Cross-Reactive Antigens of Group A Streptococci

Abstract

Cross-reactive antigens are molecules on the group A streptococcus that mimic host molecules and during infection induce an immune response against host tissues. The identification of cross-reactive antigens in group A streptococci is important in the understanding of the pathogenesis of autoimmune sequelae, such as rheumatic fever and glomerulonephritis, which may occur following group A streptococcal infection. Monoclonal antibodies (MAbs) cross-reactive with group A streptococci and human heart tissues were produced from mice immunized with streptococcal cell wall and membrane components and from rheumatic carditis patients. The cross-reactive antibodies were divided into three major subsets based on their cross-reactivity with (i) myosin and other alpha-helical molecules, (ii) DNA, or (iii) N-acetylglucosamine. All three subsets were identified among MAbs from mice immunized with group A streptococcal components, but in the human, the predominant subset reacted with the N-acetyl-glucosamine epitope and myosin and related molecules. This chapter provides more evidence about the identification and analysis of the cross-reactive antigens of the group A streptococcus. It also discusses immune responses to N-acetyl-β-d-glucosamine, dominant epitope of group a polysaccharide, in the pathogenesis of rheumatic heart disease and sydenham chorea in acute rheumatic fever.