Vaccine candidates PhtD and PhtE of Streptococcus pneumoniae are adhesins that elicit functional antibodies in humans

► PhtD and PhtE of Streptococcus pneumoniae (Spn) are adhesins. ► PhtD and PhtE isogenic mutants were shown to have reduced adherence. ► Escherichia coli expressing either PhtD or PhtE show increased adherence. ► IgG Fab is a required to study the role of functional antibodies in Spn adherence. ► PhtD and PhtE elicit functional antibodies in adults.