Abstract
The opa genes of the Gram negative bacterium Neisseria meningitidis encode Opacity-associated outer membrane proteins whose role is to promote adhesion to the human host tissue during colonisation and invasion. Each meningococcus contains 3–4 opa loci, each of which may be occupied by one of a large number of alleles. We analysed the Opa repertoire structure in a large, well-characterised collection of asymptomatically carried meningococci. Our data show an association between Opa repertoire and meningococcal lineages similar to that observed previously for meningococci isolated from cases of invasive disease. Furthermore, these Opa repertoires exhibit discrete, non-overlapping structure at a population level, and yet low within-repertoire diversity. These data are consistent with the predictions of a mathematical model of strong immune selection upon a system where identical alleles may occupy different loci.
Highlights
The Opacity (Opa) proteins of the bacterial pathogen Neisseria meningitidis mediate adhesion to and invasion of the human nasopharyngeal epithelium [1] via interaction with cell surface saccharides [2] and members of the carcinoembryonic antigen cell adhesion molecule (CEACAM) family of proteins [3,4]
Association between Opa repertoire and clonal complex The four known opa loci were analysed in the 216 meningococcal isolates from a carried population sample from the Czech Republic: a total of 864 loci
We found that the Opa repertoires were specific to individual meningococcal genotypes, similar to that observed in isolates from cases of invasive disease
Summary
The Opacity (Opa) proteins of the bacterial pathogen Neisseria meningitidis mediate adhesion to and invasion of the human nasopharyngeal epithelium [1] via interaction with cell surface saccharides [2] and members of the carcinoembryonic antigen cell adhesion molecule (CEACAM) family of proteins [3,4]. The opa gene repertoire comprises 3–4 loci per meningococcus (opaA, opaB, opaD and opaJ) [5,6,7,8]. These are constitutively transcribed and their expression is controlled by stochastic changes in a phase variable, pentameric repeat tract within the reading frame of the genes [9]. Opa proteins are highly diverse [8,10] with the majority of sequence changes localised in three regions which correspond to surface exposed loops in the proposed protein structure. Diversity is generated by gene conversion, mosaicism and modular exchange of variable regions, with the consequence that different opa loci in the same meningococcus may encode identical, similar or diverse HV regions [14,15]
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