Objective      To study the immunoprotective activity of PotD proteins from

Streptococcus pneumoniae

(

S.pn

) and its application possibility as a vaccine candidate.       Methods      After expression and purification of PotD protein

BALB/c mice were immunized with PotD protein to produce polyclonal antibody. The immunogenicity of PotD protein was assessed

and then further its effects on children were analyzed. The conservation of PotD gene in 8 different

S.pn

strains was tested by P

CR and sequencing. Using Western blot

the expression level and the conservation of PotD protein in 8 different

S.pn

strains was tested. Adherence inhibition experiments were used to analyze the immunogenicity of PotD protein.       Results      Recombinant PotD protein with high purity and high-titer anti-PotD antibody were successfully obtained. Anti-PotD antibody was also found in the sera from children under the age of 10 who were infected with

S.pn

. The PotD gene was highly conservative in the 8 different 

S.pn

strains. All of the 8 

S.pn

strains expressed the PotD protein. Adherence inhibition experiments showed that the recombinant PotD and anti-PotD antiserum had a significant inhibition effect on 

S.pn

adhesion to A549 cells.       Conclusion      PotD protein with high conservation and immunological activity can be prepared conveniently. It can significantly inhibit 

S.pn

adhesion to host cells and may be a good protein vaccine candidate.