Survival curves for groups of 12 to 15 mice vaccinated with His6-PiuA (triangles), His6-PiaA (circles), PdB (diamonds), His6-PiuA combined with His6-PiaA (open squares) or alum-PBS alone (filled squares) after IP challenge with 106 CFU of S. pneumoniae. Symbols: ▪, alum; ▵, PiuA; ⋄, PdB; ○, PiaA; □, PiuA + PiaA.