Phylogenetic analysis of partial VP7 gene of the emerging human group A rotavirus G12 strains circulating in Tunisia

Purpose. Group A rotavirus (RVA) is the leading cause of severe gastroenteritis in children younger than 5 years. The most common human G-types are G1-4 and G9. G12 genotype is currently emerging worldwide, becoming the sixth most prevalent RVA G-genotype. In Tunisia, an emergence of G12 RVA strains was observed. To understand the evolution and origin of these Tunisian G12 strains, phylogenetic analyses were conducted. Methodology. A total of 1127 faecal samples were collected from Tunisian children under 5 years consulting for gastroenteritis between 2009 and 2014. Samples were screened by ELISA for the presence of RVA antigen. RVA-positive samples were used for the detection of G12 RVA strains by semi-nested RT-PCR. G12-positive specimens were subjected to VP4 genotyping reaction. PCR products of the G12-positive samples were sequenced and characterized by phylogenetic analysis of partial VP7 gene sequence. Results. Globally, 270 (24 %) stool specimens were RVA-positive. Fourteen presented the G12 genotype (5.2 %) and were found to be in combination with either the P[6] (50.0 %) or the P[8] (50.0 %) genotype. Phylogenetic analysis revealed that all characterized Tunisian G12 strains clustered in the modern G12 lineage III and appear to form three different subclusters. Conclusion. Thus, the Tunisian G12 strains may have originated from not a single, but at least three distinct ancestral G12 strains. Detailed molecular characterization of the entire genome of these strains remains essential to help determine the extent of genetic variation and the relatedness of Tunisian G12 RVA strains to G12 strains described worldwide.