Molecular Characterization and Sequence Analysis of Pneumococcal Surface Protein A ( PspA ) from Invasive Streptococcus pneumoniae Isolated in Korea

ABSTRACT

To investigate the genetic variation within pspA from 17 clinical isolates of Streptococcus pneumoniae representing 12 capsular serotypes, we used specific PCR primers LSM12 and LSM2 derived from the DNA sequence of pspA of S. pneumoniae Rxl (type 2). We have found that all 17 isolates of S. pneumoniae have a pspA gene whose size ranges from 1.8 to 2.3 kb. RFLP analysis of the PCR-amplified pspA genes of the isolates exhibited distinct restriction patterns. Even within the same capsular type, the individual isolates of S. pneumoniae generally differed in PspA molecular masses and showed variabilities in the pspA gene locus. The nucleotide sequence of the pspA gene of S. pneumonaie KNIH1156 (type 19F) isolated from a blood specimen was determined. The sequence revealed an open reading frame of 1,827 bp nucleotides. Predicted size of the mature PspA was approximately 63 kDa. Deduced amino acid sequence of PspA of S. pneumonaie KNIH1156 revealed 57.0% identity with that of S. pneumonaie Rxl. Comparison of the nucleotide and amino acid sequences of PspA S. pneumoniae KNIH1156 (type 19F) with those of Rxl (type 2) showed considerable differences in the a-helical coiled-coil region of the two PspAs. These results suggest that the PspA of S. pneumoniae KNIH1156 has antigenic variations distinguished from those of Rxl strains.