Molecular analysis of the NSP4 and VP6 genes of rotavirus strains recovered from hospitalized children in Rio de Janeiro, Brazil

Group A rotaviruses are the main cause of acute gastroenteritis in children throughout the world. The two outer capsid proteins, VP4 and VP7, define the P and G genotypes, respectively. Rotaviruses with P[8]G1, P[4]G2, P[8]G3 and P[8]G4 genotypes are predominant in infecting humans and the G9 genotype is emerging in most continents as the fifth most common G type worldwide. The inner capsid protein VP6 is responsible for subgroup (SG) specificities, allowing classification of rotaviruses into SG I, SG II, SG I+II and SG non-I-non-II. The non-structural protein 4 (NSP4) encoded by segment 10 has a role in viral morphogenesis and five genetic groups have been described, NSP4 genotypes A–E. The aim of this investigation was to characterize the NSP4 and VP6 genes of rotavirus strains recovered from hospitalized children. Thirty rotavirus strains were submitted to RT-PCR followed by sequencing and phylogenetic analysis. Among the different G and P genotype combinations, two distinct genetic groups could be recognized for the NSP4 gene. Twenty-eight clustered with NSP4 genotype B. The two P[4]G2 strains fell into NSP4 genotype A and clustered distinctly, with a 100 % bootstrap value. The strains distinguished within a group were closely related to each other at the nucleotide and amino acid levels. A phylogenetic tree was constructed for the VP6 gene including the human strains RMC100, E210, Wa, US1205 and 1076, and the animal strains Gott, NCDV, SA-11, FI-14 and EW. This is the first report on Brazilian rotavirus strains describing NSP4 genotype A strains associated with VP6 SG I, and NSP4 genotype B strains associated with VP6 SG II.