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Norovirus has emerged as an important viral agent of acute pediatric gastroenteritis, with a growing genetic diversity reported in the last decades. Histo-blood group antigens (HBGAs) present on the surface of enterocytes are susceptibility factors for norovirus infection and differ between populations which could affects the epidemiology and evolution of these viruses. This study investigated the frequency, incidence and genetic diversity of noroviruses in a cohort of rotavirus A vaccinated children in association to the host HBGA (Secretor/Lewis) genetic susceptibility profile. Norovirus genogroups I and II (GI/GII) were screened by RT-qPCR in 569 stool samples from 132 children followed-up from birth to 11 months of age during 2014--2018. Noroviruses were identified in 21.2% of children enrolled in this study, with a norovirus detection rate of 5.6% (32/569), in 17.1% and 4.7% of acute diarrheic episodes (ADE) and non-ADE, respectively. The norovirus incidence was 5.8 infections per 100 child-months. Partial nucleotide sequencing characterized six different norovirus genotypes, with GII.4 Sydney 2012 being detected in 50% associated with three different polymerase genotypes (GII·P31, GII·P16 and GII·P4 New Orleans 2009). FUT3 genotyping was yielded seven new mutations in this population. A significant association between symptomatic norovirus infection and secretor profile could be inferred., Competing Interests: Declaration of Competing Interest The authors declare that they have no conflict of interest., (Copyright © 2020 Elsevier B.V. All rights reserved.)

The Histo-blood group antigens (HBGA) are host genetic factors associated with susceptibility to rotavirus (RV) and human norovirus (HuNoV), the major etiological agents of viral acute gastroenteritis (AGE) worldwide. The FUT2 gene expressing the alpha-1, 2-L- fucosyltransferase enzyme is important for gut HBGA expression, and also provides a composition of the phenotypic profile achieved through mutations occurring in populations with different evolutionary histories; as such, it can be considered a genetic population marker. In this study, Lewis and secretor HBGA phenotyping was performed using 352 saliva samples collected from children between three months and five years old born in the Amazon (Brazil, Venezuela and English Guyana) presenting AGE or acute respiratory infection (ARI), the latter considered as control samples. The total of children phenotyped as secretors was 323, corresponding to 91.80%. From these, 207 (58.80%) had a Le (a + b+) profile. The HBGA profiles were equally found in children with AGE as well as with ARI. The rs1047781 of the FUT2 gene was not detected in DNA from saliva cells with a Le (a+b+) profile. However, mutations not yet described in the FUT2 gene were observed: missense 325A>T, 501C>T, 585C>T, 855A>T and missense substitutions 327C>T [S (Ser) > C (Cys)], 446 T>C [L(Leu) > P(Pro)], 723C>A [N(Asn) > K(Lys)], 724A>T [I(Ile) > F(Phe)], 736C>A [H(His) > N(Asn)]. The SNP distribution in the FUT2 gene of the analyzed samples was very similar to that described in Asian populations, including indigenous tribes., (Copyright © 2019 Elsevier B.V. All rights reserved.)