Whole genome analysis of rotavirus strains circulating in Benin before vaccine introduction, 2016-2018

Species A rotaviruses (RVA) still play a major role in causing acute diarrhea in children under five years old worldwide. Currently, an 11-gene classification system is used to designate the full genotypic constellations of circulating strains. Viral proteins and non-structural proteins in the order VP7-VP4-VP6-VP1-VP2-VP3-NSP1-NSP2-NSP3-NSP4-NSP5/6 are represented by the genotypes Gx-P [x]-Ix-Rx-Cx-Mx-Ax-Nx-Tx-Ex-Hx, respectively. In Benin, ROTAVAC (R) vaccine was introduced into the Expanded Programme on Immunization in December 2019. To monitor circulating RVA strains for changes that may affect vaccine performance, in-depth analysis of strains prior to vaccine introduction are needed. Here we report, the whole-gene characterization (11 ORFs) for 72 randomly selected RVA strains of common and unusual genotypes collected in Benin from the 2016 to 2018 seasons. The sequenced strains were 15 GIP [8], 20 G2P [4], 5 G9P [8], 14 G12P [8], 9 G3P [6], 2 GIP [6], 3 G2P [6], 2 G9P[4], 1 G12P [6], and 1 G1G9P [8]/P [4]. The study strains exhibited two genetic constellations designed as Wa-like G1/G9/G12-P [6]/P [8]-I1-R1-C1-M1-A1-N1-T1-E1-H1 and DS-1-like G2/G3/G12-P [4]/P [6]- I2-R2-C2-M2-A2-N2-T2-E2-H2. Genotype G9P[4] strains possessed a DS-1-like genetic constellation with an E6 NSP4 gene, G9-P[4]-12-R2-C2-M2-A2-N2-T2-E6-H2. The mixed genotype showed both Wa-like and DS-1-like profiles with a T6 NSP3 gene Gl/G9P [8]/[4]-I1/12-R1/R2-C1/C2-M1/M2-A1/A2-N1/N2-T1/T6-E1/E6-H1/ H2. At the allelic level, the analysis of the Benin strains, reference strains (with known alleles), vaccine strains (with known alleles) identified 2-13 and 1-17 alleles for DS-1-like and Wa-like strains, respectively. Most of the study strains clustered into previously defined alleles, but we defined 3 new alleles for the VP7 (G3 = 1 new allele and G12 = 2 new alleles) and VP4 (P[4] = 1 new allele and P[6] = 2 new alleles) genes which formed the basis of the VP7 and VP4 gene clusters, respectively. For the remaining 9 genes, 0-6 new alleles were identified for both Wa-like and DS-1-like strains. This analysis of whole genome sequences of RVA strains circulating in Benin described genetic point mutations and reassortment events as well as novel alleles. Further detailed studies on these new alleles are needed and these data can also provide a baseline for studies on RVA in the post-vaccination period.