The presently disclosed subject matter provides therapeutic methods and compositions for the treatment of bacterial infections caused by Streptococcus pneumoniae. In particular, methods are provided for increasing protective antibody levels induced by pneumococcal polysaccharide vaccines in a subject in need thereof comprising administering to the subject an effective amount of an agent that inhibits the interaction between a PD-1 ligand and a PD-1 polypeptide. Immunogenic compositions are also provided comprising one or more pneumococcal polysaccharide antigens and an agent that inhibits the interaction between a PD-1 ligand and a PD-1 polypeptide.