Abstract
Bacterial lipopolysaccharides (LPSs) have been shown to promote enteric viral infections. This study tested the hypothesis that elevated levels of bacterial LPS improve oral rotavirus vaccine replication in South African infants. Stool samples were collected from infants a week after rotavirus vaccination to identify vaccine virus shedders (n = 43) and non-shedders (n = 35). Quantitative real-time PCR was used to assay for selected LPS-rich bacteria, including Serratia marcescens, Pseudomonas aeruguinosa and Klebsiella pneumonia, and to measure the gene expression of bacterial LPS, host Toll-like Receptor 4 (TLR4) and Interleukin-8 (IL-8). The abundance of selected LPS-rich bacteria was significantly higher in vaccine shedders (median log 4.89 CFU/g, IQR 2.84) compared to non-shedders (median log 3.13 CFU/g, IQR 2.74), p = 0.006. The TLR4 and IL-8 gene expressions were increased four- and two-fold, respectively, in vaccine shedders versus non-shedders, but no difference was observed in the bacterial LPS expression, p = 0.09. A regression analysis indicated a significant association between the abundance of selected LPS-rich bacteria and vaccine virus shedding (Odds ratio 1.5, 95% CI = 1.10-1.89), p = 0.002. The findings suggest that harbouring higher counts of LPS-rich bacteria can increase the oral rotavirus vaccine take in infants.