Evolution of human G4P[8] group A rotavirus strains circulating in Italy in 2013

Group A rotaviruses (RVA) are the leading cause of acute gastroenteritis in young (<5 years of age) children,causing up to 450.000 deaths worldwide, mostly in developing countries. VP7 (G-type) and VP4 (P-type)genotypes are the basis for the binary RVA classification. Although at least 27 G-types and 37 P-types ofrotavirus are presently known, most RVA infections in humans worldwide are associated with the fivemajor G/P combinations G1P[8], G2P[4], G3P[8], G4P[8] and G9P[8].During RVA gastroenteritis surveillance in Italy, a total of 1112 samples collected from children hospi-talized with acute gastroenteritis in 2013 were RVA positive and were genotyped following standardizedprotocols from the EuroRotaNet. Most strains analyzed belonged to the five major human genotypes.Among these common strains, 22 G4P[8] RVA strains from different Italian regions were subjected tonucleotide sequencing of their VP4, VP6, VP7 and NSP4 genes to investigate their evolution.The phylogenetic analysis showed that the Italian strains belonged to lineage G4-I for VP7 and tolineage P[8]-III for VP4, in line with the modern G4P[8] RVA strains detected in children worldwide. Thephylogenetic trees revealed high degrees of nucleotide identity between the RVA strains involved in thisstudy and G4P[8] strains detected previously in Europe, Asia and Africa, but also demonstrated at leastthree separate evolution clusters within the same lineage.Based on the amino acid sequences deduced for their hypervariable regions, both the VP7 and VP8*proteins