Molecular characterisation of the NSP4 gene of group A human rotavirus G2P[4] strains circulating in São Paulo, Brazil, from 1994 and 2006 to 2010.

Jéssica Wildgrube Bertol,Maria Clara Duarte Fregolente,Thabata Alessandra Ramos Caruzo,Marco Aurélio Palazzi Sáfadi,Márcio José Da Silva,Maria Lucia Rácz,Maria Silvia Viccari Gatti,Veridiana Munford

doi:10.1590/0074-02760150199

Jéssica Wildgrube Bertol, Maria Clara Duarte Fregolente + Show 6 more

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https://doi.org/10.1590/0074-02760150199

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Abstract

Group A human rotaviruses (HuRVA) are causative agents of acute gastroenteritis. Six viral structural proteins (VPs) and six nonstructural proteins (NSPs) are produced in RV-infected cells. NSP4 is a diarrhoea-inducing viral enterotoxin and NSP4 gene analysis revealed at least 15 (E1-E15) genotypes. This study analysed the NSP4 genetic diversity of HuRVA G2P[4] strains collected in the state of São Paulo (SP) from 1994 and 2006-2010 using reverse transcription-polymerase chain reaction, sequencing and phylogenetic analysis. Forty (97.6%) G2P[4] strains displayed genotype E2; one strain (2.4%) displayed genotype E1. These results are consistent with the proposed linkage between VP4/VP7 (G2P[4]) and the NSP4 (E2) genotype of HuRVA. NSP4 phylogenetic analysis showed distinct clusters, with grouping of most strains by their genotype and collection year, and most strains from SP were clustered together with strains from other Brazilian states. A deduced amino acid sequence alignment for E2 showed many variations in the C-terminal region, including the VP4-binding domain. Considering the ability of NSP4 to generate host immunity, monitoring NSP4 variations, along with those in the VP4 or VP7 protein, is important for evaluating the circulation and pathogenesis of RV. Finally, the presence of one G2P[4]E1 strain reinforces the idea that new genotype combinations emerge through reassortment and independent segregation.

Highlights

Rotaviruses (RVs) are the most important etiological agents of severe acute gastroenteritis in children younger than five years of age (WHO 2013) and they cause an estimated 1.7 billion episodes of acute diarrhoea, leading to nearly 700,000 deaths worldwide annually (Liu et al 2012, Walker et al 2013)
NSP4 is a multifunctional glycoprotein involved in viral morphogenesis and pathogenesis (Ball et al 2005) that is important for the assembly of transiently enveloped double-layered particles (DLP) during RV replication (Taylor et al 1996)
The results indicated that 97.6% of these 41 strains were of the E2 genotype and that only one (2.4%) was of the E1 genotype

Summary

Introduction

Rotaviruses (RVs) are the most important etiological agents of severe acute gastroenteritis in children younger than five years of age (WHO 2013) and they cause an estimated 1.7 billion episodes of acute diarrhoea, leading to nearly 700,000 deaths worldwide annually (Liu et al 2012, Walker et al 2013). The nonenveloped virion is 100 nm in diameter and a triple-layered capsid surrounds the genome, which is composed of 11 segments of double-stranded RNA (dsRNA) These segments encode six viral structural proteins (VP1-4 and VP6-7) and six nonstructural proteins (NSP1-6) (Estes & Kapikian 2007, Greenberg & Estes 2009). The rate of G2P[4] detection has been decreasing since 2009 (Carvalho-Costa et al 2011, Oliveira et al 2012, Soares et al 2012) This genotype fluctuation may be due to a natural phenomenon of reemergence that occurs approximately every 10 years or may be related to the introduction of the Rotarix® vaccine or both (Gómez et al 2011). NSP4 promotes an increase in the intracellular calcium concentration, which results in chloride secretion into the intestinal lumen (Ball et al 1996), the disruption of tight junctions (Tian et al 1996) and, aqueous diarrhoea (Ball et al 1996)

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