title: Streptococcus pneumoniae serotype 9A isolates contain diverse mutations to wcjE that result in variable expression of serotype 9V-specific epitope.
abstract: BACKGROUND
  Streptococcus pneumoniae is a significant pathogen capable of expressing protective and antigenically diverse capsules. To better understand the molecular basis of capsular antigenic diversity, we investigated the hypothetical serological role of wcjE, which encodes a capsule O-acetyltransferase, in the vaccine-targeted serotype 9V and related serotype 9A.
  
  
  METHODS
  We inactivated wcjE by recombination in a serotype 9V strain and determined wcjE sequences of 11 serotype 9A clinical isolates. We determined the antigenic phenotypes of these pneumococcal strains with serogroup 9-specific antibodies and flow cytometry.
  
  
  RESULTS
  Inactivation of wcjE in a serotype 9V strain resulted in expression of the 9A phenotype. Each serotype 9A clinical isolate contained a distinct mutation to wcjE. Flow cytometry showed that some 9A isolates (herein named 9Aα) expressed trace amounts of 9V-specific epitopes whereas others (named 9Aβ) did not express any. Recombination with 9Aα wcjE alleles into a 9Aβ strain conferred partial expression of 9V-specific epitopes.
  
  
  CONCLUSIONS
  Each serotype 9A strain independently arose from a serotype 9V strain. Furthermore, clinical isolates identified as 9A can contain mutations to wcjE that are either partially functional or completely nonfunctional, demonstrating a previously unidentified antigenic heterogeneity of serotype 9A isolates.
authors: Department of Microbiology, University of Alabama at Birmingham, AL, USA.
authors: Juan J
authors: JJ
authors: Calix
authors: Melissa B
authors: MB
authors: Oliver
authors: Logan K
authors: LK
authors: Sherwood
authors: Bernard W
authors: BW
authors: Beall
authors: Susan K
authors: SK
authors: Hollingshead
authors: Moon H
authors: MH
authors: Nahm
mesh_terms: D000123:Acetyltransferases / Q000235:genetics*; D016667:Bacterial Capsules / Q000378:metabolism; D001483:Base Sequence; D004269:DNA, Bacterial; D018604:Epitope Mapping; D005798:Genes, Bacterial; D008969:Molecular Sequence Data; D009154:Mutation; D016133:Polymerase Chain Reaction; D017422:Sequence Analysis, DNA; D012703:Serotyping; D013296:Streptococcus pneumoniae / Q000145:classification / Q000201:enzymology / Q000235:genetics*
chemical_list: D004269:DNA, Bacterial; D000123:Acetyltransferases