Nahary, L., Department of Molecular Microbiology and Biotechnology, George S. Wise Faculty of Life Sciences, Tel-Aviv University, Ramat Aviv 69978, Israel
Tamarkin, A., Department of Molecular Microbiology and Biotechnology, George S. Wise Faculty of Life Sciences, Tel-Aviv University, Ramat Aviv 69978, Israel
Kayam, N., Department of Molecular Microbiology and Biotechnology, George S. Wise Faculty of Life Sciences, Tel-Aviv University, Ramat Aviv 69978, Israel
Sela, S., Department of Food Science, Agricultural Research Organization, Volcani Center, Bet Dagan, Israel
Fry, L., Faculty of Medicine, Imperial College, St. Mary's Campus, London, United Kingdom, Department of Dermatology, St. Vincent's University Hospital, Dublin, Ireland, Faculty of Medicine, Imperial College, St. Mary's Campus, London W2 1PG, United Kingdom
Baker, B., Faculty of Medicine, Imperial College, St. Mary's Campus, London, United Kingdom
Powles, A., Faculty of Medicine, Imperial College, St. Mary's Campus, London, United Kingdom
Rogers, S., Department of Dermatology, St. Vincent's University Hospital, Dublin, Ireland
Benhar, I., Department of Molecular Microbiology and Biotechnology, George S. Wise Faculty of Life Sciences, Tel-Aviv University, Ramat Aviv 69978, Israel

In two-thirds of patients with guttate psoriasis (GP), there is good evidence that the eruption is triggered by a streptococcal throat infection. We attempted to determine if a specific epitope of the bacterial pathogen was associated with the humoral immune response in GP patients. Antibody titres against beta-haemolytic streptococci (BHS) extracts in sera from 14 patients with GP, 10 healthy controls and 10 chronic plaque psoriasis (CPP) patients were determined by ELISA. Antibody BHS reactivity was investigated using immunoblotting, followed by epitope mapping using peptide-phage display. The highest GP antibody titres (10,000-25,000) were found in sera that had a matching streptococcal isolate, three sera had high (5,000-12,500) and seven had raised titres (500-5,000). In the healthy control group, three had relatively high and seven lower titres. All the CPP sera had very low titres (<500). In the immunoblots, three major bands were recognised by all the GP sera, and, to a lesser extent, by four healthy controls. No GP-specific protein was identified. Epitope mapping identified 10 phage clones that specifically bound 2 or 3 GP sera, displaying five different peptide sequences that were not streptococcal in origin. These findings suggest that the antigen specificity of the humoral response to BHS in GP does not differ from that of non-psoriatic individuals. © 2008 Springer-Verlag.