Streptococcus pneumoniae serotype 9A isolates contain diverse mutations to wcjE that result in variable expression of serotype 9v-specific epitope

Academic Article


  • 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. © The Author 2011.
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    Digital Object Identifier (doi)

    Author List

  • Calix JJ; Oliver MB; Sherwood LK; Beall BW; Hollingshead SK; Nahm MH
  • Start Page

  • 1585
  • End Page

  • 1595
  • Volume

  • 204
  • Issue

  • 10