The gut microbiome and rotavirus vaccine immunogenicity in rural Zimbabwean infants

Background: Oral rotavirus vaccine (RVV) immunogenicity is considerably lower in low- versus high-income populations; however, the mechanisms underlying this remain unclear. Previous evidence suggests that the gut microbiota may contribute to differences in oral vaccine efficacy. Methods: We performed whole metagenome shotgun sequencing on stool samples and measured anti-rotavirus immunoglobulin A in plasma samples from a subset of infants enrolled in a cluster randomized 2x2 factorial trial of improved water, sanitation and hygiene and infant feeding in rural Zimbabwe (SHINE trial: NCT01824940). We examined taxonomic and functional microbiome composition using random forest models, differential abundance testing and regression analyses to explored associations with RVV immunogenicity. Results: Among 158 infants with stool samples and anti-rotavirus IgA titres, 34 were RVV seroconverters. The median age at stool collection was 43 days. The infant microbiome was dominated by Bifidobacterium longum. The gut microbiome differed significantly between early ([≤]42 days) and later samples (>42 days) however, we observed no meaningful differences in alpha diversity, beta diversity, species composition or functional metagenomic composition by RVV seroconversion status. Bacteroides thetaiotaomicron was the only species associated with anti-rotavirus IgA titre. Random forest models poorly classified seroconversion status by both composition and functional microbiome variables. Conclusions: RVV immunogenicity is low in this rural Zimbabwean setting, however it is not explained by the composition or function of the early-life gut microbiome. Further research is warranted to examine the mechanisms of poor oral RVV efficacy in low-income countries.