Multiple-gene characterization of rotavirus strains: evidence of genetic linkage among the VP7-, VP4-, VP6-, and NSP4-encoding genes

Abstract

A total of 162 rotavirus strains detected between 1996 and 2006 among individuals with diarrhea in Rio de Janeiro, Brazil, were analyzed by multiple-gene genotyping. Characterization of strains was done by RT-PCR assay for amplification and typing of the VP7-, VP4-, VP6-, and NSP4-encoding genes. Overall, 139 (85.8%) strains belonged to the common group A rotavirus combinations: 67 (41.4%) belonged to genotype G1-P[8]-I1-E1; 18 (11.1%) were G2-P[4]-I2-E2; 11 (6.8%) were G3-P[8]-I1-E1; 12 (7.4%) were G4-P[8]-I1-E1; and 31 (19.1%) were G9-P[8]-I1-E1. Two samples presented mixed genotypes (G1 + G3-P[8]-I1-E1 and G1 + G9-P[9]-I1-E1) and rare combinations, such as G2-P[6]-I2-E2 and G9-P[6]-I2-E2, were detected in six (3.7%) strains. The results suggest a linkage among all four genes. Genotypes G1/G3/G4/G5/G9-P[8] were correlated strongly to I1-E1 genotypes and G2-P[4]/P[6] were correlated to I2-E2 genotypes. Unusual combinations of genes, such as G3-P[9]-I2-E2, G9-P[9]-I1-E2, and G3-P[9]-I3-E3, were observed in 15 (9.3%) strains. The characterization of multiple genes allows a more complete analysis of the rotavirus isolates and provides evidence of natural reassortment of strains.