VP7 AND VP4 SEQUENCE ANALYSES OF ROTAVIRUS STRAINS FROM ITALIAN CHILDREN WITH VIREMIA AND ACUTE DIARRHOEA

Abstract

Background: Rotavirus has a high genetic variability. Point mutations, accumulating at a high rate, and genetic reassortment events have been well-documented. Viremia occurs commonly in children with acute rotavirus diarrhoea. However, information on genetic characterization of strains associated with systemic infection is poor. Objective: We evaluated prospectively children hospitalized for acute rotavirus diarrhoea and genotyped strains obtained from blood and stool samples. Nucleotide sequences within the VP4 ad VP7 genes of strains obtained from blood and stool specimens of the same patient were compared. Methods: Study subjects were 11 children admitted with acute rotavirus diarrhoea, documented by positive VP6 rotavirus antigen in stool specimen by immunochromatographic assay. RT-PCR of VP6, VP4 and VP7 gene segments was performed on faecal and blood samples. For sequence and phylogenetic analyses, amplicons were directly sequenced using specific primers for the VP7 and VP4 genes. Results: Seven children (63.3%) were viremic. Faecal strains were genotyped (five G1P[8] type, one G9P[8], one G1-G4P[8]). Only 3/7 blood strains were typeable (G1P[8], G4P8, and G1P[ND]). A discrepancy between faecal and blood VP7 amino acid sequences (Ser→Asp at position 94) was found in one child. Two amino acid substitutions (Ile→Val and Asn→Ser at position 106 and 113) in the VP4 sequences were demonstrated in another child. Complete correspondence was found in the third child. All the observed amino acid substitutions may be involved in rotavirus neutralization. Conclusions: During co-infection by multiple strains, a preferential extra-intestinal dissemination of some variants may occur, possibly due to differential viral characteristics.