Streptococcus pneumoniae is a human opportunistic pathogen responsible for morbidity and mortality worldwide. Pneumococcal surface protein, Choline-binding protein A (CbpA) plays a key biological role in nasopharyngeal colonization and modulating the immune response to pneumococci. We have analyzed the genetic diversity of cbpA in invasive isolates.
264 invasive S.pneumoniae isolates collected from 2010-2018, were sequenced on Illumina Platform. The CRL in-house bioinformatics pipeline was used to extract gene sequences, alignment and phylogeny analysis. Allelic variations of CbpA gene was analyzed by comparing the identity with a well-defined virulent strain of S. pneumoniae TIGR4.
Gene cbpA was identified in 261(99%) of the 264 genomes. The sequences were highly polymorphic at both nucleotide and amino acid levels. Similarity of cbpA gene ranged from 65 – 98%, while 80- 99% homology was observed at amino acid level. Amino acid residues with similar physicochemical properties aligned allowing the identification of broadly conserved CbpA domains.
Due to high polymorphism at the cbpA locus, analysis of this loci from different isolates highlights how sequence diversity correlates with structural variation. The conserved epitope regions of the CbpA protein fragments can be exploited to develop more efficacious serotype-independent vaccines.