Apr 2, 2014

Phase variation mediates reductions in expression of surface proteins during persistent meningococcal carriage

Infection and Immunity
Mohamed AlamroChristopher D Bayliss

Abstract

Asymptomatic and persistent colonization of the upper respiratory tract by Neisseria meningitidis occurs despite elicitation of adaptive immune responses against surface antigens. A putative mechanism for facilitating host persistence of this bacterial commensal and pathogen is alterations in expression of surface antigens by simple sequence repeat (SSR)-mediated phase variation. We investigated how often phase variation occurs during persistent carriage by analyzing the SSRs of eight loci in multiple isolates from 21 carriers representative of 1 to 6 months carriage. Alterations in repeat number were detected by a GeneScan analysis and occurred at 0.06 mutations/gene/month of carriage. The expression states were determined by Western blotting and two genes, fetA and nadA, exhibited trends toward low expression states. A critical finding from our unique examination of combinatorial expression states, "phasotypes," was for significant reductions in expression of multiple phase-variable surface proteins during persistent carriage of some strains. The immune responses in these carriers were examined by measuring variant-specific PorA IgG antibodies, capsular group Y IgG antibodies and serum bactericidal activity in concomitant ser...Continue Reading

Mentioned in this Paper

Short Tandem Repeat
Immune Response
Neisseria meningitidis
Pathogenic Organism
Western Blotting
Entire Upper Respiratory Tract (Body Structure)
Upper Respiratory Tract
Reverse Transcriptase Polymerase Chain Reaction
Bactericidal Activity
Western Blot

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