Rotavirus A genotype P[4]G2: genetic diversity and reassortment events among strains circulating in Brazil between 2005 and 2009.

Group A rotaviruses (RV-A) are the leading cause of severe gastroenteritis in infants and young children worldwide. Due to the epidemiologic complexity of RV-A, especially in developing countries, it is important to determine which genotypes are circulating, principally after the introduction in March 2006 of the monovalent (P[8]G1) Rotarix® vaccine in Brazil by the National Immunization Program. In Phase III trials with Rotarix®, the prevalence of genotype P[4]G2 was extremely low, and therefore, evaluation of heterotypic immunization against this genotype was performed by meta-analysis statistics tests. Different studies have shown the re-emergence of genotype P[4]G2 in Brazil, since 2005, as well as in other countries, suggesting that it could be a continental phenomenon related to the temporal variability in the genotype's naturally occurring distribution. It is important to note that genotype P[4]G2 does not share VP4 or VP7 antigens with the vaccine strain. Therefore, we performed a phylogenetic analysis based on VP4 (VP8), VP7, VP6, and NSP4 genes of RV-A genotype P[4]G2 samples isolated from the five regions of Brazil between 2005 and 2009. This study revealed that different genetic variants of RV-A genotype P[4]G2 circulated in Brazil between 2005 and 2009, and that this variability is determined mainly by: occurrence of point mutations; reassortment events; and widespread global gene flow. The results obtained in this study are important to our understanding of the epidemiology and evolution of RV-A genotype P[4]G2 and demonstrate the importance of continuous monitoring and molecular characterization of RV-A strains circulating in human and animal populations.