Publications

Abstract

Host survival depends on an effective immune system and pathogen survival on the effectiveness of immune evasion mechanisms. Staphylococcus aureus utilizes a number of molecules to modulate host immunity including the SSL family of which SSL7 binds IgA and inhibits FcalphaRI mediated function. Other gram positive bacterial pathogens produce IgA binding proteins which, like SSL7, also bind the Fc at the CH2/CH3 interface (the junction between constant domains 2 and 3 of the heavy chain). The opposing activities of the host FcalphaRI:IgA receptor ligand pair and the pathogen decoy proteins select for host and pathogen variants which exert stronger protection or evasion respectively. Curiously mouse, but not rat IgA, contains a putative N-linked glycosylation site in the centre of this host receptor and pathogen binding site. Here we demonstrate this site is glycosylated and the effect of amino acid changes and glycosylation of the CH2/CH3 interface inhibits interaction with pathogen IgA while maintaining binding of pIgR, essential to the biosynthesis and transport of SIgA.