title: Determining antibody-binding site of streptococcal pyrogenic exotoxin B to protect mice from group a streptococcus infection.
abstract: Streptococcal pyrogenic exotoxin B (SPE B), a cysteine protease, is an important virulence factor in group A streptococcal (GAS) infection. SPE B binds and cleaves antibody isotypes and further impairs the immune system by inhibiting complement activation. In this study, we examined the antibody-binding site of SPE B and used it to block SPE B actions during GAS infection. We constructed different segments of the spe B gene and induced them to express different recombinant fragments of SPE B. Using an enzyme-linked immunosorbent assay (ELISA), we found that residues 345-398 of the C-terminal domain of SPE B (rSPE B(345-398)), but not the N-terminal domain, was the major binding site for antibody isotypes. Using a competitive ELISA, we also found that rSPE B(345-398) bound to the Fc portion of IgG. The in vitro functional assays indicate that rSPE B(345-398) not only interfered with cleavage of antibody isotypes but also interfered with SPE B-induced inhibition of complement activation. Immunization of BALB/c mice using rSPE B(345-398) was able to induce production of a high titer of anti-rSPE B(345-398) antibodies and efficiently protected mice from GAS-induced death. These findings suggest that SPE B uses its C-terminal domain to bind the Fc portion of IgG and that immunization of mice with this binding domain (rSPE B(345-398)) could protect mice from GAS infection.
authors: Department of Biological Science and Technology, I-Shou University, Kaohsiung City, Taiwan.
authors: Nina
authors: N
authors: Tsao
authors: Miao-Hui
authors: MH
authors: Cheng
authors: Hsiu-Chen
authors: HC
authors: Yang
authors: Yu-Chieh
authors: YC
authors: Wang
authors: Yi-Ling
authors: YL
authors: Liu
authors: Chih-Feng
authors: CF
authors: Kuo
mesh_terms: D000818:Animals; D000907:Antibodies, Bacterial / Q000097:blood / Q000737:chemistry / Q000276:immunology*; D001426:Bacterial Proteins / Q000737:chemistry / Q000276:immunology* / Q000494:pharmacology; D001428:Bacterial Vaccines / Q000737:chemistry / Q000276:immunology / Q000494:pharmacology; D001665:Binding Sites; D003167:Complement Activation / Q000187:drug effects / Q000276:immunology; D005098:Exotoxins / Q000737:chemistry / Q000276:immunology* / Q000494:pharmacology; D006801:Humans; D007114:Immunization; D007141:Immunoglobulin Fc Fragments / Q000276:immunology; D008297:Male; D051379:Mice; D017434:Protein Structure, Tertiary; D011994:Recombinant Proteins / Q000737:chemistry / Q000276:immunology / Q000494:pharmacology; D013290:Streptococcal Infections / Q000517:prevention & control*; D013297:Streptococcus pyogenes / Q000276:immunology / Q000502:physiology*
chemical_list: D000907:Antibodies, Bacterial; D001426:Bacterial Proteins; D001428:Bacterial Vaccines; D005098:Exotoxins; D007141:Immunoglobulin Fc Fragments; D011994:Recombinant Proteins; C027951:erythrogenic toxin
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