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Fabiana Falugi, Chiara Zingaretti, Vittoria Pinto, Massimo Mariani, Laura Amodeo, Andrea G. O. Manetti, Sabrina Capo, James M. Musser, Graziella Orefici, Immaculada Margarit, John L. Telford, Guido Grandi, Marirosa Mora, Sequence Variation in Group A Streptococcus Pili and Association of Pilus Backbone Types with Lancefield T Serotypes, The Journal of Infectious Diseases, Volume 198, Issue 12, 15 December 2008, Pages 1834–1841, https://doi.org/10.1086/593176
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Abstract
Background. We previously reported that group A Streptococcus (GAS) pili are the T antigens described by Rebecca Lancefield. We also showed that these pili, constituted by backbone, ancillary 1, and ancillary 2 proteins, confer protection against GAS challenge in a mouse model.
Methods. We evaluated pilus distribution and conservation by sequencing the subunits of 39 new GAS isolates and used immunoblot analysis and agglutination assays to define the specificity of T sera to pilus subunits.
Results. GAS pili are encoded by 9 different islands within which backbone protein, ancillary protein 1, and ancillary protein 2 cluster in 15, 16, and 5 variants, respectively. Immunoblot and agglutination assays revealed that T type is determined by the backbone variant. This observation enabled us to set up a simple polymerase chain reaction assay to define the T type of GAS isolates.
Conclusions. We propose the use of a tee gene sequence typing, analogous to the emm gene typing, as a valuable molecular tool that could substitute for the serological T classification of GAS strains. From our sequence analysis and from recent epidemiological data, we estimate that a vaccine comprising a combination of 12 backbone variants would protect against >90% of currently circulating strains.
