSP4 genotype B. The G3P[3] strain was identified as NSP4 genotype C and the VP6 gene showed 97% identity at the deduced amino acid level with strain CMH222 (Thailand) strain but did not cluster with sequences of SGI, SGII, SGI+II or SG-nonI/nonII. Both strains had gene segments of animal rotavirus origin suggesting inter-species transmission of rotavirus, and in the case of G11P[25] possibly underwent reassortment subsequently with human strains resulting in an animal-human hybrid strain.

Fig. 1

Phylogenetic tree constructed from sequences of the VP7 gene of the G11 and G3 rotavirus strains and with other representative G-types using the Maximum Parsimony method. The tree was rooted using VP7 sequence of human Group C rotavirus Bristol strain. The bar indicates the variation scale.

Fig. 2

Phylogenetic tree constructed using Maximum Parsimony, and partial sequences of the gene encoding the VP6 of SGI, SGII SGI + II, and SG-nonI/nonII strains of human, and animal origin. Strain identifier, G and P type, and host from which isolates were obtained are indicates in columns 1-4. The strains described in this study are boxed.

Fig. 3

Phylogenetic tree constructed using Maximum Parsimony and sequences of the gene encoding the NSP4 of strains of human and animal origin. Strain identifier, G, and P type, and host from which isolates were obtained are indicated in columns 1-4. The strains described in this study are boxed.

Fig. 4

Phylogenetic tree constructed from amino acid sequences of the VP8* gene of the Vellore P[3] rotavirus strain and other P[3] strains using the Maximum Parsimony method. The bar indicates the variation scale.