Human rotavirus strains bearing VP4 gene P[6] allele recovered from asymptomatic or symptomatic infections share similar, if not identical, VP4 neutralization specificities

Complete genome sequence analysis of candidate human rotavirus vaccine strains RV3 and 116E

Rotaviruses (RVs) cause severe gastroenteritis in infants and young children; yet, several strains have been isolated from newborns showing no signs of clinical illness. Two of these neonatal strains, RV3 (G3P[6]) and 116E (G9P[11]), are currently being developed as live-attenuated vaccines. In this study, we sequenced the eleven-segmented double-stranded RNA genomes of cell culture-adapted RV3 and 116E and compared their genes and protein products to those of other RVs. Using amino acid alignments and structural predictions, we identified residues of RV3 or 116E that may contribute to attenuation or influence vaccine efficacy. We also discovered residues of the VP4 attachment protein that correlate with the capacity of some P[6] strains, including RV3, to infect newborns versus older infants. The results of this study enhance our understanding of the molecular determinants of RV3 and 116E attenuation and are expected to aid in the ongoing development of these vaccine candidates.

Molecular epidemiology of rotaviruses among healthy calves in Japan: isolation of a novel bovine rotavirus bearing new P and G genotypes

A total of 171 fecal specimens collected from healthy calves on a beef farm in Gifu Prefecture, Japan in 2006-2007 were examined for group A rotaviruses by RT-semi-nested PCR targeting the coding region for VP8*. Nine specimens were positive for rotavirus. G and P genotyping indicated that one strain was G10P[11]-like and six strains were considered to be the same unknown G and P genotypes. Among these six untypeable strains, one strain, AzuK-1, was adapted to cell culture and analyzed. Sequence and phylogenetic analyses of the full lengths of VP4 and VP7 genes revealed that AzuK-1 strain is a novel bovine rotavirus bearing new G21 and P[29] genotypes as confirmed by the RCWG. Furthermore, we detected G21P[29] rotaviruses in fecal specimens collected from healthy calves in Hokkaido, Japan during the period from 1997 to 1998. These findings suggest that novel G21P[29] rotaviruses have been widely prevalent among cattle for over 10 years in Japan.

First detection of G12 rotaviruses in newborns with neonatal rotavirus infection at all India Institute of Medical Sciences, New Delhi, India

Rotavirus genotype G12 strains were detected for the first time among newborns with asymptomatic rotavirus infection (74% of 39 rotavirus strains isolated from the infected infants were genotype G12) in the nursery of the All India Institute of Medical Sciences during a period from 2005 to 2006. Sequence analysis of the VP7 genes from these neonatal strains indicated a high level of homology to other G12 strains reported worldwide, suggesting the recent emergence of these strains in humans. Such nosocomial infections of newborns represent a potential source of introduction of novel rotavirus serotypes into the community.

Relationships among porcine and human P[6] rotaviruses: Evidence that the different human P[6] lineages have originated from multiple interspecies transmission events

Porcine rotavirus strains (PoRVs) bearing human-like VP4 P[6] gene alleles were identified. Genetic characterization with either PCR genotyping or sequence analysis allowed to determine the VP7 specificity of the PoRVs as G3, G4, G5 and G9, and the VP6 as genogroup I, that is predictive of a subgroup I specificity. Sequence analysis of the VP8* trypsin-cleavage product of VP4 allowed PoRVs to be characterized further into genetic lineages within the P[6] genotype. Unexpectedly, the strains displayed significantly higher similarity (up to 94.6% and 92.5% at aa and nt level, respectively) to human M37-like P[6] strains (lineage I), serologically classifiable as P2A, or to the atypical Hungarian P[6] human strains (HRVs), designated as lineage V (up to 97.0% aa and 96.1% nt), than to the porcine P[6] strain Gottfried, lineage II (<85.1% aa and 82.2 nt), which is serologically classified as P2B. Interestingly, no P[6] PoRV resembling the original prototype porcine strain, Gottfried, was detected, while Japanase P[6] PoRV clustered with the atypical Japanase G1 human strain AU19. By analysis of the 10th and 11th genome segments, all the strains revealed a NSP4B genogroup (Wa-like) and a NSP5/6 gene of porcine origin. These findings strongly suggest interspecies transmission of rotavirus strains and/or genes, and may indicate the occurrence of at least 3 separate rotavirus transmission events between pigs and humans, providing convincing evidence that evolution of human rotaviruses is tightly intermingled with the evolution of animal rotaviruses.

Porcine rotavirus strain Gottfried-based human rotavirus candidate vaccines: Construction and characterization

Rotavirus gastroenteritis remains the leading cause of severe diarrheal disease in infants and young children worldwide, and thus, a safe and effective rotavirus vaccine is urgently needed in both developing and developed countries. Various candidate rotavirus vaccines that were developed by us and others have been or are being evaluated in different populations in various parts of the world. We have recently confirmed that a porcine rotavirus Gottfried strain bears a P (VP4) serotype (P2B[6]) closely related to human rotavirus P serotype 2A[6] which is of epidemiologic importance in some regions of the world. Based on the modified Jennerian approach to immunization, we have constructed 11 Gottfried-based single VP7 or VP4 gene substitution reassortant vaccine candidates which could provide: (i) an attenuation phenotype of a porcine rotavirus in humans; and (ii) antigenic coverage for G serotypes 1-6 and 8-10 and P serotype 1A[8], 1B[4] and 2A[6]. In addition, following immunization of guinea pigs with Gottfried VP4, we found low but consistent levels of neutralizing antibodies to VP4 with P1A[8] or P1B[4] specificity, both of which are of global epidemiologic importance. Thus, porcine-based VP7 reassortant rotavirus vaccines may provide an advantage over rhesus- or bovine-based VP7 reassortant vaccines since the VP4s of the latter vaccines do not evoke antibodies capable of neutralizing the viruses bearing P1A[8], P1B[4] or P2A[6] VP4.

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

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.