Competent antigen-binding fragments (Fab) from secretory immunoglobulin a using streptococcus sanguis immunoglobulin a protease

Immunoglobulin A (IgA) protease, a family of bacterial enzymes, cleaves human IgA I at a single bond generating distinct Fab and Fc fragments. Purified secretory IgA with known specificity for Streptococcus mutans NCTC 10449 (serotype c) was hydrolyzed with IgA protease prepared from Streptococcus sanguis ATCC 10556. The isolated Fab fragments retained their initial activity by specifically binding to antigen and by deterring the sucrose-dependent adherence of S. mutans to glass indicating that the antigen-binding fragments behave as immunologically competent elements.