IMMUNIZATION OF GUINEA-PIGS WITH RECOMBINANT TMPB ANTIGEN INDUCES PROTECTION AGAINST CHALLENGE INFECTION WITH TREPONEMA-PALLIDUM NICHOLS

Treponema pallidum-susceptible guinea pigs of strain C4D were immunized with recombinant T. pallidum antigens TmpA, TmpB, TmpC, and TmpA plus TmpB plus TmpC; with Escherichia coli membranes; or with adjuvant alone. Animals in groups of five received six immunizing injections, each of 100-mu-g of antigen incorporated in RIBI adjuvant. After the sixth immunization, all experimental and nonimmunized controls were intradermally challenged with 3 x 10(6) T. pallidum Nichols freshly extracted from infected rabbit testes. Although high titers of antitreponemal antibodies in the fluorescent-treponemal-antibody test or an enzyme-linked immunosorbent assay were evoked in all animals immunized with recombinant antigens, only guinea pigs receiving TmpB antigen demonstrated protection expressed by the development of significantly (P < 0.01) smaller, atypical lesions of significantly (P < 0.01) shorter duration and devoid of or containing fewer T. pallidum organisms than lesions in the remaining immunized and control animals.