Full genome characterization of human Rotavirus A strains isolated in Cameroon, 2010-2011: Diverse combinations of the G and P genes and lack of reassortment of the backbone genes

- Complete genome sequences of 31 human rotavirus species A strains, collected in Cameroon during 2010-11, were determined.
- 18 Wa-like strains expressed G1P[6], G12P[6], or G12P[8] neutralization antigens on the genotype 1 genomic configuration (I1-R1-C1-M1-A1-N1-T1-E1-H1).
- 13 DS-1-like strains expressed G2P[4], G2P[6], G3P[6], or G6P[6] neutralization antigens on the genotype 2 genomic configuration (I2-R2-C2-M2-A2-N2-T2-E2-H2).
- G6P[6] strain may represent a novel emerging genotype in west and central African countries.
- There was a remarkable lack of reassortment of backbone genes between genotype 1 and genotype 2 rotaviruses.

Over the past few years whole genome sequencing of rotaviruses has become a routine laboratory method in many strain surveillance studies. To study the molecular evolutionary pattern of representative Cameroonian Rotavirus A (RVA) strains, the semiconductor sequencing approach was used following random amplification of genomic RNA. In total, 31 RVA strains collected during 2010-2011 in three Cameroonian study sites located 120 to 1240 km from each other were sequenced and analyzed. Sequence analysis of the randomly selected representative strains showed that 18 RVAs were Wa-like, expressing G1P[6], G12P[6], or G12P[8] neutralization antigens on the genotype 1 genomic constellation (I1-R1-C1-M1-A1-N1-T1-E1-H1), whereas 13 other strains were DS-1-like, expressing G2P[4], G2P[6], G3P[6], and G6P[6] on the genotype 2 genomic constellation (I2-R2-C2-M2-A2-N2-T2-E2-H2). No inter-genogroup reassortment in the backbone genes was observed. Phylogenetic analysis of the Cameroonian G6P[6] strains indicated the separation of the strains identified in the Far North region (Maroua) and the Northwest region (Bamenda and Esu) into two branches that is consistent with multiple introductions of G6P[6] strains into this country. The present whole genome based molecular characterization study indicates that the emerging G6P[6] strain is fully heterotypic to Rotarix, the vaccine introduced during 2014 in childhood immunization program in Cameroon. Continuous strain monitoring is therefore needed in this area and elsewhere to see if G6s, besides genotype G1 to G4, G8, G9 and G12, may become a new, regionally important genotype in the post vaccine licensure era in Africa.