Identification of human T-cell epitopes on the S4 subunit of pertussis toxin

Abstract

Ten adult humans were vaccinated with the Japanese acellular pertussis vaccine JNIH-3, containing detoxified pertussis toxin (PT), formaldehyde, and filamentous hemagglutinin. The vaccination induced a specific antibody response to PT and filamentous hemagglutinin, and a Western blot (immunoblot) analysis of the antibody response to PT revealed antibodies to PT subunits Si, S2, S3, S4, and S5. The response of peripheral lymphocytes to PT was assessed in an in vitro proliferation assay. A proliferative response to detoxified PT and PT dimers S2-S4 and S3-S4 was found, and it was further demonstrated that the proliferative response to detoxified PT and dimer S2-S4 was mediated by T cells of the CD4+ phenotype. The specificity of the proliferative response to subunit S4 was analyzed with a range of synthetic peptides synthesized on the basis of the primary sequence of subunit S4. The proliferative response to the peptides revealed two major and one minor T-cell epitope located in the NH2-terminal end of subunit S4. Pertussis toxin (PT) is considered one of the main virulence factors produced by Bordetella pertussis (52). Active or passive immunization with PT is protective in humans against disease and in animal models against lethal infection with virulent B. pertussis (1, 33, 44). Toxoided forms of PT are the principal components of acellular pertussis vaccines currently in use or under development (41). PT, which is composed of five subunits, termed S1 through S5, exhibits

Identification of murine T-cell epitopes on the S4 subunit of pertussis toxin

“…It was found that the peptides corresponding to the T-cell epitopes identified following immunization with the B oligomer were able to induce in vitro proliferative responses to PT components containing subunit S4. One of the murine T-cell epitopes identified in the present study corresponded to one of the major human T-cell epitopes identified in an earlier study (35). These results raise the possibility of using mice as a model for development of a synthetic immunogen based on defined T-and B-cell epitopes from PT.…”

“…No proliferative responses to the 12-residue peptides were found. In a previous study, PT-immune human peripheral lymphocytes were likewise stimulated in vitro with the 12-residue peptides, and no proliferative responses were found (35). The lack of responses to the 12-residue peptides is probably due to the fact that 12 amino acids in some cases may be too few to make up a T-cell epitope (19).…”

“…In vitro proliferative responses to PT components following peptide immunization. In a previous study, a major human T-cell epitope was identified in the S4 subunit sequence corresponding to peptide 4 (35). These results made it interesting to investigate the possibility of inducing in vitro recognition of different PT preparations following immunization with peptide 4.…”

“…The responses to T-cell epitopes were restricted by the major histocompatibility complex molecule, which confirmed that the cells proliferating in response to the peptides were T cells. In a previous study with PT-immune peripheral human lymphocytes (35), we showed that two major human T-cell epitopes were located around the sequences corresponding to peptide 1 and peptide 4 on subunit S4. Peptide 2 gave only low or no responses in this study (35).…”

“…In a recent * Corresponding author. study, we identified two major and one minor human T-cell epitopes on subunit S4 by using a range of synthetic peptides covering the primary sequence of S4 (35). In the present study, we used a similar approach to identify murine T-cell epitopes on S4.…”