DISTINCT IGG1 AND IGG3 SUBCLASS RESPONSES TO 2 STREPTOCOCCAL PROTEIN ANTIGENS IN MAN - ANALYSIS OF ANTIBODIES TO STREPTOLYSIN-O AND M-PROTEIN USING STANDARDIZED SUBCLASS-SPECIFIC ENZYME-LINKED IMMUNOSORBENT ASSAYS

The IgG subclass composition of antibodies to two streptococcal protei n antigens in sera following infection was analysed by enzyme-linked i mmunosorbent assays (ELISA). The assays were standardized using 5-iodo -4-hydroxy-nitrophenacetyl (NIP)-specific chimeric antibodies, to perm it quantitative comparisons between subclasses. Antibodies to streptol ysin O (SLO) were predominantly IgG1, with only minor contributions fr om the other subclasses. In contrast, antibodies to M protein were dis tributed between the IgG1 and IgG3 subclasses, and in approximately ha lf the sera IgG3 predominated. The ratio of IgG1:IgG3 was greater for SLO than for M protein in 22/23 sera. Little or no IgG4 antibody was d etected to either antigen. Functional affinities of the IgG1 and IgG3 antibodies, determined by inhibition ELISA, were comparable for the tw o antigens. The demonstration that two protein antigens encountered du ring streptococcal infection elicit antibody responses with markedly d ifferent subclass profiles has implications for IgG subclass regulatio n and vaccine development.