Background
Group B streptococcus (GBS) is a major cause of bacteraemia and meningitis in neonates worldwide; and increasingly is associated with invasive disease in adults, especially the elderly. Currently, there are no licensed GBS vaccines, but two multi-polysaccharide vaccines and a multivalent adjuvanted protein vaccine in the pipeline. We investigated the distribution of proteins targeted by the protein vaccine in the disease-causing GBS in the UK.
Methods
Sterile site GBS isolates are submitted for typing to the Streptococcus Reference Laboratory and 814 GBS whole-genome sequences were analysed to determine serotype (GBS-SB), MLST (https://github.com/tseemann/mlst) and presence-absence of genes encoding four alpha proteins Alp1, Alp2/3, Rib and AlphaC (BLASTn) was investigated. Where metadata available, EOD or LOD disease stratification were undertaken.
Results
We identified that 100% of GBS genomes had genes encoding Alpha proteins, 67.8% (n=552) had rib, 39.8% (n=324) had alp1 and 28.1% (n=229) had alp2/3 genes. In isolates from adults, rib, alp1 and alp2/3 genes were present in 55.6% (120/216), 39.4%(85/216) and 53.7% (116/216), respectively. GBS from babies under 90 days old, was dominated by rib gene (75%, 345/458), which is associated with the dominant serotype III ST17 in EOD and LOD cases. 100% of ST17 had rib gene present, 100% of ST1 isolates had alp2/3 present as previously reported.
Conclusions
Genes encoding the Alp-family proteins targeted by the protein vaccine were readily identified in this dataset. This suggests that the protein vaccine has potential to provide broad coverage of current disease-causing GBS isolates in the UK population.