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Abstract: Background: Noroviruses (NoVs) are one of the major causal agents of acute gastroenteritis among different age groups. Some of the recent studies reveal that NoV genome is highly prone to mutation and recombination which often leads to emergence of new strains. Objectives: To explore the genetic diversity of human Caliciviruses (HuCVs) among diarrhoeic children in Kolkata. Study design: The HuCVs were detected by reverse transcription-polymerase chain reaction (RT-PCR) of the partial RNA dependent RNA polymerase gene (RdRp) and capsid gene and confirmed by sequencing. The sequences were analyzed and the recombination point was detected. Results: Faecal specimens of children (n =111) visiting outpatient department of Dr B. C. Roy Memorial Hospital for Children with acute gastroenteritis were studied: 22 cases were HuCV positive with 21 NoVs. Of these, 12 NoV cases (54.5%) were GII.4 and six cases showed 99% identity with the new variant Japanese strain Hu/NoV/GII.4/OC07138/JP. Three novel NoV GII inter-genotype recombinant strains V1628/IND, V1656/IND and V1737/IND were also detected. The RdRp region of V1628 showed 96% identity with Pont de Roide 673/FRN whereas capsid region resembled GII.7/Osaka F140/JPN strain (98%); the strain V1656 showed 98% identity with RdRp region of GII.4/Monastir 375/TUN but capsid region resembled GII.8/Leverkusen 267/DE (91%); the strain V1737 showed 88% identity with RdRp of GII.5/Minato 6/N1/6/JPN whereas capsid region resembled the GII.12/Gifu 96/JPN (93%). During characterization of Caliciviruses two strains of NoV GII.b and one strain of each NoV GI.1/V1622/06/IND, GI.3/V1707/07/IND, GII.3/V1668/IND, GII.16/V1729/IND, Sapovirus GII.1/V1716/IND were also detected. Conclusions: The emergence of new variant of GII.4/2007, three novel NoV GII inter-genotype recombinant strains and various other NoVs, indicates the remarkable genetic diversity of the HuCVs as diarrhoeagenic viruses circulating in Kolkata, India. [Copyright &y& Elsevier]

Abstract: Mutation and recombination are recognized as important driving forces of evolution among RNA viruses. An intergenogroup recombinant norovirus strain [Hu/Kol/NLV/L8775/AB290150/2006/India] was detected in the faecal specimen of a 17 year old male, who had suffered from acute watery diarrhea and severe dehydration. Sequence analysis confirmed that this novel recombinant strain had a polymerase gene fragment that closely resembled a Norovirus (NoV) genogroup-I genotype-3 virus (HuCV/NLV/GI.3/VA98115/AY038598/1998/USA) and a capsid gene resembling NoV genogroup-II genotype-4 virus (NoV/Hu/GII.4/Terneuzen70/EF126964/2006/NL). The crossing over and recombination was observed at nucleotide (nt) 790 of NoV GI VA98115 strain and nt808 of NoV GII Terneuzen70 strain. In both parent strains conserved nucleotide sequence and hairpin structure (DNA secondary structure) were reported at the junction point of ORF1 and ORF2, exhibiting the mechanism of recombination in these viruses. Thus this novel recombinant NoV is another step in evolution among NoVs, indicating that constant surveillance is important to successfully monitor emergence of these strains. [Copyright &y& Elsevier]