Identification of human antigenic epitopes in an alanine-rich repeating region using sera from hu-PBL-SCID mice immunized with a surface protein antigen of Streptococcus mutans.

A 190-kDa surface protein antigen (PAc) of Streptococcus mutans is considered to play an important role in dental caries. To identify antigenic epitopes of the PAc in humans, we immunized severe combined immunodeficient (SCID) mice with recombinant PAc that was transplanted with human peripheral blood mononuclear cells (PBMC). The reactivities of the sera from the immunized hu-PBL-SCID mice to the recombinant PAc and 24 19-mer synthetic peptides covering the alanine-rich repeating region (A-region) presented in the PAc molecule were then examined. The results showed that the immunized mice produced a significant recombinant PAc-specific human antibody, and among 24 19-mer peptides, 6 19-mer peptides showed a strong reaction with the antibodies. In addition, 4 19-mer peptides containing human antigenic epitope in a donor were identified with enzyme-linked immunosorbent assay (ELISA) inhibition assays using the recombinant PAc protein. In this study, the SCID mouse was useful in identifying human antigenic epitopes.

Immunogenicity of peptides coupled with multiple T-cell epitopes of a surface protein antigen of Streptococcus mutans.

A surface protein antigen (PAc) of Streptococcus mutans, in particular the A-region of the molecule, has been noted as a possible target of effective dental caries vaccine. We have previously shown that two peptides of 19 amino acids (residues 361-379, NAKATYEAALKQYEADLAA, and residues 301-319, ANAANEADYQAKLTAYQTE), which correspond to parts of the A-region, contain both T- and B-cell epitopes for the induction of cross-reacting antibodies to the PAc. In this study, for development of an appropriate antigen as a peptide vaccine for use in prophylactic dentistry, we analysed in detail the localization of the T- and B-cell epitopes of PAc(361-379) peptide and the T-cell epitope of PAc(301-319) peptide in B10 congenic mice. In four murine major histocompatibility complex (MHC) haplotypes (H-2f,d,a and k), PAc(361-377) peptide showed T- and B-cell epitopes forming a cluster. It was found that the antibody which was induced by the immunization with the peptide was strongly cross-reactive with recombinant (r)PAc. Meanwhile, PAc(305-318) peptide, recognised by five strains of mice of different MHC haplotypes (H-2f,d,a,k and s), also bore multiple T-cell epitopes. PAc(361-377) peptide coupled to PAc(305-318) significantly elevated cross-reacting antibody levels compared to immunization with PAc(361-377) only in four H-2 haplotypes. Moreover, a peptide with PAc(305-318) coupled to the N-terminal region of PAc(361-377) produced significant cross-reacting antibody against rPAc, even in B10.S mice which had not responded to immunization with PAc(361-379) peptide. Therefore, it was suggested that coupling among the peptides forming a cluster might be effective in increasing immunogenicity. These results may provide us with a useful strategy for the design of peptide-based vaccines for S. mutans in the future.

[Isolation perfusion chemotherapy using cisplatin in malignant tumors of the extremities].

Since 1960 isolation perfusion chemotherapy has been performed as a preoperative procedure combined with surgery in 226 patients with malignant tumor of the extremities in our department. In this report we presented the result of isolation perfusion chemotherapy using cisplatin (CDDP) for 27 patients since 1983. The histologic classification of the malignant tumor was osteosarcoma in 17 patients, malignant fibrous histiocytoma (MFH) of bone in 8, and other tumor in 2. The extremity was perfused with CDDP (100 micrograms/ml) for 60 minutes. Of 27 patients, 11 were treated with hyperthermic isolation perfusion. The two-year survival rate of the 15 patients with osteosarcoma was 80%, and that of the 7 patients with MFH of bone 71%. The tumor was microscopically analyzed, and the ratio of necrotic to viable tumor cells was calculated. The degree of tumor necrosis was classified as excellent (greater than or equal to 95%), good (80-94%), fair (50-79%), and poor (less than 50%). Of 16 patients, 7 were excellent, 5 good, 3 fair and 1 poor. We concluded that isolation perfusion chemotherapy using CDDP is an effective procedure combined with surgery for malignant tumor of the extremities.