As to the VP7 gene which is considered the most important in inducing serotype-specific neutralising antibodies [23], Malawian G8, G9 and G12 genes clustered into

lineages that contained rotavirus strains exclusively or almost exclusively IBET151 of human origin. This includes the G8 VP7 gene, which was previously suspected to be derived from bovine rotaviruses [14]. Furthermore, the observation that the G8 VP7 gene from the current study belonged to the same lineage (lineage II) as the G8 VP7 genes from strains detected in Malawi in the late 1990s and early 2000s suggests that strains with very similar G8 VP7 gene sequences have continuously circulated in Malawi. As to G9 and G12 VP7 sequences from Malawi, they belong to the most common, recently emerging lineages of human rotavirus origin. Thus, despite the diversity in circulating G types, Malawian

rotavirus VP7 sequences were not unusual when compared with strains from elsewhere bearing the same genotypes. As compared to P[8] and P[4], which are regarded as indigenous to human rotaviruses, the origin of P[6] is more diverse; yet the P[6] VP4 genes of current and previously detected Malawian strains AZD9291 in vivo belong to the same sublineage of lineage I, the most common human lineage. Although the VP8* portion of the VP4 protein contains much variability among different P types in the amino acid sequence (corresponding to the globular domain of the viral spike) [23], interpretation of these findings needs to be undertaken cautiously since our analysis was only based on the VP8* gene. As to the VP6 gene that codes for the middle-layer capsid protein, our study has demonstrated that the VP6 gene of Malawian strains belonged to either the I1 or the I2 genotype, the genotypes common to

human rotaviruses of the Wa genogroup and the DS-1 genogroup, respectively [12]. Similarly, as to the NSP4 gene that codes for an enterotoxin, the NSP4 gene of Malawian strains belonged to genotype new E1 or E2 which are common to human rotavirus strains [12]. Furthermore, RNA–RNA hybridization showed that all Malawian rotavirus strains that had a long RNA pattern belonged to the Wa genogroup and that strains which had a short RNA pattern belonged to the DS-1 genogroup. Thus, while there was great diversity in the genes that code for the outer capsid proteins VP7 and VP4, rotavirus strains circulating in Malawi at the time of the vaccine trial were no more different than rotavirus strains circulating elsewhere in the world where Rotarix™ had previously demonstrated a higher level of efficacy. There is now increasing evidence that Rotarix™ offers protection against fully heterotypic strains with respect to VP7 and VP4 [33].