Objective      To evaluate the ability of Streptococcus pneumoniae multivalent DNA vaccine with dominant pneumococcal surface protein A (PspA) clades against heterogeneous PspA from different Streptococcus pneumoniae.     Methods      PspA-Fam1-Clade1 and PspA-Fam2-Clade3 fragments

which were the clades of PspA-dominant family with high protective antibody titers and strong cross-reaction

were amplified using polymerase chain reaction (PCR) from their recombinant T vectors. Then the PCR products were cloned into a eukaryotic vector pcDNA3.1(+) for construction of the recombinant plasmids pcDNA3.1-Clade1 and pcDNA3.1-Clade3. Western blotting and reverse transcription-polymerase chain reaction (RT-PCR) were performed for detecting expression of the recombinant plasmids in mammalian cells BHK-21. Recombinant PspA multivalent DNA vaccines (pcDNA3.1-Clade1+pcDNA3.1-Clade3) were injected to immunize mice

and then the mice nasopharyngeal carriage of Streptococcus pneumoniae isolates from different PspA family clades were evaluated

and median survival time of the immunized mice by abdominal attack of Streptococcus pneumoniae isolates of different PspA family clades were calculated after 21 d.     Results      The PspA-dominant family clades recombinant multivalent DNA vaccines (pcDNA3.1-Clade1+pcDNA3.1-Clade3) were successfully constructed. Colony counts of 5 Streptococcus pneumoniae isolates in the groups of mice immunized with the DNA vaccines (pcDNA3.1-Clade1+pcDNA3.1-Clade3) had no significant difference (P0.01)

but were lower than those of the control groups of which mice were immunized with vectors and PBS

respectively. The median survival time of the groups of mice immunized with the DNA vaccines (pcDNA3.1-Clade1+pcDNA3.1-Clade3) had no significant difference (P0.01)

but were all significantly longer than those of the groups of mice immunized with vectors and PBS (P0.01).     Conclusion      PspA-dominant family clades (PspA-Fam1-Clade1 and PspA-Fam2-Clade3) can effectively solve the problem of heterogeneity of PspA

and the constructed Streptococcus pneumoniae DNA vaccine could be applied to target clinical infections by Streptococcus pneumoniae strains with PspA from different family.