Characterization of New Recombinant Noroviruses

Abstract

Noroviruses are important etiologic agents of acute gastroenteritis and show great genetic diversity. To characterize more fully previously detected strains that could not be assigned unequivocally to one particular genotype based on the RNA polymerase, we have sequenced a region in the capsid gene and, in some cases, in the junction between open reading frame 1 (ORF1) and ORF2. The results allowed us to identify several recombinant noroviruses: GGIIb viruses were detected for the first time in France in August 2000 and then spread through France and to Europe during the following winter. Here we present the characterization of three other probable GII recombinants which showed different phylogenetic positions depending on their ORF1 and ORF2 sequences. Analysis of the region located between ORF1 and ORF2 by a nucleotide identity window search showed a sudden shift in similarities. Moreover, recombination breakpoints were identified upstream and downstream of the beginning of ORF2 by using a statistical test, thus confirming the involvement of this region in recombination. Unlike GGIIb, the three recombinants described here do not seem to have diffused widely in the community: one was found in a waterborne outbreak, and the other two were found in sporadic cases. Recombination is important for the evolution of RNA viruses and has already been described for noroviruses. Our results suggest that recombination is not a rare phenomenon among noroviruses, but not all these presumed recombinants that formed during RNA replication are able to spread widely.

Molecular characterization of norovirus GII strains identified in Albania

“…During 2006, the NoV GIIb/GII.3 recombinant was the most prevalent NoV strain involved in outbreaks and investigated in Queensland, Australia . A similar recombinant strain was identified in France since 2000 as reported by Ambert-Balay et al [2005]. In this study, six NoV GII strains have been characterized as GII recombinant strains, all of them among those detected during 2002-2003. The molecular characterization is an important tool to better understand the genetic variability of NoVs.…”

“…The same classification was observed for the strains 96/2002 and 106/2002 after the analysis of ORF1 sequences; for these strains it can be hypothesized the recombination event because not supported from the sequencing of the capsid regions (Table I). The strain 229/2003 showed a sequence homology in ORF1 related closely to GII.b recombinant strain (accession number: AY 682549), in ORF2 the homology was closely related to GII.3 strain as identified in France in August 2000 [Ambert-Balay et al, 2005]. Five strains were classified as NoV GII.4 (Table I) (Fig.…”

Genetic Analysis of the Capsid Gene of Genotype GII.2 Noroviruses

“…Melksham-like strains are occasionally observed in molecular surveillance data from The Netherlands and Osaka City, and strains from Japan and The Netherlands could be consistently grouped in the same alignment, suggesting continuous widespread circulation and an ability to cause disease. The recombinant genomes with GII.2 capsids, however, occur sporadically and did not show evidence for evolution, suggesting that their circulation is limited (1,4,17). The finding that strains from such widely separated geographic regions were similar shows that evolution of GII.2 NoVs is a global phe- …”

Actualités sur les norovirus

“…Par ailleurs, une recombinaison entre des souches exprimant une ARN polymérase et une capside dérivées de souches parentales différentes a été décrite [16]. L'un de ces virus recombinants, le variant GGIIb, a été isolé pour la première fois au cours d'une épidémie d'origine hydrique dans le sud de la France en août 2000 [17]. Il a représenté jusqu'à 26 % des souches caractérisées en Europe et reste une de celles qui sont le plus fréquemment retrouvées lors d'épidémies et de cas sporadiques de gastroentérite.…”