Polyhistidine triad protein D (PhtD) (PhtD)

Polyhistidine triad protein D (PhtD) is a highly conserved surface protein of Streptococcus pneumoniae that plays a vital role in the pathogen's survival and virulence. It belongs to the Pht family, characterized by multiple histidine triad (HxxHxH) motifs that bind divalent metal ions, specifically zinc, which is essential for bacterial metabolism and resistance to host-induced metal stress (Rioux et al., 2002, PubMed: 12165599). Beyond metal homeostasis, PhtD facilitates bacterial adherence to the respiratory epithelium and aids in immune evasion by binding to host complement factor H, thereby inhibiting the alternative complement pathway (Ogunniyi et al., 2009, PubMed: 19528208). Due to its presence across almost all pneumococcal serotypes, PhtD is a primary candidate for serotype-independent protein vaccines (Pancotto et al., 2013, PubMed: 23414371). Clinical trials have shown that PhtD-based vaccines are well-tolerated and capable of inducing robust antibody responses that enhance the opsonophagocytic killing of the bacteria (Hambidge et al., 2011, PubMed: 21502370). Research indicates that targeting PhtD can potentially reduce both invasive pneumococcal disease and mucosal colonization, addressing limitations of current polysaccharide-conjugate vaccines.

Other names

PhtDBVH-11Pneumococcal histidine triad protein DSP0361

Induction of protective humoral immunity, specifically opsonophagocytic antibodies that facilitate clearance of Streptococcus pneumoniae and prevent mucosal colonization.