The study on the immunogenicity of Streptococcus pneumoniae pneumolysin DNA vaccine in Rhesus macaques / 中华微生物学和免疫学杂志

ABSTRACT

Objective To study the immunogenicity of Streptococcus pneumoniae pneumolysin DNA vaccine in Rhesus macaques. Methods The deletion of the gene sequence encoding for the 11 amino acids at the carboxyl terminal of pneumolysin (PN) from its wild type gene (pn) by PCR resulted in a mu-tant pneumolysin gene (pnd). The wild type pn gene encoding PN and the mutant gene (pnd) encoding PND were cloned into pVAX1 vector respectively and then tested as Ppn and Ppnd DNA vaccines. The PN and PND proteins were purified from recombinant E. coli. Rhesus macaques were immunized by intramuscu-larly (i.m.) injection of Ppn or Ppnd DNA vaccine with electroporation (EP). Results Because of the deletion of the gene sequence encoding for the eleven amino acids at the carboxyl terminal of the PN from pn gene, the recombinant PND antigen lost its hemolytic activity while its antigenicity was remained. The spe-cific humoral immunity against pneumolysin was induced by injecting monkey with 500 μg DNA followed by EP. Boosting the Ppn or Ppnd DNA/EP primed animals with corresponding recombinant protein, PN or PND, evoked strong immune response at about 4 fold increase in the antibody titer. Conclusion Specific antibody responses were induced in the monkeys by DNA vaccination and electroporation. The immunogenic-ity of the DNA vaccines were significantly enhanced when PN or PND protein boost was applied 10 d after third DNA vaccination.