1. ¹Department of Infection, Immunity and Inflammation, University of Leicester, Leicester, UK
2. ²Department of Medical and Social Care Education, University of Leicester, Leicester, UK
3. ³Dermatology Centre, University of Manchester, Manchester, UK

Correspondence: Dr Richard D.R. Camp, Department of Infection, Immunity and Inflammation, University of Leicester, Medical Sciences Building, University Road, Leicester LE1 9HN, UK. E-mail: rdrc1@le.ac.uk

Received 10 July 2006; Revised 15 November 2006; Accepted 16 November 2006; Published online 8 March 2007.

Abstract

A pathogenic role for Streptococcus (S) pyogenes infections in chronic plaque psoriasis is suspected but poorly defined. We separated cellular and supernatant proteins from S pyogenes cultures by high-resolution two-dimensional gel electrophoresis, and used immunoblotting to demonstrate the diversity of serum or plasma IgGs that react with elements of the proteome of this bacterium. We have shown that a substantial proportion of IgG-reactive proteins from cultured S pyogenes are secreted. The total secreted protein fraction, including diverse IgG-binding elements, was subsequently used in an ELISA to measure blood titers of reactive IgG. This ELISA showed that blood samples from patients with chronic plaque psoriasis contained significantly higher titers of reactive IgG than samples from age- and sex-matched healthy controls (P=0.0009). In contrast, neither a standard assay measuring antistreptolysin O titers nor ELISAs measuring titers of IgG reactive with protein fractions from Staphylococcus aureus and Staphylococcus epidermidis, were able to distinguish between blood samples from the two groups. These findings justify the hypothesis that S pyogenes infections are more important in the pathogenesis of chronic plaque psoriasis than has previously been recognized, and indicate the need for further controlled therapeutic trials of antibacterial measures in this common skin disease.