VP8*P[8] lineages of group A rotaviruses circulating over 20 years in Brazil: proposal of six different sub-lineages for P[8]-3 clade.

Group A rotaviruses (RVA) is the most important cause of severe gastroenteritis among children worldwide. Vaccination is considered the best alternative among public health measures to reduce and prevent the global burden caused by RVA infections. Rotarix™, a monovalent vaccine based on a human strain with a G1P[8]-1 specificity, was introduced in the National Brazilian Immunization Programs (NIP) in March, 2006. RVA P[8] is the most prevalent P genotype worldwide and four distinct phylogenetic lineages: P[8]-1, -2, -3, and -4 have been described. In the current study phylogenetic analysis of the VP8(*) gene of 135 RVA P[8] Brazilian strains, in combination with G1, G3, G5 or G9 VP7 genotype, collected from 1986 to 2011 were carried out for a better understanding of the evolution of this viral genotype in Brazil. Lineages P[8]-1, P[8]-2, and P[8]-3 were observed circulating in Brazil. In 2001 these three P[8] lineages co-circulated simultaneously and this is the first report in South America to date. Considering the P[8] lineage and the G genotype, all G3 strains were related to lineage P[8]-3, whereas the G9 strains were related to P[8]-2 and P[8]-3 and G1 and G5 were related to P[8]-1, P[8]-2, and P[8]-3. In addition, the phylogenetic analysis based on estimate of genetic distances between P[8]-3 strains and the definition of a 1.5% cutoff value (with relevant statistical support) it was possible to propose a new classification for the P[8]-3 lineage into six different sub-lineages: P[8]-3.1 to P[8]-3.6. These findings reinforce the notion of the existence of constraints within specific RVA strains populations. The results obtained in this study reinforce the importance of a continuous RVA surveillance of circulating strains in order to predict the possible variants that will circulate in a country, assess the effects of vaccination on RVA circulating strains, and ultimately help in the design, challenges, and prospects of RVA vaccines.